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  • Inorganic Chemistry  (7,017)
  • Biochemistry and Biotechnology  (6,597)
  • 1995-1999  (5,192)
  • 1990-1994  (6,795)
  • 1950-1954  (1,627)
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  • 101
    Electronic Resource
    Electronic Resource
    Biomass growth monitoring using pressure drop in a cocurrent biofilter (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 97-104 
    Details
    ISSN: 0006-3592
    Keywords: fixed-bed bioreactor ; pressure drop ; biofilm growth monitoring ; Biofor ; friction factor ; Reynolds number ; wastewater treatment ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The possibility of following the biomass growth by pressure drop measurement was investigated in an aerated cocurrent upflow fixed-bed bioreactor continuously fed with wastewater containing industrial organic pollutants. The experiments were carried out in a biological filtration oxygenated reactor (Biofor) pilot plant packed with expanded clay balls (Biolite) of 2.7-mm diameter, which served as biomass carriers. The column was equipped for on-line pressure drop measurements. Correlation between pressure drop measurements and Reynolds numbers of air and water were determined in experiments carried out without biomass. Under operating conditions with biomass, it was demonstrated that column clogging and the operating time between washing cycles can be predicted depending on the volumetric organic load for a given total organic carbon inlet concentration. The biological activity of the fixed biomass was estimated from the oxygen consumption rate per unit time and carrier area. The oxygen consumption rate measurements demonstrated that the biological activity depends on the inlet substrate concentration, and that the Biofor column was most efficient between 75 and 100 g m-3 of total organic carbon inlet concentration. In the course of the wastewater treatment, using pressure drop measurements, the equivalent diameter of the Biolite particles, the reduced column macroporosity, and the biofilm thickness were calculated. An expression correlating biofilm density and biofilm thickness, as determined from the pressure drop measurements, was proposed. Good agreement was found between the fixed biomass in the reactor, determined as volatile suspended solids, and the biologically active biomass, estimated by respirometry. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 97-104, 1998.
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  • 102
    Electronic Resource
    Electronic Resource
    Resistance of biofilms to the catalase inhibitor 3-amino-1,2,4-triazole (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 135-135 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: No abstract.
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  • 103
    Electronic Resource
    Electronic Resource
    DNA protection from extracapsular nucleases, within chitosan- or poly-L-lysine-coated alginate beads (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 124-134 
    Details
    ISSN: 0006-3592
    Keywords: DNA ; encapsulation ; alginate ; nuclease ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: DNA was immobilized within alginate matrix using an external or an internal calcium source, and then membrane coated with chitosan or poly-L-lysine. Membrane thickness increased with decreasing polymer molecular weight and increasing degree of deacetylation (chitosan). Beads were exposed to a 31,000 molecular weight nuclease to determine the levels of DNA protection offered by different membrane and matrix combinations. Almost total hydrolysis of DNA was observed in alginate beads following nuclease exposure. Less than 1% of total double-stranded DNA remained unhydrolyzed within chitosan- or poly-L-lysine-coated beads, corresponding with an increase in DNA residuals (i.e. double- and single-stranded DNA, polynucleotides, bases). Chitosan membranes did not offer sufficient DNA protection from DNase diffusion since all of the double-stranded DNA was hydrolyzed after 40 min of exposure. Both chitosan and poly-L-lysine membranes reduced the permeability of alginate beads, shown by enhanced retention of DNA residuals after DNase exposure. The highest level of DNA protection within freshly prepared beads was obtained with high molecular weight (197,100) poly-L-lysine membranes coated on beads formed using an external calcium source, where over 80% of the double-stranded DNA remained after 40 min of DNase exposure. Lyophilization and rehydration of DNA beads also reduced permeability to nucleases, resulted in DS-DNA recoveries of 60% for chitosan-coated, 90% for poly-L-lysine-coated, and 95% for uncoated alginate beads. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 124-134, 1998.
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  • 104
    Electronic Resource
    Electronic Resource
    Direct fermentation of 2-keto-l-gulonic acid in recombinant Gluconobacter oxydans (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 309-315 
    Details
    ISSN: 0006-3592
    Keywords: l-ascorbic acid ; vitamin C ; 2-keto-l-gulonic acid ; l-sorbose dehydrogenase ; l-sorbosone dehydrogenase ; Gluconobacter ; chemical mutation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: We isolated Gluconobacter oxydans T-100 that had an activity to produce 2-KLGA from d-sorbitol; however, the yield of 2-KLGA was quite insufficient. Therefore, enzymes involved in the biosynthesis of l-sorbosone and 2-KLGA, l-sorbose dehydrogenase (SDH) and l-sorbosone dehydrogenase (SNDH), respectively, were purified from G. oxydans T-100. A genomic library of G. oxydans T-100 was screened to clone both genes for SDH and SNDH based on their amino acid sequences. SNDH and SDH were encoded in sequential open reading frames with 1497 and 1596 nucleotides, respectively, which were verified by the expression in Escherichia coli. The amino acid sequence of SDH and SNDH showed close similarity with E. coli choline dehydrogenase (CDH) and betaine-aldehyde dehydrogenase (BADH), respectively, which cooperatively play a key role for conferring osmotic tolerance. Because the yield of 2-KLGA by G. oxydans introduced with the genes for SDH and SNDH were insufficient, replacement of the promoter with that of Escherichia coli tufB1 in combination with chemical mutagenesis by N-methyl-N′-nitro-N-nitrosoguanidine resulted in improvement of the production level. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58:309-315, 1998.
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  • 105
    Electronic Resource
    Electronic Resource
    Modeling and measurements of fungal growth and morphology in submerged fermentations (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 216-229 
    Details
    ISSN: 0006-3592
    Keywords: model ; fungal fermentation ; morphology ; Aspergillus awamori ; agitation intensities ; dissolved oxygen tension ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Generalizing results from fungal fermentations is difficult due to their high sensitivity toward slight variation in starting conditions, poor reproducibility, and difference in strains. In this study a mathematical model is presented in which oxygen transfer, agitation intensity, dissolved oxygen tension, pellet size, formation of mycelia, the fraction of mycelia in the total biomass, carbohydrate source consumption, and biomass growth are taken into account. Two parameters were estimated from simulation, whereas all others are based on measurements or were taken from literature. Experimental data are obtained from the fermentations in both 2 L and 100 L fermentors at various conditions. Comparison of the simulation with experiments shows that the model can fairly well describe the time course of fungal growth (such as biomass and carbohydrate source concentrations) and fungal morphology (such as pellet size and the fraction of pellets in the total biomass). The model predicts that a stronger agitation intensity leads to a smaller pellet size and a lower fraction of pellets in the total biomass. At the same agitation intensity, pellet size is hardly affected by the dissolved oxygen tension, whereas the fraction of mycelia decreases slightly with an increase of the dissolved oxygen tension in the bulk. All of these are in line with observations at the corresponding conditions. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 216-229, 1998.
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  • 106
    Electronic Resource
    Electronic Resource
    Effect of Escherichia coli biomass composition on central metabolic fluxes predicted by a stoichiometric model (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 230-238 
    Details
    ISSN: 0006-3592
    Keywords: Escherichia coli ; metabolism ; flux ; linear optimization ; biomass composition ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The amino acid composition of proteins and the fatty acid composition of the cell membranes were measured in Escherichia coli growing exponentially in batch culture on glucose, succinate, glycerol, pyruvate, and acetate, and growing under continuous culture conditions on glucose at dilutions rates equivalent to the growth rates of the batch cultures. Although the fatty acid composition of the membranes did change significantly with carbon source and dilution rate, the amino acid content of proteins did not change significantly under either condition. A previously developed stoichiometric model of metabolism was used to calculate the fluxes through the metabolic reactions and to determine their sensitivity to changes in fatty acid and amino acid composition. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 230-238, 1998.
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  • 107
    Electronic Resource
    Electronic Resource
    Increased agitation intensity increases CD13 receptor surface content and mRNA levels, and alters the metabolism of HL60 cells cultured in stirred tank bioreactors (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 239-250 
    Details
    ISSN: 0006-3592
    Keywords: HL60 cells ; CD13 ; hydrodynamic effects ; mRNA ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Flow cytometry and Northern blotting were used to examine the effects of hydrodynamic forces in stirred tank bioreactors on CD13 receptor surface content and mRNA levels of HL60 (human promyelocytic leukemia) cells. A step increase in agitation rate from 80 to 300 or 400 rpm reduced the apparent HL60 growth rate in a dose-dependent manner. This step increase in agitation rate (to 300 or 400 rpm) also increased the CD13 receptor surface content on averge by 30% and 100%, respectively. This increase in CD13 receptor surface content was correlated with a 10% and a 60% increase in CD13 mRNA levels. We also observed a significant and very reproducible drop in CD13 expression over the course of a batch bioreactor run (80 rpm). Although we have no explanation for this, we show that the decrease in CD13 receptor surface content can be (at least partially, if not fully) explained by the corresponding decrease in CD13 mRNA. HL60 cell cultures agitated at 300 and 400 rpm exhibited glucose consumption and lactate production rates that were approximately 40% and 90% greater than values of the cultures agitated at 80 rpm. The physiological and practical implications of these results are discussed. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 239-250, 1998.
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  • 108
    Electronic Resource
    Electronic Resource
    Effects of methocel A15LV, polyethylene glycol, and polyvinyl alcohol on CD13 and CD33 receptor surface content and metabolism of HL60 cells cultured in stirred tank bioreactors (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 251-258 
    Details
    ISSN: 0006-3592
    Keywords: HL60 cells ; CD13 ; CD33 ; media additives ; hydrodynamic effects ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Flow cytometry was used to examine the effect of hydrodynamic forces in a stirred tank bioreactor on the CD13 and CD33 receptor surface content of HL60 (human promyelocytic leukemia) cells. A step increase in agitation rate from 80 to 400 rpm reduced the HL60 cell apparent growth rate and increased the CD13 receptor surface content per cell, on average, by 95%. In contrast, this step increase in agitation rate to 400 rpm decreased the CD33 receptor surface content per cell, on average, by 10%. The protective effects of 0.1% Methocel A15LV, polyethylene glycol (PEG), and polyvinyl alcohol (PVA) on CD13 and CD33 receptor surface content were examined under agitation at 300 rpm in parallel 2 L bioreactor runs. The average CD33 receptor surface content was unaffected by the presence of Methocel A15LV or PEG, while PVA had a slight protective effect. In contrast, in terms of CD13 receptor content, HL60 cells agitated at 300 rpm with Methocel A15LV, PEG, or PVA behaved like cells agitated at 80 rpm with no media additives (McDowell and Papoutsakis, 1998). That is, Methocel A15LV, PEG, and PVA prevented the transduction of mechanical forces which affect CD13 cell content. HL60 cells cultured with 0.1% A15LV, PEG or PVA under conditions of mild agitation (60 rpm) in spinner flasks exhibited glucose consumption and lactate production rates that were approximately 20% lower than values of cultures containing no additive. Under conditions of agitation at 300 rpm in the 2 L bioreactor, the presence of A15LV, PEG, and PVA reduced the HL60 glucose consumption and lactate production rates by approximately 50%. Thus, media additives can dramatically reduce lactate accumulation in agitated bioreactors due to cell growth, in addition to providing protection from cellular injury. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 251-258, 1998.
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  • 109
    Electronic Resource
    Electronic Resource
    Effect of post-induction nutrient feeding strategies on the production of bioadhesive protein in Escherichia coli (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 271-276 
    Details
    ISSN: 0006-3592
    Keywords: recombinant ; E. coli ; fed-batch ; protein production ; post-induction feeding ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effect of post-induction nutrient feeding strategies on the production of bioadhesive protein using an IPTG inducible expression system in Escherichia coli was investigated. Cells were cultured in an exponential fed-batch mode to the OD600 of ca. 100 (48 gDCW/L) prior to induction. Six different post-induction nutrient feeding strategies (pH-stat, exponential, constant and linear change in feeding rate with three different slopes) were then applied, and bioadhesive protein production was examined. It was found that post-induction cell growth was independent of nutrient feeding rate. However, bioadhesive protein production was significantly affected by post-induction feeding strategies. Linearly changing post-induction feeding rate with a suitable slope allowed production of bioadhesive protein up to 5.3 g/L, which was higher than that obtained by the other post-induction feeding strategies. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 271-276, 1998.
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  • 110
    Electronic Resource
    Electronic Resource
    Serum increases the CD13 receptor expression, reduces the transduction of fluid-mechanical forces, and alters the metabolism of HL60 cells cultured in agitated bioreactors (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 259-268 
    Details
    ISSN: 0006-3592
    Keywords: HL60 cells ; CD13 ; serum ; hydrodynamic effects ; mRNA ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effects of serum medium concentration on the CD13 receptor surface content and mRNA levels of HL60 (human promyelocytic leukemia) cells were examined using flow cytometry and Northern blotting. Increasing the serum concentration from 2.5% to 10% and from 5% to 10% increased the CD13 receptor surface content of HL60 cells by 100% and 25%, respectively, in spinner flasks agitated at 60 rpm. In bioreactors at 80 rpm, increasing the serum concentration from 2.5% to 10% and from 5% to 10% increased the CD13 receptor surface content by 60% and 35%, respectively. This increase in CD13 receptor surface content was correlated with a 30% and a 20% increase in CD13 mRNA levels. Increasing serum concentrations also increased the average HL60 cell size under non-damaging conditions (60 rpm in spinner flasks, 80 rpm in bioreactors). Under conditions of agitation at 300 rpm in 2 L bioreactors, increasing serum concentrations (2.5% vs. 10%, 5% vs. 10%) allowed for higher HL60 apparent growth rates, but decreased the CD13 receptor surface content and mRNA levels. In view of our earlier findings on the effects of agitation on the CD13 antigen, these data suggest that serum reduces the transduction of mechanical forces that affect CD13 expression. At 300 rpm, HL60 cells cultured in 10% serum exhibited glucose consumption and lactate production rates that were approximately 50% and 60% lower than the values of cells cultured in 5% and 2.5% serum, respectively. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 259-268, 1998.
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  • 111
    Electronic Resource
    Electronic Resource
    Double inhibition model for degradation of phenol by Pseudomonas putida Q5 (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 560-567 
    Details
    ISSN: 0006-3592
    Keywords: phenol degradation ; Pseudomonas putida ; inhibition model ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A semiempirical model, based on the presence of an inhibitory intermediate metabolite excreted to the broth, was developed to better predict the dynamic responses to shock loadings of Pseudomonas putida Q5 degrading phenol. Compared to the Haldane equation, the new model exhibited better prediction capabilities for a broad range of inlet concentration and dilution rate step changes. The experiments were performed at 10° and 25°C and ranged from stable responses to washouts. The time delays observed experimentally were successfully predicted with the dual-inhibition model and a very good agreement with the observed phenol profile also was found in a pulse experiment. A possible intermediate metabolite was detected by HPLC analyses based on the high correlation shown with the predicted inhibitory intermediate metabolite in the model. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 560-567, 1998.
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  • 112
    Electronic Resource
    Electronic Resource
    Preparation of a new thermo-responsive adsorbent with maltose as a ligand and its application to affinity precipitation (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 568-579 
    Details
    ISSN: 0006-3592
    Keywords: thermo-responsive polymer ; immobilized maltose ; affinity precipitation ; thermolabile enzyme ; concanavalin A ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A thermo-responsive polymer on which maltose was covalently immobilized as an affinity ligand was newly synthesized for purification of thermolabile proteins from the crude solution by affinity precipitation. Among the thermo-responsive polymers synthesized as carriers for adsorbent, poly(N-acryloylpiperidine)-cysteamine (pAP) has a lower critical solution temperature (LCST) of around 4°C, at which its solubility exhibits a sharp change. Adsorbent for affinity precipitation was prepared by combining pAP with maltose using trimethylamine-borane as a reducing reagent. This adsorbent (pAPM) obtained showed a good solubility response: pAPM in the basal buffer (pH 7.0) became soluble below 4°C and was completely insoluble above 8°C. The affinity precipitation method using pAPM consisted of the following four steps: adsorption at 4°C, precipitation of the complex at 10°C, desorption by adding the desorption reagent at 4°C, and recovery of a target protein at 10°C. In the affinity precipitation of Con A from the crude extract of jack bean meal, 82% of Con A added was recovered with 80% purity by addition of 0.2 M methyl-α-D-mannopyranoside as a desorption reagent. In the repeated purification of Con A from the crude extract, pAPM could be satisfactorily reused without decrease in the affinity performance. Moreover, when pAPM was used for the purification of thermolabile α-glucosidase from the cell-free extract of Saccharomyces cerevisiae, 68% of total activity added was recovered and the specific activity per amount of protein of the purified solution was enhanced 206-fold higher than that of the cell-free extract without thermal deactivation of the enzyme. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 568-579, 1998.
