Ansari A, Szabo A
Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892.
Biophys J. 1993 Mar;64(3):838-51. doi: 10.1016/S0006-3495(93)81445-0.
The theory of absorbance measurements on a system (e.g., chromophore(s) in a protein) that undergoes a sequence of reactions initiated by a linearly polarized light pulse is developed for excitation pulses of arbitrary intensity. This formalism is based on a set of master equations describing the time evolution of the orientational distribution function of the various species resulting from excitation, reorientational dynamics, and chemical kinetics. For intense but short excitation pulses, the changes in absorbance (for arbitrary polarization directions of the excitation and probe pulses) and the absorption anisotropy are expressed in terms of reorientational correlation functions. The influence of the internal motions of the chromophore as well as the overall motions of the molecules is considered. When the duration of the excitation pulse is long compared to the time-scale of internal motions but comparable to the overall correlation time of the molecule that is reorienting isotropically, the problem of calculating the changes in absorbance is reduced to the solution of a set of first-order coupled differential equations. Emphasis is placed on obtaining explicit results for quantities that are measured in photolysis and fluorescence experiments so as to facilitate the analysis of experimental data.
针对由线偏振光脉冲引发一系列反应的系统（例如蛋白质中的发色团），我们发展了关于任意强度激发脉冲的吸光度测量理论。这种形式体系基于一组主方程，这些主方程描述了由激发、重取向动力学和化学动力学所产生的各种物质的取向分布函数随时间的演化。对于强而短的激发脉冲，吸光度的变化（对于激发脉冲和探测脉冲的任意偏振方向）以及吸收各向异性是根据重取向相关函数来表示的。我们考虑了发色团的内部运动以及分子的整体运动的影响。当激发脉冲的持续时间相比于内部运动的时间尺度较长，但与各向同性重取向的分子的整体相关时间相当，计算吸光度变化的问题就简化为一组一阶耦合微分方程的求解。重点在于获得光解和荧光实验中所测量量的明确结果，以便于对实验数据进行分析。
