NMR study of translational and rotational dynamics in monoolein-water mesophases: Obstruction and hydration effects

Abstract

Using a variety of NMR methods (magnetic field gradient echo decays, 2H one- and two-dimensional spectra, spin-lattice relaxation rates), both translational and rotational dynamics of the constituents of monoolein MO/H(2)O mesophases have been studied. The experiments lead to the following conclusions. The translational dynamics of the lipid molecules is essentially dominated by obstruction effects due to the topologies of the diverse mesophases. On the other hand, water dynamics-in the regime of small water concentrations-is strongly influenced by hydration of the lipid head groups. Hydration is seen in diffusion data, in spectra and in spin-lattice relaxation of the water molecules. This work represents an involved extension of our recently published work [Chem. Phys. Lipids 106, 115 (2000)].

Solid-state Li NMR with applications to the translational dynamics in ion conductors

“…As far as the quadrupolar modulation is concerned, it is not possible to obtain a pure cos-cos data set for I = 3/2. The constant term in q ð1;3=2Þ l1 ðx Q tÞ, with l = 1 or 3, see Table 2, in addition to the diagonal and the anti-diagonal contributions, will lead to a cross-like feature in the spectra, similar to situations when liquid-like phases are additionally present [121,123,124]. While this is not necessarily a problem in the study of single crystals there are difficulties when studying polycrystalline or amorphous samples.…”

“…Eq. (124), values for the activation energy E a and the attempt frequency 1/s 0 can be determined. For example from the data for the n = 2 sample E a = 0.34 ± 0.1 eV and s 0 = (8.0 ± 5.0) · 10 À13 s [80].…”

“…(124), between the correlation time, s c and the activation energy E a and temperature T was assumed. The attempt frequency 1/s 0 was calculated from s 0 = d[E a /(2m)] À1/2 , valid for a sinusoidal barrier shape between lithium ion sites, where d is the separation between neighboring lithium ion sites and m is the mass of the mobile ion.…”

On structural transitions in a discontinuous micellar cubic phase loaded with sodium diclofenac

“…5b). A significant decrease in the diffusion coefficients is expected once phase transitions occur as in the transition from cubic to hexagonal phase [67]. Ström and Anderson [68] observed discontinuous decreases in the water diffusion coefficient with the transitions between the G-and D-phases and between the D-and P-phases.…”

“…Ström and Anderson [68] observed discontinuous decreases in the water diffusion coefficient with the transitions between the G-and D-phases and between the D-and P-phases. The decrease in the diffusion coefficients was related to the microscopic molecular displacements (so-called 'obstruction factor') [67,69].…”