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  • 113
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    Use of soybean oil and ammonium sulfate additions to optimize secondary metabolite production (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 580-588 
    Details
    ISSN: 0006-3592
    Keywords: soybean oil ; ammonium sulfate ; secondary metabolite production ; streptomyces ; lipase ; homologs ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A valine-overproducing mutant (MA7040, Streptomyces hygroscopicus) was found to produce 1.5 to 2.0 g/L of the immunoregulant, L-683,590, at the 0.6 m3 fermentation scale in a simple batch process using soybean oil and ammonium sulfate-based GYG5 medium. Levels of both lower (L-683,795) and higher (HH1 and HH2) undesirable homolog levels were controlled adequately. This batch process was utilized to produce broth economically at the 19 m3 fermentation scale. Material of acceptable purity was obtained without the multiple pure crystallizations previously required for an earlier culture, MA6678, requiring valine supplementation for impurity control.Investigations at the 0.6 m3 fermentation scale were conducted, varying agitation, pH, initial soybean oil/ammonium sulfate charges, and initial aeration rate to further improve growth and productivity. Mid-cycle ammonia levels and lipase activity appeared to have an important role. Using mid-cycle soybean oil additions, a titer of 2.3 g/L of L-683,590 was obtained, while titers reached 2.7 g/L using mid-cycle soybean oil and ammonium sulfate additions. Both higher and lower homolog levels remained acceptable during this fed-batch process. Optimal timing of mid-cycle oil and ammonium sulfate additions was considered a critical factor to further titer improvements. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 580-588, 1998.
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  • 114
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    Chinese hamster ovary cells with constitutively expressed sialidase antisense RNA produce recombinant dnase in batch culture with increased sialic acid (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 589-595 
    Details
    ISSN: 0006-3592
    Keywords: CH0 cells ; sialidase activity ; recombinant DNase ; sialic acid ; antisense DNA ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Under some cell culture conditions, recombinant glycoprotein therapeutics expressed in Chinese hamster ovary (CHO) cells lose sialic acid during the course of the culture (Sliwkowski et al., 1992; Munzert et al., 1996). A soluble sialidase of CHO cell origin degrades the expressed recombinant protein and has been shown to be released into the culture fluid as the viability of the cells decreases. To reduce the levels of the sialidase and to prevent desialylation of recombinant protein, a CHO cell line has been developed that constitutively expresses sialidase antisense RNA. Several antisense expression vectors were prepared using different regions of the sialidase gene. Co-transfection of the antisense constructs with a vector conferring puromycin resistance gave rise to over 40 puromycin resistant clones that were screened for sialidase activity. A 5′ 474 bp coding segment of the sialidase cDNA, in the inverted orientation in an SV 40-based expression vector, gave maximal reduction of the sialidase activity to about 40% wild-type values. To test if this level of sialidase would lead to increased sialic acid content of an expressed recombinant protein, the 474 antisense clone was employed as a host for expression of human DNase as a model glycoprotein. The sialic acid content of the DNase produced in the antisense cultures was compared with material made in the wild-type parental cell line. About 20-37% increase in sialic acid content, or 0.6-1.1 mole of additional sialic acid out of a total of 3.0 mole on the product, was found on the DNase made in the antisense cell lines. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 589-595, 1998.
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  • 115
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    Site-directed and random immobilization of subtilisin on functionalized membranes: Activity determination in aqueous and organic media (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 608-616 
    Details
    ISSN: 0006-3592
    Keywords: site-directed mutagenesis ; oriented immobilization ; subtilisin ; membrane ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Kinetic comparisons have been made between a randomly immobilized and a site-specifically immobilized subtilisin BPN′ on microfiltration membranes of varying hydrophilicities in both aqueous and organic media. Site-directed mutagenesis was employed to introduce a single cysteine into the amino acid sequence of subtilisin at a location away from the active site. Immobilization of this mutant enzyme was then carried out using the single cysteine residue to orient the active site of the enzyme away from the membrane surface. Kinetic comparison of the immobilized mutant enzyme with the randomly immobilized wild-type enzyme in aqueous media showed an activity enhancement on both hydrophilic silica-containing and hydrophobic poly(ether)sulfone membranes. Higher loading efficiencies were observed for the site-directed enzyme on immobilization. Optimal enzyme loading values were calculated for the randomly immobilized enzyme. An enhancement of activity was also observed for the site-directed immobilized systems using nearly anhydrous hexane as the solvent. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 608-616, 1998.
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  • 116
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    Monitoring recombinant human interferon-gamma N-glycosylation during perfused fluidized-bed and stirred-tank batch culture of CHO cells (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 596-607 
    Details
    ISSN: 0006-3592
    Keywords: micellar electrokinetic capillary chromatography ; capillary isoelectric focusing ; Chinese hamster ovary ; interferon-gamma ; perfusion culture ; glycosylation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Chinese hamster ovary cells producing recombinant human interferon-γ were cultivated for 500 h attached to macroporous microcarriers in a perfused, fluidized-bed bioreactor, reaching a maximum cell density in excess of 3 × 107 cells (mL microcarrier)-1 at a specific growth rate (μ) of 0.010 h-1. During establishment of the culture, the N-glycosylation of secreted recombinant IFN-γ was monitored by capillary electrophoresis of intact IFN-γ proteins and by HPLC analysis of released N-glycans. Rapid analysis of IFN-γ by micellar electrokinetic capillary chromatography resolved the three glycosylation site occupancy variants of recombinant IFN-γ (two Asn sites occupied, one Asn site occupied and nonglycosylated) in under 10 min per sample; the relative proportions of these variants remained constant during culture. Analysis of IFN-γ by capillary isoelectric focusing resolved at least 11 differently sialylated glycoforms over a pI range of 3.4 to 6.4, enabling rapid quantitation of this important source of microheterogeneity. During perfusion culture the relative proportion of acidic IFN-γ proteins increased after 210 h of culture, indicative of an increase in N-glycan sialylation. This was confirmed by cation-exchange HPLC analysis of released, fluorophore-labeled N-glycans, which showed an increase in the proportion of tri- and tetrasialylated N-glycans associated with IFN-γ during culture, with a concomitant decrease in the proportion of monosialylated and neutral N-glycans. Comparative analyses of IFN-γ produced by CHO cells in stirred-tank culture showed that N-glycan sialylation was stable until late in culture, when a decline in sialylation coincided with the onset of cell death and lysis. This study demonstrates that different modes of capillary electrophoresis can be employed to rapidly and quantitatively monitor the main sources of glycoprotein variation, and that the culture system and operation may influence the glycosylation of a recombinant glycoprotein. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 596-607, 1998.
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  • 117
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    Kinetic, dynamic, and pathway studies of glycerol metabolism by Klebsiella pneumoniae in anaerobic continuous culture: IV. Enzymes and fluxes of pyruvate metabolism (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 617-626 
    Details
    ISSN: 0006-3592
    Keywords: Klebsiella pneumoniae ; glycerol ; pyruvate kinase ; pyruvate:formate-lyase ; pyruvate dehydrogenase ; in vitro and in vivo activities ; dynamics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The activities of pyruvate kinase (PK), pyruvate: formate-lyase (PFL), pyruvate dehydrogenase (PDH), and citrate synthase (CS) involved in the anaerobic glycerol conversion by Klebsiella pneumoniae were studied in continuous culture under conditions of steady states and sustained oscillations. Both the in vitro and in vivo activities of PK, PFL, and PDH are strongly affected by the substrate concentration and its uptake rate, as is the in vitro activity of CS. The flux from phosphoenolpyruvate to pyruvate is found to be mainly regulated on a genetic level by the synthesis rate of PK, particularly at low substrate concentration and low growth rate. In contrast, the conversion of pyruvate to acetyl-CoA is mainly regulated on a metabolic level by the in vivo activities of PFL and PDH. The ratio of in vitro to in vivo activities is in the range of 1 to 1.5 for PK, 5 to 17 for PFL and 5 to 80 for PDH under the experimental conditions. The regulation of in vivo activity and synthesis of these enzymes is sensitive to fluctuations of culture conditions, leading to oscillations of both the in vitro and in vivo activities. In particular, PFL is strongly affected during oscillations; its average in vitro activity is only about half of its corresponding steady-state value under similar environmental conditions. The average in vitro activities of PDH and PK under oscillations are close to their corresponding steady-state values. In contrast to all other enzymes measured for the glycerol metabolism by K. pneumoniae PFL and PDH are more effectively in vivo utilized under oscillations than under steady state, underlining the peculiar role of pyruvate metabolism in the dynamic responses of the culture. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 617-626, 1998.
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    Dynamic modeling of meta- and para-nitrobenzoate metabolism by a mixed co-immobilized culture of Comamonas spp. JS46 and JS47 (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 507-516 
    Details
    ISSN: 0006-3592
    Keywords: bioremediation ; Comamonas ; nitrobenzoates ; reactor modeling ; mixed culture ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A model describing the transient activity of a mixed immobilized culture of Comamonas spp. JS46 and JS47 growing on mixed substrates is presented. The transient periods considered are those following changes in the feed carbon source, which alternated between meta- and para-nitrobenzoate. The feed profile alternately starved one of the species in the mixed culture. The response of the system, as quantified by the reactor effluent substrate concentrations, is dictated by the activity of the biomass and the appropriate biochemical pathway. As detailed mechanistic pathway information is not available, respirometry has been used to characterize both facets of activity. Two parameters were introduced: Ψ representing pathway activity and Γ representing biomass activity; a detailed description of the analysis is included. The model is compared to experimental investigation of the system and describes the reactor response well. The agreement between model and experiment suggests the usefulness of oxygen kinetics as global measurements to describe complex systems when mechanistic detail is not available. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59: 507-516, 1998.
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    Flotation characteristics of cyanobacterium Anabaena flos-aquae for gas vesicle production (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 636-641 
    Details
    ISSN: 0006-3592
    Keywords: flotation ; cyanobacterium (blue-green algae) ; gas vesicle ; buoyancy ; filament density ; photobioreactor ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Cyanobacterium Anabaena flos-aquae was cultivated in photobioreactors for production of intracellular gas vesicles (GVs), as potential oxygen microcarriers. Natural flotation of the buoyant culture was investigated as a potential means of cell harvesting, because filtration and centrifugation tended to destroy the vesicles. Best flotation was found with actively growing culture and when conducted in the dark. The flotation-related cell properties, including the specific GV content, vesicle-collapsed filament density, and intracellular carbohydrate content, were measured to understand the phenomena. During the batch culture, the specific GV content remained relatively constant at 370 μL/(g dry cells) but the filament density (ranging 1.02 to 1.08 g/cm3) showed a decrease-then-increase profile. The increase began when the growth slowed down because of the reduced light availability at high cell concentrations. The dark flotation was studied with both actively growing (μ ≈ 0.2 day-1) and stationary-phase cultures. The specific GV content of the stationary-phase culture remained relatively constant while that of the growing culture increased slightly. The intracellular carbohydrate content of the growing culture decreased much faster and more significantly, from 57 to 10 mg/(g dry cells) in ≤ 8 h. The filament density also decreased, apparently parallel to the profiles of carbohydrate content. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 636-641, 1998.
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    Expanded and packed bed albumin adsorption on fluoride modified zirconia (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 333-340 
    Details
    ISSN: 0006-3592
    Keywords: fluoride-modified zirconia ; expanded bed ; packed bed ; protein adsorption ; adsorption-desorption kinetics ; intraparticle diffusion ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The expanded bed characteristics of 75-103μm fluoride-modified zirconia (FmZr) particles synthesized by a fed batch oil emulsion process were investigated. These particles are distinguished from commercially available expanded-bed adsorbents by virtue of their high density (2.8 g/cc) and the mixed mode protein retention mechanism which allows for the retention of both cationic and anionic proteins. The linear velocity versus bed porosity data agree with the Richardson-Zaki relationship with the terminal velocity in infinite medium of 2858.4 cm/h and a bed expansion index of 5.1. Residence time distribution (RTD) studies and bovine serum albumin (BSA) adsorption studies were performed as a function of the height of the settled bed to the column diameter (H:D) ratio and degree of bed expansion with superficial velocities of 440 to 870 cm/h. The settled bed, a 2× expanded bed, and a 3× expanded bed were studied for the H:D ratios of 1:1, 2:1, and 3:1. The dynamic binding capacity (DBC) at 5% breakthrough was low (2-8 mg BSA/mL settled bed) and was independent of the H:D ratio or the degree of bed expansion. The saturation DBC was 32.3 ± 7.0 mg BSA/mL settled bed. The adsorption-desorption kinetics and intraparticle diffusion for protein adsorption on FmZr (38-75 μm) were investigated by studying the packed bed RTD and BSA adsorption as a function of temperature and flow rate. The data show that the adsorption-desorption kinetics along with intraparticle diffusion significantly influence protein adsorption on FmZr. Low residence times (∼0.8 min) of BSA result in a DBC at 5% breakthrough which is 3.5-fold lower compared to that at 6-fold higher protein residence time. At low linear velocity (45 cm/h) the breakthrough curve is nearly symmetrical and becomes asymmetrical and more dispersed at higher linear velocity (270 cm/h) due to the influence of slow adsorption-desorption kinetics and intraparticle diffusion.© 1998 John Wiley & Sons, Inc. Bioeng 60: 333-340, 1998.
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    Optimized enzymatic synthesis of methyl benzoate in organic medium. Operating conditions and impact of different factors on kinetics (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 356-361 
    Details
    ISSN: 0006-3592
    Keywords: enzymatic synthesis ; methyl benzoate ; methanol inhibition ; solvent effects ; enzyme hydration ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Enzyme-catalyzed synthesis of methyl benzoate is reported. It is the first example of direct esterification of benzoic acid which provides good yields. The reaction was performed in a heterogeneous medium by Candida rugosa lipase powder suspended in a hexane/toluene mixture. The impact of some factors was examined. Benzoic acid does not inhibit the lipase until 100 mM. Above 90 mM, methanol inhibits the enzyme. This inhibition is partially eliminated by increasing benzoic acid concentration. Below 90 mM, methanol mainly interacts with the water adsorbed on the biocatalyst. A minimum water content is necessary to activate the biocatalyst. Water must be provided proportionally to the lipase content. Toluene, necessary for benzoic acid solubilization, also acts negatively on reaction kinetics. This is attributed to a modification of benzoic acid partition between the biocatalytic and the organic phases. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 356-361, 1998.
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    Stirred culture of peripheral and cord blood hematopoietic cells offers advantages over traditional static systems for clinically relevant applications (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 534-543 
    Details
    ISSN: 0006-3592
    Keywords: stirred-culture ; hematopoietic cell culture ; serum-free medium ; peripheral blood ; umbilical cord blood ; CD34+ cells ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The ability to culture hematopoietic cells in readily characterizable and scalable stirred systems, combined with the capability to utilize serum-free medium, will aid the development of clinically attractive bioreactor systems for transplantation therapies. We thus examined the proliferation and differentiation characteristics of peripheral blood (PB) mononuclear cells (MNC), cord blood (CB) MNC, and PB CD34+ cells in spinner flasks and (control) T-flask cultures in both serum-containing and serum-free media. Hematopoietic cultures initiated from all sources examined (PB MNC, CB MNC, and PB CD34+ cells) grew well in spinner vessels with either serum-containing or serum-free medium. Culture proliferation in spinner flasks was dependent on both agitator design and RPM as well as on the establishment of critical inoculum densities (ID) in both serum-containing (2 × 105 MNC/mL) and serum-free (3 × 105 MNC/mL) media. Spinner flask culture of PB MNC in serum-containing medium provided superior expansion of total cells and colony-forming cells (CFC) at high ID (1.2 × 106 cells/mL) as compared to T-flask controls. Serum-free spinner culture was comparable, if not superior, to that observed in serum-containing medium. This is the first report of stirred culture of PB or CB MNC, as well as the first report of stirred CD34+ cell culture. Additionally, this is the first account of serum-free stirred culture of hematopoietic cells from any source. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59: 534-543, 1998.
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    Kinetic, dynamic, and pathway studies of glycerol metabolism by Klebsiella pneumoniae in anaerobic continuous culture: III. Enzymes and fluxes of glycerol dissimilation and 1,3-propanediol formation (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 544-552 
    Details
    ISSN: 0006-3592
    Keywords: Klebsiella pneumoniae ; glycerol dissimilation ; 1,3-propanediol ; in vitro and in vivo enzyme activities ; dynamics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The initial steps of glycerol dissimilation and 1,3-propanediol (1,3-PD) formation by Klebsiella pneumoniae anaerobically grown on glycerol were studied by quantifying the in vitro and in vivo activities of enzymes in continuous culture under conditions of steady state and oscillation and during transient phases. The enzymes studied included glycerol dehydrogenase (GDH), glycerol dehydratase (GDHt), and 1,3-propanediol oxidoreductase (PDOR). Three conclusions can be drawn from the steady-state results. First, glycerol concentration in the culture is a key parameter that inversely affects the in vitro activities (concentrations) of all three enzymes, but has a positive effect on their in vivo activities. Growth rate significantly affects the ratio of in vitro and in vivo enzyme activities under low glycerol concentrations, but not under glycerol excess. Second, whereas the flux through the oxidative pathway of glycerol dissimilation is governed mainly by the regulation of in vivo enzyme activity on a metabolic level, the flux through the reductive pathway is largely controlled by the synthesis of enzymes. Third, GDHt is a major rate-liming enzyme for the consumption of glycerol and the formation of 1,3-PD in K. pneumoniae at high glycerol concentrations. Results from oscillating cultures revealed that both in vitro and in vivo activities of the enzymes oscillated. The average values of the in vitro activities during an oscillation cycle agreed well with their corresponding values for nonoscillating cultures under similar environmental conditions. Experiments with step changes in the feed concentration of glycerol demonstrated that growth and product formation are very sensitive to changes of substrate concentration in the culture. This sensitivity is due to the dynamic responses of the genetic and metabolic networks. They should be considered when modeling the dynamics of the culture and attempting to improve the formation of 1,3-PD. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59: 544-552, 1998.
