13C-detection two-dimensional NMR approaches for cellulose derivatives

To demonstrate the effectiveness of ¹³C-detection two-dimensional NMR methods used for the characterization protein structures for the characterization of cellulose derivatives, ¹³C–¹³C COSY, ¹³C–¹³C INADEQUATE, and ¹³C–¹³C TOCSY experiments were applied to ¹³C-enriched sodium carboxymethyl cellulose and cellulose acetate. These samples were prepared from bacterial cellulose biosynthesized by Gluconacetobacter xylinus ATCC 53582 in medium containing 20 % uniformly ¹³C-labelled glucose in unlabeled glucose. The combination of ¹³C–¹³C COSY (or ¹³C–¹³C INADEQUATE) and ¹³C–¹³C TOCSY spectra of the cellulose derivatives facilitated the direct and precise assignment of all ring carbons of each anhydroglucose unit comprising the cellulose chain during the short experimental time. In addition, a short spin-lock time (~24 ms) in the ¹³C–¹³C TOCSY experiments was revealed to be preferable for achieving improved sensitivity and obtaining correlation signals between all carbons in the anhydroglucose units of the cellulose derivatives.