dipalmitoylphosphatidylserine and 1-2-dipalmitoylphosphatidylglycerol

The interaction between dimethylsulfoxide (DMSO) and phospholipid monolayers with different polar headgroups was studied using "in situ" Brewster angle microscopy (BAM) coupled to a Langmuir trough. For a 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) monolayer, DMSO was shown to significantly impact the structure of the liquid expanded (LE) and gaseous phases. The domains reorganized to much larger domain structures. Domains in the liquid condensed (LC) phase were formed on the DMSO-containing subphase at the mean molecular area where only gaseous and LE phases were previously observed on the pure water subphase. These results clearly demonstrate the condensing and caging effect of DMSO molecules on the DPPC monolayer. Similar effects were found on dipalmitoyl phosphatidyl ethanolamine, glycerol, and serine phospholipids, indicating that the condensing and caging effect is not dependent upon the phospholipid headgroup structure. The DMSO-induced condensing and caging effect is the molecular mechanism that may account for the enhanced permeability of membranes upon exposure to DMSO.

Topics: 1,2-Dipalmitoylphosphatidylcholine; Cell Membrane; Dimethyl Sulfoxide; Glycerophospholipids; Microscopy; Phosphatidylethanolamines; Phosphatidylglycerols; Phosphatidylserines

The folding of amyloid beta (1-40) peptide into beta-sheet-containing fibrils is thought to play a causative role in Alzheimer's disease. Because of its amphiphilic character, the peptide can interact with phospholipid membranes. Langmuir monolayers of negatively charged DPPS, DPPG, and DMPG, and also of zwitterionic DPPC and DMPC, have been used to study the influence of the peptide on the lipid packing and, vice versa, the influence of phospholipid monolayers on the peptide secondary structure by infrared reflection absorption spectroscopy and grazing incidence X-ray diffraction. The peptide adsorbs at the air/water (buffer) interface, and also inserts into uncompressed phospholipid monolayers. When adsorbed at the interface, the peptide adopts a beta-sheet conformation, with the long axis of these beta-sheets oriented almost parallel to the surface. If the lipid exhibits a condensed monolayer phase, then compression of the complex monolayer with the inserted peptide leads to the squeezing out of the peptide at higher surface pressures (above 30 mN m(-1)). The peptide desorbs completely from zwitterionic monolayers and negatively charged DPPG and DPPS monolayers on buffer, but remains adsorbed in the beta-sheet conformation at negatively charged monolayers on water. This can be explained in terms of electrostatic interactions with the lipid head groups. It also remains adsorbed at, or penetrating into, disordered anionic monolayers on buffer. Additionally, the peptide does not influence the condensed monolayer structure at physiological pH and modest ionic strength.

Topics: 1,2-Dipalmitoylphosphatidylcholine; Adsorption; Amyloid beta-Peptides; Dimyristoylphosphatidylcholine; Peptide Fragments; Phosphatidylglycerols; Phosphatidylserines; Phospholipids; Protein Structure, Secondary; X-Ray Diffraction

The interaction of the natural mucopolysaccharide hyaluronic acid with different lipids, present in the natural membranes, was studied at the lipid/water interface using thermodynamic methods and X-ray diffraction. The results show that this biopolymer modifies the properties and the structure of the lipid monolayer. The two-dimensional crystalline lattice and domain structure of the charged octadecylamine monolayer are strongly disturbed by the hyaluronic acid, the monolayer compressibility increases and the monolayer collapse pressure drops down. In addition, the presence of charged lipid interfaces influences the structural organisation of the hyaluronic acid at the membrane/water interfaces. The impacts of these results on the structural organisation at the membrane interface are discussed.

Topics: 1,2-Dipalmitoylphosphatidylcholine; Amines; Animals; Biopolymers; Buffers; Cattle; Hyaluronic Acid; Hydrogen-Ion Concentration; Kinetics; Lipids; Molecular Structure; Phosphatidylethanolamines; Phosphatidylglycerols; Phosphatidylserines; Protein Structure, Tertiary; Solvents; Surface Properties; Temperature; Thermodynamics; Water; X-Ray Diffraction

