Metal-flavin complexation. A resonance Raman investigation

Area of Science:

• Biophysical Chemistry
• Spectroscopy
• Biochemistry

Background:

• Flavin compounds exhibit intense fluorescence, complicating spectral analysis.
• Resonance Raman spectroscopy can yield high-quality spectra for flavins, despite fluorescence.
• Understanding flavin-protein interactions is crucial for flavoenzyme function.

Purpose of the Study:

• To obtain resonance Raman spectra of flavins in different chemical environments.
• To assess the utility of resonance Raman spectroscopy in probing flavin-metal interactions within flavoenzymes.
• To investigate the structural and electronic effects of metal complexation on flavin molecules.

Main Methods:

• Acquisition of resonance Raman spectra for flavin mononucleotide (FMN) complexed with silver (Ag+) and ruthenium (Ru2+).
• Analysis of spectral changes, particularly in the 1580 cm-1, 1410 cm-1, and 1260 cm-1 regions.
• Comparison of spectral data from different metal-flavin complexes to identify common vibrational changes.

Main Results:

• Significant changes in the FMN resonance Raman spectrum were observed upon Ag+ complexation, affecting key vibrational modes.
• Similar spectral alterations were noted in a Ru2+-FMN complex, indicating a general effect of metal binding.
• The observed spectral shifts are attributed to vibrational changes induced by metal coordination at N-5 and the C-4 oxygen of flavin, rather than vibronic interactions.
• A structural model for the Ag+-FMN complex was proposed.

Conclusions:

• Resonance Raman spectroscopy is effective for studying flavin-metal interactions, even in the presence of fluorescence.
• Metal complexation induces distinct vibrational changes in flavins, providing insights into binding sites and interactions.
• This technique holds potential for analyzing direct flavin-metal interactions in metalloflavoproteins in dilute solutions.