Skalicky J J, Selsted M E, Pardi A
Department of Chemistry and Biochemistry, University of Colorado-Boulder 80309-0215.
Proteins. 1994 Sep;20(1):52-67. doi: 10.1002/prot.340200107.
The exchange kinetics for the slowly exchanging amide hydrogens in three defensins, rabbit NP-2, rabbit NP-5, and human HNP-1, have been measured over a range of pH at 25 degrees C using 1D and 2D NMR methods. These NHs have exchange rates 10(2) to 10(5) times slower than rates from unstructured model peptides. The observed distribution of exchange rates under these conditions can be rationalized by intramolecular hydrogen bonding of the individual NHs, solvent accessibility of the NHs, and local fluctuations in structure. The temperature dependencies of NH chemical shifts (NH temperature coefficients) were measured for the defensins and these values are consistent with the defensin structure. A comparison is made between NH exchange kinetics, NH solvent accessibility, and NH temperature coefficients of the defensins and other globular proteins. Titration of the histidine side chain in NP-2 was examined and the results are mapped to the three-dimensional structure.
利用一维和二维核磁共振方法，在25℃下的一系列pH值范围内，测定了三种防御素（兔NP - 2、兔NP - 5和人HNP - 1）中缓慢交换的酰胺氢的交换动力学。这些NH的交换速率比无结构模型肽的速率慢10²至10⁵倍。在这些条件下观察到的交换速率分布可以通过单个NH的分子内氢键、NH的溶剂可及性和结构的局部波动来解释。测量了防御素的NH化学位移的温度依赖性（NH温度系数），这些值与防御素结构一致。对防御素与其他球状蛋白的NH交换动力学、NH溶剂可及性和NH温度系数进行了比较。研究了NP - 2中组氨酸侧链的滴定，并将结果映射到三维结构上。
