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  • 101
    Digitale Medien
    Digitale Medien
    Application of band centrifugation to the study of the assembly of alfalfa mosaic virus (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 575-595 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A band-centrifugation method for the analysis of an assembly reaction of a simple virus from its RNA and protein is described. The experiment was carried out by sedimenting a band of viral RNA through a solution of depolymerized coat protein. The resulting radial distribution of the reaction products, followed as a function of time, was analyzed by a computer simulation of the series of reaction. This method is based on a numerical solution of the continuity equation for the sedimentation-diffusion process [Claverie, J.-M., Dreux, H. & Cohen, R. (1975) Biopolymers 14, 1685-1700; Cohen, R. & Claverie, J.-M. (1975) Biopolymers 14, 1701-1716]. A numerical method for the simulation of the chemical reaction is derived. From the simulated reaction series, equilibrium constants emerge for the successive addition of protein subunits to the growing nucleoprotein particle.The method is applied to the assembly of alfalfa mosaic virus. If the reaction between RNA and protein is carried out in 0.32M CsCl, pH 7.0, two stages during particle growth are resolved, each characterized by an equilibrium constant K. The determined values for K range from 5 × 105 to 3 × 106 l. mol-1. The existence of these two stages may have a structural implication in the assembly, as they likely represent an elongation and a termination stage. If the reaction is carried out under more favorable conditions (0.25M CsCl, pH 7.0), a kinetic constant of at least 105 l. mol-1 sec-1 is derived for each reaction step. Under these conditions the assembly appears to be completed within 1 min, which is too fast to detect distinct stages by band sedimentation.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.1980.360190310
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  • 102
    Digitale Medien
    Digitale Medien
    Characterization of molecular motions in 13C-labeled aortic elastin by 13C-1H magnetic double resonance (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 597-617 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Purified insoluble elastin samples labeled with [1-13C]valine, [1-13C]alanine, and [1-13C]-lysine were prepared from chick aorta in culture. The molecular mobility at the labeled sites was investigated using 13C-1H magnetic double-resonance spectroscopy. Linewidths, T1, and nuclear Overhauser effect (NOE) values of the labeled carbons alone were obtained from dipolar decoupled difference spectra. Analysis of these parameters together with signal intensity measurements showed that essentially all the valyl residues, ca. 75% of the alanyl residues, and ca. 60% of the lysyl residues were characterized by rapid backbone motions having τ = 65 nsec. Resonances due to the remaining alanyl and lysyl residues were detected in cross-polarization experiments, which enhance the signals of motionally restricted carbons. Since lysyl and alanyl residues are found in the crosslink regions of elastin, whereas valyl residues are not, we conclude that crosslinks rather than secondary structures in the extensible region of the protein are the main source of motional restrictions in the protein. Elastin chain mobility was monitored by linewidth measurements over the range -90 to +70°C. When the swelling solvent (0.15M NaCl) was fixed at 0.6 g/g of elastin, a rapid monotonic reduction in chain mobility was observed as the temperature was lowered from 50 to 5°C. Liquidlike mobility was completely lost at 5°C. In contrast, the same sample in contact with excess solvent retained its liquidlike molecular mobility until -13°C, where it abruptly became rigid. The molecular mobility of this sample was temperature insensitive in the physiologically interesting range, 20-40°C, as a consequence of the opposing influences of temperature and swelling. Taken together these nmr data indicate that under physiological conditions, elastin is a network of mobile chains whose motions are strongly influenced by protein-solvent interactions.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.1980.360190311
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  • 103
    Digitale Medien
    Digitale Medien
    Measurement of preferential solvation of some glucans in mixed solvent systems by gel-permeation chromatography (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 639-653 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Preferential solvation of the glucans amylose, pullulan, and dextran in binary dimethyl-sulfoxide/water (DMSO/H2O) solvent mixtures has been measured using gel-permeation chromatography. The preferential solvation behavior of the three glucans in DMSO/H2O solvent mixtures is indistinguishable in the experiments reported. In solvent mixtures with mol ratio DMSO/H2O less than 1:2, all three glucans are solvated preferentially by H2O. The maximum extent of preferential solvation by H2O is about 2.5 mol H2O/mol of glucose residues. When the DMSO/H2O mol ratio exceeds 1:2, DMSO solvates the glucans preferentially to a maximum extent of about 1 mol DMSO/mol of glucose residues. An interpretation of the change in preferential solvation with mixed solvent composition is suggested in terms of the known characteristics of the binary solvent system, and the relationship of preferential solvation, reported here, to the absolute solvation of the glucan chains is discussed.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.1980.360190313
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  • 104
    Digitale Medien
    Digitale Medien
    Electrical conductivity of single crystals of lysozyme (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 669-679 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The dc electrical conductivity of large single crystals of hen egg-white lysozyme has been measured. The samples were grown from aqueous solution and dried in air with silica gel. The temperature dependence of the conductivity obeyed the relation σ = σ0 exp(- ΔE/kT), with ΔE = 1.2 eV. The ΔE value agreed with most of the previous results for various proteins in the form of lyophilized powder. On the other hand, log σ0, being between 7 and 11, was much larger than the previously reported values and differed among the samples. An irreversible decrease in σ0, without affecting ΔE, was observed on heating the samples above 85°C. It was shown that the set of results can be explained if the charge carriers responsible for the observed conduction are regarded as protons, originating from residual water molecules. Photoresponse of the samples to uv radiation below 305-315 nm was also observed. Reproducible and reliable results were obtained relatively easily in the present experiments, which is thought to be the main advantage of using single-crystalline samples.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.1980.360190315
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  • 105
    Digitale Medien
    Digitale Medien
    Molecular-mechanics studies on d(CGCGAATTCGCG)2 and dA12·dT12: An illustration of the coupling between sugar repuckering and DNA twisting (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 2345-2376 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Molecular-mechanics calculations have been carried out on the base-paired deoxy dodecanucleoside undecaphosphates d(CGCGAATTCGCG)2 and d(A12)·d(T12). These refinements were carried out using the model-built Arnott B-DNA geometry as initial coordinates (with a helix repaeat of 10.0 residues/turn), as well as helix repeats ranging from 9 to 12 residues/turn. There was some variation in the optimum calculated helix repeat, depending on the dielectric model, the presence or absence of counterions, and the method used for inclusion for nonbonded interactions; the most interesting general result of these calculations was the coupling between furanose sugar puckering and twist. This coupling was observed for all models. With a helix repeat of 9.0 residues/turn, all sugars remain C(2′)endo after refinement; as the helix repear increases to 12.0 residues/turn, the number of sugars repuckering to O(1′)endo and C(3′)endo increases also. With our most rigorous model (i.e., a model with no cutoff distance for nonbonded interactions) and a helix repeat of 10.0 residues/turn, we find a greater tendency for pyrimidine than purine repuckering in d(CGCGAATTCGCG)2, in agreement with the x-ray structural data of Drew et al. [(1981) Proc. Natl. Acad. Sci. USA 78, 2179-2185].We also carried out a number of calculations in which we “forced” one of two deoxy sugars to repucker or one of the C3′-O3′-P-O5′ (ω) torsion angles to change from gauche- to trans using dihedral angle constraints. After the constraints were removed, some of these structures “reverted” to the sugar pucker of the initial structures, while others remained repuckered. In all cases, the energies for repuckered structures after refinement were very similar to energies of the initial structure. Experiments and theory suggest that local conformational fluctuations play an essential role in nmr relaxation of 31P and 13C atoms in double-helical DNA. The results of our previous calculations on hexanucleoside phosphates and the calculations presented there are consistent with an important contribution to nmr relaxation processes of conformational changes in the torsion angle ω′ from gauche- to trans and deoxy sugar repuckering from C(2′)endo to C(3′)endo. Specifically, the calculations presented here indicate a very flexible phosphate backbone in helixes having an intermediate helix repeat of 10 to 11 residues/turn. These helixes may accommodate sugars of variable pucker without significantly disrupting base-base hydrogen-bonding and stacking interactions. All of the variant structures are similar in energy, suggesting that conversion between them can occur on a nanosecond time scale, as observed in nmr relaxation experiments.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360211204
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  • 106
    Digitale Medien
    Digitale Medien
    Microwave absorption of DNA between 8 and 12 GHzSubmitted by M. L. Swicord in partial fulfillment of the requirements of the Ph.D. degree at the University of Maryland. (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 2453-2460 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The microwave absorption of aqueous solutions of DNA extracted from E. coli has been studied between 8 and 12 GHz by the use of an optical heterodyne technique. By measuring optically the temperature rise produced in an absorbing sample by pulsed microwave radiation, unambiguous, direct measurement of the microwave absorption is possible. Our results show that E. coli DNA absorbs microwaves in the 8-12-GHz region substantially more efficiently than water, which is itself an extremely efficient absorber. The observed absorption is featureless and decreases slightly with increasing frequency. These observations are consistent with an explanation involving direct absorption by longitudinal acoustic modes of the double helix.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360211209
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  • 107
    Digitale Medien
    Digitale Medien
    Transport properties and hydrodynamic centers of rigid macromolecules with arbitrary shapes (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 751-766 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A general formalism, which includes translation-rotation coupling, is proposed for calculating translational and rotational transport properties, as well as intrinsic viscosities, of rigid macromolecules with an arbitrary shape. This formalism is based on Brenner's theory of translational-rotational dynamics and on methods for the calculation of hydrodynamic properties that have been already presented, and can be regarded as a generalization of the one proposed by Nakajima and Wada. The calculated transport properties depend on the origin as predicted by Brenner's theory, but in a disagreement with him, the center of resistance and the center of diffusion do not coincide. As one can define several hydrodynamic centers, which in practice turn out to be located at different points, the influence of the choice of the center on the calculated transport properties is discussed. An analysis of the translation-rotation coupling effects in translational diffusion reveals that they arise exclusively from hydrodynamic interactions and are rather small in some cases of interest. Finally, we present a study of the rotational diffusion of rigid bent rods with a fixed length-to-diameter ratio. The diffusion coefficients obtained can be useful to estimate changes with respect to a straight rod.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.1980.360190404
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  • 108
    Digitale Medien
    Digitale Medien
    Polyelectrolyte complexes of glycol chitosan with some polysaccharides. I. Mixing ratio and dielectric properties (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 251-263 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The formation of polyelectrolyte complexes of glycol chitosan (GlChi) with sodium salts of dextran sulfate (DS), carboxymethyl cellulose (CMC), polygalacturonic acid (GalUA)n, and alginic acid (AlgA) has been studied. The number of ionizable groups per pyranose ring and the degree of dissociation as a function of pH in the polycation and polyanions have been determined using conductometric and potentiometric titrations. The formation of the complexes at different pH values has been followed by turbidity measurements. It is found that stoichiometric complexes of the polycation with CMC, (GalUA)n, and AlgA are formed at a mixing ratio of 0.5, indicating that the conformation may correspond to chains of equal lengths. In the case of the complex of GlChi with DS, the stoichiometric composition corresponds to a mixing ratio of 0.62. Thin transparent films of the complexes have been obtained by dehydration under reduced pressure on a layer of mercury. The dielectric constant ε′ and loss ε″ of thin films of these complexes have been measured in the range of frequencies of 1-100 kHz at different temperatures above and below room temperature. The GlChi-DS complex shows very little change in the values of ε′ and ε″ with frequency or temperature. On the other hand, films of GlChi-CMC and GlChi-(GalUA)n complexes show a significant increase in ε′ and ε″ as the temperature is increased above room temperature. The increase is more prominent at low frequencies. This behavior is attributed to the Maxwell-Wagner interfacial polarization. In the case of GlChi-AlgA film, the values of ε′ and ε″ increase enormously as the temperature increases. This behavior is similar to the increase in ε′ and ε″ observed by Michels et al. [(1965) J. Phys. Chem. 69, 1456-1465] as the salt concentration increases in another polyelectrolyte complex studied by them. The electric double-layer mechanism proposed by Schwarz [(1962) J. Phys. Chem. 66, 2636-2642] to account for the dielectric properties of biocolloids is shown to account quantitatively for the observations on the GlChi-AlgA film.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360210202
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  • 109
    Digitale Medien
    Digitale Medien
    Integriertes Organisches Praktikum. Von S. Hünig, G. Märkl und J. Sauer. Verlag Chemie, Weinheim 1979. XL VIII, 744 S., Abb. u. Tab., brosch. DM 59,- (1980)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 14 (1980), S. 72-72 
    Details
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/ciuz.19800140207
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  • 110
    Digitale Medien
    Digitale Medien
    Flüssiger Schwefel - ein Rohstoff komplizierter Zusammensetzung (1980)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 14 (1980), S. 73-81 
    Details
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/ciuz.19800140302
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  • 111
    Digitale Medien
    Digitale Medien
    Kleben und Klebstoffe (1980)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 14 (1980), S. 124-133 
    Details
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/ciuz.19800140404
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  • 112
