Clayton A H, Sawyer W H
The Russell Grimwade School of Biochemistry and Molecular Biology, The University of Melbourne, Parkville, Victoria 3052, Australia.
Biophys J. 1999 Jun;76(6):3235-42. doi: 10.1016/S0006-3495(99)77475-8.
The fluorescence decay of tryptophan is a sensitive indicator of its local environment within a peptide or protein. We describe the use of frequency domain fluorescence spectroscopy to determine the conformational and environmental changes associated with the interaction of single tryptophan amphipathic peptides with a phospholipid surface. The five 18-residue peptides studied are based on a class A amphipathic peptide known to associate with lipid bilayers. The peptides contain a single tryptophan located at positions 2, 3, 7, 12, or 14 in the sequence. In aqueous solution, the peptides are unstructured and a triple-exponential function is required to fit the decay data. Association of the peptides with small unilamellar vesicles composed of egg phosphatidylcholine reduces the complexity of the fluorescence decays to a double exponential function, with a reduced dependence of the preexponential amplitude on peptide sequence. The data are interpreted in terms of a rotamer model in which the modality and relative proportions of the lifetime components are related to the population distribution of tryptophan chi1 rotamers about the Calpha-Cbeta bond. Peptide secondary structure and the disposition of the tryptophan residue relative to the lipid and aqueous phases in the peptide-lipid complex affect the local environment of tryptophan and influence the distribution of side-chain rotamers. The results show that measurement of the temporal decay of tryptophan emission provides a useful adjunct to other biophysical techniques for investigating peptide-lipid and protein-membrane interactions.
色氨酸的荧光衰减是其在肽或蛋白质中局部环境的敏感指标。我们描述了使用频域荧光光谱法来确定与单个色氨酸两亲性肽与磷脂表面相互作用相关的构象和环境变化。所研究的五个18个残基的肽基于已知与脂质双层结合的A类两亲性肽。这些肽在序列的第2、3、7、12或14位含有单个色氨酸。在水溶液中，肽是无结构的，需要用三指数函数来拟合衰减数据。肽与由鸡蛋磷脂酰胆碱组成的小单层囊泡的结合将荧光衰减的复杂性降低为双指数函数，预指数振幅对肽序列的依赖性降低。数据根据旋转异构体模型进行解释，其中寿命成分的模态和相对比例与色氨酸chi1旋转异构体围绕Cα-Cβ键的群体分布有关。肽二级结构以及色氨酸残基相对于肽-脂质复合物中脂质和水相的位置会影响色氨酸的局部环境，并影响侧链旋转异构体的分布。结果表明，测量色氨酸发射的时间衰减为研究肽-脂质和蛋白质-膜相互作用的其他生物物理技术提供了有用的辅助手段。
