Fluorescence quenching in a strongly helical peptide series: the role of noncovalent pathways in modulating electronic interactions.
Fluorescence quenching in a strongly helical peptide series: the role of noncovalent pathways in modulating electronic interactions.
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强螺旋肽系列中的荧光猝灭：非共价途径在调节电子相互作用中的作用。
DOI：
10.1021/bi00063a018
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发表时间：
1993
期刊：
影响因子：
2.9
通讯作者：
Kuki,A
中科院分区：
文献类型：
--
作者：
Basu,G;Anglos,D;Kuki,A
摘要：富含α-氨基异丁酸（Aib）的肽的非常强的螺旋倾向使得能够设计一组螺旋，所述螺旋包含作为客体氨基酸的一个荧光发色团β-（1 ′-萘基）-L-丙氨酸和一个重原子微扰剂β-溴-L-苯丙氨酸。在这一组中监测的发色残基的荧光探索重原子诱导的增强的系统间交叉作为一个潜在的有用的工具，探索远程电子相互作用的生物分子。该组中的肽是彼此的序列异构体，并且被设计为使得发色团和干扰物被两个、一个或零个Aib残基分开。然后通过螺旋的扭曲来调节芳族侧链之间的相应距离。所有肽均表现出稳态荧光猝灭，并且在进一步的时间分辨三重态-三重态吸收实验的基础上，建立了重原子诱导荧光猝灭的两种机制：（i）弱的和名义上自旋禁戒的单重态-三重态能量转移和（ii）荧光团内系统间交叉的远程重原子效应（RHAE）。单重态-三重态能量转移速率和RHAE在具有最大序列间隔但发色团和扰动物之间的直接距离最小的肽中均处于最大值。因此，两种猝灭机制都不受中间共价途径的长度控制。由插入肽骨架的结构引起的微妙因素显然有助于具有较短序列间隔的肽的RHAE。由于对远程重原子的敏感性是电子离域的量度，因此这一结果可能对理解螺旋在生物电子转移相互作用中的作用具有重要意义。近年来的一些实验研究集中在系统地研究肽系统中两个相互作用伙伴之间的量子电子离域设计成比蛋白质更简单的分子结构。这些弱的电子相互作用跨肽框架导致肽介导的淬灭过程，其定量测量可精确分析单个二级结构元件内的电子相互作用。一个突出的方法依赖于
Revised Manuscript Received January 19, 1993 abstract: The very strong helical propensity of peptides rich in a-aminoisobutyric acid (Aib) has enabled the design of a set of helices containing as guest amino acids one fluorescent chromophore,/3-(l'-naphthyl)-L-alanine, and one heavy atom perturber, p-bromo-L-phenylalanine. The fluorescence of the chromophoric residue was monitored in this set to explore heavy atom induced enhanced intersystem crossing as a potentially useful tool for exploring remote electronic interactions in biomolecules. The peptides in this set were sequence isomers of each other and were designed such that the chromophoreand the perturber were separated by two, one, or zero Aib residues. The respective distances between the aromatic side chains are then modulated by the twist of the helix. All peptides showed steady-state fluorescence quenching, and on the basis of further time-resolved triplet-triplet absorption experiments, two mechanisms for the heavy atom induced fluorescence quenching were established:(i) a weak and nominally spin-forbidden singlet-triplet energy transfer and (ii) the remote heavy atom effect (RHAE) on the intersystem crossing within the fluorophore. Both the rate of singlet-triplet energy-transfer and the RHAE are at their maxima in the peptide with the largest sequence separation but the smallest direct distancebetween the chromophore and the perturber. Thus neither quenching mechanism is controlled by the length of the intervening covalent pathway. Subtle factors arising from the structure of the intervening peptide backbone apparently contribute to the RHAE for the peptides with shorter sequence separation. Because the sensitivity to the remote heavy atom is a measure of electronic delocalization, this result mayhave significance for the understanding of the role of helices in biological electron-transfer interactions.In order to understand the complex nature of long-range electron transfer in proteins, several recent experimental studies have focused on the systematic examination of the quantum electronic delocalization betweentwo interacting partners in peptide systems designed to have simpler molecular architectures than proteins. These weak electronic interactions across the peptide frame lead to peptide-mediated quenching processes whose quantitative measurementenables the precise analysis of electronic interactions within a single secondary structural element. One prominent approach relies upon