Pandit Anjali, van Stokkum Ivo H M, Georgakopoulou Sofia, van der Zwan Gert, van Grondelle Rienk
Faculty of Earth and Life Sciences and Division of Physics and Astronomy, Department of Structural Biology, The Netherlands,
Photosynth Res. 2003;75(3):235-48. doi: 10.1023/A:1023988722299.
We investigated the temperature-mediated reassociation of the B820 subunit of Rs. rubrum to form a light-harvesting 1 complex (LH 1). By combining several spectroscopic techniques with global spectral data analysis fitting, we present evidence for the occurence of two spectral intermediates that appear during the reassociation process. At high temperatures, halfway the reassociation reaction, a prominent intermediate appears that has an absorption maximum around 850 nm, a fluorescence maximum around 860-867 nm, a high anisotropy (0.3 to 0.4) and a circular dichroism spectrum with three or four bands with alternating signs. At lower temperatures, more towards the end of the reassociation process, a second intermediate tends to appear that has an absorption maximum around 860 nm, a fluorescence maximum around 885 nm, a medium to high anisotropy (0.1 to 0.3) and a circular dichroism spectrum with two bands with alternating signs. The latter circular dichroism spectrum has a blueshifted zero-crossing compared to the spectrum of the LH 1 complex. Both intermediates have the spectroscopic features of a small oligomer. In the Q(y) region, the fluorescence anisotropy of both intermediates slightly increases at longer excitation wavelengths, indicative for energy transfer among the pigments within the intermediate oligomers.
我们研究了深红螺菌（Rs. rubrum）的B820亚基通过温度介导重新缔合形成捕光1复合体（LH 1）的过程。通过将多种光谱技术与全局光谱数据分析拟合相结合，我们提供了证据，证明在重新缔合过程中出现了两种光谱中间体。在高温下，重新缔合反应进行到一半时，会出现一个突出的中间体，其吸收峰在850 nm左右，荧光峰在860 - 867 nm左右，具有较高的各向异性（0.3至0.4），并且圆二色光谱有三或四个带，正负交替。在较低温度下，更接近重新缔合过程结束时，会出现第二个中间体，其吸收峰在860 nm左右，荧光峰在885 nm左右，具有中等至高的各向异性（0.1至0.3），并且圆二色光谱有两个带，正负交替。与LH 1复合体的光谱相比，后一种圆二色光谱的零交叉发生了蓝移。两种中间体都具有小分子寡聚体的光谱特征。在Q(y)区域，两种中间体的荧光各向异性在较长激发波长下略有增加，这表明中间体寡聚体内的色素之间存在能量转移。
