title: Self-assembled monolayer of light-harvesting core complexes from photosynthetic bacteria on a gold electrode modified with alkanethiols.
abstract: Light-harvesting antenna core (LH1-RC) complexes isolated from Rhodoseudomonas palustris were self-assembled on a gold electrode modified with self-assembled monolayers (SAMs) of the alkanethiols NH2(CH2)nSH, n = 2, 6, 8, 11; HOOC(CH2)7SH; and CH3(CH2)7SH, respectively. Adsorption of the LH1-RC complexes on the SAMs depended on the terminating group of the alkanethiols, where the adsoption increased in the following order for the terminating groups: amino groups > carboxylic acid groups > methyl groups. Further, the adsorption on a gold electrode modified with SAMs of NH2(CH2)nSH, n = 2, 6, 8, 11, depended on the methylene chain length, where the adsorption increased with increasing the methylene chain length. The presence of the well-known light-harvesting and reaction center peaks of the near infrared (NIR) absorption spectra of the LH1-RC complexes indicated that these complexes were only fully stable on the SAM gold electrodes modified with the amino group. In the case of modification with the carboxyl group, the complexes were partially stable, while in the presence of the terminal methyl group the complexes were extensively denatured. An efficient photocurrent response of these complexes on the SAMs of NH2(CH2)nSH, n = 2, 6, 8, 11, was observed upon illumination at 880 nm. The photocurrent depended on the methylene chain length (n), where the maximum photocurrent response was observed at n = 6, which corresponds to a distance between the amino terminal group in NH2(CH2)6SH and the gold surface of 1.0 nm.
authors.affiliation: Department of Applied Chemistry, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555, Japan.
authors.forename: Masaharu
authors.initials: M
authors.lastname: Kondo
authors.forename: Yukari
authors.initials: Y
authors.lastname: Nakamura
authors.forename: Kaoru
authors.initials: K
authors.lastname: Fujii
authors.forename: Morio
authors.initials: M
authors.lastname: Nagata
authors.forename: Yoshiharu
authors.initials: Y
authors.lastname: Suemori
authors.forename: Takehisa
authors.initials: T
authors.lastname: Dewa
authors.forename: Kouji
authors.initials: K
authors.lastname: Iida
authors.forename: Alastair T
authors.initials: AT
authors.lastname: Gardiner
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Cogdell
authors.forename: Mamoru
authors.initials: M
authors.lastname: Nango
mesh_terms: D000473:Alkanes / Q000737:chemistry*; D004566:Electrodes; D004579:Electron Transport; D005292:Ferricyanides / Q000737:chemistry; D006046:Gold; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry*; D018625:Microscopy, Atomic Force; D010084:Oxidation-Reduction; D011487:Protein Conformation; D012241:Rhodopseudomonas / Q000201:enzymology*; D013438:Sulfhydryl Compounds / Q000737:chemistry*
chemical_list: D000473:Alkanes; D005292:Ferricyanides; D045342:Light-Harvesting Protein Complexes; D013438:Sulfhydryl Compounds; C007931:hexacyanoferrate III; D006046:Gold