Polyglucose-protein complexes.
Abstract The specific solubility parameters of glycogen-gelatin complexes are completely destroyed after brief exposure to proteolytic enzymes. The minimal polysaccharide-gelatin binding ratios for the complete binding of dextran, glycogen, dextrin, and soluble starch (erythrodextrin free) are 4, 1, 1, and 0.5, respectively, on a dry weight basis. The stoichiometric binding ratios of polyglucose-gelatin mixtures were independent of polyglucosan molecular weight classes. Sequential degradation of gelatin by autoclaving resulted in more rapid destruction of polysaccharide binding sites than the sites responsible for gelation. The 1 → 6 polyglucose binding sites were more labile than the 1 → 4 polyglucose binding sites on the gelatin molecule. Autoclaving of soluble starch, glycogen, or dextran had no effect on their ability to bind with gelatin. Competitive-inhibition studies suggest that the gelatin molecule possesses specific binding sites for the various polyglucosans. Reversible dissociation of polyglucose-gelatin complexes can be accomplished by 44% phenol/water extraction of polyglucose-gelatin complexes. The presence of polyglucose in alkaline Cu 2+ -gelatin solutions does not alter the ability of bound Cu 2+ to inhibit gelation of gelatin. The presence of bound forms of Cu 2+ in gelatin, polyglucosans and gelatin-polyglucose mixtures can be detected by analysis of ESR spectra and is dependent upon the pH of the respective solutions. The ESR spectra of Cu 2+ -gelatin complexes are different in acid and alkaline environments. At pH 4.5 the hyperfine structures of Cu 2+ -polyglucosans are destroyed by polyglucosan-gelatin interactions. At pH 10.5, Cu 2+ -doped gelatin and gelatin-glycogen mixtures exhibit similar ESR parameters whereas glycogen did not bind Cu 2+ . Possible relationships between Cu 2+ binding sites of these polymers and the specific sites responsible for both biopolymeric complex formation and the gelation phenomenon are discussed.