scholarly journals Labelling of egg phosphatidylcholine vesicles and myelin membrane with a photoreactive lipophilic reagent

1977 ◽  
Vol 161 (2) ◽  
pp. 223-228 ◽  
Author(s):  
K M Abu-Salah ◽  
J B C Findlay
Keyword(s):  
Lipid Bilayer ◽  
Fatty Acyl ◽  
Phenyl Azide ◽  
Myelin Membrane ◽  
Polar Head ◽  
Head Groups ◽  
Polar Probe

The preparation and isolation of [3H]phenyl azide, a photosensitive non-polar probe, is reported. The reagent partitions into the lipid bilayer of egg phosphatidylcholine vesicles and bovine myelin membranes. On photoactivation to generate the nitrene grouping, as much as 90% of the covalently attached label is associated with the fatty acyl residues of the constituent phospholipid molecules. The remainder is found in the polar head groups. The cholesterol component of myelin membranes is also heavily labelled. These results suggest that such reagents may be used to probe the hydrophobic regions of natural membranes.

scholarly journals Influence of polar head groups on the gel to liquid-crystal transition in vesicular and lipid bilayer systems

1996 ◽  
Vol 92 (17) ◽  
pp. 3163 ◽  
Author(s):  
Michael J. Blandamer ◽  
Barbara Briggs ◽  
Paul M. Cullis ◽  
Jan B. F. N. Engberts ◽  
Robert I. Norman
Keyword(s):  
Liquid Crystal ◽  
Lipid Bilayer ◽  
Polar Head ◽  
Head Groups ◽  
Crystal Transition ◽  
Liquid Crystal Transition

Microstructural morphology of sphingolipid dispersions as investigated by freeze-fracture EM

1995 ◽  
Vol 53 ◽  
pp. 944-945
Author(s):  
Vitthal S. Kulkarni ◽  
Wayne H. Anderson ◽  
Rhoderick E. Brown
Keyword(s):  
Acyl Chain ◽  
Biological Significance ◽  
Freeze Fracture ◽  
Fatty Acyl ◽  
Fatty Acyl Moiety ◽  
Aqueous Dispersions ◽  
Head Groups ◽  
Lipid Species ◽  
Microstructural Morphology ◽  
Layer Chromatography

The biological significance of the sphingomyelins (SM) and monoglycosylated sphingolipids like galactosylceramides (GalCer) are well documented Our recent investigation showed tubular bilayers in the aqueous dispersions of N-nervonoyl GalCer [N-(24:lΔ15,cls) GalCer] (a major fatty acyl moiety of natural GalCer). To determine the influence of lipid head groups on the resulting mesophasic morphology, we investigated microstructural self-assemblies of N-nervonoyl-SM [N-(24:1 Δ15,cls) SM; the second most abundant sphingomyelin in mammalian cell membranes], 1- palmitoyl-2-nervonoyl phosphatidylcholine [PNPC] (the lipid species with the same acyl chain configuration as in N-(24: 1) GalCer) and also compared it with egg-SM by freeze-fracture EM.Procedures for synthesizing and purifying N-(24:1) GalCer, N-(24:1) SM, and PNPC have been reported . Egg-SM was purchased from Avanti Polar Lipids, Alabaster AL. All lipids were >99% pure as checked by thin layer chromatography. Lipid dispersions were prepared by hydrating dry lipid with phosphate buffer (pH 6.6) at 80-90°C (3-5 min), vigorously vortexing (1 min) and repeating this procedure for three times prior to three freeze-thaw cycles.

Polar head groups are important for barrier-protective effects of oxidized phospholipids on pulmonary endothelium

2007 ◽  
Vol 292 (4) ◽  
pp. L924-L935 ◽  
Author(s):  
Anna A. Birukova ◽  
Panfeng Fu ◽  
Santipongse Chatchavalvanich ◽  
Dylan Burdette ◽  
Olga Oskolkova ◽  
...  
Keyword(s):  
Protective Effects ◽  
Oxidized Phospholipids ◽  
Barrier Dysfunction ◽  
Polar Head ◽  
Cell Counts ◽  
Head Groups ◽  
Stimulation Of

