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  • 1
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 717-738 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new procedure for evaluating u and σ characterizing σ-helix-forming polypeptides in solution was derived from Nagai's theory for the helix-coil transition of such polymers. Here u is the activity for helix formation from random coil, and σ is the helix initiation parameter. The necessary data are the helical content fN at fixed solvent and temperature as a function of N, where N is the degree of polymerization of the polypeptide sample. Such data were obtained from ORD measurements on a number of fractionated samples of poly-N5-(3-hydroxypropyl)-L-glutamine (PHPG) in mixtures of water and methanol covering the complete range of composition and at various termperatures (5-40°C). When analyzed in terms of the proposed procedure, they yielded values of σ which were in the range (3.2 ± 0.6) × 10-4, substantially independent of solvent composition and temperature. These values were much larger than those obtained recently for σ of poly(β-benzyl-L-aspartate) in m-cresol and in a mixture of chloroform and DCA. The data for [η] and s0 (limiting sedimentation coefficient) as functions of molecular weight indicated that the molecular shape of PHPG in pure methanol is essentially rodlike, whereas that in pure water is not entirely randomly coiled but rather may be regarded as an interrupted helix. These indications were consistent with the results from ORD measurements. When plotted against the corresponding values of fN, the values of [η] and [s0] for PHPG in mixtures of water and methanol of various compositions and temperatures formed smooth composite curves, and we attributed these phenomena to the fact that σ of PHPG was nearly constant under these solvent conditions. Here [s0] stands for a reduced limiting sedimentation coefficient which is equal to the inverse friction factor of the solute molecule.
    Additional Material: 17 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 1177-1195 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Measurements of light scatting, sedimentation equilibrium, sedimentation velocity, and viscosity were carried out on fractions of native amylose in dimethylsulfoxide at 25°C. The data for statistical radius as a function of weight-average molecular weight Mw suggested a stiff nature of this biopolymer in the solvent studied when interpreted in terms of Kirste's recent calculations with a stiff chain model. The data for sedimentation coefficient were consistent with this suggestion, and when analyzed in terms of the theory Hearst and Stockmayer for wormlike chain, a value of 233 Å2 was obtainedd for a/λ, where a is the length of a monomer unit projected on the chain axis and (2λ)-1is the persistence length of the wormlike chain. The intrinsic viscosity data gave a high a value as 0.91 for the exoponent in the Houwink-Mark-Sakuarada equation, in Substantial agreement with Cowie's prenious work.We attempted to interpret these data by use of the Eizner-Ptitsyn equation for wormlike chains, with omission of the free-drainage term and introduction of the a/λ value obtained from sedimentation data. It was found that, except in the region of Mw above one million, the observed values were fitted well by the E-P theory with a = 1.4 Å and (2λ)-1 = 87 Å. The disagreement in the high-molecular-weight region was tentatively attributed to excluded volume effect. The a value obtained suggests that the molecular conformation of amylose in dimethylsulfoxide is predominantly helical, in contrast to that of the same polymer in aqueous solutions of simple electrolyte. It was also found that a similar value of a was derived from our data for the second virial coefficient and partial specific volume if the molecule was assumed to be essentially rodlike.
    Additional Material: 11 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 10 (1972), S. 23-42 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Statistical radii of gyration, second virial coefficients, and intrinsic viscosities of sharp fractions (M̄w/M̄n ≈ 1.1) of polyisobutylene (PIB) covering a wide range of molecular weight (1.6 × 105 to 4.7 × 106) were determined in isoamyl isovalerate (IAIV) at a number of temperatures ranging from 20 to 60°C, in n-heptane at 25°C, and in cyclohexane at 25°C by light-scattering and viscosity measurements. It was found that IAIV at 22.1°C is a theta solvent for PIB. Analysis of the data by the methods described in preceding papers of this series indicated that, except for minor differences, the conclusions derived from similar studies with polychloroprene, polystyrene, and poly-p-methylstyrene hold equally for solutions of the typical linear polymer investigated here. In particular, no decisive evidence for the drainage effect was found.
    Additional Material: 14 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 8 (1969), S. 633-645 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The binding curves of 1-, 2-, 3-, and 9-aminoacridine and proflavine on native DNA and the circular dichroism (CD) spectra of the bound cations have been determined under the same conditions. The variation of the CD spectra with the amount (r) of aminoacridine bound per DNA phosphorus was of two main kinds: (1) the rotational strength of those aminoacridines which possess a 3-amino group depended markedly on r and decreased to relatively small values (or zero) at zero r; or, (2) the rotational strength changed relatively little with r and tended to a finite value at zero r. The relevance of these observations is discussed with respect to interelation models of the complexes and with respect to possible explanations of the basis of this induction of optical activity.
    Additional Material: 10 Ill.
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  • 5
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We report progress in elucidating the structure of nisin, a naturally occurring peptide antibiotic. Nisin contains five rings constrained by lanthionine or methyllanthionine bridges, as well as α,β-unsaturated amino acids. We have determined conformations for two model compounds of ring A and a derivative of ring B through interactive nmr and computer simulation studies. High-resolution nmr techniques provides structural information, which was further refined through molecular dynamics simulations. These methods are being applied to the remaining constrained fragments of the molecule. This conformational information will be employed in an aufbau approach to determining the structure of the entire molecule.
