OBSERVATION OF THE HELICAL STRUCTURE OF THE BACTERIAL POLYSACCHARIDE ACETAN BY ATOMIC-FORCE MICROSCOPY

A method has been developed that has been found to give reproducible i mages of uncoated polysaccharides by Atomic Force Microscopy (AFM). Aq ueous solutions of the polysaccharide are deposited as drops onto fres hly cleaved mica surfaces, air dried, and then imaged under butanol. T he method has been used to obtain images of the bacterial polysacchari de acetan. In regions within the deposited sample, where the molecules are aligned side-by-side, it has been possible to observe a periodic structure along the polysaccharide chain, attributable to the helical structure of acetan.