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  • Chemistry  (7.254)
  • General Chemistry  (879)
  • Inorganic Chemistry  (785)
  • Aerodynamics
  • Triticum aestivum
  • 1985-1989  (7.285)
  • 1950-1954
  • 1940-1944
  • 1935-1939
  • 1985  (7.285)
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  • 1985-1989  (7.285)
  • 1950-1954
  • 1940-1944
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  • 1
    ISSN: 1432-0789
    Schlagwort(e): Rhizosphere bacteria ; Nitrogenase activity ; Triticum aestivum ; Inoculation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Wheat seedlings were inoculated with rhizosphere nitrogen-fixing bacteria and grown gnotobiotically for 15 days. The growth medium consisted of semisolid agar with or without plant nutrients. The bacteria, isolated from roots of field-grown wheat, were three unidentified Gram-negative rods (A1, A2, E1), one Enterobacter agglomerans (C1) and two Bacillus polymyxa (B1, B2). A strain of Azospirillum brasilense (USA 10) was included for comparison. Nitrogenase activity (acetylene reduction activity, ARA) was tested on intact plants after 8 and 15 days of growth. In semisolid agar without plant nutrients, five isolates showed ARA of 0.01–0.9 nmol C2H4 plant−1 h−1, while the two strains of B. polymyxa had higher ARA of 3.3–10.6 nmol C2H4 plant−1 h−1. Plant development was not affected by inoculation with bacteria, except that inoculation with B. polymyxa resulted in shorter shoots and lower root weight. Transmission electronmicroscopy of roots revealed different degrees of infection. A. brasilense, A1 and A2, occurred mainly in the mucilage on the root surface and between outer epidermal cells (low infectivity). B. polymyxa strains and E1 were found in and between epidermal cells (intermediate infectivity) while E. agglomerans invaded the cortex and was occasionally found within the stele (high infectivity).
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 71 (1985), S. 31-38 
    ISSN: 1432-2242
    Schlagwort(e): Triticum aestivum ; 2D electrophoresis ; Gene localization ; Homoeologous genes ; Genetic regulation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Among the 782 spots observed in two-dimensional gel electrophoresis of denatured proteins from etiolated wheat shoots, 185 were found to be variable between the euploid and 26 ditelosomic lines of ‘Chinese Spring’. Thirty-five structural genes were located on 17 chromosome arms. Numerous intensity changes showing alterations in protein levels were observed and led to the following statements: 1) regulators are frequently found and can be assigned for a same polypeptide to various chromosome arms; 2) for most polypeptides homoeologous arms do not manifest similar effects; 3) nevertheless, when affecting the same polypeptide, homoeologous arms display in most cases identical regulatory effects; 4) gene dosage compensation is observed in only one out of four homoeoallelic situations.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    ISSN: 1432-2242
    Schlagwort(e): Intrachromosomal mapping ; Nucleolar organiser region ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Restriction enzyme digestion of the ribosomal RNA genes of the nucleolar organisers of wheat has revealed fragment length polymorphisms for the nucleolar organiser on chromosome 1B and the nucleolar organiser on 6B. Variation between genotypes for these regions has also been demonstrated. This variation has been exploited to determine the recombination frequency between the physically defined nucleolar organiser on 1B (designatedNor1) and other markers; two loci,Glu-B1 andGli-B1 which code for endosperm storage proteins andRf3, a locus restoring fertility to male sterility conditioned byT. timopheevi cytoplasm.Gli-B1 andRf3 were located on the short-arm satellite but recombine with the nucleolar organiser giving a gene order ofNor1 — Rf3 — Gli-B1. Glu-B1 is located on the long arm of 1B but shows relatively little recombination withNor1, which is, in physical distance, distal on the short arm. This illustrates the discrepancy between map distance and physical distance on wheat chromosomes due to the distal localisation of chiasmata. The recombination betweenNor1 andRf3 indicates that, contrary to previous suggestions, fertility restoration is not a property of the nucleolar organiser but of a separate locus.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 69 (1985), S. 325-328 
    ISSN: 1432-2242
    Schlagwort(e): Line × tester analysis ; Triticum aestivum ; Gene action ; Combining ability ; Mating designs
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary For studying the inheritance of metric traits, diallel cross and factorial mating designs are commonly used. Since factorial mating design is less restrictive in crossing plans, the genetic information drawn from it was compared with that from a diallel cross. The comparison was made using graphical, genetic components and combining ability analyses for grain yield, grain weight and spike length in a field experiment of bread wheat (Triticum aestivum L.). Analyses were made on a nine parent diallel cross and a 4 ♀ × 5 ♂ factorial mating design which was sampled from the diallel cross. In general, there was a high degree of agreement between the results obtained from factorial mating design and diallel cross analyses showing thereby that the former provides almost equivalent genetic information to the latter.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 69 (1985), S. 583-589 
    ISSN: 1432-2242
    Schlagwort(e): Common wheat ; Triticum aestivum ; Electrophoresis ; Endosperm proteins ; Glutenins ; Gliadins ; Genetic control
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Total endosperm proteins extracted from both several common wheat cultivars and some intervarietal substitution lines derived from them were fractionated according to their molecular weight in a high resolution one-dimensional gel electrophoresis. The four donor cultivars and the recipient one — ‘Chinese Spring’, possessed differentially migrating protein bands in the fractions of high molecular weight (HMW) glutenins and gliadins. Several of these bands were identified for the first time in this study. By utilizing intervarietal substitution lines the control of the HMW glutenins and gliadins by chromosomes of homoeologous group 1 was either reaffirmed or, for the new bands, established. Several HMW gliadin subunits showed a considerable variation in their staining intensity in the intervarietal substitution lines indicating that their expression was dependent on the genetic background.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 70 (1985), S. 294-299 
    ISSN: 1432-2242
    Schlagwort(e): Anther culture ; Pollen callus (plantlet) ; Induction frequency ; Triticum aestivum ; Agropyron glaucum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Experimental results showed that the use of potato extract as a basic component of culture medium had a promoting effect on producing calli in anther culture of the intergeneric hybrids of Triticum aestivum × Triticum-Agropyron (intermediate type). The induction frequencies of pollen callus on the Potato-II medium containing potato extract as the main component was much higher than that found on N6 and W5 media. The induction frequencies of pollen callus and green plantlets in four intergeneric hybrid material inoculated at the late-uninucleate pollen stage were all higher than those inoculated at the mid-uninucleate stage. Appropriate increases in culture temperature significantly increased pollen callus induction frequencies of the intergeneric hybrids. The genotype and physiological state of anther donor plants also influenced pollen callus and green plantlet induction frequencies.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 70 (1985), S. 634-642 
    ISSN: 1432-2242
    Schlagwort(e): Hexaploid wheat ; Triticum aestivum ; Glutenins ; Electrophoresis ; Amino acid analysis ; Peptide mapping
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Several high molecular weight endosperm glutenin subunits, coded by genes located on chromosomes 1A, 1B and 1D of common wheat, Triticum aestivum L. em. Thell., were isolated from excised gel segments and subjected to amino acid analysis and peptide mapping; the latter was carried out following a limited digestion with trypsin, chymotrypsin or Staphylococcus aureus — V8 protease. Generally, all high molecular weight glutenins had a similar amino acid composition but several significant differences were observed in some of them. Both analyses revealed that the structural similarity among the various subunits was related to the homology of the genes coding them: subunits coded by homoalleles, i.e., different alleles of the same gene, were most similar; those coded by homoeoalleles, i.e., alleles of homoeologous genes, were less similar; whereas subunits coded either by alleles of different genes of the same gene cluster, or by nonhomoeoalleles of homoeologous clusters, were the least similar. Several small peptides derived from protease digestion of various subunits had a higher than expected staining intensity indicating that small peptide repeats may be interspersed within the glutenin subunits. The evolutionary course of the high molecular weight glutenins is discussed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 71 (1985), S. 278-283 
    ISSN: 1432-2242
    Schlagwort(e): Nucleolar competition ; Amphiplasty ; Ag-NORs ; Addition lines ; Triticum aestivum ; Aegilops umbellulata
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The nucleolar organizer activity of wheat (Triticum aestivum, AABBDD) and Aegilops umbellulata (UU) chromosomes have been analyzed in the complete set of the chromosome addition lines by using a highly reproducible silver-staining procedure. Chromosomes 1U and 5U produce the partial inactivation of wheat nucleolar organizer chromosomes 6B, 1B and 5D. The chromosomes D and G from Ae. umbellulata, which are not SAT-chromosomes, seem to specifically influence the activity of wheat NORs. The predominant status of the U genome with respect to nucleolar competition in the Triticeae is confirmed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Euphytica 34 (1985), S. 525-537 
    ISSN: 1573-5060
    Schlagwort(e): Triticum aestivum ; bread wheat ; somaclonal variation ; chromosomal aberrations ; wheat breeding
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Transmission of somaclonal variation was studied in callus derived (SC1) plants of wheat, Triticum aestivum L. Second (SC2), third (SC3) and fourth (SC4) generations were compared with those obtained from embryo culture (E1-E4). SC2 generation had significantly lower grain yield (−37.3%), reduced thousand kernel weight (−7.8%) and shorter height (−2.1%) than that of E2, and included 5.7% seed-sterile and 15.0% partially seed-sterile plants. SC3 generation showed reduced yield (−12.6%), lower thousand kernel weight (−4.9%) and shorter plant height (−1.9%) than E3 generation. SC4 progeny of a short height, partially sterile SC1 variant included aberrant plants: a haploid, few aneuploids, mixoploids, some showing multiploidy, spindle abnormalities, multivalents, bridges and fragments, and tillers having supernumerary spikes with branched rachis. Somaclonal variation resulted from genome instability in callus, and likely involved transposable elements.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Euphytica 34 (1985), S. 559-571 
    ISSN: 1573-5060
    Schlagwort(e): Triticum aestivum ; wheat ; ear emergence ; number of leaves ; number of spikelets ; photoperiod ; vernalization ; geographical distribution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Differences in response to photoperiod and vernalization and genetic variation independent of photoperiod and vernalization (earliness per se), affecting time of ear emergence of wheat, were identified in controlled environment experiments with 33 varieties of diverse geographical origin. The results were compared with an analysis of time of ear emergence of 10409 T. aestivum accessions from the USDA Small Grain Collection grown from autumn sowings in Pendleton, Oregon, and spring sowings in Fargo, North Dakota. The effect of differences in photoperiod and vernalization sensitivity on time of ear emergence was similar to the effect of earliness per se, both under controlled environment conditions and in the field. Most of the accessions from low latitude regions reached ear emergence rapidly owing to their insensitivity to photoperiod and vernalization and earliness per se factors accelerating ear emergence. Lateness was common among accessions from Northern Europe, Afghanistan and Turkey, which was due to sensitivity to photoperiod and vernalization, and to earliness per se factors delaying ear emergence. The physiological basis of earliness per se is discussed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 11