    Digitale Medien
    Digitale Medien
    Methoden chemisch-kinetischer Berechnungen. Von H.-J. Bittrich, D. Haberland, G. Just. Verlag Chemie, Weinheim 1979. 217 S., 59 Abbildungen, 13 Tabellen, kart. DM 39, - (1980)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 14 (1980), S. 134-134 
    Details
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/ciuz.19800140406
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  • 113
    Digitale Medien
    Digitale Medien
    Chronik (1980)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 14 (1980), S. 176-176 
    Details
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/ciuz.19800140506
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  • 114
    Digitale Medien
    Digitale Medien
    Ethische Ziele und natur-wissenschaftliche Entwicklung. Probleme einer vernachlässigten Beziehung (1980)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 14 (1980), S. 168-175 
    Details
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/ciuz.19800140505
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  • 115
    Digitale Medien
    Digitale Medien
    Bioaktive Siliciumverbindungen (1980)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 14 (1980), S. 197-207 
    Details
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/ciuz.19800140605
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  • 116
    Digitale Medien
    Digitale Medien
    Organische Chemie. Von A. Streitwieser und C. H. Heathcock. Verlag Chemie, Weinheim, Deerfield Beach, Basel 1980. XXXI, 1490 S., 411 Abb., 132 Tab., geb. DM 98, - (1980)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 14 (1980), S. 209-209 
    Details
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/ciuz.19800140607
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  • 117
    Digitale Medien
    Digitale Medien
    Experiments in Environmental Chemistry. A Laboratory Manual. Von P. D. Vowles und D. W. Connell. Pergamon Press, Oxford, New York, Toronto, Sydney, Paris, Frankfurt 1980. VII, 102 S., Zeichn. u. Abb., kart. $ 9,95 (1980)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 14 (1980), S. 210-210 
    Details
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/ciuz.19800140609
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  • 118
    Digitale Medien
    Digitale Medien
    Masthead (1982)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 16 (1982) 
    Details
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/ciuz.19820160102
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  • 119
    Digitale Medien
    Digitale Medien
    NMR-Tomographie (1982)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 16 (1982), S. 35-45 
    Details
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 16 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/ciuz.19820160203
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  • 120
    Digitale Medien
    Digitale Medien
    Chronik (1982)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 16 (1982), S. 69-70 
    Details
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/ciuz.19820160207
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  • 121
    Digitale Medien
    Digitale Medien
    Kometen - Urmaterie unserer Welt (1982)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 16 (1982), S. 94-100 
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    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/ciuz.19820160305
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  • 122
    Digitale Medien
    Digitale Medien
    mini-chiuz (1982)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 16 (1982), S. A32 
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    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/ciuz.19820160308
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  • 123
    Digitale Medien
    Digitale Medien
    Röntgenstrukturanalyse von Molekülen IITeil I vgl. diese Zeitschr. 16, 71 (1982). (1982)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 16 (1982), S. 116-123 
    Details
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/ciuz.19820160405
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  • 124
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    Digitale Medien
    mini-chiuz (1982)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 16 (1982), S. A46 
    Details
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/ciuz.19820160409
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  • 125
    Digitale Medien
    Digitale Medien
    Johann Christian Bernhardt und die Vitriolsäure. Leben und Wirken eines (fast) unbekannten Arzt-Chemikers im 18. Jahrhundert (1982)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 16 (1982), S. 149-159 
    Details
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/ciuz.19820160504
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  • 126
    Digitale Medien
    Digitale Medien
    Adsorption of polypeptides on the solid surface. II. Effect of secondary chain structure and helix-coil transition (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 805-821 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The theory of adsorption of semistiff chains on a planar surface developed by the authors previously has been used to consider the helix-coil transition in single-stranded macromolecule interacting with an adsorbent plane. The cases of nonselective interaction when the adsorption energy is independent of the unit conformation (a) and selective interaction with only helical (b) or coiled (c) sequences active in adsorption were investigated. In case (b) the existence of secondary structure favors chain bonding to the surface. This leads to the increase in the stability of the helical state and complete polypeptide chain spiralization. The profile of the conformational helix-coil transition acquires an asymmetrical shape inherent to the second-order phase transition.In case (c) the bonding of a partially helical chain to the surface is similar to the adsorption of Gaussian coils and is accompanied by the destruction of secondary structure, this destruction being appreciable even if the helical state in space was favorable.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.1980.360190407
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  • 127
    Digitale Medien
    Digitale Medien
    Unwinding of DNA induced by fluorescein mercuric acetate (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 991-999 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Fluorescein mercuric acetate causes the unwinding of DNA and binds to the separated bases. This unwinding process can be followed by measuring absorption changes of this reagent. For untreated calf thymus DNA, the initial rate was very slow, and the shape of the kinetic curve was sigmoidal. When double-strand breaks of DNA were produced by DNase II treatment or sonication, the initial rate increased and the sigmoidal character disappeared. The initial rate was shown to be proportional to the concentration of helix ends. From this relation the rate of unwinding was estimated to be 2.0 base pairs/sec at 1.0 × 10-5M fluorescein mercuric acetate and 25°C. DNase I treatment, which produces single-strand breaks and a smaller number of double-strand breaks, also increased the initial rate. However, this increase was due only to the double-strand breaks, that is, single-strand breaks had no significant effect on the initial rate. Also, uv irradiation increased the initial rate linearly with uv dose, at least up to 2 × 105 erg/mm2, suggesting that this increase is due to photoproducts other than usual pyrimidine dimers. We discuss the usefulness of this kinetic method in structural studies of DNA.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.1980.360190505
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  • 128
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    Digitale Medien
    Circular dichroism of nucleic acid monomers. I. Calculated adenosine and 2′-deoxyadenosine CD spectra (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1017-1038 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A combination of the DeVoe and Kirkwood polarizability concepts is developed to calculate CD spectra of nucleic acid monomers. The method is perfectly general and applies to any system where the constituents have absorption properties which are widely separated in terms of frequency. The theory is applied to calculate the CD spectra of adenosine and 2′-deoxyadenosine conformers. Bond polarizabilities are evaluated for the ribosyl moiety of adenosine, as a function of glycosidic rotational angles and polarizability anisotropies. It is found that a wide range of C-C and C-O bond polarizabilities give similar CD results. Isotropic atom polarizabilities are also evaluated. It is found that the CD results using these polarizabilities do not differ significantly from those obtained with bond polarizabilities. The CD spectra of adenosine and 2′-deoxyadenosine are calculated for three x-ray diffraction determined geometries: A-form RNA, B-form DNA, and C-form DNA. The results indicate that the monomer CD spectra are strongly dependent on the precise geometry and appear to be of importance in understanding the spectra of oligomers and polymers. The deoxyadenosine conformers are found to have calculated CD spectra which are less intense than those of the ribosyl conformers. These results indicate that the measured differences between the CD magnitudes of ribo- and deoxyriboadenosine are due to the presence or absence of the 2′-hydroxyl. Weighted averaged adenosine CD spectra are calculated with the aid of probability distributions from conformational energy calculations. The results suggest a new method for obtaining empirical monomer parameters for use in optical calculations. The calculations in this paper indicate for the first time that DeVoe theory, in combination with the Kirkwood theory, provides a useful method for the calculation of the CD spectra of nonpolymeric molecules.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.1980.360190507
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  • 129
    Digitale Medien
    Digitale Medien
    β-Chain conformation of the high-sulfur proteins from wool (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1093-1097 
    Details
    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
    URL: http://dx.doi.org/10.1002/bip.1980.360190512
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  • 130
    Digitale Medien
    Digitale Medien
    Calorimetric determination of the enthalpy of ionization of oxidized and reduced horse heart cytochrome c (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 899-911 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The heats of ionization of protons, ΔHi, of oxidized and reduced horse heart cytochrome c in 0.15M KCl at 20°C were determined using a titration calorimeter which simultaneously afforded the potentiometric titration curve. Reproducibility of the thermal titrations is within 2%, and evaluation of the heats observed after the heat loss corrections is estimated to be within 5%. A single titration of oxidized cytochrome c from pH 11 to 3 is in excellent agreement with the thermal titration of this protein obtained with flow calorimetry. The thermal titration, however, is not reversible, due in part to the loss of titratable group(s) in this pH region and to the heat contribution of the acid and alkaline conformational changes which occur. Although of lesser magnitude, the reduced form also indicates similar thermal transitions. These differences are due solely to conformational contributions to the thermal process, since the potentiometric curves are reversible. The nature of the irreversibility for oxidized cytochrome c appears to involve the loss of a group with pK′ 8.9 and the shift of two groups from pK′ 5.6 to 4.8. Thermal difference curves for this process indicate that heats of -7.8 and -24.1 kcal/mol are liberated which are centered at pH 9.3 and 3.9, respectively.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.1980.360190413
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  • 131
    Digitale Medien
    Digitale Medien
    Syn-anti equilibrium of purine bases in dinucleoside monophosphates as studied by proton longitudinal relaxation (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1211-1239 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The preferential orientations of the purine bases in dinucleoside monophosphates such as ApA, ApG, and GpA in 10-2M neutral aqueous solutions have been investigated by proton relaxation at 250 MHz. These orientations are deduced from computer simulations of the magnetization recovery curves following a 180° nonselective pulse. The distances between the H(8) proton of a base and the ribose ring protons which are used in these calculations are obtained by minimization as a function of the glycosyl torsion angle ϒ of the standard deviation between the isotropic reorientation correlation times τR derived from the relaxation rates of these protons. The average H(1′) - H(8) distance obtained by this procedure may be readily verified from the reduction of the H(1′) relaxation rate when H(8) is substituted by a deuteron. The limits of validity of the assumption of a single correlation time τR governing the proton relaxation have been estimated, taking into account several possible internal motions, e.g., the rotation of the base, of the methylene exocyclic group and the N ⇄ S interconversion of the ribose ring. For 10-10 〈 τR 〈 2 × 10-10 sec, it appears that the influence of these motions on the proton relaxation becomes perceptible when the jump rates among equilibrium positions exceed ca. 109 sec-1.The whole of the experimental results show that for the ribose ring N conformer, the orientation of the bases is found in the ranges 60° 〈 ϒ 〈 80° (syn) and 180° 〈 ϒ 〈 210° (anti). For ribose S conformer, it is observed that this orientation is mainly syn with 5° 〈 ϒ 〈 90°. The average H(1′) - H(8) distance provides semiquantitative information on the overall syn or anti orientations of the base in each nucleoside moiety. At 298 K the population of the anti conformer is found to increase in the order A- pG 〈 Ap-G ∼ Gp-A 〈 Ap-A 〈 A-pA 〈 G-pA. A more detailed analysis of relaxation data shows that the maximum possible fraction of the stacked form of dinucleotides, due to the occurrence of N-anti conformers in both nucleoside moieties, is in the order ApG 〈 GpA 〈 ApA, in agreement with previous works, with however smaller values.Lastly the deuteron linewidth in position 8 of the bases indicates a syn-anti transition rate of the order of 109 sec-1 at room temperature, without noticeable effects therefore on the proton relaxation.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.1980.360190608
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  • 132
    Digitale Medien
    Digitale Medien
    Effect of counterions on complex coacervation (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1289-1298 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: In a recent paper, we developed a thermodynamic theory on the complex coacervation in the absence of low molecular ions, under the assumption that the coacervation is a condensation phenomenon of aggregates of polyanion and polycation in the aqueous solution, by obtaining the interaction potential US between these aggregates on the basis of Flory's method. In this paper, we have extended the theory to a more complicated phenomenon of the counterion-containing solutions. This treatment has led the interaction potential having an additional contribution to US resulting from an entropy increase by the counterion distribution. The phase diagram between solution (sol) and separated phase has been obtained as a function of the difference of charges between polyanion and polycation. It has been found that the presence of counterions sensitively suppresses the coacervation.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.1980.360190705
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  • 133
    Digitale Medien
    Digitale Medien
