Two-dimensional rotating-frame Overhauser spectroscopy (ROESY) and (13)C NMR study of the interactions between maltodextrin and an anionic surfactant

Rotational frame nuclear Overhauser effect spectroscopy (ROESY) and (13)C NMR measurements were carried out to study the molecular interaction between maltodextrin, a digestive byproduct of starch, and an anionic surfactant. Significant differences in chemical shifts were observed when sodium dodecyl sulfate (SDS) was introduced into the maltodextrin (DE 10) solutions. (13)C NMR measurement indicated that there were downfield shifts and broadening of peaks, especially in the region of 75-81 and 100-103 ppm, which were assigned to carbons 1 and 4 of the d-glucopyranose residues of maltodextrin, respectively. ROESY spectra indicated cross-peaks between the SDS and maltodextrin protons. These peaks can arise only in the case of the designated SDS protons and maltodextrin protons being less than 0.5 nm apart for a substantial period of time. The most intense cross-peaks are those between the central CH(2) protons of SDS near 1.2 ppm and the maltodextrin protons ranging from 3.5 to 3.9 ppm. The SDS-H3 CH(2) protons were resolved from the bulk of the SDS protons, with peaks and shoulders at 1.25 ppm, which indicated an especially strong interaction of the SDS hydrophobic tail with MD6 and some less intense interactions with MD2, 4, and 5.