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首页> 外文期刊>Chemistry: A European journal >First Peptide-Based System of Rigid Donor - Rigid Interchromophore Spacer-Rigid Acceptor: A Structural and Photophysical Study
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First Peptide-Based System of Rigid Donor - Rigid Interchromophore Spacer-Rigid Acceptor: A Structural and Photophysical Study

机译：刚性供体的第一个基于肽的系统-刚性发色团间隔物-刚性受体：结构和光物理研究

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摘要

The results of X-ray diffraction analysis, fluorescence experiments and moleuclar mechanism calculations on the terminally protected hexapeptide -(S)Bin-Ala-Aib-TOAC-(Ala)_2- are presented. This is the first peptide investigated photophysically that is characterized by a) a rigid, ibnaphthyl-based #alpha#-amino acid (Bin) fluorophore,b) a rigid interchromophore bridge, the -Ala-Aib-sequence, and c) a rigid, nitroxide-based #alpha#-amino acid quencher (TOAC). In the crystal state the backbone fo the spectroscopically critical 1-4 segmetn of both independent molecules in the asymmetric unit of the hexapeptide is folded in a regular, left-handed 3_10-helix. The steady-state fluorescence spectra show a remarkable quenching of Bin emission by the TOAC residue located one complete turn of the helix apart. Time-resolved fluorescence measurements exhibit a biexponential decay with solvent-dependent lifetime components ranging from 0.5 to 1.5 ns and from 3 to 5 ns. Time-decay data combined with moleuclar mechanics calculations allowed us to assign these lifetimes to two left-handed 3_10-helical conformers in which an intramolecular electronic energy transfer from excited Bin to TOAC takes place. For a given solvent the difference between the two lifetimes primarily depends on a different relative orientation of the two chromophores in the conformers, which is in turn related to a different puckering of the TOAC cyclic system.
机译：给出了末端保护的六肽-（S）Bin-Ala-Aib-TOAC-（Ala）_2-的X射线衍射分析，荧光实验和分子机理计算的结果。这是用光物理方法研究的第一个肽，其特征是a）刚性的基于萘甲酰基的＃alpha＃-氨基酸（Bin）荧光团，b）刚性的发色团桥，-Ala-Aib序列，以及c）刚性的，基于氮氧化物的＃alpha＃-氨基酸淬灭剂（TOAC）。在晶体状态下，六肽不对称单元中两个独立分子的光谱关键的1-4节的骨架被折叠成规则的左手3_10螺旋。稳态荧光光谱显示，距螺旋完整一圈的TOAC残基可显着抑制Bin发射。时间分辨的荧光测量结果显示双指数衰减，溶剂依赖的寿命分量范围为0.5到1.5 ns和3到5 ns。时间衰减数据与分子力学计算相结合，使我们能够将这些寿命分配给两个左旋3_10螺旋构象异构体，其中发生分子内电子能量从受激Bin转移到TOAC。对于给定的溶剂，两个寿命之间的差异主要取决于构象异构体中两个生色团的不同相对取向，这又与TOAC循环系统的不同褶皱有关。

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