We have previously described protective effects of oxidized 1-palmitoyl-2-arachidonoyl- sn-glycero-3-phosphocholine (OxPAPC) on pulmonary endothelial cell (EC) barrier function and demonstrated the critical role of cyclopentenone-containing modifications of arachidonoyl moiety in OxPAPC protective effects. In this study we used oxidized phosphocholine (OxPAPC), phosphoserine (OxPAPS), and glycerophosphate (OxPAPA) to investigate the role of polar head groups in EC barrier-protective responses to oxidized phospholipids (OxPLs). OxPAPC and OxPAPS induced sustained barrier enhancement in pulmonary EC, whereas OxPAPA caused a transient protective response as judged by measurements of transendothelial electrical resistance (TER). Non-OxPLs showed no effects on TER levels. All three OxPLs caused enhancement of peripheral EC actin cytoskeleton. OxPAPC and OxPAPS completely abolished LPS-induced EC hyperpermeability in vitro, whereas OxPAPA showed only a partial protective effect. In vivo, intravenous injection of OxPAPS or OxPAPC (1.5 mg/kg) markedly attenuated increases in the protein content, cell counts, and myeloperoxidase activities detected in bronchoalveolar lavage fluid upon intratracheal LPS instillation in mice, although OxPAPC showed less potency. All three OxPLs partially attenuated EC barrier dysfunction induced by IL-6 and thrombin. Their protective effects against thrombin-induced EC barrier dysfunction were linked to the attenuation of the thrombin-induced Rho pathway of EC hyperpermeability and stimulation of Rac-mediated mechanisms of EC barrier recovery. These results demonstrate for the first time the essential role of polar OxPL groups in blunting the LPS-induced EC dysfunction in vitro and in vivo and suggest the mechanism of agonist-induced hyperpermeability attenuation by OxPLs via reduction of Rho and stimulation of Rac signaling.

Enzymatic Preparation of Phospholipids Containing Various Polar Head Groups

1990 ◽  
Vol 613 (1 Enzyme Engine) ◽  
pp. 686-690 ◽  
Author(s):  
TSUNEO YAMANE ◽  
LEKH RAJ JUNEJA ◽  
DONGXIU LI ◽  
SHOICHI SHIMIZU
Keyword(s):  
Enzymatic Preparation ◽  
Polar Head ◽  
Head Groups

Self-assembled structures formed by a wedge-shaped molecule in 2D and 3D: the role of flexible side chains and polar head groups

2010 ◽  
Vol 12 (7) ◽  
pp. 1444-1452 ◽  
Author(s):  
Xiaomin Zhu ◽  
Ahmed Mourran ◽  
Uwe Beginn ◽  
Martin Möller ◽  
Denis V. Anokhin ◽  
...  
Keyword(s):  
Side Chains ◽  
Polar Head ◽  
Head Groups ◽  
Self Assembled ◽  
2D And 3D

Human Coagulation Factor Va Interaction with Phospholipid Vesicles: A Molecular Dynamics Study.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 1699-1699
Author(s):  
Tivadar Orban ◽  
Michael Kalafatis
Keyword(s):  
Amino Acid ◽  
Lipid Bilayer ◽  
Factor Xa ◽  
Accessible Surface Area ◽  
Fatty Acyl ◽  
Phospholipid Bilayer ◽  
Solvent Accessible Surface Area ◽  
Factor Va ◽  
Accessible Surface ◽  
Simulation Time

