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  • Chemistry  (6,410)
  • 2015-2019
  • 1980-1984  (6,410)
  • 1945-1949
  • 1980  (6,410)
  • 1
    Electronic Resource
    Electronic Resource
    Interstellar molecules (1980)
    Springer
    Journal of molecular evolution 15 (1980), S. 79-101 
    Details
    ISSN: 1432-1432
    Keywords: Molecules ; Interstellar ; Chemistry ; Isotopes ; Solar system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The study of interstellar molecules broadly includes two areas of interest. One area uses the unique ability of molecules to act as probes of the physical conditions in the cold, dense, visually opaque component of the interstellar medium. The physical properties of this and other components of the interstellar medium are summarized. The other area deals with the chemistry of interstellar molecules, recent aspects of which are emphasized in this review. Gas-phase chemistry, shock chemistry, and grain surface chemistry are discussed in the context of recent observations. No present observations suggest that surface reactions are relevant, but neither can they be ruled out. Ion-molecule reactions are clearly operative, at least for the simpler species. Chemical isotope fractionation is reviewed, andd it is concluded that the complexities of the chemistry allow no cosmological conclusions to be drawn from observations of deuterium in interstellar molecules, while the presence of13C in interstellar molecules permits an estimate of the12C/13C ratio which is consistent with the current concepts of the nucleosynthesis history of the Galaxy. Possible connections between interstellar molecules and the early molecular history of the solar system are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01732663
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  • 2
    Electronic Resource
    Electronic Resource
    The importance of energetic particle precipitation on the chemical composition of the middle atmosphere (1980)
    Springer
    Pure and applied geophysics 118 (1980), S. 128-151 
    Details
    ISSN: 1420-9136
    Keywords: Galactic cosmic rays ; Solar proton events ; Particle precipitation ; Chemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract An assessment is made of the relative contribution of certain classes of energetic particle precipitation to the chemical composition of the middle atmosphere with emphasis placed on the production of odd nitrogen and odd hydrogen species and their subsequent role in the catalytic removal of ozone. Galactic cosmic radiation is an important source of odd nitrogen in the lower stratosphere but since the peak energy deposition occurs below the region where catalytic removal of O3 is most effective, it is questionable whether this mechanism is important in the overall terrestrial ozone budget. The precipitation of energetic solar protons can periodically produce dramatic enhancement in upper stratospheric NO. The long residence time of NO in this region of the atmosphere, where catalytic interaction with O3 is also most effective, mandates that this mechanism be included in future modelling of the global distribution of O3. Throughout the mesosphere the precipitation of energetic electrons from the outer radiation belt (60°≲Λ≲70°) can sporadically act as a major local source of odd hydrogen and odd nitrogen leading to observable O3 depletion. Future satellite studies should be directed at simultaneously measuring the precipitation flux and the concomitant atmosphere modification, and these results should be employed to develop more sophisticated models of this important coupling.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01586448
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  • 3
    Electronic Resource
    Electronic Resource
    Reversion of the B to A transition of DNA induced by specific interaction with the oligopeptide distamycin A (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 823-831 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of the DNA-binding oligopeptide distamycin A on the B to A transition of DNA in ethanol/water solutions has been studied by means of CD. (The overbars indicate that it does not matter which particular form of the corresponding families is considered.) The results show that increasing the concentration of distamycin A reverses the A conformation (in 82% ethanol) to the B conformation due to its strong binding and stabilization of the latter. In accordance with previous data for pure aqueous solutions, a site size of 3.5 base pairs is obtained from the studies in water/ethanolic solutions. From the data on the B to A transition in the presence of distamycin A, we estimated the length of the cooperativity ν0 = 10 base pairs.The results demonstrate that the oligopeptide systems of distamycin, as well as those of netropsin, are effective stabilizers of the DNA B-conformation.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1980.360190408
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  • 4
    Electronic Resource
    Electronic Resource
    NMR evidence for a type I β-turn in (Pro2)-tetrapeptides and interdependence of cis:Trans isomerism, ring flexibility, and backbone conformation (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 781-804 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tetrapeptides with proline in position 2, asparagine or leucine in position 3, and glycine in positions 1 and 4, with end groups free or blocked on the N-terminal side, were studied in their various ionic states in 2H2O and in Me2SO-d6 by 1H- and 13C-nmr. In order to clarify or refine some details, successive substitutions of the residues in these peptides with amino acids enriched to 85% in 13C, or to 85% 13C plus 97% 2H were carried out. The 1H and 13C chemical shifts as well as the 1H-1H, 13C-13C, and 13C-1H coupling constants and the signal intensities show strong similarity of behavior between the tetrapeptides of asparagine and leucine. The main conformational characteristics are (1) the almost total stabilization of the trans conformer in the type I β-turn structure when the peptide is in the zwitterion state dissolved in Me2SO. This is deduced from the 3JC3αH-N3H and the 3JC2′-H3α coupling constants, which both furnish a dihedral angle of φ3 = -90°, and from the positive value of the temperature coefficient of the glycine-4 amide protons, which suggests a type 4 → 1 hydrogen bond; (2) the evolution of cis and trans isomer fractions which change with the ionic state of the peptides in Me2SO, whereas they remain constant in aqueous solution; and (3) the conformation of the pyrrolidine ring as it follows the variations in cis:trans isomer populations together with the side-chain rotamer fractions of the residue in position 3. In the β-turn conformation the isomer cis is less abundant and the pyrrolidine ring is more flexible; this explains the perfect accommodation of the proline residue in position 2 of a bend. The interdependence of these phenomena where interactive forces play a predominant role underlines the importance of cooperative effects in the molecule. The results also suggest that the cis isomer of proline can adapt itself just as well as the trans isomer to position 2 of a type I β-turn.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1980.360190406
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  • 5
    Electronic Resource
    Electronic Resource
