Examination of the structure of amylopectin molecules by fluorescent labeling

Amylopectin molecules from rice, maize, sweet potato and potato were examined by fluorescent labeling followed by gel-permeation HPLC. The number-average degree of polymerization (dpn) was determined to be in range of 9600–15,900. The molar-based distribution revealed the presence of three molecular species, large (dpn 13,400–26,500), medium (4400–8400) and small (700–2100). Their molar proportions differed by plant origin. The large species was a major component (43–63% by mole). A relatively large amount of the medium (16–28% by mole) and small (19–38%) species was found although their weight proportion was small (8–15, 1–4%, respectively). The three species from waxy rice amylopectin had a similar chain-length distribution and also a similar size-distribution of C chains. These results suggested that the three species were basically similar in cluster structure but different in number of clusters per molecule.