Synchronous Measurement of Ultrafast Anisotropy Decay of the B850 in Bacterial LH2 Complex

• Published in: Chinese physics letters 2015-02, Vol.32 (2), p.48-51
• Main Authors: Wang, Yun-Peng, Du, Lu-Chao, Zhu, Gang-Bei, Wang, Zhuan, Weng, Yu-Xiang
• Format: Article
• Language: English
• Subjects: Anisotropy; Bacteria; Broken symmetry; C2对称性; Coherence; Decay; Excitation; LH2; Rhodobacter sphaeroides; Symmetry; Synchronous; 各向异性; 同步测量; 复合物; 细菌; 腐烂; 衰减动力学
• ISSN: 0256-307X; 1741-3540
• DOI: 10.1088/0256-307X/32/2/023101

Ultrafast anisotropic decay is a prominent parameter revealing ultrafast energy and electron transfer; however, it is dimcult to be determined reliably owing to the requirement of a simultaneous availability of the parallel and perpendieular polarized decay kinetics. Nowadays, any measurement of anisotropic decay is a kind of approach to the exact simultaneity. Here we report a novel method for a synchronous ultrafast anisotropy decay measurement, which can well determine the anisotropy, even at a very early time, as the rising phase of the excitation laser pulse. The anisotropic decay of the B850 in bacteriM light harvesting antenna complex LH2 of rhodobacter sphaeroides in solution at room temperature with coherent excitation is detected by this method, which shows a polarization response time of 30 fs, and the energy transfer from the initial excitation to the bacteriochlorophylls in B850 ring takes about 7Ors. The anisotropic decay that is probed at the red side of the absorption spectrum, such as 880 nm, has an initial value of 0.4, corresponding to simulated emission, while the blue side with an anisotropy of 0.1 contributes to the ground-state bleaching. Our results show that the coherent excitation covering the whole ring might not be realized owing to the symmetry breaking of LH2： from C9 symmetry in membrane to C2 symmetry in solution.