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Femtosecond Fluorescence Spectra of NADH in Solution: Ultrafast Solvation Dynamics.
The Journal of Physical Chemistry B ( IF 2.8 ) Pub Date : 2020-01-15 , DOI: 10.1021/acs.jpcb.9b10656 Simin Cao 1 , Haoyang Li 1 , Yangyi Liu 1 , Mengjie Zhang 1 , Mengyu Wang 1 , Zhongneng Zhou 1 , Jinquan Chen 1 , Sanjun Zhang 1 , Jianhua Xu 1 , Jay R Knutson 2
The Journal of Physical Chemistry B ( IF 2.8 ) Pub Date : 2020-01-15 , DOI: 10.1021/acs.jpcb.9b10656 Simin Cao 1 , Haoyang Li 1 , Yangyi Liu 1 , Mengjie Zhang 1 , Mengyu Wang 1 , Zhongneng Zhou 1 , Jinquan Chen 1 , Sanjun Zhang 1 , Jianhua Xu 1 , Jay R Knutson 2
Affiliation
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The ultrafast solvation dynamics of reduced nicotinamide adenine dinucleotide (NADH) free in solution has been investigated, using both a femtosecond upconversion spectrophotofluorometer and a picosecond time-correlated single-photon counting (TCSPC) apparatus. The familiar time constant of solvent relaxation originating in "bulk water" was found to be ∼1.4 ps, revealing ultrafast solvent reorientation upon excitation. We also found a slower spectral relaxation process with an apparent time of 27 ps, suggesting there could either be dissociable "biological water" hydration sites on the surface of NADH or internal dielectric rearrangements of the flexible solvated molecule on that timescale. In contrast, the femtosecond fluorescence anisotropy measurement revealed that rotational diffusion happened on two different timescales (3.6 ps (local) and 141 ps (tumbling)); thus, any dielectric rearrangement scenario for the 27 ps relaxation must occur without significant chromophore oscillator rotation. The coexistence of quasi-static self quenching (QSSQ) with the slower relaxation is also discussed.
中文翻译：
溶液中 NADH 的飞秒荧光光谱：超快溶剂化动力学。
使用飞秒上转换荧光分光光度计和皮秒时间相关单光子计数 (TCSPC) 装置研究了溶液中游离的还原型烟酰胺腺嘌呤二核苷酸 (NADH) 的超快溶剂化动力学。发现源自“大量水”的常见溶剂弛豫时间常数为~1.4 ps，揭示了激发后溶剂的超快重新取向。我们还发现了较慢的光谱弛豫过程，表观时间为 27 ps，这表明 NADH 表面可能存在可解离的“生物水”水合位点，或者在该时间尺度上柔性溶剂化分子的内部介电重排。相比之下，飞秒荧光各向异性测量表明旋转扩散发生在两个不同的时间尺度（3.6 ps（局部）和141 ps（翻滚））；因此，任何 27 ps 弛豫的介电重排情况都必须在没有显着发色团振荡器旋转的情况下发生。还讨论了准静态自猝灭（QSSQ）与较慢弛豫的共存。
更新日期：2020-01-26
中文翻译：
溶液中 NADH 的飞秒荧光光谱：超快溶剂化动力学。
使用飞秒上转换荧光分光光度计和皮秒时间相关单光子计数 (TCSPC) 装置研究了溶液中游离的还原型烟酰胺腺嘌呤二核苷酸 (NADH) 的超快溶剂化动力学。发现源自“大量水”的常见溶剂弛豫时间常数为~1.4 ps，揭示了激发后溶剂的超快重新取向。我们还发现了较慢的光谱弛豫过程，表观时间为 27 ps，这表明 NADH 表面可能存在可解离的“生物水”水合位点，或者在该时间尺度上柔性溶剂化分子的内部介电重排。相比之下，飞秒荧光各向异性测量表明旋转扩散发生在两个不同的时间尺度（3.6 ps（局部）和141 ps（翻滚））；因此，任何 27 ps 弛豫的介电重排情况都必须在没有显着发色团振荡器旋转的情况下发生。还讨论了准静态自猝灭（QSSQ）与较慢弛豫的共存。
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