From Proteopedia
proteopedia linkproteopedia linkAmylose is a linear polymer of glucose that occurs in starch. It occurs in foods such as grains and potatoes, and it is a major source of energy (calories) in most diets. There are three major forms of crystalline amylose, A, B, and V, that differ in the three-dimensional structure. Amylose can also occur as amorphous structure, for example in starch or when cooked in water. Amylose is distinct from amylopectin, which is a branched polymer of glucose, and from cellulose, which is a linear polymer of glucose that differs in stereochemistry from amylose. In the context of naturally occurring starch, parts of amylopectin form semi-crystalline layers resembling amylose A or B, while amylose itself occurs in the amorphous parts.
Structure
| and B occur as parallel double-helices of glucose chains, with 6 glucose units per turn. In contrast, amylose V shows single helices, as illustrated in the crystal structure of (same structure shown as ). A more irregular conformation of a cyclic amylose occurs is found in complex with a protein in the structure 5jiw. In solution, amylose occurs as flexible hydrated single helices. These can bind to small molecules to form inclusion complexes such as the famous starch/iodine/iodide complex. Because of the difficulty in characterizing non-crystalline or semi-crystalline polymeric materials with complex chemical makeup (variation in chain length and location of branch points), the structure of starch and its components [1] is less well characterized than that of proteins.
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References
- ↑ Perez, Serge & Bertoft, Eric. (2010). The molecular structures of starch components and their contribution to the architecture of starch granules: A comprehensive review. Starch ‐ Stärke. 62. 389 - 420. 10.1002/star.201000013.
