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Electronic properties of flavins: Implications on the reactivity and absorption properties of flavoproteins
Author(s) -
Wouters Johan,
Durant François,
Champagne Benoît,
André JeanMarie
Publication year - 1997
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/(sici)1097-461x(1997)64:6<721::aid-qua9>3.0.co;2-y
Subject(s) - chemistry , protonation , cndo/2 , molecular orbital , computational chemistry , electronic structure , flavin group , delocalized electron , photochemistry , chemical physics , molecule , organic chemistry , ion , enzyme
Electronic and structural properties of three protonated forms [HFl ox , H 2 Fl ox + (N 5 ), and H 2 Fl ox + (N 1 )] of lumiflavin have been determined at the HF/3‐21G level of approximation. Larger delocalization and basicity explain the favorable protonation of N 1 with respect to N 5 whereas N 1 protonation considerably activates the electrophilicity of N 5 with respect to C 4a . The relative position of the first electronic transition evaluated at the CNDO/CI level for the radicalar H 2 Fl · (N 5 ) and H 2 Fl · (N 1 ) structures further supports the classification of the flavoenzymes into two classes. Moreover, the π‐π* 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 lumiflavin (HFl ox ) and hydroquinone, we have rationalized the complex formation in 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. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 64 : 721–733, 1997