FTIR and laser-Raman spectra of oligosaccharides in water: characterization of the glycosidic bond

Changes in conformation of oligosaccharides, and the constraints imposed by hydrogen bonding with the solvent, were studied by means of vibrational spectroscopy (FTIR-ATR and laser-Raman). Oligosaccharides differing in positions of the glycosidic bond, such as trehalose, sucrose, maltose, melibiose, lactose, maltotriose, raffinose, and stachyose, were investigated. FTIR spectra of oligosaccharides in aqueous solution at different concentrations allow differentiation of these molecules according to the types of glycosidic bonds present and the changes in conformation of their constituent monosaccharides. Characteristic spectral ranges influenced by the glycosidic linkage position, overall hydration, and concentration of the aqueous solution were found. Tentative assignment of the observed IR and Raman bands was achieved.