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1.
Steady-state fluorescence polarization of the fluorescent probe 1,6-diphenyl-1,3,5-hexatriene reported temperature-dependent lipid order in l-α-dimyristoylphosphatidylcholine, egg phosphatidylcholine and synaptosomal membranes. No change in lipid order was detected after depolarization of synaptosomes by veratridine (150 μM) even in the presence of 2 mM CaCl2. However, Ca2+ reduced the mobility of a second probe, dansylated dipalmitoylphosphatidylethanolamine, in dispersions of synaptosomal lipids. This effect, which was seen at a Ca2+/total phospholipid ratio as low as 0.1, may represent an interaction between the cation and negatively-charged phospholipids. It is suggested that Ca2+ promotes a phase separation in synaptosomal lipids which may be relevant to the process of neurotransmitter release. 相似文献
2.
The influence of Ca2+ mediators (nifedipine, verapamil and prostaglandin F2α) on fluorescence polarization of l-anilino-8-napthalene-sulphonate in dipalmitoyl phosphatidylcholine and dimyristoyl phosphatidylcholine
liposomes was studied at various temperatures to understand the dynamic behaviour of membrane lipids. We also studied the
effect of change in calcium concentration on the fluorescence polarization of the dye in the liposomes. Our results show increase
in polarization (indicative of stiffening of the membrane) in the presence of Ca2+ ions. In the case of dimyristoyl phosphatidylcholine liposomes, all 3 drugs caused decrease in fluorescence polarization
(increase in fluidity of the membrane) with or without Ca2+ ions in the medium. Contrary to this, in the case of dipalmitoyl phosphatidylcholine liposomes, the fluidization effect is
observed for all the 3 drugs in the absence of Ca2+ ions; in the presence of Ca2+ ions stiffening is observed upon addition of nifedipine and verapamil which are antagonists, and fluidization is observed
upon addition of prostaglandin F2α. The role of drug-induced fluidity changes in membranes in therapy planning is discussed in the paper. 相似文献
3.
Isabel Baeza Carlos Wong Ricardo Mondragón Sirenia González Miguel Ibáñez Norberto Farfán Carlos Argüello 《Journal of molecular evolution》1994,39(6):560-568
Liposomes formed from egg-yolk phosphatidylcholine:egg-yolk phosphatidate (molar ratio 2:1) containing pBR322 DNA and DNase I were induced to form, with divalent cations, bilayer/nonbilayer phase transitions of phosphatidate which allowed cation diffusion into liposomes; then cation diffusion was measured by the activation of the hydrolysis of DNase I on DNA. The formation of phosphatidate transitions on liposomes was demonstrated by freeze-fracture and 31P NMR, and a direct correlation between the formation of phosphatidate transitions and the transbilayer diffusion of cations was found: only Ca2+ and Mn2+, which induce phase transitions, were able to penetrate liposomes and triggered the DNase I activity; in addition, Ca2+ at higher concentrations (10 mM) caused fusion of liposomes, whereas Mn2+ did not, suggesting that transitions induced by Mn2+ participated only in the diffusion of this ion; furthermore, Mg2+ neither formed phase transitions nor triggered the enzymatic activity. The liposomes studied represent more dynamic structures that can form phosphatidate structures involved in both (1) the interchange of divalent cations with the surroundings, thereby modulating encapsulated enzymes, and (2) the fusion of lipid vesicles probably implicated in the enrichment of liposomal content in the early Precambian Earth.Correspondence to: C. Argüello 相似文献
4.
Sheep red blood cells are shown to incorporate phosphatidylcholine when incubated in human plasma in the presence of EGTA. This treatment results in up to a 5-fold increase in mol ratio of phosphatidylcholine to sphingomyelin. By replacing EGTA with Ca2+ the increase of phosphatidylcholine content is completely inhibited, due to the activation of the membrane bound lecithinase which rapidly degrades the incorporated phosphatidylcholine. Analogous treatments of the isolated erythrocyte membranes resulted in similar phosphatidylcholine incorporation but in the presence of Ca2+ a residual phosphatidylcholine uptake was still observed. These results suggest that in the isolated membranes small amounts of phosphatidylcholine can be incorporated into an additional region which is unavailable for the membrane lecithinase. The increase in the phosphatidylcholine to sphingomyelin mol ratio in sheep red blood cells is concomitant with an increase in lipid fluidity, as well as increase in osmotic fragility. 相似文献
5.
