Dynamic mechanism of halide salts on the phase transition of protein models, poly(N-isopropylacrylamide) and poly(N,N-diethylacrylamide)
Dynamic mechanism of halide salts on the phase transition of protein models, poly(N-isopropylacrylamide) and poly(N,N-diethylacrylamide)
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卤化物盐对蛋白质模型聚(N-异丙基丙烯酰胺)和聚(N,N-二乙基丙烯酰胺)相变的动力学机制
DOI：
10.1039/d0cp01366h
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发表时间：
2020
影响因子：
3.3
通讯作者：
Feng Jiwen
中科院分区：
文献类型：
--
作者：
Yan Xiaoshuang;Chu Yueying;Liu Biaolan;Ru Geying;Di Yi;Feng Jiwen
盐对蛋白质系统的影响尚未完全了解。采用多核NMR、色散校正密度泛函理论（DFT-D）和动态光散射（DLS）方法研究了三种卤化物盐（NaI、NaBr和NaCl）与两种蛋白质模型（PNIPAM和PDEA）的离子动力学行为.由聚合物引起的离子线宽和化学位移的变化清楚地说明了阴离子而不是阳离子直接与聚合物相互作用。从表征聚合物-阴离子相互作用强度的阴离子的NMR横向弛豫速率的变温测量，Cl−/Br−/I−在相变期间的演化行为在每个聚合物系统中是相似的，但在两个聚合物系统之间是不同的。在加热过程中，PNIPAM的相转变与阴离子的NMR横向弛豫速率同步变化，但在PDEA相转变前3 ~ 4.5 °C时，横向弛豫速率迅速下降并消失。通过结合DFT-D和DLS数据，弛豫结果意味着阴离子在完全聚合物脱水或塌陷之前从与PDEA相互作用的位点逃逸，这可以归因于缺乏阴离子-NH相互作用。PNIPAM和PDEA体系中阴离子的不同动态演化为我们理解蛋白质在复杂盐水溶剂中折叠的微观机制提供了重要线索。
The effects of salts on protein systems are not yet fully understood. We investigated the ionic dynamics of three halide salts (NaI, NaBr, and NaCl) with two protein models, namely poly(N-isopropylacrylamide) (PNIPAM) and poly(N,N-diethylacrylamide) (PDEA), using multinuclear NMR, dispersion corrected density functional theory (DFT-D) calculations and dynamic light scattering (DLS) methods. The variation in ionic line-widths and chemical shifts induced by the polymers clearly illustrates that anions rather than cations interact directly with the polymers. From the variable temperature measurements of the NMR transverse relaxation rates of anions, which characterize the polymer–anion interaction intensities, the evolution behaviors of Cl−/Br−/I− during phase transitions are similar in each polymer system but differ between the two polymer systems. The NMR transverse relaxation rates of anions change synchronously with the phase transition of PNIPAM upon heating, but they drop rapidly and vanish about 3–4.5 °C before the phase transition of PDEA. By combining the DFT-D and DLS data, the relaxation results imply that anions escape from the interacting sites with PDEA prior to full polymer dehydration or collapse, which can be attributed to the lack of anion–NH interactions. The different dynamic evolutions of the anions in the PNIPAM and PDEA systems give us an important clue for understanding the micro-mechanism of protein folding in a complex salt aqueous solvent.