    Dielectric relaxation of DNA solutions. IV. Effects of salts and dyes (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1039-1047 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The effects of salts (NaCl, LiCl, Me4NCl, AgNO3, MgCl2, CuCl2 and MnCl2) and dyes (acridine orange and methylene blue) on the low-frequency dielectric relaxation (0.1 Hz-30 kHz) of dilute aqueous solutions of DNA were investigated with varying salt or dye concentrations. Both the dielectric relaxation time τD and the rotational relaxation time τ estimated from the reduced viscosity decrease in quite parallel ways with increasing M/P (M/P being the normality ratio of cation to phosphate residue), reflecting the contraction of DNA molecule due to electrostatic shielding and cation binding. The agreement between τD and τ through the whole range of M/P supports our previous conclusion that the low-frequency relaxation of DNA arises from rotation of the molecule. The dielectric increment Δε also decreases with increasing M/P on account of both the contraction of DNA and the decrease in effective degree of dissociation of DNA. Δε as a function of M/P is interpreted in terms of a quasi-permanent dipole due to counterion fluctuation. These effects of cations are the strongest for divalent cations and rather weak for Na+, Li+, and Me4N+. Effects of dye on τD and Δε are also well explained by the rotation of DNA molecule with a quasi-permanent dipole due to counterion fluctuation on the basis of intercalation of dye at D/P 〈 0.2 (D/P being the molarity ratio of dye to phosphate residue) and external binding at 0.2 〈 D/P 〈 1.0.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.1980.360190508
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  • 134
    Digitale Medien
    Digitale Medien
    Models for boundary effects on molecular rotation in membranes (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1597-1602 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Rotational and wobbling diffusion coefficients for spherical and long-chain molecules in membranes are calculated using a simple hydrodynamic model. Estimates of the contributions to the diffusion coefficients arising from hydrodynamic interactions between molecules and membrane interfaces are obtained and found to be small. For molecules containing polar head groups, we show that the presence of a membrane interface can produce a significant reduction in the wobbling diffusion coefficient over what would be obtained in an isotropic fluid.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.1980.360190904
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  • 135
    Digitale Medien
    Digitale Medien
    Cation effects on the nonlinear electrical properties of DNA solutions (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1629-1640 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The nonlinear electrical properties of DNA solutions were measured when different monovalent cations were added to DNA. The influence of different parameters has been examined: fundamental frequency, field strength, and concentration. A linear relationship between the harmonic current Ih and the DNA concentration is shown, even for higher concentration values (400 mg/l.). The frequency dispersion of Ih has the same shape for all the cations and the low-frequency amplitude of Ih increases in the following order: Li+ 〈 Na+ 〈 K+ 〈 NH4+ 〈 Cs+. The nonlinear polarizability values are compared with the linear ones determined using the very low field electric birefringence technique. Both linear and nonlinear values are of the same order of magnitude. It is thought that the nonlinear electrical property of high-molecular-weight DNA mainly results from the deformation of the DNA coils by the electric field.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.1980.360190907
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  • 136
    Digitale Medien
    Digitale Medien
    Dependence of the internal relaxation time for DNA on salt type as inferred by quasielastic light scattering (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1655-1666 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Quasielastic light scattering methods were used to study calf thymus DNA in solutions of LiCl, NaCl, NH4Ac, and NH4Cl. Plots of the reciprocal relaxation time (1/τ) vs sin2(θ/2), where θ is the scattering angle, exhibit two linear regions, in accordance with theories for semiflexible polymers based on the t → 0 approximation. In these theories the slope of the linear region at low angles is associated with the translational diffusion coefficient (Dt), whereas the slope of the linear region at high angles is associated with the segmental diffusion coefficient (Ds = kT/ƒs). The midpoint of the “transition” between these two linear regions is associated with the mean displacement between segments (b). Data presented here indicate that the Rouse-Zimm parameters b and ƒs are significantly different for DNA in 0.4M NH4Cl relative to the other salts at comparable ionic strengths. It is suggested that this difference reflects local solvent structure and that both b and Ds are sensitive to the local water structure.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.1980.360190909
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  • 137
    Digitale Medien
    Digitale Medien
    Microscopic persistence length of native DNA: Its relation to average molecular dimensions (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1689-1694 
    Details
    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
    URL: http://dx.doi.org/10.1002/bip.1980.360190912
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  • 138
    Digitale Medien
    Digitale Medien
    Effect of some monohydric alcohols on the oxygen affinity of hemoglobin: Relevance of solvent dielectric constant and hydrophobicity (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1703-1703 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.1980.360190914
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  • 139
    Digitale Medien
    Digitale Medien
    Masthead (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980) 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.1980.360191001
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  • 140
    Digitale Medien
    Digitale Medien
    Sodium counterion activity of poly(S-carboxymethyl-L-cysteine) and the beta-random-coil transition (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1743-1752 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Sodium ion activity was measured using a Na-glass electrode in a solution of poly(S-carboxymethyl-L-cysteine) with no added salt at various degrees of neutralization and various concentrations for samples of different molecular weights. The conformational change from random coil to the β-structure was detected from the activity coefficient of counterions, as well as from CD. At a constant degree of neutralization, the activity coefficient is insensitive to a concentration change not only in the random-coil state, but also in the range of conformational change if the concentration is below about 3 × 10-2 monomolal. At high concentrations of about 5 × 10-2 monomolal, however, the activity coefficient becomes low, probably due to the occurrence of the stacking of the pleated sheets.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.1980.360191005
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  • 141
    Digitale Medien
    Digitale Medien
    1H-nmr study of protected methionine homo-oligopeptides in helix-supporting environment (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1791-1799 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: 1H-nmr spectra for a series of Boc-L-(Met)n-OMe (n = 2-9) homo-oligopeptides have been observed in the helix-supporting solvent trifluoroethanol (TFE) at millimolar concentrations. Interfering solvent peaks were eliminated using two decoupling frequencies to selectively remove the methylene and hydroxyl protons of the solvent. Comparisons with specifically α-deuterated homo-oligopeptides gave complete assignments of the NH region of the Boc-Metn-OMe oligomers up to the heptapeptide. Analysis of chemical shifts, coupling constants, and temperature dependence of chemical shifts suggests that up to the hexapeptide, similar structures exist in deuterochloroform and TFE. In contrast, nmr parameters at the heptapeptide for several internal residues differ in these solvents. These results suggest that a C7 to α-helix transition may occur in TFE as the chain length of the methionine oligopeptides increases.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.1980.360191008
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  • 142
    Digitale Medien
    Digitale Medien
    Use of natural-abundance 15N-nmr spectroscopy to investigate the secondary structure of peptides: Gramicidin S (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1815-1826 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The natural-abundance 15N-nuclear magnetic resonance (nmr) spectrum of the cyclic decapeptide gramicidin S has been measured and assigned in the solvents dimethyl sulfoxide, methanol, and 2,2,2-trifluoroethanol. Three methods have been investigated to distinguish between peptide groups which are exposed to or shielded from the solvent. The solvent dependence of the 15N chemical shift is correlated with the two types of peptide group in gramicidin S—those with the carbonyl group exposed or shielded from the solvent. The second method monitors the lability of the N—H proton (via the collapse of the reduced 15N-1H coupling) in the presence of added base used to promote intermolecular exchange - peptide protons shielded from the solvent exchange more slowly. The third method looks at the temperature dependence of the 15N chemical shifts in dimethyl sulfoxide. Here the data are not so distinctive as to allow the differentiation between solvent-exposed or shielded N—H bonds at all peptide groups.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.1980.360191010
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  • 143
    Digitale Medien
    Digitale Medien
    Modification of the apparent radius of gyration of cytochrome c by the distribution of counterions in solution (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1887-1897 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Small changes in the apparent radius of gyration of native cytochrome c were measured as a function of pH in solutions of 0 and 50 mM ruthenium hexicyanide. The forward scattering was also measured as a function of pH under the same conditions to ascertain the contribution of the Ru ion shell to the forward scattering and concomitantly to the radius of gyration. The forward scattering and small alterations in the radius of gyration were then measured as a function of Ru counterion concentration. These results are then interpreted in terms of the mechanisms which influence the measured apparent radius of gyration. It is shown that the Debye-Hückel theory of counterion distributions can be used to describe the data in situations where scattering from the bound Ru ions contributes less significantly than scattering from the ion cloud.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.1980.360191015
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  • 144
    Digitale Medien
    Digitale Medien
    Masthead (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980) 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.1980.360191101
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  • 145
    Digitale Medien
    Digitale Medien
    Fluorine nmr studies of poly(N-acryloyl-β-alanine)-α-chymotrypsin conjugates (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1827-1837 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Fluorine nmr experiments carried out at 51.0 and 94.1 MHz have been used to explore the interaction of the probe molecule p-fluorocinnamate with conjugates formed from α-chymotrypsin and poly(N-acryloyl-β-alanine). The data obtained include enzyme-induced chemical-shift effects, spin-lattice (R1) and transverse (R2) relaxation rates, and the rate constant for dissociation of the fluorocinnamate-enzyme complexes. Analysis of the results indicates that while overall molecular tumbling of the enzyme molecule is not greatly changed by attachment of polymers of various sizes, conjugated polymer can appreciably affect the structure of the p-fluorocinnamate binding site. The important variable involved in such structural changes appears to be the amount of polymer present per mole of protein.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.1980.360191011
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  • 146
    Digitale Medien
    Digitale Medien
    Concentration distribution and spatial moments of moving macromolecules undergoing isomerization (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1875-1886 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Expressions for zeroth, first, and second spatial moments are obtained for diffusing macromolecules A and B that move due to an external field and undergo reversible isomerization, switching back and forth according to first-order kinetics. In addition, expressions for third and fourth moments are derived for the special case of equal diffusion coefficients, equal rate constants, and equal but opposite velocities. The initial conditions are arbitrary amounts of A or B concentrated in an infinitesimally narrow region. The moments are computed from derivatives of the Fourier-transformed concentration profiles of A and B. The moments are used in an expansion in term of Hermite polynomials, the Gram-Charlier expansion, to construct the concentration profiles of A or B or A and B together. The examples presented show that a few terms of the expansion, for which explicit expressions are given, can give tolerable accuracy if the velocity is not too large and the rate constants and diffusion coefficient are not too small. The expansion can be used to determine when the profiles are unimodal.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.1980.360191014
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  • 147
    Digitale Medien
    Digitale Medien
    Triple helix-coil transition of covalently bridged collagenlike peptides (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1909-1917 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The thermal triple helix-coil transition of covalently bridged collagenlike peptides with repeating sequences of (Ala-Gly-Pro)n, n = 5-15, was studied optically. The peptides were soluble in water/acetic acid (99:1) and were found to form triple-helical structures in this solvent system beginning with n = 8. The thermodynamic analysis of the transition equilibrium curves for n = 9-13 yielded the parameters ΔH°s = -7.0 kJ per tripeptide unit, ΔS°s = -23.1 J deg-1 mol-1 per tripeptide unit for the coil-to-helix transition, and the apparent nucleation parameter σ ≃ 5 × 10-2. It was suggested through double-jump temperature experiments that the rate-limiting step during refolding is not only influenced by the difficulties of nucleation, but also by cis-trans isomerization of the Gly-Pro peptide bond.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.1980.360191017
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  • 148
    Digitale Medien
    Digitale Medien
    Experimental characterization of poly(hydroxyalkyl-L-glutamine) conformations in aqueous calcium chloride and sodium perchlorate solutions (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1923-1941 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Poly(hydroxyalkyl-L-glutamine) (alkyl = ethyl, propyl, butyl) solutions have been studied by CD as functions of temperature and activity of calcium chloride and sodium perchlorate. Helical content is altered by changes in salt activity and temperature. The helicity of poly(hydroxybutyl-L-glutamine) and poly(hydroxypropyl-L-glutamine) falls to zero in a monotonic fashion with increasing calcium chloride activity. A nonzero helicity reappears at activities in excess of 5-50 mol kg-1. Poly(hydroxypropyl-L-glutamine) is much more sensitive to calcium chloride than is poly(hydroxybutyl-L-glutamine), and both polypeptides are more sensitive to calcium chloride than are typical proteins. Markedly different behavior is observed with sodium perchlorate. This salt acts as a helix stabilizer at low activities but becomes a destabilizer at activities higher than 0.3-1.0 mol kg-1. In this respect the effect of sodium perchlorate on nonionic poly(hydroxyalkyl-L-glutamines) resembles that seen with cationic poly(L-lysine) and poly(L-arginine). Helix stabilization at low sodium perchlorate activity is moderate for poly(hydroxybutyl-L-glutamine) and large for poly(hydroxypropyl-L-glutamine) and poly(hydroxyethyl-L-glutamine).
