Electronic transition moments of 6-methyl isoxanthopterin--a fluorescent analogue of the nucleic acid base guanine.

ABSTRACT: Fluorescent nucleic acid base analogues are important spectroscopic tools for understanding local structure and dynamics of DNA and RNA. We studied the orientations and magnitudes of the electric dipole transition moments (EDTMs) of 6-methyl isoxanthopterin (6-MI), a fluorescent analogue of guanine that has been particularly useful in biological studies. Using a combination of absorption spectroscopy, linear dichroism (LD) and quantum chemical calculations, we identified six electronic transitions that occur within the 25,000-50,000 cm(-1) spectral range. Our results indicate that the two experimentally observed lowest-energy transitions, which occur at 29,687 cm(-1) (337 nm) and 34,596 cm(-1) (289 nm), are each polarized within the plane of the 6-MI base. A third in-plane polarized transi

SUBMITTER: Widom JR 

PROVIDER: S-EPMC3553960 | biostudies-literature | 2013 Jan

REPOSITORIES: biostudies-literature