Ca sup 2+ , Mg sup 2+ , Li sup + , Na sup + , and K sup + distributions in the headgroup region of binary membranes of phosphatidylcholine and phosphatidylserine as seen by deuterium NMR

Journal Article · Tue Jul 31 00:00:00 EDT 1990 · Biochemistry; (USA)

DOI:https://doi.org/10.1021/bi00482a019· OSTI ID:6276728

Roux, M; Bloom, M ^[1]

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1. Univ. of British Columbia, Vancouver (Canada)

The binding of calcium, magnesium, lithium, potassium, and sodium to membrane bilayers of 5 to 1 (M/M) 1-palmitoyl-2-oleoylphosphatidylcholine (POPC) and 1-palmitoyl- 2-oleoylphosphatidylserine (POPS) was investigated by using deuterium nuclear magnetic resonance (2H NMR). Both lipids were deuteriated on their polar headgroups, and spectra were obtained at 25 degrees C in the liquid-crystalline phase as a function of salt concentration. The spectra obtained with calcium were correlated with 45CaCl2 binding studies to determine the effective membrane-bound calcium at low calcium binding, up to 0.78 calcium per POPS. Deuterium quadrupolar splittings of both POPC and POPS headgroups were shown to be very sensitive to calcium binding. The behavior of these two headgroups over a wide range of CaCl2 concentrations suggests that Ca2+ binding occurs in at least two steps, the first step being achieved with 0.5 M CaCl2, with a stoichiometry of 0.5 Ca2+ per POPS. Correlations of the deuterium Ca2+ binding data with related data obtained after incorporation of a cationic integral peptide showed that the effects of these two cationic molecules of the POPS headgroup are qualitatively similar, and provided further support for two-step Ca2+ binding to the POPC/POPS 5:1 membranes. The corresponding data obtained with magnesium, lithium, and potassium indicate that these cations interact with both the choline and serine headgroups. The amplitudes of headgroup perturbations could be partly correlated to the relative affinities of the metallic cations for the lipid membrane. The two-step binding described with Ca2+ appears to be relevant to the Mg2+ data, and in certain limits to the Li+ data. The data were interpreted in terms of conformational changes of the lipid headgroups induced by an electric field due to the charges of the membrane-bound metallic cations.

• OSTI ID: 6276728
• Journal Information: Biochemistry; (USA), Vol. 29:30; ISSN 0006-2960
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
CALCIUM COMPOUNDS
BIOCHEMICAL REACTION KINETICS
LITHIUM COMPOUNDS
MAGNESIUM COMPOUNDS
PHOSPHOLIPIDS
DEUTERATION
POTASSIUM COMPOUNDS
SODIUM COMPOUNDS
CALCIUM 45
CATIONS
CELL MEMBRANES
DEUTERIUM
MEMBRANE PROTEINS
NMR SPECTRA
NUCLEAR MAGNETIC RESONANCE
RECEPTORS
STOICHIOMETRY
TRACER TECHNIQUES
ALKALI METAL COMPOUNDS
ALKALINE EARTH ISOTOPES
ALKALINE EARTH METAL COMPOUNDS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CALCIUM ISOTOPES
CELL CONSTITUENTS
CHARGED PARTICLES
CHEMICAL REACTIONS
DAYS LIVING RADIOISOTOPES
ESTERS
EVEN-ODD NUCLEI
HYDROGEN ISOTOPES
INTERMEDIATE MASS NUCLEI
IONS
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LIGHT NUCLEI
LIPIDS
MAGNETIC RESONANCE
MEMBRANES
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANIC PHOSPHORUS COMPOUNDS
PROTEINS
RADIOISOTOPES
REACTION KINETICS
RESONANCE
SPECTRA
STABLE ISOTOPES
550201* - Biochemistry- Tracer Techniques