    Digitale Medien
    Digitale Medien
    Springer
    Euphytica 34 (1985), S. 153-159 
    ISSN: 1573-5060
    Schlagwort(e): Triticum aestivum ; wheat ; Secale cereale ; rye ; Triticosecale ; callus culture
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Callus cultures were initiated from inflorescence explants of wheat, rye and triticale on MS medium supplemented with 2 mgl-1 2,4-D+5% CW or 2 mgl-1 2,4-D+0.5 mgl-1 BA. On transfer of the cultures to medium supplemented with 15% CW+0.2 mgl-1 NAA or 1 mgl-1 BA+0.1 mgl-1 IAA, shoot buds and embryoids were produced. Full fledged plantlets obtained on MS medium supplemented with NAA were transferred to the field. Cytological analysis showed the plants to be diploid. However, the regenerated plantlets were shorter, produced fewer tillers and had lower fertility compared to the control.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 12
    Digitale Medien
    Digitale Medien
    Springer
    Euphytica 34 (1985), S. 207-211 
    ISSN: 1573-5060
    Schlagwort(e): Triticum aestivum ; wheat ; Secale cereale ; rye ; hybrid necrosis ; intergeneric cross
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary An inbred line of rye (Secale cereale L.) has been found to carry a gene for hybrid necrosis. This gene was detected in crosses with a highly crossable wheat (Triticum aestivum L.) genotype which carries the gene Ne2. This appears to be the first report of a gene for hybrid necrosis being present in the rye genome.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 13
    Digitale Medien
    Digitale Medien
    Springer
    Euphytica 34 (1985), S. 317-327 
    ISSN: 1573-5060
    Schlagwort(e): Triticum aestivum ; bread wheat ; aneuploidy ; semi dwarfness
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Tall varietal impurities occurring in a number of new semi-dwarf winters wheats carrying the Norin 10 dwarfing genes Rht1 or Rht2 are causing problems at seed certification. Cytological analysis of such impurities from three varieties shows they are aneuploids and are mainly monosomic (2n=41) for chromosomes carrying semi-dwarfing genes. Because Rht1 and Rht2 act as suppressors of height, their reduced dosage as in monosomics, produces plants considerably taller than in the euploid condition.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 14
    Digitale Medien
    Digitale Medien
    Springer
    Euphytica 34 (1985), S. 367-370 
    ISSN: 1573-5060
    Schlagwort(e): Triticum aestivum ; wheat ; frost resistance ; chromosome 5A ; reciprocal monosomic analysis ; allelic variation ; substitution line
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary F2 monosomic analysis and the direct comparisons between aneuploid series from different varieties of wheat suggest the likelihood of allelic variation. It is impossible however, from these studies to prove unequivocally that allelic variation exists. Some effects can be due to chromosome dosage rather than allelic variation. This disadvantage was overcome by using reciprocal monosomic analysis to study the genetic control of frost resistance on chromosome 5A in wheat. Data support the previous results obtained by F2 monosomic and substitution analysis. The chromosome 5A has been shown to be the one which carries the major allelic differences that distinguish wheat varieties Chinese Spring, Rannyaya 12 and Mironovskaya 808 for frost resistance.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 15
    ISSN: 1573-5060
    Schlagwort(e): Triticum aestivum ; wheat ; reciprocal F1 monosomics ; ear emergence ; number of leaves ; number of spikelets ; photoperiod ; vernalization ; growth rate
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary A reciprocal F1 monosomic analysis of chromosomal differences between Spica and Bersée was carried out under controlled environment conditions. Chromosomes associated with differences in days to ear emergence, number of leaves and number of spikelets were identified. The results indicated that chromosome 2B of Spica carries a photoperiod insensitivity allele at the Ppd 2 locus. Both Spica and Bersée appear to have a vernalization insensitity allele at the Vrn 2 locus on chromosome 5B. On chromosome 3A, 4B, 4D and 6B factors were found with major effects on earliness per se, diffeences in ear emergence and number of spikelets which were independent of photoperiod and vernalization. The possibility that these factors influence growth rate is discussed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 16
    Digitale Medien
    Digitale Medien
    Springer
    Euphytica 34 (1985), S. 233-236 
    ISSN: 1573-5060
    Schlagwort(e): Triticum aestivum ; wheat ; auricle colour ; genetics ; instability of expression ; gene penetration
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Only a few publications deal with the genetics of auricle colour of wheat. They report that red pigmentation is conditioned by one dominant gene, symbolized Ra. Ra is present in Egyptian local wheat cultivars. My own research showed the great instability of this character.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 17
    Digitale Medien
    Digitale Medien
    Springer
    Euphytica 34 (1985), S. 625-640 
    ISSN: 1573-5060
    Schlagwort(e): Triticum aestivum ; bread wheat ; selection criteria ; harvest index ; grain yield ; hill plots ; genotype x environment interaction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Alternative strategies of multi-site testing of advanced lines in the northern wheat belt of New South Wales have been evaluated, using genetic parameters for large plot grain yield and hill plot harvest index estimated from dryland and irrigated trials at regional sites during 1975–1981. The average pairwise genetic correlation of large plot grain yields recorded at different sites within years was 0.45±.03, with a mean repeatability within trials of 0.56±.05. Harvest index measured in 20-grain hill plots in 1978 showe genetic correlations of 0.98±.08 with plot yield at the same site, and 0.39±0.06 with plot yield assessed at other sites in the same year. The genetic correlation between harvest index in hill plots and total biological yield in large plots at the same site was 0.84±.13, the relationship showing no evidence of curvilinearity. Selection for harvest index in hill plots is therefore expected to lead to an increase in biological yield as well as grain yield in the breeding populations studied. Quantitative genetic theory suggests that the response to selection for grain yield can be increased by approximately 40% with an initial screening using hill plot harvest index at three sites instead of one, and reallocation of resources in the first stage of large plot yield assessment to include 6–8 sites, rather than dryland and irrigated trials at a single location.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 18
    Digitale Medien
    Digitale Medien
    Springer
    Euphytica 34 (1985), S. 833-847 
    ISSN: 1573-5060
    Schlagwort(e): Triticum aestivum ; wheat ; growth analysis ; relative growth rate ; selection
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary For a better insight in the effect of wide spacing on the outcome of plant selection in spring wheat, the growth of free-grown individual plants was followed in time for each of 12 cultivars. As time proceeded, the cultivar differences for per-plant weight showed progressively less relation with those for seedling weight. At anthesis, the genetic correlation with seedling weight was still about 0.80, but at final harvest it was only 0.06. This contrasted with the genetic correlation between seedling weight and final biomass in closely planted mixtures which was on the average 0.77. The outcome of selection of genotypes in isolation is therefore expected to deviate substantially from that of selection in densely planted segregating populations where the differences in initial size tend to be maintained in time. The ranking of the varieties grown in isolation changed in time because of differences in relative growth rate (RGR). The genetic variance of RGR decreased much less with time than RGR itself. Late-flowering varieties showed the higher RGR so that these varieties improved their position in the ranking in isolation. Special attention is paid to the methodology of plant growth analysis in variety experiments and in estimating means and variances of RGR.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 19
    Digitale Medien
    Digitale Medien
    Springer
    Plant and soil 85 (1985), S. 3-9 
    ISSN: 1573-5036
    Schlagwort(e): Catabolism ; Glycine betaine ; Salt tolerance ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Glycine betaine is readily accumulated in wheat (Triticum aestivum cv. Inia) shoots during periods of salinity stress. The ability of the plant to utilize betaine as a source of nitrogen remains unresolved. We, therefore, conducted solution culture experiments in a greenhouse to test the hypothesis that betaine is degraded in wheat shoots under conditions of severe nitrogen deficiency. Betaine concentrations increased in continuously salt stressed plants for only 17 days after salinity was imposed. After this period, concentrations (dry weight basis) decreased steadily until plants died 32 days later. Decreases in betaine concentration were also observed in treatments where salinity stress was removed. The rate of decrease in concentration was greatest in the N-free treatment. These decreases in betaine concentration were the result of dilution by plant growth. Betaine contents (μmol shoot−1) remained unchanged after removal of substrate nitrate. Therefore our results support the hypothesis that betaine is a stable end product of metabolism.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 20
    Digitale Medien
    Digitale Medien
    Springer
    Plant and soil 83 (1985), S. 327-330 
    ISSN: 1573-5036
    Schlagwort(e): Amphiploid ; Elytrigia ; Genome ; Salinity ; Triticum aestivum ; Wheat ; Wheatgrass
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Triticum aestivum cv. Chinese Spring wheat,Elytrigia elongatum (tall wheatgrass), and theTriticum-Elytrigia amphiploid were grown in complete nutrient culture containing, in addition, 0, 40, 80 and 120 mM NaCl. The 3 genotypes responded quite differently to increasing salinity; the Na concentration of wheat shoots increased in direct proportion to the increase in salinity of the external medium whereas the Elytrigia response was interpreted as showing high affinity for Na at low external Na (40 mM) but comparative exclusion of Na at high salinities (120 mM). In contrast, Na levels of the amphiploid were less than those of either wheat or Elytrigia under both low and high salinities. Thus the amphiploid behaved like wheat at 40 mM NaCl but more like Elytrigia at 120 mM NaCl because Na transport to the amphiploid shoot was restricted over the whole salinity range. The K concentration of the amphiploid shoot at high salinities was significantly greater than the K concentrations of either wheat or Elytrigia.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 21
    Digitale Medien
    Digitale Medien
    Springer
    Plant and soil 83 (1985), S. 399-409 
    ISSN: 1573-5036
    Schlagwort(e): Inhibitory bacteria ; Pseudomonads ; Root growth ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Root-colonizing pseudomonads capable of inhibiting seedling winter wheat (Triticum aestivum L.) root growth in an agar seedling bioassay also significantly inhibited wheat root growth in vermiculite; however, the inhibitory trait is quite labile in laboratory culturing. The extent of inhibition in both the agar and vermiculite medium depended on inoculum level. These pseudomonads were found to produce a toxin capable of inhibiting growth ofEscherichia coli C-la andBacillus subtilis. Field isolates that strongly inhibit growth of indicator bacteria also inhibited root growth. Toxin production by the bacteria appeared necessary for inhibition of root growth and indicator bacteria as toxin-negative (TOX−) mutants no longer inhibited either. Antibiosis towardsE. coli as well as wheat seedling root inhibition in agar was reversed by L-methionine, providing further evidence that a toxin, produced by these organisms, is involved in growth retardation.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 22
    Digitale Medien
    Digitale Medien
    Springer
    Plant and soil 86 (1985), S. 369-378 
    ISSN: 1573-5036
