Lockhart D J, Kim P S
Department of Biology, Massachusetts Institute of Technology, Cambridge Center 02142.
Science. 1993 Apr 9;260(5105):198-202. doi: 10.1126/science.8469972.
Electrostatic interactions in proteins are potentially quite strong, but these interactions are mitigated by the screening effects of water, ions, and nearby protein atoms. The early work of Kirkwood and Westheimer on small organic molecules showed that the extent of the screening may depend on whether charged or dipolar groups are involved. The dielectric and ionic screening of the interactions between the dipolar backbone amide groups of monomeric alpha helices and either (i) solvent-exposed charges or (ii) solvent-exposed dipoles at the amino terminus was measured. The dielectric screening effects are an order of magnitude greater for the backbone-charge interactions than for the backbone-dipole interactions, and the ionic strength dependence is substantially different in the two cases. These results suggest that interactions that involve the dipolar groups of proteins may be relatively more important for stability and function than is generally thought.
蛋白质中的静电相互作用可能相当强，但这些相互作用会因水、离子和附近蛋白质原子的屏蔽效应而减弱。柯克伍德和韦斯特海默早期对小分子的研究表明，屏蔽程度可能取决于所涉及的是带电基团还是偶极基团。测量了单体α螺旋的偶极主链酰胺基团与（i）溶剂暴露电荷或（ii）氨基末端溶剂暴露偶极之间相互作用的介电和离子屏蔽。主链 - 电荷相互作用的介电屏蔽效应比主链 - 偶极相互作用大一个数量级，并且在这两种情况下离子强度依赖性有很大不同。这些结果表明，涉及蛋白质偶极基团的相互作用对于稳定性和功能可能比一般认为的更为重要。
