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At least 487 records · Page 27Linked to original sources
PubMed1993

[PAF-antagonists with a phospholipid structure. 5. Propanediol phospholipids with various substituted pyridinium and quinuclidinium head groups and variations of the phosphorus-nitrogen distance;synthesis, characterization and structure activity relationship].

A series of 10 PAF-analogues, structurally modified in position C-2 (n-propyl) and position C-3 (polar head group) were synthesized, and the PAF-inhibitory potencies was evaluated using PAF-induced aggregation of human blood platelets in vitro. Structure-activity relationships revealed, that the PAF-inhibitory activity is strongly influenced by the distance between phosphate and onium center and the structure of the substituted heterocyclus. The best activity was observed by 3,5-dimethylpyridinium- and 4-ethylpyridinium derivative with a P-N-distance of 6 methylene groups (IC50 = 1.9 x 10(-6) mol/l and 2.7 x 10(-6) mol/l).

Blood Platelets↗
PubMed1984

Covalent linkage of a synthetic peptide to a fluorescent phospholipid and its incorporation into supported phospholipid monolayers.

A number of fluorescent peptide-lipid conjugates have been synthesized. Peptides with ten or eleven amino acids are linked through a single lysine residue to the headgroup of phosphatidylethanolamine, fluorescently labelled on one acyl chain, using homobifunctional disuccinimidyl crosslinking reagents. Peptide-lipids can be further derivatized with the hapten dinitrophenyl. Purified peptide-lipids have been incorporated into dimyristoylphosphatidylcholine monolayers at the interface of air and phosphate-buffered saline, at concentrations of up to 11 mol%. For equal average molecular areas, monolayers containing peptide-lipids have higher surface pressures than pure lipid monolayers; for equal surface pressures, peptide-lipid monolayers have higher average molecular areas than pure lipid monolayers. When the peptide-lipid monolayers are transferred to hydrophobic glass slides, the fluorescence appears uniformly distributed. Fluorescence recovery after photobleaching measurements indicate that peptide-lipids diffuse in the monolayer with coefficient 1.5 X 10(-9) cm2/s, which is much smaller than that of typical lipids in fluid membranes. In addition, the diffusion coefficient of peptide-lipids decreases with increasing peptide-lipid concentration. We conclude that the peptide portion of the peptide-lipid associates with the lipid monolayer and/or that peptide-lipids oligomerize.

4-Chloro-7-nitrobenzofurazan↗
PubMed1990

Calcium-induced lipid phase separations and interactions of phosphatidylcholine/anionic phospholipid vesicles. Fluorescence studies using carbazole-labeled and brominated phospholipids.

A novel method that uses a carbazole-labeled fluorescent phosphatidylcholine, which partitions preferentially into liquid-crystalline lipid domains, to monitor the kinetics and the extents of thermotropic and ionotropic lateral phase separations in vesicles combining brominated and nonbrominated phosphatidylcholines (PCs), phosphatidic acids (PAs), and phosphatidylserines (PSs) is described. The calcium-induced segregation of several nonbrominated PA species in liquid-crystalline brominated PC bilayers behaves as a well-defined lateral phase separation; the residual solubility of the PA component in the PC-rich phase in the presence of calcium can vary severalfold depending on the PA acyl chain composition. PC/PS mixtures show a pronounced tendency to form metastable solutions in the presence of calcium, particularly when they contain less than equimolar proportions of PS. This metastability is not readily relaxed by repeated freeze-thawing of vesicles in the presence of calcium, by avidin-mediated contacts between PC/PS vesicles containing biotinylated lipids, or by calcium-induced lateral segregation of PA in the same vesicles. Different PS species exhibit different apparent residual solubilities in liquid-crystalline PC bilayers, ranging from less than 10 mol % for dimyristoyl-PS to ca. 45 mol% for dioleoyl-PS, after prolonged incubations of PC/PS multilamellar vesicles with excess calcium. Results are presented, obtained by using the above lipid-segregation assay and parallel assays of intervesicle lipid mixing, that raise questions concerning the relevance of the equilibrium behavior of calcium-treated PS/PC mixtures to the relatively rapid interactions (fusion and lipid mixing) of PC/PS vesicles that follow initial exposure to calcium.

Bromine↗
PubMed1990

Phospholipids chiral at phosphorus. Dramatic effects of phosphorus chirality on the deuterium NMR properties of the choline head group of phospholipids in the liquid crystalline phase.

To probe the motional and conformational properties of the choline head group of 1,2-dipalmitoyl-sn-glycero-3-thiophosphocholine (DPPsC), the Rp, Sp, and Rp + Sp isomers of [alpha-D2]DPPsC, [beta-D2]DPPsC, and [delta-D9]DPPsC in the subgel, gel, and liquid crystalline phases were investigated with deuterium NMR, and the results were compared with those of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) labeled at the same positions. In the subgel phase (5 degrees C) all isomers of [alpha-D2]DPPsC and [beta-D2]DPPsC displayed amorphous line shapes characteristic of a restricted and disordered motional environment, whereas [delta-D9]DPPsC showed narrower and symmetric line shapes indicating substantial motions. For all three labeled positions the apparent line width of the Rp isomer is larger than those of Sp and Rp + Sp isomers, and the amorphous line shape of the Rp isomer also persists at 25 and 35 degrees C, which confirm the previous observation that the Rp isomer is unusually stable in the subgel phase and suggest that the Rp isomer is more rigid than the other isomers in the choline head group. In the gel phase (25 and 35 degrees C) narrower and symmetric line shapes were observed for Sp and Rp + Sp isomers, and the apparent line widths were comparable to those of DPPC. In the liquid crystalline phase there are dramatic differences between the spectra of DPPC and different isomers of DPPsC.(ABSTRACT TRUNCATED AT 250 WORDS)

Choline↗