Structure of building blocks in amylopectins

Glucose residues in amylopectin organised into building blocks (unfilled circles) and separated by residues in interblock segments (black circles). [Display omitted] ► Fine structure of building blocks is largely unique for different starches. ► Different starches have unique building block interconnections. ► Building blocks in cereal starches have preferred Haworth conformation. Building blocks represent the smallest, branched units found inside clusters of amylopectins. The building blocks from clusters of 10 different amylopectins, representing a wide variety of plants, were isolated and size-fractionated. The unit chain compositions were then analysed. It was found that the number of chains in building blocks increased in proportion to their size similarly in all samples regardless plant source. The smallest blocks (DP 5–9) consisted of 2 chains and the largest blocks (DP ⩾45), of which generally only little existed, possessed ⩾10 chains. Generally, the degree of branching increased with building block size, but the organisation of chains inside the blocks was unique for each sample. Nevertheless, compared to other plants, amylopectins from cereals (represented by rye, oats, rice and waxy maize) possessing elevated number of the shortest internal B-chains (DP 3–7), tended to have blocks with a lower ratio of A:B-chains, indicative of a preferred Haworth type of structure as opposed to the Staudinger configuration.