    Schlagwort(e): Dry-matter accumulation ; Glomus deserticola ; Glomus fasciculatum ; Mycorrhizae ; Root growth ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Drought resistance of wheat (Triticum aestivum L.) as influenced by two vesiculararbuscular mycorrhizal (VAM) fungi,Glomus fasciculatum 10 andGlomus deserticola 19, was evaluated. Soil columns 0.15 m diam. by 1.20 m length were used to reduce the influence of limited rooting space. With initial soil water at 0.5 MPa (0.145 kg kg−1), plants were subjected to low-level water stress throughout the experiment and severe water stress for 24 h at one (55 days after transplanting, Feekes scale 10.1) two (55 and 63 days, Feekes 10.1 and 10.2), or three (55, 63, and 70 days, Feekes 10.1, 10.1, and 10.2) periods. After each stress period, one set of plants was watered and grown to maturity without subsequent water stress. A second set of plants was harvested 1 week after stress.G. fasciculatum-inoculated plants harvested 7 days after stress at 55 days had greater leaf area and leaf, total plant, and root weight than non-VAM plants.G. deserticola-inoculated plants had greater leaf area and leaf weight than non-VAM plants. After stress at 55 and 63 days, leaf area, and leaf and total dry weight were again greater for VAM than for non-VAM plants. However, after stress at 55, 63, and 70 days, differences in aboveground biomass between VAM and non-VAM plants were not significant at P=0.05. Aboveground biomass was not affected by VAM species in plants stressed at 55 or 55 and 63 days, butG. fasciculatum-inoculated plants produced more tillers atter stress at 55 days. When grown to maturity, VAM plants which had undergone three stress periods had twice the biomass and grain yield as non-VAM plants subjected to the same stress. The three stress periods reduced number of heads and kernel numbers of weight of non-VAM plants compared to VAM plants.G. fasciculatum-inoculated plants consistently had increased root weight and rooting depth.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 23
    Digitale Medien
    Digitale Medien
    Springer
    Plant and soil 88 (1985), S. 377-384 
    ISSN: 1573-5036
    Schlagwort(e): Carbonic anhydrase ; Dry matter ; Eucalyptus maculata ; E. marginata ; E. patens ; Seedlings ; Symptoms ; Triticum aestivum ; Zinc
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Effects of zinc supply on shoot and root dry weight, root length, zinc concentrations and carbonic anhydrase activity were measured in 52 day old seedlings ofEucalyptus maculata, E. marginata, E. patens and wheat grown in a zinc deficient soil in the glasshouse. Symptoms of zinc deficiency in the eucalyptus and wheat appeared within 20 to 35 days. Eucalypt seedlings had short internodes and small necrotic leaves, reduced dry weight of shoots and roots, root length and zinc concentrations in young leaves; the measurable level of leaf carbonic anhydrase activity decreased to zero. Similar responses also occurred in wheat. The level of zinc fertilizer required for normal growth of Eucalyptus seedlings is therefore likely to be similar to that used for wheat and other agricultural crops.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 24
    Digitale Medien
    Digitale Medien
    Springer
    Plant and soil 87 (1985), S. 309-310 
    ISSN: 1573-5036
    Schlagwort(e): Leaf water potential ; Pressure chamber ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary The most widely used technique of leaf water potential measurements is with the Scholander pressure chamber. Representative leaf water potential values require many determinations on individual leaves and this can be time consuming in large fields or experiments with multiple treatments. This paper describes a method of obtaining a mean value more rapidly, by using two leaves in the pressure chamber at the same time, but recording the end point of each leaf separately.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 25
    Digitale Medien
    Digitale Medien
    Springer
    Plant and soil 88 (1985), S. 93-100 
    ISSN: 1573-5036
    Schlagwort(e): Aluminum ; Calcium ; Copper ; Glycine max ; Iron ; Magnesium ; Manganese ; Nitrogen ; Phosphorus ; Potassium ; Sorghum bicolor ; Triticum aestivum ; Zea Mays ; Zinc
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Information is limited on soil contamination of leaves from field-grown row crops, especially with respect to aluminum (Al) analyses. The objective of this study was to determine the influence of washing leaf samples with either deionized water or detergent solution on elemental analyses for several agronomic crop plants. The crop plants sampled were corn (Zea mays L.), soybean (Glycine max L. Merr.), grain sorghum (Sorghum bicolor L. Moench), and wheat (Triticum aestivum L.). The crops were grown on a range of soil types, soil pH values, and tillage practices. Samples of upper leaves and lower leaves were collected separately. The samples were either not washed, washed with deionized water, or washed with detergent solution. After drying, grinding, and digesting, the samples were analyzed for Al, nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu). For all crop plants and conditions studied, there was no effect on measured N, P, K, Ca, Mg, Mn, Zn, or Cu concentrations, but measured Al and Fe concentrations were influenced by washing. In general, washing had a greater effect on Al analyses than on Fe analyses. Soybean samples were most affected by washing, while wheat samples seemed to be least affected. The results reflected greater contamination of lower leaves than upper leaves. Decontamination procedures appear necessary prior to Al and Fe analyses of field-grown crop plants.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 26
    Digitale Medien
    Digitale Medien
    Springer
    Plant and soil 86 (1985), S. 347-355 
    ISSN: 1573-5036
    Schlagwort(e): Azospirillum ; Rhizospheric bacteria ; Spring wheat ; Triticum aestivum ; Triticum durum ; Yield response
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Five field experiments were conducted during 1982 and 1983 to evaluate the yield response of two lines of common wheat and one line of durum wheat to several rhizospheric bacteria. The two lines tested in the 1982 experiment (a common wheat and a durum wheat) showed a considerable yield response to incoulation withAzospirillum brasilense, with an average significant yield incresae of 23%. In the 1983 experiments, variable yield responses, some of which were significant, were obtained by inoculating three wheat lines (two common wheat and one durum wheat) with Azospirillum or with other rhizospheric bacteria, isolated from various Israeli wild relatives of wheat. A certain specificity between the tested wheat lines, the applied bacteria and the particular local conditions was evident. Inverse relationships were found between the maximum percentage yield increase due to inoculation with the most efficient bacteria and the yield level of the non-inoculated plots.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 27
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. vi 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 28
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 49-63 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A molecular model for the complex formed between the jack bean lectin concanavalin A (Con A) and glycopeptides of the complex biantennary class is described. The model was derived using coordinates for Con A determined by x-ray crystalographic refinement techniques, with 1.75-Å resolution data, and coordinates for the glycopeptides obtained from 1H-nmr measurements, using the nuclear Overhauser effect. Previous solution and crystallographic studies provided several constraints on the possible mode of interaction of the lectin and the glycopeptide. Examination of the model suggests that the glycopeptide binding site is defined by four loops on the protein surface made up by amino acid residues: 12-18, 98-102, 205-208, and 226-229. Within these loops, it favorable interactions with high-affinity ligands and tose responsible for the unfavourable interactions with poor ligands.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 29
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Peptide hormones and neurotransmitters are functional amphiphilic substances that deploy their chared and nonpolar substituents as required for traversing aqueous phases en rout to their ultimate transfer into the lipid-rich environment of their membrane-embedded receptors. As a means of determining the role(s)that cellular membrane lipids may play in mediating these events, we describe an experimental approach, using high-resolution 1H-and 13C-nmr spectroscopy, for delineation of the structures of complexes between the (neurotransmitter pentapeptide) enkephalins and micellar and vesicular phospholipid particles. Residue-specific enkephalin interactions with lipid are identified; affinity constants for the hydrophobic component(s) of peptide/lipid association are calculated for enkephalin and several of its analogs; and comparisons with morphine are presented. Finally, based on molecular details obtained from nmr experiments, a model is proposed for the encoutner of a peptide hormone with a phospholipid membrane surface.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 30
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985) 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 31
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Both (dC-dG)4 and d(CGCATGCG) crystallize in hexagonal lattices and their three-dimensional structure has been solved by x-ray diffraction analysis. Both molecules are found to form Z-DNA, although the fine details of the structure cannot be visualized due to the statistical disordering of the molecules along the c-axis, which is brought about by the symmetry constraints of the space group. This represents the first time in which the unmodified dinucleotide sequences CpAp and TpGp have been found to form Z-DNA in a crystalline lattice.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 32
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 359-377 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Differential melting curves (DMCs) of DNAs pA03 and pBR322 in solutions of different ionic strength (0.02 and 0.2M Na+) were obtained. A previously developed procedure of glyxal fixation of partially denatured DNA molecules at temperatures within the melting range was used to construct electron-microscopic melting maps for pBR322 and pAO3 plasmid DNA and for the replicative form of bacteriophage φX174 DNA, allowing the melting of these DNA molecules to be followed in solutions of low (0.1 × SSC) and high (1 × SSC) ionic strength. In spite of the fact that the melting was at nonequilibrium at the low ionic strength, the melting maps for the two kinds of solutions practically coincided. Experimental data are compared with theoretical calculations based on the Fixman-Freire algorithm. The conclusion is that the melting pattern of these DNAs is, on the whole, correctly described by the theory, although there are appreciable differences between the theoretical and experimental differential melting curves. We have also determined the relation between the melting temperature of a region and its GC content, with allowances made for the boundary conditions of melting in 0.1 × SSC and 1 × SSC solutions, and have analyzed the theoretical shape of peaks of the DMCs.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 33
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 421-423 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 34
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985) 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 35
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 427-439 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Electrostatic effects are believed to determine the molecular structure and function of macromolecules in many ways. In metallo-based enzymes and in metal-macromolecule interactions in solution, these effects may predominate. In order to tackle metal ion-nucleic acid interactions theoretically, we propose a modification of Debye's distance-dependent dielectric function first proposed more than 50 years ago. This function more closely approximates physical reality at small interatomic separations. Our theory yields a dielectric function that gives reasonable agreement with experimental data in preliminary calculations.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 36
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: It is suggested that the three-dimensional structure of globular proteins is partly determined by a framework of strengthened hydrogen bonds that involves both ionic side chains and water molecules in addition to the polypeptide backbone. This conclusion follows from a combination of the results of ab initio molecular-orbital computations on small model molecules and high-accuracy x-ray data on the rubredoxin molecule. The computations yield the idea of hydrogen-bonded bridges that are built from tens of atoms, and the experimental information yields the idea that the bridges are assembled into clusters, each of which is built from hundreds of atoms. Some 10 such clusters then form a globular protein.
