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B de Kruijff

Publications and source records attributed to B de Kruijff.

At least 235 records · Page 13Linked to original sources
PubMed1980

31P-NMR studies on membrane phospholipids in microsomes, rat liver slices and intact perfused rat liver.

1. The 36.4 and 81 MHz 31P-NMR spectra of isolated rat liver microsomes, rat liver slices and perfused rat liver have been recorded in the 4-40 degree C temperature range. 2. In isolated microsomes at 37 degrees C the majority of the phospholipids undergo isotropic motion, whereas at 4 degrees C most of the phospholipids give rise to typical 'bilayer' spectra. 3. Isolated hydrated rat liver microsomal phosphatidylethanolamine is organised in the hexagonal HII phase above 7 degrees C. 4. The Mn2+ permeability of the microsomal membrane is strongly temperature dependent. At 37 degrees C Mn2+ addition eliminates the entire 31P-NMR spectrum, demonstrating that all phospholipids interact with Mn2+. At 4 degrees C a 43% reduction in signal intensity is observed, indicating that at this temperature 43% of the phospholipids are located in the outer monolayer of a lipid bilayer. 5. In liver slices incubated in oxygenated Krebs-Ringer buffer at 4 degrees C there is a rapid decrease in ATP level such that within 20 min almost all ATP is degraded. In these ATP-depleted liver slices at 4 degrees C, virtually all phospholipids in all membranes have 31P-NMR spectra indicating bilayer structure. At 37 degrees C approx. 14% of the phospholipids undergo isotropic motion. 6. Preliminary experiments on perfused rat liver show stable ATP levels for 4 h at 37 degrees C. The spectra, furthermore, suggest similar behavior for the membrane phospholipids to that observed in the liver slices. 7. The possible sources of teh observed isotropic motion of the membrane phospholipids are discussed.

Animals↗
PubMed1980

Application of 31P-NMR saturation transfer techniques to investigate phospholipid motion and organization in model and biological membranes.

The potential of 31P-NMR saturation transfer experiments for determining motional characteristics (in the millisecond to second time scale) of phospholipids in model and biological membranes is demonstrated. A technique to separate membrane phospholipid 31P-NMR signals from those of small water-soluble phosphates in intact cells in liver tissue is also illustrated.

Animals↗
PubMed1980

31P nuclear magnetic resonance and freeze-fracture electron microscopy studies on Escherichia coli. I. Cytoplasmic membrane and total phospholipids.

1. At the growth temperature the total phospholipids isolated from Escherichia coli cells give rise to 31P-NMR spectra which indicate the existence of lamellar, isotropic and hexagonal phases. These phases are also detected by freeze fracture electron microscopy. In particular, the isotropic phase may contain lipidic particles (possibly inverted micelles) associated with the lamellar phase. 2. The cytoplasmic membrane isolated from E. coli cells grown at 37 degrees C is mainly lamellar at 25 degrees C, whereas at 37 and 45 degrees C the presence of some almost isotropic phospholipid motion is indicated. The possible significance of the isotropic phase for the functioning of the cytoplasmic membrane is discussed.

Cytoplasm↗
PubMed1980

31P nuclear magnetic resonance and freeze-fracture electron microscopy studies on Escherichia coli. III. The outer membrane.

1. The outer membrane of a phospholipase A-deficient mutant of Escherichia coli K12, isolated without the use of EDTA and lysozyme, showed the same freeze-fracture morphology as that seen in cells and remained stable for hours as observed by 31P-NMR. 2. 31P-NMR spectroscopy of the isolated outer membranes revealed that the lipopolysaccharide exists in the same physical state as in phospholipid-lipopolysaccharide liposomes and is most probably arranged in a bilayer at 37 degrees C. The outer membrane contains most or all of the phospholipids at 37 degrees C, and all the phospholipids at 20 degrees C, as a bilayer. 3. The 31P-NMR spectroscopy of the outer membranes from a mutant strain lacking the major outer membrane protein b, c and d (60% of the total outer membrane protein) yields virtually the same spectrum as the wild-type outer membranes, although most of the particles and pits which were observed in wild-type outer membranes in freeze-fracture electron microscopy were absent. 4. Whereas treatment of wild-type outer membranes with calcium ions has no effect on the 31P-NMR spectrum, treatment with EDTA results in more motion of the lipopolysaccharide.

Calcium↗
PubMed1980

Preservation of bilayer structure in human erythrocytes and erythrocyte ghosts after phospholipase treatment. A 31P-NMR study.

