Self-assembled monolayer of light-harvesting core complexes from photosynthetic bacteria on a gold electrode modified with alkanethiols.

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 carbox...