B. De Kruijff A.J. Verkley C.J.A. Van Echteld W.J. Gerritsen C. Mombers P.C. Noordam J. De Gier 《生物化学与生物物理学报:生物膜》1979,555(2):200-209
A new type of lipid organization is observed in mixtures of phosphatidylcholine with cardiolipin (in the presence of Ca2+), monoglucosyldiglyceride 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. 相似文献
6.
When cat adrenocortical cells were incubated with exogenous phospholipid substrate (autoclaved ) in the presence of corticotropin, there was a Ca2+-dependent increase in phospholipid breakdown activity, suggesting that a hormone-stimulated phospholipase is localized to the plasma membrane. Phospholipase activity in a particulate fraction from lysed cells at neutral pH was a function of the Ca2+ concentration. The addition of increasing Ca2+ concentrations to a subcellular fraction of lysed cells which had been prelabelled with [14C]arachidonic acid produced graded increases in fatty acid release. A depletion of label from phosphatidylcholine was observed, as well as a marked increase in radioactivity associated with phosphatidylethanolamine. The subcellular fraction of cells prelabelled with [14C]palmitic acid failed to release fatty acid in response to Ca2+, although a loss of label from phosphatidylcholine and a modest gain in label by phosphatidylethanolamine was demonstrable. A Ca2+-activated deacylation-reacylation reaction preferentially involving phosphatidylethanolamine was evident in cortical cells prelabelled with archidonic acid; whereas, other Ca2+-stimulated lipolytic reactions also appeared to be operative in cells prelabelled with either arachidonic or palmitic acid. The Ca2+-dependent mobilization of arachidonic acid from an endogenous phospholipid pool lends additional support to the idea that Ca2+-mediated activation of phospholipase A2 participates in the control of adrenocortical activity. However, since Ca2+ also stimulated arachidonic acid liberation from cortical triglycerides, these lipid moieties may also contribute to the observed effects of Ca2+ on fatty acid release. 相似文献
7.
A.G. Lee 《生物化学与生物物理学报:生物膜》1976,448(1):34-44
The efefct of a number of amine anaesthetics related to procaine on the temperature of lipid phase transitions has been studied using chlorophyll α as a fluorescence probe. The amines cause a reduction in the temperature of the phase transition of dipalmitoyl phosphatidylcholine and dipalmitoyl phosphatidylethanol-amine and of mixtures of these lipids. The binding of charged amines causes a build up of positive charge on the membranes, limiting the binding. Incorporation of negative charge into the lipid bilayers causes a considerable increase in the binding of the charged amines, and the effect is reversed by addition of Ca2+. Anaesthesia is suggested to arise from an increase in the proportion of lipid in the liquid crystalline phase, resulting in a conformational change in the sodium channel. Effects of the tertiary amines on nerve conduction can be understood if the negatively charged lipid in the membrane is concentrated around the sodium channel: positively charged anaesthetics will have a greater effect when applied to the inside of a nerve because of the low Ca2+ concentration inside the nerve. 相似文献
8.
The effects of Ca2+ on phosphatidic acid-phosphatidylcholine membranes have been studied using phospholipid spin labels. ESR spectra of spin-labeled phosphatidic acid-phosphatidylcholine membranes and phosphatidic acid-spin-labeled phosphatidylcholine membranes are exchange-broadened immediately upon addition of CaCl2. These changes directly and conclusively indicate Ca2+-induced clustering of spin-labeled phosphatidylcholine and aggregation of spin-labeled phosphatidic acid bridged by Ca2+-chelation in the binary phopholipid membranes. In the Ca2+-chelated aggregates, the motions of the alkyl chains of phosphatidic acid are greatly reduced and the lipid molecules are more closely packed. The clusters and aggregates are formed in patches and the sizes are dependent on the fractions. Ba2+ and Sr2+ induce the lateral phase separations to the same extent as Ca2+. Mg2+ is also effective but to a lesser extent. In acid solutions (pH 5.5), the Ca2+-induced lateral phase separations are of slightly lesser extent than in alkaline solution (pH 7.9). These results are compared with those for phosphatidylserine-phosphatidylcholine membranes reported previously and necessary conditions for the lateral phase separations are discussed. 相似文献
9.
P.W.M. Van Dijck P.H.J.Th. Ververgaert A.J. Verkleij L.L.M. Van Deenen J. De Gier 《生物化学与生物物理学报:生物膜》1975,406(4):465-478
10.