    Zusätzliches Material: 16 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.1980.360191102
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  • 149
    Digitale Medien
    Digitale Medien
    Influence of uracil photohydrate formation on the conformational properties of heterodinucleoside monophosphatesA preliminary account of some of this work was presented at the 21st Annual Meeting of the Biophysical Society, New Orleans, Louisiana; Symposium abstracts in Biophys. J. (1977) 17, 223a. (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1983-2002 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The structural properties of uracil photohydrates at the monomer and dimer level in aqueous solution have been examined in detail by nmr spectroscopy. Based on such evidence, the absolute configurations of the two possible diastereomers have been assigned, and the conformational perturbations induced by photohydration have been evaluated. In all instances, photohydration shifts the 2E ⇌ 3E puckering equilibrium of the sugar ring of the uridylyl fragment towards 2E (from 12-18%). In addition, for both dimers examined in detail, ho6UpA and Apho6hU, the effect of dimerization on sugar pucker is such that the 3′-terminal unit shows a clear increase in the percentage of 3E (relative to the appropriate 5′-mononucleotide), whereas the percentage 3E of the 5′-terminal unit shows no change. This is contrary to the findings in the normal dinucleoside monophosphates, where an increased preference for 3E pucker occurs in both residues on dimerization and increased base stacking. Significant base-base interactions were observed in both hydrated dimers despite the loss of the planar π-system in the uracil fragment. In addition, the rate of photohydration for a particular dimer pair (e.g., ApU and UpA or GpU and UpG) is shown to be inversely dependent on the amount of base stacking in the parent dimer. This latter parameter has also been correlated with the ratio of the two possible diastereomers formed in the reaction and is associated with a preferential attack at one face of the pyrimidine base ring. The shift of the sugar puckering equilibrium towards 2E has been compared with similar shifts observed when adenosine and guanosine are methylated at N(1) and N(7), respectively. The possible biological significance of the above-mentioned conformational aspects is discussed.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.1980.360191105
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  • 150
    Digitale Medien
    Digitale Medien
    Helix-coil transitions in a simple polypeptide model (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 2033-2045 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A simplified model of a polypeptide chain is described. Each residue is represented by a single interaction center. The energy of the chain and the force acting on each residue are given as a function of the residue coordinates. Terms to approximate the effect of solvent and the stabilization energy of helix formation are included. The model is used to study equilibrium and dynamical aspects of the helix-coil transition. The equilibrium properties examined include helix-coil equilibrium constants and their dependence on chain position. Dynamical properties are examined by a stochastic simulation of the Brownian motion of the chain in its solvent surroundings. Correlations in the motions of the residues are found to have an important influence on the helix-coil transition rates.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.1980.360191108
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  • 151
    Digitale Medien
    Digitale Medien
    Electric dichroism and birefringence of poly(ribocytidylic acid). I. Optical properties and stability (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 2123-2132 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Measurements of the uv absorption and melting profiles of poly(rC) at low-salt conditions confirm the existence of a double-stranded complex at low pH and imply, but do not prove, the structure proposed by Akinrimisi et al. (1963) Biochemistry 2, 340-343. Electric dichroism and birefringence provide additional supporting evidence and indicate that the complex is one in which the bases are tilted considerably from the major molecular axis. The base-stacking tendency of single-stranded poly(rC), unlike poly(rA), is found to be insufficient to maintain a rodlike structure; the persistence length of stacked bases in poly(rC) must be very small. The existence of an out-of-plane transition in poly(rC) in the vicinity of 300 nm is conclusively demonstrated by both dichroism and birefringence measurements.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.1980.360191112
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  • 152
    Digitale Medien
    Digitale Medien
    Study of the influence of NH⃛S hydrogen bonds on the reduction potential in Clostridium pasteurianum 2(4Fe-4S) ferredoxin using deuterium exchange (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 2133-2141 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The effect of deuterium substitution of exchangeable hydrogen atoms on the reduction potential of Clostridium pasteurianum 2(4Fe-4S) ferredoxin has been studied. The studies were conducted to determine if NH⃛S hydrogen bonds to the iron-sulfur cluster are dominant in the mechanism of influence of the protein on cluster reduction potential, as has been proposed [Carter, C. W. (1977) J. Biol. Chem. 252, 7802-7811]. Deuteration of the slowly exchangeable hydrogen atoms, however, yields essentially no shift in the reduction potential (-0.2 ± 0.8 mV), suggesting that NH⃛S bonds are not important modifiers of cluster reduction potential in this protein.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.1980.360191113
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  • 153
    Digitale Medien
    Digitale Medien
    Kinetics of reactions involving DNA containing stress-induced single-stranded regions (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 2143-2164 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The theoretical kinetics are analyzed for reactions between torsionally stressed DNA and another compound which reacts at different rates with portions of the substrate molecule which are in different conformational states. These reactions are assumed to obey Michaelis-Menten kinetics, so no cooperative effects occur. The DNA is regarded as being susceptible to a stress-induced local conformational transition as described recently by Benham. Briefly, alterations in torsional stress consequent on superhelicity effectively change the relative concentrations of the two conformational states of the substrate, thereby influencing the course of the reaction. This theory is developed for transition between the B-form helix and the single-stranded, random-coil states. To illustrate the influence of posited stress-induced melting on kinetics, calculations are made on simple models of two biochemical phenomena. First, the variations in initial nicking rates of single-strand-specific endonucleases with substrate superhelicity are interpreted as arising from changes in the concentration of (stress-induced) single-stranded binding sites. Second, the observed dependence of the transcription rate of RNA polymerase core enzyme on substrate superhelicity is interpreted in terms of a model in which the rate-limiting step in the initiation event is the formation of a complex between the enzyme and a single-stranded region. Related experimental results are shown to be qualitatively consistent with the suggestion that sufficiently supercoiled DNA contains locally melted regions.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.1980.360191202
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  • 154
    Digitale Medien
    Digitale Medien
    A theory for polarized fluorescence microscopy of chromosome structures (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 2267-2267 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.1980.360191209
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  • 155
    Digitale Medien
    Digitale Medien
    Melting experiment concerning the topological structure of closed circular double-stranded DNA (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 117-129 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A melting experiment was performed on the whole set of populations of the replicative form of φX174 DNA, which can be obtained treating this DNA with rat liver nicking-closing enzyme in the presence of ethidium bromide. Gel electrophoresis performed by loading the DNA samples at neutral and alkaline pH allows separation of these populations in discrete sets of bands, which can then be compared. The outcome of the experiments indicates that in the range of electrophoretic mobilities which can be explored, no band is formed exclusively by circular complementary strands which can be separated by alkaline denaturation. These results are compared with what would be expected if double-stranded closed circular DNA had structures other than the canonical double helix. Under nonrestrictive hypotheses, the experiments reported allow one to obtain a minimum estimate of the absolute value of the linking number of a closed circular double-stranded DNA: for native φX174 RF DNA, the linking number appears to be greater than 12 (in absolute value). Some data on the electrophoretic mobility of denatured closed circular duplexes are reported, which still wait for a physicochemical interpretation.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360210110
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  • 156
    Digitale Medien
    Digitale Medien
    Conformations of cyclic peptide/calcium complexes in solution (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 169-179 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Synthetic cyclic octapeptides of general structure cyclo[Glu(γOBzl)-Sar-Gly-(N-R)Gly]2 (R = n-hexyl and cyclohexyl) transport calcium ions selectively across organic phases and phospholipid membranes. We have now used proton nmr spectroscopy (360 MHz) to study the solution conformation(s) of their calcium complexes. When Ca(ClO4)2 was added to solutions of these peptides in CDCl3, nmr spectra of the resulting calcium complexes were characteristic of a single C2-symmetric conformer. From a Karplus-Bystrov analysis of vicinal coupling constants in both the peptide backbone and Glu side chain (treated as an ABCC′MX spin system), in conjuction with model-building studies, a structure was proposed in which the calcium ion is bound in an octahedral-type complex by the four (coplanar) carbonyl groups of the (all-trans) Glu-Sar and Gly-(N-R)Gly peptide bonds. Occurrence of preferred rotamers about Glu side chain Cα-Cβ bonds indicated that restricted rotation in peptide side chains arises upon calcium binding.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360210114
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  • 157
    Digitale Medien
    Digitale Medien
    Proton transfer and polarizability of hydrogen bonds formed between cysteine and lysine residues (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 25-42 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: (L-Cys)n + N-base systems and (L-Cys)n + (L-Lys)n systems were studied by ir spectroscopy. It is shown that in the water-free systems, SH⃛N ⇌ S-⃛H+N hydrogen bonds are formed. With the (L-Cys)n + N-base systems, both proton-limiting structures in the SH⃛N ⇌ S-⃛H+N bonds have equal weight when the pKa of the protonated N-base is 2 pKa units larger than that of (L-Cys)n. The same is true with the water-free (L-Cys)n + (L-Lys)n system. Thus, with regard to the type of proton potentials present, these hydrogen bonds are proton-transfer hydrogen bonds showing very large proton polarizabilities. This is confirmed by the occurrence of continua in the ir spectra. Small amounts of water open these hydrogen bonds and increase the transfer of the proton to (L-Lys)n. In the (L-Lys)n + N-base systems, with increasing proton transfer the backbone of (L-Cys)n changes from antiparallel β-structure to coil. In (L-Cys)n + (L-Lys)n, the conformation is determined by the (L-Lys)n conformation and changes depending on the chain length of (L-Lys)n. Finally, the reactivity increase in the active center of fatty acid synthetase, which should be caused by the shift of a proton, is discussed on the basis of the great proton polarizability of the cysteine-lysine hydrogen bonds.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360210104
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  • 158
    Digitale Medien
    Digitale Medien
    Influence of ionic strength on the dichroism properties of polynucleosomal fibers (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 101-116 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: We report electric-dichroism and electron-microscopic studies of chromatin fibers fixed by protein-protein crosslinking at salt concentrations ranging from 10 to 100 mM. The results confirm a progressive disorganization of the fiber as the salt concentration is lowered. The positive dichroism and large polarizability anisotropy characteristic of the 300-Å diameter fiber found in 100 mM salt are replaced by negative dichroism and smaller effective polarizability anisotropy or dipole moment for samples fixed at lower salt concentration. We interpret the results in terms of segmental, field-induced orientation of the disorganized structure which is present in low salt concentrations. We also observed a field-induced absorbance decrease in chromatin fibers fixed at salt concentration at and below 100 mM. All three optical effects, namely overall orientation of the high-salt fixed fiber, segmental orientation of the low-salt fixed fiber, and field-induced absorbance decrease, occur on roughly the same time scale, 20-100 μs for 50 nucleosome polynucleosomes. The polarizability anisotropy of fibers fixed in 100 mM salt was found to be proportional to the length of the fragment and to the reciprocal square root of the conductivity of the solution used for electric-dichroism measurements. Addition of Mg2+ to the measurement buffer affected the dichroism amplitude of samples fixed below 100 mM salt but not those fixed at 100 mM salt. The results reinforce the need for caution in interpreting electric-dichroism measurements on chromatin fibers because of possible field-induced distortion effects.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360210109
