2D-IR spectroscopy of azide-labeled carbohydrates in H₂O.

This article focuses on the characterization of azide-labeled carbohydrates as vibrational probes for two-dimensional infrared (2D-IR) spectroscopy to study carbohydrate dynamics and protein–carbohydrate interactions. The study examines commercially available azide-functionalized monosaccharides (glucose and galactose) and more complex carbohydrates (N-acetylglucosamine and lactose) in aqueous solution, revealing that the vibrational absorption profiles and dynamics depend primarily on the azide labeling position on the carbohydrate ring, with additional variations between isomers. Notably, azide groups at the C2 position of glucose exhibit a longer vibrational lifetime and narrower spectral linewidth compared to other samples, suggesting distinct local environments and solvent accessibility. The findings demonstrate that azide-labeled carbohydrates produce strong, well-resolved 2D-IR signals without interfering Fermi resonances and remain detectable at biologically relevant millimolar concentrations in water, supporting their potential use in future biophysical studies of enzymatic catalysis and protein–carbohydrate interactions.