Effect of NaCl and CaCl2 on the lateral diffusion of zwitterionic and anionic lipids in bilayers

The influence of addition of NaCl or CaCl2 (0.3 and 0.1M, respectively) on the lateral diffusion coefficient (DL) of dioleoylphosphatidylcholine (DOPC) or dioleoylphosphatidylglycerol (DOPG) was measured by the pulsed field gradient NMR technique. DL of DOPC was unaffected, whereas the DOPG diffusion decreased with salt concentration. 23Na NMR quadrupole splittings of DOPG between 20 and 60°C and added NaCl between 0 and 15wt% decreased only slightly with salt content, but increased with increasing temperature. Similar results were obtained for palmitoyloleoylphosphatidylglycerol, in which the palmitoyl chain order parameter increased slightly with salt. A model with free and “bound” ions was used to interpret the splitting data.