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  • 159
    Digitale Medien
    Digitale Medien
    Interactions of DNA with divalent metal ions. III. Extent of metal binding: Experiment and theory (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 219-232 
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    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: DNA with Mn2+ as the only counterion has been prepared, and the extent of the Mn2+ binding was determined under a variety of conditions through measurements of the proton relaxation enhancement of water. The total extent of Mn2+ binding per DNA phosphate is found to be 0.43 ± 0.04, independent of the metal ion concentration in the experimental range of 2.8 × 10-5 to 2.1 × 10-3M. The predictions of Manning's condensation theory and those obtained from solution of the generalized Poisson-Boltzmann equation regarding the extent of divalent ion binding to polyelectrolytes, in the presence and absence of monovalent counterions, are compared with one another and with the experimental results. Good agreement between the two theoretical approaches is found, with less than 14% variance in the predicted extent of binding over a large range of mono- and divalent ion concentrations. While the predictions of both theoretical approaches generally agree with the experimental results, some discrepancies are noted and their possible origins discussed.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360210117
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  • 160
    Digitale Medien
    Digitale Medien
    Microdomain dynamics in folding proteins (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 1275-1300 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The basic formulas for the incorporation into the diffusion-collision model of the stabilities of intermediate states on the folding pathway are derived and discussed. A hypothetical two-step folding pathway is calculated in detail. A model for the production of incorrectly folded intermediates is suggested and some numerical estimates made. Implications and future directions in the evolution of the model are discussed. Three appendices deal with some mathematical aspects of the model.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360210703
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  • 161
    Digitale Medien
    Digitale Medien
    Quasielastic light scattering by biopolymers. V. Interparticle interactions between polynucleosomes (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 1365-1382 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Quasielastic light scattering and electrophoretic light scattering experiments were performed on chicken erythrocyte polynucleosome solutions at various temperatures and ionic strengths. The apparent diffusion coefficient, Dapp, was found to depend on the scattering vector K. In general, Dapp can be described as a damped oscillatory function of K in the ionic strength range of 10 to 60 mM and over the temperature range of 10 to 40°C. Electrophoretic light scattering studies on total digest chromatin samples indicate the apparent charge on the polynucleosomes increases as the ionic strength is lowered from 10 to 1 mM. These data are interpreted in terms of fluctuations in the surface charge distribution of the polyion and subsequent inducement of an asymmetric distribution of small ions about the polyion. These fluctuation components lead to the formation of “clusters” of polyions.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360210707
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  • 162
    Digitale Medien
    Digitale Medien
    Microwave absorption by folded DNA chains (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 1399-1410 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Absorption of radiation by DNA polymer is calculated for the case of bent polymer chains. The molecule is assumed to be straight except for localized bends. The region between two bends is studied in particular. The vibrational properties of the bends are parameterized by a transmission and a reflection coefficient. A general Green function expression for absorption is studied for various values of the damping rate, as well as the transmission/reflection coefficients. Curves of absorption vs frequency are shown for a number of cases.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360210709
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  • 163
    Digitale Medien
    Digitale Medien
    Helix-coil transition of poly(α,L-glutamic acid) at an interface: Correlation with static and dynamic membrane properties (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 1451-1463 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: When adsorbed from an aqueous dilute solution at high pH into the pores of an inert cellulose acetate filter, poly(α,L-glutamic acid) remains strongly anchored to the pore walls. The existence of the helix-coil transition for the adsorbed polypeptide in a certain pH range is evidenced by static and dynamic membrane properties displayed by the “activated” filter, such as excess cation uptake, membrane potential, and hyraulic permeability. In particular, the variations of the hydrodynamic thickeness present a sigmoidal shape characteristic of the helix-coil transition at the interface, a transition apparently less sharp than in solution.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360210713
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  • 164
    Digitale Medien
    Digitale Medien
    Chromatin structure studied by linear dichroism at different salt concentrations (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 343-358 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: We have studied the linear dichroism (LD) of rat liver chromatin oriented by flow. Soluble chromatin, prepared by brief nuclease digestion, is found to exhibit a positive LD at low ionic strength (1 mM NaCl), with a constant LD/A over the absorption band centered at 260 nm (A, isotropic absorbance). Several previous dichroism studies on soluble chromatin have been performed on sonicated materials and have given negative LD, probably due to the presence of uncoiled DNA. The positive dichroism can be interpreted in terms of a supercoil of DNA in chromatin with a pitch angle larger than 55°, and is, for example, consistent with a model where the cylindrical nucleosome core particles are stacked face to face in the chromatin filament. In contrast to the nuclease-digested chromatin, sonicated chromatin was confirmed to exhibit negative LD. This difference can be attributed to a partial uncoiling of the linker regions between the nucleosomes due to the shearing. The structural transition of chromatin to a compact form can be observed as a reduction of the positive LD of the nuclease-digested chromatin to almost zero in 0.1 M NaCl or in 0.1 mM MgCl2. This transition is due to a decreased electrostatic repulsion between negative phosphate groups on the DNA chain. In the case of Na+, this can be explained as a screening effect due to the bulk concentration of Na+. With Mg2+ a considerably stronger effect may indicate a more localized binding to the phosphates. At ionic strengths higher than 0.5M NaCl, the dissociation of the histones from DNA leads to uncoiling of chromatin. The change in LD during this process shows that histone H1 contributes only to a small degree to the coiling of the DNA chain, whereas histones H3 and H4 play the major role in the coiling.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360210209
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  • 165
    Digitale Medien
    Digitale Medien
    Physicochemical properties of pectic acid. I. Thermodynamic evidence of a pH-induced conformational transition in aqueous solution (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 431-449 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: On the basis of measurements of enthalpy of dissociation and of dilution, an interamolecular conformational transition induced by pH change is shown for pectic acid in aqueous solution. Additional evidence is given by potentiometic, viscometric, and chiroptical results. The transition from a more rigid, probably H-bonded, structure prevailing at low pH to a more extended one at around neutrality is accompanied by a ΔH value of about 500 cal/equiv and a ΔS value of 1.6 cal/equiv K in water at 25°C. The addition of salts increases the stability of the rigid conformation without changing the general features of the phenomenon. Dilatometric measurements suggest that the transition is accompanied by practically no change in the overall solvation of the polymer chain.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360210214
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  • 166
    Digitale Medien
    Digitale Medien
    Borate complexes of amphotericin B: Polymeric species and aggregates in aqueous solutions (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 459-470 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Amphotericin B, a polyene macrolide antibiotic, exists in aqueous solution as a poorly soluble, high-molecular-weight aggregate. A borate complex of this polyene was prepared that has greater solubility and is less aggregated. In aqueous solution this borate complex exists as a mixture of several molecular species differing in borate content, molecular weight, and molecular conformation. The solubility varied with pH and was minimal at neutrality. Throughout the pH range it was one to two orders of magnitude higher than that of the parent compound. The molecular size distribution, as determined by differential ultrafiltration, showed a progressive increase in the weight fraction of aggregates going from acid to alkaline solutions. The sizes of aggregates ranged from under 25 to over 100 molecules. The borate content of the complexes increased with increasing pH. No borate was complexed in acid solutions. This indicated that amphotericin B and borate ions can complex to form copolymer chains of varying length in which these species alternate, since both are bifunctional. The complexation equilibrium is favored by high pH. Absorption and CD spectra indicated that the polyene molecules can stack reversibly to form dimers. Dimerization constants calculated from the spectra were highest in neutral solution and declined with increasing acidity or alkalinity. In alkaline solutions the polymer chains are long and extended, with minimal stacking. In neutral solution the chains are shorter and extensively stacked. In acid solutions no borate complexes are formed, and the polyenes are stacked to an intermediate degree. The very different effects of pH and concentration on the degree of complexation with borate and on the degree of dimerization of the polyenes shows that these equilibria are independent of each other.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360210216
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  • 167
    Digitale Medien
    Digitale Medien
    Equilibrium swelling of pigment gallstones: Evidence for network polymer structure (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 601-610 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A major component of pigment gallstones (PS) is a black, insoluble substance. It has been suggested that this pigment material might be a highly crosslinked polymer, and if such were the case, it should imbibe solvent (swell) to the maximum permitted by the crosslinks of its macromolecular network. We measured the equilibrium amount, qeq, by which pulverized, desiccated PS swells in different liquids, including isotonic aqueous buffers at pH values from 1.5-11.5. For ionic strengths ≥ 0.15, the dependence of qeq on pH exhibits a broad titration curve with a midpoint near pH 7. qeq was 〈 1.2 in methanol, dimethylformamide, dimethylsulfoxide, and chloroform. The ir absorbance from vinyl groups in the black pigment was only one-eighth that of unconjugated bilirubin, the primary chemical building block of PS; this implicates vinyl groups in the formation of a polymer network. The rise in qeq with increasing pH suggests that the carboxyl groups are free to ionize and are therefore not involved in the covalent bonds that make the crosslinked polymer. A network polymer structure would account for the inability to dissolve PS in those solvents in which unconjugated bilirubin is soluble.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360210309
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  • 168
    Digitale Medien
    Digitale Medien
    25Mg-nmr investigations of the magnesium ion-DNA interaction (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 653-664 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: 25Mg-nmr data are reported that address the nature of the magnesium ion-DNA interaction. It is found that competitor ions such as calcium, mercury, zinc, and cobalt ions are not effective in competing for all of the magnesium ion-DNA interaction that is reported by the 25Mg-nmr spectrum. The temperature dependence of the 25Mg-nmr spectrum in DNA solution studied at high concentrations of competitor ion indicates that the chemical-exchange lifetime of the magnesium ions at DNA binding sites makes a major contribution to the 25Mg-nmr line width. However, the activation parameters are not consistent with the temperature dependence of either transport properties or chemical exchange with phosphate groups alone, but are consistent with a sum of at least two processes that provide opposing contributions to the 25Mg-nmr relaxation. It is also shown that the non-Lorentzian character of the 25Mg-nmr line previously reported is consistent with the effect of an incompletely averaged static nuclear electric quadrupole interaction and/or an exchange process that is slow with respect to the magnitude of this interaction. Because the concentrations employed in these experiments are high, the present data do not provide a direct or critical test of the electrostatic theories of ion-polyelectrolyte interaction. The present data do demonstrate, however, that such theories alone are insufficient as a basis for understanding the 25Mg-nmr data.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360210312
