Tsaih M L, Chen R H
Department of Marine Food Science, National Taiwan Ocean University, Keelung, ROC.
Int J Biol Macromol. 1997 Jun;20(3):233-40. doi: 10.1016/s0141-8130(97)01165-3.
The effects of molecular weight and urea on the magnitude of the Mark-Houwink exponent a and the relative stiffness parameter B of chitosan molecules in dilute solutions were analyzed. The results show that in solutions with ionic strengths between 0.01 and 0.3 M, the relative chain stiffness parameter B and the Mark-Houwink exponent a of chitosans whose molecular weights were between 22.3 x 10(4) and 91.4 x 10(4) fell between 0.143 and 0.152 and from 0.404 to 0.497, respectively; whereas for chitosans whose molecular weights were between 7.8 x 10(4) and 14.8 x 10(4) these values fell between 0.110 and 0.138 and from 0.653 to 1.009, respectively. Both results indicate that the stiffness and conformations of small molecular weight chitosans were more stiff and extended, respectively, than higher molecular weight ones, and that molecular weight-induced conformational transition occurred. Chitosans in solutions containing 4 M urea possessed a rod-shaped conformation in both molecular weight domains, and no molecular weight-induced conformational transitions occurred.
分析了分子量和尿素对稀溶液中壳聚糖分子的马克-豪温克指数a的大小以及相对刚度参数B的影响。结果表明，在离子强度为0.01至0.3 M的溶液中，分子量在22.3×10⁴至91.4×10⁴之间的壳聚糖的相对链刚度参数B和马克-豪温克指数a分别在0.143至0.152之间以及从0.404至0.497之间；而对于分子量在7.8×10⁴至14.8×10⁴之间的壳聚糖，这些值分别在0.110至0.138之间以及从0.653至1.009之间。这两个结果均表明，小分子壳聚糖的刚度和构象分别比大分子壳聚糖更硬且更伸展，并且发生了分子量诱导的构象转变。在含有4 M尿素的溶液中的壳聚糖在两个分子量范围内均具有棒状构象，并且未发生分子量诱导的构象转变。
