Theiss Christoph, Leupold Dieter, Moskalenko Andrei A, Razjivin Andrei P, Eichler Hans J, Lokstein Heiko
Institut für Optik und Atomare Physik, Technische Universität Berlin, 10623 Berlin, Germany.
Biophys J. 2008 Jun;94(12):4808-11. doi: 10.1529/biophysj.107.121681. Epub 2008 Mar 13.
EET between the two circular bacteriochlorophyll compartments B800 and B850 in native (containing the carotenoid rhodopin) and carotenoidless LH2 isolated from the photosynthetic purple sulfur bacterium Allochromatium minutissimum was investigated by femtosecond time-resolved transient absorption spectroscopy. Both samples were excited with 120-fs laser pulses at 800 nm, and spectral evolution was followed in the 720-955 nm range at different delay times. No dependence of transient absorption in the B800 band on the presence of the carotenoid rhodopin was found. Together with the likewise virtually unchanged absorption spectra in the bacteriochlorophyll Q(y) region, these observations suggest that absence of rhodopin does not significantly alter the structure of the pigment-protein complex including interactions between bacteriochlorophylls. Apparently, rhodopin does also not accelerate B800 to B850 EET in LH2, contrary to what has been suggested previously. Moreover, "carotenoid-catalyzed internal conversion" can also be excluded for the bacteriochlorophylls in LH2 of A. minutissimum. Together with previous results obtained with two-photon fluorescence excitation spectroscopy, it can also be concluded that there is neither EET from rhodopin to B800 nor (back-)EET from B800 to rhodopin.
利用飞秒时间分辨瞬态吸收光谱法，研究了从极小嗜硫光合紫细菌中分离出的天然（含有类胡萝卜素玫红菌红素）和无类胡萝卜素的LH2中，两个环状细菌叶绿素区室B800和B850之间的激子能量转移（EET）。两个样品均用800 nm的120飞秒激光脉冲激发，并在720 - 955 nm范围内不同延迟时间跟踪光谱演化。未发现B800波段的瞬态吸收对类胡萝卜素玫红菌红素的存在有依赖性。连同细菌叶绿素Q(y)区域中同样几乎未改变的吸收光谱，这些观察结果表明，玫红菌红素的缺失不会显著改变色素 - 蛋白质复合物的结构，包括细菌叶绿素之间的相互作用。显然，与之前的推测相反，玫红菌红素在LH2中也不会加速B800到B850的EET。此外，极小嗜硫光合紫细菌LH2中的细菌叶绿素也可以排除“类胡萝卜素催化的内转换”。连同先前用双光子荧光激发光谱法获得的结果，还可以得出结论，既不存在从玫红菌红素到B800的EET，也不存在从B800到玫红菌红素的（反向）EET。
