Syntheses of 1,2-di-O-palmitoyl-sn-glycero-3-phosphocholine (DPPC) and analogs with 13C- and 2H-labeled choline head groups

Effect of deuteration on the phase behaviour and structure of lamellar phases of phosphatidylcholines - Deuterated lipids as proxies for the physical properties of native bilayers

Deuteration of phospholipids is a common practice to elucidate membrane structure, dynamics and function, by providing selective visualisation in neutron scattering, nuclear magnetic resonance and vibrational spectroscopy. It is generally assumed that the properties of the deuterated lipids are identical to those of the protiated lipids, and while a number of papers have compared the properties of different forms, to date this has been no systematic study of the effects over a range of conditions. Here we present a study of the effects of deuteration on the organisation and phase behaviour of four common phospholipids (DSPC, DPPC, DMPC, DOPC), observing the effect of chain deuteration and headgroup deuteration on lipid structure and phase behaviour. For saturated lipids in excess water the gel-fluid phase transition temperature is 4.3 ± 0.1 °C lower for lipids with deuterated chains compared to protiated chains, consistent with previous work. Despite this significant change, well away from the transition structural changes as measured by powder small angle X-ray scattering are small and within errors. To investigate this further, measurements were carried out on oriented multilamellar stacks of DOPC in the fluid phase at reduced hydration. Neutrons are used in conjunction with contrast variation to elucidate the role of the deuteration explicitly. It is found that deuterated chains cause a reduction in the lamellar repeat spacing and bilayer thickness, but deuterated headgroups cause an increase. Consequences for the interpretation of Neutron Scattering data with deuterated lipids are discussed.

Synthesis of Perdeuterated 1-Palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine ([D82 ]POPC) and Characterisation of Its Lipid Bilayer Membrane Structure by Neutron Reflectometry

1-Palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), an unsaturated acyl chain containing lipid, is often the predominant lipid in eukaryotic cell membranes in which it is crucial for the fluidity of membranes under physiological conditions. Commercially available, partially deuterated [D₃₁ ]1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine ([D₃₁ ]POPC) does not provide sufficient isotopic contrast for detailed structural studies of multicomponent membranes through neutron techniques. Herein, a relatively straightforward and generic chemical deuteration method is discussed for the asymmetric synthesis of perdeuterated [D₃₁ ]1-palmitoyl-[D₃₃ ]2-oleoyl-sn-[D₅ ]glycero-[D₁₃ ]3-phosphocholine ([D₈₂ ]POPC) that also allows selective deuteration of any of its constituent groups. Neutron reflectivity of a [D₈₂ ]POPC-supported bilayer was used to experimentally determine the neutron scattering length density profile of the lipid. The acyl chains of [D₈₂ ]POPC are closely contrast-matched to heavy water, whereas the very high scattering length density of the deuterated glycerophosphocholine head groups provides good contrast to membrane-binding agents in both deuterated and non-deuterated solvent environments.

An LC method for the analysis of phosphatidylcholine hydrolysis products and its application to the monitoring of the acyl migration process

An assay for quantitative analysis of phosphatidylcholine (1,2-dipalmitoyl-sn-glycero-3-phosphocholine) and its hydrolysis products: 1-hydroxy-2-palmitoyl-sn-glycero-3-phosphocholine and 1-palmitoyl-2-hydroxy-sn-glycero-3-phosphocholine, sn-glycero-3-phosphocholine and palmitic acid using high-performance liquid chromatography with charge aerosol detector (CAD) was developed. The separation of the compounds of interest was achieved on a reversed-phase/hydrophilic interaction stationary phase with a mobile phase consisting of acetonitrile:methanol:10mM ammonium acetate solution. The method was applied to control the acyl migration process of LPC regioisomers in the most common solvents used in the synthesis or modification of PC.

The total synthesis of 2-O-arachidonoyl-1-O-stearoyl-sn-glycero-3-phosphocholine-1,3,1'-(13)C3 and -2,1'-(13)C2 by a novel chemoenzymatic method

2-O-Arachidonoyl-1-O-stearoyl-sn-glycero-3-phosphocholine was synthesized with carbon-13 enrichment of the three glycerol carbons and the carbonyl of the stearoyl group. Phospholipase A(2) was utilized to give optically pure lyso-PC, and only 3% acyl migration occurred during reacylation with arachidonic acid anhydride. This phospholipid is an important biosynthetic precursor of arachidonic acid metabolites as well as the endocannabinoid 2-arachidonoylglycerol (2-AG), and is now available for NMR studies.