摘要:

AbstractAn outline of thermodynamic and hydrodynamic properties of polyelectrolytes in solution is given. It is pointed out that proper models should be adopted to explain those properties. A polyion is often assumed to be a rigid rod having smeared charges on its surface for analyzing thermodynamic properties. The electrostatic potential distribution around rod‐like polyions, which may be calculated from the Poisson‐Boltzmann equation, can be tested by comparison with potentiometric titration data of poly(weak acids). Features of the counterion‐binding concept in analyzing thermodynamic properties are explained.It is pointed out that the radius of gyration is important for analyzing hydrodynamic properties. Features of sedimentation, diffusion, and electrophoresis are explained and compared with each other. Discussion on the expansion factor of the polyion in the presence of added salt is also given in comparison with the theories published. Finally, a characteristic polymer concentration dependence of reduced viscosity, diffusion coefficient, and osmotic pressure coefficient of polyelectrolytes in pure aqueous solutions is expl

ISSN:0360-8905    

DOI:10.1002/polc.5070490103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY

摘要:

AbstractApplying nonequilibrium thermodynamics, a theory of nonisothermal membrane phenomena through charged membranes is described. Agreement between theory and observed thermal membrane potential is satisfactory. In thermo‐osmosis, the effective temperature difference across the membrane is determined by measuring the thermal membrane potential. A qualitative explanation based on nonequilibrium thermodynamics is presented for the experimental result

ISSN:0360-8905    

DOI:10.1002/polc.5070490104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY

摘要:

AbstractAn attempt is made to outline the role of nuclear magnetic resonance (NMR) in the study of the hydration of proteins. NMR techniques are very effective in these studies because of the sensitivity of the magnetic resonance of isotopes of the water molecule (usually1H,2H, and17O) to the changes in the molecular state and environment that are brought about by the water‐protein interaction. The NMR techniques which are effective in characterizing specific properties of the hydration water such as mobility, anisotropy, and heterogeneity are discussed. Methods of interpreting the data so obtained in terms of these molecular properties as applied to particular protein‐water systems are outli

ISSN:0360-8905    

DOI:10.1002/polc.5070490105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY

摘要:

AbstractThe paramagnetic ion Gd3+binds to the α‐carboxyl group of a peptide and broadens the resonances from the13C and1H nuclei of the backbone sequentially along the chain. The sequential broadening of both carbonyl and Cαnuclei of PheAspAlaSerVal have been observed in 6 M guanidine hydrochloride at pH 4.0. Sequential broadening from the N‐terminus is also possible using Cu2+at pH ≥ 8.Broadening experiments using triglycine and either Gd3+or Cu2+show that it is more difficult to broaden13C than1H resonances on the same amino acid residue. The ratio of [Gd3+]CMR/[Gd3+]PMR is 12 ± 5, which agrees reasonably well with the theoretical value of 16. The ratio [Cu2+]CMR/[Cu2+]PMR is 3 ± 2.The relative advantages of proton magnetic resonance (PMR) and carbon‐13 magnetic resonance (CMR) spectroscopy for this application are discussed. It is concluded that sequence determinations of 20 mg samples of peptides, ranging in size up to 7–9 residues, should be possible using CMR spectroscopy. The main advantage of PMR spectroscopy is the much smaller amounts of material required, but other problems preclude its use at this time except for very si

ISSN:0360-8905    

DOI:10.1002/polc.5070490106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY

摘要:

AbstractThe random coil dimensions of polysarcosine and poly‐α‐aminoisobutyric acid have been evaluated using both theoretical and experimental methods. Theoretical values for characteristic ratios were derived from the (ϕ, Ψ) potential energy maps for the cis and trans isomers of Nα‐acetylsarcosine N,N‐dimethylamide and for Nα‐acetyl‐α‐aminoisobutyryl N‐methylamide. Experimental values were derived from viscosity data in various solvents. For polysarcosine in glacial acetic acid, the experimentally derived characteristic ratio agreed with the theoretically derived value for the trans isomer. From the lower ratios observed using water and particularly chloroform, these solvents are presumed to admit the cis isomer. Theoretical calculations (derived from energy maps) of poly‐α‐aminoisobutyric acid gave an unusually low characteristic ratio (<1) which was not in agreement with that from viscosity measurements in heptafluorobutyric acid. Reasons for the discrepancy are discussed in terms of the ease of propagation of helical region

