SIDE CHAIN INTERACTIONS GOVERNING A-HELIX STABILITY

我们的目标是检测和测量特定的相互作用， 链，其影响分离的α-螺旋在水溶液中的稳定性 溶液 相互作用可以是两种类型：（1） 相邻残基之间的相互作用，以及（2）带电残基和 阿尔法螺旋偶极子 作为起始点，将图1的C-肽（残基1-13） 已知核糖核酸酶A在0 ℃，pH 5， 而Zimm-Bragg方程和主客体数据预测， 13-残基肽在水中可显示可测量的α-螺旋形成， 而与氨基酸序列或温度无关。 因此，具体 侧链相互作用对于C-肽螺旋稳定性一定是重要的。 我们的方法是使用化学合成的C肽类似物。 我们 已经发现，两个带电基团，Glu 2-和His 12+，在任何一端的， 螺旋在稳定C-肽螺旋中起关键作用。 我们有 还发现Glu 9可以被替换而不丧失螺旋稳定性， 因此一种可能的Glu 9-他的12+盐桥并不重要。 我们 会用同样的方法来检测谷氨酸Arg 10+盐桥。 测试 正在进行中，以检测可能的螺旋稳定相互作用， Glu 2-、His 12+和α-螺旋偶极子。 我们还将测试 在成对的特异性侧链中， 残基

Our aim is to detect and measure specific interactions involving side chains that affect the stability of an isolated Alpha-helix in aqueous solution. The interactions can be of two types: (1) interactions between neighboring residues, and (2) interactions between charged residues and the Alpha-helix dipole. As a starting point, the C-peptide (residues 1-13) of ribonuclease A is known to show 30% helix formation at 0 degrees C, pH 5, whereas the Zimm-Bragg equation and host-guest data predict that no 13-residue peptide can show measurable Alpha-helix formation in water, regardless of amino acid sequence or temperature. Consequently, specific side chain interactions must be important for C-peptide helix stability. Our approach is to use chemically synthesized analogs of C-peptide. We have found that two charged groups, Glu2- and His12+, at either end of the helix play a critical role in stabilizing the C-peptide helix. We have also found that Glu9 can be replaced without loss of helix stability, and therefore that a possible Glu9-...His12+ salt bridge is not important. We will use the same approach to test for a Glu2-...Arg10+ salt bridge. Tests are in progress to detect possible helix-stabilizing interactions involving Glu2-, His12+ and the Alpha-helix dipole. We will also test for neighbor-dependent interactions between side chains in pairs of specific residues.