Dynamical Model for the Counteracting Effects of Trimethylamine N-Oxide on Urea in Aqueous Solutions under Pressure.
Dynamical Model for the Counteracting Effects of Trimethylamine N-Oxide on Urea in Aqueous Solutions under Pressure.
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DOI：
10.1021/acs.jpcb.9b10844
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发表时间：
2020-03-12
期刊：
影响因子：
--
通讯作者：
Ichiye T
中科院分区：
文献类型：
--
作者：
Teng X;Ichiye T
在活细胞中发现的溶质中，尿素变性和三甲胺n -氧化物（TMAO）稳定蛋白质；此外，当尿素与氧化三甲胺的比例为2:1时，这些效果会被抵消。有趣的是，软骨鱼在海洋表面以相似的比例使用尿素和氧化三甲胺作为渗透剂，但随着深度的增加，氧化三甲胺的比例也在增加。这里，不同尿素：氧化三甲胺比例水溶液的分子动力学模拟表明，如果尿素：氧化三甲胺比例恒定，溶液中水的扩散系数随压力而变化，但令人惊讶的是，在这些鱼中发现的比例几乎与压力无关，作为深度的函数。这表明这一比例可能维持了水动力学的稳态。此外，扩散是由溶液中不同物质的氢键寿命决定的。基于这些观察，建立了一个氢键寿命的动力学模型，用于研究水溶液中溶质和水与蛋白质的氢键倾向。该模型既解释了氧化三甲胺对尿素变性的抵消作用，也解释了软骨鱼中发现的深度依赖性尿素：氧化三甲胺比例。
Of cosolutes found in living cells, urea denatures and trimethylamine N-oxide (TMAO) stabilizes proteins; furthermore, these effects cancel at a 2:1 ratio of urea to TMAO. Interestingly, cartilaginous fish use urea and TMAO as osmolytes at similar ratios at the ocean surface but with increasing fractions of TMAO at increasing depths. Here, molecular dynamics simulations of aqueous solutions with different urea:TMAO ratios show that the diffusion coefficients of water in the solutions vary with pressure if the urea:TMAO ratio is constant, but strikingly are almost pressure independent at the ratio found in these fish as a function of depth. This suggests that this ratio may be maintaining a homeostasis of water dynamics. In addition, diffusion is determined by hydrogen-bond lifetimes of the different species in the solution. Based on these observations, a dynamical model in terms of hydrogen-bond lifetimes is developed for the hydrogen bonding propensities of cosolutes and water in an aqueous solution to proteins. This model provides an explanation for both the counteracting effects of TMAO on urea denaturation and the depth-dependent urea:TMAO ratio found in cartilaginous fish.
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