The effects of Ca 2+ on lipid diffusion

• Published in: Chemistry and physics of lipids Vol. 41; no. 3; pp. 183 - 194
• Main Authors: Blatt, Edward, Vaz, Winchil L.C.
• Format: Journal Article
• Language: English
• Published: Elsevier Ireland Ltd 01.10.1986
• Subjects: Ca 2+ binding; fluorescence; lipid diffusion; phosphorescence; lipid diffusion; T m; fluorescence; E12; phosphorescence; Ca 2+ binding; D t; NBD-PE; FRAP; DMPC; DPH; DPPC
• DOI: 10.1016/0009-3084(86)90021-6
• ISSN: 0009-3084

The effects of Ca 2+ on rotational and translational diffusion of lipids in multilamellar dimyristoylphosphatidylcholine (DMPC)-water systems were investigated by time-resolved phosphorescence anisotropy, steady-state fluorescence polarization and fluorescence recovery after photobleaching (FRAP) experiments. Above the phase transition temperature ( T m ), addition of Ca 2+ caused a steady increase in the segmental motion of the phosphorescent probe, but resulted in slower diffusion of the fluorescent and lateral diffusion probes. The former result is attributed to changes in the structure of the lipid/water interface that affects the chromophore mobility on the phosphorescence time scale but does not reflect lipid motion. Below the phase transition temperature, slower diffusion of all probes were observed with increasing concentrations of Ca 2+, with sudden large changes occurring at [Ca 2+] ∼ 500 mM. This behaviour is attributed to association of Ca 2+ with the lipid phosphate groups and the exclusion of water molecules which results in tighter packing of lipids and smaller segmental motion, leading eventually to the immobilization of lipid molecules.