Theoretical study of the electronic spectra of oxidized and reduced states of lumiflavin and its derivative

Time-dependent density functional theory has been applied to investigate the electronic absorption spectrum of oxidized and reduced lumiflavin and its derivative, 8-NH2-lumiflavin. The calculations allow the authors to explain the origin of the difference in spectral features between oxidized and reduced states of lumiflavin. For the reduced lumiflavin, a reasonable assignment of the experimental spectrum has been made for the first time. Furthermore, the results obtained reveal that the NH2 group plays a critical role in shaping the spectral features of 8-NH2-lumiflavin, and offer a reasonable explanation for the spectral changes upon substituting the NH2 group for the CH3 group of lumiflavin. (C) 2007 Wiley Periodicals, Inc.