Yakovlev Andrei G, Shkuropatov Anatoli Ya, Shuvalov Vladimir A
Department of Photobiophysics, Belozersky Institute of Chemical and Physical Biology of Moscow State University, Moscow 119899, Russia.
Biochemistry. 2002 Feb 26;41(8):2667-74. doi: 10.1021/bi0101244.
Formation and coherent propagation of nuclear wavepackets on potential energy surfaces of the excited state of the primary electron donor P and of the charge transfer states P(+)B(A)(-) and P(+)H(A)(-) were studied in native and pheophytin-modified Rhodobacter sphaeroides R-26 reaction centers (RCs) induced by 25 fs excitation (where B(A) and H(A) are the primary and secondary electron acceptors, respectively). The processes were monitored by measuring coherent oscillations in kinetics of the time evolution of the stimulated emission band of P at 935 nm, of the absorption band of B(A)(-) at 1020 nm, and of the bleaching band of H(A) at 760 nm. It was found that the nuclear wavepacket motion on the 130-140 cm(-1) surface of P is directly induced by light absorption in P. When the wavepacket approaches the intersection between P and P(+)B(A)(-) surfaces at 120 and 380 fs delays, the formation of intermediate mixed-state emitting light at 935 nm (P) and absorbing light at 1020 nm (P(+)B(A)(-)) takes place. At the latter time, the wavepacket is transferred to the 32 cm(-1) mode which can belong to the P hypersurface effectively transferring the wavepacket to the P(+)B(A)(-) surface or can represent a diabatic surface which is formed by the states P and P(+)B(A)(-). The wavepacket motion on the P(+)B(A)(-) surface or on the P(+)B(A)(-) part of the mixing surface is accompanied by irreversible electron transfer to H(A). This process is monitored by the kinetics of 1020 nm band development and 760 nm band bleaching (delayed with respect to 1020 nm band development) which both have the enhanced 32 cm(-1) mode in Fourier transform (FT) spectra. The mechanism of wavepacket transfer from the 130-140 cm(-1) to the 32 cm(-1) mode is discussed.
研究了在25飞秒激发下,天然的和脱镁叶绿素修饰的球形红细菌R-26反应中心(RCs)中,初级电子供体P的激发态以及电荷转移态P(+)B(A)(-)和P(+)H(A)(-)的势能面上核波包的形成及相干传播(其中B(A)和H(A)分别是初级和次级电子受体)。通过测量935nm处P的受激发射带、1020nm处B(A)(-)的吸收带以及760nm处H(A)的漂白带随时间演化动力学中的相干振荡来监测这些过程。研究发现,P的130 - 140cm(-1)表面上的核波包运动是由P中的光吸收直接诱导的。当波包在120和380飞秒延迟时接近P和P(+)B(A)(-)表面的交点时,会形成在935nm处发射光(P)且在1020nm处吸收光(P(+)B(A)(-))的中间混合态。在较晚时刻,波包转移到32cm(-1)模式,该模式可能属于P超曲面从而有效地将波包转移到P(+)B(A)(-)表面,或者可能代表由P和P(+)B(A)(-)态形成的非绝热表面。P(+)B(A)(-)表面或混合表面的P(+)B(A)(-)部分上的波包运动伴随着向H(A)的不可逆电子转移。这个过程通过1020nm带的发展动力学和760nm带的漂白(相对于1020nm带的发展有延迟)来监测,这两者在傅里叶变换(FT)光谱中都有增强的32cm(-1)模式。讨论了波包从130 - 140cm(-1)模式转移到32cm(-1)模式的机制。