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 37
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 581-581 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 38
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 581-581 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 39
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 157-166 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Monoclonal antibodies to different parts of bacteriorhodopsin were raised to define its topography in the membrane. It is shown that the amino acid residue Glu 194 is a part of an antigenic determinant and should be located on the membrane surface. We found that the removal of the C-terminal 17 amino acid sequence does not affect the efficiency of the proton transport in bacteriorhodopsin. From a combination of proteolysis and secondary structure prediction methods an experimentally testable structural model for bovine rhodopsin is presented. The complete amino acid sequence of the transducin γ-subunit consisting of 69 residues was determined.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 40
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 403-419 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Fluorescence and absorbance methods were used to study the interaction of daunomycin with calf-thymus DNA over a wide range of temperatures and NaCl concentrations. van't Hoff analysis provided estimates for the enthalpy of the binding reaction over the NaCl range of 0.05-1.0 M. Daunomycin binding is exothermic over this entire range, and the favorable binding free energy arises primarily from the large, negative enthalpy. Both the enthalpy change and entropy change are strong functions of ionic strength. Possible molecular contributions to the enthalpy and entropy are discussed, leading to the tentative conclusion that hydrogen-bonding interactions at the interacalation site are the primary contributors to the observed thermodynamic parameters. The dependence of the enthalpy on the ionic strength is well beyond the predictions of current polyelectrolyte theory and cannot be fully accounted for. The enthalpy and entropy changes observed compensate one another to produce relatively small free-energy changes over the range of solution conditions studied.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 41
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Mechanical creep and creep recovery in small shearing deformations have been studied in unligated clots formed with both thrombin and ancrod. In thrombin clots, both A binding sites (which interact with “a” sites to link monomer units within a protofibril) and B sites (which interact with “b” sites to form links between protofibrils) are exposed to enable formation of linkages; in ancrod clots, only the A sites are exposed. Fine clots (with minimal lateral aggregation of protofibrils), coarse clots (with substantial aggregation of fibril bundles), and clots of intermediate coarseness were compared. Fine thrombin clots showed less creep at short times but more creep at long times than coarse or intermediate clots and had more irrecoverable deformation relative to the initial elastic deformation. Ancrod clots had greater irrecoverable deformation than the corresponding thrombin clots, both fine and coarse. The permanent deformation in fine ancrod clots was enormous, corresponding almost to fluid character; the rate of permanent deformation was larger than that in fine thrombin clots by more than two orders of magnitude. For all types of clots, differential measurements of compliance (or its reciprocal, elastic modulus), as well as the applicability of the Boltzmann superposition principle to calculation of creep recovery, showed that the overall density of structure remained constant throughout the mechanical history; i.e., if structural elements were breaking, they were reforming at the same rate in different configurations. The possibility that the weakness of ancrod clots is attributable to partial degradation of α-chains rather than absence of Bb linkages was eliminated by comparisons of clots made with thrombin, ancrod, and ancrod plus thrombin; the last two showed identical partial degradation of α-chains (by gel electrophoresis), but the first and third had essentially identical initial elastic moduli and creep behavior. Two alternative mechanisms for irrecoverable deformation in fine clots are discussed, involving rupture of protofibrils and slippage of twisted segments, respectively.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 42
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 735-745 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Recently, it was suggested that parallel β-sheets have a significant dipole moment, in contrast to antiparallel sheets. Ab initio molecular-orbital (MO) calculations on parallel and antiparallel β-strands of tetra(Gly) show that they have very similar charge distributions. Interaction energies between two and three strands of tetra(Gly), obtained using the direct reaction field Hamiltonian, show that a particular choice of point charges is probably not crucial for calculating interactions within β-sheets, but that it might be for calculating interactions between these sheets and other parts of a protein, in particular, α-helices. The point-charge representation of our MO-SCF results will probably reduce the hazard of introducing artefacts in electrostatic calculations of protein conformational energies, provided the short-range interactions are treated in a more realistic way, i.e., such that intra- and interchain induction effects are included.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 43
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The pH and ionic strength dependence of conformation of the COOH-terminal fragment 206-316 (fragment FII) of thermolysin was monitored by far-uv CD and difference absorption measurements. This fragment was shown previously to possess the properties of a protein domain, i.e., able to refold into a stable nativelike structure [Fontana, A., Vita, C. & Chaiken, I. M. (1983) Biopolymers 22, 69-78]. Analysis of the CD spectra in the pH range of 1-12 indicated that near pH 1, the conformation of fragment FII appears to be in an intermediate state (H) between the fully unfolded one (U) [the guanidine hydrochloride (Gdn · HCl)-induced unfolded state] and the nativelike state (N - that attained at neutral pH). Quantitative analysis of secondary structure from CD spectra revealed that state H at 4°C is characterized by some 30% α-helical structure, compared to 47% for state N. The heat- and Gdn · HCl-mediated unfolding transitions of state H were fully reversible and characterized by little cooperativity, which is taken as an indication that state H corresponds to several species possessing different, and low, conformational stabilities. The midpoint transition from state H to N occurs near pH 2.5, implying that the acid transition results from the titration of carboxyl groups of the fragment with anomalously low pK, as would be expected for groups involved in specific salt bridges. Fragment FII at pH 1 (state H) may be induced to exhibit nearly the same degree of helicity of state N simply by increasing the ionic strength of the solution, thus reducing the repulsive interactions between positive charges within the highly charged fragment at pH 1. The results obtained emphasize the role of electrostatic interactions in the folding and stability of fragment FII and suggest a mechanism of folding of the fragment from U to N involving an intermediate state characterized by an assembly of fluctuating α-helices.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 44
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 867-882 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: DNA supercoiling is both an interesting problem from the theoretical point of view and an important phenomenon affecting DNA functions in vivo. Experimentally, however, hardly more than the overall hydrodynamic shape, superhelical density, and enzymic or chemical reactivity of the parameters that are in some way related to DNA secondary and tertiary structure in the superhelical state can be determined. Consequently, it is highly desirable to build up models of DNA supercoiling that, on the one hand, match the above type of global data and, on the other, take advantage of the knowledge about DNA structure at lower levels of complexity, i.e., with linear DNA molecules and its synthetic models. One possible approach, presented here, deals with an extension of Fuller's and Benham's general ideas concerning an elastomechanical model of DNA supercoiling. We extend their model with an algorithm suitable for numerical calculations and construct a fast computer program, ROPASE, that displays the rod shapes as dependent on its elastic properties and applied stress. Development of this program made inevitable a detailed analysis of the input parameters found to be degenerate in the sense that not all of them should be considered variable to generate the whole set of possible solutions of the model. Many calculations were performed using ROPASE to test its properties and the properties of the elastomechanical model. Representative DNA shapes are presented.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 45
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 905-910 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 46
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 883-895 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The thermotropic behavior of lipid vesicles prepared from dimyristoylphosphatidylcholine in the presence of cytochrome c oxidase has been studied by highly sensitive differential scanning microcalorimetry. This protein has a remarkable effect on the gel-liquid crystalline transition of dimyristoylphosphatidylcholine. In the presence of cytochrome c oxidase, the thermogram of the lipid vesicles exhibits a second endothermic peak, which is adjacent to the main lipid phase-transition peak and appears at a higher temperature. As the concentration of added protein increases, the two endothermic peaks become further separated, and the transition temperatures and the heats of transition corresponding to both endothermic peaks decrease. A greater decrease in the transition temperature at the lower-temperature peak with added protein suggests that the lower-temperature peak is more perturbed than the higher-temperature peak. The higher-temperature peak is not thermally reversible. Treatment of sample well above the transition temperature results in a reduction of the magnitude of the higher-temperature peak. The lipid-protein interaction contributing to the higher-temperature peak is discussed.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 47
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: An intercalation model of a complex between DNA and a bleomycin fragment (BLMF), consisting of the bithiazole core and an amide and a protonated amino substituent, is presented. The model, which shows a preference for BLMF with the protonated amine in the minor groove and the acetyl terminal inserted into either the minor and major grooves, respectively, agrees with recently obtained nmr data. The selection of sites I and II, which have the smallest unwinding of the three theoretical intercalation sites, is consistent with the experimental unwinding angle of 12°. The bithiazole moiety stacks between two base pairs of the double helix, while the protonated substituent interacts ionically with the negatively charged regions of the backbone in the minor groove of the DNA. The protonated amine also forms an intramolecular hydrogen bond with the carbonyl oxygen of the amide group on the same substituent. Analysis of drug complexes with different base-pair sequences reveal four energetically defined groups. The relative energy of the dimer duplex complexes of BLMF correlates with bleomycin's observed base-sequence specificity upon cleavage. The most stable intercalation complexes form adjacent to the bases cleaved most readily. This correlation suggests a primary connection between intercalation and cleavage. A model cleavage site based on these preliminary theoretical calculations and the experimental observations is proposed. It consists of an intercalation site in a trimer duplex. Pyrimidine(p)purine sequences are the predominant sites for intercalation, and the base adjacent to the site at the (3′) end is cleaved.
