Wet Gecko β-角蛋白的分子结构和动力学,ACS Biomaterials Science & Engineering

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Wet Gecko β-角蛋白的分子结构和动力学
ACS Biomaterials Science & Engineering ( IF 5.4 ) Pub Date : 2022-12-16 , DOI: 10.1021/acsbiomaterials.2c01022
Hossein Eslami _{1,

2} , Tobias Materzok ₁ , Florian Müller-Plathe ₁

Affiliation

进行分子动力学模拟以研究壁虎角蛋白中吸水的分子图以及相对湿度 (RH) 对水溶胀角蛋白局部结构和动力学的影响。在低 RH 下，通过水与角蛋白亲水基团的氢键结合发生吸水。在高 RH (>80%) 下，额外的水分子通过氢键连接到酰胺连接的水分子的第一“层”（多分子吸附），从而产生 S 形吸附等温线。这导致在角蛋白的亲水基团周围形成大的链状簇，随着相对湿度的进一步增加，形成渗透水网络。对吸附在角蛋白中的水分子动力学的检查表明，存在两种状态，结合的和游离的，用于水。这些状态下的水动力学取决于相对湿度。在低 RH 下，需要将紧密结合的水分子向角蛋白进行大规模平移运动，以重塑角蛋白的整个水合壳。在高 RH (>80%) 下，水分子在两种状态之间交换得更快。水分子的质心均方位移表明水分子在角蛋白溶剂化壳中的跳跃运动。跳跃机制在 RHs < 80% 时更为明显。在较高的相对湿度下，通过水团（水网络）的水翻译占主导地位。我们已经观察到动态特性对 RH 依赖性的两种情况：动态逐渐增加超过 10% < RH < 80% 的情况和在 RH > 80% 时剧烈动态加速的情况。后一种状态恰好在吸水和体积膨胀也增加得多的地方开始，并且观察到壁虎角蛋白的弹性特性发生急剧变化。观察到所有动力学过程的弛豫时间与壁虎角蛋白的含水量之间几乎呈线性关系。

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Molecular Structure and Dynamics in Wet Gecko β-Keratin

Molecular dynamics simulations are performed to investigate the molecular picture of water sorption in gecko keratin and the influence of relative humidity (RH) on the local structure and dynamics in water-swollen keratin. At low RHs, water sorption occurs through hydrogen bonding of water with the hydrophilic groups of keratin. At high RHs (>80%), additional water molecules connect to the first “layer” of amide-connected water molecules (multimolecular sorption) through hydrogen bonds, giving rise to a sigmoidal shape of the sorption isotherm. This causes the formation of large chain-like clusters surrounding the hydrophilic groups of keratin, which upon a further increase of the RH form a percolating water network. An examination of the dynamics of water molecules sorbed in keratin demonstrates that there are two states, bound and free, for water. The dynamics of water in these states depends on the RH. At low RHs, large-scale translational motions of tightly bound water molecules to keratin are needed to remake the entire hydration shell of the keratin. At high RHs (>80%), the water molecules more quickly exchange between the two states. The center-of-mass mean-square displacement of water molecules indicates a hopping motion of water molecules in the keratin solvation shell. The hopping mechanism is more pronounced at RHs < 80%. At higher RHs, water translation through water clusters (water network) dominates. We have observed two regimes for the dependence of dynamical properties on the RH: a regime of gradual increase of the dynamics over 10% < RH < 80% and a regime of drastic dynamic acceleration at RH > 80%. The latter regime begins exactly where the water uptake and the volume swelling also increase much more and where a drastic change in the elastic properties of gecko keratin has been observed. A nearly linear relation between the relaxation times for all dynamical processes and the water content of gecko keratin is observed.

更新日期：2022-12-16

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