Clark D S, Mattice W L
Macromolecules. 1977 Mar-Apr;10(2):369-74. doi: 10.1021/ma60056a028.
Intrinsic viscosities and sedimentation coefficients have been measured as a function of molecular weight for poly(gamma-hydroxy-L-proline) in water. The molecular weight range covered is 9,000-35,000. High molecular weight poly(gamma-hydroxy-L-proline) in water has the hydrodynamic behavior of a random coil immersed in a good solvent, as judged by d ln [eta]/d ln M, d ln so/d ln M, dbeta/dM, and the size of beta[= nu rho (-1)]/1/3etaM-2/3(1 - nurho)-1]. The characteristic ratio, ((r2)o/nplp2) infinity, is found to be 15.9 +/- 1.6, which is not significantly different from the result of 13.7 +/- 0.9 obtained for poly(L-proline) by Mattice and Mandelkern under the same conditions. This observation casts doubt on the importance of intrachain hydrogen bonded bridges from the hydroxyl group to a carbonyl oxygen via a water molecule. The characteristic ratios and the effects of calcium chloride on the hydroynamic properties suggest that poly(L-proline) and poly(gamma-hydroxy-L-proline) possess a similar source of flexibility which is often overlooked. Two possibilities for this flexibility are a second energy minimum about the Calpha-C' bond and cis-trans isomerization about the peptide bond.
已测定了聚（γ-羟基-L-脯氨酸）在水中的特性粘度和沉降系数与分子量的函数关系。所涵盖的分子量范围为9000 - 35000。从d ln[η]/d ln M、d ln s₀/d ln M、dβ/dM以及β[= νρ(-1)]¹/³ηM⁻²/³(1 - νρ)⁻¹]的大小判断，水中高分子量的聚（γ-羟基-L-脯氨酸）具有随机线团沉浸在良溶剂中的流体力学行为。发现特征比((r²)₀/npₗp²)∞为15.9 ± 1.6，这与马蒂斯和曼德尔克恩在相同条件下对聚（L-脯氨酸）得到的13.7 ± 0.9的结果没有显著差异。这一观察结果对通过水分子从羟基到羰基氧的链内氢键桥的重要性提出了质疑。特征比以及氯化钙对流体力学性质的影响表明，聚（L-脯氨酸）和聚（γ-羟基-L-脯氨酸）具有相似的柔性来源，而这一点常常被忽视。这种柔性的两种可能性是围绕Cα-C'键的第二个能量最小值以及围绕肽键的顺反异构化。
