Starch has been used over several millennia for a number of different applications. However, research on understanding this substance only spans about three centuries starting with Leeuwenhoek who observed it in 1716. This story of discovery of the molecular structure and architectural makeup of starch is chronicled in a series of six essays of which this is the fifth with a focus on the understanding of amylopectin structure. Research with a focus on the structure of amylopectin, the branched and major component in starch granules, started only in the 1940s when accurate techniques for the separation of amylose and amylopectin were developed. The understanding of amylopectin structure went hand in hand with research on starch granule crystallinity and lamellar organization. The discoveries of new enzymes involved in starch biosynthesis and degradation added to the understanding of amylopectin structure. Soon it became apparent that enzyme preparations used in this kind of research had to be of highest purity in order to achieve accurate results. The purification of debranching enzymes from bacterial sources, in combination with the new technique of gel-permeation chromatography, revolutionized the understanding of the unit chain composition in amylopectin as being different from that of glycogen, and resulted in the proposal of the cluster structure of amylopectin.
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