ELECTROCHEMICAL PROPERTIES OF POLY(L-2-ANTHRAQUINONYLALANINE)

Electrochemical behavior of two block copolypeptides consisting of pol y(L-2-anthraquinonylalanine) unit as a component was studied with volt ammetric analyses and electrochemical spectroscopy. Cyclic voltammetry and differential pulse voltammetry indicated that the anthraquinonyl groups in the polypeptides show only the first redox wave at the poten tial that corresponds to the monoanion formation of monomeric compound s. Under the same conditions monomeric compounds showed both the first and second redox waves. Absorption spectra under constant electric po tential indicated that anthraquinone dianions are formed in the polype ptides under potentials where monoanions are formed in the monomeric c ompounds. The result indicates that dianions are more stable than mono anions in the polypeptides. The mechanism of dianion formation was ten tatively attributed to fast electron migrations among anthraquinonyl s ide groups of the polypeptides, followed by efficient disproportionati ons. CD spectroscopy indicated that no conformational change is associ ated with the redox processes. These unique properties suggest that po ly(anthraquinonylalanine) is a promising candidate for a helical molec ular wire that mediates electrons between electrodes and redox enzymes .