1. Shifts in the 1H and 31P-nmr signals originating from the outer and inner phosphorylcholine head-groups and from the lipid acyl chains are observed when phosphatidylcholine vesicles are treated with increasing extravesicular concentrations of the lanthanides Eu3+, Pr3+, Yb3+, and Dy3+. 2. The addition of KNCS to increase the binding of the lanthanide ions to the outer head-groups is used to demonstrate that the intravesicular group shifts are not caused by bulk susceptibility effects. 3. The magnitude and direction of the observed shifts in the 1H-nmr spectrum are shown to be consistent with (a) pseudocontact interaction of the paramagnetic lanthanide ions with the outer phospholipid head-groups, (b) current views of the conformation of the phosphatidylcholine head-group in the presence of lanthanides, and (c) a conservation of magnetic field within the vesicles due to their spherical nature. 4. Variation of the shifts with temperature are compared for egg phosphatidylcholine and dipalmitoyl phosphatidylcholine. The temperature variation in shifts is also used to study phase transitions in each monolayer and phase separations in mixed lipid systems. 相似文献
11.
The fully active gastrin and CCK analogues [Nle15]-gastrin- 17 and [Nle, Thr]-CCK-9 were analysed for their Ca2+ and Tb3+ affinities in various membrane mimetic conditions. In TFE both gastrin and CCK exhibited high affinities for calcium and terbium. At saturation level identical metal ion/peptide ratios were determined with Ca2+ and Tb3+, i.e. R = 3 for gastrin and R = 1 for CCK, confirming the very similar coordination properties of the two metal ions. The conformational effects of both metal ions were found to be very similar with a disordering effect in the case of gastrin and a conformational transition to β-turn type structure in the case of CCK. In order to mimic more properly physiological conditions, similar experiments were performed in the prsence of phospholipid bilayers. No interaction of the peptides with the bilayers was observed even in the presence of phospholipid bilayers. No interaction of the peptides with the bilayers was observed even in the presence of mmolar Ca2+ concentrations. Induced lipid interaction via N-terminal lipodervatization of gastrin and CCK allowed to translocate quantitatively the two hormones into phospholipid bilayers and to examine the effect of extravesicular Ca2+ on the conformation of the peptide headgroups and on their display at the water/lipid interphase. The CCK moiety of the lipo-CCK inserted into phospholipid bilayers interacts with the lipid phase and addition of Ca2+ enhances the clustering of the peptide headgroups in a more β-sheet type conformation. Conversely, insertion of lipo-gastrin into the bilayers leads to full exposure of the gastrin headgroup to the bulk water in predominantly random coil structure. Again Ca2+ provokes aggregation. As the lipo-peptide/phospholipid system still represents only an artificial model, it remains hazardous to derive a biological relevance from these data. The significantly higher affinity of lanthanide ions than Ca2+ for the peptides could well play a role in the inhibibitory activity of lanthanum on the signal transduction of the CCK family of hormones. 相似文献
12.
Ca2+-induced phase separation in phosphatidylserine/phosphatidylethanolamine and phosphatidylserine/phosphatidylethanolamine/phosphatidylcholine model membranes was studied using spin-labeled phosphatidylethanolamine and phosphatidylcholine and compared with that in phosphatidylserine/phosphatidylcholine model membranes studied previously. The phosphatidyl-ethanolamine-containing membranes behaved in qualitatively the same way as did phosphatidylserine/phosphatidylcholine model membranes. There were some quantitative differences between them. The degree of phase separation was higher in the phosphatidylethanolamine-containing membranes. For example, the degree of phase separation in phosphatidylserine/phosphatidylethanolamine membranes containing various mole fractions of phosphatidylserine was 94–100% at 23°C and 84–88% at 40°C, while the corresponding value for phosphatidylserine/phosphatidylcholine membranes was 74–85% at 23°C and 61–79% at 40°C. Ca2+ concentration required for the phase separation was lower for phosphatidylserine/phosphatidylethanolamine than that for phosphatidylserine/phosphatidylcholine membranes; concentration to cause a half-maximal phase separation was M for phosphatidylserine-phosphatidylethanolamine and M for phosphatidylserine/phosphatidylcholine membranes. The phase diagram of phosphatidylserine/phosphatidylethanolamine membranes in the presence of Ca2+ was also qualitatively the same as that of phosphatidylserine/phosphatidylcholine except for the different phase transition temperatures of phosphatidylethanolamine (17°C) and phosphatidylcholine (?15°C). These differences were explained in terms of a greater tendency for phosphatidylethanolamine, compared to phosphatidylcholine, to form its own fluid phase separated from the Ca2+-chelated solid-phase phosphatidylserine domain. 相似文献
13.