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  • 169
    Digitale Medien
    Digitale Medien
    Effects of side-chain conformation on π-π* circular dichroic spectra of poly(L-α-aminobutyric acid) general helices (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 703-704 
    Details
    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
    URL: http://dx.doi.org/10.1002/bip.360210316
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  • 170
    Digitale Medien
    Digitale Medien
    Semiflexibility of collagens in solution (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 715-728 
    Details
    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 of lugworm cuticle collagen in 0.1M acetic acid was evaluated as 1600 ∼ 1800 Å by Yamakawa-Fujii's model for a wormlike chain from the sedimentation constant and the intrinsic viscosity. The persistence length was further examined for a series of sample “collagen sonicates” produced by varying the duration of sonic irradiation. To estimate the salt effect on the persistence length, measurements were made over a range of NaCl concentrations from 0 to 0.1M. The results showed that the cuticle collagen and collagen sonicates had identical values of persistence length and that the neutral salt effect for the cuticle collagen was far smaller than that for DNA.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360210402
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  • 171
    Digitale Medien
    Digitale Medien
    Hydrodynamics, size, and shape of bacteriophage T4D tails and baseplates (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 797-804 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: We have used translational diffusion coefficient measurements and subunit hydrodynamic theory to determine the dimensions and shape of bacterioophage T4D baseplates and tails. The diffusion coefficient of the baseplate, measured by quasielastic laser light scattering (QLS), was determined previously by Wagenknecht and Bloomfield to be D = 8.56 × 10-8 cm2/s. For the tail, we found D = 5.88 × 10-8 cm2/s by QLS, and D = 6.02 × 10-8 cm2/s by combining sedimentation coefficient and molecular weight in the Svedberg equation. These values, which have an uncertainty of ±2.7%, when combined with subunit hydrodynamic theory, enabled us to refine estimates of dimensions obtained by electron microscopy. For the hexagonal baseplate, the vertex-to-vertex distance is about 480 Å, the thickness is 160 Å, and there are six extended short fibers 320-Å long and 40 Å in diameter. When a baseplate of these dimensions is attached to a tail tube-sheath-connector complex 1050-Å long and 240 Å in diameter, the calculated D is 5.93 × 10-8 cm2/s, within 1% of experiment. This combined use of electron microscopy and hydrodynamics, using the former to ascertain shape, and the latter to obtain solution dimensions, is a powerful approach to the structure of biomolecular complexes.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360210406
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  • 172
    Digitale Medien
    Digitale Medien
    Spin-label studies of the pH-induced random coil to α-helix conformational transition in poly(L-lysine) (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 833-847 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Poly(L-lysine) of various molecular weights between 2700 and 475,000 was spin-labeled. From the electron spin resonance spectra, the degree of freedom of the nitroxide was determined by calculation of the rotational correlation time as the poly(L-lysine) underwent the pH-induced random coil to α-helix conformational transition. In general, the rotational correlation time of the nitroxide increased as the pH was increased, indicating a more restricted environment for the spin label when poly(L-lysine) is deprotonated. For the high-molecular-weight poly(L-lysine) this corresponds to the formation of the α-helix and indicates that the side chain-side chain interaction and decreased segmental motion of the backbone (slightly) restricts the motion of the spin label. For the 2700-molecular-weight poly(L-lysine), previously shown not to assume a helical conformation at high pH, the increase in the rotational correlation time of the spin label indicates that the side chain-side chain interaction takes place after deprotonation but without helix formation. This may indicate that helix formation per se is not needed to produce the observed effect even with the high-molecular-weight polymers. The rotational correlation time of the spin label at a particular pH did not depend on the molecular weight of the poly(L-lysine) over the 200-fold range of molecular weights. This indicates that the rotational correlation time reflects the rotational mobility of the spin label in a localized environment and not the rotational diffusion of the entire macromolecule.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360210409
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  • 173
    Digitale Medien
    Digitale Medien
    Fluoroquinacrine binding to nucleic acids: Investigation of the 19F-nmr, optical, and fluorescence properties in the presence of DNA, poly(A), and tRNA (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 909-921 
    Details
    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 fluoroquinacrine, 3-fluoro-7-chloro-9-(diethylamino-1-methylbutyl-amino)acridine, with poly(A), DNA, and tRNA has been investigated by monitoring changes in the 19F-nmr properties, the fluorescence, and the optical absorbance of the drug. The changes in the properties of fluoroquinacrine in the presence of nucleic acids are similar to those observed for quinacrine and suggest that the drugs bind in a similar fashion. The molecular dynamics of fluoroquinacrine bound to nucleic acids were determined by interpreting the data from a number of different nmr relaxation experiments with a two-correlation-time model. The two motions are the long-range bending motion of the drug-nucleic acid complex and the sliding of the drug between the base pairs. Both dipolar and chemical shift anisotropy contributions to the nmr relaxation parameters were taken into consideration. The binding of fluoroquinacrine to tRNA appears to be different from that observed for binding to DNA. Optical absorbance and 19F-nmr were also used to examine the helix-to-coil transitions of the drug-nucleic acid complexes. In the DNA complex, the 19F chemical shift changes parallel the absorption changes that occur during the transition. 19F-nmr and absorption show that the drug-tRNA complexes undergo a cooperative helix-to-coil transition, with the drug binding sites melting when the tRNA is 70% denatured.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360210505
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  • 174
    Digitale Medien
    Digitale Medien
    Masthead (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982) 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360211001
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  • 175
    Digitale Medien
    Digitale Medien
    Crystal structure and solution conformation of 1-N-acetyl-β-D-glucopyranosyl amine: A model for the glycopeptide linkage (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 1971-1977 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The crystal structure of the title compound, a model for the glycosyl linkage between the asparagine side chain and N-acetyl glucosamine in glycoproteins, has been determined and compared to other model structures. The pyranose ring in the crystal is in the 4C1 chair conformation and the amide functions at C1 and at C2 are both oriented such that the amide protons are nearly trans to their respective sugar-ring protons. Coupling constants determined from the fully assigned proton nmr spectrum in aqueous solution are consistent with the conformation in the crystal.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360211004
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  • 176
    Digitale Medien
    Digitale Medien
    Flow dichroism of capsid DNA phages. I. Fast and slow T4B (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 1991-2010 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Flow linear dichroic studies have been conducted on phage T4B in its fast and slow forms. The behavior of the phages is well represented by an equivalent ellipsoid model using the Peterlin-Stuart theory. The measurements permit the evaluation of the optical factor of the DNA in the phage and the rotary diffusion coefficient of the phage particle. Both these quantities change during the slow-fast conversion. The rotary diffusion results are in good agreement with those obtained by other workers with other methods. The optical factor is negative, indicating a net alignment of DNA helices parallel to the phage axis. The results exclude certain simplified models for the packaged DNA but do not lead to a unique structural conclusion. The flow dichroism experiment and its interpretation are described, and a simple method of calculating optical factors for complicated but cylindrically symmetric structures is presented.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360211006
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  • 177
    Digitale Medien
    Digitale Medien
    Polynucleotide folding in yeast tRNAPhe: Elucidation of short-, medium-, and long-range interactions of sugar-phosphate-sugar backbone and base using a “blocked” nucleotide probeContribution No. 590 from the Department of Crystallography and Biophysics, University of Madras, Guindy Campus, Madras-600025, India. (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 2033-2047 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: It has recently been proposed that the repeating backbone nucleotide may be regarded as consisting of two blocks of equal magnitude representable by two virtual bonds. Implicit consideration of the nucleotide (ψ,ψ) and internucleotide (ω′,ω) geometry that generate variety in polynucleotide conformations, and of the constancy of the repeating structural moieties (P-C4′ and C4′-P) independent of the above rotations, has enabled us to utilize this scheme in the study of ordered structures such as di-, oligonucleotides and, most significantly, tRNA. The polynucleotide folding dictated by short-, intermediate-, and long-range interactions in the monoclinic and orthorhombic forms is described and compared through circular plots depicting the virtual bond torsions and distance plots constructed independently for backbone as well as bases. The torsions and the bond angles associated with the virtual bonds afford a clear distinction between ordered helical segments from loops and bends of tRNA. Lower virtual bond torsions (-60° to 60°) concomitant with higher values of virtual bond angles characterize various bend regions, while torsions around 160°-210° typify ordered helical strands. The distance plot elucidates the type of interaction associated with various sub-structures (helix-helix, helix-loop, and loop-loop) that form the constituents of different structural domains. Several other features such as the manifestation of the P10 loop and the approximate twofold symmetry in the tRNA molecule are conspicuous on the distance plot.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360211008
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  • 178
    Digitale Medien
    Digitale Medien
    Fluctuational base-pair opening in DNA at temperatures below the helix-coil transition region (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 2069-2081 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The probability of DNA base-pair opening was calculated at temperatures below the denaturation region. The helix-coil transition theory, modified to include different nearest-neighbor interactions, was employed. Predictions of base-pair opening employing DNA melting-curve parameters differed considerably from predictions based on parameters evaluated from synthetic RNA oligomer data of Gralla and Crothers (G-C) and formaldehyde-DNA binding experiments of McGhee and von Hippel (M-vH). Calculations based on the latter parameters indicate a base-pair-opening probability of 10-2-10-3 at 35°C in 0.1M NaCl. DNA melting-curve parameters predict values about 103 smaller. At a temperature 10°C below the transition midpoint of a specific DNA sequence, DNA melting parameters predict base-pair opening of about 10-3, whereas the G-C and M-vH parameters predict that ≳0.16 of the DNA is melted. Experiments and theoretical assumptions relevant to the calculations are analyzed. Evidence suggests that DNA melting parameters are valid when the average loop size exceeds some minimum value, whereas the G-C and M-vH parameters appear more valid for single base-pair loops. A reconciliation of the two sets of predictions can be made if interactions extending beyond neighboring base pairs are considered. Such interactions will make the parameters of the nearest-neighbor model appear to change with the average loop size. Experiments that may provide further measurements of base-pair opening are discussed.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360211011
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  • 179
    Digitale Medien
    Digitale Medien
    New polymer syntheses. IV.Part III: Kricheldorf, H. R. & Fehrle, M. (1980) Makromol. Chem. 181, 2571-2585. Polypeptides of lysine and ornithine with pending pyrimidine bases (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 2097-2122 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Starting with β-methoxy methacryloylisocyanate, β-methoxy methacrylisothiocyanate, and β-isocyanatopropionyl chloride, on the one hand, and Nα-Z-lysine or Nα-Z-ornithine, on the other hand, Nα-Z-amino acids with pyrimidine bases in the side chain were synthesized. These Z-protected nucleoamino acids were converted to the corresponding N-carboxyanhydrides (NCAs) via the silylester method. In the case of 2-thiothymine derivatives, the reaction intermediate of the NCA synthesis caused benzylation of the thioxo- group, so that a new class of 2-mercaptopyrimidine derivatives was isolated unexpectedly. The poly(nucleoamino acids) obtained by polymerization of the nucleoamino acid NCAs were characterized by elemental analyses, optical rotations 1H-nmr and 13C-nmr spectra. Vapor pressure osmometry revealed that the DPs were in the range of 20-30. Their spectra suggest a helical secondary structure. While all homopolypeptides are insoluble in water, copolypeptides containing L-lysine Nε-hydrobromide possess good solubility in water.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360211103
