Cierpicki T, Otlewski J
Laboratory of Protein Engineering, Institute of Biochemistry and Molecular Biology, University of Wrocław, Poland.
J Biomol NMR. 2001 Nov;21(3):249-61. doi: 10.1023/a:1012911329730.
Correlations between amide proton temperature coefficients (deltasigmaHN/deltaT) and hydrogen bonds were investigated for a data set of 793 amides derived from 14 proteins. For amide protons showing temperature gradients more positive than -4.6 ppb/K there is a hydrogen bond predictivity value exceeding 85%. It increases to over 93% for amides within the range between -4 and -1 ppb/K. Detailed analysis shows an inverse proportionality between amide proton temperature coefficients and hydrogen bond lengths. Furthermore, for hydrogen bonds of similar bond lengths, values of temperature gradients in alpha-helices are on average I ppb/K more negative than in beta-sheets. In consequence. a number of amide protons in alpha-helices involved in hydrogen bonds shorter than 2 A show deltasigmaHN/deltaT < -4.6 ppb/K. Due to longer hydrogen bonds, 90% of amides in 3(10) helices and 98% in beta-turns have temperature coefficients more positive than -4.6ppb/K. Ring current effect also significantly influences temperature coefficients of amide protons. In seven out of eight cases non-hydrogen bonded amides strongly deshielded by neighboring aromatic rings show temperature coefficients more positive than -2 ppb/K. In general, amide proton temperature gradients do not change with pH unless they correspond to conformational changes. Three examples of pH dependent equilibrium showing hydrogen bond formation at higher pH were found. In conclusion, amide proton temperature coefficients offer an attractive and simple way to confirm existence of hydrogen bonds in NMR determined structures.
对来自14种蛋白质的793个酰胺数据集，研究了酰胺质子温度系数（deltasigmaHN/deltaT）与氢键之间的相关性。对于温度梯度比-4.6 ppb/K更正的酰胺质子，氢键预测值超过85%。对于-4至-1 ppb/K范围内的酰胺，该值增加到93%以上。详细分析表明，酰胺质子温度系数与氢键长度成反比。此外，对于键长相似的氢键，α-螺旋中温度梯度的值平均比β-折叠中更负1 ppb/K。因此，α-螺旋中一些参与短于2 Å氢键的酰胺质子显示deltasigmaHN/deltaT < -4.6 ppb/K。由于氢键较长，3(10)螺旋中90%的酰胺和β-转角中98%的酰胺的温度系数比-4.6 ppb/K更正。环电流效应也显著影响酰胺质子的温度系数。在八个案例中的七个中，被相邻芳香环强烈去屏蔽的非氢键酰胺显示温度系数比-2 ppb/K更正。一般来说，酰胺质子温度梯度不会随pH值变化，除非它们对应于构象变化。发现了三个在较高pH值下显示氢键形成的pH依赖性平衡的例子。总之，酰胺质子温度系数为在NMR确定的结构中确认氢键的存在提供了一种有吸引力且简单的方法。
