Tonouchi Noriyuki, Kosumi Daisuke, Sugisaki Mitsuru, Nango Mamoru, Hashimoto Hideki
Department of Physics, Graduate School of Science, Osaka City University, Sugimoto, Sumiyoshi, Osaka, 558-8585, Japan.
Photosynth Res. 2015 Apr;124(1):77-86. doi: 10.1007/s11120-015-0095-z. Epub 2015 Feb 14.
Absorption and Raman spectra of spheroidene dissolved in various organic solvents and bound to peripheral light-harvesting LH2 complexes from photosynthetic purple bacteria Rhodobacter (Rba.) sphaeroides 2.4.1 were measured. The results showed that the peak energies of absorption and C-C and C=C stretching Raman lines are linearly proportional to the polarizability of solvents, as has already been reported. When comparing these results with those measured on LH2 complexes, it was confirmed that spheroidene is surrounded by a media with high polarizability. However, the change in the spectral width of the Raman lines, which reflect vibrational decay time, cannot be explained simply by a similar dependence of solvent polarizability. The experimental results were analyzed using a potential theoretical model. Consequently, a systematic change in the Raman line widths in the ground state can be satisfactorily explained as a function of the viscosity of the surrounding media. Even when the absorption peaks appear at the same energy, the vibrational decay time of spheroidene in the LH2 complexes is approximately 15-20 % slower than that in organic solvents.
测量了溶解于各种有机溶剂中并与光合紫色细菌球形红杆菌（Rba.）sphaeroides 2.4.1的外周光捕获LH2复合物结合的球烯的吸收光谱和拉曼光谱。结果表明，吸收峰能量以及C-C和C = C伸缩拉曼谱线与溶剂的极化率呈线性比例关系，这与之前报道的一致。将这些结果与在LH2复合物上测量的结果进行比较时，证实球烯被具有高极化率的介质所包围。然而，反映振动衰减时间的拉曼谱线宽度的变化不能简单地用溶剂极化率的类似依赖性来解释。使用一个潜在的理论模型对实验结果进行了分析。因此，基态拉曼谱线宽度的系统变化可以作为周围介质粘度的函数得到令人满意的解释。即使吸收峰出现在相同能量处，球烯在LH2复合物中的振动衰减时间也比在有机溶剂中慢约15 - 20％。
