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Solution properties of synthetic polypeptides. II. Sedimentation and viscosity of poly‐γ‐benzyl‐ L ‐glutamate in dimethylformamide
Author(s) -
Fujita Hiroshi,
Teramoto Akio,
Yamashita Tsuneko,
Okita Koichi,
Ikeda Shoichi
Publication year - 1966
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.1966.360040708
Subject(s) - chemistry , sedimentation coefficient , prolate spheroid , monomer , intrinsic viscosity , macromolecule , limiting , viscosity , solvent , molecule , dimethylformamide , intramolecular force , crystallography , stereochemistry , analytical chemistry (journal) , thermodynamics , polymer , chromatography , organic chemistry , physics , mechanical engineering , biochemistry , classical mechanics , engineering , enzyme
Nine samples of poly‐γ‐benzyl‐ L ‐glutamate (PBLG), ranging in M̄ w from 19,000 to 410,000, were examined viscomctrically and by ultracentrifugation with dimethylforma‐mide (DMF) at 25°C. as helicogenic solvent. The data for [η] and s 0 (limiting sedimentation coefficient) as functions of M̄ w were fitted well by the theories for a rigid prolate ellipsoid of revolution whose major axis increases linearly with M̄ w , but whose minor axis is independent of M̄ w . 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 [η] is about 1.3 A., whereas that from s 0 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 α‐helix, for which h is 1.5 A. The concentration dependence of s 0 was found to agree well with the recent theoretical prediction of Peterson for cylindrical macromolecules.