    Transport properties of particles with segmental flexibility. II. Decay of fluorescence polarization anisotropy from hinged macromolecules (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 913-930 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An algorithm is presented for the Monte Carlo simulation of the decay of fluorescence polarization from segmentally flexible molecules. Based on the random walk model of Brownian motion, the treatment explicitly follows the stochastic changes in the diffusion coefficients as the molecule bends. It includes the effects of a linear restoring force opposing the bending and the effects of hydrodynamic coupling between the translational, rotational, and bending motions. One application is presented: the simulation of anisotropy decay curves for hinged rods. A variety of decay curves are obtained, including single- and multiexponential behavior, and the following conclusions are reached: (1) increasing the flexibility is usually, but not always, accompanied by a more rapid rate of depolarization; (2) reducing the size of the fluorescent subunit will usually, but not always, increase the rate of depolarization; and (3) the complex interplay between the effects of molecular shape, relative sizes of the subunits, restoring force, and orientation of the transition dipoles renders it unlikely that any simple method can be used to interpret anisotrophy data without simulation. In particular, it is not possible to determine the extent of bending by fitting the data with the two-exponential approximation used by some investigators in the past.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1980.360190414
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  • 6
    Electronic Resource
    Electronic Resource
    13C-nmr spectroscopy of red algal galactans (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 977-990 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 13C-nmr spectra of red seaweed galactans, belonging to the agar and carrageenan groups or having the “intermediate” type of structure, were interpreted on the basis of 13C-nmr spectra of model compounds. Signal assignments have been made for most of the known extreme structures of such galactans. 13C-nmr spectroscopy was shown to be a rapid and convenient method of structural analysis, which permits one to determine the type of galactan structure, the absolute configurations of its constituents (galactose and 3,6-anhydrogalactose), and the positions of the sulfate and O-methyl groups in a polysaccharide molecule.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1980.360190504
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  • 7
    Electronic Resource
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    Dielectric changes in hyaluronate solutions at microwave frequencies as a function of concentration, system pH, and temperature (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 931-944 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The dielectric response of human umbilical cord hyaluronic acid in various environments has been studied at microwave frquencies using a resonant microwave cavity as a probe. Both the real and imaginary parts of complex dielectric constant and the loss tangent for hyaluronate solutions are obtained by utilizing equations for perturbation of a resonant cavity. Dielectric changes at room temperature have been observed in aqueous solutions of hyaluronic acid as a function of concentration ranging from 0 to 350 mg/ml. The data indicate the existence of ordered phases in hyaluronate solutions at selective concentrations, that is, exhibiting lyotropic-type transitions. Hyaluronate solutions at 1.5 and 3 mg/ml concentrations have been studied at various pH in the range of 6-8 and at constant ionic strength 0.1. A temperature-dependent transition in hyaluronate solution of 120 mg/ml concentration has been observed at physiological temperature. It is shown that this temperature-dependent behavior can be related to the orientational polarizability term in the Debye theory of polar molecules in liquids.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1980.360190415
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  • 8
    Electronic Resource
    Electronic Resource
    A quantitative test of Zimm's model for the rotor-speed-department sedimentation of linear DNA molecules (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 945-964 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In 1974, Zimm described a theory which predicts that the sedimentation coefficient of high-molecular-weight DNA will decrease as the rotor speed of measurement increases. In 1979, this theory was revised, and the new formula predicts speed-dependence effects that are substantially smaller than the predictions of the original version. This report describes the results of subjecting both the original and the revised versions of the theory to quantitative tests using a well-defined sucrose-gradient system and a DNA of known molecular weight (T4c DNA). T4c bacteriophage is a mutant, whose DNA contains the unmodified base cytosine, instead of the glucosylated hydroxymethylcytosine characteristic of the T-even bacteriophages, and has a molecular weight of 115 ± 3 × 106. The DNA of the wild-type phage (T4D+) was also used in some experiments.In addition to the quantitative tests, the experiments test for an effect first observed by Rubenstein and Leighton, which showed that the sedimentation coefficient measured for T2 DNA depended on the composition of the centrifuge tube used for the measurement (tube composition effect). It can be inferred from this observation that an interaction occurs between particle and tube wall during sedimentation, and this leads to a reduction in sedimentation velocity independent of the reduction in S described by Zimm's theory.The results show that in the range of 25,000-50,000 rpm, the original but theoretically incorrect form of the theory quite accurately describes the sedimentation behavior of both T4c and T4D+ DNA, although T4D+ was a special case in some respects. The revised (corrected) form of the theory predicts much less of a speed-dependence effect than that actually observed. The discrepancy between corrected theory and observation suggests that other factors (perhaps arising from the use of the swinging bucket rotor geometry) are causing the additional observed reduction in S20,w. However, the experiments show that the tube composition effect does not seem to be one of these.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1980.360190502
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  • 9
    Electronic Resource
    Electronic Resource
    Proton NMR study of the interaction of cis-dichloro-diamine-platinum(II) with poly(I) and poly(I)·poly(C) (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1299-1309 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The fixation of cis (NH3)2Cl2Pt(II) to poly(I)·poly(C) leads to the formation of two complexed species. One involves coordination to a single base (accounting for about 70% of the total platinum bound over the rb range 0.07-0.25) and the other to two bases which are not adjacent to each other but may be on the same strand and separated by a loop. Reaction of the platinum compound with poly(I) gives in addition to the above two species a minor one (about 15%, independent of rb over the range 0.05-0.30) in which the platinum is bound to two adjacent bases. The availability of such coordination reduces the dominance of the 1:1 species, which, however, remains the major one (ca. 55%).
