Preparation of Catalytic Antibodies toward the Synthesis of Sequential Polypeptides

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Monoclonal antibodies were raised against peptides containing nonnatural amino acids carring azobenzene group and pyrenyl group, respectively. The anti-azobenzene antibody bound only trans azobenzene group and released it when it was photoisomerized to the cis form. The photoisomerization of bound azobenzene group was found to take place inside the binding site. By using this unique property, a photoswitching of redox enzyme reaction was attempted. When an azobenzene unit was linked to an NAD^+-derivative, the latter showed normal mediation activity in a coupled redox enzyme reaction of alcohol dehydrogenase and diaphorase. When the anti-azobenzene antibody was added to the enzyme system, the mediation activity was completely suppressed in the dark, but the mediation activity recovered when the system was irradiated with UV light. The photocycle could be repeated many times.The photocontrolled antigen-antibody reaction was carried out on a monolayr containing azobenzene groups cast on a flat surface of mica. The antibodies bound on the monolayr surface were directly observed with atomic-force microscopy (AFM) technique. The number of antibody increased with increasing the hapten content, indicating that the binding is specific to the hapten groups. Photocontrol of the hapten-antibody reaction was also achieved on the monolayr surface.The anti-pyrenyl antibody bound a variety of pyrenyl derivatives including L-1-pyrenylalanine. But it did not bind D-1-pyrenylalanine. The unique property will be applied to optical resolution of nonnatural amino acids. The pyrenyl fluorescence of pyrenyl group bound to the anti-pyrenyl antibody was studied in detail. It was found that the pyrenyl group in the excited state remains inside the binding site and fluoresces.