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    Expulsion of proteins from water-in-oil microemulsions by treatment with cosurfactant (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 557-566 
    Details
    ISSN: 0006-3592
    Keywords: microconclusions ; liquid-liquid extraction of proteins ; bioseparations ; reverse micelles ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A quick and simple method has been developed for the recovery of proteins from water-in-oil microemulsions (w/o-MEs), which is needed to further the use of liquid-liquid extraction in bioseparations. By adding a small portion (0.1 v/v or less) of cosurfactant (e.g., 1-alkanol) to w/o-ME solution, proteins were readily expelled, sometimes as solids, while most or all of the surfactant (Aerosol OT) remained in solution. The release of proteins increased with the further addition of cosurfactant and was greater when the molar ratio of protein to w/o-ME or fractional occupancy (f) was high. However, protein expulsion was also significant when f was small. The addition of cosurfactant released ribonuclease, lysozyme, α-chymotrypsin, pepsin, bovine serum albumin (BSA), and catalase from w/o-ME solution, but the expulsion was greater for BSA relative to chymotrypsin and lysozyme. Protein expulsion also increased with cosurfactant chain length for the homologous series of 1-alkanols starting at 1-butanol; however, water was also coexpelled in significant amounts. An exception to the latter rule was 1-butanol, which readily promoted the release of protein, but not encapsulated water. The addition of 1-butanol to a w/o-ME solution containing α-chymotrypsin and BSA selectively released the former protein, with chymotryptic activity occurring in the recovered protein. Possible mechanisms for the cosurfactant-mediated release of protein are discussed. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59: 557-566, 1998.
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    Hydrophobilization of an esterase by genetic combination with polyproline at the carboxyl terminal (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 582-586 
    Details
    ISSN: 0006-3592
    Keywords: esterase ; genetic recombination ; hydrophobilization ; polyproline ; transesterification reaction ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Polyproline, which is an amphiphilic polypeptide, was incorporated into the carboxyl terminal of an esterase by the recombinant DNA technique. The hydrophobicity of the esterase increased with increasing chain length of polyproline without inducing significant conformational changes. The mutant esterase catalyzed the hydrolysis of long-chain carboxylic acid ester more efficiently than the native esterase. It is considered that the alteration of substrate specificity is due to enhanced access of the mutant esterases to hydrophobic substrates. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59:582-586, 1998.
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    Capture of human monoclonal antibodies from cell culture supernatant by ion exchange media exhibiting high charge density (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 689-698 
    Details
    ISSN: 0006-3592
    Keywords: purification ; cation exchange chromatography ; cell culture ; cell culture medium ; serum free ; therapeutic antibodies ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A shortcut purification sequence for therapeutic proteins should consist of three steps: capture, purification, and polishing. Special emphasis has been put on direct capture of human monoclonal antibodies from culture supernatants with ion-exchangers avoiding pretreatment steps such as desalting, dilution, and other means to reduce the ionic strength. CM-HyperD, a cation-exchanger composed of an inorganic macroporous support filled with a viscoelastic gel with a high charge density was used. Capture of monoclonal antibodies from clarified hybridoma cell culture grown in media supplemented with fetal calf serum was investigated. Screening of different pH conditions and buffers for the load step showed that monoclonal antibodies were efficiently bound by CM-HyperD at pH 4.0 and 5.0 at an ionic strength equivalent to culture supernatant. Combination of negative purification with Q-Sepharose FF and capturing with CM-HyperD gave sufficient yield and resolution. Implementation of wash steps with higher conductivity did not improve the purity, but decreased the yield. Interestingly, high flow rates improved the purity. When antibodies were captured from serumfree culture supernatant the antibody could be eluted in a single peak with substantial reduction of contaminants. Capturing of antibodies by ion-exchange sorbents from culture supernatant is possible despite the high salt content. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 689-698, 1998.
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    7Li and 23Na NMR studies of transmembrane cation transport mediated by ionophore lasalocid A (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 15-20 
    Details
    ISSN: 1075-2617
    Keywords: ion transport ; kinetics ; lithium ; NMR ; shift reagent ; vesicles ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ion transport across phospholipid vesicles was studied by 7Li and 23Na-NMR using an aqueous anionic paramagnetic shift reagent, dysprosium nitrilotriacetate [Dy(NTA)2]3-, mediated by ionophores, lasalocid A and A23187. The intra- and extracellular 7Li and 23Na-NMR signals were well separated (20 Hz) at mM concentration of the shift reagent. The observed data on the rate constant for lithium transport across DPPC vesicles at various concentrations of the ionophores indicated that lasalocid A is a more efficient carrier for lithium ion compared with the sodium ion transport by this ionophore, while A23187 was not specific to either of the ions (Li or Na). ©1998 European Peptide Society and John Wiley & Sons, Ltd.
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    Conformational behaviour of Cα,α-diphenylglycine: folded vs. extended structures in DφG-containing tripeptides (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 21-32 
    Details
    ISSN: 1075-2617
    Keywords: Cα,α-disubstituted amino acids ; crystal structure ; molecular dynamics ; conformation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The crystal structures of three fully protected tripeptides containing the Dφg residue (Cα,α-diphenylglycine) in the central position are reported, namely Z-Gly-Dφg-Gly-OMe (a), Z-Gly-Dφg-Aib-OMe (b) and Z-Aib-Dφg-Aib-OMe (c). The molecular conformations are quite unusual because the Dφg residue adopts a folded conformation in the 310-helical region when the following residue adopts a folded conformation of opposite handedness (peptidesbandc). In contrast, the Dφg residue adopts the more frequently observed fully extended conformation when the following residue adopts a semi-extended conformation (peptidea). These findings are in agreement with the theoretical calculations on Ac-Dφg-Aib-NHCH3 and Ac-Aib-Dφg-NHCH3 also reported in this work. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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    Peptides from bovine brain: structure and biological role (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 211-225 
    Details
    ISSN: 1075-2617
    Keywords: endogenous peptides ; proteolytic degradation ; functional protein ; biologically active peptides ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Fractionation of bovine brain extracts followed by automatic Edman sequencing of individual components resulted in identification of 107 endogenous peptides formed from functional proteins (haemoglobin, myelin basic protein, cytochromecoxidase, etc) or unknown precursors. Several of the newly identified brain peptides demonstrate different types of biological activity; some of the substances show considerable overlap with the known biologically active peptides. It is suggested that these peptides should participate in regulation of extracellular and intracellular biochemical processes. A concept of ‘tissue-specific peptide pool’ is formulated describing a novel system of peptidergic regulation, complementary to the conventional hormonal and neuromodulatory systems. According to that description functional proteins provide their proteolytically derived fragments for maintaining the tissue homeostasis by modulating the availability of peptide receptors to respective ‘true’ ligands. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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    The crystal state conformation of Aib-rich segments of peptaibol antibiotics (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 502-510 
    Details
    ISSN: 1075-2617
    Keywords: X-ray crystal structure ; gliodeliquescin ; alamethicin ; hypelcin ; paracelsin ; Ac, acetyl ; pBrBz, para-bromobenzoyl ; Me, methyl ; Piv, pivaloyl ; Z, benzyloxycarbonyl ; tBu, tert butyl ; TFA, trifluoroacetic acid ; EDCI, N-ethyl-N′-(3-dimethyl-aminopropyl)-carbodiimide HOBt, 1-hydroxybenzotriazole ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ac-(Aib-Ala)3-OH (a protected segment of the peptaibols gliodeliquescin and paracelsin), Z-Leu-Aib-Val-Aib-Gly-OtBu (a segment of [Leu]7-gliodeliquescin), Z-Val-Aib-Aib-Gln-OtBu (a common segment of alamethicin, paracelsin, and hypelcin), and Ac-Aib-Pro-(Aib-Ala)2-OMe and Z-Aib-Pro-(Aib-Ala)2-OMe, which represent differently Nα-protected 1-6 segments of alamethicin and hypelcin, have been synthesized by solution methods. The crystal-state conformations of these five Aib-containing peptides have been determined by X-ray diffraction analysis. We have confirmed that the 310-helical structure is preferentially adopted by Aib-rich short peptides. An experimentally unambiguous proof for the 310→α-helix conversion has been provided by the two differently N-blocked -Aib-Pro-(Aib-Ala)2-OMe hexapeptides. The β-bend ribbon conformation, commonly observed in the (Aib-Pro)n sequential oligopeptides, is not found in the -Aib-Pro-Aib-Ala-Aib-Ala- sequence. As expected on the basis of the l-configuration of the Cα-monoalkylated residues, a right-handed helix screw sense was found in all peptides investigated. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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    X-ray structures of new dipeptide taste ligands (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 229-238 
    Details
    ISSN: 1075-2617
    Keywords: Conformational analysis ; peptide-based taste ligands ; artificial sweeteners ; X-ray crystal structures ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The molecular basis of sweet taste was investigated by carrying out the crystal state conformational analysis by X-ray diffraction of the following dipeptide taste igands:N-3,3-dimethylbutyl-aspartyl-phenylalanine methyl ester,I(N-DMB-Asp-Phe-OMe), its sodium salt (N-DMB-Asp-Phe-ONa),II, aspartyl-D-2-aminobutyric acid-(S)-α-ethylbenzylamide,III(Asp-D-Abu-(S)-α-ethylbenzylamide), aspartyl-N′-((2,2,5,5-tetramethylcyclopentanyl)-carbonyl)-(R)-1,1-diamino-ethane,IV(Asp-(R)-gAla-TMCP), and aspartyl-D-valine-(R)-α-methoxymethylbenzyl amide,V(Asp-D-Val-(R)-α-methoxymethylbenzylamide). With the exception of the sodium saltII, all compounds are sweet-tasting, showing in some cases considerable potency enhancement with respect to sucrose. The results of this study confirm the earlier model that an ‘L-shape’ molecular array is essential for eliciting sweet taste for dipeptide-like ligands. In addition, it was established that (i) substitution of the N-terminal group does not inhibit sweet taste, if its zwitterionic character is maintained; (ii) a hydrophobic group located between the stem and the base of the L-shape could be responsible for sweetness potency enhancement, as found inI, IIIandIV; in fact, the extraordinary potency of the N-alkylated analogueIwould support a model with an additional hydrophobic binding domain above the base of the ‘L’; (iii) removal of the methyl ester at the C-terminus of compoundIwith the salt formation gives rise to the tasteless compoundII; (iv) for the first time all possible side-chain conformers (g-,g+andt) for the N-substituted aspartyl residue were observed; and (v) a retro-inverso modification, incorporated at position 2 of the dipeptide chain, confers greater flexibility to the molecule, as demonstrated by the contemporary presence of six conformationally distinct independent molecules in the unit cell and yet sweet taste properties are maintained, as found inIV. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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    Energy minimization studies on α-turns (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 239-252 
    Details
    ISSN: 1075-2617
    Keywords: Hydrogen-bonded-tetrapeptide ; α-turns ; α-turn conformation ; energy minimization ; secondary structure ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Using a grid search technique, the entire conformational space of a system of four linked peptide units (tetrapeptide) was scanned to pick out geometrically possible 5→1 type hydrogen-bonded conformations defined as an α-turn. The energy minimization of these conformations led to 23 distinct minimum energy conformations (MECs) falling in 13 different classes. The presence of β and γ turn type hydrogen bonds along with 5→1 type hydrogen bond gave conformational variability in a given class. The occurrence of bifurcated hydrogen bonding network was a characteristic feature of most of the MECs. In many prototype MECs non-glycyl residues such as Ala and Pro could be accommodated. Comparison of MECs with the α-turn examples that are observed in proteins showed that the conformationally worked out MECs occurred in isolation in proteins, with the α-helical α-turn being distinctly the most predominant. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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    Conformational sampling of bioactive conformers: a low-temperature NMR study of 15N-Leu-enkephalin (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 253-265 
    Details
    ISSN: 1075-2617
    Keywords: Opioids ; enkephalin ; selectivity ; conformation ; NMR ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conformational studies of enkephalins are hampered by their high flexibility which leads to mixtures of quasi-isoenergetic conformers in solution and makes NOEs very difficult to detect in NMR spectra. In order to improve the quality of the NMR data, Leu-enkephalin was synthesized with 15N-labelled uniformly on all amide nitrogens and examined in a viscous solvent medium at low temperature. HMQC NOESY spectra of the labelled Leu-enkephalin in a DMSOd6/H2O mixture at 275 K do show numerous NOEs, but these are not consistent with a single conformer and are only sufficient to describe the conformational state as a mixture of several conformers. Here a different approach to the structure-activity relationships of enkephalins is presented: it is possible to analyse the NMR data in terms of limiting canonical structures (i.e. β- and γ-turns) and finally to select only those consistent with the requirements of δ selective agonists and antagonists. This strategy results in the prediction of a family of conformers that may be useful in the design of new δ selective opioid peptides. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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    Solid-phase synthesis of peptide nucleic acid (PNA) monomers and their oligomerization using disulphide anchoring linkers (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 266-281 
    Details
    ISSN: 1075-2617
    Keywords: Peptide nucleic acid monomers ; PNA synthesis ; disulphide linkers ; solid-phase synthesis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new simple solid-phase method has been developed for synthesizing Boc-protected peptide nucleic acid (PNA) monomers. An immobilized backbone 3 was built on Expansin® resin using an ester disulphide handle: 2-hydroxypropyl-dithio-2′-isobutyric acid (HPDI). The base acetic acids of thymine 5, Z-cytosine 9, Z-adenine 12, and 6-O-benzyl guanine 17 were prepared and coupled to the immoblized backbone. The HPDI handle was cleaved under mild conditions by cyanolysis or assisted hydrolysis with tris(2-carboxyethyl)phosphine (TCEP) to give undamaged PNA monomers. These monomers were coupled to form oligomers by solid-phase method with another disulphide linkage: aminoethyldithio-2-isobutyric acid (AEDI) grafted on an amino-functionalized TentaGel® resin, using in situ neutralization and TBTU as activating reagent. Final cleavage of the AEDI linker gave PNA bearing a cysteamide residue that could be useful for optimizing PNA properties. Oligomers of up to 16 residues long were assembled. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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    A new hybrid resin for stepwise screening of peptide libraries combined with single bead Edman sequencing (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 282-288 
    Details
    ISSN: 1075-2617
    Keywords: Synthetic peptide library ; one-bead-one-compound ; partial cleavage ; soluble phase screening ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A library system was developed for the discovery of bioactive peptides. Library synthesis and peptide sequencing was performed on a solid support while the screening for bioactivity was done with peptides in solution. The peptides were synthesized by split and mix, one-bead-one-peptide library synthesis, using a Tentagel S-NH2 solid support with a loading of approximately 100 pmol/bead. The major part of the peptide was connected to the support by a single acid-labile linker and a minor part of the peptide was acid-stabile attached to the polymer. The percentage of acid-stabile attached peptides could easily be controlled during modification of the amino functionalities of the resin at the start of the process. The cleavage rate of the acid-labile attached peptide from the resin depends on the composition of the cleavage mixture. When cleavage conditions were carefully controlled, a three-step partial cleavage protocol allowed for convergent bioactivity screening on peptide libraries using only one type of acid-labile linker. The partial cleavage and convergent screening procedure was repeated three times, after which the bead containing the bioactive peptide was sequenced. As such a bead still contained acid-stabile attached peptide, the Edman sequencing was straightforward and repetitive yields were excellent because the immobilized peptide was not washed out. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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    α-Hydroxymethylserine as a peptide building block: synthetic and structural aspects (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 46-57 
    Details
    ISSN: 1075-2617
    Keywords: α-hydroxymethylserine peptides ; isopropylidene protecting group ; crystal structure ; peptide conformation ; peptide synthesis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A synthetic methodology has been developed for peptide bond formation with α-hydroxmethylserine as the carboxyl or amino component and also for the preparation of homo-sequences. The key intermediate, O,O-protected α-hydroxymethylserine in the form of an isopropylidene derivative, is easily accessible and represents the first example of a heterocyclic Cα,α-disubstituted amino acid containing an 1,3-dioxane ring. The use of this intermediate facilitates protection of the sterically hindered amino and carboxyl groups and is advantageous for the coupling and deprotection steps. X-ray structure determination of Z-HmS(Ipr)-Ala-OMe revealed that the two crystallographically independent molecules present in the asymmetric unit adopt an S-shaped conformation. In the one molecule the achiral HmS(Ipr) residue has the torsion angle values (φ==61.4°,ψ=40.8°) in the left-handed helical region of the Ramachandran map, while in the second molecule the negative torsion angles (φ=-60.1°, ψ=-44.4°) are associated with the right-handed helix. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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    Synthesis and structural characterization of human-identical lung surfactant SP-C protein (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 355-363 
    Details
    ISSN: 1075-2617
    Keywords: lung surfactant ; human-identical SP-C protein ; solid phase synthesis ; palmitoylation ; structural characterization ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An efficient synthesis for human-identical lung surfactant protein SP-C is described with a semi-automated solid phase synthesizer using Fmoc chemistry. Double coupling and acetic anhydride capping procedures were employed for synthetic cycles within the highly hydrophobic C-terminal domain of SP-C. Isolation of the protein was performed by mild cleavage and deprotection conditions and subsequent HPLC purification yielding a highly homogeneous protein as established by sequence determination, electrospray, plasma desorption and MALDI mass spectrometry. A general method has been employed for the preparation of Cys-palmitoylated protein by using temporary Cys(tButhio) protection, in situ deprotection with β-mercaptoethanol and selective palmitoylation of resin-bound SP-C. The mild synthesis and isolation conditions provide SP-C with a high α-helical content, comparable to that of the natural SP-C, as assessed by CD spectra. Furthermore, first biophysical data indicate a surfactant activity comparable to that of the natural protein. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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    Large-scale production of peptides using the solid phase continuous flow method. Part 2cf. J. Peptide Sci. 3, 224-230 (1997) for part 1.: preparative synthesis of a 26-mer peptide thrombin inhibitor (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 327-334 
    Details
    ISSN: 1075-2617
    Keywords: large-scale peptide synthesis ; continuous flow ; macrosorb ; hindered sequence ; thrombin inhibitor ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A preparative method for the preparation of large peptides is described. An advantageous theoretical weight of peptide/weight of starting resin ratio (tPw/Rw) of about 0.3 was successfully experimented. The esterification of the first amino acid was realized with a racemization of less than 1%. The study of the coupling conditions led to the use of a diluted acylating mixture that allowed a 56% consumption of the amino acid derivatives (percentage use of amino acids) introduced in the synthesis. The cost analysis of the synthesis showed that the recovery of the amino acid derivatives was not worthwhile. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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    Trans-cis amide bond isomerization in fulleroprolines (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 364-368 
    Details
    ISSN: 1075-2617
    Keywords: trans-cis amide equilibrium ; dynamic nuclear magnetic resonance ; fulleroproline ; NOE differential spectroscopy ; proline ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 1H NMR study of fulleroproline derivative Ac-Fpr-OtBu and its Pro analogue Ac-l-Pro-OtBu over a range of temperatures in toluene-d8 solution has enabled the comparison of their equilibrium and activation parameters for the trans/cis interconversion around the amide partial double bond. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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    Solid phase synthesis of cyclic peptides: model studies involving i-(i+4) side chain-to-side chain cyclisation (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 335-343 
    Details
    ISSN: 1075-2617
    Keywords: cyclic peptides ; human growth hormone ; lactam cyclisation ; side chain effects ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conditions for the synthesis of i-(i+4) side chain-to-side chain head-to-tail Lys→Glu and Glu→Lys linked cyclic peptides related to hypoglycaemic analogues of human growth hormone hGH [6-13] have been examined. The success of the cyclisation reaction with the corresponding resin-bound, partially protected linear peptides was found to be both reagent as well as sequence dependent, with competing inter-chain oligomerisation predominating in some cases. The results also indicated that protection with the bulky Fmoc group of the amino acid residues immediately adjacent to the side chain-deprotected Lys and Glu residues, which participate in the cyclisation reaction, enhanced the rate of lactam formation. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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    Conformational investigations on glycosylated threonine-oligopeptides of increasing chain length (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 58-71 
    Details
    ISSN: 1075-2617
    Keywords: circular dichroism ; FT-IR absorption ; glycopeptides ; 1H nuclear magnetic resonance ; oligo-peptides ; peptide conformation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Stepwise solution syntheses are described of the homo-oligomers Z-(Thr)n-NHCH3 (n=1-4, I1-4), Z-{[Gal(Ac)4β]Thr}n-NHCH3(n=1-5, II1-5) and Z-[(Galβ)Thr]n-NHCH3 (n=1-5, III1-5). Members of the III1-5 series were obtained by de-acetylation of the corresponding oligomers of the II1-5 series. The conformational preferences of the terminally protected homo-peptides of the three series were investigated by FT-IR absorption spectroscopy both in the solid state and in CDCl3 solution, at various concentrations. Proton NMR measurements in CDCl3 and in DMSO-d6 were also carried out and the effect of temperature variation on the chemical shifts of amide protons was determined in DMSO-d6 (range 298-335 K) and in CDCl3 (range 298-320 K). CD spectra were recorded in water and in TFE. Solubility problems prevented measurements in CDCl3 solution for Z-(Thr)4-NHCH3 and for the entire III1-5 series. The existence of unordered structures in the carbohydrate-free oligomers and of more or less extended, organized structures in the glycosylated derivatives is indicated by the NMR and IR measurements. The sugar moieties apparently show a structure-inducing effect on the peptide chain. ©1998 European Peptide Society and John Wiley & Sons, Ltd.
