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Small‐angle X‐ray scattering study on conformation of poly(sodium l ‐glutamate) in NaCl and NaF aqueous solutions
Author(s) -
Shimizu Shigeru,
Muroga Yoshio,
Hyono Tatsuya,
Kurita Kimio
Publication year - 2007
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s0021889807006255
Subject(s) - small angle x ray scattering , aqueous solution , chemistry , random coil , crystallography , circular dichroism , titration , potentiometric titration , carboxylate , scattering , stereochemistry , inorganic chemistry , physics , optics , electrode
The effect of anions F − and Cl − on the conformation of poly(sodium l ‐glutamate) (PNaGA) in added‐salt aqueous solution was studied using potentiometric titration, high‐resolution proton nuclear magnetic resonance (NMR), circular dichroism (CD) and small‐angle X‐ray scattering (SAXS) techniques. In the titration curve for PNaGA in NaCl aqueous solution, four conformation regions, i.e. aggregation‐, helical‐, helix‐to‐coil transition‐ and random‐coiled, were clearly observed but these regions were gradually obscured when the concentration of F − was increased. Both CD and NMR spectra have clarified that the local conformation of PNaGA in NaF aqueous solution is a random‐coiled state, independent of the degree of neutralization (DN). SAXS studies show that the conformation of a larger dimension for PNaGA having DN = 0.25 in 0.2 NaF aqueous solution is roughly mimicked by a worm‐like chain having persistence length of ca 5.9 Å, but the conformation at DN = 0.80 is far from an isolated worm‐like chain.