RULES FOR ALPHA-HELIX FORMATION

我们的目标是预测天然序列的α-螺旋含量 缩氨酸 预测的规则正在开发和测试中。 零阶规则基于标准的三个参数 螺旋-线团转变理论（sigma，s，delta H）。 最近的研究工作表明 内在的螺旋形成 不同氨基酸的趋势（s值），当这些是 通过在基于丙氨酸的参考肽中的取代来确定。 的 一级规则包括用于侧链相互作用的附加项， 比如离子对相互作用，我们最近已经确定了。 Δ H，每个残基螺旋形成的焓变， 与D.W.教授合作用量热法测定。伯伦的 其它参数由热展开、曲线 通过圆二色性测量具有重复序列的肽， 不同的链长。 这次试装是与 教授 J.A.舍曼作为这项工作的背景， 替代的依赖性正在研究，与 Lifson-Roig理论预测的效果和上下文依赖性是 通过改变相邻残基来研究。 s之间的区别 在丙氨酸基肽和主客体共聚物中发现的值， 羟丁基-L-谷氨酰胺（HBLG）作为宿主被认为是由 当HBLG是宿主时，结果的强上下文依赖性。 我们将 通过上下文依赖性实验来验证这一假设。

Our goal is to predict the alpha-helix contents of natural-sequence peptides. The rules for prediction are being developed and tested now. The zero-order rules are based on the three parameters of standard helix-coil transition theory (sigma,s,delta H). Recent work has shown that there are large differences between the intrinsic helix-forming tendencies (the s values) of different amino acids when these are determined by substitution in alanine-based reference peptides. The first-order rules include additional terms for side-chain interactions, such as ion pair interactions, which we have been determining recently. Delta H, the enthalpy change of helix formation per residue, is being determined calorimetrically in collaboration with Prof. D.W. Bolen. The other parameters are being determined from thermal unfolding, curves measured by circular dichroism for peptides with repeating sequences and varying chain lengths. The fitting is being done in collaboration with Prof. J.A. Schellman. As background for this work, the position dependence of a substitution is being studied in comparison with the effect predicted by the Lifson-Roig theory and the context dependence is studied by varying neighboring residues. The difference between the s values found in alanine-based peptides and in host-guest Copolymers with hydroxybutyl-L-glutamine (HBLG) as the host is thought to arise from a strong context dependence of the results when HBLG is the host. We will test this hypothesis by experiments on context dependence.