STRUCTURES OF SUBFRACTIONS OF CORN AMYLOSE

Incubation of corn amylose in aqueous 1-butanol at 40° gave insoluble (Fppt) and soluble (Fsup) fractions. Fsup had a lower affinity for iodine (i.a. 16.0 g. 100 g-1) and a higher weight-average d.p. (d.p.w 5910) than Fppt (i.a. 20.5, d.p.w 2460). Fppt and Fsup contained linear and slightly branched molecules in the molar ratios 60:40 and 84:16, respectively. Of the branched molecules in the amylose, ∼ 89% was found in Fppt. This main branched molecule had d.p.w 5700, number-average d.p. (d.p.n) 2200, and 6 chains on average, and comprised the short (d.p.n ∼ 18) and extremely long (d.p.n > 370, d.p.w > 2760) chains. The branched molecules in Fsup had d.p.w 7840, d.p.n 1620, and 20 chains on average, and comprised short d.p.n ∼ 18), long (d.p.w > 230), and extremely long (d.p.w > 2730) chains. Maltohexaose was the shortest side-chain of the branched molecules. The large branched molecule in Fsup seemed to comprise an immature cluster. © 1990.