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.