Optical properties of sugars. VI. Circular dichroism of amylose and glucose oligomers

Abstract

Abstract The CD spectra of amylose, the maltose oligomers, cellobiose, and the cyclodextrins are measured in aqueous solution to 1640 Å. Two bands are found in this region. An examination of chromophorically equivalent but conformationally different glucans demonstrates that the CD of glucans is sensitive to conformation. However, the conformation of the subunits in the maltose oligomer series appears independent of chainlength. The conformations of the interior maltosyl groups of this series are all approximately equivalent. A comparison of the amylose and cycloamylose spectra indicates that amylose is substantially biased in its chirality. Since there is little chainlength dependence, the oligomers should have a similar chirality bias. The butanol complex of amylose, which is believed to have a V‐form helical conformation, has a CD similar to free aqueous amylose. This is consistent with conformational calculations on amylose which predict that the maltosyl subunits of amylose are restricted to a small region on its conformational map which includes the V‐form helix. It is also consistent with the idea that amylose a loosely wound and extended helix in aqueous solution.