Lee K C, Hu W, Cross T A
Department of Chemistry, Florida State University, Tallahasee 32306-3006.
Biophys J. 1993 Sep;65(3):1162-7. doi: 10.1016/S0006-3495(93)81150-0.
A detailed experimental description of molecular dynamics requires an accurate description of the global correlation time. For the gramicidin cation-selective channel the local dynamics of the polypeptide backbone are thought to play a very significant role in the functional process of this channel which occurs on the 10-100-ns time scale. By solid-state NMR spectroscopy an experimental description of the local dynamics including a description of the axis about which the motions occur, the amplitude of the motions, whether they are diffusional or discontinuous and the frequency of the motions is possible. Initial interpretations of the NMR data for this polypeptide backbone in fully hydrated lipid bilayers suggests that the time scale for the local motions is the same as the kinetic time scale (North and Cross, 1993). Here the global correlation time is found from d4-Ala3 and d4-Ala5-gramicidin A powder pattern spectra to be 36 microseconds at 309 K. This surprisingly long correlation time may reflect the high viscosity of the peptide environment or possibly the higher molecular weight of a peptide-lipid aggregate. Furthermore, this reassessment of the global correlation time supports the initial interpretation of relaxation data for the local motions.
对分子动力学进行详细的实验描述需要准确描述全局相关时间。对于短杆菌肽阳离子选择性通道，多肽主链的局部动力学被认为在该通道发生在10 - 100纳秒时间尺度上的功能过程中起着非常重要的作用。通过固态核磁共振光谱法，可以对局部动力学进行实验描述，包括对运动发生的轴、运动幅度、运动是扩散性的还是不连续的以及运动频率的描述。对完全水合脂质双层中该多肽主链的核磁共振数据的初步解释表明，局部运动的时间尺度与动力学时间尺度相同（诺斯和克罗斯，1993年）。在这里，从d4 - Ala3和d4 - Ala5 - 短杆菌肽A粉末图谱光谱中发现，在309 K时全局相关时间为36微秒。这个惊人的长相关时间可能反映了肽环境的高粘度，或者可能是肽 - 脂质聚集体的较高分子量。此外，对全局相关时间的这种重新评估支持了对局部运动弛豫数据的初步解释。