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1980.360190706
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  • 10
    Electronic Resource
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    Heavy-atom effects associated with methylmercury (II) binding to rabbit glyceraldehyde-3-phosphate dehydrogenase (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1329-1344 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The complex of CH3Hg(II) with the accessible cysteines of glyceraldehyde-3-phosphate dehydrogenase (GAPD, EC 1.2.1.12) from rabbit muscle has been studied by phosphorescence and optically detected magnetic resonance (ODMR) spectroscopy. The wavelength dependence of the phosphorescence decay kinetics has also been measured. Comparison of CH3Hg(II)-GAPD with GAPD by these methods shows that a specific optically resolved tryptophan site of GAPD is perturbed by the interaction with a nearby mercury atom. The perturbation on the luminescence and ODMR properties is typical of an external heavy-atom effect. Based on the x-ray diffraction structure of the lobster enzyme, it is proposed that the heavy-atom effect results from the interaction of tryptophan-310 with CH3Hg(II) bound to cysteine-281 in the rabbit muscle enzyme.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1980.360190709
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  • 11
    Electronic Resource
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    Interaction of spermine with different forms of DNA. A conformational study (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1415-1434 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The energy of interaction of a spermine molecule with the A- and B-forms of DNA has been calculated, assuming that the molecule of spermine is fixed in the narrow groove of the DNA helix with the formation of hydrogen bonds between the amino groups of spermine and the phosphate groups of DNA. The atom-atom potentials method was used. Optimal structures for the A-DNA-spermine and B-DNA-spermine complexes are suggested. It is shown that, in agreement with the experimental data, the interaction of the spermine molecule with the A-DNA is energetically more favorable than that with the B-DNA. Two main factors are responsible for this: (1) the distance between neighboring phosphates of the chain in A-DNA (which is about 1 Å less than that in B-DNA) corresponds better to the distance between the amino groups of the propyl part of spermine; and (2) the orientation of phosphate groups in A-DNA inside the groove is preferable for complex formation with spermine to the outside groove arrangement of the phosphates in B-DNA. These conclusions are further confirmed by the calculations for DNA-propane diamine complexes.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1980.360190802
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  • 12
    Electronic Resource
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    Crystal and molecular structure of isoleucinomycin, cyclo[-(D-Ile-Lac-Ile-D-Hyi)3-](C60H102N6O18) (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1517-1534 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The crystal structure of a synthetic analog of valinomycin, cyclo[-(D-Ile-Lac-Ile-D-Hyi)3-] (C60H102N6O18), has been determined by x-ray diffraction procedures. The crystals are orthorhombic, space group P212121, with cell parameters a = 11.516, b = 15.705, c = 39.310 Å, and Z = 4. The atomic coordinates for the C, N, O atoms were refined in the anisotropic thermal motion approximation and for the H atoms in the isotropic approximation. Values of standard (R) and weighted (Rw) reliability factors after refinement are 0.073 and 0.056, respectively. The structure is completely asymmetric. The cyclic molecular backbone is stabilized by six intramolecular hydrogen bonds N—H…O=C, five bonds being of the 4→1 type and one being of the 5→1 type. The side chains are located on the molecular periphery. The conformational state of isoleucinomycin in the crystal is intermediate between the corresponding crystalline states of valinomycin and meso-valinomycin. The observed conformation suggests that complexation could proceed via entry of the ion at the face possessing the L-Lac residues, the less crowded face.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1980.360190808
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  • 13
    Electronic Resource
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    Conformational analysis of the milk oligosaccharides (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1555-1566 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Possible conformations of lacto-N-tetraose, lacto-N-neotetraose, related disaccharides, and other milk oligosaccharides have been studied by an energy-minimization procedure using empirical potential functions. Lacto-N-tetraose favors a “curved” conformation, while lacto-N-neotetraose favors an approximately “straight” conformation. These two conformations differ mainly in the position of the terminal galactose residue with respect to the rest of the molecule. This difference explains the greater strength of lacto-N-neotetraose compared with lacto-N-tetraose in its ability to inhibit the cross-reaction of blood group P1 fractions with Type XIV pneumococcal antipolysaccharide. Although the favored conformation of lacto-N-tetraose (inactive) agrees with the model proposed by the earlier workers, that for lacto-N-neotetraose (active) differs. The favored conformations for the disaccharides galactose-β(1-4)-N-acetylglucosamine, galactose-β(1-3)-N-acetylglucosamine, and lactose are similar in overall shape, differing only in the nature and orientation of the side groups. This explains their nearly equal inhibitory activity. These theoretical models also explain the increased activity of lacto-N-fucopentaose I over that of lacto-N-tetraose and the relative activities of the substituted lactoses. The present studies suggest that it is the overall shape of the molecule which is important for activity, rather than the terminal β(1-4)-linked galactose residue alone.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1980.360190811
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  • 14
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    Influence of methanol on the rotational diffusion of poly(L-lysine) in the helix-coil transition (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1571-1585 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 13C spin-lattice relaxation times of poly(L-lysine) have been obtained at 67.9 MHz in aqueous solution and in a mixed solvent (40% methanol/60% water). A concomitant determination of the conformation by CD permits the correlation of conformation and rotational diffusion of the polymer. The dependence on pH of the spin-lattice relaxation times of the 13Cα and the side-chain carbon resonances reflects the diffusional motion in the random-coil conformation, in the helix-coil transition, and in the conformation of the α-helix. In the mixed solvent the reorientational correlation time of the Cα-Hα vector increases from τ = 0.37 nsec (random coil) to τ = 12.0 nsec (α-helix). In aqueous solution the correlation time of this vector increases from τ = 0.33 nsec (random coil) to τ ≫ 11 nsec. The reorientation rates of the side-chain methylene groups in the two solvents are markedly different. The reorientation of all methylene groups is reduced in the mixed solvent.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1980.360190902
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  • 15
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    Solid-state conformation of copolymers of β-benzyl-L-aspartate with L-alanine, L-leucine, L-valine, γ-benzyl-L-glutamate, or ∊-carbobenzoxy-L-lysine (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1603-1615 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The solid-state conformation of copolymers of β-benzyl-L-aspartate [L-Asp(OBzl)] with L-leucine (L-Leu), L-alanine (L-Ala), L-valine (L-Val), γ-benzyl-L-glutamate [L-Glu(OBzl)], or ∊-carbobenzoxy-L-lysine (Cbz-L-Lys) has been studied by ir spectroscopy and circular dichroism (CD). The ir spectra in the region of the amide I and II bands and in the region of 700-250 cm-1 have been determined. The results from the ir studies are in good agreement with data obtained by CD experiments. Incorporation of the amino acid residues mentioned above into poly[L-Asp(OBzl)] induces a change from the left-handed into the right-handed α-helix. This conformational change for the poly[L-Asp(OBzl)] copolymers was observed in the following composition ranges: L-Leu, 0-15 mol %; L-Ala, 0-32 mol %; L-Val, 0-8 mol %; L-Glu(OBzl), 3-10 mol %; and Cbz-L-Lys, 0-9 mol %.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1980.360190905
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  • 16
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    Physical aging of dry elastin (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1667-1673 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dry purified ligamentum nuchae elastin has been investigated for physical aging. The samples were quenched from a temperature (197°C) close to the softening point to a number of measuring temperatures ranging from -20 to +180°C. At each temperature, the small-strain torsional creep properties were determined at a number of elapsed intervals after the quench. Aging effects were found over the whole temperature range, and the creep and aging behavior of elastin turned out to be very similar to that of synthetic polymers.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1980.360190910
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  • 17
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    DNA backbone conformation in cis-syn pyrimidine[]pyrimidine cyclobutane dimersPresented at the American Society of Biological Chemists and Biophysical Society Meeting, June 1-5, 1980, New Orleans, Louisiana [(1980) Fed. Proc. 39, 1879]. (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1695-1701 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1980.360190913
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  • 18
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    Toroidal elastic supercoiling of DNA (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1705-1713 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Covalently closed circular DNA can exist in different configurations known as circular, toroidal, and interwound. Changes among these forms can be made in several ways, including the insertion of dye molecules between adjacent base pairs, which tends to untwist the double-helical structure. The aim of this paper is to discuss these configurations, and the changes among them, in the context of classical elastomechanics. The concepts of twisting, linkage and writhing are explained. Simple experiments on a twisted linear-elastic rod are described, and it is shown that although the circular and interwound forms may be modeled in this way, the toroidal form does not occur, being mechanically unstable. Theoretical energy calculations by Levitt on bent and twisted DNA show that DNA exhibits a particular kind of nonlinear elasticity in which there is an unusual coupling between bending and twisting. The aim of the paper is to show qualitatively that this special kind of elasticity can stabilize the toroidal form of closed circular DNA.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1980.360191002
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  • 19
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    Physicochemical investigation of k-carrageenan in the random state (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1357-1374 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Light-scattering, viscosity, and sedimentation experiments on aqueous solutions of k-carrageenan show that this sulfated polygalactose is an expanded flexible random coil. This expansion is due to long-range interactions that are predominantly electrostatic. Extrapolation of viscosity data to infinite ionic strength provided values for the intrinsic viscosity which were subjected to the Stockmayer-Fixman analysis, giving a value for the Mark-Houwink coefficient under theta-conditions, Kθ, of 0.27. The characteristic ratio, C∞, under these conditions is 7.8, and the conformation factor σ is 2. In a solution of 0.118 ionic strength, where a Mark-Houwink exponent aη of 0.86 is found, the radii of gyration calculated from viscosity data are lower than those found from the angular dependence of scattered light. On the other hand, the radius of gyration found from the sedimentation rate agrees well with the light-scattering radius. The relations between molecular parameters are corrected for the poly-dispersity of the sample.
