An Indirect Chaotropic Mechanism for the Stabilization of Helix Conformation of Peptides in Aqueous Trifluoroethanol and Hexafluoro-2-propanol
作者:Richard Walgers、Tony C. Lee、Arthur Cammers-Goodwin
DOI:10.1021/ja973552z
日期:1998.5.1
behavior of the coil/helix transition. To define the TFE effect, solvent-dependent physicochemical behaviors of two molecular probes for solvent character were monitored and compared with the solvent dependence of peptide helix formation. The rate of decarboxylation of 6-nitro-3-carboxybenzisoxazole was determined in aqueous mixtures as a function of concentration for DMSO, EtOH, MeOH, iPrOH, HFIP, and
针对 2,2,2-三氟乙醇对肽构象(TFE 效应)的影响,提出了一种修正的间接机制,这表明在纯水中,螺旋状态的溶剂壳比无规卷曲状态更紧密。醇类助溶剂优先通过破坏溶剂壳来稳定螺旋状态,这对螺旋形成的自由能造成不利的焓和有利的熵贡献。采用这种修改后的机制是因为它最好地解释了线圈/螺旋转变的溶剂相关热力学行为。为了定义 TFE 效应,监测了两种溶剂特性分子探针的溶剂依赖性物理化学行为,并将其与肽螺旋形成的溶剂依赖性进行了比较。在水性混合物中测定 6-硝基-3-羧基苯并异恶唑的脱羧速率与 DMSO、EtOH、MeOH、iPrOH、HFIP 和 TFE 浓度的函数关系。将这些速率研究与螺旋形式的共溶剂相关热力学联系起来……