Insensitivity of tryptophan fluorescence to local charge mutations.
Insensitivity of tryptophan fluorescence to local charge mutations.
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色氨酸荧光对局部电荷突变不敏感。
DOI：
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发表时间：
2013
影响因子：
3.3
通讯作者：
P. Callis
中科院分区：
文献类型：
--
作者：
J. N. Scott;P. Callis
金黄色葡萄球菌核酸酶色氨酸140的稳态荧光光谱最大值(λmax)在附近的带电基团被突变去除后基本保持不变，即使可能会对λmax产生很大的静电影响。为了帮助理解这一奇怪结果的潜在机制，我们用三组50 ns的分子动力学模拟对λ最大值进行了建模，这些模拟在显性水中进行，与激发态和基态电荷平衡。利用模拟得到的坐标，对野生型蛋白质和四个电荷改变突变体进行了半经验量子力学和独立的静电分析。附近带电的赖氨酸本身的静电贡献相对于气相贡献了30-90 nm的红移，但在每种情况下，水的贡献都产生了补偿性的蓝移，使预测的λ最大值在实验值的2 nm以内，对于所有五种蛋白质来说，都是332±0.5 nm。尽管有序水的长程集体相互作用会产生很大的蓝移，这对确定吸收和荧光的稳态λ最大值至关重要，但这种蓝移不会对激发后依赖时间的斯托克斯移动的幅度做出贡献，这种蓝移来自附近的电荷，并且只有∼6水域与这些电荷紧密相连。因此，我们得出结论，对于STNase，水和蛋白质对斯托克斯位移的影响是不可分的。
The steady state fluorescence spectral maximum (λmax) for tryptophan 140 of Staphylococcal nuclease remains virtually unchanged when nearby charged groups are removed by mutation, even though large electrostatic effects on λmax might be expected. To help understand the underlying mechanism of this curious result, we have modeled λmax with three sets of 50-ns molecular dynamics simulations in explicit water, equilibrated with excited state and with ground state charges. Semiempirical quantum mechanics and independent electrostatic analysis for the wild-type protein and four charge-altering mutants were performed on the chromophore using the coordinates from the simulations. Electrostatic contributions from the nearby charged lysines by themselves contribute 30-90 nm red shifts relative to the gas phase, but in each case, contributions from water create compensating blue shifts that bring the predicted λmax within 2 nm of the experimental value, 332 ± 0.5 nm for all five proteins. Although long-range collective interactions from ordered water make large blue shifts, crucial for determining the steady state λmax for absorption and fluorescence, such blue shifts do not contribute to the amplitude of the time dependent Stokes shift following excitation, which comes from nearby charges and only ∼6 waters tightly networked with those charges. We therefore conclude that for STNase, water and protein effects on the Stokes shift are not separable.
影响因子：
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作者：
P. Callis
通讯作者：
P. Callis
影响因子：
3.3
作者：
Golosov, Andrei A.;Karplus, Martin
通讯作者：
Karplus, Martin
DOI：
10.1021/jp104425t
发表时间：
2010-09
期刊：
The journal of physical chemistry. B
影响因子：
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作者：
D. Toptygin;T. Woolf;L. Brand
通讯作者：
D. Toptygin;T. Woolf;L. Brand