Urea orientation at protein surfaces
Urea orientation at protein surfaces
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DOI：
10.1021/ja075034m
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发表时间：
2007-12-12
影响因子：
15
通讯作者：
Cremer, Paul S.
中科院分区：
文献类型：
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作者：
Chen, Xin;Sagle, Laura B.;Cremer, Paul S.
我们利用振动和频率光谱（VSFS）的独特能力来研究蛋白质表面的界面尿素分子。实验在牛血清白蛋白/水界面进行。界面尿素的绝对取向可以直接用VSFS法测定。结果发现，在高pH下，尿素的NH基团指向蛋白质，蛋白质带负电荷。在低pH下，蛋白质带正电荷，取向翻转。这种行为类似于界面水的行为。尿素和蛋白质之间的直接相互作用本质上应该是静电的，因此对蛋白质的电荷状态非常敏感。蛋白质的尿素变性对电荷不敏感，这与直接的相互作用机制不一致。
We have exploited the unique ability of vibrational sum frequency spectroscopy (VSFS) to investigate interfacial urea molecules at protein surfaces. Experiments were carried out at the bovine serum albumin/water interface. The absolute orientation of interfacial urea could be followed directly by VSFS. It was found that urea orients with its NH groups pointing toward the protein at high pH, where the protein is negatively charged. The orientation flips at low pH, where the protein is positively charged. This behavior resembles that of interfacial water. The direct interactions between urea and proteins should be electrostatic in nature and, therefore, very sensitive to the charge state of the protein. Urea denaturation of proteins, however, is not sensitive to charge, which is inconsistent with a direct interaction mechanism.