Electronic properties of flavins: Implications on the reactivity and absorption properties of flavoproteins

✍ Scribed by Johan Wouters; François Durant; Benoît Champagne; Jean-Marie André

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 366 KB
• Volume: 64
• Category: Article
• ISSN: 0020-7608
• DOI: 10.1002/(sici)1097-461x(1997)64:6<721::aid-qua9>3.0.co;2-y

✦ Synopsis

Electronic and structural properties of three protonated forms HFl , ox q Ž . q Ž .x H Fl N , and H Fl N of lumiflavin have been determined at the HFr3-21G level 2 ox 5 2 ox 1 of approximation. Larger delocalization and basicity explain the favorable protonation of N with respect to N whereas N protonation considerably activates the electrophilicity 1 5 1 of N with respect to C . The relative position of the first electronic transition evaluated 5 4 a ؒ Ž . ؒ Ž . at the CNDOrCI level for the radicalar H Fl N and H Fl N structures further 2 5 2 1

supports the classification of the flavoenzymes into two classes. Moreover, the -U transition has been correctly placed as the lowest energy transition for the neutral oxidized lumiflavin and predicts a blue shift of the low-lying electronic transition upon monoprotonation. Finally, from the analysis of the molecular complex between oxidized Ž . lumiflavin HFl and hydroquinone, we have rationalized the complex formation in ox terms of the complementarity between the molecular electrostatic potentials as well as in terms of the overlap between the frontier orbitals involved in these charge transfer process.