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  • 1
    Electronic Resource
    Electronic Resource
    Excimer fluorescence of (+)-anti-benzo (a)pyrene diol epoxide covalently bound to poly (dG-dC): Structural implications (1990)
    New York : Wiley-Blackwell
    Biopolymers 29 (1990), S. 1249-1260 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Fluorescence of (+)-anti-benzo (a) pyrene diol epoxide [(+)-anti-BPDE] covalently bound to poly (dG-dC) has been studied with steady-state and time-resolved techniques. Extensive formation of excimers is found, even at small (0.008) BPDE/nucleotide ratios. This indicates favored covalent binding to bases close to already modified guanines. Both fluorescence excitation spectra and lifetime measurements reveal two populations of (+)-anti-BPDE adducts: one that can form excimers and one that cannot. Three excimer lifetimes (4.5, 29, and 83 ns) are observed. Differently shifted monomer and excimer excitation spectra are discussed in terms of pyrene-pyrene exciton interactions, consistent with a distance shorter than 7 Å between the excimer-forming BPDE chromophores.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360290814
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  • 2
    Electronic Resource
    Electronic Resource
    A molecular dynamics study of conformational changes and hydration of left-handed d (CGCGCGCGCGCG)2 in a nonsalt solution (1992)
    New York : Wiley-Blackwell
    Biopolymers 32 (1992), S. 1035-1059 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Twelve dinucleotides (one complete turn) of left-handed, flexible, double-helix poly(dG- dC) Z-DNA have been simulated in aqueous solution with K+ counterions for 70 ps. Most of the d(GpC) phosphates have rotated in accordance with a ZI → ZII transition. The ZII conformation was probably partly stabilized by counterions, which coordinate one of the anionic oxygens and the guanine-N7 of the next (5′ → 3′ direction) base. The presence of base-coordinating ions close to the helical axis rotated and pulled about half of the d (CpG) phosphates further into the groove. These ions also gave rise to rather large deviations from the crystal structure (ZI) with their tendency of pulling the bases closer toward the helical axis. A flipping of the orientation about the glycosyl bond from the +sc to the -sc region was observed for one guanosine, also leading to deviations from the crystal structure. Many bridges containing one or two water molecules were found, with a dominance for the latter. They essentially formed a network of intra- and interstrand bridges between anionic and esterified phosphate oxygens. A “spine” of water molecules could be distinguished as a dark zig-zag pattern in the water density map. The lifetime of a bridge containing one water was about twice as long as that of a two-water bridge and it lasted 5-15 times longer than a hydrogen bond in water. The lifetimes were also calculated for a selection of bridge types, in order of decreasing stability: O1P/O2P… W…O′4 ≫ O1P/O2P… W… guanine-N2 〉 O1P/O2P… W…O1P/O2P. The reorientational motion of water molecules in the first hydration shell around selected groups was slowed down considerably compared to bulk water and the decreasing order of correlation times was guanine-N2 〉 O′4 〉 O′3/ O′5 〉 O1P/O2P. © 1992 John Wiley & Sons, Inc.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360320814
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  • 3
    Electronic Resource
    Electronic Resource
    Li+ counterion self-diffusion in ordered DNA (1994)
    New York : Wiley-Blackwell
    Biopolymers 34 (1994), S. 1605-1614 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The anisotropic self-diffusion coefficient of 7Li+ (I = 3/2) counterions has been studied in hydrated, macroscopically oriented Li-(B)DNA fibers at relatively high water contents, corresponding to approximate DNA-DNA helix axis distances of 22-35 Å, using the pulsed field gradient hmr spin-echo method. Self-diffusion coefficients parallel (D∥) and perpendicular (D⊥) to the DNA helix axis increase with increasing salt content and with increasing DNA-DNA helix axis distance. The observed anisotropy D∥/D⊥ decreases from 1.6 to 1.2 with the DNA-DNA separation increasing from 22 to 35 Å in the salt-free sample. This result can be understood by the obstruction effect caused by the DNA molecules themselves. The values of the Li+ self-diffusion coefficients in the most water-rich system with no added salt (corresponding to an approximate distance of 35 Å between the DNA helix axes) were D∥ ∼ 1.15 × 10-10 m2 s-1 and D⊥ ∼ 0.98 × 10-10 m2 s-1, compared to 9.14 × 10-10 m2 s-1 for the diffusion of Li+ in an aqueous solution of LiCl (∼ 2.1M). The possible occurrence of restriction effects in the DNA fibers have also been studied by determining the self-diffusion coefficient at different effective diffusion times. The self-diffusion coefficient of Li+ in the sample with the largest DNA-DNA helix axis distance seems to be independent of the effective diffusion time, which indicates that the lithium ions are not trapped within impermeable barriers. The possibility of diffusion through permeable barriers has also been investigated, and is discussed. © 1994 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360341205
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  • 4
    Electronic Resource
    Electronic Resource
    Z → B transition in poly[d(G-m5C)2] induced by interaction with 4′,6-diamidino-2-phenylindole (1993)
    New York : Wiley-Blackwell
