ISSN:
0006-3525
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Light-scattering measurements were performed for a number of poly-γ-benzyl-L-glutamate (PBLG) samples in dimethylformamide (DMF) and in chloroform-formamide (C-F) at 25°C. Osmotic pressure data for some of these polypeptide samples in DMF at 37°C. were also determined. The scattering radii 〈S2〉1/2 in the two solvents were roughly proportional to the sample's weight-average molecular weight Mw. The lengths per monomeric residue h, calculated from the measured 〈S2〉1/2 and Mw with the assumption of a rigid rod of uniform density, were about 1.2 A. in DMF and about 1.5 A. in C-F. The measured values for the Mw/Mn ratio indicated that the samples used were quite polydisperse in molecular weight. If this effect is taken into account, the above values for h must be lowered drastically. In fact, application of Holtzer's procedure, which is capable of yielding h free of polydispersity effects, gave 0.85 A. for h in DMF and 1.16 A. for h in C-F. Since, according to the recent conclusion established by Parry and Elliott, the correct conformation of the PBLG molecule in helicogenic solvents must be the α-helix for which h is 1.5 A., these results imply that the overall shape of the PBLG helix cannot be a rigid rod, in contradiction to the earlier conclusion of Doty et al.
Additional Material:
5 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/bip.1966.360040707
Permalink