Relating Trp-Glu dipeptide fluorescence to molecular conformation: The role of the discrete chi 1 and chi 2 angles
Relating Trp-Glu dipeptide fluorescence to molecular conformation: The role of the discrete chi 1 and chi 2 angles
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DOI：
10.1002/jcc.23288
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发表时间：
2013-07-05
影响因子：
3
通讯作者：
Juszczak, Laura J.
中科院分区：
文献类型：
--
作者：
Eisenberg, Azaria Solomon;Juszczak, Laura J.
分子动力学（MD），再加上荧光数据的带电二肽的色氨酸谷氨酸（Trp-Glu），揭示了一个详细的图片如何特定的构象影响荧光。荧光发射光谱和时间分辨发射测量已收集所有四个带电物种。还对Trp-Glu物质进行了长度为20至30 ns的MD模拟，因为模拟提供了可以与荧光数据相关的水相构象数据。计算表明，每个二肽种类的特征在于一组相似的六个离散Chi 1、Chi 2二面角对。优选的Chi 1角60度、180度和300度在末端胺相对于吲哚环的定位中起重要作用。60度的Chi 1角导致骨架在吲哚环上的重叠，并且环与末端胺没有相互作用。180度和300度的Chi 1值导致主链远离吲哚环的延伸和NH3阳离子与吲哚的相互作用。这种相互作用被认为是电荷转移猝灭的原因。两个荧光寿命和它们相应的振幅与所有四个带电Trp-Glu二肽的Chi 1角概率分布相关。荧光发射带最大值也与拟定的末端胺阳离子荧光淬灭模式一致。(c)2013 Wiley Periodicals，Inc.
Molecular dynamics (MD), coupled with fluorescence data for charged dipeptides of tryptophanyl glutamic acid (Trp-Glu), reveal a detailed picture of how specific conformation affects fluorescence. Fluorescence emission spectra and time-resolved emission measurements have been collected for all four charged species. MD simulations 20 to 30 ns in length have also been carried out for the Trp-Glu species, as simulation provides aqueous phase conformational data that can be correlated with the fluorescence data. The calculations show that each dipeptide species is characterized by a similar set of six, discrete Chi 1, Chi 2 dihedral angle pairs. The preferred Chi 1 angles60 degrees, 180 degrees, and 300 degrees play the significant role in positioning the terminal amine relative to the indole ring. A Chi 1 angle of 60 degrees results in the arching of the backbone over the indole ring and no interaction of the ring with the terminal amine. Chi 1 values of 180 degrees and 300 degrees result in an extension of the backbone away from the indole ring and a NH3 cation- interaction with indole. This interaction is believed responsible for charge transfer quenching. Two fluorescence lifetimes and their corresponding amplitudes correlate with the Chi 1 angle probability distribution for all four charged Trp-Glu dipeptides. Fluorescence emission band maxima are also consistent with the proposed pattern of terminal amine cation quenching of fluorescence. (c) 2013 Wiley Periodicals, Inc.