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首页> 外文期刊>The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical >Time. Resolved Fluorescence of Glucagon Studied by Global Compartmental Analysis
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Time. Resolved Fluorescence of Glucagon Studied by Global Compartmental Analysis

机译：时间。全局间隔分析研究胰高血糖素的分辨荧光

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摘要

The photophysics of the polypeptide hormone glucagon in aqueous phosphate buffer (λ↑(eχ) = 295 nm, pH 6.7, 17.2 ℃) in the presence of the added quencher sodium iodide is investigated using standard simultaneous biexponential and global compartmental analyses of its fluorescence decay surface. The use of the scanning procedure in global compartmental analysis allows distinction between reversible and irreversible transformation processes in the excited state (J. Phys. Chem. 1995, 99, 8959-8971). Furthermore, by comparison of the species-associated with the decay-associated emission spectra, a unidirectional process in the excited state can be distinguished from the case where no interconversion occurs between the two excited-state species. Scanning different rate constants and comparing the species-associated with the decay-associated emission spectra indicate that the dual exponential fluorescence decays of the single tryptophan-containing polypeptide glucagon are due to two non-interconverting excited-state species resulting from excitation of their respective ground states. On the time scale of fluorescence there is no interconversion between the two excited-state species. The composite deactivation rate constant values for monomeric glucagon in phosphate buffer (k0a = 1.01× 10↑(9) s↑(-1) and k↓(0.2) = 2.7× 10↑(8) s↑(-1)) are separated into contributions via fluorescence (kFl = 0.05× 10↑(9) S↑(-1) and k↓(F2) = 1.6 × 10↑(8) s↑(-1)) and nonradiative processes (k↓(NR1) = 0.96 × 10↑(9) S↑(-1) and k↓(NR2)= 1.1 × 10↑(8) s-t). The fluorescence quantum yields in the absence of added quencher are φ↑(0)↓(F1) = 0.05 and φ↑(0)↓(F2) = 0.58. The relatively high values (> 1 × 10↑(9)M↑(-1)) of the rate constants of quenching are indicative of a tryptophyl residue exposed to the surrounding aqueous environment. The obtained values of the rate constants may indicate that the decay component of 1 ns is associated with a tryptophyl residue in a flexible extended random coil conformation of the polypeptide chain while its 3.7 ns counterpart corresponds to a tryptophan in a compact, quite rigid backbone conformation. The method used to elucidate the origin of the biexponen-tial fluorescence decays of glucagon is generally applicable to any intramolecular two-state excited-state process and will be useful in the study of peptides and proteins with dual exponential fluorescence decay kinetics.
机译：使用标准的同时双指数和整体隔室分析方法，研究了在添加了猝灭剂碘化钠的条件下，在磷酸盐缓冲液（λ↑（eχ）= 295 nm，pH 6.7，17.2℃）中多肽激素胰高血糖素的光物理性质。表面。在整体区室分析中使用扫描程序可以在激发态下区分可逆和不可逆转化过程（J. Phys。Chem。1995，99，8959-8971）。此外，通过比较与衰变相关的发射光谱相关的种类，可以将激发态下的单向过程与两个激发态种类之间不发生相互转换的情况区分开。扫描不同的速率常数并将物种相关的物种与衰变相关的发射光谱进行比较，表明单个含色氨酸的多肽胰高血糖素的双指数荧光衰变归因于两个非相互转换的激发态物种，它们是由各自的地面激发而产生的状态。在荧光的时间尺度上，两种激发态物质之间没有相互转换。磷酸缓冲液中单体胰高血糖素的复合失活速率常数值为（k0a = 1.01×10↑（9）s↑（-1）和k↓（0.2）= 2.7×10↑（8）s↑（-1））通过荧光（kF1 = 0.05×10↑（9）S↑（-1）和k↓（F2）= 1.6×10↑（8）s↑（-1））和非辐射过程（k↓（NR1） ）= 0.96×10↑（9）S↑（-1）和k↓（NR2）= 1.1×10↑（8）st）。在不添加淬灭剂的情况下，荧光量子产率为Φ↑（0）↓（F1）= 0.05和Φ↑（0）↓（F2）= 0.58。淬灭速率常数的相对较高的值（> 1×10↑（9）M↑（-1））表明色氨酸残基暴露于周围水环境。获得的速率常数值可能表明1 ns的衰减分量与多肽链的柔性延伸随机卷曲构象中的色氨酸残基有关，而其3.7 ns的对应物对应于紧凑，相当刚性的骨架构象中的色氨酸。 。阐明胰高血糖素的双指数荧光衰减的起源的方法通常适用于任何分子内的两态激发态过程，并将用于研究具有双指数荧光衰减动力学的肽和蛋白质。

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