Photosynthetic Bacterial Light-Harvesting Antenna Complexes Adsorbed on Silica Nanoparticles Revealed by Silica Shell-Isolated Au Nanoparticle-Enhanced Raman Spectroscopy
- 化学化工－已发表论文 
Assembling of photosynthetic light-harvesting proteins with inorganic nanoparticles can be a promising strategy for developing artificial solar cells. However, characterization of protein adsorption and its spatial orientation with respect to the interface is still a challenging task. Here we report surface-enhanced Raman spectra of light-harvesting antenna complexes (LH2) from two different photosynthetic bacteria adsorbed onto Au core silica shell (Au@SiO2) nanoparticles to illustrate LH2 adsorption and orientation at the interface. The surface plasmon enhanced Raman spectra of typical vibrational modes of carotenoids are used as the intrinsic reporter of LH2 adsorbed on Au@SiO2. Carotenoid molecules are asymmetrically located inside the disk-like LH2 closest to cytoplasmic side, leading to an orientation-dependent surface-enhanced Raman gain when the LH2 binds to the interface with one of its two end surfaces. We find that the Raman gain factors for LH2 from Rba. sphaeroides are larger than those from Rps. acidophila, suggesting that these two different LH2s adsorbed on the negatively charged silica shell with opposite orientation of their end surfaces carrying opposite charges. This is further supported by the observed difference in the B850 excited-state lifetime change for these two different LH2s when adsorbed onto silica nanoparticles, where the lifetime of B850 acts as an intrinsic reporter for nanoparticle-induced protein deformation which is also orientation-dependent, owing to the asymmetrical location of B850 ring inside the LH2.
CitationJOURNAL OF PHYSICAL CHEMISTRY C,2012,116（12）：6993-6999