We present the exact solution of a microscopic statistical mechanical model for the transformation of a long polypeptide between an unstructured coil conformation and an α-helix conformation. The polypeptide is assumed to be adsorbed to the interface between a polar and a non-polar environment such as realized by water and the lipid bilayer of a membrane. The interfacial coil-helix transformation is the first stage in the folding process of helical membrane proteins. Depending on the values of model parameters, the conformation changes as a crossover, a discontinuous transition, or a continuous transition with helicity in the role of order parameter. Our model is constructed as a system of statistically interacting quasiparticles that are activated from the helix pseudo-vacuum. The particles represent links between adjacent residues in coil conformation that form a self-avoiding random walk in two dimensions. Explicit results are presented for helicity, entropy, heat capacity, and the average numbers and sizes of sboth coil and helix segments.

中文翻译：

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水-脂界面多肽的螺旋-螺旋转变


我们提出了用于长多肽在非结构化卷曲构象和α-螺旋构象之间转换的微观统计力学模型的精确解。假定多肽被吸附到极性和非极性环境之间的界面，例如通过水和膜的脂质双层实现的。界面螺旋-螺旋转变是螺旋膜蛋白折叠过程的第一阶段。根据模型参数的值，构象在顺序参数的作用下以交叉、不连续转变或具有螺旋性的连续转变的形式变化。我们的模型被构建为一个由螺旋伪真空激活的统计相互作用的准粒子系统。这些粒子代表了线圈构象中相邻残基之间的链接，在二维中形成自回避随机游走。给出了螺旋度、熵、热容以及螺旋和螺旋段的平均数量和尺寸的明确结果。