对菌紫质(Bacteriorhodopsin, BR)薄膜的光致各向异性特性进行了理论模拟。由随机取向的极性BR分子构成的聚合物薄膜在宏观上是各向同性的,但在线偏振光的作用下,BR分子对激发光的选择性吸收,导致不同异构体分子取向的不均匀分布,从而使BR薄膜在宏观上呈现出各向异性。利用BR光循环的二能级模型,得到了B态分子取向分布随时间的变化关系,推导出了BR薄膜光致各向异性动力学的数学表达式,模拟了不同激发光强下BR薄膜的光致各向异性动力学曲线,得到了和实验结果一致的计算结果。

The polymeric film embedded with polar bacteriorhodopsin (BR) molecules is isotropic in macroscopy since the BR molecules are randomly distributed. Upon excitation by a linearly polarized light, selective absorption of BR molecules with respect to the polarization orientation of the excitation light makes the nonuniformly distributed orientation of BR molecules, resulting in a macroscopic anisotropy. According to the two-state model of BR photocycle, the time-dependent orientation distribution of BR molecules in B state is obtained. The kinetic equations of the photoinduced anisotropy of the BR-film are derived. The kinetic curves of the photoinduced anisotropy at different intensities of excitation light are simulated, which are consistent with experimental results.