Peloquin J M, Violette C A, Frank H A, Bocian D F
Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213.
Biochemistry. 1990 May 22;29(20):4892-8. doi: 10.1021/bi00472a020.
Resonance Raman (RR) spectra are reported for the photosynthetic reaction center (RC) protein from Rhodobacter sphaeroides 2.4.1. The spectra were obtained with a variety of excitation wavelengths, spanning the UV, violet, and yellow-green regions of the absorption spectrum, and at a number of temperatures ranging from 30 to 270 K. The RR data indicate that the frequencies of certain vibrational modes of the bacteriochlorin pigments in the RC shift with temperature. These shifts are reversible and do not depend on external factors such as solvent or detergent. The acetyl carbonyl bands exhibit the largest shifts with temperature. These shifts are attributed to thermal effects involving the torsional vibrations of the acetyl groups of several (or all) of the bacteriochlorins rather than to specific pigment-protein interactions. The frequency of the structure-sensitive skeletal mode near 1610 cm-1 of one of the two bacteriopheophytins (BPhs) in the RC is also sensitive to temperature. In contrast, no temperature sensitivity is observed for the analogous modes of the bacteriochlorophylls or other BPhs. Over the range 160-100 K, the skeletal mode of the BPh upshifts by approximately 4 cm-1. This upshift is attributed to a flattening of the macrocycle at low temperatures. It is suggested that the BPh active in the electron-transfer process is the pigment whose structure is temperature dependent. It is further suggested that such structural changes could be responsible in part for the temperature dependence of the electron-transfer rates in photosynthetic RCs.
报道了球形红细菌2.4.1光合反应中心（RC）蛋白的共振拉曼（RR）光谱。这些光谱是在多种激发波长下获得的，涵盖了吸收光谱的紫外、紫光和黄绿色区域，并且在30至270 K的多个温度下测量。RR数据表明，RC中细菌叶绿素色素某些振动模式的频率随温度发生变化。这些变化是可逆的，且不依赖于溶剂或去污剂等外部因素。乙酰羰基谱带随温度的变化最大。这些变化归因于涉及几种（或所有）细菌叶绿素乙酰基扭转振动的热效应，而非特定的色素 - 蛋白质相互作用。RC中两种细菌脱镁叶绿素（BPhs）之一在1610 cm-1附近的结构敏感骨架模式的频率也对温度敏感。相比之下，未观察到细菌叶绿素或其他BPhs类似模式的温度敏感性。在160 - 100 K范围内，BPh的骨架模式向上移动约4 cm-1。这种上移归因于低温下大环的扁平化。有人认为，在电子转移过程中起作用的BPh是其结构依赖于温度的色素。进一步表明，这种结构变化可能部分导致光合RC中电子转移速率的温度依赖性。
