Molecular characterization of wheat amylopectins by multiangle laser light scattering analysis

Weight-average molecular weight (M(w)) and chain length of eight amylopectins isolated from one Australian, two United States, and five Korean wheats were measured using multiangle laser light scattering (MALLS) and refractive index (RI) detectors operated in a microbatch mode, and in a high- performance size-exclusion chromatography (HPSEC) mode. The M(w) of amylopectins measured in the microbatch mode ranged from 29 x 10⁶ to 349 x 10⁶. Three amylopectins (Geuru, Tapdong and WW) showed significantly high M(w) values over 200 x 10⁶. The M(w) measured by HPSEC mode with MALLS-RI detectors (42 x 10⁶ to 73 x 10⁶) were significantly less than those obtained in the microbatch mode with exception of dark northern spring hard wheat (DNS) amylopectin, indicating the possible variation of M(w) by the analysis mode. Root-mean square of the radius of gyration (R(g)) also was greater when the microbatch mode was used (122-340 vs. 95-116 nm). Chain length distributions of debranched amylopectins of different cultivars, measured by the HPSEC-MALLS-RI system, were similar. Weight average degrees of polymerization (DP(w)) of A, B¹, and larger B chains (B(≥2) had ranges of 13-22, 26-46, and 58-73, respectively, and mass ratios of A and B chains ranged from 0.7 to 1.1.