Mattice W L
Macromolecules. 1977 May-Jun;10(3):511-6. doi: 10.1021/ma60057a002.
Rotational isomeric state theory, in the form appropriate for branched molecules, has been used to calculate the mean-square unperturbed radius of gyration, (s2)0, for cross-linked polyglycine, poly(L-alanine), poly(L-proline), poly(L-alanyl-D-alanine), poly(L-propyl-L-prolylglycine), poly(L-prolyl-L-alanylglycine, poly(glycyl-L-alanyl-L-proline), and poly(L-alanyl-L-alanylglycine). The central amino acid residue in each polypeptide chain is replaced by the L-cysteinyl residue involved in cross-link formation. Each cross-linked molecular is considered to contain two trifunctional branch points, the alpha-carbon atoms of the two L-cysteinyl residues. Random flight statistics provide a poor estimate for g, defined as the ratio of (s2)0 for branched and linear polypeptides containing the same number of amino acid residues, for molecules of moderate molecular weight. The values of g obtained by random flight statistics and rotational isomeric state theory merge as the molecular weight becomes infinite. Deviations of g from its random flight value correlate with the size of the characteristic ratio, (s2)0/nplp2, for the linear polypeptides. The number of peptide bonds is np, and lp denotes the distance between neighboring alpha carbon atoms. Random flight statistics perform better in estimating the change in (s2)0 accompanying the cross-linking of the two polypeptide chains than it does in the estimation of g.
已采用适用于支链分子形式的旋转异构体状态理论，来计算交联聚甘氨酸、聚（L - 丙氨酸）、聚（L - 脯氨酸）、聚（L - 丙氨酰 - D - 丙氨酸）、聚（L - 丙基 - L - 脯氨酰甘氨酸）、聚（L - 脯氨酰 - L - 丙氨酰甘氨酸）、聚（甘氨酰 - L - 丙氨酰 - L - 脯氨酸）和聚（L - 丙氨酰 - L - 丙氨酰甘氨酸）的均方无扰回转半径((s^2)_0)。每条多肽链中的中心氨基酸残基被参与交联形成的L - 半胱氨酰残基取代。每个交联分子被认为包含两个三官能分支点，即两个L - 半胱氨酰残基的α - 碳原子。对于中等分子量的分子，随机飞行统计对(g)（定义为含有相同数量氨基酸残基的支链和线性多肽的((s^2)_0)之比）的估计效果较差。随着分子量变为无穷大，通过随机飞行统计和旋转异构体状态理论获得的(g)值趋于一致。(g)与其随机飞行值的偏差与线性多肽的特征比((s^2)_0 / n_p l_p^2)的大小相关。肽键数为(n_p)，(l_p)表示相邻α - 碳原子之间的距离。随机飞行统计在估计两条多肽链交联时((s^2)_0)的变化方面，比估计(g)时表现更好。