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  • 180
    Digitale Medien
    Digitale Medien
    Vibrational circular dichroism in amino acids and peptides. 7. Amide stretching vibrations in polypeptides (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 2161-2183 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Vibrational circular dichroism (VCD) spectra for the principal amide stretching vibrations, amide A (N—H stretch) and amide I (predominantly C=O stretch), are presented and analyzed for a variety of polypeptides dissolved in chloroform, as well as for two examples in D2O. Our results for poly(γ-benzyl-L-glutamate) confirm the first and only previous report of VCD in polypeptides carried out by Singh and Keiderling [(1981) Biopolymers 20, 237-240]. Collectively, our spectra show that the sense of the bisignate VCD in these two regions depends on the sense of α-helicity and not on the absolute configuration of the constituent amino acids. This conclusion is established by obtaining VCD for the two polypeptides, poly(β-benzyl-L-asparate) and poly(im-benzyl-L-histidine), that form left-handed as opposed to right-handed α-helices. A new amide band having significant VCD intensity owing to its Fermi resonance interaction with the N—H stretching mode has been identified as a weak shoulder on the low-frequency side of the amide A band near 3200 cm-1 and is assigned as a combination band of the amide I and amide II vibrations. VCD spectra of polypeptides in D2O solution, although weak, have been successfully measured in the amide I region, where spectra appear to be more complicated due to the presence of solvated and internally hydrogen-bonded amide groups. Strong monosignate contributions to the VCD in the amide A and amide I regions for some of the polypeptides indicate coupling of an electronic nature between these two regions and is deduced by an application of the concept of local sum rules of rotational strength. It appears that a detailed understanding of the VCD obtained for polypeptides will not only be diagnostic of secondary structure, but also of more subtle structural and vibrational effects that give rise to local, intrinsic chirality in the amide vibrations.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360211106
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  • 181
    Digitale Medien
    Digitale Medien
    DNA bis-intercalation: Theoretical analysis, including cooperativity of the interaction of echinomycin analogs with DNA (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 2279-2290 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A theoretical analysis of the binding curves for the bifunctional peptide antibiotic echinomycin and its analogs interacting with a variety of DNAs is presented. The method is an extension of our previous work using the sequence-generating-function technique and has been modified to allow for consideration of cooperativity within the framework of the neighbor-exclusion rule. Binding by both single and double intercalation is included, and the results are, in many cases, superior to the analysis based on single-mode binding. In all cases the data are consistent with the neighbor-exclusion principle for intercalation when analyzed with this approach, while data analysis, using a simpler method, often led to violation of this rule. Positive cooperativity is considered in the treatment of data for binding to poly(dA-dT). Finally, we discuss the relationship between base specificity and binding site size.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360211114
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  • 182
    Digitale Medien
    Digitale Medien
    Quasielastic light scattering by biopolymers. VI. Diffusion of mononucleosomes and oligonucleosomes in the presence of static and sinusoidal electric fields (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 1383-1398 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Quasielastic light scattering and electrophoretic light scattering studies were carried out on mononucleosome and oligonucleosome systems. The electrophoretic light scattering experiments employed static and sinusoidal electric fields. Data are presented that suggest at least two relaxation modes. It is proposed that the small amplitude sinusoidal field effectively polarizes the ion atmosphere about the polyion, thus leading to an induced dipole moment that varies sinusoidally in time. This model is, in essence, an extension of the current interpretation of low-frequency dielectric dispersion data on DNA as being due to fluctuations of counterions along the polyion.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360210708
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  • 183
    Digitale Medien
    Digitale Medien
    Absorption of microwave radiation by DNA double helix in aquo (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 1465-1468 
    Details
    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
    URL: http://dx.doi.org/10.1002/bip.360210714
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  • 184
    Digitale Medien
    Digitale Medien
    DNA bis-intercalation: Theoretical calculation of binding curves (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 419-430 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A statistical mechanical calculation of the binding properties of DNA bis-intercalators is presented, based on the sequence-generating function method of Lifson. The effects of binding by intercalation of one or both chromophores of a bifunctional intercalating agent are examined. The secular equation for a general model that includes the effects of neighbor (nearest and non-nearest) exclusion and/or cooperativity in the binding of both singly and doubly intercalated ligands is derived. Numerical results for binding curves are presented for a more restricted model in which each type of bound ligand rigorously excludes its nearest neighbor and the total number of sites covered by a doubly intercalated ligand is variable. At low values of free ligand concentration bis-intercalation dominates the binding process, while at high value of free ligand concentration, intercalation of only one chromophore per ligand becomes significant due to the unavailability of contiguous free sites required for bis-intercalation. Also, depending on the binding parameters, the free energy of the system can be lowered by a loss of doubly intercalated ligands in favor of singly intercalated ones. Corresponding to this transition in binding mode, the average number of sites occupied by a bound ligand decreases from that characteristic of bis-intercalation to that characteristic of mono-intercalation as free ligand concentration increases. An analysis of Scatchard plots describing bis-intercalation is presented.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.1980.360190215
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  • 185
    Digitale Medien
    Digitale Medien
    DNA bis-intercalation: Application of theory to the binding of echinomycin to DNA (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 431-443 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The statistical mechanical model for the binding of bifunctional intercalating ligands to duplex DNA described in the preceding paper is applied to the example of echinomycin-DNA interactions. This is the only system for which binding curves have been obtained under conditions leading to binding by both bis-intercalation and mono-intercalation simultaneously. Binding parameters and Scatchard plots are calculated for a variety of conditions. A detailed comparison of these calculations with the results from the previous analysis of the same binding data in terms of the McGhee-Von Hippel theory, assuming only one mode of binding, is presented. The results of our calculations are consistent with the model of bis-intercalation requiring the two bound chromophores of a bifunctional ligand to be separated by two base pairs. It is not necessary to assume violation of the nearest-neighbor exclusion principle, as occurred in the original analysis.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.1980.360190216
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  • 186
    Digitale Medien
    Digitale Medien
    Long-range spin-spin coupling as an aid for the assignment of aromatic residues in peptide 1H-nmr spectra (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 2483-2486 
    Details
    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
    URL: http://dx.doi.org/10.1002/bip.360211213
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  • 187
    Digitale Medien
    Digitale Medien
    Kinetics of formation of fibrin oligomers. II. Size distributions of ligated oligomers (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 2265-2277 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Human fibrinogen was treated with thrombin in the presence of fibrinoligase (Factor XIIIa) and calcium ion at pH 8.5, ionic strength 0.45, and the ensuing polymerization was interrupted at various time intervals (t) both before and after the clotting time (tc) by solubilization with a solution of sodium dodecylsulfate and urea. Aliquots of the solubilized protein were subjected to gel electrophoresis on polyacrylamide gels after disulfide reduction by dithiothreitol and on agarose gels without reduction. The degree of γ-γ ligation was determined from the former and the size distribution of ligated oligomers, for degree of polymerization x from 1 to 10, from the latter. In some experiments, thrombin was inhibited, after partial polymerization, by p-nitrophenyl-p′-guanidinobenzoate. From these, it was concluded that for thrombin concentration ≤0.013 units/mL and fibrinoligase ≥30 mg/L, oligomer assembly is rapid compared with peptide A release and ligation is rapid compared with assembly. Under these conditions, the theory of the first paper of this series describes rather well the time dependences of the degree of γ-γ ligation, the weight fractions of monomer and small oligomers, and the number- and weight-average degrees of polymerization after solubilization of the staggered overlapped assemblies, each of which splits to give two strands of end-to-end ligated oligomers. The theory assumes that the second A peptide is released by thrombin more rapidly than the first by a factor q, which, from the experimental data, is determined to be 16. The subsequent assembly into staggered overlapped oligomers follows the statistics of linear polycondesation taking into account the presence of both difunctional and monofunctional combining units. For higher thrombin or lower fibrinoligase concentrations, ligation fails to keep pace with oligomer assembly, and the size distributions after solubilization show a higher proportion of very small and a lower proportion of larger ligated oligomers, owing to separation of the staggered overlapped assemblies into smaller fragments.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360211113
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  • 188
    Digitale Medien
    Digitale Medien
    Loop formation in polynucleotide chains. I. Theory of hairpin loop closure (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 2329-2344 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A theoretical model to determine the probability of loop formation, based on an elaborated form of the Jacobson-Stockmayer theory of cyclization equilibria, has been developed and used on RNA chains of homogeneous puckering and lengths up to 27 residues. The probability Qx (q, γ0, ε0) of occurrence of hairpin loops of a particular chain x is given by Qx (q, γ0, ε0) = [W (q) δr][2Γq (γ0)δγ] [Eq,γ0 (ε0) δε] where W(q) is the three-dimensional density distribution function of end-to-end vectors r centered about the ideal loop closure position q; Γq(γ0) is an angular correlation factor that restricts the orientation of terminal bonds (i.e., bond x and bond 1) in the loop to a specified value Δθ = cos-1 (γ0) when r adopts a value within a range δr from position q; and Eq,γ0(ε0) is the probability that ε falls within δε of ε0 when r and γ assume the values denoted by the respective subscripts. The parameter ε is related to the angle between a hypothetical bond (x + 1) and bond 1. In these calculations, Eqγ0(ε0) was set equal to 1. For randomly coiling models previously developed to reproduce polynucleotide unperturbed dimensions, loop closure probability is maximized with chains of length 22 residues. Larger hairpin loops of 24-25 residues, also favored in C3′-endo random coils of this type, are potential models of tRNA unfolding. W(q) is a stronger determinant of loop closure than Γq(γ0). The angular correlation effect is most noticeable at chain lengths 22 and 23 where 2Γq(γ0) deviates from unity.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360211203
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  • 189
    Digitale Medien
    Digitale Medien
    Analysis of high-resolution melting (thermal dispersion) of DNA. Methods (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 681-700 