1. Fresh human erythrocytes were treated with lytic and non-lytic combinations of phospholipases A2, C and sphingomyelinase. The 31P-NMR spectra of ghosts derived from such erythrocytes show that, in all cases, the residual phospholipids and lysophospholipids remain organized in a bilayer configuration. 2. A bilayer configuration of the (lyso)phospholipids was also observed after treatment of erythrocyte ghosts with various phospholipases even in the case that 98% of the phospholipid was converted into lysophospholipid (72%) and ceramides (26%). 3. A slightly decreased order of the phosphate group of phospholipid molecules, seen as reduced effective chemical shift anisotropy in the 31P-NMR spectra, was found following the formation of diacyglycerols and ceramides in the membrane of intact erythrocytes. Treatment of ghosts always resulted in an extensive decrease in the order of the phosphate groups. 4. The results allow the following conclusions to made: a. Hydrolysis of phospholipids in intact red cells and ghosts does not result in the formation of non-bilayer configuration of residual phospholipids and lysophospholipids. b. Haemolysis, which is obtained by subsequent treatment of intact cells with sphingomyelinase and phospholipase A2, or with phospholipase C, cannot be ascribed to the formation of non-bilayer configuration of phosphate-containing lipids. c. Preservation of bilayer structure, even after hydrolysis of all phospholipid, shows that other membrane constitutents, e.g. cholesterol and/or membrane proteins play an important role in stabilizing the structure of the erythrocyte membrane. d. A major prerequisite for the application of phospholipases in lipid localization studies, the preservation of a bilayer configuration during phospholipid hydrolysis, is met for the erythrocyte membrane.

Ceramides↗
PubMed1980

The action of pimaricin, etruscomycin and amphotericin B on liposomes with varying sterol content.

1. The effect of pimaricin, etruscomycin and amphotericin B on the K+ release from liposomes is strongly dependent on their sterol concentration. Pimaricin and etruscomycin induce K+ release from egg lecithin liposomes with cholesterol contents of more than 25 and 10 mol%, respectively, at polyene concentrations of 100 and 10 microgram/ml, respectively. Amphotericin B shows a maximal effect at a cholesterol content of 20 mol% at a concentration of 0.4 microgram/ml. 2. For liposomes containing ergosterol the sensitivity is shifted to a lower sterol content. All three polyenes show activity at 10 mol% ergosterol. The sensitivity for amphothericin B is increased approx. 15 times by the incorporation of ergosterol compared to cholesterol. The increase in sensitivity is much less for pimaricin and etruscomycin. The K+ release is maximal at an ergosterol concentration of 30 mol%. 3. Pimaricin, etruscomycin and amphotericin B can induce K+ release from erythrocytes without the release of haemoglobin at concentrations of 20, 2 and 1 microgram/ml, respectively. For these polyenes a selective permeability change is also demonstrated for liposomes since K+ is released but no [14C]dextran. Filipin shows a nonselective release of solutes from erythrocytes and liposomes. 4. At cholesterol concentrations higher than 20 mol% and ergosterol concentrations higher than 10 mol%, etruscomycin, pimaricin and amphotericin B show little dependence of the bilayer thickness and are able to release K+ from didocosenoyl phosphatidylcholine liposomes after addition of the polyene to one side of the membrane. A possible mechanism is discussed.

Amphotericin B↗
PubMed1980

Differential miscibility properties of various phosphatidylcholine/lysophosphatidylcholine mixtures.

Using enthalphy data from differential scanning calorimetry experiments and 13C-NMR linewidths of specifically (N-Me-13C)-labelled lipids, the miscibility properties of phosphatidylcholines and lysophosphatidylcholines in liposomal dispersons have been investigated. It was found that 16 : 0 lysophosphatidylcholine mixes homogeneously in 16 : 0/16 : 0 phosphatidylcholine bilayers. Mixtures of 16 : 0 lysophosphatidylcholine with 18 : 1c/18 : 1c phosphatidylcholine, of 18 : 1c lysophosphatidylcholine with 16 : 0/16 : 0 phosphatidylcholine and of 18 : 1c lysophosphatidylcholine with 18 : 1c/18 : 1c phosphatidylcholine of exhibited immiscibility in the phosphatidylcholine gel state.

Calorimetry, Differential Scanning↗
PubMed1980

Barrier characteristics of membrane model systems containing unsaturated phosphatidylethanolamines.

