Comparison of Small-Angle Scattering Methods for the Structural Analysis of Octyl-β-maltopyranoside Micelles

Small-angle neutron scattering (SANS) and small-angle X-ray scattering (SAXS) experiments were performed to investigate the micelle structure of n-octyl-β-maltopyranoside (OM). Density measurements were carried out to obtain the volumetric characteristics of OM for micelle structure analysis. Both temperature and concentration were varied in scattering experiments to study their effects on micelle size. The scattering data were analyzed by the indirect Fourier transformation method (IFT) and model fitting. The IFT method gave the radius of gyration of the micelles and their pair distance distribution function. It was found that the radii of gyration from SANS data were much smaller than those from SAXS data at similar solution conditions. Moreover, pair distance distribution functions from SANS and SAXS data were also different. Model fitting indicated that a spherical shell model can be used to describe both SANS and SAXS data using similar structure parameters. Comparison of SAXS data in D2O and H2O shows that the OM micelle has a similar structure in both solvents. The size of the micelle does not increase with increasing concentration up to 188 mM. From 10 to 50 °C, the structure of the micelle is not sensitive to temperature changes. Comparison of the micelle structures of OM with those of its two closely related glycolipids, n-octyl-β-glucopyranoside (OG) and n-dodecyl-β-maltopyranoside (DM), suggests that the hydrophilic force plays an important role in the micelle structure of glycolipids.