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    An interaction of albumin with hyaluronic acid and chondroitin sulfate: A study of affinity chromatography and circular dichroism (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1407-1414 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
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    Masthead (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980) 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/bip.1980.360190801
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  • 22
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    The translational friction of toroids (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1475-1489 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An approximate analytic expression for the translational friction coefficient of a toroid modeled as a continuous shell of frictional elements is derived using the Kirkwood approximation. The accuracy of this expression was determined by comparing the friction coefficients predicted by it to those predicted by extrapolated shell-model calculations using the modified Oseen tensor. To show that these calculations do indeed yield the correct friction coefficients, actual translational friction coefficients were determined by observing settling rates of macroscopic model rings or toroids in a high-viscosity silicone fluid. Our conclusion is that the approximate expression yields friction coefficients that are about 1.5-3% low for finite rings. For thin rings, a comparison is also made with the exact result of Yamakawa and Yamaki [J. Chem. Phys. 57, 1572 (1972); 58, 2049 (1973)] for the translational friction of plane polygonal rings. This comparison shows that the approximate expression yields results which are low by 2-3% unless the rings are extremely thin, in which case the error is larger. In the limit of an infinitely thin ring the approximate expression reduces to the Kirkwood result [J. Polym. Sci. 12, 1 (1954)], which is low by 8.3%. We discuss briefly how this work may be useful in determining the structure of DNA compacted by various solvent-electrolyte systems and polyamines.
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    Dynamic light scattering studies of internal motions in DNA. II. Clean viral DNAs (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1451-1474 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Internal Brownian motions of clean φ29 and λ-DNAs have been studied using photon-correlation techniques at both visible (λ0 = 632.8 nm) and uv (λ0 = 363.8 nm) wavelengths. The present dynamic light scattering data, which extend to K2 = 19 × 1010 cm-2, can in every case be satisfactorily simulated by a Rouse-Zimm model polymer with an appropriate choice of the three model parameters. The effects of pH, salt concentration, single-strand breaks, and molecular weight on those model parameters have also been investigated. Intact clean DNAs exhibit surprisingly little variation with pH from 7.85 to 10.25, with salt concentration from 0.01 NaCl to 5.4M NH4Cl, or with molecular weight or GC content. The single-strand breaks have no effect at pH 9.46, but produce dramatic changes in the model parameters at pH 10.0 and 10.25, indicating the introduction of titratable joints at those pHs. The failure of either single-strand breaks or a large change in GC content to alter the model parameters in the neutral pH range is a strong indication that local denaturation is not required for those flexions and torsions that dominate the relaxation of fluctuations in the scattered light. The Langevin relaxation time for the slowest internal mode of a particular Rouse-Zimm model derived from the dynamic light scattering data is compared with pertinent literature data extrapolated to the same molecular weight. The present algorithm for determining model parameters from the light-scattering Dapp vs K2 curve actually yields a Langevin time in fairly good agreement with the literature value. For unknown reasons the light-scattering D0 values generally exceed those obtained from the molecular weight and sedimentation coefficient by about 20%.
    Additional Material: 7 Ill.
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    Ultraviolet Raman spectroscopy of polyribouridylic acid: Excitation profile of the hypochromism induced by order-disorder transition (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1507-1515 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Raman spectra of polyribouridylic acid excited in the uv region, from 363 to 290 nm, are reported. The conformational changes of the polymer from random coil to ordered structure with stacked bases at high and low temperature, respectively, are reflected by important changes in the Raman line intensities; this Raman hypochromism is itself a function of the excitation wavelength - its profile has been determined and shows negative values in the region of 290 nm (near resonance), i.e., hypochromism becomes hyperchromism. Thus the knowledge of the hypochromism excitation profile is important in following order-disorder transition of a polymer using resonance Raman spectroscopy. Theoretical attempts are proposed for explanation, involving not only the relative variations of the molar extinction coefficient on the order-disorder transition of the polymer, but also the damping factors of the vibronic levels. The theoretical curve is found to fit adequately the experimental data over the excitation range, using only the frequency of the O-O transition of uracil and a vibronic linewidth of 2200 cm-1.
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    Interaction of poly(α-L-glutamic acid) and sodium poly(α-L-glutamate) with solvent components in water-2-chloroethanol mixtures (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 2177-2190 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preferential interaction of sodium poly(α-L-glutamate) and poly(α-L-glutamic acid) with the solvent components in water/2-chloroethanol mixtures has been determined using density-increment measurements. The degree of preferential interaction was deduced from the density increments at constant molality of 2-chloroethanol and at constant chemical potential of 2-chloroethanol. Sodium poly(α-L-glutamate) and poly(α-L-glutamic acid) are both preferentially hydrated in the whole range of solvent composition. A dehydration process occurs during the 2-chloroethanol-induced coil-to-helix transition of sodium poly(α-L-glutamate). This dehydration process was attributed to the release of some moles of water from the neighborhood of the peptide bond during the nucleation of the helix. After the conformational transition, sodium poly(α-L-glutamate) is solvated by one 2-chloroethanol molecule. The location of water and 2-chloroethanol molecules in the different parts of the residue (more polar and less polar portions) is also discussed.
    Additional Material: 5 Ill.
