INDUCED CIRCULAR-DICHROISM STUDY OF THE AQUEOUS-SOLUTION COMPLEXATIONOF CELLO-OLIGOSACCHARIDES AND RELATED POLYSACCHARIDES WITH AROMATIC DYES

Acetobacter xylinum, grown in the presence of low levels of the water- soluble dye Calcofluor White ST produces a pellicle of cellulose that has no detectable crystallinity. Biological factors of this sort are p robably more important than physical factors in controlling the higher order structures of celluloses. Circular dichroism (CD) is induced by complexes that are formed by specific interactions between chiral oli gosaccharides and dye molecules. Using CD, equilibrium constants were measured for the association reactions between various dyes with a ser ies of cello-oligosaccharides (n = 2-6), methylcellulose, hydroxypropy lcellulose (HPC), amylose, cyclomalto-oligosaccharides (cyclodextrins) , and the linear malto-oligosaccharides (n = 3-7). Possible structural features of the complexes are discussed. Dyes that are capable of bin ding to the higher cello-oligomers in aqueous solutions are the same d yes that modify the solid structure of bacterial cellulose. An analogy between the binding of water-soluble dyes to cello-oligosaccharides a nd the binding of the cellulose-degrading enzyme, cellobiohydrolase I, to cellulose is discussed.