    Additional Material: 6 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 40 (1998), S. 145-152 
    ISSN: 0021-9304
    Keywords: bioactive bone cement ; Bis-GMA resin ; AW glass-ceramic ; mechanical properties ; bioactivity ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: We examined the influence of the proportion of glass-ceramic powder in a bioactive bone cement of our formula on the bone-bonding ability of cement. Changes in cement bonding with time also were examined. The bioactive bone cement consisted of MgO-CaO-SiO2-P2O5-CaF2 glass-ceramic powder (AW-GC powder) and bisphenol-α-glycidyl methacrylate (Bis-GMA)-based resin. AW-GC powder was added to the cement as 0%, 30%, 50%, 70%, and 80% w/w. Rectangular plates (2 × 10 × 15 mm) of each cement with polished surfaces were implanted into the proximal metaphysis of the tibiae of male rabbits, and the failure load was measured by detaching tests 10 and 25 weeks after implantation. The failure loads of each cement were 0% = 0.03, 30% = 1.52, 50% = 2.67, 70% = 3.56, and 80% = 5.59 kg at 10 weeks, and 0% = 0.05, 30% = 1.68, 50% = 2.77, 70% = 3.80, and 80% = 6.37 kg at 25 weeks. Observation of the cement-bone interface revealed that all bioactive bone cements (30%-80%) formed direct contact with bone whereas intervening fibrous tissue was observed in all specimens of the 0% group. By scanning electron microscopy, all bioactive bone cements (30%-80% groups) showed direct contact with bone at the cement-bone interface. In the 0% group, direct contact with bone at the cement-bone interface was not observed. By electron-probe microanalysis, a Ca-P-rich layer was not detected at the cement-bone interfaces of the 30%-70% bioactive bone cements, but in some samples of the 80% cement specimens a thin Ca-P-rich layer (3 μm thick) was observed at the interface at 10 and 25 weeks after implantation. These results show that all of the bioactive bone cements tested had the ability to bond to bone and to function as bioactive composites of ceramics and polymers. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 145-152, 1998.
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  • 7
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 15 (1977), S. 2255-2267 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: For a nondraining polymer coil in the vicinity of the theta temperature the cube of the viscosity expansion factor αη may be expanded in powers of the excluded-volume parameter z as αη3 = 1 + C1z + C2z2 + ···. No exact values of the coefficients C1, C2, ···, are as yet known. This paper aims at evaluating C1 by the Kirkwood-Riseman formalism of polymer hydrodynamics with no mathematical approximation. The analysis gives C1 = 1.29, which is much smaller than 1.55 derived on the basis of the same formalism by Kurata and Yamakawa. The approximations used by these authors are discussed by comparison of their analysis with the present one. The first-order excluded-volume effect on the translational friction factor is also evaluated in the same way as for the intrinsic viscosity, and the result is shown to agree quite closely with the exact value determined by Stockmayer and Albrecht.
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  • 8
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 21 (1983), S. 1187-1194 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A theoretical study is made of three-phase separation in a ternary solution consisting of a pure solvent and two homologous monodisperse polymers with relative chain lengths P1 and P2. The Flory - Huggins interaction parameter X is assumed to depend linearly on the volume fraction φ of the polymer mixture: χ = χ0(T) + k(T)φ. For a given P1 the ratio of P2 to P1 for the onset of three-phase separation increases with an increase in k, first gradually and then sharply. Loci of critical points for this condition on the χ0 vs. φ diagram are determined for a series of fixed values of P1 and their significance is discussed.
    Additional Material: 3 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 17 (1979), S. 2103-2109 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Zero-shear-rate intrinsic viscosities [η]0 in benzene at 25°C and in cyclohexane at 34.5°C were measured for two series of polystyrene samples: six fractions ranging in Mw(weight-average molecular weight) from 8.8 × 106 to 5.7 × 107 and 11 “monodisperse” samples ranging in Mw from 4 × 103 to 4.8 × 106. The results, combined with typical literature data, yielded \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {[\eta ]_0 = 7.8 \times 10^{ - 5} \bar M_w^{0.75 \pm 0.01} } & {(4 \times 10^5 〈 \bar M_w 〈 6 \times 10^7 ,{\rm benzene at }25^\circ {\rm C})} \\ {[\eta ]_0 = 8.8 \times 10^{ - 4} \bar M_w^{0.50} } & {(10^3 〈 \bar M_w 〈 6 \times 10^7 ,{\rm cyclohexane at }34.5^\circ {\rm C})} \\ \end{array} $$\end{document} These relations cover the broadest range of molecular weights reported so far in the literature on synthetic polymers. In contrast to Slagowski et al., we observe no “anomaly” in the molecular weight dependence of [η]0 for benzene solutions of very high molecular weight samples (〉107).
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  • 10
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 19 (1981), S. 1405-1422 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Mixtures of two “monodisperse” samples of polystyrene (M1 = 4.53 × 104, M2 = 10.3 × 104; Mw/Mn 〈 1.01) in cyclohexane were allowed to separate into two phases at different polymer concentrations and temperatures. The compositions in the two phases were measured by gel permeation chromatography, and used to determine isothermal binodals. From the binodal data the critical temperature and concentration were estimated as functions of the composition of the polymer mixture, and the separation factor σ for each polymer component was calculated. In contrast with typical results in the literature, σ was almost independent of molecular weight of the polymer. It is shown by deriving a general expression for σ that theoretical prediction of σ requires accurate knowledge about the Flory-Huggins interaction parameter as a function of the concentrations of individual polymer components.
    Additional Material: 9 Ill.
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