Spectrally silent transitions in the bacteriorhodopsin photocycle
Spectrally silent transitions in the bacteriorhodopsin photocycle
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DOI：
10.1016/s0006-3495(96)79475-4
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发表时间：
1996-11-01
影响因子：
3.4
通讯作者：
Hess, B
中科院分区：
文献类型：
--
作者：
Chizhov, I;Chernavskii, DS;Hess, B
在101个波长（330-730 nm）下从0至40 ℃分析细菌视紫红质的光循环动力学。数据可以满意地近似为八个指数。最慢的组分（在20摄氏度下的半衰期为20毫秒）属于13顺式循环。剩余的七个指数足以描述全反式光循环表明，至少有七个中间体的全反式循环必须存在，虽然只有五个光谱不同的物种（K，L，M，N和O）已被确定。这七个指数和它们在不同温度下的光谱为讨论各种弛豫动力学方案提供了基础。不可逆连续跃迁的最简单模型包括在第一个K →> L步骤之后LM、MN和NO中间体的准平衡。这些准平衡由蛋白质和/或发色团区域外的质子转移步骤的限速动力学控制。因此，存在一个明显的动力学悖论（即，为什么弛豫指数的数目（至少七个）高于不同光谱中间体的数目（仅五个）），这可以通过假设一些跃迁对应于光谱上不同的中间体之间的准平衡的变化来解释（即，是无声的幽灵）。
The photocycle kinetics of bacteriorhodopsin were analyzed from 0 to 40 degrees C at 101 wavelengths (330-730 nm). The data can be satisfactorily approximated by eight exponents. The slowest component (half-time 20 ms at 20 degrees C) belongs to the 13-cis cycle. The residual seven exponentials that are sufficient to describe the all-trans photocycle indicate that at least seven intermediates of the all-trans cycle must exist, although only five spectrally distinct species (K, L, M, N, and O) have been identified. These seven exponentials and their spectra at different temperatures provide the basis for the discussion of various kinetic schemes of the relaxation. The simplest model of irreversible sequential transitions includes after the first K --> L step the quasiequilibria of LM, MN, and NO intermediates. These quasiequilibria are controlled by rate-limiting dynamics of the protein and/or proton transfer steps outside the chromophore region. Thus there exists an apparent kinetic paradox (i.e., why is the number of exponents of relaxation (at least seven) higher than the number of distinct spectral intermediates (only five)), which can be explained by assuming that some of the transitions correspond to changes in the quasiequilibria between spectrally distinct intermediates (i.e., are spectrally silent).