摘要:

AbstractIntensities and other spectral parameters of infrared amide I and II bands of α‐helical polypeptides in solutions have been determined for poly(γ‐benzylglutamate), poly(γ‐ethylglutamate), and polymethionine in chloroform, polylysine, poly(glutamic acid), and fibrillar protein tropomyosin from rabbit muscles in heavy water. The majority of spectral parameters are characteristic. The half‐width of the amide I band was found to vary in the range of 15–40 cm−1for different polypeptides in the different solutions. The correlation between this parameter of the amide I band and the stability of the α‐helix was estimated. A new weak band near 1537 cm−1of unknown origin was observed for the hydrogen form of polypeptides in

ISSN:0006-3525    

DOI:10.1002/bip.1974.360130902

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

年代:1974

数据来源: WILEY

摘要:

AbstractTheDandLcopolymerizations of γ‐benzyl glutamate N‐carboxylic anhydride (NCA) were carried out by two different initiators,n‐butylamine and sodium methoxide. The stereoregularity of the polymer was examined by infrared spectroscopy in the region 700–200 cm−1. A remarkable difference was found between the polymers obtained by these initiators in the region 450–400 cm−1. In the polymer obtained with sodium methoxide as initiator, the 409‐cm−1peak assigned to local α‐helical conformation was not greatly affected by the amount of theL‐form, but in the polymer obtained byn‐butylamine this peak was much affected by the variation ofL‐content. This indicates that the stereo‐selectivity of the polymerization in the sodium methoxide initiated system is higher than that in the

ISSN:0006-3525    

DOI:10.1002/bip.1974.360130903

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

年代:1974

数据来源: WILEY

摘要:

AbstractThe intrinsic viscosity and molecular weight of several samples of polyhydroxyethylaspartamide with differing degrees of polymerization were determined and related, according to the Mark‐Howink equation. Theaexponent is consistent with a random‐coil structure. The average unperturbed dimensions of the polymer, the dimensions in water, and the water–polymer interaction parameter were calculated according to Flory and Fox. The interaction of the polymer with water may explain its good efficacy as a plasma expander, as has previously been demonstrated in biological experiments. The behavior of the molecule in 6Mguanidine hydrochloride solution was also studied: this solvent has a very slight effect on the configuration of the polymer, in contrast with its normal effect on pro

ISSN:0006-3525    

DOI:10.1002/bip.1974.360130904

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

年代:1974

数据来源: WILEY

摘要:

AbstractTheoretical values are reported for the specific conductivity, charge carrier mobilities, and delocalized free paths in β‐polyglycine using the parallel‐chain pleated sheet conformation and the all‐valence electron energy band structure obtained previously. The mobilities are found to be much larger along the polypeptide backbones than in the direction of the hydrogen bonds. This indicates a mechanism of conduction in which the former path is favored for electronic delocalization. The preexponential factor of the specific conductivity obtained theoretically agrees well with experimental r

ISSN:0006-3525    

DOI:10.1002/bip.1974.360130905

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

年代:1974

数据来源: WILEY

摘要:

AbstractThe results of a CNDO/2 all‐valence electron crystal orbital study are reported for the sugar‐phosphate chain of DNA. The valence and conduction bandwidths are found to be large enough to make electronic delocalization through this backbone possible. Different mechanisms for charge carrier transport in DNA are compared on the basis of the electron and hole effective masses. Conduction along the backbone seems to be at least as probable as through the aperiodic system of the superimposed nucleotide ba

ISSN:0006-3525    

DOI:10.1002/bip.1974.360130906

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

年代:1974

数据来源: WILEY

摘要:

AbstractThe circular dichroism of a series ofL‐methionine oligopeptides [BOC‐(Met)n‐OMe] was examined in trifluoroethanol and hexafluoroacetone sesquihydrate. The results indicate that the trimer through the hexamer exists predominantly in disordered conformations in these solvents. An abrupt change in the CD pattern at the heptamer in trifluoroethanol suggests thatL‐methionine oligopeptides begin forming helices at this chain

ISSN:0006-3525    

DOI:10.1002/bip.1974.360130907

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

年代:1974

数据来源: WILEY

摘要:

AbstractMicrocalorimetric heat capacity measurements on dilute and concentrated solutions and films of poly[d(A‐T)·d(A‐T)] in 2Msodium chloride have been carried out. Values for enthalpy, entropy, and temperature of the helix–coil transition have been found to depend on the polymer concentration, and to have maxima near 20% (w/w) of polymer. The results are discussed in terms of polynucleotide hydration as one of the structure stabilizing f

ISSN:0006-3525    

DOI:10.1002/bip.1974.360130908

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

年代:1974

数据来源: WILEY

摘要:

AbstractThe circular dichroism spectra of complexes of the antibiotics daunomycin, nogalamycin, chromomycin, and mithramycin with calf thymus DNA have been measured over a range of drug/DNA ratios. The similarity of the CD spectra of bound chromomycin and mithramycin suggests that they have very similar binding sites, which produce strong effects on the CD spectra of the bound drugs, and remove the differences arising from local stereochemistry in the free drugs. It was found that it was not possible to predict whether the antibiotics intercalated, from studies of the CD spectra alone, even when comparisons were made with the CD spectra of aminoacridine–DNA complexes with intercalating or nonintercalating ligand

ISSN:0006-3525    

DOI:10.1002/bip.1974.360130909

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

年代:1974

数据来源: WILEY

摘要:

AbstractThe spin‐lattice relaxation time (T1) of water adsorbed on collagen fibers was determined at six frequencies and temperatures varying from 25° to −80°C. Care was taken to eliminate the contributions to the signal of protons other than those in the adsorbed water. Quantitative calculations were made onT1and the results were compared with the experimental data. It is suggested that a maximum of about 0.50–0.55 g water per g collagen forms a hydration layer, which cannot be frozen down to −90°C and exhibits a distribution of motional correlation times. For collagen samples containing a larger quantity of adsorbed water, the additional water molecules behave like ordinary isotropic water, having a single correlation time and a freezing temperature of a

ISSN:0006-3525    

DOI:10.1002/bip.1974.360130910

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

年代:1974

数据来源: WILEY

摘要:

AbstractRecent advances in dielectric theory are applied to two models representing an aqueous solution of dipolar macromolecules. In one model the water is treated as a dielectric continuum and the macromolecule as a finite‐sized sphere; in the other both components are represented as point dipoles suspended in a background dielectric. The predicted frequency dependences of the complex permittivity in these two cases agree and the validity of the dielectric technique for estimating macromolecular size and shape is established. The model in which water is treated as a dielectric continuum predicts a larger dielectric dispersion in the radio frequency region, which is consistent with the experimental data available for myoglobin. The validity of the Debye formula for relaxation time and the effect of “dielectric friction” in macromolecular solutions are also disc

ISSN:0006-3525    

DOI:10.1002/bip.1974.360130911

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

年代:1974

数据来源: WILEY