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    Linear and cyclic peptides as substrates for Lyn tyrosine kinase (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 33-45 
    Details
    ISSN: 1075-2617
    Keywords: conformational studies ; -OBg esters ; protein tyrosine kinase ; src-PTK ; synthetic peptides ; tyrosine phosphorylation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two Tyr residues are supposed to play a crucial role in the regulation of protein tyrosine kinases of the Src family. Autophosphorylation of Src Tyr416 correlates with enzyme activation, while phosphorylation of C-terminal Tyr527 by Csk gives rise to inactive forms of Src kinases.It has previously been demonstrated that the Src-like tyrosine kinase expressed by the oncogenelyndisplays a particularly high affinity (Km20 μm) toward the dimeric linear and cyclic derivatives of the heptapeptide H-Glu-Asp-Asn-Glu-Tyr-Thr-Ala-OH which reproduces the main autophosphorylation site of most of the Src enzymes. Under the experimental conditions used only one Tyr residue of the dimeric sequence can be phosphorylated [P. Ruzza, A. Calderan, B.Filippi, B. Biondi, A. Donella Deana, L. Cesaro, L. A. Pinna & G. Borin (1995) Int. J. Peptide Protein Res. 45, 529-539].The present study addresses the problem of the efficiency displayed by Lyn towards the two Tyr residues located at positions 5 and 12 of the dimeric peptide. To this purpose, two tetradecapeptides were synthesized by the classical solution method, each containing one of the two Tyr residues alternatively replaced by Phe, and the corresponding univocal cyclic form. A possible correlation between the different structural properties induced by the modifications of the native sequence and the ability of the peptides to act as Lyn substrates was noted. The kinetic data obtained indicate that Lyn phosphorylates the residues located at different positions in the two linear analogues differently. In particular, while the Tyr5, Phe12 derivative presents aKmvalue similar to those obtained for the dimeric linear and cyclic unmodified analogues, theKmvalue of the Phe5, Tyr12 derivative is two-fold higher than those found for the above-mentioned peptides. Moreover, as previously reported for the linear and cyclic dimeric forms of the native sequence, in the mono-tyrosine containing series of dimers the still conformationally flexible cyclic derivative shows a phosphorylation efficiency two-fold higher than those found for the linear derivatives. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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    Chemoselectively addressable HCan building blocks in peptide synthesis: L-homocanaline derivatives (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 72-80 
    Details
    ISSN: 1075-2617
    Keywords: L-homocanaline ; chemoselectively addressable amino acid ; oxime bond ; peptide synthesis ; glycopeptide ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (S-2-amino-5-(aminooxy)pentanoic acid (L-homocanaline, HCan), a structural analogue of lysine, contains a reactive alkyloxyamine side chain and is therefore considered to react chemoselectively with carbonyl compounds by forming a kinetically stable oxime bond. The chemical synthesis of L-homocanaline starting from protected glutamic acid derivatives is described. Two orthogonally protected homocanaline derivatives were synthesized and their use in standard SPPS procedures was exemplified for the synthesis of a chemoselectively addressable cyclic peptide for use in TASP design. Moreover, the wide range of applications of this unique building block was demonstrated for the chemoselective ligation of an unprotected disaccharide to a HCan containing model peptide resulting in a chimeric glycopeptide structure. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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    Applications of the Mitsunobu reaction in peptide chemistry (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 1-14 
    Details
    ISSN: 1075-2617
    Keywords: Mitsunobu reaction ; N-alkyl amino acid synthesis ; amino acid derivatives synthesis ; β-lactam formation ; peptide oxazolines and thiazolines ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Mitsunobu reaction - the nucleophilic substitution of an alcoholic hydroxyl group mediated by the redox system trialkylphosphine/dialkyl azodicarobxylate - is widely used in the chemistry of biologically active compounds. The paper deals with applications of the Mitsunobu reaction in amino acid and peptide chemistry. The process provides easy access to many unnatural amino acids and derivatives. Since the reaction occurs with complete inversion of the configuration at the carbinol chiral centre, it can be used for the synthesis of diastereoisomers of hydroxy- and tioprolines. Cyclization of β-hydroxy amino acid containing peptides under Mitsunobu reaction conditions leads to a constrained peptide that mimics the stabilizing reverse turn secondary structure. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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    Inhibition of cruzipain visualized in a fluorescence quenched solid-phase inhibitor library assay. D-Amino Acid Inhibitors for cruzipain, cathepsin B and cathepsin L (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 83-91 
    Details
    ISSN: 1075-2617
    Keywords: fluorescence quenched assay ; inhibitor library ; Trypanosoma cruzi ; cathepsin B and L inhibitors ; Parasitic protease inhibition ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A PEGA-resin was derivatized with a 3:1 mixture of hydroxymethyl benzoic acid and Fmoc-Lys(Boc)-OH and the fluorogenic substrate Ac-Y(NO2)KLRFSKQK(Abz)-PEGA was assembled on the lysine using the active ester approach. Following esterification of the hydroxymethyl benzoic acid with Fmoc-Val-OH a library XXX-k/r-XXXV containing approximately 200,000 beads was assembled by split synthesis. The resulting ‘one bead, two peptides’ library was subjected to extensive hydrolysis with cruzipain. One hundred darker beads were isolated and the 14 most persistently dark beads were collected and sequenced. The putative inhibitor peptides and several analogues were synthesized and found to be competitive μM to nM inhibitors of cruzipain in solution. The inhibitory activity was found to be unspecific to cruzipain when compared with cathepsins B and L and specific when compared with kallikrein. One of the inhibitors was docked into the active site of the cathepsin B and was found most probably to bind to the enzyme cavity in an unusual manner, owing to the inserted D-amino acid residue. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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    Bradykinin antagonists with dehydrophenylalanine analogues at position 5 (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 92-100 
    Details
    ISSN: 1075-2617
    Keywords: bradykinin ; antagonists ; dehydrophenylalanine ; smooth muscle contraction ; radio-ligand binding studies ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Continuing the studies on structural requirements of bradykinin antagonists, it has been found that analogues with dehydrophenylalanine (ΔPhe) or its ring-substituted analogues (ΔPhe(X)) at position 5 act as antagonists on guinea pig pulmonary artery, and on guinea pig ileum. Because both organs are considered to be bradykinin B2receptor tissues, the analogues with ΔPhe or ΔPhe(X) at position 5, but without any replacement at position 7, seem to represent a new structural type of B2receptor antagonist. All the analogues investigated act as partial antagonists; they inhibit the bradykinin-induced contraction at low concentrations and act as agonists at higher concentrations. Ring substitutions by methyl groups or iodine reduce both the agonistic and antagonistic activity. Only substitution by fluorine gives a high potency. Incorporation of ΔPhe into different representative antagonists with key modifications at position 7 does not enhance the antagonist activity of the basic structures, with one exception. Only the combination of ΔPhe at position 5 with DPhe at position 7 increases the antagonistic potency on guinea pig ileum by about one order of magnitude. Radio-ligand binding studies indicate the importance of position 5 for the discrimination of B2receptor subtypes. The binding affinity to the low-affinity binding site (KL) was not significantly changed by replacement of Phe by ΔPhe. In contrast, ring-methylation of ΔPhe results in clearly reduced binding to KL. The affinity to the high-affinity binding site (KH) was almost unchanged by the replacement of Phe in position 5 by ΔPhe, whereas the analogue with 2-methyl-dehydrophenylalanine completely failed to detect the KH-site. The peptides were synthesized on the Wang-resin according to the Fmoc/Butstrategy using Mtr protection for the side chain of Arg. The dehydrophenylalanine analogues were prepared by a strategy involving PyBop couplings of the dipeptide unit Fmoc-Gly-ΔPhe(X)-OH to resin-bound fragments. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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    The Maculatin peptides from the skin glands of the tree frog Litoria genimaculata: a comparison of the structures and antibacterial activities of Maculatin 1.1 and Caerin 1.1 (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 111-115 
    Details
    ISSN: 1075-2617
    Keywords: Litoria genimaculata ; skin glands ; glandular secretions ; peptides ; antibiotic activity ; maculatins 1 ; caerin 1.1 ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Six peptides have been isolated and characterized from the dorsal glands of the tree frog Litoria genimaculata. One of these is the known hypotensive peptide caerulein; the others have been named maculatins. The amino acid sequences of the maculatin peptides have been determined using a combination of fast atom bombardment mass spectrometry and automated Edman sequencing. Four of the maculatin peptides show antibiotic activity, with maculatin 1.1 [GLFGVLAKVAAHVVPAIAEHF(NH2;)] showing the most pronounced activity, particularly against Gram-positive organisms. Maculatin 1.1 resembles the known caerin 1 antibiotic peptides, except that four of the central amino acid residues (of the caerin 1 system) are missing in maculatin 1.1. A comparison of the antibiotic activity of maculatin 1.1 with those of caerin 1.1 is reported. ©1998 European Peptide Society and John Wiley & Sons, Ltd.
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    Solution conformation of an immunogenic peptide from HRV2: comparison with the conformation found in a complex with a Fab fragment of an anti-HRV2 neutralizing antibody (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 101-110 
    Details
    ISSN: 1075-2617
    Keywords: NMR ; random coil ; rhinovirus ; synthetic vaccine ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformation of a [15]-peptide (H-VKAETRLNPDLQPTE-NH2) from VP2 of rhinovirus HRV2 complexed with a Fab fragment was previously shown by X-ray crystallographic studies to be similar to the one found in the corresponding region of HRV1A. Antibodies raised against this peptide bind to and neutralize HRV2. In order to identify structural features preserved in solution that may explain the ability of this short peptide to mimic the structure of the protein surface, the peptide has been studied by NMR in aqueous solution as well as under denaturing conditions.The peptide is shown to be a random coil in solution. However, the sequence forming a 310 helix in the complex is biased into a helical conformation according to NOE intensity data as well as from urea and pH titrations. This sequence adopts the same conformation in an unrelated protein. NOE data suggest that a β-turn found in the complex may be sampled in solution. Also, Glu4, interacting with Arg6 in the crystal, has a reduced pKa value in solution. It is concluded that the local structure present in the random coil state of VP2(156-170) contains enough information to direct the production of antibodies that bind to and neutralize HRV2. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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    SPC3, an anti-HIV peptide construct derived from the viral envelope, binds and enters HIV target cells (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 479-485 
    Details
    ISSN: 1075-2617
    Keywords: anti-HIV agent ; Env-derived peptide ; SPC3 ; V3 domain ; HIV infection ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: SPC3 is a peptide construct (eight branches of the GPGRAF motif) derived from the consensus sequence present at the apex of the third variable domain of the human immunodeficiency virus (HIV) envelope (Env). It presents a potent anti-HIV activity and is currently tested in phase II clinical trials (FDA protocol 257A). Its mode of action remains unclear. It was thought that SPC3 exerts its effect both during HIV interaction with CD4+ cells but also through interference either with a post-binding event or with Env processing. Accordingly, SPC3 was supposed to be able to bind and to enter CD4+ cells. In this work, we addressed these points. SPC3 was found to interact with CD4+ cell membrane with a K0.5 value in the range of 500 nm. The binding of SPC3 to CD4+ cells involves its interaction with a cell membrane associated protein which is pronase sensitive and different from CD4. This interaction was similar from 2 to 37°C. The maximum binding occurred at acidic pH whereas the interaction was inhibited in alkaline conditions. We observed also that SPC3 was internalized rapidly into the cells - the maximal intracell amount was reached within 30 min - where it remained stable for at least 24 h. Altogether, these data suggest that SPC3 can exert its antiviral activity via interference with events occurring at the cell surface but also into the target cell. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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    Enkephalin analogs containing 4,4-difluoro-2-aminobutyric acid: Synthesis and fluorine effect on the biological activity (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 496-501 
    Details
    ISSN: 1075-2617
    Keywords: enkephalins ; DPDPE ; opioid agonists ; δ-receptor ; fluorine containing amino acid ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Analogs of Met-enkephalin and [d-Pen2, d-Pen5]enkephalin (DPDPE) containing the partially fluorinated amino acid 4,4-difluoro-2-aminobutyric acid (DFAB) in the 2- or 3-position of the peptide sequence were synthesized and their opioid activities and receptor selectivities were determined in vitro. The linear fluorinated [d-DFAB2, Met5-NH2]enkephalin showed μ and δ agonist potencies comparable to those of natural [Leu5]enkephalin. The partially fluorinated DPDPE analogs behaved differently as compared with their non-fluorinated correlates. While l-amino acid substitution in position 3 of DPDPE usually resulted in higher δ agonist potency than d-amino acid substitution, [d-DFAB3]DPDPE turned out to be a more potent δ agonist than [l-DFAB3]DPDPE. Furthermore, [d-DFAB3]DPDPE showed over 100-fold higher δ agonist potency than [d-Abu3]DPDPE (Abu=2-aminobutyric acid), indicating that the fluorine substituents interact favorably with a δ opioid receptor subsite. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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    Synthesis of peptide and pseudopeptide amides inhibiting the proliferation of small cell and epithelial types of lung carcinoma cells (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 486-495 
    Details
    ISSN: 1075-2617
    Keywords: substance P analogues ; synthesis of pseudopeptide amides ; small cell lung cancer ; inhibition of proliferation ; SCLC, small cell lung cancer ; BN, bombesin ; GRP, gastrin releasing peptide ; SP, substance P ; pHOPA, 4-hydroxyphenyl-acetyl ; MPA, 2-amino-3-methylpentane ; cycloLeu, 1-amino-1-cyclopentane-carbonyl ; d-MePhe, d-N-methyl-phenylalanyl ; LAH, lithium aluminium hydride ; MES, mercaptoethanesulfonic acid ; DCC, dicyclohexylcarbodiimide ; DCU, dicyclohexylurea ; Dnp, 2,4-dinitrophenyl ; HOPfp, pentafluorophenol ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Small cell lung cancer (SCLC) cell lines produce and secrete various peptide hormones, e.g. bombesin (BN)/gastrin releasing peptide (GRP) like peptides that are proposed to function as their autocrine growth factors. To inhibit the proliferative effect of these hormones we have synthesized short chain BN[7-14]-analogues replacing the C-terminal peptide bond by a methylene-amino (-CH2NH-) unit and introducing d-Phe or d-Ser into position 12. As several substance P (SP) analogues were found to inhibit the growth of SCLC cells, some short chain SP-analogues have been synthesized. (Pseudo)octapeptides were synthesized in solution, by fragment condensation using the DCC/HOPfp method. Fragments and SP-analogues were synthesized stepwise using pentafluorophenyl esters. The resistance to hydrolysis of the reduced peptide bond made permitted exact quantification of the Leuψ(CH2NH)Leu pseudopeptide in hydrolysates. The binding ability of both types of peptides to BN-receptors on Swiss 3T3 mouse fibroblast cells and their antiproliferative effect on NCI-H69 human SCLC cell line have been tested and compared with a short chain SP-antagonist pHOPA-d-Trp-Phe-d-Trp-Leu-Leu-NH2 (R) previously described as a potent inhibitor of SCLC proliferation. While BN-analogues showed weak activity in inhibition of proliferation of SCLC cells, SP-analogues 6: d-MePhe-d-Trp-Phe-d-Trp-Leuψ(CH2NH)-Leu-NH2 and 7: d-MePhe-d-Trp-Phe-d-Trp-Leu-MPA, in spite of greatly diminished affinity towards the BN-receptor, inhibited SCLC proliferation more effectively than R (6: IC50=2 μm, 7: IC50=5 μm and R: IC50=10 μm). Moreover, 6 inhibited the respiratory activity of SK-MES 1 epithelial type of lung carcinoma cells in proliferating but not in the quiescent state, suggesting that the antiproliferative effect of these compounds is not due to simple cytotoxicity. These short chain analogues of SP might be promising candidates as therapeutic agents in the treatment of SCLC. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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    Presentation of antigenic peptides by products of the major histocompatibility complex (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 182-194 
    Details
    ISSN: 1075-2617
    Keywords: MHC class I ; MHC class II ; peptide binding groove ; anchor residues ; hydrophobic pockets ; peptide termini ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Molecules encoded by the major histocompatibility complex (MHC) are polymorphic integral membrane proteins adapted to the presentation of peptide fragments of foreign antigens to antigen-specific T-cells. The diversity of infectious agents to which an immune response must be mounted poses a unique problem for receptor-ligand interactions; how can proteins whose polymorphism is necessarily limited bind an array of peptides almost infinite in its complexity? Both MHC class I and class II determinants have achieved this goal by harnessing a limited number of peptide side chains to anchor the epitope in place while exploiting conserved features of peptide structure, independent of their primary sequence. While class I molecules interact predominantly with the N- and C-termini of peptides, class II determinants form an extensive hydrogen bonding network along the length of the peptide backbone. Such a strategy ensures high-affinity binding, while selectively exposing the unique features of each ligand for recognition by the T-cell receptor. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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    PEGA supports for combinatorial peptide synthesis and solid-phase enzymatic library assays (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 195-210 
    Details
    ISSN: 1075-2617
    Keywords: PEGA ; solid-phase enzyme assay ; PEG ; MMP-9 ; fluorescence quenched peptides libraries ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Permeable resins cross-linked with long PEG chains were synthesized for use in solid-phase enzyme library assays. High molecular weight bis-amino-polyethylene glycol (PEG) 4000, 6000, 8000 were synthesized by a three-step reaction starting from PEG-bis-OH. Macromonomers were synthesized by partial or di-acryloylation of bis-amino-PEG derivatives. Bis/mono-acrylamido-PEG were copolymerized along with acrylamide by inverse suspension copolymerization to yield a less cross-linked resin (Type I, compounds 6-9). Furthermore, acryloyl-sarcosin ethyl ester was co-polymerized along with bis-acrylamido PEG to obtain more crosslinked capacity resin (Type II, compounds 13-19). N,N-Dimethylacrylamide was used as a co-monomer in some cases. The polymer was usually obtained in a well-defined beaded form and was easy to handle under both wet and dry conditions. The supports showed good mechanical properties and were characterized by studying the swelling properties, size distribution of beads, and by estimating the amino group capacity. Depending on the PEG chain length, the monomer composition and the degree of cross-linking the PEGA supports showed a high degree of swelling in a broad range of solvents, including water, dichloromethane, DMF, acetonitril, THF and toluene; no swelling was observed in diethyl ether. The PEGA resins (Type I) with an amino acid group capacity between 0.07 and 1.0 mmol/g could be obtained by variation of the monomer composition in the polymerization mixture. Fluorescent quenched peptide libraries were synthesized on the new polymer using a multiple column library synthesizer and incubated with the matrix metalloproteinase MMP-9 after it had been activated by 4-aminophenyl mercuric acetate resulting in 67/83 kDa active enzyme. The bright beads were separated manually under a fluorescence microscope and sequenced to obtain peptide substrates for MMP-9. After treatment with ethylene diamine, high-loaded resins (Type II) have been employed in continuous flow peptide synthesis to yield peptides in excellent yield and purity. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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    Synthesis and characterization of a new biotinylated gramicidin (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 371-377 
    Details
    ISSN: 1075-2617
    Keywords: biotinylgramicidin ; peptide synthesis ; planar lipid bilayers ; ion channel ; biotin-avidin interactions ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new linear gramicidin analog bearing a biotinyl group grafted on C-terminal part was designed to study ligand-receptor interactions. The C-terminal alcohol in the native peptide was first replaced by an amino group. Then the peptide was synthesized on a polystyrene resin functionalized by the 2-chlorotrityl chloride following a biotinylation performed in solution. This new N′-biotinyl-(EDA)15-Gramicidin A was reconstituted in planar lipid bilayers and exhibited channel activities similar to those of natural gramicidin, with unitary conductance value about 30 ps in 1 m KCl. Furthermore this ionophore activity was quenched by addition of streptavidin in the surrounding medium. Our system is an outstanding tool for monitoring ligand-receptor interactions and could be used for designing a new biosensor. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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    Binding of rationally designed non-natural peptides to the human leukocyte antigen HLA-B*2705 (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 378-388 
    Details
    ISSN: 1075-2617
    Keywords: HLA-B27 ; circular dichroism ; thermal denaturation ; computer-aided ligand design ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: High-affinity ligands of non-peptidic nature, binding to the class I major histocompatibility complex protein HLA B*2705 whose expression is strongly linked to the pathogenesis of the autoimmune disease ankylosing spondylitis, should give way to a selective immunotherapy by blocking or antagonising the interaction with autoreactive T cell clones. Here we present experimental data on the binding of modified peptides, designed to optimally bind to HLA-B*2705 by filling a hydrophobic binding pocket (pocket D) with nonencoded aromatic amino acids. Three peptides with altered side chains (alpha-naphthylalanine, beta-naphthylalanine and homophenylalanine) in position 3 were synthesised. The thermal denaturation profiles of the HLA protein in complex with the modified peptides, monitored by circular dichroism spectroscopy, showed a significant shift towards higher melting temperatures with respect to the parent T cell epitope. The proposed binding mode of the nonnatural peptides was checked by site-directed mutagenesis of the pocket D, hypothesised to accommodate the large hydrophobic side chains. Reducing the size and depth of the pocket by mutating Leu l56 into Trp only affects the binding of the non-natural ligands, thus providing experimental evidence that the nonnatural peptide amino acids bind as predicted to the host MHC protein. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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    Conformation and membrane activity of an analogue of the peptaibol antibiotic trichogin GA IV with a lipophilic amino acid at the N-terminus (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 389-399 
    Details
    ISSN: 1075-2617
    Keywords: conformational analysis ; lipo-amino acid ; membrane activity ; NMR ; peptide antibiotic ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have synthesized by solution-phase methods two analogues of the 11-residue lipopeptaibol antibiotic trichogin GA IV in which the N-terminal n-octanoyl group is replaced either by an N-acetylated 2-amino-2-methyl-l-undecanoic acid or by an N-acetylated α-aminoisobutyric acid. CD, FTIR absorption, and NMR analyses unequivocally show that the main structural features of trichogin GA IV are preserved in these analogues. Since only the peptide containing the lipophilic chain exhibits membrane-modifying properties, these results strongly support the view that moving the long acyl moiety from the Nα-blocking group to the side chain of the N-terminal extra-residue does not affect the conformational properties or the membrane activity of trichogin GA IV. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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    1H NMR conformational study on n-terminal nonapeptide sequences of HIV-1 Tat protein: a contribution to structure-activity relationships (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 400-410 
    Details
    ISSN: 1075-2617
    Keywords: HIV-1 Tat ; dipeptidyl peptidase IV ; 1H NMR spectroscopy ; MD calculations ; structure-activity relationships ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: On the basis of our recent results, the N-terminal sequence of HIV-1 Tat protein as a natural competitive inhibitor of dipeptidyl peptidase IV (DP IV) is supposed to interact directly with the active site of DP IV hence mediating its immunosuppressive effects via specific DP IV interactions. Of special interest is the finding that amino acid substitutions of the Tat(1-9) peptide (MDPVDPNIE) in position 5 with S-isoleucine and in position 6 with S-leucine led to peptides with strongly reduced inhibitory activity suggesting differences in the solution conformation of the three analogues. Therefore, 1H NMR techniques in conjunction with molecular modelling have been used here to determine the solution structure of Tat(1-9), I5-Tat(1-9) and L6-Tat(1-9) and to examine the influence of amino acid exchanges on structural features of these peptides. The defined structures revealed differences in the conformations what might be the reason for different interactions of these Tat(1-9) analogues with certain amino acids of the active site of DP IV. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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    Microscopic observations of the different morphological changes caused by anti-bacterial peptides on Klebsiella pneumoniae and HL-60 leukemia cells (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 413-425 
    Details
    ISSN: 1075-2617
    Keywords: modes of action ; anti-bacterial ; cecropins ; morphology ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Natural anti-bacterial peptides cecropin B (CB) and its analogs cecropin B-1 (CB-1), cecropin B-2 (CB-2) and cecropin B-3 (CB-3) were prepared. The different characteristics of these peptides, with amphipathic/hydrophobic α-helices for CB, amphipathic/amphipathic α-helices for CB-1/CB-2, and hydrophobic/hydrophobic α-helices for CB-3, were used to study the morphological changes in the bacterial cell, Klebsiella pneumoniae and the leukemia cancer cell, HL-60, by scanning and transmission electron microscopies. The natural and analog peptides have comparable secondary structures as shown by circular dichroism measurements. This indicates that the potency of the peptides on cell membranes is dependent of the helical characteristics rather than the helical strength. The microscopic results show that the morphological changes of the cells treated with CB are distinguishably different from those treated with CB-1/CB-2, which are designed to have enhanced anti-cancer properties by having an extra amphipathic α-helix. The morphological differences may be due to their different modes of action on the cell membranes resulting in the different potencies with lower lethal concentration and higher concentration of 50% inhibition (IC50) of CB on bacterium and cancer cell, respectively, as compared with CB-1/CB-2 (Chen et al. 1997. Biochim. Biophys. Acta 1336, 171-179). In contrast, CB-3 has little effect on either the bacterium or the cancer cell. These results provide microscopic evidence that different killing pathways are involved with the peptides. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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    Solution structure of peptides from HIV-1 Vpr protein that cause membrane permeabilization and growth arrest (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 426-435 
    Details
    ISSN: 1075-2617
    Keywords: HIV-1 ; viral protein ; solution structure ; sequence motifs ; helices ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Vpr, one of the accessory gene products encoded by HIV-1, is a 96-residue protein with a number of functions, including targeting of the viral pre-integration complex to the nucleus and inducing growth arrest of dividing cells. We have characterized by 2D NMR the solution conformations of bioactive synthetic peptide fragments of Vpr encompassing a pair of H(F/S)RIG sequence motifs (residues 71-75 and 78-82 of HIV-1 Vpr) that cause cell membrane permeabilization and death in yeast and mammalian cells. Due to limited solubility of the peptides in water, their structures were studied in aqueous trifluoroethanol. Peptide Vpr59-86 (residues 59-86 of Vpr) formed an α-helix encompassing residues 60-77, with a kink in the vicinity of residue 62. The first of the repeated sequence motifs (HFRIG) participated in the well-defined α-helical domain whereas the second (HSRIG) lay outside the helical domain and formed a reverse turn followed by a less ordered region. On the other hand, peptides Vpr71-82 and Vpr71-96, in which the sequence motifs were located at the N-terminus, were largely unstructured under similar conditions, as judged by their CαH chemical shifts. Thus, the HFRIG and HSRIG motifs adopt α-helical and turn structures, respectively, when preceded by a helical structure, but are largely unstructured in isolation. The implications of these findings for interpretation of the structure-function relationships of synthetic peptides containing these motifs are discussed. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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    Biological and conformational studies on analogues of a synthetic peptide enhancing HIV-1 infection (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 436-448 
    Details
    ISSN: 1075-2617
    Keywords: CD ; FT-IR ; gp120-CD4 interaction ; HIV-1 ; structure-function studies ; solid-phase peptide synthesis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have previously demonstrated that a 23-amino acid peptide derived from the V3 loop of the surface glycoprotein of the HIV-1 strain MN is able to bind CD4 and to enhance HIV-1 infection. Further studies have suggested that the peptide/CD4 interaction induces an increase in both CD4 expression and CD4/gp120 binding affinity. This paper describes the biological and physico-chemical characterization of three analogues of reduced sequence that have been designed in order to identify the minimum active sequence of this peptide corresponding to the MN-HIV-1 principal neutralizing domain. Biological studies indicate that the entire sequence is required for biological activity and that the sequence 1-18 presents an inhibitory activity. CD and FT-IR absorption data are discussed here in order to identify possible structure-function correlations. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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    Monitoring of solid phase peptide synthesis by FT-IR spectroscopy (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 461-470 
    Details
    ISSN: 1075-2617
    Keywords: monitoring ; solid phase peptide synthesis ; FT-IR spectroscopy ; difficult sequences ; aggregation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Aggregation phenomena of growing peptides on the resin have seldom been investigated. We report here how conformations are determined by FT-IR spectroscopy. Therefore the sequence 80-99 of HIV 1-protease was synthesized. After every coupling a resin sample was taken out of the reaction column and a FT-IR spectrum recorded. The results were compared with the UV monitoring obtained from another synthesis of the same peptide. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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    Tuning micelles of a bioactive heptapeptide biosurfactant via extrinsically induced conformational transition of surfactin assembly (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 449-458 
    Details
    ISSN: 1075-2617
    Keywords: peptide surfactant ; surfactin ; conformation ; micelles ; biosurfactant ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have studied the effects of extrinsic environmental conditions on the conformation of surfactin, a heptapeptide biosurfactant from Bacillus subtilis, in aqueous solutions. It has been made clear that temperature, pH, Ca2+ ions and the synthetic nonionic surfactant hepta-ethylene glycol (C12E7) affect the conformation of surfactin in aqueous solutions. The β-sheet formation reached a maximum at 40°C both in presence and absence of (C12E7) and the nonionic surfactant enhances the β-sheet formation even at 25°C. Ca2+ induced the formation of a-helices and caused this transition at 0.3 mm with surfactin monomers or at 0.5 mm with surfactin micelles, but above these transition concentrations of Ca2+ β-sheets were observed. In micellar solution the β-sheet structure was stabilized at pH values below 7 or upon addition of Ca2+ in concentrations above 0.5 mm. Our results indicated that the bioactive conformation of surfactin is most likely the β-sheets when the molecules are assembled in micelles. The β-sheet structure in micelles could be retained by tuning the micelles. Surfactin micelles could be tuned in the bioactive conformation by manipulating pH, temperature, Ca2+ or (C12E7) concentrations in surfactin solutions. Our results strongly indicated that Ca2+ and other molecules (such as C12E7) may function as directing templates in the assembly and conformation of surfactin in micelles. Thus, we suggest environmental manipulation and template-aided micellation (TAM) as a new approach for preparing predesigned micelles, microemulsions or micro-spheres for specific application purposes. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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    N-hydroxy-amide analogues of MHC-class I peptide ligands with nanomolar binding affinities (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 471-478 
    Details
    ISSN: 1075-2617
    Keywords: N-hydroxy peptides ; peptides ; ligands ; MHC ; solid-phase synthesis ; MHC, major histocompatibility complex ; BSA, bovine serum albumin ; DMEM, Dulbecco s modified Eagle'rsquo;s medium ; FITC, fluorescein isothiocyanate ; TcR, T cell receptor, Alloc, allyloxycarbonyl ; Bzl, benzyl ; NMM, N-methyl morpholine ; DIC, diisopropylcarbodiimide ; TIS, triisopropylsilane ; DIPEA, diisopropylethylamine ; HOBt, 1-hydroxybenzotriazole ; DBU, 1,8-diazabicyclo[5.4.0]undecen-7-ene ; HATU, O-(7-azabenzotriazol-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate ; HOAt, 7-aza-1-hydroxybenzotriazole ; CPY, carboxypeptidase Y ; APM, aminopeptidase M ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A novel class of major histocompatibility complex class I (MHC-I) ligands containing an N-hydroxy-amide bond was designed on the basis of the natural epitope SIINFEKL, and synthesized on solid phase. The capacity of these compounds to bind to the MHC-I molecule H-2Kb and to induce T cell responses was analysed in comparison with the corresponding glycine containing variant of SIINFEKL. Binding to the MHC molecule was diminished by the N-hydroxy group at positions 2 and 3 of the oligomer and improved in the case of positions 4, 5, 6 and 7. No change was seen for position 1. The efficacy of T cell stimulation was strongly reduced by the modification of all positions except for position 1. A complete loss of activity was found for the N-hydroxy variant in positions 4 and 6. N-Hydroxy amide-containing peptides displayed an enhanced stability to enzymatic degradation. This new class of MHC ligand can become instrumental as immunomodulatory reagent in various disease situations. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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    Capping and dynamic relation between domains 1 and 2 of gelsolin (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 116-127 
    Details
    ISSN: 1075-2617
    Keywords: gelsolin ; actin ; capping proteins ; synthetic peptides ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Gelsolin is a protein that severs and caps actin filaments. The two activities are located in the N-terminal half of the gelsolin molecules. Severing and subsequent capping requires the binding of domains 2 and 3 (S2-3) to the side of the filaments to position the N-terminal domain 1 (S1) at the barbed end of actin (actin subdomains 1 and 3). The results provide a structural basis for the gelsolin capping mechanism. The effects of a synthetic peptide derived from the sequence of a binding site located in gelsolin S2 on actin properties have been studied. CD and IR spectra indicate that this peptide presented a secondary structure in solution which would be similar to that expected for the native full length gelsolin molecule. The binding of the synthetic peptide induces conformational changes in actin subdomain 1 and actin oligomerization. An increase in the polymerization rate was observed, which could be attributed to a nucleation kinetics effect. The combined effects of two gelsolin fragments, the synthetic peptide derived from an S2 sequence and the purified segment 1 (S1), were also investigated as a molecule model. The two fragments induced nucleation enhancement and inhibited actin depolymerization, two characteristic properties of capping. In conclusion, for the first time it is reported that the binding of a small synthetic fragment is sufficient to promote efficient capping by S1 at the barbed end of actin filaments. ©1998 European Peptide Society and John Wiley & Sons, Ltd.
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    Preparation of fluorescence quenched libraries containing interchain disulphide bonds for studies of protein disulphide isomerases (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 128-137 
    Details
    ISSN: 1075-2617
    Keywords: Disulphide bond formation ; fluorescence quenched library ; peptide library ; protein ; disulphide isomerase ; solid-phase assay ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Protein disulphide isomerase is an enzyme that catalyses disulphide redox reactions in proteins. In this paper, fluorogenic and interchain disulphide bond containing peptide libraries and suitable substrates, useful in the study of protein disulphide isomerase, are described. In order to establish the chemistry required for the generation of a split-synthesis library, two substrates containing an interchain disulphide bond, a fluoroescent probe and a quencher were synthesized. The library consists of a Cys residue flanked by randomized amino acid residues at both sides and the fluoroescent Abz group at the amino terminal. All the 20 natural amino acids except Cys were employed. The library was linked to PEGA-beads via methionine so that the peptides could be selectively removed from the resin by cleavage with CNBr. A disulphide bridge was formed between the bead-linked library and a peptide containing the quenching chromophore (Tyr(NO2)) and Cys(pNpys) activated for reaction with a second thiol. The formation and cleavage of the interchain disulphide bonds in the library were monitored under a fluoroescence microscope. Substrates to investigate the properties of protein disulphide isomerase in solution were also synthesized. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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    Peptide siderophores (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 147-181 
    Details
    ISSN: 1075-2617
    Keywords: peptide ; siderophore ; microbial metabolites ; iron ; complex ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Siderophores are low molecular weight iron chelators, produced by virtually all bacteria, fungi and some plants. They serve to deliver the essential element iron, barely soluble under aerobic conditions, into microbial cells. Siderophores are therefore important secondary metabolites which are very often based on amino acids and their derivatives. Biosynthesis, transport, regulation and chemical synthesis of natural siderophores and their analogues is of considerable interest for the protein and peptide chemist. This review gives an overview of the structural classes of peptidic siderophores, along with data on their biosynthesis. On a number of representative examples, strategies and schemes of their chemical synthesis are described. ©1998 European Peptide Society and John Wiley & Sons, Ltd.
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    An efficient and convenient procedure for the synthesis of nα-Fmoc-O-monobenzyl phosphonotyrosine (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 138-141 
    Details
    ISSN: 1075-2617
    Keywords: monobenzyl phosphotyrosine ; phosphotyrosine ; Fmoc phosphotyrosine ; phosphonotyrosine ; monobenzyl phosphonotyrosine ; 1H-NMR, proton nuclear magnetic resonance ; TBDMSCl, tert-butyldimethylsilyl chloride ; Fmoc-ONSu, Fmoc-N-hydroxysuccinimide ; NMM, N-methylmorpholine ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An efficient procedure is described for the synthesis of Nα-Fmoc-O-monobenzyl phosphonotyrosine from the corresponding dibenzyl derivative by monodebenzylation in the presence of sodium iodide. A simple work up procedure removes the by-products and the monobenzylated phosphono product is obtained in high yield. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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    Synthesis and activity of dimeric bradykinin antagonists containing diaminodicarboxylic acid bridge residues (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 289-293 
    Details
    ISSN: 1075-2617
    Keywords: Bradykinin antagonist ; dimer ; diaminodicarboxylic acid ; bridge residue ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Enhancement of a ligand's interaction with a receptor through presenting the ligand in multimeric form is a topic of general interest. Thus dimerization of single-chain bradykinin antagonist peptides has previously been shown to be beneficial in terms of potency and duration of action. While crosslinking polypeptides at terminal positions using suitable dicarboxylic acids and diamines is comparatively straightforward synthetically, internal dimerizations are usually achieved through oxidation or double S-alkylations of cysteine residues, resulting in metabolically unfavourable disulphide and thioether cross-links. Using suitably modified standard solid-phase peptide synthesis protocols, dimeric bradykinin antagonist peptides [H-(d-Arg)-Arg-Pro-Hyp-Gly-Phe]2-X-[(d-Phe)-Leu-Arg-OH]2 were synthesized where X corresponds to a l,l-2,7-diaminosuberic or l,l-2,9-diaminosebacic acid residue, respectively. The biological activity of these peptides was comparable to that of conventional dimeric bradykinin antagonists cross-linked through cystine or bis(succinimido)alkyl bridges. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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    Cryochemistry: freezing effect on peptide coupling in different organic solutions (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 300-304 
    Details
    ISSN: 1075-2617
    Keywords: Cryochemistry ; frozen organic solution ; peptide coupling ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The freezing effect on peptide coupling in organic solutions of different polarity has been investigated and compared with the results obtained in liquid phase. The model reaction of DCC-activated coupling of Boc-Ala-Phe-OH with H-Ala-OBut has been carried out in dioxane, dimethylsulfoxide and formamide, as well as in mixtures (90%/10%, v/v) of dioxane with acetonitrile, dimethylformamide, dimethylsulfoxide and formamide.The reactions have been traced and evaluated by RP-HPLC analysis. Freezing the reaction mixture resulted in all cases in a significant suppression of the N-dipeptidylurea side-product formation together with a slight decrease of tripeptide epimerization. The coupling yields and the side effects depended on the solvent, with the dioxane and dioxane/acetonitrile mixture produced the best results. The role of freezing and solvent in the improved results is discussed. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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    Coloured peptides: synthesis, properties and use in preparation of peptide sub-library kits (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 294-299 
    Details
    ISSN: 1075-2617
    Keywords: Coloured neurotensin analogues ; coloured peptides ; coloured peptide libraries ; peptide labelling with chromophores ; peptide synthesis on coloured support ; solubilizing tags ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several methods were developed for the solid-phase synthesis (SPPS) of coloured peptides and peptide libraries. At first a bifunctional red compound, 4-(4-(N-ethyl-N-(3-(tert-butyloxycarbonyl)aminopropyl)amino)phenylazo)benzoic acid (Boc-EPAB), was coupled with chloromethyl resin to obtain a new solid support suitable for SPPS using Boc chemistry. Peptides synthesized on this coloured resin had the chromophore at their C-termini. N-terminally coloured peptides were synthesized on a traditional solid support, coupled with chromophoric carboxylic acid before cleavage. A model pentapeptide, Phe-Ala-Val-Leu-Gly, and its ten derivatives were synthesized and their properties studied. It was found that the presence of chromophores decreases the water solubility of peptides. However, insertion of solubilizing tags (penta-lysine sequences or polyoxyethyl chains) into the molecule of any coloured derivative resulted in enhancement of the solubility. The RP-HPLC hydrophobicity indexes (ϕ0) of the coloured peptides were also determined because ϕ0 values are closely related to their water solubility. A coloured pentapeptide library was synthesized using the portioning-mixing method. Each component of this library contained the red azo dye (EPAB) and the penta-lysine tag. Before the last coupling step the samples were not mixed. All of the 19 sub-libraries obtained after cleavage were readily soluble in water, giving intense red solutions.The effect of chromophore (EPAB) and/or penta-lysine solubilizing tag on the biological activity was also studied. Potencies of the bovine neurotensin 8-13 fragment and its different coloured and penta-lysine derivatives were compared in isolated longitudinal muscle strips of guinea pig ileum. It was shown that the hexapeptide with penta-lysine tag had almost the same activity as the 8-13 fragment itself. The activity of the EPAB-derivative was found to be rather low. However, the presence of the solubilizing tag in the coloured hexapeptide compensated the negative effect of the chromophore. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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    A conformational study in solution of pro-somatostatin fragments by NMR and computational methods (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 305-318 
    Details
    ISSN: 1075-2617
    Keywords: pro-somatostatin ; β-turn ; NMR ; computational methods ; conformational analysis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The results of a conformational study by nuclear magnetic spectroscopy and computational methods on a series of point-mutated synthetic peptides, containing 14 amino acid residues and mimicking the region containing the Arg-Lys dibasic cleavage site of pro-somatostatin, have confirmed the possible role of a well defined secondary structure in the recognition phenomenon by processing enzymes.The importance of the residues located near the Arg-Lys dibasic site in the C-terminal region of the pro-hormone for the cleavage of the precursor into somatostatin-14 has been confirmed. The present structural analysis indicates the occurrence of two β-turns in the 4-7 and 11-14 regions, flanking the cleavage site, for all the peptides recognized as substrates by the processing enzyme.Interestingly, in the point-mutated analogue not processed by the enzyme and containing the replacement of proline by alanine in position 5 the first β-turn is displaced by one residue and involves the Ala5-Arg8 segment. This observation may explain the lack of recognition by the maturation enzyme. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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    Influence of the secondary structure on the pore forming properties of synthetic alamethicin analogs: NMR and molecular modelling studies (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 344-354 
    Details
    ISSN: 1075-2617
    Keywords: ion channels ; amphipathicity ; α-helices ; bilayers ; SDS micelles ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthetic alamethicin analogs, in which all Aib residues had been replaced by Leu (L2) then proline 14 replaced by an alanine (L5), were studied in SDS micelles using circular dichroism and NMR spectroscopy. Nuclear Overhauser effects were used as constraints for molecular modelling. The structures determined for both peptides in SDS micelles were compared with those previously obtained in methanol in order to establish a secondary structure/ionophore activity relationship. Our results indicated that a shortening of peptide helices could be responsible for the observed decrease in ion channel lifetimes. However, the length of helices may not by itself explain the drastic destabilization of channels when Pro14 of alamethicin is replaced by Ala in L5. Indeed analysis of the helical wheel of L5 reveals heterogeneity in the amphipathicity depending on the medium. Thus, loss of amphipathicity seems to underly the observed destabilization of channels. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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    Localisation of a protein core-specific epitope from gastrointestinal mucin (MUC2). The effect of epitope immobilisation on antibody recognition (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 319-326 
    Details
    ISSN: 1075-2617
    Keywords: MUC2 mucin ; synthetic peptides ; antibody recognition in solution ; antibody recognition on immobilised peptides ; B cell epitope of MUC2 mucin ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Human intestinal mucins are high molecular weight glycoproteins which protect and lubricate the epithelium of the gastrointestinal tract. In cases of malignant disease, mucins are abnormally expressed, overproduced or underglycosylated. This feature may enable the mucins to serve as tumour markers. The MUC2 mucin largely consists of a variable number of tandem repeats of a 23 amino acid sequence, 1PTTTPITTTTTVTPTPTPTGTQT23. In this study we have localised the minimal and the optimal epitope within this region by the previously developed protein core specific 996 monoclonal antibody using synthetic peptides. Several overlapping and truncated peptides related to the tandem repeat unit have been prepared by solid-phase methodology. Other mucin peptides were synthesised on the tips of polyethylene pins, and these remained C-terminally attached to the pins for comparative investigations. The interaction of the 996 monoclonal antibody with the synthetic peptides was studied either in solution by competition RIA or on immobilised peptides by indirect ELISA experiments. These experiments show that the minimal epitope recognised by the 996 antibody is the Ac-19TGTQ22 (IC50=3100 μm in solution). For the optimal 996 antibody binding in solution the 16PTPTGTQ22 heptapeptide (IC50=3 μm) is required. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
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    Extraction of equine chorionic gonadotrophin from pregnant mare plasma by direct adsorption on chromatographic media (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 22-25 
    Details
    ISSN: 0006-3592
    Keywords: eCG ; pregnant mare serum gonadotrophin ; batch sorption ; hormone purification ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Equine chorionic gonadotrophin (eCG) is a hormone of practical value in veterinary medicine and animal production. Here we report a novel preparation procedure based on its direct adsorption onto anionic-exchange resins in a batch-wise mode. The active plasma is previously conditioned to reduce pH and ionic strength to required levels. After the adsorption stage, a 90% recovery of the initial eCG is achieved, with a concentration factor of about 50 and an enrichment factor around 500, with high preservation of biological activity. Further purification is carried out by cation-exchange column chromatography. The recovery for the whole process is higher than 70%, and the final potency of the preparation is close to 4000 IU/mg. The process is well suited for its application to the industrial scale. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 22-25, 1998.
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    Modification of ultrafiltration membrane with gelatin protein (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 26-34 
    Details
    ISSN: 0006-3592
    Keywords: ultrafiltration ; modification ; gelatin ; fouling ; protein ; zeta potential ; membrane ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A dye-binding procedure was developed for the analysis of protein attached to the membrane, with bound and adsorbed forms of attachment being distinguished. The relationship between modification procedure and protein attachment was explored and related to flux, streaming potential, and rejection with variation of pH. The effects of attaching four different types of gelatin to the membrane were studied. Assessment was made of modifications for improvement of flux and selectivity in the presence of protein foulants. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 26-34, 1998.
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    Recombinant production and purification of novel antisense antimicrobial peptide in Escherichia coli (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 55-61 
    Details
    ISSN: 0006-3592
    Keywords: synthetic antimicrobial peptide ; prochymosin ; recombinant ; expression ; purification ; fusion protein ; inclusion bodies ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A fusion protein was genetically engineered that contains an antimicrobial peptide, designated P2, at its carboxy terminus and bovine prochymosin at its amino terminus. Bovine prochymosin was chosen as the fusion partner because of its complete insolubility in Escherichia coli, a property utilized to protect the cells from the toxic effects of the antimicrobial peptide. This fusion protein was purified by centrifugation as an insoluble inclusion body. A methionine linker between prochymosin and the P2 peptide enabled P2 to be released by digestion with cyanogen bromide. Cation exchange HPLC followed by reversed-phase HPLC were used to purify the P2 peptide. The recombinant P2 peptide's molecular mass was confirmed by mass spectrometry to within 0.1% of the theoretical value (2480.9 Da), and the antimicrobial activity of the purified recombinant P2 against E. coli D31 was determined to be identical to that of the chemically synthesized peptide (minimal inhibitory concentration of 5 mg/mL). Although the yield of the fusion protein after expression by the cells was high (16% of the total cell protein), the percentage recovery of the P2 peptide in the inclusion bodies was relatively low, which appears to be due to losses in the cyanogen bromide digestion step. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 55-61, 1998.