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    Effects of pD on ring-stacking interactions between dinucleoside phosphates and tryptamine (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 2223-2245 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Complex formation between tryptamine and mononucleotides and dinucleoside phosphates containing adenine and/or cytosine has been studied at five pD's ranging from 1.1 to 7.4 by proton magnetic resonance spectroscopy. Chemical shifts of base ring protons and the ribose anomeric proton in the nucleotides and indole ring protons in tryptamine were monitored and their changes with pD and intermolecular interactions interpreted qualitatively. Stacked complexes were found to exist at all pD's in the range studied. Complex geometries differ depending on pD. An electrostatic interaction between the tryptamine amino group and the nucleotide phosphate group contributes to complex formation above pD 4 but is not strong enough to shift the dinucleoside phosphate equilibrium towards the unstacked conformer.
    Additional Material: 5 Ill.
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    Conformational energy studies on N-methylated analogs of thyrotropin releasing hormone, enkephalin, and luteinizing hormone-releasing hormone (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1943-1973 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Empirical conformational energy calculations have been carried out for N-methyl derivatives of alanine and phenylalanine dipeptide models and N-methyl-substituted active analogs of three biologically active peptides, namely thyrotropin-releasing hormone (TRH), enkephalin (ENK), and luteinizing hormone-releasing hormone (LHRH). The isoenergetic contour maps and the local dipeptide minima obtained, when the peptide bond (ω) preceding the N-methylated residue is in the trans configuration show that (1) N-methylation constricts the conformational freedom of both the ith and (i + 1)th residues; (2), the lowest energy position for both residues occurs around φ = -135° ± 5° and ψ = 75° ± 5°, and (3) the αL conformational state is the second lowest energy state for the (i + 1)th residue, whereas for the ith residue the C5 (extended) conformation is second lowest in energy. When the peptide bond (ωi) is in the cis configuration the ith residue is energetically forbidden in the range φ = 0° to 180° and ψ = -180° to +180°. Conformations of low energy for ωi = 0° are found to be similar to those obtained for the trans peptide bond. In all the model systems (irrespective of cis or trans), the αR conformational state is energetically very high. Significant deviations from planarity are found for the peptide bond when the amide hydrogen is replaced by a methyl group. Two low-energy conformers are found for [(N-Me)His2]TRH. These conformers differ only in the φ and ψ values at the (N-Me)His2 residue. Among the different low-energy conformers found for each of the ENK analogs [D-Ala2,(N-Me)Phe4, Met5]ENK amide and [D-Ala2,(N-Me)Met5]ENK amide, one low-energy conformer was found to be common for both analogs with respect to the side-chain orientations. The stability of the low-energy structures is discussed in the light of the activity of other analogs. Two low-energy conformers were found for [(N-Me)Leu7]LHRH. These conformations differ in the types of bend around the positions 6 and 7 of LHRH. One bend type is eliminated when the active analog [D-Ala6,(M-Me)Leu7]LHRH is considered.
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    Interactions of molecules with nucleic acids. III. Steric and electrostatic energy contours for the principal intercalation sites, prerequisites for binding, and the exclusion of essential metabolites from intercalation (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 2067-2089 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Based on steric and electrostatic considerations, the prerequisites for binding to DNA via the intercalation mechanism are proposed. Steric contour energy curves are presented to demonstrate the region inaccessible to an intercalant. They are calculated with a 6-n (n = 14) potential. This method is a soft potential analog of an excluded-volume approach. Electrostatic contours on the steric surface illustrate the relatively positive and negative regions of the binding site. The principal intercalation sites, predicted to fit into B-DNA via a tetramer-duplex unit, and the unconstrained dimer-duplex units, obtained in crystal structures, are examined. These contours illustrate the requirements of size, conformation, and net atomic charges necessary for intercalation and optimum binding. Based on the limited space available for intercalation by the presence of the backbone and the maximum base-pair separation of 8.25 Å, an Essential Metabolite Exclusion Hypothesis is presented.
    Additional Material: 9 Ill.
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    The chiroptical properties of proteins. II. Near-ultraviolet circular dichroism of lysozymeTaken in part from the Ph.D. dissertation of W. J. G. (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 2191-2208 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A study of the near-uv CD spectrum of lysozyme was carried out in the presence and absence of the inhibitor tri-N-acetylglucosamine, and theoretical chiroptical calculations based on the tetragonal crystal structure of the enzyme and the enzyme-inhibitor complex were performed. The results of these calculations indicate that the near-uv CD spectrum of lysozyme can be adequately explained in terms of negative rotatory strengths arising from the tryptophan 1La (293-300 nm) and the disulfide n-σ* bands (250 rm), and positive rotatory strength contributions from the tryptophan 1Lb bands (291 nm) and the tyrosine 1Lb bands (275 nm). Contributions to the rotatory strength of each band were approximated in terms of specific interactions between chromophores. It was found that the rotatory strength of most of the near-uv transitions arises primarily from coupling interactions involving other side-chain chromophores and amide groups which are in close proximity. Changes which are observed in the lysozyme CD spectrum on binding of tri-N-acetylglucosamine may be explained in terms of changes in the rotatory strength which result from interactions of the 1La transitions of the active-site tryptophans with the acetamide groups of the inhibitor. The reasonable agreement which is found between the experimental and calculated rotatory strengths implies that the crystal conformation of lysozyme must resemble the solution conformation.
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    Relationship between conformation and physicochemical properties of polypeptides. I. Synthesis of homo- and co-oligopeptides by the liquid-phase method (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 173-187 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of the following oligo- and co-oligopeptides by the liquid-phase method is described: (L-Met)15 (I), [L-Glu(OBzl)]20 (II), (L-Val)8-Gly (IV), (L-Ile)8-Gly (V), (L-Ile)4-Gly-(L-Ile)4 (VI), (L-Ile)4-Pro-(L-Ile)4 (VII), (L-Met)5-L-Pro-(L-Met)5 (VIII), [L-Glu(OBzl)]7-L-Pro-[L-Glu(OBzl)]7 (IX). The oligomers are covalently bound to bifunctional polyethylene glycol (PEG) and monofunctional PEG-M of Mr 5 × 103-2 × 104. Analytical controls were carried out after each step of synthesis in order to ensure quantitative coupling yields. All products could be obtained in high purity as indicated by amino acid analysis, thin-layer chromatography and chiroptical methods. The solubility of the oligomers was strongly enhanced by the presence of the C-terminal PEG group, enabling conformational investigations in a variety of solvents. A significant relationship between conformation and physicochemical properties of the oligopeptides was observed. Oligomers with tendencies to adopt α-helical (I, II) or unordered structures (VI-IX) showed no pronounced change in solubility or coupling kinetics during chain elongation, whereas the onset of a β-structure (IV, V) was paralleled by a drastic decrease in solubility and reactivity of the terminal amino groups. Most notably, the insertion of a proline or glycine in the middle of a β-forming peptide chain (VI, VII) resulted in a considerable increase in solubility compared to the corresponding homo-oligomers. The impact of the conformational properties of a peptide chain on strategic considerations of peptide synthesis in solution is delineated.