The barrier characteristics of membrane model systems containing unsaturated phosphatidylethanolamines have been investigated. (1) At increasing temperatures 18:1c/18:lc-phosphatidylethanolamine liposomes lose their permeability barrier for K+ as a consequence of the transition from a lamellar to a hexagonal orientation as detected by 31P-NMR and freeze-fracturing electron microscopy. (2) Introduction of 18:1c/18:1c-phosphatidylcholine in the 18:1c/18:1c-phosphatidylethanolamine lipid system stabilizes the bilayer structure and the permeability barrier for K+ and glucose while cholesterol destabilizes. (3) Upon heating of the investigated 18:1c/18:1c-phosphatidylcholine-18:1c/18:1c-phosphatidylethanolamine-(cholesterol) mixtures, structures are formed which give rise to isotropic 31P-NMR signals and which on the basis of freeze-fracture pictures are interpreted as sponge-like structures. Lowering the temperature results in restoration of the barrier function of the lipid structures.

Freeze Fracturing↗
PubMed1980

Phospholipids and membrane transport.

The ability of membrane lipids to adopt nonbilayer configurations suggests dynamic roles for lipids in many functional abilities of biological membranes. In this work evidence supporting the involvement of lipids in three types of membrane transport process is presented and discussed. These transport processes include facilitated transbilayer transport of polar molecules, transport mechanisms involving fusion events, and transport possibilities arising from alternative membrane morphology. In particular it is shown that lipids such as cardiolipin, which adopt the hexagonal HII phase in the presence of Ca2+, may be logically proposed to facilitate Ca2+ transport across membranes via an inverted micellar intermediate. Alternatively, in transport processes such as exocytosis the ability of Ca2+ to generate membrane instabilities favouring nonbilayer alternatives suggests a crucial role of phospholipid in the fusion event vital to exocytotic release. Finally, nonbilayer lipid structures may be suggested to favour formation of isolated compartments connected by a continuous membrane where lateral diffusion processes can lead to transport. These various possibilities are summarized in a "metamorphic mosaic" model of biological membranes.

Adrenal Glands↗
PubMed1979

Inside-outside distribution and diffusion of phosphatidylcholine in rat sarcoplasmic reticulum as determined by 13C NMR and phosphatidylcholine exchange protein.

1. The transverse distribution of phosphatidylcholine in rat sarcoplasmic reticulum was investigated employing 13C NMR in conjunction with the shift reagent DyCl3. 2. Sarcoplasmic reticulum phosphatidylcholine was enriched with 13C by feeding rats a diet containing [N-Me3-13C]choline. Up to 32% of the sarcoplasmic reticulum phosphatidyl-[N-Me3-12C]choline was replaced by phosphatidyl-[N-Me3-13C]choline. 3. Titration of 13C-enriched sarcoplasmic reticulum with Dy3+ indicates that 40% of the phosphatidyl-[N-Me3-13C]choline is exposed to the external medium, whereas 60% is shielded from interaction with Dy3+. 4. Incubation of 32P-labelled sarcoplasmic reticulum with excess mitochondria and phosphatidylcholine exchange protein results in a fast transport of approx. 80% of [32P]phosphatydylcholine to the mitochondria indicating that part of the phosphatidylcholine pool is involved in a rapid transbilayer movement.

Animals↗
PubMed1979

Transverse distribution and movement of lysophosphatidylcholine in sarcoplasmic reticulum membranes as determined by 13C NMR and lysophospholipase.

1. The transverse distribution of 1-palmitoyl-sn-glycero-3-phospho-N-[Me-13C]-choline in vitro incorporated in sarcoplasmic reticulum has been measured by means of 13C NMR and DyCl3 as an impermeable shift reagent. 2. Lysophosphatidylcholine added to the membranes equilibrates within 30 min at 20 degrees C between outer and inner membrane leaflet so that 42% is located in the inner leaflet. 3. Lysophosphatidylcholine diffuses back from the inner leaflet to the outer upon lysophospholipase action on the outer lysophosphatidylcholine pool.

Animals↗
PubMed1979

The occurrence of lipidic particles in lipid bilayers as seen by 31P NMR and freeze-fracture electron-microscopy.

A new type of lipid organization is observed in mixtures of phosphatidyl-choline with cardiolipin (in the presence of Ca2+), monoglycosyldiglyceride and phosphatidylethanolamine (in the presence of cholesterol). This phase is characterised by an isotropic 31P NMR signal and is visualised by freeze-fracturing as particles and pits on the fracture faces of the lipid bilayer. As the most favourable model for this phase we propose the inverted micelle sandwiched in between the two monolayers of the lipid bilayer.

