Nakata Yasushi, Amitani Keiji, Norisuye Takashi, Kitamura Shinichi
Department of Macromolecular Science, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan.
Biopolymers. 2003 Aug;69(4):508-16. doi: 10.1002/bip.10393.
Seven cyclic (1 --> 4)-alpha-D-glucan (cycloamylose) samples ranging in weight-average molecular weight from 5 x 10(3) to 1.8 x 10(4) and gamma-cyclodextrin have been studied by sedimentation equilibrium in dimethylsulfoxide (at 25 degrees C) and by dynamic light scattering in 0.5 N aqueous sodium hydroxide (at 25 degrees C), a good solvent for linear amylose. The measured translational diffusion coefficients D in the aqueous NaOH agree fairly closely with previous Monte Carlo results for cyclic (1 --> 4)-alpha-D-glucan chains with excluded volume, when correction is made for the effects of bead diameter and fluctuating hydrodynamic interaction (HI) on the Kirkwood theory on which the computation of D was based. These D data are also explained almost quantitatively by Yamakawa and Fujii's expression for the associated KP ring (based on the Kratky-Porod wormlike chain) with the molecular parameters for linear amylose if the fluctuating HI and excluded-volume effects are taken into account. It is concluded that the translational diffusion behavior of cycloamylose in the aqueous NaOH is consistent with the conformational characteristics derived from the conformational energy of maltose and dilute-solution data for linear amylose.
通过在二甲基亚砜中（25℃）的沉降平衡以及在0.5N氢氧化钠水溶液中（25℃）的动态光散射，对七种重均分子量在5×10³至1.8×10⁴之间的环状（1→4）-α-D-葡聚糖（环糊精）样品以及γ-环糊精进行了研究，0.5N氢氧化钠水溶液是直链淀粉的良溶剂。当对珠子直径和波动的流体动力学相互作用（HI）对计算扩散系数D所基于的柯克伍德理论的影响进行校正后，在氢氧化钠水溶液中测得的平动扩散系数D与先前关于具有排除体积的环状（1→4）-α-D-葡聚糖链的蒙特卡罗结果相当吻合。如果考虑波动的HI和排除体积效应，这些D数据也几乎可以通过山川和藤井关于相关KP环（基于克拉特基-波罗德蠕虫状链）并结合直链淀粉分子参数的表达式进行定量解释。得出的结论是，环糊精在氢氧化钠水溶液中的平动扩散行为与从麦芽糖的构象能量和直链淀粉稀溶液数据得出构象特征一致。
