ABSTRACT
Bacterial photosynthetic membrane proteins, light-harvesting antenna complex (LH1), reaction center (RC), and their combined 'core' complex (LH1-RC) are functional elements in the primary photosynthetic events, i.e., capturing and transferring light energy and subsequent charge separation. These photosynthetic units (PSUs) isolated from Rhodospirillum rubrum (Rs. rubrum) were assembled onto an ITO electrode modified with 3-aminopropyltriethoxysilane (APS-ITO). The near IR absorption spectra of PSUs on the assembled electrodes were identical to those of solutions, indicating that the LH1 and LH1-RC core complexes were native on the electrode. Photocurrent response of PSUs on the electrode was examined upon illumination of the LH1 complex at 880 nm. The LH1-RC and a mixed assembly of LH1 and RC exhibited photocurrent response, but not LH1 only, consistent with the function of these PSUs, capturing light energy and transferring electron. This result provides useful methodology for building an artificial fabrication of PSUs on the electrode.
Subject(s)
Photosynthetic Reaction Center Complex Proteins/metabolism , Tin Compounds/chemistry , Cell Membrane/chemistry , Electrodes , Light-Harvesting Protein Complexes/chemistry , Light-Harvesting Protein Complexes/isolation & purification , Models, Biological , Photosynthetic Reaction Center Complex Proteins/chemistry , Photosynthetic Reaction Center Complex Proteins/isolation & purification , Propylamines , Rhodospirillum rubrum/cytology , Rhodospirillum rubrum/metabolism , Silanes/chemistry , Spectrophotometry, InfraredABSTRACT
Light-harvesting antenna core (LH1-RC) complexes isolated from Rhodospirillum rubrum and Rhodopseudomonas palustris were successfully self-assembled on an ITO electrode modified with 3-aminopropyltriethoxysilane. Near infra-red (NIR) absorption, fluorescence, and IR spectra of these LH1-RC complexes indicated that these LH1-RC complexes on the electrode were stable on the electrode. An efficient energy transfer and photocurrent responses of these LH1-RC complexes on the electrode were observed upon illumination of the LH1 complex at 880 nm.
Subject(s)
Bacterial Proteins/metabolism , Light-Harvesting Protein Complexes/metabolism , Bacterial Proteins/chemistry , Electrochemistry/methods , Electrodes , Light-Harvesting Protein Complexes/chemistry , Photosynthesis , Rhodopseudomonas/metabolism , Rhodospirillum rubrum/metabolism , Spectroscopy, Fourier Transform InfraredABSTRACT
The subunit light-harvesting 1 (LH 1) complexes isolated from photosynthetic bacteria Rhodospirillum rubrum using n-octyl-beta-glucoside were reassociated and adsorbed on a mica substrate using spin-coat methods with the aim of using this LH complex in a nanodevice. The near-IR absorption and fluorescence spectra of the LH 1 complexes indicated that the LH 1 complex on the mica was stable, and efficient energy transfer from a carotenoid to a bacteriochlorophyll a was observed. Atomic force microscopy of the reassociated LH 1 complexes, under air, showed the expected ringlike structure. The outer and inner diameters of the ringlike structure of the LH 1 complex were approximately 30 and 8 nm, respectively, and the ringlike structure protruded by 0.2-0.6 nm.
