Effect of substitution degree on carboxymethylcellulose interaction with lysozyme

Substitution degree (DS) of carboxymethylcellulose (CMC) is one of the critical internal factors for affecting CMC interacting with other polyelectrolytes. The assembly of lysozyme (Ly) and CMC with various DS were analyzed with turbidities, zeta potentials, intrinsic fluorescence, Fourier transform infrared spectra and circular dichroism. It was found that the electrostatic interactions were weakened with decreasing the ratio for Ly and CMC in the Ly-CMC complexes because of the increasing electrostatic repulsion of CMC itself. Electrostatic attractions were also reduced at neutral or alkaline pH and high salt concentration. In addition, electrostatic attractions were much stronger between Ly and CMC with higher DS. CMC with higher DS value can resist the decomposition of Ly-CMC more effectively. Our work provides a new insight for understanding the interactions between proteins and polysaccharides. (C) 2016 Elsevier Ltd. All rights reserved.