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    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 capabilities of a method for obtaining high-resolution melting profiles of short, homogeneous DNAs using a thermo-differential absorbance technique. The absorbance difference of two identical DNA solutions, raised linearly in temperature and maintained at a constant temperature difference, is monitored using a double-beam spectrophotometer. A specially constructed temperature controller and cell holder enable the temperature of the DNA samples to be controlled and monitored directly. A heating rate of 6.75°C/hr has been found to give reproducible results at ionic strengths 〉 0.01M. A method of reconstructing the true derivative from experimental data using a Taylor series expansion is described and shown to work well when the difference in temperature between samples is in the range of 0.2°C. Reconstructed derivative profiles are further analyzed by deconvolution into distinct Gaussian components. The melting profile of PM-2 DNA is shown to consist of 14 components, while the much longer lambda DNA yields 55. Related techniques such as data management and analysis for the fractional G·C content of specific domains are also described.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.1980.360190316
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  • 190
    Digitale Medien
    Digitale Medien
    Intramolecular low-frequency vibrations in lysozyme by neutron time-of-flight spectroscopy (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 43-50 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: High-resolution neutron time-of-flight (TOF) spectra were measured for partly deuterated hen egg-white lysozyme in solution with and without N-acetyl-glucosamine inhibitor bound to the cleft, and in polycrystalline form. Weak but reproducible bands occur at frequencies between 25 and 375 cm-1. The bands were tentatively assigned on the basis of previous results for homopolypeptides. At very small energy transfers (between about 1 cm-1 and 40 cm-1), the TOF spectra show a dependence both on inhibitor binding and crystalline environment. This is interpreted in terms of conformational flexibility.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360210105
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  • 191
    Digitale Medien
    Digitale Medien
    Electric dichroism studies on ferriheme- and ferroheme-poly(L-lysine) complexes at pH 9-12 (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 89-100 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Transient electric dichroism has been measured for the ferriheme-poly(L-lysine)[(Lys)n], ferroheme-(Lys)n, and ferroheme-(Lys)n-carbon monoxide (CO) solutions at pH 9-12. The Soret absorption maximum in electronic spectrum (λ), the reduced linear dichroism (ρ∞) at complete orientation and the calculated angle (φ) between the porphyrin plane of a bound heme and the oriented polymer axis are determined for the following complexes: a ferriheme-(Lys)n complex at pH 9.5-10.5 (λ = 420 nm, ρ∞ = 0.50, and φ = 19°), a ferroheme-(Lys)n complex at pH 9.5-10.2 (λ = 432 nm, ρ∞ = 0.77, and φ = 0°), and a ferroheme-(Lys)n-CO complex at pH 9.25 (λ = 430 nm, ρ∞ = 0.38, and φ = 24°). Based on the above data, the validity of the structures of heme-(Lys)n complexes proposed by other investigators is discussed.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360210108
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  • 192
    Digitale Medien
    Digitale Medien
    Effects of salts on the nonequivalent stability of the α-helices of isomeric block copolypeptides (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 131-145 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The stability of the α-helices of isomeric block copolypeptides is nonequivalent, as reported previously. In order to explore the origin of the nonequivalence, the stability of α-helix of two block copolypeptides, (L-Ala)20-(L-Glu)20-(L-Phe) (designated as AEF) and (L-Glu)20-(L-Ala)20-(L-Phe) (EAF), in aqueous solution was investigated as a function of pH, temperature, and salt concentration by the measurement of the α-helical content using CD at 223 nm. The transition temperature, Tm, as a measure of the stability of the α-helix, decreased with increasing the salt concentration for EAF, while Tm increased for AEF. The results indicate that electrostatic interactions affect the nonequivalence of such helical stability. Thermodynamic quantities, ΔG, ΔH, and ΔS, of the thermal transition from random coil to α-helix were obtained by applying the curve-fitting method to the data. The major contribution to the effects of salts seems to be the entropic term, not the enthalpy term. This is unexpected, since the salt ions would weaken electrostatic interactions between ionized groups and the dipole along the helical axis, which affect the enthalpy term. In addition, the dependence of the electrostatic effect on the salt concentration is different for EAF and AEF. There fore, the nonequivalence cannot be accounted for by only the electrostatic effect, suggesting that it originates from some intrinsic property of the α-helix.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360210111
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  • 193
    Digitale Medien
    Digitale Medien
    Anomalous temperature dependence of frictional coefficients: Diffusion and sedimentation measurement of low-density lipoproteins, albumin, and polystyrene latex (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 233-248 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Using quasielastic light scattering, we have determined the diffusion coefficients of low-density lipoprotein (LDL) and polystyrene latex spheres over the temperature range of 293-318 K. The results show that after correction for thermal changes in the solvent, there remains a residual negative temperature coefficient in the diffusion amounting to about -0.6%/K that is independent of the chemical type of complex. Confirmation of these results was obtained for LDL through sedimentation studies over a similar range of temperatures. The residual temperature coefficient was similar to that reported for oxyhemoglobin [W. B. Veldkamp and R. Votano (1980) Biopolymers 19, 111-124] and greater than that found for bovine serum albumin by these and earlier workers. These observations show that the residual dependence on temperature is not an isolated phenomenon and could in part be explained by increased aggregation of particles, although this is not the primary cause of the effect.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360210118
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  • 194
    Digitale Medien
    Digitale Medien
    Poly(dA-dT) complexes with histone H1 and pancreatic ribonuclease: Specific base recognition evidenced by ultraviolet resonance Raman spectroscopy (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 277-286 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The conformational changes of poly(dA-dT) from random coil to ordered structure with stacked bases produce important changes in the Raman line intensities (hypochromism) when the polymer is excited under the preresonance Raman conditions (λ excitation = 300 nm). Poly(dA-dT)-RNase and poly(dA-dT)-histone H1 interactions have been studied as models of mechanisms of destabilization and stabilization by proteins of the DNA secondary structure, respectively, following this intense preresonance Raman hypochromism. In addition, the specific variation of the intensity of the 1582-cm-1 line of adenine is interpreted in terms of the interaction of the amino group with the RNase (thus involving the large groove). In the poly(dA-dT)-H1 complex, the intensity of the 1665-cm-1 line of thymine increases. This increase appears to involve the C2=O group of thymine, located in the narrow groove.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360210204
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  • 195
    Digitale Medien
    Digitale Medien
    Comparative microcalorimetric and dilatometric analysis of the interactions of quinacrine, chloroquine, and ethidium bromide with DNA (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 331-341 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The enthalpies of binding of chloroquine and quinacrine to DNA at different molar ratios of drug to DNA and at different ionic strengths have been measured. The limiting values obtained with quinacrine fall in the range found for typical intercalating agents (e.g., ethidium, proflavin, adriamycin), whereas the value obtained with chloroquine is always zero, independent of the ratio of drug to DNA and ionic strength. The dilatometric measurements performed on the same systems and on the ethidium-DNA system show that when ethidium and quinacrine bind to DNA at low drug/DNA ratios, a volume decrease of about 16 mL/mol of bound drug occurs. No change in volume is observed when the two drugs bind to DNA through external, electrostatic forces. The volume change can be attributed to the loss of structured water around hydrophobic moieties of the drug molecules, following intercalation. In contrast, chloroquine binding to DNA at low drug/DNA ratios is characterized by a volume change distinctly smaller than that shown by quinacrine. The low ΔVB and ΔHB values shown by chloroquine are discussed in terms of the mechanism of interaction with DNA.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360210208
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  • 196
    Digitale Medien
    Digitale Medien
    1H-nmr comparative studies of polynucleotides: Conformation and dynamic structure of polyribo(uridylic) and polyribo(cytidylic) acids in neutral solution (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 383-402 
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    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 the dynamic structure of single-stranded poly(U) and poly(C) in neutral aqueous solution have been investigated by 1H-nmr at two different frequencies (90 and 250 MHz) and at various temperatures. Measurements of proton chemical shifts, coupling constants JH-H, and proton relaxation times, T1, T2, versus temperature show a striking difference in conformation and in dynamic structure between the two polynucleotides studied. The temperature effect on δ and JH-H is found to be substantial for poly(C) and insignificant for poly(U). The S conformer is favored in poly(U), whereas the N conformer strongly predominates in poly(C) (≃90%), similar to the case for RNAs. These results suggest that single-stranded poly(C) probably possesses a helical or partial helical structure, whereas poly(U) shows a clear preference for the random coil, in agreement with the optical results. The local motions of the ribose and base were studied at various temperatures by measurements on the relaxation times at 90 and 250 MHz. For a given temperature between 22 and 72°C, the ratio T1(90)/T1(250) is practically the same for all poly(U) protons, indicating that in this temperature interval the ribose base unit of poly(U) undergoes an isotropic motion characterized by a single correlation time τc. Above 52°C, poly(C) exhibits a dynamic structure similar to poly(U). Below this temperature, poly(C) exists in an equilibrium between randomly coiled and single-stranded helix forms. This situation is characterized by a strong cross-relaxation effect and T1 values corresponding to a relatively short apparent correlation time. An activation energy of 4 kcal/mol was determined for the motion of the ribose-base unit in both single-stranded polynucleotides.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360210211
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  • 197
    Digitale Medien
    Digitale Medien
    N-substitutes poly-α-amino acids. III. Synthesis and conformational properties of poly(N-methyl-L-glutamic acid) (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 471-474 
    Details
    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
    URL: http://dx.doi.org/10.1002/bip.360210217
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  • 198
    Digitale Medien
    Digitale Medien
    Masthead (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982) 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360210301
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  • 199
    Digitale Medien
    Digitale Medien
    Influence of hemin on the conformation of cyanogen bromide-cleaved peptides of apomyoglobin (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 805-815 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The complexes of the three BrCN-cleaved fragments of sperm whale apomyoglobin with hemin were studied by circular dichroism (CD). In native myoglobin, the heme is located in the middle fragment; the isolated peptide (residues 56-131), however, produces little extrinsic Cotton effects by the addition of hemin, although about four molecules of hemin are bound to this peptide. In marked contrast, the COOH-terminal peptide (residues 132-153), which binds three hemin molecules, shows strong Cotton effects in the Soret bands and drastically changes its conformation from unordered to highly helical. The Arg-modified or Lys-deaminated peptide no longer undergoes conformational changes by the addition of hemin, suggesting that the two propionic acid groups of one hemin molecule interact with the Arg residue and one of the Lys residues, which stabilizes the induced helical conformation. The NH2-terminal peptide (residues 1-55) binds one hemin molecules, and the helicity of this fragment is slightly enhanced by the addition of hemin. Both the CD and difference absorption spectra indicate that the mode of interaction between the peptides and hemin are different for the three apomyoglobin fragments.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360210407
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  • 200
    Digitale Medien
    Digitale Medien
    Circular dichroism study of modified nucleosides (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 849-858 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: CD study of four modified nucleosides, constituents of tRNA molecules, revealed that 2-thio-5-methyluridine and 5-methyluridine in aqueous solution, 0.1N HCl, and organic solvents essentially occur in an anti-conformation. 5-Methylcytidine also occurs in an anti-conformation similar to cytidine in aqueous solution and organic solvents, while 2-thiocytidine dihydrate appears to occur in an anti-conformation. It is stressed that the CD data of thionucleosides might be applied to the successfully conformational analysis of tRNA molecules.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360210410
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