CNR-IPCF, Largo Bruno Pontecorvo 3, I-56127 Pisa, Italy.
CNR-IPCF, Largo Bruno Pontecorvo 3, I-56127 Pisa, Italy; Dipartimento di Fisica, Università di Pisa, Largo Bruno Pontecorvo 3, I-56127 Pisa, Italy.
Biochim Biophys Acta Gen Subj. 2017 Jan;1861(1 Pt B):3553-3563. doi: 10.1016/j.bbagen.2016.04.027. Epub 2016 May 4.
The properties of the three dynamic processes, α-relaxation, ν-relaxation, and caged dynamics in aqueous mixtures and hydrated proteins are analogous to corresponding processes found in van der Waals and polymeric glass-formers apart from minor differences.
Collection of various experimental data enables us to characterize the structural α-relaxation of the protein coupled to hydration water (HW), the secondary or ν-relaxation of HW, and the caged HW process.
From the T-dependence of the ν-relaxation time of hydrated myoglobin, lysozyme, and bovine serum albumin, we obtain Ton at which it enters the experimental time windows of Mössbauer and neutron scattering spectroscopies, coinciding with protein dynamical transition (PDT) temperature Td. However, for all systems considered, the α-relaxation time at Ton or Td is many orders of magnitude longer. The other step change of the mean-square-displacement (MSD) at Tg_alpha originates from the coupling of the nearly constant loss (NCL) of caged HW to density. The coupling of the NCL to density is further demonstrated by another step change at the secondary glass temperature Tg_beta in two bio-protectants, trehalose and sucrose.
The structural α-relaxation plays no role in PDT. Since PDT is simply due to the ν-relaxation of HW, the term PDT is a misnomer. NCL of caged dynamics is coupled to density and show transitions at lower temperature, Tg_beta and Tg_alpha.
The so-called protein dynamical transition (PDT) of hydrated proteins is not caused by the structural α-relaxation of the protein but by the secondary ν-relaxation of hydration water. "This article is part of a Special Issue entitled "Science for Life" Guest Editor: Dr. Austen Angell, Dr. Salvatore Magazù and Dr. Federica Migliardo".
在水混合物和水合蛋白质中,三种动态过程(α-松弛、ν-松弛和笼形动力学)的性质与范德华和聚合玻璃形成体中的相应过程类似,除了一些微小的差异。
收集各种实验数据使我们能够描述与水合作用耦合的蛋白质的结构α-松弛(HW)、HW 的二级或ν-松弛以及笼形 HW 过程。
从水合肌红蛋白、溶菌酶和牛血清白蛋白的ν-松弛时间的 T 依赖性中,我们得到 Ton,在该温度下,它进入 Mössbauer 和中子散射光谱学的实验时间窗口,与蛋白质动力学转变(PDT)温度 Td 重合。然而,对于所有考虑的系统,在 Ton 或 Td 时的α-松弛时间长几个数量级。均方位移(MSD)的另一个阶跃变化源自笼形 HW 的几乎恒定损耗(NCL)与密度的耦合。在两种生物保护剂海藻糖和蔗糖中的次级玻璃化温度 Tg_beta 处的另一个阶跃变化进一步证明了 NCL 与密度的耦合。
结构α-松弛在 PDT 中不起作用。由于 PDT 仅仅是由于 HW 的ν-松弛,术语 PDT 是一个用词不当。笼形动力学的 NCL 与密度耦合,并在较低温度 Tg_beta 和 Tg_alpha 处显示转变。
水合蛋白质的所谓蛋白质动力学转变(PDT)不是由蛋白质的结构α-松弛引起的,而是由水合作用的二级ν-松弛引起的。“本文是一个特刊的一部分,题为“生命科学”,客座编辑:Austen Angell 博士、Salvatore Magazù 博士和 Federica Migliardo 博士”。