Self-molecular assembly of light-harvesting complex isolated from photosynthetic bacteria on modified electrodes

Abstract

Pigments play an important role on energy-transfer process in light-harvesting (LH) polypeptides complex of photosynthesis, where porphyrins such as bacteriochlorophylls (BChls) are assembled according to cooperative interactions between the LH polypeptides and BChls. It is interesting to note that the LH polypeptides organize the BChls so that an efficient energy transfer process between BChls may occur. In this paper, we examine the self-assemble of Zn-BChla using LH polypeptides separately isolated from photosynthetic bacteria to organize an artificial LH complex. The key to the molecular assembly is ready availability of the LH complex-formation on modified indium-tin-oxide (ITO) electrode. We selected the native LH polypeptides isolated from photosynthetic bacteria, because the native polypeptides formed a stable Zn-BChla complex in octylglucoside (OG) solution analogous to the LH 1-type complex. The ITO electrode was silanized to introduce amino groups and then, the LH polypeptides complex was assembled on the modified ITO by soaking the ITO electrode into the OG solution forming the LH polypeptides complex (phosphate buffer, pH = 7.0). The Qy band of Zn-BChla in the LH complex on the ITO was red-shifted analogous to the subunit-tipe complex of the LH 1 complex, indicating the self-molecular assembly of the LH 1-type complex on the electrode