    Zusätzliches Material: 7 Ill.
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  • 48
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Boc-L-Leu-Aib-Pro-Val-Aib-Aib-Glu(OBzl)-Gln-Phl (Boc = t-butyloxycarbonyl, Aib = α-aminoisobutyric acid, Bzl = benzyl, Phl = phenylalaninol), C59H90N10O14, the protected C-terminal nonapeptide with the sequence 12-20 of alamethicin, crystallizes in the orthorhombic space group P212121 with a = 15.666, b = 16.192, c = 26.876 Å, and Z = 4. The molecular conformation is right-handed helical with three α-(5 → 1 hydrogen bonds) and three β-turns (4 → 1 hydrogen bonds). All but two of the hydrogen bonds are significantly longer than the usual value and show bifurcation to some extent. The α/310r-helical nonapeptide molecules are arranged head-to-tail along the a direction. The resulting linear antiparallel chains are linked by a weak intermolecular hydrogen bridge, thus forming a two-dimensional layer structure in the ab plane. The conformation of this nonapeptide is almost identical with that of the corresponding C-terminal part found by x-ray crystallography of the eicosapeptide alamethicin.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 49
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A newly designed host-guest approach is introduced as a experimental tool to explore the relationship between the sequence of peptides and their secondary structure. From the CD spectra of the host-guest peptides studied, a tentative scale for the α-helix potential in 2,2,2-trifluorethanol of guest amino acids is delineated. The conformational preferences are also examined in β-structure supporting media (solid state, CH2Cl2, CH3OH, H2O) using ir-absorption and CD techniques. Scales for the β-forming tendency of guest amino acid residues in the different media are delineated. It is shown that the preferred conformation of the host-guest peptides is a function of the medium, the chain length, and the protecting groups. Given the fact that conformational effects are important in peptide synthesis, the tentative scales may serve as a guideline to predict secondary structures of side-chain-protected or -deprotected peptides in a given solvent, complementing the well-known empirical conformational prediction parameters.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
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  • 50
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 1107-1111 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 51
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985) 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 52
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 1115-1129 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The interaction of CuCl2 with poly(S-carboxymethyl-L-cysteine) (poly[Cys(CH2COOH)]) and poly(S-carboxyethyl-L-cysteine) (poly[Cys(C2H4COOH)]) were studied by absorption spectra and circular dichroism (CD). On mixing CuCl2 with polypeptide solutions, absorption bands appeared at 320-325 nm in both polypeptides, and at 255-260 nm in the case of poly[Cys(CH2COOH)]. A stable bound species was formed in the case of poly[Cys(CH2COOH)], since the apparent molar absorption coefficient of the bound species did not depend on the mixing ratio. From the absorption data, it was inferred that Cu2+ ions were complexed with the side chains, most probably with sulfur atoms and carboxyl groups. Induced optical activities were observed for the two polypeptides. The CD spectra of poly[Cys(CH2COOH)] + CuCl2 gave simpler aspects than those of poly[Cys(C2H4COOH)] + CuCl2.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 53
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The atomic motions from a molecular-dynamics simulation of yeast tRNAPhe are analyzed and compared with those observed in protein simulations. In general, the tRNA motions are of larger amplitude, they are more anisotropic, and they arise from potentials of mean force that are more anharmonic than in the protein case. In both cases, the amplitudes are largest for atoms on the surface of the molecules. On the other hand, the most anisotropic and anharmonic atomic motions are generally found in the interior of the tRNA, while they are found on the surface of the protein. These differences are discussed in terms of the differences in structure between nucleic acids and proteins.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 54
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985) 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 55
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 947-960 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The purpose of this work was to improve our understanding of quasielastic light scattering from long rigid rods (QL 〉〉 1). For these scatterers, only small angular displacements are required to produce dephasing of the scattering light. This plus the fact that only rods lying perpendicular to Q contribute to the scattered light allow one to simplify the intermediate scattering function to an analytic form. This form is shown to be nonexponential, exhibiting (t)-½ behavior at long delay times. This new scattering function can then be fit to experimental functions using standard methods.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 56
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 1001-1008 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: We report high-resolution Raman spectra obtained from the circularly closed double stranded DNA (Form I) of the plasmid pBR322 and from its corresponding linear form (Form III). Comparison of the Raman spectra of the two forms demonstrates that, at a superhelical density (σ) of -0.069, which is of the same order as those found for most naturally occurring circularly closed DNAs, no major structural transitions occur under the influence of supercoiling. It is shown that at least 98% of all bases are fully basepaired, and that the conformation of the sugar-phosphate backbone is essentially identical to that of linear DNA. Thus, the structural influence of supercoiling, under these conditions, is confined to minor stretches of the plasmid DNA.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 57
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 1075-1087 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The force field established for guanine is applied here to guanine-containing biopolymers by considering the model compound 9-methylguanine, in which the methyl group is taken as a dynamic unit whose mass is concentrated on the carbon. In-plane normal-mode frequencies for this model compound and its N-deuterated analog are calculated. Band frequencies observed for guanine residue in Raman biopolymer spectra, such as those for DNA, RNA, or poly(G), are associated with calculated modes having similar wavelengths. They are discussed by taking into account observed and calculated D, 15N, and 18O isotopic shifts. The atomic displacements for the normal modes corresponding to the principal bands are illustrated and a number of assignments proposed.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 58
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 935-945 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A comparative study has been made using molecular mechanics of the ring entity of the active enkephalin analogs, Tyr-cyclo(-Nω-D-XXX-Gly-Phe-Leu-), where XXX is variously A2pr, A2bu, and Orn. Several conformations are favored for all three, and the lower-energy models are compatible with a Gly3-Phe4 bend in the active form of enkephalin. Some difficulties in assuming standard geometries in conformational surveys are illustrated.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
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  • 59
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 961-978 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The x-ray structure of Boc-L-Ala-Aib-Ala-Aib-Ala-Glu(OBzl)-Ala-Aib-Ala-Aib-Ala-OMe(I) represents the first α-helix determined by direct methods. This undecapeptide is a model of the N-terminus of alamethicin, and it exhibits voltage-dependent pores in bilayer membranes at a higher voltage and concentration than alamethicin. The molecule crystallizes in the monoclinic space group P21 with a = 10.602(1), b = 23.884(3), c = 13.622(1) Å, β = 95.61(6)°, and Z = 2. It adopts a right-handed α-helical conformation in the solid state with intramolecular 5 → 1 hydrogen bonds. An additional intramolecular hydrogen bond is bifurcated, forming a stronger 4 → 1 interaction (i.e., a β-turn III) and a weaker 5 → 1 interaction, thus prolonging the α-helical part up to 9 residues. The α-helix radius of 2.1 Å, the height per residue (distance Ni … Ni + 4) of 1.53 Å, the resulting length of the α-helical part of 13.8 Å (9 residues) resp. 15.3 Å (10 residues), the van der Waals radius (4.7 Å), and the minimal diameter of pores formed by aggregation of 3-10 α-helices were calculated omitting the Glu(OBzl) side chain. In the crystal, the α-helices are linked head to tail via two hydrogen bridges forming continuous chains. Adjacent helices are oriented in antiparallel with their helix axes and have only van der Waals contacts.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 60
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 1009-1022 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Time-resolved fluorescence polarization anisotropy measurements were performed on two fractionated samples of duplex poly(dGdC) containing 230 (+40, -30) base pairs (bp) and 590 ± 40 bp. Deconvolution using the intermediate zone formula for the twisting correlation functions (which is not valid for such short DNAs) yields apparent torsion constants for these two samples that are disparate and, in any case, too low. By similarly deconvoluting simulated data constructed from the correct twisting correlation functions, it can be inferred that these two samples actually exhibit the same torsion constant, α = (4.0 ± 0.4) × 10-12 dyn cm. Within the experimental uncertainties, this value is the same as that reported previously from this laboratory for linear φ29 and linearized M13mp7 DNAs. The 590-bp sample exhibited a peculiar evolution of its apparent torsional rigidity from a very high initial value, \documentclass{article}\pagestyle{empty}\begin{document}$ \hat \alpha $\end{document} = (11 ± 1) × 10-12 dyn cm, to a normal value over a period of several months, during which time many very small fragments appeared to be dissociated from, or annealed out, of the predominant high-molecular-weight species. Possible interpretations of these observations are discussed.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 61
