Döring K, Beck W, Konermann L, Jähnig F
Max-Planck-Institut für Biologie, Abteilung Membranbiochemie, Tübingen, Germany.
Biophys J. 1997 Jan;72(1):326-34. doi: 10.1016/S0006-3495(97)78671-5.
The membrane protein porin and a synthetic polypeptide of 21 hydrophobic residues were inserted into detergent micelles or lipid membranes, and the fluorescence of their single tryptophan residue was measured in the time-resolved and polarized mode. In all cases, the tryptophan fluorescence exhibits a long-lifetime component of about 20 ns. This long-lifetime component was exploited to detect slow orientational motions in the range of tens of nanoseconds via the anisotropy decay. For this purpose, the analysis of the anisotropy has to be extended to account for different orientations of the dipoles of the short- and long-lifetime components. This is demonstrated for porin and the polypeptide solubilized in micelles, in which the longest relaxation time reflects the rotational diffusion of the micelle. When the polypeptide is inserted into lipid membranes, it forms a membrane-spanning alpha-helix, and the slowest relaxation process is interpreted as reflecting orientational fluctuations of the helix.
将膜蛋白孔蛋白和一个由21个疏水残基组成的合成多肽插入去污剂胶束或脂质膜中，并以时间分辨和偏振模式测量它们单个色氨酸残基的荧光。在所有情况下，色氨酸荧光都表现出约20纳秒的长寿命成分。利用这一长寿命成分，通过各向异性衰减来检测几十纳秒范围内的缓慢取向运动。为此，各向异性分析必须扩展，以考虑短寿命和长寿命成分偶极子的不同取向。这在溶解于胶束中的孔蛋白和多肽中得到了证明，其中最长的弛豫时间反映了胶束的旋转扩散。当多肽插入脂质膜时，它形成一个跨膜α螺旋，最慢的弛豫过程被解释为反映螺旋的取向波动。
