Acid hydrolysis and molecular weights of various corn amylopectin and glycogen

Amylopectin samples were obtained from mature and immature sweet, dent, and waxy varieties of corn starch samples by dispersing the starch samples with either 6 M LiBr or bufered amyl alcohol solutions. The degree of branching, molecular weights, and radii of gyration were obtained on these amylopectins. The results were explained assuming that Erlander's proposed mechanism for the synthesis of starch from glycogen is valid. The corn amylopectins and an immature sweet corn glycogen sample obtained from Schoch were hydrolyzed at a pH of 4.2 at the refluxing temperature. Samples were taken at various time intervals. The values of Mw obtained from these samples showed that glycogen and amylopectin behave as randomly formed polymers. The rates of hydrolysis obtained in these studies indicate that the large molecules in all corn endosperm amylopectins and glycogens exist in chemical aggregates of four. These chemical aggregates do not appreciably influence the statistical size distribution of the amylopectin and glycogen molecules. A comparison of the properties of a sweet corn glycogen sample and an immature sweet corn amylopectin sample indicates strongly that glycogen is a precursor to starch.