Spectral and redox properties of benzodipteridine. A pulse radiolysis, laser flash photolysis and semi-empirical molecular orbital study

Abstract

The properties of the flavin enzyme mimic benzodipteridine (BDP) have been studied by pulse radiolysis, laser flash photolysis and semi-empirical molecular orbital (AM1) methods. The redox, protolytic and tautomeric equilibria in the ground state and excited triplet state were compared to the parent flavin molecule (FL). Pulse radiolysis was used to detect the one-electron reduced form of BDP which was found to be less basic than flavins, in agreement with the prediction of semi-empirical calculations. BDP is more electrophilic than FL in the ground state, but not in the excited triplet state, due to the lower triplet energy of the former as predicted by semi-empirical calculations. In contrast to FL, the triplet state of BDP does not appear to be more basic than the ground state, in agreement with the calculated shift in electron density upon excitation.

References

1. Various articles, in Chemistry and biochemistry of flavoenzymes, ed. F. Muller, CRC Press, Boca Raton, 1991, p. 171.
2. Y. Yano, M. Nakazato, K. Lizuka, T. Hoshino, K. Tanaka, M. Koga and F. Yoneda, J. Chem. Soc., Perkin Trans. 2, 1990, 2179.
3. M. J. S. Dewar, E. G. Zoebisch, E. F. Healey and J. J. P. Stewart, J. Am. Chem. Soc., 1985, 107, 3902.
4. J. Butler, B. Hodgson, B. M. Hoey, E. J. Land, J. S. Lea, E. J. Lindley, F. Rushton and A. J. Swallow, Radiat. Phys. Chem., 1989, 34, 633.
5. E. J. Land and A. J. Swallow, Biochemistry, 1969, 8, 2117.
6. F. Muller, P. Hemmerich, A. Ehrenberg, G. Palmer and V. Massey, Eur. J. Biochem., 1970, 14, 185.
7. H. S. Rzepa and G. A. Suner, J. Chem. Soc., Chem. Commun., 1993, 11 743.
8. R. F. Anderson, Biochem. Biophys. Acta, 1980, 722, 158.
9. C. Alhambra, F. J. Luque, J. Estelrich and M. Orozco, J. Org. Chem., 1995, 60, 969.
10. W. C. Neikam and M. M. Desmond, J. Am. Chem. Soc., 1964, 86, 4811.
11. A. Zweig, W. G. Hodgson and W. H. Jura, J. Am. Chem. Soc., 1964, 86, 4124.
12. P. F. Heelis and A. Koziolowa, J. Photochem. Photobiol., 1991, 11, 365.
13. D. Rehm and A. Weller, Ber. Bunsenges, Physik. Chem., 1969, 73, 834.
14. J. M. Lhoste, A. Hauge and P. Hemmerich, Biochemistry, 1975, 5, 3290.
15. S. Screiner, U. Steiner and H. E. A. Kramer, Photochem. Photobiol., 1975, 21, 81.
16. P. S. Song, Photochem. Photobiol., 1968, 7, 311.
17. S. J. F. Formosinho and L. G. A. Arnaut, Photochem. Photobiol. A, 1993, 1, 21.