Department of Physics, Faculty of Sciences, VU University Amsterdam, Amsterdam, The Netherlands.
Biophys J. 2013 Jun 4;104(11):2493-502. doi: 10.1016/j.bpj.2013.04.026.
A question at the forefront of biophysical sciences is, to what extent do quantum effects and protein conformational changes play a role in processes such as biological sensing and energy conversion? At the heart of photosynthetic energy transduction lie processes involving ultrafast energy and electron transfers among a small number of tetrapyrrole pigments embedded in the interior of a protein. In the purple bacterial reaction center (RC), a highly efficient ultrafast charge separation takes place between a pair of bacteriochlorophylls: an accessory bacteriochlorophyll (B) and bacteriopheophytin (H). In this work, we applied ultrafast spectroscopy in the visible and near-infrared spectral region to Rhodobacter sphaeroides RCs to accurately track the timing of the electron on BA and HA via the appearance of the BA and HA anion bands. We observed an unexpectedly early rise of the HA⁻ band that challenges the accepted simple picture of stepwise electron transfer with 3 ps and 1 ps time constants. The implications for the mechanism of initial charge separation in bacterial RCs are discussed in terms of a possible adiabatic electron transfer step between BA and HA, and the effect of protein conformation on the electron transfer rate.
生物物理科学的前沿问题之一是，量子效应和蛋白质构象变化在生物传感和能量转换等过程中起到了何种程度的作用？光合作用能量转换的核心是涉及少数几个嵌入蛋白质内部的四吡咯色素之间超快能量和电子转移的过程。在紫色细菌反应中心（RC）中，一对细菌叶绿素：辅助细菌叶绿素（B）和细菌叶绿素（H）之间发生高效的超快电荷分离。在这项工作中，我们通过 BA 和 HA 阴离子带的出现，应用可见和近红外光谱区的超快光谱学，准确地跟踪电子在 BA 和 HA 上的时间。我们观察到 HA⁻带的出乎意料的早期上升，这对具有 3 ps 和 1 ps 时间常数的逐步电子转移的公认简单图像提出了挑战。根据 BA 和 HA 之间可能的绝热电子转移步骤以及蛋白质构象对电子转移速率的影响，讨论了细菌 RC 中初始电荷分离机制的意义。