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    Plasmid stability of recombinant Pseudomonas sp. B13 FR1 pFRC20P in continuous culture (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 62-70 
    Details
    ISSN: 0006-3592
    Keywords: plasmid stability ; recombinant microorganism ; continuous culture ; Pseudomonas sp. B13 FR1 pFRC20P ; degradation of aromatic compounds ; chlorobenzoate ; methylbenzoate ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Plasmid stability of recombinant Pseudomonas sp. B13 FR1 pFRC20P, a strain capable of mineralizing 3- and 4-chlorobenzoate and 4-methylbenzoate, was investigated in continuous culture. The hybrid cosmid pFRC20P enables the strain to mineralize 4-methylbenzoate. Rapid plasmid loss was observed under nonselective conditions using 3-chlorobenzoate as the substrate. Plasmid stability decreased with increasing dilution rate. Despite the growth advantage of the generated plasmid free cells a total depletion of plasmid bearing cells was not observed. After approximately 50 generations the fraction of plasmid bearing cells reached a constant level of 10%, which was stably maintained during the next 25 generations. Cells from this stage were used to inoculate a new culture that resulted in a stable level of 50% plasmid bearing cells. By a temporary substrate change to selective conditions (4-methylbenzoate), this level could be further increased to 70%. Literature models on plasmid stability could not be applied to describe the experimental data. Therefore, a new but unstructured model was developed to describe the experimental results. The model is based on the existence of three subpopulations: a plasmid free one, an original plasmid bearing one with a growth disadvantage compared to plasmid free cells, and a second plasmid bearing subpopulation with increased stability that is generated from the original one and has a growth rate comparable to the plasmid free cells. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 62-70, 1998.
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    The influence of impeller type in pilot scale Xanthan fermentations (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 95-108 
    Details
    ISSN: 0006-3592
    Keywords: Xanthan fermentation ; impeller type ; power consumption ; mixing ; oxygen transfer ; Xanthan productivity ; product quality ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The rheological complexity of Xanthan fermentations presents an interesting problem from a mixing viewpoint, because the phenomena of poor bulk blending and low oxygen mass transfer rates inherent in highly viscous fermentations (and their consequences) can be systematically investigated, even at the pilot plant scale. This study in a 150 L fermentor compares the physical and biological performance of four pairs of impellers: a standard Rushton turbine, a large diameter Rushton turbine, a Prochem Maxflo T, and a Scaba 6SRGT. Accurate in-fermentor power measurements, essential for the comparison of impellers in relation to operating costs are also reported. It is demonstrated that the agitator performance in Xanthan fermentations is very specific and the choice of which impeller to use in bioreactors to obtain enhanced performance is dependant on the applied criterion. None of the criterion favored the use of the standard Rushton turbine, therefore suggesting that there are strong grounds for retrofitting these impellers with either large diameter impellers of similar design or with novel agitators. In addition, fluid dynamic modeling of cavern formation has clearly highlighted the importance of a well mixed and oxygenated region for providing the capacity for high microbial oxygen uptake rates which govern Xanthan productivity and quality. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 95-108, 1998.
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    Microfabricated immunoisolating biocapsules (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 118-120 
    Details
    ISSN: 0006-3592
    Keywords: biocompatibility ; microfabrication ; biohybrid organs ; immunoisolation ; Islets of Langerhans ; silicon ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A microfabricated silicon-based biocapsule for the immunoisolation of cell transplants is presented. The biocapsule-forming process employs bulk micromachining to define cell-containing chambers within single crystalline silicon wafers. These chambers interface with the surrounding biological environment through polycrystalline silicon filter membranes. The membranes are surface micromachined to present a high density of uniform pores, thus affording sufficient permeability to oxygen, glucose, and insulin. The pore dimensions, as small as 20 nm, are designed to impede the passage of immune molecules and graft-borne viruses. The underlying filter-membrane nanotechnology has been successfully applied in controlled cell culture systems (Ferrari et al., 1995), and is under study for viral elimination in plasma fractionation protocols. Here we report the encouraging results of in vitro experiments investigating the biocompatibility of the microfabricated biocapsule, and demonstrate that encapsulated rat neonatal pancreatic islets significantly outlive and outperform controls in terms of insulin-secretion capability over periods of several weeks. These results appear to warrant further investigations on the potential of cell xenografts encapsulated within microfabricated, immunoisolating environments for the treatment of insulin-dependent diabetes. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 118-120, 1998.
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    Sucrose enhances the recovery and activity of ribonuclease A during reversed micelle extraction (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 374-379 
    Details
    ISSN: 0006-3592
    Keywords: reversed micelles ; ribonuclease A ; activity ; recovery ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: We have investigated the effect of two simple sugars, glucose and sucrose, on the extraction of ribonuclease A by AOT-isooctane reversed micelles. Including the sugars at concentrations up to 0.75 M in the feed solution resulted in moderate improvements in the forward transfer efficiency. The greatest effects were seen observed in the backward transfer step where both the protein recovery yield and the activity of the protein were greatly increased. Protein transfer and activity yields were also dependent on the AOT concentration. We suggest that the presence of sucrose, which was solubilized into the reversed micelles, results in preferential hydration of ribonuclease A, reducing the protein-surfactant interactions. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58:374-379, 1998.
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    Transition probability cell cycle model with product formation (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 387-399 
    Details
    ISSN: 0006-3592
    Keywords: population balance ; cell cycle ; hybridoma ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A cell cycle population model based on the transition probability model of Smith and Martin (1973) has been extended to include product synthesis and export. The model handles two probable mechanisms. In the direct production model, the product is the protein. In the transcription model, the product is the specific mRNA. The protein is synthesized by translation of the specific mRNA and subsequently exported. In either case, the cell density is jointly distributed in the primary product and maturity age in the cell cycle. This extended model also is capable of describing a large range of conditions, including substrate dependent batch and continuous cultures. With the use of unity maturity-velocity (but the transition rate a function of limiting substrate), the model is shown to exhibit a negative growth association between the specific productivity of monoclonal antibodies from hybridomas and the dilution rates of a chemostat. Possibilities of maturity age dependent transcription and translation are considered, and the results show that these features can amplify the specific productivity negative association with specific growth rate. While this model may provide a partial elucidation of monoclonal antibody productivity in a chemostat, the present work provides a proper framework with which probable cell cycle dependent product formation can be analyzed rigorously with a comprehensive computational model. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58:387-399, 1998.
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    Influence of biomass production and detachment forces on biofilm structures in a biofilm airlift suspension reactor (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 400-407 
    Details
    ISSN: 0006-3592
    Keywords: abrasion ; airlift reactor ; biofilm ; structure ; density ; surface shape ; thickness ; shear ; carrier concentration ; substrate loading ; detachment ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The influence of process conditions (substrate loading rate and detachment force) on the structure of biofilms grown on basalt particles in a Biofilm Airlift Suspension (BAS) reactor was studied. The structure of the biofilms (density, surface shape, and thickness) and microbial characteristics (biomass yield) were investigated at substrate loading rates of 5, 10, 15, and 20 kg COD/m3 · day with basalt concentrations of 60 g/L, 150 g/L, and 250 g/L. The basalt concentration determines the number of biofilm particles in steady state, which is the main determining factor for the biofilm detachment in these systems. In total, 12 experimental runs were performed. A high biofilm density (up to 67 g/L) and a high biomass concentration was observed at high detachment forces. The higher biomass content is associated with a lower biomass substrate loading rate and therefore with a lower biomass yield (from 0.4 down to 0.12 gbiomass/gacetate). Contrary to general beliefs, the observed biomass detachment decreased with increasing detachment force. In addition, smoother (fewer protuberances), denser and thinner compact biofilms were obtained when the biomass surface production rate decreased and/or the detachment force increased. These observations confirmed a hypothesis, postulated earlier by Van Loosdrecht et al. (1995b), that the balance between biofilm substrate surface loading (proportional to biomass surface production rate, when biomass yield is constant) and detachment force determines the biofilm structure. When detachment forces are relatively high only a patchy biofilm will develop, whereas at low detachment forces, the biofilm becomes highly heterogeneous with many pores and protuberances. With the right balance, smooth, dense and stable biofilms can be obtained. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58:400-407, 1998.
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    Protein sorption and recovery by hydrogels using principles of aqueous two-phase extraction (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 416-427 
    Details
    ISSN: 0006-3592
    Keywords: protein separation ; isolation and purification ; aqueous two-phase extraction ; hydrogels ; gels ; polymer solution thermodynamics ; partition coefficients ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Use of the thermodynamic principles of aqueous two-phase extraction (ATPE) to drive protein into a crosslinked gel is developed as a protein isolation and separation technique, and as a protein loading technique for drug delivery applications. A PEG/dextran gel system was chosen as a model system because PEG/dextran systems are widely used in aqueous two-phase extraction and dextran gels (Sephadex®) are common chromatographic media.The effects of polymer concentrations and molecular weights, salts, and pH on the partitioning of ovalbumin matched ATPE heuristics and data trends. Gel partition coefficients (Cgel/Csolution) increased with increasing PEG molecular weight and concentration and decreasing dextran concentration (increased gel swelling). The addition of PEG to the buffer solution yielded partition coefficients more than an order of magnitude greater than those obtained in systems with buffer alone, or added salt. A combined salt/PEG system yielded an additional order of magnitude increase. For example, when ovalbumin solution (2.3 mg/mL) was equilibrated with Sephadex® G-50 at pH 6.75, the partition coefficients were 0.13 in buffer, 0.11 in buffer with 0.22M KI, 2.3 in 12 wt% PEG-10,000 and 32.0 in 12 wt% PEG-10,000 with 0.22M KI. The effect of anions and cations as well as ionic strength and pH on the partitioning of ovalbumin also matched ATPE heuristics.Using the heuristics established above, partition coefficients as high as 80 for bovine serum albumin and protein recoveries over 90% were achieved. In addition, the wide range of partition coefficients that were obtained for different proteins suggests the potential of the technique for separating proteins. Also, ovalbumin sorption capacities in dextran were as high as 450 mg/g dry polymer, and the sorption isotherms were linear over a broad protein concentration range. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58:416-427, 1998.
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    Overexpression of a cytosolic chaperone to improve solubility and secretion of a recombinant IgG protein in insect cells (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 196-203 
    Details
    ISSN: 0006-3592
    Keywords: baculovirus ; chaperone ; hsp70 ; insect cell ; immunoglobulin ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The secretion of heterologous IgG proteins in the baculovirus-insect cell expression system is accompanied by substantial insoluble immunoglobulin in the infected cells. The accumulation of these insoluble forms suggests a limitation in the processing and secretory pathway of the infected cells. As a result, cytosolic hsp70 chaperones, which are known to associate and prevent aggregation of polypeptides in vitro, have been coexpressed in the infected cells. The hsp70 protein coprecipitated with the immunoglobulin to indicate the formation of a specific hsp70-immunoglobulin complex in vivo. Immunoblot and pulse chase studies indicated that coexpression of hsp70 increased intracellular immunoglobulin solubility. Metabolic labeling experiments revealed that hsp70 increased secreted immunoglobulin levels after several days infection as compared to infection with control baculoviruses. Pulse chase studies indicated that hsp70 increases the solubility of immunoglobulin precursors that are then processed and assembled into the complete antibody oligomer. A comparison of the action of cytosolic hsp70 chaperone to the endoplasmic reticulum chaperone BiP suggests sequential action in which hsp70 increases the solubility of preprocessed immunoglobulin, while BiP enhances the solubility of processed immunoglobulin chains. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58: 196-203, 1998.
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    Metabolic engineering of bacteria for ethanol production (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 204-214 
    Details
    ISSN: 0006-3592
    Keywords: ethanol ; lignocellulose ; fermentation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Technologies are available which will allow the conversion of lignocellulose into fuel ethanol using genetically engineered bacteria. Assembling these into a cost-effective process remains a challenge. Our work has focused primarily on the genetic engineering of enteric bacteria using a portable ethanol production pathway. Genes encoding Zymomonas mobilis pyruvate decarboxylase and alcohol dehydrogenase have been integrated into the chromosome of Escherichia coli B to produce strain KO11 for the fermentation of hemicellulose-derived syrups. This organism can efficiently ferment all hexose and pentose sugars present in the polymers of hemicellulose. Klebsiella oxytoca M5A1 has been genetically engineered in a similar manner to produce strain P2 for ethanol production from cellulose. This organism has the native ability to ferment cellobiose and cellotriose, eliminating the need for one class of cellulase enzymes. The optimal pH for cellulose fermentation with this organism (pH 5.0-5.5) is near that of fungal cellulases. The general approach for the genetic engineering of new biocatalysts has been most successful with enteric bacteria thus far. However, this approach may also prove useful with Gram-positive bacteria which have other important traits for lignocellulose conversion. Many opportunities remain for further improvements in the biomass to ethanol processes. These include the development of enzyme-based systems which eliminate the need for dilute acid hydrolysis or other pretreatments, improvements in existing pretreatments for enzymatic hydrolysis, process improvements to increase the effective use of cellulase and hemicellulase enzymes, improvements in rates of ethanol production, decreased nutrient costs, increases in ethanol concentrations achieved in biomass beers, increased resistance of the biocatalysts to lignocellulosic-derived toxins, etc. To be useful, each of these improvements must result in a decrease in the cost for ethanol production. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58:204-214, 1998.
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    Genetic manipulation of acid and solvent formation in Clostridium acetobutylicum ATCC 824 (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 215-221 
    Details
    ISSN: 0006-3592
    Keywords: butanol ; butyrate ; vector ; complementation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The genes coding for enzymes involved in butanol or butyrate formation were subcloned into a novel Escherichia coli-Clostridium acetobutylicum shuttle vector constructed from pIMP1 and a chloramphenicol acetyl transferase gene. The resulting replicative plasmids, referred to as pTHAAD (aldehyde/alcohol dehydrogenase) and pTHBUT (butyrate operon), were used to complement C. acetobutylicum mutant strains, in which genes encoding aldehyde/alcohol dehydrogenase (aad) or butyrate kinase (buk) had been inactivated by recombination with Emr constructs. Complementation of strain PJC4BK (buk mutant) with pTHBUT restored butyrate kinase activity and butyrate production during exponential growth. Complementation of strain PJC4AAD (aad mutant) with pTHAAD restored NAD(H)-dependent butanol dehydrogenase activity, NAD(H)-dependent butyraldehyde dehydrogenase activity and butanol production during solventogenic growth. The development of an alternative selectable marker makes it is possible to overexpress genes, via replicative plasmids, in mutant strains that lack specific enzyme activities, thereby expanding the number of possible genetic manipulations that can be performed in C. acetobutylicum. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58:215-221, 1998.
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    Engineering polyphosphate metabolism in Escherichia coli: Implications for bioremediation of inorganic contaminants (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 231-239 
    Details
    ISSN: 0006-3592
    Keywords: polyphosphate metabolism ; metabolic engineering ; Escherichia coli ; bioremediation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Polyphosphate metabolism plays an important role in the bioremediation of phosphate contamination in municiple wastewater, and may play a key role in heavy metal tolerance and bioremediation. However, little is known about the regulation of polyphosphate metabolism in microorganisms and its role in heavy metal toxicity. We have manipulated polyphosphate metabolism in Escherichia coli by overexpressing the genes for polyphosphate kinase (ppk) and for polyphosphatase (ppx) under control of their native promoters and inducible promoters. Overexpression of ppk results in high levels of intracellular polyphosphate, improved phosphate uptake, but no increase in tolerance to heavy metals. Overexpression of both ppk and ppx results in lower levels of intracellular polyphosphate, secretion of phosphate from the cell, and increased tolerance to heavy metals. Metabolic flux analysis indicates that the cell responds to increased flux through the PPK-PPX pathway by altering flux through the TCA cycle. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58:231-239, 1998.
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    Enhanced TGFβ1 maturation in high five cells coinfected with recombinant baculovirus encoding the convertase furin/pace: Improved technology for the production of recombinant proproteins in insect cells (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 85-91 
    Details
    ISSN: 0006-3592
    Keywords: furin ; proprotein convertases ; transforming growth factor beta ; baculovirus ; precursor proteins ; overexpression systems ; growth factors ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: One important limitation of the widely used insect baculovirus overexpression system is its inefficiency to properly process heterologous proteins which are initially biosynthesized as larger inactive precursor proteins. One example is transforming growth factor beta 1 (TGFβ1), a 25-kDa homodimeric protein with pleiotropic functions. As many growth factors, the inactive TGFβ1 precursor molecule needs to be proteolytically cleaved C-terminal to a basic sequence to yield the mature and active homodimer. In insect cells, a large proportion of overexpressed TGFβ1 was found in an inactive precursor form suggesting that the levels of endogenous convertases are limiting for the production of mature and bioactive TGFβ1 in this system. We have demonstrated that furin, a member of a novel family of mammalian prohormone convertases (PCs) can efficiently process TGFβ1 precursor resulting in the production of the mature and active growth factor. Taking advantage of this observation, we have developed an improved overproduction system for TGFβ1 by coexpressing prohTGFβ1 and human furin convertase in High Five cells. Using this system, the production of mature active TGFβ1 increased in a dose-dependent fashion reaching up to 7.8-fold the amount obtained with the growth factor only. Thus, eliminating the rate-limiting step in recombinant TGFβ1 production maximizes its processing efficiency and the yield of the mature active growth factor. Such simple and efficient technology could be useful for large scale production of other proproteins which undergo similar maturation processes and share furin recognition sequences at the junction between the proregion and the mature polypeptide. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58:85-91, 1998.