Calcium↗
PubMed1979

A 13C NMR method for determination of the transbilayer distribution of phosphatidylcholine in large, unilamellar, protein-free and protein-containing vesicles.

(1) Large unilamellar vesicles have been prepared from N-[Ne3-13C]-18 : 1c/18 : 1c-phosphatidylcholine, both with and without the major intrinsic proteins from the human erythrocyte membrane incorporated in the bilayer. (2) It is shown that the inside-outside distribution of the lipid molecules in these large unilamellar structures can be determined using 13C NMR. (3) Large vesicles of 18 : 1c/18 : 1c-phosphatidylcholine containing glycophorin show an enhanced permeability to Dy3+. It is shown that the permeability barrier of these vesicles can be restored by addition of 10 mol% 18 : 1c/18 : 1c-phosphatidylethanolamine or 1-18 : 1c-lysophosphatidylcholine.

Animals↗
PubMed1978

Calcium-induced aggregation and fusion of mixed phosphatidylcholine-phosphatidic acid vesicles as studied by 31P NMR.

1. The transbilayer distribution of the phospholipids in sonicated egg phosphatidylcholine-phosphatidic acid vesicles and the interaction of Ca2+ with these vesicles was studied by 31P NMR. 2. Over a wide composition range the bilayer of these vesicles has a symmetrical phospholipid composition. 3. With ratios of Ca2+ to phosphatidic acid in the outer monolayer of the vesicles up to 0.3, Ca2+ induces vesicle aggregation. The extent of aggregation is increased by the Ca2+ concentration in the medium and the outer monolayer concentration of phosphatidic acid. The vesicle aggregation can be fully reversed by chelating Ca2+. 4. When the ratio exceeds 0.5 Ca2+ induces vesicle fusion. The fusion is maximal for vesicles containing both phosphatidylcholine and phosphatidic acid. The data suggest that Ca2+-induced lateral phase separations make the bilayer more susceptible to fusion.

Calcium↗
PubMed1978

Evidence for isotropic motion of phospholipids in liver microsomal membranes. A 31P NMR study.

1. The motional properties of phospholipids in bovine and rat liver microsomes and aqueous dispersions of the extracted lipids have been investigated employing 31 P NMR techniques. 2. The 31P NMR spectra obtained from the microsomes indicate that a considerable portion of the constituent phospholipids experience isotropic motion on the NMR timescale (10(-5) s). This is in strong contrast to the spectra obtained from aqueous dispersions of the extracted lipids, which display the characteristic lineshape associated with liquid crystalline phospholipids in (large) bilayer structures, which experience restricted anisotropic motion. 3. Evidence is presented which strongly suggests that the isotropic motion of microsomal phospholipids does not arise from tumbling of the microsomal vesicles or from lateral diffusion of phospholipids around these vesicles. 4. These results are discussed in terms of possible transitory formation of intramembrane non-bilayer lipid configurations, with which the bulk (bilayer) phospholipids are in rapid exchange.

Animals↗
PubMed1978

Effect of glycophorin incorporation on the physico-chemical properties of phospholipid bilayers.

1. The thermotropic behaviour of phospholipid molecules in reconstituted glycophorin-containing vesicles has been investigated by means of differential scanning calorimetry. Each glycophorin molecule is able to perturb the properties of 80--100 phospholipid molecules in such a way that these lipid molecules no longer participate in the cooperative gel to liquid-crystalline phase transition. This number of perturbed phospholipid molecules was discovered to be independent of the lipid charge. 2. By means of freeze-facture electron microscopy it could be demonstrated that glycophorin is not excluded from the solid lipid phase upon cooling the lipids below their gel to liquid-crystalline phase transition temperature. In mixtures of phosphatidylcholines which show solid-solid immiscibility, glycophorin is preferentially associated with the lower-melting lipid component upon phase separation, as could be demonstrated by both differential scanning calorimetry and freeze-fracture electron microscopy. 3. The effect of glycophorin on the mobility of phospholipids has been investigated by means of 31 P NMR. Glycophorin, incorporated into sonicated vesicles of dioleoylphosphatidic acid, is able to immobilize nine lipid molecules very strongly in their phosphate region. Evidence for an electrostatic inter-action between the protein and this negatively charged phospholipid has been presented. 4. The presence of glycophorin causes discontinuities in the lipid bilayer. This results in higher susceptibility of the bilayer towards attack by lipolytic enzymes and in enhanced membrane permeability.

Calorimetry, Differential Scanning↗