Intramolecular and Intermolecular Perturbation on Electronic State of FAD Free in Solution and Bound to Flavoproteins: FTIR Spectroscopic Study by Using the C = O Stretching Vibrations as Probes

The intramolecular and intermolecular perturbation on the electronic state of FAD was investigated by FTIR spectroscopy by using the C=O stretching vibrations as probes in D₂O solution. Natural and artificial FADs, i.e. 8-CN-, 8-Cl-, 8-H-, 8-OCH₃-, and 8-NH₂-FAD labelled by 2-¹³C, ¹⁸O=C(2), or 4,10a...

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Published inJournal of biochemistry (Tokyo) Vol. 142; no. 2; pp. 265 - 272
Main Authors Nishina, Yasuzo, Sato, Kyosuke, Setoyama, Chiaki, Tamaoki, Haruhiko, Miura, Retsu, Shiga, Kiyoshi
Format Journal Article
LanguageEnglish
Published England Japanese Biochemical Society 01.08.2007
Oxford University Press
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Summary:The intramolecular and intermolecular perturbation on the electronic state of FAD was investigated by FTIR spectroscopy by using the C=O stretching vibrations as probes in D₂O solution. Natural and artificial FADs, i.e. 8-CN-, 8-Cl-, 8-H-, 8-OCH₃-, and 8-NH₂-FAD labelled by 2-¹³C, ¹⁸O=C(2), or 4,10a-¹³C₂ were used for band assignments. The C(2)=O and C(4)=O stretching vibrations of oxidized FAD were shifted systematically by the substitution at the 8-position, i.e. the stronger the electron-donating ability (NH₂ > OCH₃ > CH₃ > H > Cl > CN) of the substituent, the lower the wavenumber region where both the C(2)=O and C(4)=O bands appear. In contrast, the C(4)=O band of anionic reduced FAD scarcely shifted. The 1,645-cm⁻¹ band containing C(2)=O stretching vibration shifted to 1,630 cm⁻¹ in the medium-chain acyl-CoA dehydrogenase (MCAD)-bound state, which can be explained by hydrogen bonds at C(2)=O of the flavin ring. The band was observed at 1,607 cm⁻¹ in the complex of MCAD with 3-thiaoctanoyl-CoA. The 23 cm⁻¹ shift was explained by the charge-transfer interaction between oxidized flavin and the anionic acyl-CoA. In the case of electron-transferring flavoprotein, two bands associated with the C(4)=O stretching vibration were obtained at 1,712 and 1,686 cm⁻¹, providing evidence for the multiple conformations of the protein.
Bibliography:istex:22AFA4F2C1D148E5E42CFBAF2E10F4A543FF6977
ark:/67375/HXZ-707TJFKM-9
ObjectType-Article-1
SourceType-Scholarly Journals-1
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ISSN:0021-924X
1756-2651
DOI:10.1093/jb/mvm129