The π–π* molecular structure of flavin of FADH− enzymatic cofactor using the LCAO method

The π–π* molecular structure (eigenenergies and eigenfunctions) of flavin tricyclic ring is calculated, using the linear combination of atomic orbitals (LCAO) method containing only pz atomic orbitals. In respect to FADH− position opposite to DNA lesion in photolyase, flavin's HOMO is found to be distributed in the central and distal side, while LUMO is localized in the distal side of flavin (the side that is closer to the adenine part of FADH− and farther than the DNA dimer lesion). LUMO1 as well as LUMO2 are mainly distributed in the proximal side of flavin (the side that is closer to the DNA dimer). Our findings are compared with previous theoretical results as well as with experimental values of known π–π* transitions.