Using Sodium Cation Organization To Study the Phase Behavior of Bicelle Solutions

Abstract

The 23 Na nuclear magnetic resonance (NMR) spectra for NaCl dissolved in the nematic phase of dimyristoylphosphatidylcholine (DMPC)/dihexanoyl-phosphatidylcholine (DHPC) bicelle solutions at 34°C display line splittings consistent with the quadrupolar satellite transitions for the I ) 3 / 2 23 Na nucleus. At temperatures exceeding 40°C additional residual 23 Na satellite transition lines develop, suggesting that a new ordered phase similar to pure DMPC is present.

Bicelles as model membranes for solid‐ and solution‐state NMR studies of membrane peptides and proteins

“…The formation of MLVs is observed at low lipid concentration or elevated temperature. This structural diagram is consistent with previous studies performed at similar q ratios and sample conditions (37,56,77). Figure 4(b) highlights the effect of negatively charged DMPG in bicelles.…”

Sodium MRI: Methods and applications

“…The Augustine model [71–73], for example, also describes the important case of sodium ions in the vicinity of polyelectrolytes. In this case, relaxation is induced by the diffusion motion of the ions within the EFG generated by the polyelectrolytes.…”

Nuclear spin relaxation of sodium cations in bacteriophage Pf1 solutions

“…In addition to providing a measurable change in the electrical properties of the solution probed by the ͗ rod ͘ and ͑͗ rod 2 ͘ − ͗ rod ͘ 2 ͒J rod ͑0͒ contributions to the 23 Na NMR signal, the Pf1 has the added effect of increasing the bulk viscosity of water and of course changing the hydrogen bonding capacity and ultimately the dielectric constant of water. 19,27 Therefore, although there is an isotropic contribution to the 23 Na relaxation, it is not reasonable to expect that this background relaxation compare to a similar solution with the same sodium ion concentration without Pf1.…”

“…25,26 It is the presence of this type of potential, or more specifically the corresponding macroscopic field gradient ٌ 2 V͑r͒, that leads to residual quadrupolar couplings in the one dimensional spectra for I Ͼ 1 / 2 nuclei dissolved into aqueous phase liquid crystals with building blocks that are massive in comparison with the free ion size. 19,27,28 In addition, translational diffusion of the I Ͼ 1 / 2 nuclear spins in the macroscopic field gradient ٌ 2 V͑r͒ can lead to relaxation. The difference in time scale between the processes responsible for the relaxation in isotropic phase mentioned above and the effect of one dimensional translational diffusion in the macroscopic field gradient ٌ 2 V͑r͒ suggests that the effects of these two types of relaxation can be treated separately.…”

“…4. 11,20,25 19,27 a numerical solution to Eq. ͑4.1͒ must be used to determine V͑r͒ and thus the gradient V rr ͑r͒ = ٌ 2 V͑r͒ = ͑1/r͒ ‫ץ͑‬ / ‫ץ‬r͒ ͑r‫ץ‬V͑r͒ / ‫ץ‬r͒, the critical parameter in the laboratory frame spin Hamiltonian,…”