Stability of Dextran Solutions

In order to clarify the accessibility of dextran to both water and dextran the onset of turbidity in dextran solution was studied by means of viscosimetry and near-infrared and PMR measurements. Mole fraction of monomeric and hydrogen-bonded water species in dextran solutions were calculated for various concentrations of dextran solutions from 2ν1+ν3 and ν1+ν2+ν3 bands where ν1, ν2, and ν3 are the fundamental vibrations of symmetric stretching, bending and asymmetric stretching, respectively. The extent of hydrogen bonds was estimated from PMR chemical shift of water proton. A dextran solution was characterized by a low concentration in monomeric water. An anomalous time dependence of viscosity and PMR chemical shift was observed for concentrated solutions. A mechanism has been proposed for gelation and the onset of turbidity, stress being laid on comparable accessibility of dextran to both water and dextran.