ISSN:0360-8905    

DOI:10.1002/polc.5070490107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY

摘要:

AbstractBueche's theory of the mechanical degradation of polymers in shear is applied to try to account for the changes in flour proteins following high‐speed mixing of doughs. Because of the high viscosity of dough (∼ 108poise), shear strain rates on the order of 102sec−1, which are encountered in standard dough mixers, are sufficient to cause scission of covalent bonds. The limiting amount of protein, extractable after mixing, increased with mixing speed, in agreement with the predicted effect of strain rate on breakdown. Agents which crosslinked protein chains through strong covalent bonds increased the mixing stability of doughs, while those which crosslinked by formation of SS bonds greatly accelerated breakdown, reflecting the more labile nature of the SS bond. Some predictions about the rheclogical effectiveness of different SS bonds follow from the theory. Predicted changes in molecular weight distribution of protein following mixing are in agreement with experimental results obtained by ot

ISSN:0360-8905    

DOI:10.1002/polc.5070490108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY

摘要:

AbstractWater soluble polysaccharides are used broadly and in large amounts by food and nonfood industries. These polymers are plant exodates, seaweed extracts, plant extracts, seed endosperms, modified starches and cellulose, and biosynthetics. They may be neutral or anionic through their content of carboxyl or sulfate half‐ester groups. They may be linear or branched but their usefulness depends upon their causing large rheological or other physical effects at low concentrations. They are used mainly to improve viscosity, suspension stability, emulsification, flocculation or emolliency. Their use is increasing each year and the trend is toward use of agricultural or biosynthetic gums or starch and cellulose derivative

ISSN:0360-8905    

DOI:10.1002/polc.5070490109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY

摘要:

AbstractGel chromatography studies of a series of gelatins and dextrans on Sepharose 4B substrates are described. The intrinsic viscosities and weight average molecular weights of the gelatin samples are also measured. A plot of mean partition coefficients versus log (M>W[η]) is found to be linear for the dextrans, but not for the gelatins, in 0.1 M urea. In 0.1 M urea/0.1 M NaCl solution, the gelatins behaved more reproducibly.The molecular weight distributions of the various gelatins, as delineated by the gel chromatography data, are considered in relation to manufacturing processes and physical properties

ISSN:0360-8905    

DOI:10.1002/polc.5070490110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY

摘要:

AbstractNovel methods have been developed for the preparation of polymers suitable for the attachment of enzymes, or other biochemical macromolecules, to render them water insoluble. By a new irradiation process, p‐nitrostyrene has been graft copolymerized to trunk polymers, such as polypropylene. Reduction of the nitro group in the graft copolymer gives the amino derivative, which may be converted to other functional groups (isothiocyanato or diazo) or used in conjunction with bifunctional reagents in order to covalently bind enzymes to produce active, water‐insoluble conjugates. The properties of one such conjugate, in which trypsin was immobilized by covalent attachment to poly(p‐isothiocyanatostyrene‐g‐propylene) are discussed. The advantages of the present radiation grafting technique are compared with conventional methods for insolubilizin

ISSN:0360-8905    

DOI:10.1002/polc.5070490111

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY

摘要:

AbstractThe literature on gel permeation chromatography (GPC) is surveyed and briefly reviewed to provide a guide to some of the more important references, particularly those dealing with equipment and polymer molecular weight determination. A number of applications of GPC in the authors' laboratories are discussed in order to illustrate use of the GPC technique, with particular regard to its value in estimating low molecular weight substances present in polymers.

ISSN:0360-8905    

DOI:10.1002/polc.5070490112

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY