The structural organization of N-methyl-2-pyrrolidone + water mixtures: a densitometry, x-ray diffraction, and molecular dynamics study.

A combined approach of molecular dynamics simulations, wide angle X-ray scattering experiments, and density measurements was employed to study the structural properties of N-methyl-2-pyrrolidone (NMP) + water mixtures over the whole concentration range. Remarkably, a very good agreement between computed and experimental densities and diffraction patterns was achieved, especially if the effect of the mixture composition on NMP charges is taken into account. Analysis of the intermolecular organization, as revealed by the radial and spatial distribution functions of relevant solvent atoms, nicely explained the density maximum observed experimentally.

1H and 13C NMR studies of melon and head blubber of the striped dolphin (Stenella coeruleoalba).

Intact portions of melon, the echolocation organ of the striped dolphin (Stenella coeruleoalba), and the corresponding raw oils were analyzed by means of one- and two dimensional 1H and 13C NMR techniques. For comparative purposes the tissue and the raw oil of head blubber were also examined. Complete assignments of the spectra were obtained. Furthermore, dynamics of the lipid components was investigated by means of 13C NMR spin lattice relaxation time (T1). Analysis of the data revealed that lipid molecules in the tissue compartments experience a liquid-like microenvironment and that T1 values depend on the lipid composition and/or organization in the intact tissue framework. In particular, a dependence of the T1 values on the wax esters content in melon intact tissues was found. A possible correlation between dynamic parameters and sound propagation properties has been hypothesized.