Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield, S10 2TN, UK.
J Biomol NMR. 2012 Jan;52(1):57-64. doi: 10.1007/s10858-011-9583-4. Epub 2011 Nov 11.
Temperature coefficients have been measured for backbone amide (1)H and (15)N nuclei in the B1 domain of protein G (GB1), using temperatures in the range 283-313 K, and pH values from 2.0 to 9.0. Many nuclei display pH-dependent coefficients, which were fitted to one or two pK(a) values. (1)H coefficients showed the expected behaviour, in that hydrogen-bonded amides have less negative values, but for those amides involved in strong hydrogen bonds in regular secondary structure there is a negative correlation between strength of hydrogen bond and size of temperature coefficient. The best correlation to temperature coefficient is with secondary shift, indicative of a very approximately uniform thermal expansion. The largest pH-dependent changes in coefficient are for amides in loops adjacent to sidechain hydrogen bonds rather than the amides involved directly in hydrogen bonds, indicating that the biggest determinant of the temperature coefficient is temperature-dependent loss of structure, not hydrogen bonding. Amide (15)N coefficients have no clear relationship with structure.
已在 283-313 K 的温度范围内和 2.0 至 9.0 的 pH 值下测量了蛋白 G（GB1）B1 结构域中骨架酰胺（1）H 和（15）N 核的温度系数。许多核显示出 pH 依赖性系数，这些系数拟合到一个或两个 pK（a）值。（1）H 系数表现出预期的行为，即氢键酰胺的负值较小，但对于那些在规则二级结构中参与强氢键的酰胺，氢键的强度与温度系数的大小呈负相关。与温度系数的最佳相关性是与二级位移相关，表明热膨胀非常均匀。系数的最大 pH 依赖性变化是侧链氢键相邻环中的酰胺，而不是直接参与氢键的酰胺，这表明温度系数的最大决定因素是结构的温度依赖性丧失，而不是氢键。酰胺（15）N 系数与结构没有明显关系。
