Yan M, Manor D, Weng G, Chao H, Rothberg L, Jedju T M, Alfano R R, Callender R H
Institute of Ultrafast Spectroscopy and Lasers, City College of City University, New York, NY 10031.
Proc Natl Acad Sci U S A. 1991 Nov 1;88(21):9809-12. doi: 10.1073/pnas.88.21.9809.
We report on time-resolved absorption studies of the bovine visual pigment rhodopsin with subpicosecond resolution at room temperature. Our data show that bathorhodopsin, rhodopsin's early photoproduct, is photochemically formed in 3.0 +/- 0.7 ps. The data suggest that bathorhodopsin formation is kinetically preceded by two species along the rhodopsin-to-bathorhodopsin reaction coordinate. The first is identified with the vertically excited Franck-Condon state. This decays with an approximately 200-fs lifetime to an intermediate, which then decays to bathorhodopsin in 3.0 ps. We assign this intermediate to be an excited state transient near 90 degrees along the 11-12 torsional coordinate of rhodopsin's chromophore. Exchange of rhodopsin's exchangeable protons for deuterons does not affect the observed dynamics. These observations are both qualitatively and quantitatively consistent with molecular dynamics calculations, which model the rhodopsin to bathorhodopsin phototransition as a cis-trans isomerization along the 11-12 torsional coordinate of rhodopsin's chromophore.
我们报道了在室温下以亚皮秒分辨率对牛视觉色素视紫红质进行的时间分辨吸收研究。我们的数据表明，视紫红质的早期光产物视紫红质中间体在3.0±0.7皮秒内通过光化学方式形成。数据表明，在视紫红质到视紫红质中间体的反应坐标上，视紫红质中间体的形成在动力学上先于两个物种。第一个被确定为垂直激发的弗兰克-康登态。它以约200飞秒的寿命衰减为一个中间体，然后在3.0皮秒内衰减为视紫红质中间体。我们将这个中间体指定为视紫红质发色团11-12扭转坐标上接近90度的激发态瞬态。视紫红质可交换质子与氘核的交换不会影响观察到的动力学。这些观察结果在定性和定量上都与分子动力学计算一致，分子动力学计算将视紫红质到视紫红质中间体的光转变模拟为沿视紫红质发色团11-12扭转坐标的顺反异构化。
