Infrared internal reflectance spectroscopic studies of protein-polysaccharide interactions

Abstract

Comparison of infrared attenuated total reflectance (IR-ATR) and transmission spectra of thin films of neutral and anionic polysaccharides showed that the ATR reflectivity technique resolved the OH deformation mode of the polysaccharides to a greater extent than the corresponding transmission spectra. In addition, the SO stretch band of fucan was a broad band at 1247 cm −1 in the transmission spectrum whereas the ATR spectrum split the band into a doublet at 1256 cm −1 and 1218 cm −1. Interactions between polysaccharides and between polysaccharides and gelatin were detected by noting decreases in intensities and shifts in the frequencies in the OH deformation bands of the polysaccharides, and, in the presence of gelatin, with concomitant shifts in the frequencies of the Amide I and II bands of the protein. Complex formation in which hydrogen bonding was involved was detected in thin films of the following biopolymeric mixtures: glycogen—gelatin, glycogen phosphate—gelatin, glycogen—fucan, fucan—gelatin, and fucan—gelatin in the presence of glycogen.