Fluorescence of Two-dimensional Patterned Photosynthetic Proteins onto Gold surface
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Fluorescence of Two-dimensional Patterned Photosynthetic Proteins onto Gold surface Rei A. Furukawa1, Shunsuke Yajima2, Shinji Nozaki1, Takehisa Dewa2 and Mamoru Nango3 1 The University of Electro-communications, 1-5-1 Chofugaoka, Tokyo, 182-8585 Japan. 2 Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya, 466-8555 Japan. 3 Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka, 558-8585 Japan. ABSTRACT Photosynthetic membrane proteins convert solar light into chemical energy in a significantly high efficiency. Up-to-date reports of the photosynthetic bacterium suggest that such effective light conversion is due to the energy transfer between two light-harvesting (LH) protein complexes that are patterned in two dimensions. In this report, LH complex isolated from Rb. sphaeroides was immobilized onto a patterned gold surface with self-assembled monolayers (SAMs) and lipid bilayers at two main objectives: (1) micron-scale patterning of LH complex, and (2) prevention of quenching for pattern observation. INTRODUCTION Photosynthetic membrane proteins convert solar light into chemical energy efficiently. When light energy is absorbed in vivo by purple bacterial light-harvesting (LH) complexes, it is rapidly transferred to the reaction centers (RC) where light energy is efficiently converted into useful chemical energy[1]. In most types of purple photosynthetic bacteria, there are two types of antenna complexes: peripheral LH2 complexes and the LH1 complexes. The structure of the LH2 complex of Rhodopseudomonas acidophila strain 10050 has been resolved to a resolution of 2.0 Å[2]. This LH2 complex consists of a ring of nine heterodimeric subunits. Our current understanding of energy transfer and charge separation reactions in the LH2 and LH1-RC complexes has enabled the first step to be taken toward generating from them artificial systems that convert light energy into usable electrical current. Previous attempts to produce an artificial energy converting electrode system used either the LH1 complexes or RC immobilized on the electrodes. Until now, however, there have only been a few attempts to immobilize intact core complexes consisting of both the LH2 and LH1-RC components together onto one electrode. To realize such patterned structure, a technique for selective immobilization of each LH complexes needs to be developed. In addition, a method to avoid the quenching of LH complex immobilized on a gold electrode is useful in order to characterize the fabricated patterns. In this present work, we have developed a method for yielding the fluorescence of LH2 complex that was immobilized to a gold surface. Furthermore, LH2 immobilization in a 5 mmpitch line pattern and its fluorescence observation was succeeded using a lipid modified substrate.
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EXPERIMENT Design of the fabricated LH2 immobilized substrate is shown in Fig. 1. Small unilamellar vesicles (SUV) of GMB-DPPE and GMB-DOPG were prepared as follows. N-(4Maleimidobutyryloxy) succinimide (GMBS) (0.07 M) and 1,2-dioleoyl-sn-glycero-3phosphoethanola
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