Femtosecond stimulated Raman spectroscopy of flavin after optical excitation.
Femtosecond stimulated Raman spectroscopy of flavin after optical excitation.
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光激发后黄素的飞秒受激拉曼光谱。
DOI：
10.1021/jp1117129
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发表时间：
2011
期刊：
影响因子：
--
通讯作者：
N. Ernsting
中科院分区：
文献类型：
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作者：
Alexander Weigel;A. Dobryakov;Bastian Klaumünzer;Mohsen Sajadi;P. Saalfrank;N. Ernsting
在黄素蓝光感受器(BLUF)中，在光照后的几个100ps内就已经形成了信号状态，吸收光谱只有很小的变化。原则上，可以用飞秒受激拉曼光谱(FSRs)来监测伴随的结构演变。用该方法表征了核黄素和黄素腺嘌呤二核苷酸在极性溶剂中的激发态性质。对电子基态S(0)和激发到S(1)态，在90-1800厘米(-1)范围内观察到拉曼模，并用量子化学计算指定了这两种态的拉曼模。结果表明，线条形状对共振条件有很大的影响。它们受到任何参与电子态的波包运动的影响，导致受激拉曼光谱的复杂幅度调制。S(1)中的波包可以通过皮秒拉曼脉冲的受激发射泵浦来标记和隔离。通过对宽带瞬时荧光和吸收的定量比较，得到了激发态吸收光谱。通过这种方法，确定了FSR的共振条件。发射光谱的早期差异取决于过剩的振动能，溶剂化被视为发射带的动态斯托克斯位移。只有通过溶剂化过程中发射振子强度的变化才能证明nπ*态。S(1)腺嘌呤猝灭是从动力学的角度用各种方法观察到的，而不是光谱中间体。
In blue-light photoreceptors using flavin (BLUF), the signaling state is formed already within several 100 ps after illumination, with only small changes of the absorption spectrum. The accompanying structural evolution can, in principle, be monitored by femtosecond stimulated Raman spectroscopy (FSRS). The method is used here to characterize the excited-state properties of riboflavin and flavin adenine dinucleotide in polar solvents. Raman modes are observed in the range 90-1800 cm(-1) for the electronic ground state S(0) and upon excitation to the S(1) state, and modes >1000 cm(-1) of both states are assigned with the help of quantum-chemical calculations. Line shapes are shown to depend sensitively on resonance conditions. They are affected by wavepacket motion in any of the participating electronic states, resulting in complex amplitude modulation of the stimulated Raman spectra. Wavepackets in S(1) can be marked, and thus isolated, by stimulated-emission pumping with the picosecond Raman pulses. Excited-state absorption spectra are obtained from a quantitative comparison of broadband transient fluorescence and absorption. In this way, the resonance conditions for FSRS are determined. Early differences of the emission spectrum depend on excess vibrational energy, and solvation is seen as dynamic Stokes shift of the emission band. The nπ* state is evidenced only through changes of emission oscillator strength during solvation. S(1) quenching by adenine is seen with all methods in terms of dynamics, not by spectral intermediates.