Nanoparticle induced light-harvesting membrane protein deformation (LH2) revealed by ultrafast spectroscopic study of the excitonic states

PHYS 25

Yu-Xiang Weng, yxweng@aphy.iphy.ac.cn, Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Hai Dian Qu Zhong Guan Cun Nan San Jie 8 Hao, Beijing, 100080, China
We used femto-second time resolved transient absorbance difference spectroscopy to investigate the membrane protein of a light-harvesting antenna complex (LH2) from photosynthetic bacteria Rb. sphaeroides 2.4.1, which consists of two concentric polypeptide cylinders and ringlike pigment aggregate (B850). The deformation of the protein was induced by self-assembly of LH2 onto nanoparticles of different size. The results show that when size of the nanoparticle approaches the diameter of either the inner or the outer polypeptide cylinder, it would induce a largest protein deformation, giving rise to a shorter excited-state life time of B850. This provides a quantitative example of size-matching interaction between the protein and the nanopartilces.