| Abstract: | Fragments of amylose were enzymatically synthesized and purified to α-(a→4)-glucans of well defined degress of polymerization by preparative size exclusion chromatography. Maltooligosaccharides from DP 3 to 12 were subjected to 13C-NMR-spectroscopy. The addition of iodine as a complexing agent selectively affected the carbon atoms involved in the glycosidic bond. Resonances of C-1 and C-4 experienced a dramatic downfield shift. This is interpreted as a change of conformation of the amylose helix. The shift differences can be measured conveniently and be used for calculations of complex stability constants. Maltohexaose and higher saccharides gave strong effects upon complexation, indicating that one helical turn brings about a gain in helical stability. No lower chain-length limit for the complex-forming capacity was observed. Even the smallest fragments of amylose showed complexing behaviour. |