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The conformation and internal dynamics of supercoiled pUC 8 DNA (2717 bp) are examined by dynamic light scattering, and the magnitude and uniformity of its torsional rigidity are determined using time-resolved fluorescence polarization anisotropy of intercalated ethidium dye. Neither measurement gives any indication of an appreciably reduced bending or twisting rigidity, or anomalously rapid internal motions. For 31P, in supercoiled pUC 8, we measure T2 = (2.0 ± 0.5) × 10-3 s. This lies within the range of present theoretical estimates obtained using normal rigidities. The proton linewidths observed for pUC 8 and pBR322 (4363 bp) DNAs are within a factor of 2-3 of those similarly estimated assuming ordinary rigidities.According to Bendel, Laub and James [(1982) J. Am. Chem. Soc. 104, 6748-6754], supercoiled pIns36 DNA (7200 bp) exhibits an astonishingly long T2 = 1.17 s for 31P, a slowest rotational relaxation time, τ = 5 × 10-9 s, and an enormously reduced bending rigidity. Serious questions raised by these findings are examined here. The 5 × 10-9 s slowest rotational relaxation time is shown to be physically inadmissible.The nmr relaxation theory developed previously by Allison, Shibata, Wilcoxon, and Schurr [(1982) Biopolymers 21, 729-762], is modified to incorporate new results for deformable filaments, which directly introduce the highly nonexponential tumbling correlation function for reorientation of the local helix axis. Essential requirements for a complete calculation of R2, including estimation of the tumbling correlation function and evaluation of the still unknown DIP/CSA cross-term, are described in detail. Slow coil-deformation modes analogous to the Rouse-Zimm modes of linear DNAs are shown to make an important, if not dominant, contribution to the R2 relaxation rate. Geometrical parameters in the theory are chosen to provide good agreement with literature data for 600-bp linear DNA. Using this theory and an informed guess for the tumbling correlation function, we find that the 31P-nmr relaxation data of Bendel et al., if correct, necessarily impose on their DNA one or more extreme properties, such as enormously reduced bending or twisting rigidities. In contrast, the same theory yields reasonable agreement with the T2 reported here for 31P in supercoiled pUC 8 DNA when its rigidities are assumed to be quite ordinary.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 62
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 1131-1146 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The aggregation behavior of the chemotactic peptide analogs, Formyl-Met-Leu-Phe-OMe (1) and Formyl-Met-Aib-Phe-OMe (2), has been studied in chloroform and dimethylsulfoxide over the concentration range of 0.2-110 mM by 1H-nmr spectroscopy. Both peptides associate in CDCl3 at concentrations ≥ 2 mM, while there is no evidence for aggregation in (CD3)2SO. Analog 1 adopts an extended conformation in both solvents favoring association to form β-sheet structures. A folded, γ-turn conformation involving a 3 → 1 hydrogen bond between Met CO and Phe NH is supported by 1H-, 13C-nmr, and ir studies of analog 2. The influence of backbone conformation on the ease of peptide aggregation is demonstrated by ir studies in CHCl3 and CD studies in dioxane.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
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  • 63
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 1169-1188 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A 24-ps molecular-dynamics simulation of motions in yeast tRNAPhe has been completed. The overall structure of the molecule is well preserved, for the motions represent fluctuations about an average structure that is very much like the crystallographic structure. The four helical stems remain intact, the structures of the loop regions do not deteriorate, and even the base stacking in the single-stranded amino acid acceptor terminus is maintained. With two exceptions, none of the sugar puckers is significantly changed. The unconstrained floppy motions of base A76 are responsible for the repuckering of ribose 76. The other sugar that repuckers is ribose, 46, and this is the result of a very small structural change in the center of the molecule that is also responsible for the breakage of one tertiary hydrogen bond. This change in local structure does not seriously distort the base-stacking and intercalation patterns where the variable loop and the D-stem interact.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
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  • 64
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 1233-1246 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The persistence length and effective long-range bending rigidity are derived for a discrete model of an anisotropically bending filament and shown to be independent of the torsional rigidity. The twisting persistence length is found to be independent of the anisotropic bending rigidity. Other statistical properties are briefly discussed, including the dependence of tangent vector projections on contour length. The dependence of a tensor contraction on contour length is derived for an isotropically bending filament with no equilibrium twist.
    Materialart: Digitale Medien
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  • 65
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 1257-1263 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Vibrational CD (VCD) and ir absorption data are reported for a series of films of Boc-(L-Ala)n-OMe homo-oligopeptides (n = 3-7) in the amide I and A regions. The data evidenced a sharp change between n = 3 and n = 4, which parallels the onset of β-structure formation, and another between n = 5 and n = 6, which parallels the full development of β-structure. This represents the first report of the application of VCD to oligopeptide conformation. The data resembled earlier reported film VCD studies of higher-molecular-weight polypeptides of known β-structure.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 66
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 1271-1291 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Conformational-energy calculations have been carried out in order to determine favorable packing arrangements within a group of α-helices. The influence of side chains and of the number of interacting α-helices on the mode of packing was analyzed. In this work, our earlier methods for computing the packing energy of a pair of α-helices [Chou, K.-C., Némethy, G. & Scheraga, H. A. (1984) J. Am. Chem. Soc. 106, 3161-3170] have been extended to treat the interactions among several helices. Also, new algorithms allow the matching of standard peptide geometry to x-ray coordinates of helical complexes and the analysis of interrelations between several helices. As a specific test case, the packing of three neighboring α-helices, viz., the A, G, and H helices of sperm whale myoglobin, was considered. Minimum-energy arrangements were computed for the separate A-H and the G-H α-helix pairs as well as for the A-G-H three-helix complex. For the packing of the nearly antiparallel G and H α-helices, the same optimal structure was obtained in two- and three-helix complexes, indicating that a single packing arrangement is specifically favored by interhelix interactions. For the pair of nearly perpendicular A and H α-helices, interactions are less specific, so that there is no unique optimal structure in the two-helix complex; in the three-helix complex, however, a specific mode of packing is favored even for the A-H pair. This result indicates that the presence of other nearby α-helices can influence the packing of a given α-helix pair. The computed arrangement of the A-G-H complex is very close to that of the crystallographically determined structure. These results can be used to make deductions about the likely sequence of events in protein folding, where, in this particular case, it appears that the G-H helix pair may form first and then induce proper orientation of the A helix.
    Zusätzliches Material: 4 Ill.
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  • 67
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 1337-1363 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Quantum-mechanical equations are derived that are particularly well suited to actual computations of the CD for helical polymers. They make use of cyclic boundary conditions and helical symmetry, so that only two matrices with a size equal to the number of transitions considered need be diagonalized. The final equations are expressed directly in terms of monomer properties and helical parameters to invite the same input as earlier calculations, and are given as a rotational strength times a shape function for ease of comparison with the earlier work. The shape of the helix term is expressed as a derivative with respect to ω and depends on the distance between monomers along the helix axis. Other terms involving two electric transition dipoles depend on the distance from the helix axis to the transition center. These equations are directly comparable to the classical equations derived for cyclic boundary conditions and helical symmetry. We present an outline of the derivation and enough intermediate steps to clarify how the equations arise.
    Zusätzliches Material: 2 Ill.
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  • 68
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 1385-1385 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
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  • 69
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 1479-1491 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The Raman and ir spectra of α-helical poly(L-glutamic acid) have been assigned on the basis of a normal mode calculation for this structure. The force field was based on our previously refined main-chain force constants for α-poly(L-alanine) and side-chain force constants for β-calcium-poly(L-glutamate). Despite the identical backbone α-helical structures, significantly different frequencies are calculated, and observed, in the amide III and backbone stretch regions of α-poly(L-glutamic acid), as compared with α-poly(L-alanine). This clearly demonstrates the influence of side-chain structure on mainchain vibrational modes.
    Zusätzliches Material: 2 Ill.
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  • 70
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 1501-1514 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The quasielastic light scattering method was used to study the ionic strength dependence of the mutual diffusion coefficient of sodium polystyrene sulfonate (NaPSS) as a function of NaCl and CaCl2 concentrations. The results indicate a splitting in the relaxation times that depends on the ratio Cp/Cs, where Cp and Cs are the polyion and added salt concentrations. A universal relationship taking into account Manning's theory of condensation and the Debye screening due to the added salt is proposed to characterize the fast-slow relaxation time transition.