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    Chemically stabilized trypsin used in dipeptide synthesis (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 366-373 
    Details
    ISSN: 0006-3592
    Keywords: trypsin ; stabilization ; peptide synthesis ; organic solvents ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Bovine pancreatic trypsin was treated with ethylene glycol bis(succinic acid N-hydroxysuccinimide ester). Approximately 8 of 14 lysines per trypsin molecule were modified. This derivative (EG trypsin) was more stable than native between 30° and 70°C: T50 values were 59°C and 46°C, respective. EG trypsin's half-life of 25 min at 55°C was fivefold greater than native's. EG trypsin had a decreased rate of autolysis and retained more activity in aqueous mixtures of 1,4-dioxan, dimethylformamide, dimethylsulfoxide, and acetonitrile. EG trypsin had lower Km values for both amide and ester substrates; its kcat values for two amides (benzoyl-l-arginine p-nitroanilide and benzyloxycarbonyl glycyl-glycyl-arginyl-7-amino-4-methyl coumarin) increased, whereas its kcat value for an ester (thiobenzoyl benzoyloxycarbonyl-l-lysinate) decreased slightly. The specific activity (kcat/Km) of EG trypsin was increased for both amide and ester substrates. EG trypsin gave higher yields and reaction rates than native in kinetically controlled synthesis of benzoyl argininyl-leucinamide in acetonitrile and in t-butanol. Highest peptide yields occurred with EG trypsin in 95% acetonitrile, where 90% of the substrate was converted to product. No peptide synthesis occurred in 95% DMF with either form of trypsin. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58:366-373, 1998.
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    Deactivation and conformational changes of cutinase in reverse micelles (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 380-386 
    Details
    ISSN: 0006-3592
    Keywords: reverse micelles ; cutinase ; deactivation ; conformational changes ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Deactivation data and fluorescence intensity changes were used to probe functional and structural stability of cutinase in reverse micelles. A fast deactivation of cutinase in anionic (AOT) reverse micelles occurs due to a reversible denaturation process. The deactivation and denaturation of cutinase is slower in small cationic (CTAB/1-hexanol) reverse micelles and does not occur when the size of the cationic reverse micellar water-pool is larger than cutinase. In both systems, activity loss and denaturation are coupled processes showing the same trend with time. Denaturation is probably caused by the interaction between the enzyme and the surfactant interface of the reversed micelle. When the size of the empty reversed micelle water-pool is smaller than cutinase (at W0 5, with W0 being the water:surfactant concentration ratio) a three-state model describes denaturation and deactivation with an intermediate conformational state existing on the path from native to denaturated cutinase. This intermediate was clearly detected by an increase in activity and shows only minor conformational changes relative to the native state. At W0 20, the size of the empty water-pool was larger than cutinase and the data was well described by a two-state model for both anionic and cationic reverse micelles. For AOT reverse micelles at W0 20, the intermediate state became a transient state and the deactivation and denaturation were described by a two-state model in which only native and denaturated cutinase were present. For CTAB/1-hexanol reverse micelles at W0 20, the native cutinase was in equilibrium with an intermediate state, which did not suffer denaturation. 1-Hexanol showed a stabilizing effect on cutinase in reverse micelles, contributing to the higher stabilities observed in the cationic CTAB/1-hexanol reverse micelles. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58:380-386, 1998.
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    Increase of xylitol production rate by controlling redox potential in Candida parapsilosis (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 440-444 
    Details
    ISSN: 0006-3592
    Keywords: xylitol production ; redox potential ; dissolved oxygen ; Candida parapsilosis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effect of redox potential on xylitol production by Candida parapsilosis was investigated. The redox potential was found to be useful for monitoring the dissolved oxygen (DO) level in culture media, especially when the DO level was low. An increase in the agitation speed in a 5 L fermentor resulted in an increased culture redox potential as well as enhanced cell growth. Production of xylitol was maximized at a redox potential of 100 mV. As the initial cell concentration increased from 8 g/L to 30 g/L, the volumetric productivity of xylitol increased from 1.38 g/L · h to 4.62 g/L · h. A two-stage xylitol production strategy was devised, with stage 1 involving rapid production of cells under well-aerated conditions, and stage 2 involving cultivation with reduced aeration such that the culture redox potential was 100 mV. Using this technique, a final xylitol concentration of 180 g/L was obtained from a culture medium totally containing 254.5 g/L xylose in a 3,000 L pilot scale fermentor after 77 h fermentation. The volumetric productivity of xylitol during the fermentation was 2.34 g/L · h. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58:440-444, 1998.
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    Systematic errors in data evaluation due to ethanol stripping and water vaporization (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 428-439 
    Details
    ISSN: 0006-3592
    Keywords: water vaporization ; ethanol stripping ; condensation ; absorption ; elemental recoveries ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Systematic errors due to the neglect of water and/or ethanol partition between liquid and gaseous phases are discussed for bioreactors equipped with or without a condenser. Both water vapor and ethanol vapor are present in the off-gas leaving the condenser. Presence of residual water vapor largely influences the gas measurements by dilution. As a consequence, the oxygen consumption rate can be overestimated by a factor of 3 if calculations are not corrected for water vapor content or if no additional device is implemented after the condenser to completely dry the off-gases. The mass balance and partition equations predict that the condenser has only a small effect on reduction of the ethanol vapor content of the off-gas. The reason is the high ethanol concentration of the condensate droplets on the condenser wall in contact with the off-gases. Model predictions as well as experimental results show that ethanol evaporation represents a large fraction of the ethanol production rate and influences greatly the elemental recoveries. For a reactor working at 30°C without condensation of the vapors and for a volumetric aeration rate of 0.63vvm, stripping of ethanol resulted in a gaseous dilution rate of 0.016 h-1 for ethanol. The dilution rate by stripping was reduced to 0.014 h-1 when a condenser at 12°C was implemented. The fraction of ethanol that is stripped is mainly dependent on the ratio D/vvm (liquid to gaseous flow rates), and the effect is only slightly influenced by low condenser temperature. The evaporation of ethanol may account for more than 20% of the ethanol formation rate. Therefore, the condenser does not succeed to reflux all ethanol to the reactor broth. In terms of a unit operation, ethanol vapor can be efficiently reduced by absorption instead of condensation. To demonstrate the feasibility, a simple modification of the reactor was tested for continuous cultures: the feed port was changed from the top-plate to the top of the condenser, which was used as an absorption column. Ethanol stripping was reduced by a factor of 4 as compared to the condensation setup (at 12°C): it accounted for 2% of the ethanol production rate as compared to 8.2% at D = 0.19 h-1 and 0.63vvm. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58:428-439, 1998.
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    Protein-protein and protein-salt interactions in aqueous protein solutions containing concentrated electrolytes (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 451-451 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: No abstract.
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    Intrinsic kinetic parameters of the pellet forming fungus Aspergillus awamori (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 478-485 
    Details
    ISSN: 0006-3592
    Keywords: Aspergillus awamori ; intrinsic kinetic parameters ; oxygen concentration profiles ; oxygen microelectrode ; immobilisation ; pellet formation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Fungi like Aspergillus awamori may spontaneously form pellets, which introduces an extra oxygen transfer resistance and influences the activity of the microorganism. Consequently, dramatic variations of apparent kinetics are reported in literature, due to variations in culture conditions, e.g., oxygen bulk concentration and pellet morphology. True intrinsic growth parameters like maximum growth rate and biomass yield, are important for process modelling and design. Values for these parameters may be obtained from observed kinetics by properly accounting for the anaerobic activity of the fungus. The true aerobic carbon yield for A. awamori of 0.6 mol Cx/mol Cs could be determined from the observed biomass yield after macroscopic monitoring of the anaerobic activity, and correction for the ethanol production by the fungal pellets. The true maximum growth rate was obtained from artificially immobilised A. awamori. In such well-defined system, transport is only diffusive and the morphology is not influenced by the stirring conditions. A maximum growth rate of 0.4 h-1 at pH 4.5 could be established in gel beads after microscopic monitoring of the oxygen penetration with microelectrodes. The developing biomass concentration profiles in these beads may be inferred from an adequate theoretical description of the oxygen profiles in course of time. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58: 478-485, 1998.
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    Specific heat flow rate: An on-line monitor and potential control variable of specific metabolic rate in animal cell culture that combines microcalorimetry with dielectric spectroscopy (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 464-477 
    Details
    ISSN: 0006-3592
    Keywords: specific metabolic rate ; calorimetry ; capacitance ; metabolic activity ; on-line biosensor ; animal cell culture ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: One of the requirements for enhanced productivity by the animal culture systems used in biotechnology is the direct assessment of the metabolic rate by on-line biosensors. Based on the fact that cell growth is associated with an enthalpy change, it is shown that the specific heat flow rate is stoichiometrically related to the net specific rates of substrates, products, and indeed to specific growth rate, and therefore a direct reflection of metabolic rate. Heat flow rate measured by conduction calorimetry has a technical advantage over estimates for many material flows which require assays at a minimum of two discrete times to give the rate. In order to make heat flow rate specific to the amount of the living cellular system, it would be advantageous to divide it by viable biomass. This requirement has been fulfilled by combining a continuous flow microcalorimeter ex situ with a dielectric spectroscope in situ, the latter measuring the viable cell mass volume fraction. The quality of the resulting biosensor for specific heat flow rate was illustrated using batch cultures of Chinese hamster ovary cells (CHO 320) producing recombinant human interferon-γ (IFN-γ) during growth in a stirred tank bioreactor under fully aerobic conditions. The measuring scatter of the probe was decreased significantly by applying the moving average technique to the two participant signals.It was demonstrated that the total metabolic rate of the cells, as indicated by the specific heat flow rate sensor, decreased with increasing time in batch culture, coincident with the decline in the two major substrates, glucose and glutamine, and the accumulation of the by-products, ammonia and lactate. Furthermore, the specific heat flow rate was an earlier indicator of substrate depletion than the flow rate alone. The calorimetric-respirometric ratio showed the intensive participation of anaerobic processes during growth and the related IFN-γ production. Specific heat flow rate was monotonically related to specific cell growth rate and associated with specific IFN-γ production. Specific heat flow rate is potentially a valid control variable for the growth of genetically engineered cell lines producing target proteins. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58: 464-477, 1998.
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    Removal of nitrate from industrial wastewaters in a pilot plant by nitrate-tolerant Klebsiella oxytoca CECT 4460 and Arthrobacter globiformis CECT 4500 (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 510-514 
    Details
    ISSN: 0006-3592
    Keywords: nitrate removal ; Klebsiella oxytoca ; Arthrobacter globiformis ; dinitroethylene glycol ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Two strains, a gram-negative bacterium Klebsiella oxytoca CECT 4460 and a gram-positive, mycelium-forming bacterium Arthrobacter globiformis CECT 4500, tolerant to up to 1 M nitrate, were isolated from the grounds of a munitions factory. Under strict aerobic conditions and with appropriate C-sources, growth of these bacteria took place when the nitrate concentration in the medium was below 150 mM. Optimal growth conditions regarding the culture medium composition for the biological removal of nitrate were established in batch cultures. Then, the system was scaled up to a 40-L pilot plant and operated under continuous conditions in a factory with direct waste streams from dinitroethylene glycol production after appropriate dilution with nontreated groundwaters. The level of nitrate in the effluent was below 0.5% of the initial N-load. Nitrite and ammonium were undetectable and the level of the C-source in the effluent was below 50 mg per L. On the basis of these results, we conclude that the system worked on site satisfactorily. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58: 510-514, 1998.
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    A novel biotinylated degradable polymer for cell-interactive applications (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 529-535 
    Details
    ISSN: 0006-3592
    Keywords: drug delivery ; tissue engineering ; surface modification ; polymer ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: We describe the development of a novel biodegradable polymer designed to present bioactive motifs at the surfaces of materials of any architecture. The polymer is a block copolymer of biotinylated poly(ethylene glycol) (PEG) with poly(lactic acid) (PLA); it utilizes the high-affinity coupling of the biotin-avidin system to undergo postfabrication surface engineering. We show, using surface plasmon resonance analysis (SPR) and confocal microscopy that surface engineering can be achieved under aqueous conditions in short time periods. These surfaces interact with cell surface molecules and generate beneficial responses as demonstrated by the model study of integrin-mediated spreading of endothelial cells on polymer surfaces presenting RGD peptide adhesion sequences. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58: 529-535, 1998.
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    On-line study of fungal morphology during submerged growth in a small flow-through cell (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 541-553 
    Details
    ISSN: 0006-3592
    Keywords: fungal morphology ; Aspergillus oryzae ; on-line image analysis ; growth kinetics and branching pattern ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A flow-through cell is designed to measure the growth kinetics of hyphae of Aspergillus oryzae grown submerged in a well controlled environment. The different stages of the growth process are characterized, from the spore to the fully developed hyphal element with up to 60 branches and a total length lt up to 10,000 μm. Spore swelling is found to occur without change in the form of the spore (circularity index constant at about 1.06) and the spore volume probably increases exponentially. The germ tube appears after about 4 h. The branching frequency and the rate of germ tube extension is determined. After about 10 h growth at a glucose concentration of 250 mg L-1, 6-7 branches have been set, and both the total hyphal length lt and the number of tips increase exponentially with time. The specific growth rate of the hyphae is 0.33 h-1 while the average rate of the extension of the growing tips approaches 55 μm h-1.The growth kinetics for all the branches on the main hypha have also been found. The main hypha and all the branches grow at a rate which can be modeled by saturation kinetics with respect to the branch length and with nearly equal final tip speeds (160 μm h-1). Branches set near the apical tip of the main hypha attain their final tip speed in the shortest time, i.e., the value of the saturation parameter is small.Finally, the influence of substrate (glucose) concentration cs on the values of the morphological parameters has been determined. It is found that saturation type kinetics can be used to describe the influence of cs on the growth.Experiments with recirculation of effluent from the cell back to the inlet strongly suggest that the fungus secretes an inducer for growth and branching. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58: 541-553, 1998.
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    Production of lycopene by the food yeast, Candida utilis that does not naturally synthesize carotenoid (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 306-308 
    Details
    ISSN: 0006-3592
    Keywords: lycopene ; Candida utilis ; carotenoids ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The Erwinia uredovora crtE, crtB, and crtI genes, which are responsible for the synthesis of carotenoid lycopene from farnesyl pyrophosphate, were expressed in Candida utilis under the control of the promoters and terminators derived from the C. utilis GAP, PGK, and PMA genes, respectively. The yeast transformant carrying the carotenoid biosynthesis genes produced 758 μg/g dry weight of lycopene along with 407 μg/g dry weight of phytoene in the stationary phase. It was observed in the C. utilis transformant that ergosterol content was decreased to 65% of that in the parent strain that accumulated 6.04 mg/g dry weight of ergosterol. It is therefore possible that the carbon flux for the ergosterol biosynthesis has been branched at farnesyl pyrophosphate to generate a new pathway for the lycopene production in this yeast transformant. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58:306-308, 1998.
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    Elemental balancing of biomass and medium composition enhances growth capacity in high-density Chlorella vulgaris cultures (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 605-611 
    Details
    ISSN: 0006-3592
    Keywords: Chlorella vulgaris ; algae ; elemental balancing ; medium design ; high-density cultures ; photoautotrophic growth ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The basic requirements for high-density photoautotrophic microalgal cultures in enclosed photobioreactors are a powerful light source and proper distribution of light, efficient gas exchange, and suitable medium composition. This article introduces the concept of balancing the elemental composition of growth medium with biomass composition to obtain high-density cultures. N-8 medium, commonly used for culturing Chlorella vulgaris was evaluated for its capacity to support high-density cultures on the basis of elemental stoichiometric composition of C. vulgaris. This analysis showed that the N-8 medium is deficient in iron, magnesium, sulfur, and nitrogen at high cell densities. N-8 medium was redesigned to contain stoichiometrically balanced quantities of the four deficient elements to support a biomass concentration of 2% (v/v). The redesigned medium, called M-8 medium, resulted in up to three- to fivefold increase in total chlorophyll content per volume of culture as compared to N-8 medium. Further experiments showed that addition of each of the four elements separately to N-8 medium did not improve culture performance and that balanced supplementation of all four deficient elements was required to yield the improved performance. Long-term (24 d) C. vulgaris culture in M-8 medium showed continuous increase in chlorophyll content and biomass throughout the period of cultivation. In contrast, the increase in chlorophyll content and biomass ceased after 7 and 12 d, respectively in N-8 medium, demonstrating the higher capacity of M-8 medium to produce biomass. Thus, the performance of high cell density photobioreactors can be significantly enhanced by proper medium design. The elemental composition of the biomass generated is an appropriate basis for medium design. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59:605-611, 1998.
    Additional Material: 3 Ill.
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