Fluorescence quenching of dyes by tryptophan: Interactions at atomic detail from combination of experiment and computer simulation
Fluorescence quenching of dyes by tryptophan: Interactions at atomic detail from combination of experiment and computer simulation
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DOI：
10.1021/ja036082j
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发表时间：
2003-11-26
影响因子：
15
通讯作者：
Smith, JC
中科院分区：
文献类型：
--
作者：
Vaiana, AC;Neuweiler, H;Smith, JC
结合荧光光谱和分子动力学（MD）模拟表征了两种有机荧光染料罗丹明6G （R6G）和一种噻嗪衍生物MR121与水溶液中氨基酸色氨酸的相互作用。稳态和时间分辨荧光猝灭实验揭示了基本非荧光基态染料/色氨酸配合物的形成。MD模拟用于阐明分子相互作用的几何形状。由md导出的染料和猝灭环体系几何中心之间距离r的概率分布P(r)， R6G比MR121延伸到更高的距离，这是由于在R6G/色氨酸体系中色氨酸与染料的苯基环和酯基之间的荧光相互作用几何分布。这样做的结果是实验发现，在模拟中使用的条件下，大约25%的R6G染料是荧光的，而MR121只有10%。结合上述结果可以确定“淬火距离”r*，在此距离以上不发生淬火。发现两种染料/色色剂体系的r*非常相似（类似于5.5埃），对应于接近范德华接触。实验动态Stern-Volmer分析和MD轨迹都表明，静态猝灭是荧光强度的主要决定因素。提出的方法可能是有用的结构解释数据从荧光偶联物通常用于监测生物分子系统的结合和动力学。
Fluorescence spectroscopy and molecular dynamics (MD) simulation are combined to characterize the interaction of two organic fluorescent dyes, rhodamine 6G (R6G) and an oxazine derivative (MR121), with the amino acid tryptophan in aqueous solution. Steady-state and time-resolved fluorescence quenching experiments reveal the formation of essentially nonfluorescent ground-state dye/Trp complexes. The MD simulations are used to elucidate the molecular interaction geometries involved. The MD-derived probability distribution of the distance r between the centers of geometry of the dye and quencher ring systems, P(r), extends to higher distances for R6G than for MR121 due to population in the R6G/Trp system of fluorescent interaction geometries between Trp and the phenyl ring and ester group of the dye. The consequence of this is the experimental finding that under the conditions used in the simulations about 25% of the R6G dye is fluorescent in comparison with 10% of the MR121. Combining the above findings allows determination of the "quenching distance", r*, above which no quenching occurs. r* is found to be very similar (similar to5.5 Angstrom) for both dye/Trp systems, corresponding to close to van der Waals contact. Both experimental dynamic Stern-Volmer analysis and the MD trajectories demonstrate that the main determinant of the fluorescence intensity is static quenching. The approach presented is likely to be useful in the structural interpretation of data obtained from fluorescent conjugates commonly used for monitoring the binding and dynamics of biomolecular systems.