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    Circular dichroism and conformational analysis of the membrane-modifying peptide -N-t-Boc-(Aib-L-Ala)5-Gly-Ala-Aib-Pro-Ala-Aib-Aib-Glu-(OBzl)-Gln-OMe with respect to alamethicin (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 203-214 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformational analysis of the CD spectrum is reported for the synthetic and membrane-modifying nonadecapeptide analog of alamethicin N-t-Boc-(Aib-L-Ala)5-Gly-Ala-Aib-Pro-Ala-Aib-Aib-Glu(OBzl)- Gln-OMe. The CD data are evaluated according to three different methods and are discussed with respect to those obtained from natural alamethicin and suitable models such as N-t-Boc-(Aib-L-Ala)7-OPOE, fragments of the synthetic nonadecapeptide, and the hexadecapeptide N-t-Boc-(Aib-L-Ala)5-Pro-Ala-Aib-Aib-Glu(OBzl)-Gln-OMe. The synthetic nonadecapeptide with the longer helical region exhibits membrane activities comparable to those of alamethicin, whereas the hexadecapeptide with the shorter helix is inactive.
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    Masthead (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980) 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/bip.1980.360190201
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    Dynamic light scattering in a flow - a new method of particle anisotropy investigation (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 231-240 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology
    Notes: This paper deals with the light scattering from particles rotating in a flow with a transverse velocity gradient. It is theoretically substantiated and experimentally proved that the scattered light spectrum contains reliable information of the particle configuration and dimensions. The proposed technique may prove also very promising for the analysis of particle polydispersion.
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    Poly(ε-L-lysine): Synthesis and conformationPart of this work was presented at the International Symposium on Biomolecular Structure held in Madras, India, in January 1978. (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 219-229 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of poly(ε-L-lysine) is described. This is a poly(ε-amino acid) in which the ε-amino group of lysine is condensed with the α-carboxyl group to produce a chain backbone that is a variant of the usual one seen in proteins and the side chain is the α-amino group. Conformational studies of poly(ε-L-lysine) and its t-butyloxycarbonyl derivative suggest the likelihood of a chain order that is formally similar to the antiparallel pleated-sheet conformation of proteins.
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    Contribution of electrodiffusion to the dynamics of electrically stimulated changes in mechanical properties of collagen membranesPresented at the Third International Congress of Biorheology, August 28-September 1, 1978, La Jolla, California. (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 241-262 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have studied the kinetics of oscillatory tensile forces in collagen membranes. These forces were generated by sinusoidal electric fields applied across the membrane. Both the magnitude and phase of the measured force changed with frequency over a three-decade range. The membrane-separated electrolyte baths had different ionic strength but identical non-isoelectric pH. Changes in intramembrane ionic strength due to the electric field were calculated over the same frequency range via an electrodiffusion model that was generalized to include convection and electrokinetic coupling. A comparison of the experimental and theoretical phases and amplitudes versus frequency suggests that electrodiffusion is the dominant rate-limiting process in this electromechanochemical transduction. These results are relevant to electrostatic interactions in connective tissues and to membrane-based filtration devices in which membrane permeability may be actively varied and controlled by an applied electric field.
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    Heat capacity changes and partial molal heat capacities of some di- and tripeptides in water (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 263-272 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Integral enthalpies of solution of several dipeptides and tripeptides in water at low concentrations have been determined at 25 and 35°C. These data have been used to derive the changes in heat capacity on dissolution at infinite dilution ΔCp0 at 30°C. Limiting partial molal heat capacities ΔCp20 have been determined by combining ΔCp0 with Cp2 (heat capacity of pure solid peptides). Using the data on ω-amino acids and these peptides, the partial molal heat capacity of a peptide group —CONH— was semiquantitatively estimated.
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    Heat capacities of transfer of some amino acids and peptides from water to aqueous urea solution (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 273-284 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Integral enthalpies of solution at low concentrations of several amino acids and peptides in 2 and 6M urea solutions have been determined at 25 and 35°C. These data have been used to derive the enthalpies of transfer (at 25 and 35°C) and heat capacities of transfer (at 30°C) of these amino acids and peptides from water to aqueous urea solutions. Furthermore, the enthalpies of transfer and heat capacities of transfer per CH2 group and per peptide group —CONH— have also been estimated. These results show that while the enthalpies and heat capacities of transfer per CH2 group are positive and negative, respectively, the reverse is true for —CONH— group. The implications of these results in the mechanism of the denaturation of proteins by urea are discussed.
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    Studies on transfer ribonucleic acids and related compounds. XXVI.Paper XXV: Ohtsuka, E., Miyake, T. & Ikehara, M. (1979) Chem. Pharm. Bull. 27, 341-345. Circular dichroic properties of cyclic oligoribonucleotides and their linear counterparts (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 285-296 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The CD spectra of cUpUp, cCpCp, and cGpGp derived from DCC-catalyzed polymerization of the relevant protected ribonucleoside 3′-phosphates are described. Similar studies on Up, U 〉 p, and cUp, as well as cUpUpUp and cUpUpUpUp, are presented. The spectral properties of the cyclic oligomers are compared with those of the corresponding linear oligomers with terminal 3′-phosphates so as to demonstrate that disruption of normal right-handed base stacking is considerable in these RNA loops.
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    Chemical synthesis of (1 → 2)-α-D-mannopyranan (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 297-309 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The polymerization of 1,2-anhydro-3,4,6-tri-O-benzyl-β-D-mannopyranose proceeds in the presence of Lewis acids, cationic coordination catalysts, and strong bases. Debenzylation of the products yields oligomeric saccharides or low polymers. Polymerization in toluene by means of potassium alkoxide complexed with crown ethers leads to essentially stereoregular (1 → 2)-α-D-mannopyranan. The original derivatives have been characterized by optical rotation, viscosity, molecular weight, gel permeation chromatography, and spectrometry. The free polysaccharides have been characterized by optical rotation, molecular weight, and 1H- and 13C-nmr spectrometry and compared to yeast mannan hydrolysate oligomers.
    Additional Material: 4 Ill.
