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Solution properties of synthetic polypeptides. II. Sedimentation and viscosity of poly-γ-benzyl-L-glutamate in dimethylformamide

✍ Scribed by Hiroshi Fujita; Akio Teramoto; Tsuneko Yamashita; Koichi Okita; Shoichi Ikeda

Publisher
Wiley (John Wiley & Sons)
Year
1966
Tongue
English
Weight
538 KB
Volume
4
Category
Article
ISSN
0006-3525

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✦ Synopsis

Nine samples of poly-ybeneyl-kglutamate (PBLG), ranging in aw from 19,000 to 410,000, were examined viscometrically and by ultracentrifugation with dimethylformamide (DMF) at 25°C. as helicogenic solvent. The data for [v] and SO (limiting sedimentation coefficient) as functions of am were fitted well by the theories for a rigid prolate ellipsoid of revolution whose major axis increases linearly with aw but whose minor axis is independent of a,.,. This implies that the overall shape of the PBLG molecule in DMF is represented by a straight cylinder whose cross section is independent of its length. The length per monomeric residue h evaluated from [v] is about 1.3 A., whereas that from so is about 1.6 A. No adequate explanation for this difference in h can be found at present. More serious is the fact that these hydrodynamically evaluated values of h are appreciably larger than the value obtained from our light-scattering measurements reported previously. All these values of h from our studies are not consistent with the value characteristic of the a-helix, for which h is 1.5 A. The concentration dependence of so was found to agree well with the recent theoretical prediction of Peterson for cylindrical macromolecules.

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