Abstract The prothrombinase complex, the enzyme responsible for the timely conversion of prothrombin to thrombin, is composed of factor Xa (the enzyme), factor Va (the cofactor) assembled on the activated cell surface in the presence of divalent metal ions. In our quest to propose a model of the prothrombinase complex we first created a homology model in solution of factor Va (pdb code 1y61). Next we created a mixed phospholipid bilayer model composed of 1-palmitoyl, 2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC) and 1-palmitoyl, 2-oleoyl-sn-glycero-3-phosphatidylserine (POPS) in a 4:1 ratio. The lipid bilayer was equilibrated for 10 ns. The data showed that the average area per head group and the deuterium order parameters of the fatty acyl chains compare well with the previously reported nuclear magnetic resonance data. We next created a system composed of factor Va, water molecules, phospholipid bilayer composed of POPS/POPC and sodium ions. Factor Va was placed at the near interface of the equilibrated POPC/POPS phospholipid bilayer but making sure that the two entities were not interacting. Molecular dynamics simulation was then performed on the entire system. Distance analysis performed between the center of masses of the factor Va molecule and the lipid bilayer revealed that during the 4.5 ns simulation time, the factor Va molecule gets inserted into the interface of the hydrophobic core of the bilayer. The distance between the two centers of masses decreased during the 4.5 ns simulation time from 92 Å to 78 Å. At the end of the 4.5 ns simulation time the indole moieties of Trp2063 and Trp2064 were found to be in the vicinity of the ester and the fatty acyl chain moieties of the phospholipids. Factor Va was found to participate in hydrogen bonds formation with both the carboxylate and the phosphate groups of POPS. Following 4.5 ns simulation time the farthest amino acid residue away from the membrane is located at ~ 100 Å from the lipid bilayer plane. This result is in agreement with previous fluorescence energy transfer studies that concluded that a domain of membrane-bound factor Va is positioned at a minimum distance of 90 Å above the membrane surface. It is noteworthy that the amino acid sequence comprising Pro1663 to Val1672 of factor Va had a root mean square displacemenent (RMSD) 4.5 times higher as the average RMSD of the other residues, i.e., 9 Å. This sequence is highly hydrophobic in nature and it was previously shown to contain a membrane binding site on factor Va. However, the present placement of factor Va on the lipid bilayer does not allow the insertion of this hydrophobic patch into the lipid bilayer. We next tested the hypothesis whether the region encompassing amino acid residues Glu323 to Val331 gets exposed to solvent following the interaction of factor Va with the phospholipids. This region was shown to contain a binding site of factor Xa on factor Va. Solvent accessible surface area calculated for each amino acid residue of the Glu323 to Val331 sequence revealed that during the 4.5 ns simulation time the solvent accessible surface area does not increase. In conclusion, our work proposes for the first time a model of factor Va bound to a mixed POPC/POPS lipid bilayer and provides the necessary framework that accounts for the presence of phospholipids as a major regulatory component of a protein complex. This model can be extrapolated to the study of the dynamics of other membrane associated complexes involved in blood coagulation.

scholarly journals Biosynthesis of Ether-Type Polar Lipids in Archaea and Evolutionary Considerations

2007 ◽  
Vol 71 (1) ◽  
pp. 97-120 ◽  
Author(s):  
Yosuke Koga ◽  
Hiroyuki Morii
Keyword(s):  
Mevalonate Pathway ◽  
Polar Lipids ◽  
In Vivo Studies ◽  
Head Group ◽  
Polar Head Group ◽  
Phospholipid Synthesis ◽  
Polar Head ◽  
Head Groups

SUMMARY This review deals with the in vitro biosynthesis of the characteristics of polar lipids in archaea along with preceding in vivo studies. Isoprenoid chains are synthesized through the classical mevalonate pathway, as in eucarya, with minor modifications in some archaeal species. Most enzymes involved in the pathway have been identified enzymatically and/or genomically. Three of the relevant enzymes are found in enzyme families different from the known enzymes. The order of reactions in the phospholipid synthesis pathway (glycerophosphate backbone formation, linking of glycerophosphate with two radyl chains, activation by CDP, and attachment of common polar head groups) is analogous to that of bacteria. sn-Glycerol-1-phosphate dehydrogenase is responsible for the formation of the sn-glycerol-1-phosphate backbone of phospholipids in all archaea. After the formation of two ether bonds, CDP-archaeol acts as a common precursor of various archaeal phospholipid syntheses. Various phospholipid-synthesizing enzymes from archaea and bacteria belong to the same large CDP-alcohol phosphatidyltransferase family. In short, the first halves of the phospholipid synthesis pathways play a role in synthesis of the characteristic structures of archaeal and bacterial phospholipids, respectively. In the second halves of the pathways, the polar head group-attaching reactions and enzymes are homologous in both domains. These are regarded as revealing the hybrid nature of phospholipid biosynthesis. Precells proposed by Wächtershäuser are differentiated into archaea and bacteria by spontaneous segregation of enantiomeric phospholipid membranes (with sn-glycerol-1-phosphate and sn-glycerol-3-phosphate backbones) and the fusion and fission of precells. Considering the nature of the phospholipid synthesis pathways, we here propose that common phospholipid polar head groups were present in precells before the differentiation into archaea and bacteria.

scholarly journals The Acceptor for Polar Head Groups of the Lipid A Component of Salmonella Lipopolysaccharides

1978 ◽  
Vol 86 (2) ◽  
pp. 487-496 ◽  
Author(s):  
Volker LEHMANN ◽  
John REDMOND ◽  
Aubrey EGAN ◽  
Inge MINNER
Keyword(s):  
Lipid A ◽  
Polar Head ◽  
Head Groups
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