The importance of coulombic interactions for the induction of β structure in lysine oligomers by sodium dodecyl sulfate
The importance of coulombic interactions for the induction of β structure in lysine oligomers by sodium dodecyl sulfate
复制标题
库仑相互作用对于十二烷基硫酸钠诱导赖氨酸低聚物中 β 结构的重要性
作者：
W. Mattice;W. Harrison
在25°C的十二烷基硫酸钠水溶液中获得了三（L -赖氨酸）、四（L -赖氨酸）和五（L -赖氨酸）的圆二色性光谱。在洗涤剂浓度超过0.01 m时，十二烷基硫酸钠对这些低聚物均无显著影响，文献结果表明，在此条件下，高分子量聚合物形成β结构。在洗涤剂浓度接近3.5 × 10−4 M时，五元（L -赖氨酸）而不是较小的低聚物发生构象变化。在这些条件下，它的圆二色性与聚赖氨酸在十二烷基硫酸钠中形成β结构时所观察到的圆二色性基本相同。五（L -赖氨酸）的溶液，表现出这种修饰的圆二色性，也是浑浊的，导致低聚物形成了分子间β结构的结论。当这些实验在0.1 M氢氧化钠存在下进行时，十二烷基硫酸钠既不产生浊度，也不产生修改的圆二色光谱。这些观察结果提供了令人信服的证据，证明阴离子洗涤头和阳离子赖氨酸氨基之间的库仑相互作用对于十二烷基硫酸钠诱导的五（L -赖氨酸）构象变化是必不可少的。
Circular dichroism spectra have been obtained for tri(L‐lysine), tetra(L‐lysine), and penta(L‐lysine) in aqueous sodium dodecyl sulfate at 25°C. None of the oligomers are affected significantly by sodium dodecyl sulfate at detergent concentrations exceeding 0.01 M. Literature results show that the high‐molecular‐weight polymer forms a β strucure under these conditions. At detergent concentrations near 3.5 × 10−4 M the penta(L‐lysine), but not the smaller oligomers, undergoes a conformational change. Its circular dichroism under these conditions is essentially identical to that observed with poly(L‐lysine) when it forms a β structure in sodium dodecyl sulfate. Solutions of the penta(L‐lysine), which exhibit this modified circular dichroism, are also turbid, leading to the conclusion that the oligomer has formed an intermolecular β structure. When these experiments are conducted in the presence of 0.1 M sodium hydroxide, the sodium dodecyl sulfate produces neither turbidity nor a modified circular dichroism spectrum. These observations provide compelling evidence that Coulombic interaction between the anionic detergent head and the cationic lysyl amino groups is essential for the conformational change induced in penta(L‐lysine) by sodium dodecyl sulfate.