15N solid-state NMR as a probe of flavin H-bonding

Area of Science:

• Biochemistry
• Biophysics
• Spectroscopy

Background:

• Flavins are crucial cofactors mediating diverse biological reactions.
• Understanding how enzyme environments modulate flavin reactivity is key to enzyme function.
• Solid-state NMR (SSNMR) is explored as a tool to probe flavin electronic structure.

Purpose of the Study:

• To investigate the utility of SSNMR for probing flavin electronic structure.
• To compare the sensitivity of SSNMR and solution NMR to hydrogen-bonding interactions.
• To elucidate how hydrogen bonds influence flavin reactivity through electronic structure modulation.

Main Methods:

• Utilized solid-state NMR (SSNMR) to measure (15)N chemical shift tensor principal values (δ(ii)) of flavins.
• Employed a model system of the flavodoxin active site to study hydrogen-bonding effects.
• Performed density functional theoretical (DFT) calculations to complement experimental findings.

Main Results:

• SSNMR demonstrated superior responsiveness to hydrogen-bonding interactions compared to solution NMR.
• Hydrogen bonding to the flavodoxin active site model induced a 10 ppm increase in the δ(11) of N5.
• SSNMR distinguished between different hydrogen-bonding environments, unlike solution NMR.

Conclusions:

• SSNMR is a powerful technique for investigating flavin electronic structure and hydrogen-bonding interactions.
• Hydrogen bonds significantly modulate flavin electronic structure and reactivity.
• Computational methods like DFT can validate and explain SSNMR observations of flavin-environment interactions.