Molecular Construction Group

■Object

Making things small gives a great benefit for human beings: highly densely packed functions, small energy to produce and operate the system and less harmful effect to the environment. The ultimate goal of the ﾒshrinkingﾓ technology should be the molecular-level construction of machines (molecular or nano-technology). The technology could be the key in future industries.

■Results in Fiscal Year

We have examined the handling of protein and peptide molecules as models to construct molecular machines. Bacterial photosynthetic reaction centers (RCs) are mostly used. RCs convert light energy to electric potential Orientation of the molecule is required to enable the efficient electron flow. Enhancement of light energy conversion could realize the bio-molecular devices.

(1) Molecular handling of proteins at air-water interface and in liposome

Molecular orientation of RC has been studied. Rc of Rhodopseudomonas viridis was chemically modified by cross-linkage with horse heart cytochrome c. The polar distribution of the hydrophobicity/hydrophilicity in the molecular complex was effective for the control of the orientation at the interface. The complex was found to be useful for the orientation also in liposomes.

(2) Energy transfer molecular system

Artificial light-harvesting system has been constructed for energy transport to RC. RCs and bacteriochloro-phylls were incorporated in liposomes with changing the ratio. Light quanta entrapped by bacteriochloro-phylls were transferred to RC. The energy transfer became more efficient by decreasing the distance of the two kinds of molecules. Chlorophylls extracted from plants could be also useful for the collection of photones and excitation of RCs.

(3) Genetic methods for protein construction

Genetic engineering methods for Rhodopseudomonas viridis has been prepared. RC molecules fused with foreign proteins were designed by using the genetic method to give different physical nature. A fused protein of luciferace with H-subunit of RC was prepared and its synthesis in the cell was confirmed. The method for isolation of the RC containing luciferace-H subunit is being studied.

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