title: Influence of lipid lateral distribution on the surface charge response of the phosphatidylcholine headgroup as detected using 2H nuclear magnetic resonance.
abstract: The effect of lipid lateral distribution on the surface charge response of the phosphatidylcholine headgroup, in bilayers composed of binary mixtures of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and 1,2-dimyristoyl-sn-glycero-3-phosphate (DMPA), was investigated by monitoring the deuterium nuclear magnetic resonance (2H-NMR) spectrum of choline-deuterated phosphatidylcholine as a function of temperature and DMPA concentration. Addition of DMPA at temperatures corresponding to fully liquid-crystalline membranes caused a progressive increase (decrease) in the 2H-NMR quadrupole splitting from POPC-alpha-d2 (POPC-beta-d2), in agreement with the known response of phosphatidylcholine to negative membrane surface charge (Seelig, J., Macdonald, P.M. and Scherer, P.G. (1987) Biochemistry 26, 7535-7541). Lateral phase separation of DMPA-rich domains was induced in these mixtures by lowering the temperature in the range from 60 degrees C to -15 degrees C, and was accompanied by a reversal of the original effects of DMPA on the quadrupole splitting. Analysis of the 2H-NMR spectral response allows one to generate a temperature/composition phase diagram for the POPC/DMPA system. We conclude that 2H-NMR of headgroup-deuterated phosphatidylcholine can be employed to sense and to quantify inhomogeneities in the lateral distribution of charged membrane components.
authors.affiliation: Department of Chemistry, University of Toronto, Ontario, Canada.
authors.forename: F M
authors.initials: FM
authors.lastname: Marassi
authors.forename: S
authors.initials: S
authors.lastname: Djukic
authors.forename: P M
authors.initials: PM
authors.lastname: Macdonald
mesh_terms: D000814:Aniline Compounds; D002152:Calorimetry, Differential Scanning; D003903:Deuterium; D009682:Magnetic Resonance Spectroscopy; D010713:Phosphatidylcholines / Q000737:chemistry*; D013696:Temperature
chemical_list: D000814:Aniline Compounds; D010713:Phosphatidylcholines; C050795:N,N-dimethyl-4-anisidine; D003903:Deuterium; C028694:1-palmitoyl-2-oleoylphosphatidylcholine