A Raman Study on the C(4)=O Stretching Mode of Flavins in Flavoenzymes: Hydrogen Bonding at the C(4)=O Moiety

Abstract

Raman spectroscopy was used to investigate the hydrogen bonding at the C(4)=O moiety of the isoalloxazine nucleus in a series of flavins and flavoproteins. Isotope effects of Raman bands confirmed that the band observed around 1,710 cm(-1) is mainly derived from C(4)=O stretching vibrational mode. A linear correlation was observed between the frequency of C(4)=O stretching and the chemical shift of 13C(4), suggesting that the data from both Raman and NMR spectroscopies reflect a common perturbation, i.e., hydrogen bonding. The maximum difference of C(4)=O frequency among flavins and flavoproteins examined is 36 cm(-1) [1,723 cm(-1) for riboflavin-binding protein (Kim, M. and Carey, P.C. (1993) J. Am. Chem. Soc. 115, 7015-7016) and 1,687 cm(-1) for the complex of medium-chain acyl-CoA dehydrogenase with acetoacetyl-CoA]; the maximum difference of 40-70 kJ/mol in the hydrogen bonding strength at the C(4)=O exists among flavoproteins. By use of an empirical linear correlation between the frequency of C=O stretching and the bond length of the C=O, it is estimated that the maximum difference in the bond length among flavoproteins treated here is ca. 0.017 A. The hydrogen bonding at the C(4)=O in medium-chain and short-chain acyl-CoA dehydrogenases becomes stronger upon complexation with substrate analogs. Since the hydrogen bonding at the C(4)=O is expected to enhance the electron-accepting capacity of the N(5) position, substrate-binding itself probably raises the reactivity of flavin, through enhancing the hydrogen bonding.

Raman spectroscopy of nondispersive intermediate frequency modes and their overtones in carbon nanotubes

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Vibrational Spectroscopy of an Algal Phot-LOV1 Domain Probes the Molecular Changes Associated with Blue-Light Reception

“…2-4 for the spectra. The assignment to molecular vibrations has been done on the basis of the published data and calculations (Dutta et al, 1980;Nishina et al, 1998;Altose et al, 2001;Abe and Kyogoku, 1987;Lively and McFarland, 1990;Bowman and Spiro, 1981;Hazekawa et al, 1997;Kim and Carey, 1993;McFarland, 1987;Zheng et al, 1999;Rath et al, 1994 downshifts by 5 cm ÿ1 in the presence of D 2 O. The strongest influence of D 2 O is exerted on the three negative bands in the region between 1280 cm ÿ1 and 1220 cm ÿ1 .…”

Acyl‐CoA dehydrogenases

“…Insight into the nature of these species starts with studies of the acetoacetyl-CoA complex with SCAD [86]. The molecular and steric prerequisites for formation of MCAD CT-complexes were then studied in detail by the group of Miura [10,72,[75][76][77][78]87,88]. They can be described in analogy to the interactions shown in Fig.…”