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Exact Solution to the Extended Zwanzig Model for Quasi-Sigmoidal Chemically Induced Denaturation Profiles: Specific Heat and Configurational Entropy

机译:拟S形化学诱导变性曲线的扩展Zwanzig模型的精确解:比热和构型熵

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Temperature and chemically induced denaturation comprise two of the most characteristic mechanisms to achieve the passage from the native stateNto any of the unstructured statesDjin the denatured ensemble in proteins and peptides. In this work we present a full analytical solution for the configurational partition function𝒵qsof a homopolymer chain poly-X in the extended Zwanzig model (EZM) for a quasisigmoidal denaturation profile. This solution is built up from an EZM exact solution in the case where the fractionαof native contacts follows exact linear dependence on denaturant’s concentrationζ; thus an analytical solution for𝒵Lin the case of an exact linear denaturation profile is also provided. A recently established connection between the numberνof potential nonnative conformations per residue and temperature-independent helical propensityωcomplements the model in order to identify specific proteinogenic poly-X chains, where X represents any of the twenty naturally occurring aminoacid residues. From𝒵qs, equilibrium thermodynamic potentials like entropy𝒮and average internal energy〈E〉and thermodynamic susceptibilities like specific heatC𝓋are calculated for poly-valine (poly-V) and poly-alanine (poly-A) chains. The influence of the rate at which native contacts denature as function ofζon thermodynamic stability is also discussed.
机译:温度和化学诱导的变性包括两个最典型的机制,以实现从天然状态N到任何非结构化状态Djin的传递,即蛋白质和肽中的变性集合体。在这项工作中,我们为准Z形变性轮廓的扩展Zwanzig模型(EZM)中的均聚物链聚-X的构型分配函数提供了完整的解析解决方案。当自然接触的分数α遵循变性剂浓度ζ的精确线性依赖关系时,此解决方案是基于EZM精确解决方案构建的;因此,在精确的线性变性曲线的情况下,也提供了一种分析解决方案。最近建立的每个残基潜在非天然构象数目与温度无关的螺旋倾向ω之间的联系是该模型的补充,以识别特定的蛋白多聚X链,其中X代表二十个天然氨基酸残基中的任何一个。从s算出聚缬氨酸(poly-V)和聚丙氨酸(poly-A)的平衡热力学势(如熵)和平均内能(E)和热力学磁化率(如比热C&#x1D4CB)。链。还讨论了天然接触变性速率随ζ函数的变化对热力学稳定性的影响。

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