    Biopolymers 33 (1993), S. 1677-1686 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Z form of poly[d(G-m5C)2], in presence of Mg2+ ion, is found to be transformed into B form upon interaction with 4′,6-diamidino-2-phenylindole (DAPI). The Z → B transformation is complete at a mixing ratio of about 0.07 DAPI per DNA base pairs, i.e., each DAPI molecule may be related to the conversion of 6-7 base pairs. An interaction between DAPI and poly[d(G-m5C)2] in its Z form at low drug: DNA ratios is suggested from optical dichroism and time-resolved luminescence anisotropy results. The spectroscopic behaviour of DAPI indicates that the Z conformation of DNA does not provide normal binding sites for DAPI, such as groove or intercalation sites, but that the initial association may be of external nature. © 1993 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360331105
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  • 5
    Electronic Resource
    Electronic Resource
    Studies of growth conditions in wood for three white-rot fungi and their cellulaseless mutants (1980)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 22 (1980), S. 363-376 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: White-rot fungi, which have the ability to degrade all the wood components including lignin, are of great interest in biotechnological processes based on wood and other lignocellulosic materials. It was demonstrated earlier that enough lignin can be degraded to cause a decrease in the energy demand for production of thermomechanical pulp if wood chips are pretreated by cellulaseless mutants of white-rot fungi. This paper concerns the growth conditions in wood for three white-rot fungi and their cellulaseless mutants in order to determine optimal conditions for such pretreatment processes. The pH and temperature optima have been determined as well as the growth rate in wood. The results show that the growth rate in wood. at least for Cel 44 (a cellulaseless mutant of Sporotrichum pulverulentum), is not the rate-limiting step in delignification. From different mixtures of urea and NH4H2PO4 the optimal nitrogen source was determined for the mutants. The optimal C/N ratio was found to vary between 160/1 and 400/1. It is suggested that the lower the C/N ratio, the faster the growth. It was also demonstrated that both water- and acetone-extractable substances in wood supported the growth of cellulaseless mutants. When some glucose was added to the wood, the weight loss caused by Cel 44 increased. All these observations support earlier findings that lignin in wood cannot be degraded by white-rot fungi unless a more easily metabolizable carbon source is used simultaneously.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260220210
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  • 6
    Electronic Resource
    Electronic Resource
    Fermentation of waste mechanical fibers from a newsprint mill by the rot fungus Sporotrichum pulverulentum (1975)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 17 (1975), S. 327-348 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The growth and protein production of Sporotrichum pulverulentum, formerly called Chrysosporium lignorum, have been studied in submerged cultures using lignin-containing waste fibers from a newsprint mill as the only carbon source. The influence of different nitrogen sources on the growth parameters has been particularly investigated. The regulation of the production of extracellular enzymes and their interaction with the fibers is discussed. Experiments with cellulose of different degrees of polymerization and crystallinities showed that the protein content in the residual substance decreased, particularly when the crystallinity increased. When the highly crystalline powder cellulose was used as carbon source, the protein content in the residual substance was only 6% and with the mechanical waste fibers 14%. The results obtained demonstrate that the more complex the carbon source the more difficult it is to digest and the more enzyme has to be produced for its degradation. This puts a heavy burden on the protein synthesizing mechanism. Utilizing results from other work, where the endo- and exo-l, 4-β-glucanases produced by S. pulverulentum for the degradation of cellulose have been quantitatively purified, it has been calculated that the extracellular enzymes under these conditions can together account for approximately 30% of the protein in the mycelium. The endo- and exo-1,4-β-glucanases account for up to 55% of the extracellular protein.Certain possibilities of producing a final product with a high protein content using complex carbon sources are also mentioned.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260170304
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  • 7
    Electronic Resource
    Electronic Resource
    Enzyme mechanisms involved in cellulose hydrolysis by the rot fungus Sporotrichum pulverulentum (1978)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 20 (1978), S. 317-332 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This article presents a review of the enzyme mechanisms involved in degradation of cellulose by the white-rot fungus Sporotrichum poulverulentum. The hydrolytic enzymes involved include: (1) five endo-1,4-β-glucanases; (2) one exo-1,4-β-glucanase, and (3) one or several 1,4-β-glucosidases. A recently discovered oxidative enzyme of importance in in vitro cellulose degradation seems to be a cellobiose oxidase. An oxidoreductase, cellobiose:quinone oxidoreductase, is of importance both in cellulose and in lignin degradation. Regulatory mechanisms of the extracellular enzyme activities, such as monosugar levels causing catabolite repression of the endoglucanases, have also been investigated. The enzymes used by S. pulverulentum in cellulose hydrolysis are compared to those used by Trichoderma viride. Very similar types of enzymes are used in both cases. However, no oxidative enzyme has so far been found to be involved in extracellular cellulose degradation in the case of T. viride. Recommendations for further research are given.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260200302
