# What do we know about the structure of the amylopectin iodine complex?

I am studying a method of finding the ratio between amylose and amylopectin using the difference in color of the amylose-iodine complex(blue) and the amylopectin-iodine complex (red/brown).

Through the use of techniques like x-ray crystallography, the structure of the amylose-iodine complex seems to be fairly well understood, as iodine inside a helical chain of amylose.

However, I cannot find many papers that explicitly claim the structure of the amylopectin-iodine complex. Perhaps the branched nature makes it more complex, or the variety in structure unlike amylose makes it impossible to find a general structure.

Are we aware of any certain structure of the amylopectin iodine complex? Any directions to relevant papers would be appreciated.

• For clarification: What you search is a data set (e.g., as a .cif or .pdb file) to access the structure data like in the case of «Crystal structure of cellulose-iodine complex», Tashiro et al. 2019Polymer140, figures 7 (apparently based on diffraction data), 10/11 (apparently computation based)? – Buttonwood Apr 10 at 8:52
• «Understanding Starch Structure: Recent Progress» by Bertoft appears to be an entry to consider, too. – Buttonwood Apr 10 at 9:01
• For clarification, I am just looking for information, qualitative or quantitative, on the structure of the amylopectin-iodine complex. (or whether that can even be found, based on variety of amylopectin structure). Tashiro et al. (2019) seems to cover both starch and cellulose, but only amylose and not amylopectin. For starch, it seems to be just the typical single helix structure. – jettosutorimu Apr 10 at 12:13
• Because amylopectin is less likely to form chanels than amylose, I think chances are lower to form a regular complex with iodine. Because both are biopolymers, they are not a typical entry in CSD database, but as sugars not part of pdb.org either. Maybe the author of this site used for the illustration of the «empty» structure of amylopectin X-ray based data and may hint where to find additional data (complexes with iodine). Nevertheless, continue literature search in scientific databases (web of science, scifinder). – Buttonwood Apr 10 at 19:52
• A last resort may be to contact researchers active in the field (e.g., doi.org/10.1186/s40104-018-0303-8) since research in sugars has much tradition (example and its «cited by» below the publication). – Buttonwood Apr 10 at 19:53