Multiple quantum filtered NMR studies of the interaction between collagen and water in the tendon
Multiple quantum filtered NMR studies of the interaction between collagen and water in the tendon
复制标题
DOI：
10.1021/ja011791n
复制
发表时间：
2002-03-27
影响因子：
15
通讯作者：
Navon, G
中科院分区：
文献类型：
--
作者：
Eliav, U;Navon, G
我们研究了水和牛跟腱中大分子蛋白质（如胶原蛋白）之间磁化传递的物理过程和化学反应。由于这种蛋白质的NMR谱被非常大的偶极相互作用加宽，因此蛋白质上的各种官能团的NMR峰不能基于它们不同的化学位移而彼此分离。观察蛋白质光谱的另一个复杂性是大量水的强烈窄峰。因此，蛋白质内或水与蛋白质之间的磁化传递（MT）不能依赖于化学位移的差异，而这在液体中通常是可能的。我们提出了一种方法，分离的蛋白质光谱的水光谱的基础上，它们不同的分子内偶极相互作用，使排他性的激发的蛋白质或水。因此，可以测量蛋白质光谱以及蛋白质内的自旋扩散效应。此外，可以测量从蛋白质到水的MT速率，反之亦然。两种类型的机制被认为是MT：化学交换和偶极相互作用相关的过程（如NOE）。通过检查以下实验条件的影响来区分它们：（a）温度;（B）pH;（c）浴液中D2 O与H2O的比率;（d）蛋白质与除水以外的小分子（如DMSO和甲醇）的相互作用。我们的研究结果使我们得出结论，MT是由蛋白质和水之间的偶极相互作用的冰点以下占主导地位，而蛋白质和水分子之间的质子交换是最重要的过程高于冰点。基于蛋白质的自旋温度是在比MT短得多的时间尺度上建立的这一事实，我们可以测量蛋白质光谱，这些光谱通过各种官能团对它们的贡献来区分;即，亚甲基的贡献与甲基的贡献不同。
We studied the physical processes and the chemical reactions involved in magnetization transfer between water and large proteins, such as Collagen, in bovine Achilles tendon. Since the NMR spectrum for such proteins is broadened by very large dipolar interactions, the NMR peaks of the various functional groups on the protein cannot be separated from one another on the basis of their different chemical shifts. A further complication in observing the protein spectrum is the intense narrow peak of the abundant water. Thus, magnetization transfer (MT) within the protein or between water and the protein cannot rely on differences in the chemical shifts, as is commonly possible in liquids. We present a method that separates the protein spectrum from that of the water spectrum on the basis of their different intramolecular dipolar interactions, enabling exclusive excitation of either the protein or water. As a result, the protein spectrum as well as the effect of spin diffusion within the protein can be measured. In addition, the MT rates from the protein to water and vice versa can be measured. Two types of mechanisms were considered for the MT: chemical exchange- and dipolar interaction-related processes (such as NOE). They were distinguished by examining the effects of the following experimental conditions: (a) temperature; (b) pH; (c) ratio of D2O to H2O in the bathing liquid; (d) interaction of the protein with small molecules other than water, such as DMSO and methanol. Our results lead us to the conclusion that the MT is dominated below the freezing point by the dipolar interaction between the protein and water, while an exchange of protons between the protein and the water molecules is the most significant process above the freezing point. On the basis of the fact that the spin temperature is established for the protein on a time scale much shorter than that of the MT, we could measure protein spectra that are distinguished by the contributions made to them by the various functional groups; i.e., contributions of methylenes were distinguished from those of methyls.