Dihydrobiopterin (H2Bip) and biopterin (Bip) are two molecules in the pterin family that accumulate in the white patches of the skin in patients with the disease vitilgo. Using HPLC, fluormetric, and other techniques, Thomas and co-workers proposed an eleven-step mechanism by which H2Bip is photo-oxidized to Bip in aqueous media. (�Photochemistry of Dihydrobiopterin in Aqueous Solution�, Thomas et.al. Org. Biomol. Chem., 2010  , 8, 800-810.) In the present work, we present the results of a collaboration with the above mentioned authors where the proposed mechanism is investigated using Density Functional Theory (DFT) calculations. The calculations explore the various photochemical spin states (excited-singlet and -triplet states), electron-transfer reactions, and radical reactions using the PCM (Polarizable Continuum Model) for solvation using water as the dielectric constant for all species. These thermodynamic results, and their known limitations, are used to support the feasibility of the literature proposed mechanism.

DFT study of the mechanism of the photo-oxidation of dihydrobiopterin in aqueous media

245th National Meeting (2013)

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