Structural Studies of Pullulan by Nuclear Magnetic Resonance Spectroscopy

Abstract

Nuclear Magnetic Resonance (NMR) spectroscopy was used to probe the primary structure of the glucan pullulan. Carbon-13, proton and phospliorus-31 NMR spectra in aqueous solution of the intact polysaccharide obtained from three different sources indicate that significant suuctural differences can occur among these samples. In particular, two samples consist solely of a(1+6) linked maltotriose units, in accord with the generally accepted structure. However a third sample has fewer a(l-+6) linkages and appears to consist of higher a( 1 + 6) linked maltooligosaccharides in addition to maltotriose. Unlike the other samples. this sample was also phosphorylated. Enzymatic digzstion of pullulan followed by NMR spectroscopy using pullulanase confirmed these results, as did HPLC analysis of the resulting digest, which showed the presence of maltooligosaccharides consisting of ten and more glucose units. However, HPLC analysis of acid hydro1 ysed pullulan indicated that no sugars other than glucose were present in any of the samples examined.

The synthesis and characterization of poly(ethylene glycol) grafted on pullulan

“…Table I shows the feed molar ratio of PEG and glucose ring of pullulan and the DS values of the products. The DS values of the products were determined by high‐resolution 1 H‐NMR spectroscopy in D 2 O18, 19; it is obtained by comparing the integration value at 5.2–5.4 ppm (2H) assigned to H‐4 with that at 4.2 ppm assigned to the modified PEG methylene (2H) protons. The table shows that DS values of the products increase with the amount of PEG added.…”

Molecular mobility and microscopic structure changes in κ-carrageenan solutions studied by gradient NMR

“…The corresponding signals are indicated by p and , respectively. Detailed information on the signal assignments of pullulan and -carrageenan can be found in the literature (Mclntyre & Calgary, 1993;Tojo & Prado, 2003). The water peak at 4.7 ppm was completely eliminated due to the fast diffusion of water.…”

Estimation of the hydrodynamic screening length in κ-carrageenan solutions using NMR diffusion measurements

“…Detailed information on the signal assignments of k-carrageenan and pullulan can be found in the literature. 13,14 The intensity of the peak from the anomeric proton of pullulan at 5.36 p.p.m., which is separated from the peaks of k-carrageenan, decayed with increasing g and indicates the diffusion of pullulan among the network structure formed by the k-carrageenan chains.…”