Abstract
AbstractThe number average molecular weight, Mn, of low molecular weight dextran was determined through endgroup analysis, and the intrinsic, viscosities of these materials in aqueous solution were determined at 25°C. The ultrasonic velocities in their aqueous solutions were also measured at 25 and 45°C. As concerns the molecular weight dependence of the intrinsic viscosity, partial specific compressibility of solute and the hound water around the solute, the following results were obtained. (1) log [η]‐log Mn and [η]/Mn0.5 – Mn0.5 plots were in accord with the Mark‐Houwink and Stockmayer‐Fix‐man equations respectively for Mn > 2, 000, but these plots deviated from the equations for Mn < 2, 000. (2)The partial specific compressibility, β1°, of dextran is expressed by following equation for Mn < 2,000: β1° = 10−12 × (13.6 log Mn ‐ 51.7) (cm2/dyne). In contrast, it, becomes the constant value, ‐‐ 7.3 × 10−12 cm2/dyne, for Mn > 2,000. (3) The amount of bound water of dextran calculated from the sound velocity measurement lakes constant value of 0.17 ml g for Mn > 2, 000, but the amount of hydration increase with decreasing molecular weight for Mn < 2,000. From these results, a dextran molecule in aqueous solution is expected to change its conformation from random coiling to uncoiling stretched form at the molecular weight of around 2, 000 or about 12 glucose units.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call