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  • 8
    Electronic Resource
    Electronic Resource
    Nutritional evaluation of the white-rot fungus Sporotrichum pulverulentum as a feedstuff to rats, pigs, and sheep (1980)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 22 (1980), S. 2285-2303 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The production of single-cell protein (SCP) based on cheap carbon sources such as spent liquor from paper mills is of interest for different reasons. The White-rot fungus (Sporotrichum pulverulentum) has earlier been shown to degrade cellulose and lignin. The nutritive value of this fungus was investigated with rats, pigs, and sheep. The effect of different drying process was evaluated on rats. Experiments with piglets, growing pigs, and sheep were aimed at getting primary information on nutritive parameters with domestic animal species, Chemical analysis of S. pulverulentum showed that the sum of the amino acids corresponded to 70% and ammonia, GABA, and glucosamine to 20% of its crude protein content. Differences between drying treatments in their effect on protein digestibility were not noted. From a protein quality viewpoint, a tendency toward superiority was noted for two of the drying processes. The amino acid digestibility of S. pulverulentum was inferior to values for soybean oil meal given in textbooks. The piglet experiment confirmed the lower nutritive value of S. pulverulentum compared with soybean oil meal. in the piglet stage a content of metabolizable energy of S. pulverulentum was found which corresponded to 60% of that for soybean oil meal. With increasing age the ability of pigs to utilize the fungus increased. The limited nutritive value for monogastric animals is most certainly caused by the cell-wall structure of S. pulverulentum with poor digestibility of the carbohydrates. The experiment with sheep showed more satisfactory results than with monogastric species, with digestibility of crude protein of 82% and a content of metabolizable energy of 70% of soybean oil meal.
    Additional Material: 9 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260221107
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  • 9
    Electronic Resource
    Electronic Resource
    Enzymic hydrolysis of lignocellulosic materials: I. Models for the hydrolysis process  -  a theoretical study (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 135-138 
    Details
    ISSN: 0006-3592
    Keywords: enzymic hydrolysis ; enzyme recovery ; process models ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: At the end of an enzymic hydrolysis process involving a solid lignocellulosic substrate, enzymes are found both in solution and absorbed to the substrate residue. Removal of residue from the system will result in loss of some of the enzymes, the extent of which will depend on the design of the process. To minimize enzyme loss, a study has been conducted in which six process models have been formulated and an enzyme loss function derived for each model based on the total amount of enzymes lost through residue removal. Model 1 is a reference model, characterized by an uninterrupted hydrolysis throughout the entire hydrolysis period. The residue is then washed in order to recover both sugar and adsorbed enzymes before the residue is discarded. Models 2-6 are all characterized by the removal of hydrolysate three times during the process, recirculation of dissolved and adsorbed enzymes to various points in the process and selection of a stage at which the residue is removed. The following conclusions could be drawn from the derived enzyme loss functions: Increased enzyme adsorption leads to increased enzyme loss.The enzyme loss decreases if the solid residue is removed late in the process.Both adsorbed and dissolved enzymes should be introduced at the starting point of the process. This is particularly important for dissolved enzymes. Three models were chosen for experimental studies, which are reported in a second, accompanying article. The experimental results obtained are compared with the theoretical study reported here.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260380205
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  • 10
    Electronic Resource
    Electronic Resource
    Enzymic saccharification of pretreated wheat straw (1985)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 27 (1985), S. 650-659 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Studies of pretreatment of wheat and its subsequent saccharification by Trichoderma reesei cellulases are reported. Steam explosion was found to be the most effective of the pretreatment methods tested. Data are presented describing the effect of enzyme and substrate concentration on the rate and degree of hydrolysis. Significant inhibition of the cellulases was observed when sugar concentrations were 6% or higher. This inhibition increased when glucose and ethanol were present simultaneously. Adsorption of enzymes to the substrate was followed during a 24-h hydrolysis period. An initial rapid and extensive adsorption occurred, followed by a short desorption period that was followed in turn by a further increased adsorption peaking after 3 h. Intermediate removal of hydrolysate, particularly in combination with a second addition of enzyme, clearly improved the yield of saccharification compared to an uninterrupted hydrolysis over a 24-h period. Thus, a 74% yield of reducing sugars was obtained. Furthermore, an increase in the amount of recoverable enzymes was observed under these conditions. Evidence is presented that suggests that a countercurrent technique, whereby free enzymes in recovered hydrolysate are adsorbed onto new substrate, may provide a means of recirculating dissolved enzymes.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260270515
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