Sharma Ganga P, Reshetnyak Yana K, Andreev Oleg A, Karbach Michael, Müller Gerhard
Department of Physics, University of Rhode Island, Kingston RI 02881, USA.
Fachgruppe Physik, Bergische Universität Wuppertal, D-42097 Wuppertal, Germany.
J Stat Mech. 2015 Jan;2015. doi: 10.1088/1742-5468/2015/01/P01034. Epub 2015 Jan 27.
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 -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.
我们给出了一个微观统计力学模型的精确解，该模型用于描述长多肽在无结构卷曲构象和α-螺旋构象之间的转变。假设多肽吸附在极性和非极性环境之间的界面上，例如由水和膜的脂质双层所构成的环境。界面上的卷曲-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，构象变化呈现为交叉转变、不连续转变或连续转变，其中螺旋度作为序参量。我们的模型构建为一个由从螺旋伪真空中激活的统计相互作用准粒子组成的系统。这些粒子代表卷曲构象中相邻残基之间的连接，它们在二维空间中形成自回避随机游走。给出了关于螺旋度、熵、热容量以及卷曲和螺旋片段的平均数量和大小的明确结果。
