화학공학소재연구정보센터
Macromolecules, Vol.45, No.6, 2882-2890, 2012
Chondroitin Sulfate in Solution: Effects of Mono- and Divalent Salts
Chondroitin sulfate (CS) is a linear sulfated polysaccharide found in cartilage and other tissues in the body. Small-angle neutron scattering (SANS) and dynamic light scattering (DLS) measurements are made on semidilute CS solutions to determine ion-induced changes in the local order of the CS chains and in their dynamic properties. In salt-free CS solutions SANS detects the correlation peak due to local ordering between adjacent chains in which the characteristic interchain distance is d approximate to 57 angstrom. In both monovalent and divalent salts (NaCl and CaCl2) aligned linear regions are distinguishable, corresponding to distance scales ranging from the length of the monomer unit (8 angstrom) to about 1000 angstrom. With increasing calcium ion concentration, the scattering intensity increases. Even in the presence of 200 mM CaCl2, however, neither phase separation nor cross-linking occurs. DLS in the CS solutions reveals two characteristic relaxation modes, the fast mode corresponding to the thermal concentration fluctuations. The collective diffusion coefficient D decreases with increasing calcium ion concentration and exhibits a power law function of the single variable c/J, where c is the CS concentration and J is the ionic strength of the salt in the solution. This result implies that the effect of the sodium and calcium ions on the dynamic properties of CS solutions is fully accounted for by the ionic strength.