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    Physical association of two simple alkylators to some DNA sequences (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 311-324 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Molecular mechanics calculations have been used to determine the preferred physical association sites of the known alkylating agent dimethyl aziridinium ion (Az+) and a CH3+ prototype test probe with B-form, tetrameric DNA sequences. Electrostatic interactions are most important in determining these preferential physical association sites. In turn, the intermolecular energy minima depend on the charge distribution assigned to the DNA sequence. However, for three reported DNA charge distributions, only two distinct sets of energy minima were obtained for the CH3+-like ion interacting with (G-C)4, (A-T)4, and [(G-C)·(A-T)]2 deoxyribonucleic acids. These minima correspond to physical association geometries in which the CH3+-like ion is near known alkylation sites. The results of the Az+ … [(G-C)·(A-T)]2 interaction are virtually identical to those found for the CH3+-like ion. Aqueous solvation energetics have little effect on the physical association of Az+ with [(G-C)·(A-T)]2.
    Additional Material: 6 Ill.
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    Chemical reactivity of protonated aziridine with nucleophilic centers of DNA bases (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 325-340 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of molecular orbital calculations, using MINDO/3 and CNDO/2L methods, have been used to characterize the chemical reaction of protonated aziridine with DNA nucleophilic base sites. The N-7 atom of guanine is found to be the preferred alkylation site only when the O-6 atom of guanine is involved in base-pair hydrogen bonding. Otherwise O-6 is the predicted major site of alkylation. This indirectly suggests that protonated aziridine alkylation processes involve base-paired DNA structures, since N-7 guanine is the observed major site of alkylation. Alkylation of N-3 adenine is predicted to be more favorable than chemical attack of the N-7 adenine position. Both of these sites, however, are predicted to be less reactive than N-7 of guanine. These chemical reactivity studies resolve alkylation specifically not achieved in the DNA-alkylator physical association calculations reported in the preceding paper.
    Additional Material: 12 Ill.
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    Conformational analysis of somatostatin and selected analogs in oriented polyoxyethylene by infrared dichroism (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 341-352 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Infrared dichroic studies and deuterium exchange measurements of somatostatin and some of its analogs incorporated in uniaxially oriented polyoxyethylene are described. Band positions and dichroic ratios in the N-H stretching and amide I and II regions are similar to those of flexible and nonordered peptides like valinomycin and poly[Glu(ONa)]. This information, together with fast deuterium exchange rates, suggests that somatostatin exists in a flexible nonordered conformation in polyoxyethylene. One analog, di-S3,14-acetamidomethyl dihydrosomatostatin, was found to exist in both nonordered and β-like conformations.
    Additional Material: 3 Ill.
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    Monte carlo simulation of the solvent structure in crystals of a hydrated cyclic peptide (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 395-418 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Monte Carlo simulation of the structure of the 16 ordered and disordered waters in the unit cell of crystals of the cyclic peptide cyclo(-L-Ala-L-Pro-D-Phe)2 is reported. The water structure has been characterized in terms of the statistically averaged positions of the individual molecules, their root-mean-square movements about these positions, the probability of finding a water in a given spatial position in the crystal (probability maps), and examination of individual configurations of the system. In this way a picture is obtained of the water structure, including water orientations (hydrogen positions), the hydrogen-bonding network, and fluctuations in these structural features, to a degree hitherto unavailable either from experimental or theoretical studies. In addition, the variation in water structure in various peptide environments was studied and correlated with the energetics of the individual water molecules. Variations in the crystalline environment of different water molecules lead to energy differences of as much as 4-5 kcal/mol in their average energies. Similarly, differences are observed in the water-peptide and water-water components of the energy. Two different water potentials were tested. The results were compared with experimental data in terms of mean positions, root-mean-square movements, and the Fourier transform of the simulated water structure. The agreement factor (R factor) calculated from the theoretical water probability distribution was 18.8% compared to the x-ray value of 14.5%, and the value of 28% when the water is omitted.
    Additional Material: 6 Ill.
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    Masthead (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980) 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/bip.1980.360190301
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    Polymeric model system for protein-bilirubin interaction (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 445-448 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1980.360190217
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    Conformational flexibility of peptides containing α,β-unsaturated amino acid residues. I. Conformational analysis of N-acetyl-N′-methylamides of dehydroalanine and N-methyldehydroalanine (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 469-475 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conformational energy calculations on the N-acetyl-N′-methylamides of dehydroalanine and N-methyldehydroalanine indicate that their conformational behavior is very different from that of the corresponding saturated compounds. The conformational data in the literature from x-ray and nmr investigations on peptides containing α,β-unsaturated residues are discussed on the basis of these theoretical results.
    Additional Material: 4 Ill.
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    Synthesis and ordered structure of amphipatic block copolymers with a saccharide and a peptide block (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 493-507 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Amphipatic block copolymers (OβEb) with a hydrophilic saccharide block and a hydrophobic polypeptide block were synthesized. In these copolymers the saccharide block is the glyco-amino acid Oβ from ovomucoid and the peptide block (Eb) is a poly(γ-benzyl-L-glutamate) block. Copolymers OβEb exhibit, in the solid state and in Me2SO concentrated solutions, mesomorphic lamellar structures where the polypeptide chains are in an α-helical conformation. Depending on the molecular weight of the polypeptide block, three types of lamellar structures are obtained, and they differ by the mode of organization of the polypeptide chains in their lamellae and by the T or Y conformation of the saccharide block.
    Additional Material: 9 Ill.
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    Spectroscopic and equilibrium dialysis studies of poly(α-L-glutamic acid)-Cu(II) complexes in the pH range 4-7For the preceding paper of the Macromolecule-Metal Ion Complex series, see Macromolecules 12 (1979) in press. (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 477-491 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The formation of complex between the Cu2+ ion and poly(α-L-glutamic acid) [poly(Glu)] in 150 mM NaCl solutions was studied by uv-visible absorption and equilibrium dialysis methods at the mixing ratios of Glu residues to Cu2+, R, of 32, 16, and 8 and in the pH range 4-7. The results showed that more than 90% of Cu2+ ions bind to the poly(Glu) at pH 〉 4.9, but the bound Cu(II) begins to dissociate with a decrease in pH. The absorption spectra of bound Cu(II) varied with pH and R in a complicated manner. Three different component spectra were disclosed from the analysis of the pH dependence of the bound spectra. We concluded that poly(Glu)-Cu(II) complexes fall into three classes in the pH range 4-7, with the proportions of these complexes varying with both pH and R. The three complexes predominate either in the helix or extended-coil region, in the helix-coil transition region, or in the helix-aggregate region. The stability constant and binding mode of each Cu(II)-Glu complex were estimated from the dialysis data. With these results, the possible structure of each complex is discussed.