    Zusätzliches Material: 5 Ill.
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  • 71
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 72
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 1573-1593 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A theory of the electrophoresis of DNA through gels with large interfiber spacing, such as dilute agarose, is presented. We assume that the DNA molecule moves along its axis through a “tube” in a neutral gel under the influence of the electric field. The tube is random except for possible bias due to the effects of the field. When the field is small, we easily recover the inverse-length dependence of the mobility found previously by de Gennes and by Doi and Edwards. At higher fields, a new effect appears; the tube becomes oriented because the field biases the direction of the leading end of the chain as it moves to form an extension of the tube. This leads to an increase of the mobility with increasing field by adding a field-dependent but length-independent term to the mobility expression. In agreement with experiment, we find that the field effect can be important at fields as low as 1 V/cm and that the effect can seriously decrease the sensitivity of the mobility to chain length. We also examine the fluctuation of the migration distance, the degree of orientation induced by the field, and the transient effects occurring when the feld direction is rotated by a right angle.
    Zusätzliches Material: 3 Ill.
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  • 73
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985) 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 74
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The confortmational behavior of the cholecystokinin-related fragments CCK4, CCK5, and CCK6 as determined by 1H-nmr spectroscopy in DMSO-d6 and water and fluorescence-transfer measurements in aqueous medium are greatly dependent on the ionization states of these peptides. Under netral conditions, the backbones of CCK5 and CCK6 preferentially adopted folded forms with a β-turn including the four residues Gly-Trp-Met-Asp, probably stabilized by a hydrogen bond between the CO of Gly and the NH of Phe. In these structures, possible induced by an ionic interaction between the carboxylic group of Asp32 and the NH3+ group of the N-terminal amino acid, the lateral chains of the various residues are quite distant from each other (15-16 Å). Under acidic conditions, extended structures without interactions between side chains predominate for CCK5 and CCK6, while for CCK4, a conformational change drawing the Trp and Phe side chains in close proximity was shown by fluorescence. The conformations observed in aqueous medium at physiological pH are discussed in relation to the biological activity of these peptides.
    Zusätzliches Material: 6 Ill.
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  • 75
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 1647-1662 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Thermally induced helix-coil transitions of myosin rod, light meromyosin, and tropomyosin were studied by optical rotatory dispersion (ORD). Fractional helicity was calculated from both the Moffitt-Yang parameter, b0, and the corrected mean residue rotation [m′] at 231.4 nm. Between 3 and 30°C, [m′] increases linearly with a slope of 59/°C, whereas b0 is virtually constant, indicating apparently different thermal melting behavior. Poly(L-lysine) and poly(L-glutamic acid) in their helical forms and myoglobin also show a nearly linear temperature dependence of [m′]231.4. Muscle proteins in 6M guanidine hydrochloride and the random-coil forms of the homopolymers exhibit temperature-dependent values of [m′]231.4 and b0. We conclude from these observations that ORD properties of both α-helices and random-coil polypeptides have significant intrinsic temperature dependencies. A new method of estimating fractional helicity as a function of temperature is proposed.
    Zusätzliches Material: 10 Ill.
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  • 76
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 77
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 2035-2040 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 78
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The conformation of phenylacetyl-D-alanyl-D-alanine in the crystalline state was characterized by Fourier-transform ir and Raman spectroscopy and was unambiguously solved by x-ray single-crystal determination. In the crystalline state, the molecule adopts a partially folded conformation quite similar to that of another cell wall peptide, acetyl-D-alanyl-D-alanine [Benedetti et al. (1981) J. Biol. Chem. 256, 9229-9234], although the crystal structure is stabilized by a quite different intermolecular hydrogen-bond pattern. No significant deviation from the usual trans-planar peptide group geometry was detected. The conformations accessible in the noncrystalline state were investigated by ir measurements in solution and conformational energy calculations. The theoretical study revealed that the peptide is a highly flexible molecule, since 55 minima were detected, within 3 kcal/mol, including the conformation found in the single crystal. The ir data for phenylacetyl-D-alanyl-D-alanine in different solvents were in accordance with virtually extended conformations, with some indication for weak, intramolecularly hydrogen-bonded C5-rings. These conformational data obtained for the cell wall peptide analog are compared with those known for penicillin G in the crystalline state.
    Zusätzliches Material: 7 Ill.
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  • 79
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 1863-1879 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Molecular mechanical calculations were done on complexes of ethidium cation with various base-paired deoxydinucleoside monophosphates [(ApT)2, (TpA)2, (A2 · T2), (GpC)2, (CpG)2, and (G2 · C2)] and deoxyhexanucleoside pentaphosphates [(ATATAT)2, (TATATA)2, (A6 · T6), (GCGCGC)2, (CGCGCG)2, and G6 · C6]. Relative binding energies, sequence preferences, and conformational aspects of the intercalation complexes were studied. The most detailed models used (an all-atom force field) gave results in good agreement with previous calculations and experimental work. Less-sophisticated models did not perform as well.
    Zusätzliches Material: 5 Ill.
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  • 80
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 1931-1940 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Transient photodichroism (TPD) data of Wang, Hogan and Austin [(1982) Proc. Natl. Acad. Sci. USA 79, 5896-5900] for methylene blue intercalated in nucleosomal DNA are reanalyzed using correct expressions for the twisting correlation functions of short DNAs. The data are found to rule out several models, including one in which the helix axis is constrained to girdle the equator of the sphere (representing a core particle) but the DNA is everywhere able to undergo twisting deformations and/or spinning around its local helix axis. However, when the ends of the DNA are rigidly clamped (against twisting/spinning) to the sphere, the same model gives an excellent fit to the data with suitable choices of parameters. From these and other observations, it is concluded that nucleosomal DNA must be rigidly clamped to the core particle at one or more points, although it is free to twist at most sites of binding of the dye. Moreover, if the dye is actually bound between two clamped points, then the torsional rigidity of DNA in the nucleosome is at least 2.5 times smaller than that of an ordinary linear DNA.
    Zusätzliches Material: 2 Ill.
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  • 81
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
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  • 82
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 1881-1897 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The configurational properties of an isotropically bendable wormlike chain have been investigated using a Monte Carlo approach. In particular, radial distributions for end-to-end separation, ring closure probabilities, and the angular correlation of the two ends of the chain have all been determined as a function of the contour length of the chain. The results of this analysis, when applied to the data of Shore et al. [(1981) Proc. Natl. Acad. Sci. USA 78, 4833-4837] for the length dependence of ring closure for doublehelical DNA, yields a value for the persistence length of DNA in remarkable agreement with earlier hydrodynamic studies.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
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  • 83
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 1909-1930 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Optical anisotropy data spanning a very wide time range are analyzed using a recently developed theory for filamentous macromolecules that can bend, twist, and also admit overdamped local libration (or wobble) of the chromophore. A rapid relaxation in the fluorescence polarization anisotropy (FPA) near 10-10 s is fitted well by superimposing isotropic wobble of the chromophore (7° rms polar and azimuthal amplitude) on the long-wavelength twisting and bending motions that characterize the relaxation at longer times but not by the latter alone. Moreover, the decay of the FPA from 0.5 to 150 ns cannot be satisfactorily fitted by chromophore wobble in an otherwise rigid DNA and must be assigned primarily to twisting, as noted previously.Data from 26 ns to 20 μs for 600 base-pair DNA are accurately fitted with only a single adjustable scaling factor when the tumbling correlation function is taken to be the empirical electric birefringence decay function of Elias and Eden. The Barkley-Zimm (BZ) tumbling correlation for very long filaments appears to decay too rapidly and results in significant overestimation of the depolarization for t ≤ 300 ns. In the range of the FPA experiments (t ≥ 150 ns), equally good fits with equally uniform torsion constants are obtained for long DNAs, whether one assumes the BZ tumbling correlation function or neglects tumbling entirely, but the best-fit torsion constant (actually the product of the torsion constant and friction factor) is increased by the factor 1.9 when the BZ result is used with a persistence length of a = 500 Å. The BZ bending theory is compared with other experimental data, and also with a simulation at very short times with mixed results. Present uncertainties regarding the tumbling dynamics and the friction factor for azimuthal rotation allow the torsion constant to be as much as 3.8 times larger than the initial estimate of Thomas et al. Apparent torsion constants obtained from relative ligase kinetics measurements are also briefly discussed.
    Zusätzliches Material: 6 Ill.
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  • 84
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 1981-1993 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Electric-field pulses of e.g. 20 kV/cm and 100 μs induce a strong decrease in the scattered light intensity of DNA condensed by spermine. Analysis of this effect demonstrates that the decrease of the scattered light intensity results from decondensation of DNA. The decondensation reaction requires an electric-field strength exceeding a threshold value. Complete decondensation can be achieved at field strength that are only slightly higher than the threshold value. The decondensation process is strongly accelerated at high electric-field strengths. At 30 kV/cm, the decondensation time constant is ∼8 μs, corresponding to an acceleation factor of 105 relative to the field-free decondensation reaction. The dependence of the time constants on the electric-field strength suggests that the field-induced decondensation is due to a dissociation field effect. The condensation process observed after electric-field pulses at low concentrations of DNA and spermine shows a characteristic induction period, which strongly depends on the spermine concentration. This induction period reflects the time required for the binding of spermine to DNA, until the degree of binding is sufficiently high for the condensation reaction. The fast dissociation of condensed DNA by electric-field pulses together with a relatively long lifetime of the free DNA results in a reaction cycle resembling a hysteresis loop.
    Zusätzliches Material: 5 Ill.