Cell membranes and their lipids play critical roles in calcification. Specific membrane phospholipids promote the formation of calcium phosphate and become a part of the organic matrix of growing calcification. We propose that membrane lipids also promote the formation of calcium oxalate (CaOx) and calcium phosphate (CaP) containing kidney stones, and become a part of their stone matrix.. Human urine, crystals of CaOx and CaP produced in the urine of healthy individuals, and urinary stones containing struvite, uric acid, CaOx and CaP crystals for the presence of membrane lipids were analyzed. Crystallization of CaOx monohydrate at Langmuir monolayers of dipalmitoylphosphatidylglycerol (DPPG), dipalmitoylphosphatidylcholine (DPPC), dipalmitoylphosphatidylserine (DPPS), dioleoylphosphatidylglycerol (DOPG), palmitoyloleoylphosphatidylglycerol (POPG) and dimyristoylphosphatidylglycerol (DMPG) was investigated to directly demonstrate that phospholipid assemblies can catalyze CaOx nucleation.. Urine as well as CaOx and CaP crystals made in the urine and various types of urinary stones investigated contained some lipids. Urine of both CaOx and uric acid stone formers contained significantly more cholesterol, cholesterol ester and triglycerides than urine of healthy subjects. However, urine of CaOx stone formers contained more acidic phospholipids. The organic matrix of calcific stones contained significantly more acidic and complexed phospholipids than uric acid and struvite stones. For each Langmuir monolayer precipitation was heterogeneous and selective with respect to the orientation and morphology of the CaOx crystals. Crystals were predominantly monohydrate, and most often grew singly with the calcium rich (10-1) face toward the monolayer. The number of crystals/mm2 decreased in the order DPPG> DPPC and was inversely proportional to surface pressure and mean molecular area/molecule.. Stone forming conditions in the kidneys greatly impact their epithelial cells producing significant differences in the urinary lipids between healthy and stone forming individuals. Altered membrane lipids promote face selective nucleation and retention of calcium oxalate crystals, and in the process become a part of the growing crystals and stones.

Topics: 1,2-Dipalmitoylphosphatidylcholine; Adult; Aged; Aged, 80 and over; Calcium Oxalate; Crystallization; Female; Humans; Kidney Calculi; Lipids; Male; Membrane Fluidity; Middle Aged; Phosphatidylglycerols; Phosphatidylserines

The relationship between the antioxidant effect of acidic phospholipids, phosphatidic acid (PA), phosphatidylglycerol (PG) and phosphatidylserine (PS), on iron-induced lipid peroxidation of phospholipid bilayers and their abilities to bind iron ion was examined in egg yolk phosphatidylcholine large unilamellar vesicles (EYPC LUV). The effect of each acidic phospholipid added to the vesicles at 10 mol% was assessed by measuring phosphatidylcholine hydroperoxides (PC-OOH) and thiobarbituric acid-reactive substances. The addition of dipalmitoyl PS (DPPS) showed a significant inhibitory effect, although the other two acidic phospholipids, dipalmitoyl PA (DPPA) and dipalmitoyl PG (DPPG), did not exert the inhibition. Neither dipalmitoyl PC (DPPC) nor dipalmitoyl phophatidylethanolamine (DPPE) showed any remarkable inhibition on this system. None of the tested phospholipids affected the lipid peroxidation rate remarkably when the vesicles were exposed to a water-soluble radical generator. The iron-binding ability of each phospholipid was estimated on the basis of the amounts of iron recovered in the chloroform/methanol phase after separation of the vesicle solution to water/methanol and chloroform/methanol phases. EYPC LUV containing DPPS, DPPA, and DPPG had higher amounts of bound iron than those containing DPPC and DPPE, indicating that these three acidic phospholipids possess an iron-binding ability at a similar level. Nevertheless, only DPPS suppressed iron-dependent decomposition of PC-OOH significantly. Therefore, it is likely that these three acidic phospholipids possess a significant iron-binding ability, although this ability per se does not warrant them antioxidative activities. The ability to suppress the iron-dependent decomposition of PC-OOH may explain the unique antioxidant activity of PS.

Topics: Amidines; Antioxidants; Ascorbic Acid; Iron; Lipid Bilayers; Lipid Peroxidation; Liposomes; Phosphatidic Acids; Phosphatidylcholines; Phosphatidylglycerols; Phosphatidylserines; Thiobarbituric Acid Reactive Substances

In the present study we examined the short term stability of liposomes in the freeze-dried state for different lipid compositions containing trehalose as a lyoprotectant. The retention of carboxyfluorescein and average vesicle size after rehydration were monitored as a function of the temperature to which the dry cakes were exposed for 0.5 h. The thermal behaviour of the cakes was analysed by modulated temperature differential scanning calorimetry, and acyl chain order and interaction between trehalose molecules and the phospholipid headgroups was studied by Fourier transform infrared spectroscopy. Induction of leakage, suppression of the (onset) bilayer transition temperature (Tm) and enhancement of the interaction between sugar and phospholipid molecules were observed below the glass transition temperature (Tg) for all lipid compositions studied. The above changes concurred with the melting transition of the bilayer. Two out of five lipid compositions showed no significant change in average vesicle size, indicating that leakage was not necessarily caused by vesicle fusion. In addition, leakage could not be explained in terms of a phase transition during rehydration of the liposomes. We conclude that for liposomes freeze-dried in trehalose the temperature range of the bilayer melting process is a better indicator than Tg for the maximal temperature to which liposomes may be exposed for a short period of time (0.5 h) without loss of stability.

Topics: 1,2-Dipalmitoylphosphatidylcholine; Cholesterol; Drug Stability; Freeze Drying; Lipids; Liposomes; Microscopy, Electron, Scanning; Particle Size; Phosphatidylglycerols; Phosphatidylserines; Spectroscopy, Fourier Transform Infrared; Water