    Additional Material: 9 Ill.
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    Nearest-neighbor and next-nearest-neighbor effects in the proton NMR spectra of the oligoribonucleotides ApGpX and CpApX (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 557-573 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The variable-temperature proton nmr spectra of the oligoribonucleotides in the series CpApX and the series ApGpX, X = A, G, C, U, together with the parent dimers CpA and ApG have been measured. A complete analysis of all the nonexchangeable base proton resonances and ribose H-1′ proton resonances was made. The presence of trends in the shielding abilities of the various bases at both the nearest-neighbor and next-nearest-neighbor positions were identified. The observed shieldings could be used to predict the chemical shifts of protons in related systems. Based on the empirical results from ribodinucleoside monophosphates, the temperature-dependent behavior of the J1′2′ coupling constants of the triribonucleotides suggested that the compounds in the CpApX series stacked from the 5′-end to the 3′-end, while those in the ApGpX series stacked from the 3′-end to the 5′-end.
    Additional Material: 7 Ill.
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    Monte carlo computation of the supercoiling energy, the sedimentation constant, and the radius of gyration of unknotted and knotted circular DNA (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 619-637 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Closed random Gaussian polygonal chains of N (6 〈 N 〈 150) bonds of equal length b and thickness d have been generated on a computer. The knot type, the writhing number w, the radius of gyration, and the average of the inverse of the distance between two apices have been determined for each chain. For all the studied knot types - 0, 31, 41, 51, and 52 - the probability density of finding a given w is Gaussian. The Gaussian is centered about 0 for the amphichiral knots. Therefore, for long circular DNAs, the contribution to the supercoiling energy, which depends on w only, may be considered as purely entropic and may be expressed as ARTw2/N, in agreement with previous semiempirical considerations. The parameter A increases with chain thickness, it decreases as N gets larger but rapidly reaches a plateau. Comparison with experimental data from the literature would suggest that the ratio of the writhing to the constraint increases with ionic strength. The ratio of sedimentation constant of the supercoiled DNA to the sedimentation constant of the nicked DNA varies as N1/4 (w/N)2, and therefore depends on the writhing density and on the length of the DNA.
    Additional Material: 10 Ill.
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    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 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Additional Material: 7 Ill.
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    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 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
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    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 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
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    Electrical conductivity of single crystals of lysozyme (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 669-679 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
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    Transport properties and hydrodynamic centers of rigid macromolecules with arbitrary shapes (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 751-766 
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
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    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 
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    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/ciuz.19800140207
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    Flüssiger Schwefel - ein Rohstoff komplizierter Zusammensetzung (1980)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 14 (1980), S. 73-81 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/ciuz.19800140302
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    Kleben und Klebstoffe (1980)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 14 (1980), S. 124-133 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 8 Ill.
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    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 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/ciuz.19800140406
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    Chronik (1980)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 14 (1980), S. 176-176 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
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    URL: http://dx.doi.org/10.1002/ciuz.19800140506
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    Ethische Ziele und natur-wissenschaftliche Entwicklung. Probleme einer vernachlässigten Beziehung (1980)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 14 (1980), S. 168-175 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/ciuz.19800140505
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    Bioaktive Siliciumverbindungen (1980)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 14 (1980), S. 197-207 
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    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/ciuz.19800140605
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    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
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/ciuz.19800140607
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    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 
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    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/ciuz.19800140609
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    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
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
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    Unwinding of DNA induced by fluorescein mercuric acetate (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 991-999 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Additional Material: 6 Ill.
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    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 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Additional Material: 12 Ill.
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    β-Chain conformation of the high-sulfur proteins from wool (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1093-1097 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1980.360190512
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    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 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Additional Material: 10 Ill.
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    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 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Additional Material: 7 Ill.
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    Effect of counterions on complex coacervation (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1289-1298 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
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    Dielectric relaxation of DNA solutions. IV. Effects of salts and dyes (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1039-1047 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Additional Material: 8 Ill.
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    Models for boundary effects on molecular rotation in membranes (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1597-1602 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
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    Cation effects on the nonlinear electrical properties of DNA solutions (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1629-1640 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Additional Material: 5 Ill.
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    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 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
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    Microscopic persistence length of native DNA: Its relation to average molecular dimensions (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1689-1694 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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    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 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/bip.1980.360190914
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    Masthead (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980) 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/bip.1980.360191001
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    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 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
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    1H-nmr study of protected methionine homo-oligopeptides in helix-supporting environment (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1791-1799 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
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    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 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
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    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 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
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    Masthead (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980) 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/bip.1980.360191101
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    Fluorine nmr studies of poly(N-acryloyl-β-alanine)-α-chymotrypsin conjugates (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1827-1837 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
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    Concentration distribution and spatial moments of moving macromolecules undergoing isomerization (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1875-1886 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1980.360191014
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  • 86
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    Triple helix-coil transition of covalently bridged collagenlike peptides (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1909-1917 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1980.360191017
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  • 87
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    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
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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).
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1980.360191102
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    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
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1980.360191105
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  • 89
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    Helix-coil transitions in a simple polypeptide model (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 2033-2045 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1980.360191108
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  • 90
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    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
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1980.360191112
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  • 91
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    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
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1980.360191113
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  • 92
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    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
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1980.360191202
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  • 93
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    A theory for polarized fluorescence microscopy of chromosome structures (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 2267-2267 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1980.360191209
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    DNA bis-intercalation: Theoretical calculation of binding curves (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 419-430 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1980.360190215
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    DNA bis-intercalation: Application of theory to the binding of echinomycin to DNA (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 431-443 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1980.360190216
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    Analysis of high-resolution melting (thermal dispersion) of DNA. Methods (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 681-700 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/bip.1980.360190316
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    mini-chiuz (1980)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 14 (1980), S. A26 
    Details
    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ciuz.19800140309
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    Wasser. Lösungsmittel, Lebensraum und Ökofaktor. Von R. Wittig. Akademische Verlagsgesellschaft, Wiesbaden 1979. VIII, 184 S., Zeichn. u. Tab., kart. DM 24, - (1980)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 14 (1980), S. 103-103 
    Details
    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ciuz.19800140306
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  • 99
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    Die Biosynthese von Antibiotica-Peptiden (1980)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 14 (1980), S. 105-114 
    Details
    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ciuz.19800140402
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    Das Ei des Columbus - Ein Energiebilderbuch von F. Vester. Kösel-Verlag, München 1979. 18 S. Begleitbroschüre, Spiralheftung, DM 14,80 (1980)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 14 (1980), S. 134-134 
    Details
    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ciuz.19800140407
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