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  • 85
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985) 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 86
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 2041-2043 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 87
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 2057-2085 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A theory of adsorption of a polypetide chain capable of undergoing the coil-β-structure transition on a solid planar surface has been developed. The mutual influence of two order-disorder phase transitions, a conformational and an adsorption transition, was investigated. Various types of adsorption transitions are possible, depending on the initial conformational state (partly or completely β-structured) and the selectivity of adsorption: (a) the second-order phase transition, in which the chain is partly structured, both in adsorbed and desorbed states; and (b) the first-order phase transition, in which the chain exhibits a regular β-structure, at least on one side of the adsorption transition boundary. The chain bonding to the surface alters the degree of β-structure, both in the case of selective and nonselective adsorption (similar to the adsorption of the chains with other types of secondary structure). We show that the slope of the adsorption curves for partly β-structural chains increases as a result of an increase in the degree of β-structuring, and this effect is even stronger than the analogous effect of β-structuring.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
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  • 88
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Various copolypeptides were prepared by benzylamine or tertiary amine-initiated copolymerizations of alanine-N-carboxyanhydride (Ala-NCA) and valine-N-carboxyanhydride (Val-NCA). The number-average molecular weights of these copolypeptides were detemined by 1H-nmr spectroscopic end-group analyses and viscosity measurements. The sequences were characterized by 15N-nmr spectra in solution, and the average lengths of the homogeneous blocks were determined from the signal intensities. The 50.3-and 75.4-MHz 13C-nmr CP/MAS spectra of the solid copolypeptides are not sensitive to sequence effects, but allow qualitative and quantitative analyses of the secondary structures. In contrast to other methods, the 13C-nmr spectra allow determination of the extent to which individual amino acids are incorporated into β-sheet or α-helix phases. Depending on primary structure and molecular weight, the secondary structure of (Ala/Val) copolypeptides may vary significantly. Both monomer units may be predominantly helical or predominantly β-sheet structure, or the Val units may prefer the β-sheet structure with most Ala-units forming β-helices. However, these secondary structures are more or less thermodynamically unstable and revert to the stable conformations on reprecipitation from trifluoroacetic acid/water.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 89
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 2231-2242 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The intramolecular formation of multiple clusters of interacting helices has been characterized in a homopolymer. The configuration partition function permits the formation of clusters in which the number of interacting helices may be as large as the greatest integer in n/2, where n denotes the number of amino acid residues in the chain. The theoretical formulation has its origin in a recent [Mattice, W. L. & Scheraga, H. A. (1984) Biopolymers 23, 1701-1724], tractable matrix expression for the configuration partition function for intramolecular antiparallel β-sheet formation. Reassignment of the expression for one of the n(n+3)/2 elements in the sparse statistical weight matrix, along with a simple change in notation, converts that treatment into a matrix formulation of the configuration partition function for a chain containing multiple clusters of interacting antiparallel helices. The five statistical weights used are δ, fl, w, and the Zimm-Bragg σ and s. Each tight bend that connects two interacting helices contributes a factor of δ, fl is used in the weight for larger loops between interacting helices, and w arises from helix-helix interaction. The influence of the helix-helix interaction is well illustrated by two helix-coil transitions in a chain with n = 156 and σ = 0.001. In the absence of helix-helix interaction, the transition occurs by the nucleation and subsequent elongation of a small number of helices. When helix-helix interaction is attractive, the transition can occur by a different mechanism. Formation of a single pair of interacting helices is followed by addition of new helices to the initial cluster. In the latter process, individual helices experience relatively little growth after they are formed.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 90
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 2279-2299 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The low-energy conformations accessible to dCpdG modified at guanine N2 via trans epoxide opening by (+) and (-) 7β,8α-dihydroxy-9α,10α-epoxy-7,8,9,10-tetrahydrobenzo(a)pyrene (anti-BPDE) have been delineated by minimized semiempirical potential-energy calculations with all torsion angles flexible. Nearly 4000 trials were made, representing a fairly thorough investigation of the conformation space of the adducts. Carcinogen-base stacked states and base-base stacked conformers were found in the low-energy regions of both enantiomers. Many ω′, ω, ψ domains accommodate the two types of conformations, with B-like backbones among the most preferred states in each case. The conformational differences between the two enantiomers on the dimer level reside in subtle distinctions in orientation of the carcinogen-base linkage.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
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  • 91
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 2345-2356 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The temperature dependence of the composition of coacervate and equilibrium phases is examined for the polypentapeptide of elastin (L-Val1-L-Pro2-Gly3-L-Val4-Gly5)n in water. This provides for the development of a phase diagram. CD data is presented that provides information on associated polypeptide structure changes that, when added to previous CD, nmr, and dielectric relaxation data at lower water composition, allow construction of a phase-structure diagram of the polypentapeptide-water system. The molecular-weight dependence of phase change (coacervation) is included. The volume-composition studies as a function of temperature also provide temperature coefficients of expansion and of composition important in analyzing the mechanism of elasticity.
    Zusätzliches Material: 5 Ill.
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  • 92
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The proton magnetic resonance spectra of o-nitrophenylthio-tetra- and hexa-γ-benzyl-L-glutamate ethylamides have been measured at different concentrations in CDCl3 and CD22C1. The NH and α-CH resonances of the tetrapeptide show downfield shifts with increasing concentration, accompanying disappearance of their fine structure and line broadening. The apparent feature of chemical shifts against concentration is sigmoidal, and it can be interpreted by assuming the presence of a step or more of association-dissociation equilibria of tetrapeptide. With increasing concentration, small aggregates are formed by intermolecular hydrogen bonding, the size of which is not sufficiently large to exhibit critical micelle concentrations. In contrast to the tetrapeptide, the hexapeptide has constant chemical shifts of the NH and α-CH resonances, independent of concentration, which implies that only the unassociated molecules show observable sharp resonances. In the hexapeptide, the phenyl CH and benzyl CH2 groups of the side chains exhibit new resonances above certain critical concentrations, indicating the restriction of rotational freedom of the side chains in the aggregated states.
    Zusätzliches Material: 10 Ill.
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  • 93
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: We describe the solution (1H-nmr) and calculated conformations of the opiatelike peptide dermorphin and the analysis of structure-conformation-activity relationships in the series [Alan]-dermorphin. We used 1H-nmr spectroscopy to study dermorphin and its analogs [Alan]-dermorphin (with n = 1, 2…7) dissolved in dimethylsufoxide. Conformational energy calculations using semiempirical partitioned energy function methods were then carried out on dermorphin and its [L-Ala2]-analog. Agreement between calculation and experiment is satisfying, both suggesting predominance of a type I β-turn around Pro6-Ser7 at the C-terminus and of an extended structure in the central sequence Phe3-Gly4-Tyr5. Detailed analysis by step-by-step substitutions with Ala indicates that intraresidue interactions dominate over medium-range interactions (between adjacent residues), although the latter may also have a noticeable influence in shaping conformations. As a general feature, the effects of substitutions on the arrangement of side chains are always larger on the succeeding residue than on the preceding residue. Almost all the variations of activity observed in the analogs can be explained from conformational changes occurring in the aromatic side chains of the biologically important Tyr1, Phe3, and Tyr5 on substitutions effected on adjacent residues (fluctuations via medium-range interactions).
    Zusätzliches Material: 3 Ill.
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  • 94
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 2449-2468 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A detailed conformational analysis of polyoxyethylene-bound N-t-butyloxycarbonyl homo-oligo-L-glutamates up to the heptamer was carried out in CDCl3 solution using high-resolution 1H-nmr spectroscopy. Unequivocal assignments of resolved backbone NH and α-CH resonances were obtained with specifically deuterated oligomers. From nmr measurements, chemical-shift dependencies with respect to temperature and solvent, and the line-broadening effects of free radicals allowed the determination of hydrogen-bonded residues. The nmr data, along with model-building studies, suggest that seven-membered rings may exist in the N-terminal portion of these peptides. Replacement of the N-t-butyloxycarbonyl group by an acetyl or pyroglutamyl residue gave aggregated peptides, pointing to a special contribution by the Boc group to hydrogen bonding and solubility in CDCl3.
    Zusätzliches Material: 5 Ill.
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  • 95
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 2495-2510 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A detailed conformational analysis of homo-oligo-L-glutamates was carried out in aqueous solution using 1H-nmr spectroscopy. Three series of side-chain protected (α-OMe) glutamate oligopeptides, attached to polyoxyethylene (POE) to enhance their solubility, were synthesized. The effect of the N-terminal blocking groups - Boc, Ac, and pGlu - on the conformations of these peptides in water is discussed. Unequivocal assignments were obtained for all amide NH resonances through use of selectively α-deuterated oligo-glutamates. Analysis of vicinal coupling constants, temperature dependence of NH chemical shifts, transfer of saturation experiments, and titration studies with a denaturing solvent (DMSO) were used to investigate the peptide structure. These data suggest that the Glu1 and Glu2 NH protons of each heptamer are solvent exposed, while the NH protons of interior glutamate residues chain are solvent sequestered. The nmr data are consistent with the onset of helical structure at the heptamer of each series in aqueous solution. The POE-peptides with pGlu at the N-terminus showed considerably reduced stability of structure than those with the Boc or acetyl blocking groups. Peptide conformations and their stability in water are compared to those in other solvents.
    Zusätzliches Material: 5 Ill.
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  • 96
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 19 (1985), S. 31-31 
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 97
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 19 (1985), S. 69-76 
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 98
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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    Chemie in unserer Zeit 19 (1985), S. 86-94 
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 20 Ill.
    Materialart: Digitale Medien
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    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 19 (1985), S. 125-136 
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
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