Electrostatic contributions to chain stiffness and excluded-volume effects in sodium hyaluronate solutions

Intrinsic viscosities [eta] for sodium hyaluronate in aqueous sodium chloride at 25 degrees C were determined for 12 samples ranging in weight-average molecular weight M(w) from 3.8 x 10(3) to 3.5 x 10(3) at NaCl concentrations C-s between 0.005 and 2.5 M. They were analyzed on the basis of the Yamakawa Fujii Yoshizaki theory for [eta] of an unperturbed wormlike chain combined with the Yamakawa Stockmayer Shimada theory for excluded volume effects to estimate the total persistence length q and the excluded-volume strength B as functions of C-s. At any C-s studied, excluded-volume effects on [eta] became appreciable when M(w) exceeded 1 x 10(4)-2 x 10(4). The C-s dependance of q yielded 4.0 nm for q(0) (the intrinsic persistence length) of the polysaccharide chain at infinite ionic strength. It was found that the values of q-q(0) (i.e., the electrostatic contribution to q) at C-s < 0.02 M were roughly 70% larger than predicted by the Le Bret theory and the Odijk-Skolnick-Fixman theory. On the other hand, the estimated B values agreed fairly well with Fixman and Skolnick's theory for the excluded-volume interaction between a pair of charged rodlike segments unless C-s was lower than 0.05 M.