Liang Li, Yao Ping, Jiang Ming
Department of Macromolecular Science and Key Laboratory of Molecular Engineering of Polymer, Fudan University, Shanghai 200433, China.
Biomacromolecules. 2005 Sep-Oct;6(5):2748-55. doi: 10.1021/bm050250d.
Apocytochrome c interacts with two copolymers: poly(isobutylene-alt-maleic acid) (PIMA) and poly(1-tetradecene-alt-maleic acid) (PTMA). The interaction leads to apocytochrome c, a conformational change from random coil to alpha-helical structure. The alpha-helix content is influenced by the copolymer concentration, the length of alkyl chain of the copolymers, and pH of the medium. The electrostatic attraction between the copolymer and protein is an indispensable factor for the folding of the protein at acid pH. The hydrophobic interaction is an important factor over the entire pH range, especially when both the copolymer and protein carry negative charges at alkaline pH. The electrostatic and hydrophobic attractions between the copolymer and protein exclude water molecules, promoting the formation of hydrogen bonds within the helical structure. On the other hand, the hydrogen bonds formed between the ionized carboxyl of the copolymer and the amide of the protein partly restrain the formation of hydrogen bonds within the helical structure when the copolymer concentration is higher at pH 6.5 and 10.5.
脱辅基细胞色素c与两种共聚物相互作用：聚（异丁烯-alt-马来酸）（PIMA）和聚（1-十四碳烯-alt-马来酸）（PTMA）。这种相互作用导致脱辅基细胞色素c的构象从无规卷曲转变为α-螺旋结构。α-螺旋含量受共聚物浓度、共聚物烷基链长度和介质pH值的影响。在酸性pH条件下，共聚物与蛋白质之间的静电吸引是蛋白质折叠不可或缺的因素。在整个pH范围内，疏水相互作用都是一个重要因素，尤其是在碱性pH条件下共聚物和蛋白质都带负电荷时。共聚物与蛋白质之间的静电和疏水吸引排除了水分子，促进了螺旋结构内氢键的形成。另一方面，当在pH 6.5和10.5时共聚物浓度较高时，共聚物的离子化羧基与蛋白质的酰胺之间形成的氢键部分抑制了螺旋结构内氢键的形成。
