Bilayers of phosphatidylserine: a deuterium and phosphorus nuclear magnetic resonance study

Abstract

The structure and motion of the phosphatidylserine molecule in bilayers have been studied with deuterium and phosphorus-3 1 nuclear magnetic resonance. The phase behavior and the thermodynamic properties of phosphatidylserine were further characterized by means of spin-label electron paramagnetic resonance and differential scanning calorimetry. 1.2-Dipalmitoyl-, 1,2-dimyristoyl-, and 1,2-dioleoyl-snglycero-3-phosphoserine were selectively deuterated in the fatty acyl chains, in the glycerol backbone, and in both the 2 and 3 segments of the serine moiety. The residual deuterium quadrupole couplings and the phosphorus-3 1 chemical shielding anisotropy of lipid-water mixtures a t pH 7.0 in the absence of divalent cations were measured as a function of temperature and provided quantitative data on segmental motions of the serine head group, the phosphate linkage, the glycerol backbone, and the hydrocarbon region. The N M R data of phosphatidylserine are compared with those previously obtained for phosphatidylcholine and phosphatidylethanolamine. Qualitative and quantitative agreement exists for the ordering of the fatty acyl chains of all these lipids. In particular, in all phospholipids, the sn-2 chain is bent at the C-2 segment. The bilayer thickness as calculated from the deuterium N M R data is similar to that of phosphatidylcholine. The deuterium magnetic resonance spectra of the C-3 deuPhosphatidylserine is an interesting lipid in biological membranes. Primarily, this phospholipid can bind calcium to its head group, resulting in a broadening and a shift to higher temperatures of the gel to liquid-crystalline phase transition in pure phosphatidylserine membranes (Jacobson & Papahadjopoulos, 1975). This could be important in biological systems because this property would allow for a relatively fast change in the lipid phase a t a constant temperature. Work on phosphatidylserine in model systems has been mainly concerned with macroscopic properties of natural brain phosphatidylserine, i.e., bilayer lamellar spacings as studied with X-ray diffraction, electron micrographs of lamellar structures, phase transition temperatures, electrophoretic mobilities, monolayer properties, and extensive studies on ion binding. More microscopic properties such as chain ordering or head group structure and motion have not been studied. Compared with the extensive literature for phosphatidylcholine and phosphatidylethanolamine, there is a lack of physical data on synthetic phosphatidylserines. This deficiency has probably been due to the difficulty of the phosphatidylserine synthesis and the more complicated purification techniques required. Phosphatidylserine is also much less stable than either phosphatidylcholine or phosphatidylethanolamine. This instability is especially noticeable with DPPS;' the high transition temperature of 53 "C forces one to measure at temperatures where From the terated glycerol backbone of 1,2-dipalmitoyl-and 1,2-dioleoyl-sn-glycero-3-phosphoserine are similar to those of 1.2-dipalmitoyl-sn-glycero-3-pho...

Weak interaction of spectrin with phosphatidylcholine‐phosphatidylserine multilayers: A 2H and 31P NMR study

“…The presence of charged lipids such as DMPS [28], of ions [36] or of charged anaesthetics [37] near the deuterated head group of DMPC strongly modifies its conformation, as a result of the perturbation of the bilayer surface charge [43]. Partial neutralization or screening of DMPS charges by positive charges at the membrane surface allows the DMPC head group to recover its original conformation [22].…”

“…The head group deuterated DMPC is a mixture of DMPC-& and DMPC-ds (9: 1, w/w). The spectrum from the protein-free dispersions ( fig.3a) shows three distinct quadrupolar splittings, the internal one (0.8 kHz) corresponding to the deuterons of the N(CD+ groups of DMPC-ds, the intermediate splitting (2.4 kHz) from the deuterons in &positions of DMPC-&, while the largest splittings partially resolved into two splittings (7.8 and 8.6 kHz) correspond to the two deuterons in cY-position of DMPC-& [28]. The magnitude of these splittings is unaffected by bound spectrin ( fig.3b) although the spectral lines are narrower in the presence of spectrin.…”

“…Deuterium NMR spectra at 35°C of head group deuterated DMPS-d3 mixed with DMPC (1: 1, w/w) ( fig.4a) show three resolved quadrupolar splittings, the two inner ones (2.8 and 9.7 kHz, respectively) corresponding to the deuterons in the a-position of the serine head group, and the larger one (14 kHz) corresponding to the deuteron in ,& position [28]. Again, there is no observable effect of the incorporation of spectrin on the magnitude of these splittings ( fig.4b).…”

Thermodynamic study of benzocaine insertion into different lipid bilayers

“…Experimentally, −S CD can be calculated from H-NMR experiments of specific deuterated methylene groups along the hydrocarbon lipid tails with the axis normal to the lipid bilayer. 17,41,42 By simulation, the order parameters may be calculated from the methylene hydrogen orientation with respect the z-axis normal to …”

Polyethylene glycols interact with membrane glycerophospholipids: is this part of their mechanism for hypothermic graft protection?

“…Each lipid has its specific transition temperature at which the acyl chains undergo dramatic conformational change [27]. So, in bilayers at neutral pH, DPPC, DPPS, and DPPE have shown a phasetransition temperature of, respectively, 41.4°C, 53°C, and 63°C while SOPC monounsaturated glycerophospholipids have shown a transition temperature of 5.6°C [28][29][30][31]. In addition, it has been demonstrated that PEG increases the phase-transition temperature of glycerophospholipids, possibly by changing the solvation property of water [32][33][34].…”