Study on Interactions between Plasma Proteins and Polymer SurfaceSato, Hiroko; Morimoto, Hiroyuki; Nakajima, Akio; Noishiki, Yasuharu
doi: 10.1295/polymj.16.1pmid: N/A
Plasma proteins at high concentrations were found to be adsorbed on a synthetic material surface as a multimolecular layer. However, at low concentrations, albumin, globulin, and fibrinogen molecules were adsorbed on the material surface as a Langmuir-type monomolecular layer. The adsorption rate constants of plasma proteins were evaluated for segmented polyether urethane nylon, poly(vinyl alcohol), materials containing relatively hydrophobic groups, and glass. The initial stage at which plasma starts to come into contact with these materials was taken into consideration. The good antithrombogenecity of segmented polyether urethane nylon was concluded to be due to its selective adsorption of albumin.
β-Turn-Like Conformation and Side Chain Interactions of Aspartic Acid-Containing DipeptidesIshii, Hiroshi; Inoue, Yoshio; Chûjô, Riichirô
doi: 10.1295/polymj.16.9pmid: N/A
Conformation of Asp-containing dipeptides of the general formulae: Ac–Asp–X–NHMe and A–c–X–Asp–NHMe (X = Ser, Lys, Asp, and Tyr) in solution were investigated using 1H and 13C NMR spectroscopy. The dominant formation of a β-turn-like structure was confirmed in the dipeptides, Ac–Ser–Asp–NHMe and Ac–Lys–Asp–NHMe with the deprotonated Asp side chain, from the dependence of the amide proton chemical shifts on temperature, solvent composition, and peptide concentration, and from the backbone dihedral angle φ. The backbone conformations of these dipeptides changed with the deprotonation of Asp. In addition to the intramolecular hydrogen bond of the 4–1 type constituting β-turn structure, other kinds of intramolecular interaction between the carboxylate groups of Asp and side chains of neighboring residues were found in Ac–Ser–Asp–NHMe, Ac–Asp–Ser–NHMe, Ac–Lys–Asp–NHMe by analysis of the side chain rotamer populations, spin-lattice relaxation times, and pK
a values. These side chain interactions may possibly contribute to the stabilization of the β-turn-like structure.
Morphorogical and Structural Studies on Large Spherulites of Poly(p-phenylene terephthalamide)Xu, Duanfu; Okuyama, Kenji; Kumamaru, Fumiko; Takayanagi, Motowo
doi: 10.1295/polymj.16.31pmid: N/A
The poly(p-phenylene terephthalamide) (PPTA) spherulite grown from a concentrated sulfuric acid solution and its hydrolysis products were investigated by electron microscopy and X-ray diffraction. Sharp Bragg reflections and their spacings indicated that the nascent spherulite consists of complex crystals of PPTA and sulfuric acid. All the diffraction spots from the hydrolysis products of PPTA/H2SO4 spherulites could be associated with the Form II crystal with one exception on the equator. This exceptional spot had a fairy strong intensity in the diffraction patterns from air-dried spherulites and was assigned to the (100) reflection. On the other hand, the intensity of this reflection could not be expected from the packing arrangement of the Form II crystal. To explain the intensity of (100), the Form II crystal structure was modified and water was introduced into the unit cell. The structure found showed good agreement between observed and calculated structure amplitudes. Further, the calculated amount of bound water was almost the same as that lost by annealing above 400 K.
Structure and Piezoelectricity of Poly(vinylidene fluoride) Films Obtained by Solid-State ExtrusionTasaka, Shigeru; Niki, Jun; Ojio, Takeaki; Miyata, Seizo
doi: 10.1295/polymj.16.41pmid: N/A
Solid-state extrusion of poly(vinylidene fluoride) and its coextrusion with polyethylene were carried out using a slit die (die angle=35°) at 400 MPa. Extrudates with smooth surfaces were obtained at extrusion ratios from 2.0 to 6.5. Wide-angle X-ray diffractions of the extrudates showed double orientation characteristic of the form I crystals, with the c-axis preferentially oriented in the machine direction and the b-axis parallel to the film surface. The piezoelectric constant d
31 of the extrudates increased with increasing extrusion ratio, but decreased with increasing extrusion temperature. Thus, the piezoelectric activity may be explained by changes in Poisson’s ratio and Young’s modulus, perfection of crystallites, and selective orientation.
Optical Rotatory Dispersion of Liquid Crystal Solutions of a Triple-Helical Polysaccharide SchizophyllanVan, Kazuo; Asakawa, Toshiaki; Teramoto, Akio
doi: 10.1295/polymj.16.61pmid: N/A
When confined in a thin parallel cell, a liquid crystal solution of a polysaccharide schizophyllan formed a planar texture and showed very strong optical rotatory power. The wavelength dependence of the optical rotatory power was represented by a simple equation of the Drude type and differed from that of an isotropic solution which obeyed a Moffitt-Yang type equation. The data at longer wavelengths were consistent with the prediction by the de Vries theory of cholesterics, yielding a layer birefringence approximately proportional to the polymer concentration. The intrinsic birefringence of a schizophyllan triple helix was estimated to be about 0.02, which is much smaller than that of xanthan and the birefringence of crystalline cellulose. The difference in birefringence was ascribed to the difference in chain conformation among these glucans. An abrupt change in ORD behavior occurred when an isotropic solution was cooled down to a temperature close to the isotropic-biphasic boundary temperature, indicating the occurrence of a pretransition from isotropic to cholesteric phases.