[8a-A502-1~12] 12.7 Biomedical Engineering and Biochips

[8a-A502-7] Atomic level view of elementary processes involved in biosynthesis of melanin: dopaquinone reactions investigated by density functional theory based calculation

〇(D)Ryo Kishida¹, Hideaki Kasai^2,3 (1.Dept. Appl. Phys., Osaka Univ., 2.NIT, Akashi College, Japan, 3.CIA, Osaka Univ.)

Keywords:density functional theory, first principles calculation, melanin

Biosynthesis of melanin pigment involves dopaquinone (DQ) as an intermediate which can undergo two types of competitive reactions, i.e., cyclization and thiol binding. Cyclization is a ring closure reaction which proceeds via intramolecular C-N bond formation. Thiol binding is a substitution reaction which proceeds via thiol (R-SH)-DQ intermolecular C-S bond formation. In this study, we conducted the mechanistic investigation on the two competitive reactions. We calculated the potential energy surfaces for the two reactions along relevant degrees of freedom. We found the sulfhydryl surfur in thiol is strongly attracted by carbonyl carbons in DQ.