论文标题
鸟肾既可能引起并防止生物乳清分子的疏水崩溃
Guanidinium can both Cause and Prevent the Hydrophobic Collapse of Biomacromolecules
论文作者
论文摘要
进行了傅立叶变换红外和相变测量以及分子计算机模拟以及热力学建模的组合，以探测鸟嘌呤盐影响折叠状态的稳定性与未固定状态的弹性蛋白样多肽（ELP）（ELP）的稳定性的机制，一种未充电的热层。我们发现阳离子的作用高度依赖于与之配对的对抗。具体而言，GND+从ELP/水界面耗尽，发现与硫酸盐等充足的阴离子（如硫酸盐）配对时，可以稳定大分子的折叠状态。在这种情况下，稳定是通过排除的体积（或耗尽）效应发生的，从而将硫酸盐从ELP/水界面上强烈划分。有趣的是，在低盐浓度下，GND+与SCN-配对时，GND+稳定了ELP的折叠状态，这是ELP的强粘合剂。在这种情况下，发现阴离子和阳离子都富含聚合物的塌陷状态。由于GND+交联聚合物链共同链接在一起，因此崩溃的状态之所以受到青睐。此外，阴离子将GND+分配到聚合物表面。在较高的盐浓度（> 1.5 m）下，GNDSCN切换到稳定未填充的状态，因为足够量的GND+和SCN分配到聚合物表面以防止交联发生。最后，在第三种情况下，发现与聚合物（例如GNDCL）以中间方式相互作用的盐在所有盐浓度下都偏爱未固定的构象。
A combination of Fourier transform infrared and phase transition measurements as well as molecular computer simulations, and thermodynamic modeling were performed to probe the mechanisms by which guanidinium salts influence the stability of the collapsed versus uncollapsed state of an elastin-like polypeptide (ELP), an uncharged thermoresponsive polymer. We found that the cation's action was highly dependent upon the counteranion with which it was paired. Specifically, Gnd+ was depleted from the ELP/water interface and was found to stabilize the collapsed state of the macromolecule when paired with well-hydrated anions such as sulfate. Stabilization in this case occurred via an excluded volume (or depletion) effect, whereby sulfate was strongly partitioned away from the ELP/water interface. Intriguingly, at low salt concentrations, Gnd+ was also found to stabilize the collapsed state of the ELP when paired with SCN-, which is a strong binder for the ELP. In this case, the anion and cation were both found to be enriched in the collapsed state of the polymer. The collapsed state was favored because the Gnd+ crosslinked the polymer chains together. Moreover, the anion helped partition Gnd+ to the polymer surface. At higher salt concentrations (>1.5 M), GndSCN switched to stabilizing the uncollapsed state because a sufficient amount of Gnd+ and SCN- partitioned to the polymer surface to prevent cross-linking from occurring. Finally, in a third case, it was found that salts which interacted in an intermediate fashion with the polymer (e.g. GndCl) favored the uncollapsed conformation at all salt concentrations.