Dynamic light scattering has been used to study the temperature dependence of Ca2+-induced fusion of phosphatidylserine vesicles and mixed vesicles containing phosphatidylserine and different phosphatidylcholines. The final vesicle size after Ca2+ and EDTA incubation serves as a measure of the extent of fusion. With phosphatidylserine vesicles, the extent of fusion shows a sharp maximum at an incubation temperature which depends on the Ca2+ concentration between 0.8 and 2 mM. The shift in the fusion peak temperature with Ca2+ concentration is similar to the typical shift in the phase transition temperature with divalent cation concentration in acidic phospholipids. The results suggest a direct correlation between the fusion peak temperature and the phase transition temperature in the presence of Ca2+ prior to fusion. With mixed vesicles containing up to 33% of a phosphatidylcholine in at least 2 mM Ca2+, the extent of fusion as a function of incubation temperature also shows a maximum. The fusion peak temperature is essentially independent of the quantity and type of phosphatidylcholine and the Ca2+ concentration, and identical to that with pure phosphatidylserine in excess Ca2+. The results imply that Ca2+-induced molecular segregation occurs first, and fusion subsequently takes place between pure phosphatidylserine domains. 相似文献
14.
Konstantin N. Belosludtsev Alexander S. Trudovishnikov Natalia V. Belosludtseva Alexey V. Agafonov Galina D. Mironova 《The Journal of membrane biology》2010,237(1):13-19
Earlier we found that in the presence of Ca2+ palmitic acid (Pal) increases the nonspecific permeability of artificial (planar and liposomal) membranes and causes permeabilization
of the inner mitochondrial membrane. An assumption was made that the mechanism of Pal/Ca2+-induced membrane permeabilization relates to the Ca2+-induced phase separation of Pal and can be considered as formation of fast-tightening lipid pores due to chemotropic phase
transition in the lipid bilayer. In this article, we continue studying this pore. We have found that Pal plus Ca2+ permeabilize the plasma membrane of red blood cells in a dose-dependent manner. The same picture has been revealed for stearic
acid (20 μM) but not for myristic and linoleic acids. The Pal-induced permeabilization of erythrocytic membranes can also
occur in the presence of Ba2+ and Mn2+ (200 μM), but other bivalent cations (200 μM Mg2+, Sr2+, Ni2+, Co2+) are relatively ineffective. The formation of Pal/Ca2+-induced pores in the erythrocytic membranes has been found to result in the destruction of cells. 相似文献
15.
D. Papahadjopoulos W.J. Vail C. Newton S. Nir K. Jacobson G. Poste R. Lazo 《生物化学与生物物理学报:生物膜》1977,465(3):579-598
The interaction of phosphatidylserine vesicles with Ca2+ and Mg2+ has been examined by several techniques to study the mechanism of membrane fusion. Data are presented on the effects of Ca2+ and Mg2+ on vesicle permeability, thermotropic phase transitions and morphology determined by differential scanning calorimetry, X-ray diffraction, and freeze-fracture electron microscopy. These data are discussed in relation to information concerning Ca2+ binding, charge neutralization, molecular packing, vesicle aggregation, phase transitions, phase separations and vesicle fusion.The results indicate that at Ca2+ concentrations of 1.0–2.0 mM, a highly cooperative phenomenon occurs which results in increased vesicle permeability, aggregation and fusion of the vesicles. Under these conditions the hydrocarbon chains of the lipid bilayers undergo a phase change from a fluid to a crystalline state. The aggregation of vesicles that is observed during fusion is not sufficient in itself to induce fusion without a concomitant phase change. Mg2+ in the range of 2.0–5.0 mM induces aggregation of phosphatidylserine vesicles but no significant fusion nor a phase change.From the effect of variations in pH, temperature, Ca2+ and Mg2+ concentration on the fusion of vesicles, it is concluded that the key event leading to vesicle membrane fusion is the isothermic phase change induced by the bivalent metals. It is proposed that this phase change induces a transient destabilization of the bilayer membranes that become susceptible to fusion at domain boundaries. 相似文献
16.
Calcium- and calmodulin-regulated breakdown of phospholipid by microsomal membranes from bean cotyledons 总被引:11,自引:8,他引:3
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Evidence for the involvement of Ca2+ and calmodulin in the regulation of phospholipid breakdown by microsomal membranes from bean cotyledons has been obtained by following the formation of radiolabeled degradation products from [U-14C]phosphatidylcholine. Three membrane-associated enzymes were found to mediate the breakdown of [U-14C] phosphatidylcholine, viz. phospholipase D (EC 3.1.4.4), phosphatidic acid phosphatase (EC 3.1.3.4), and lipolytic acyl hydrolase. Phospholipase D and phosphatidic acid phosphatase were both stimulated by physiological levels of free Ca2+, whereas lipolytic acyl hydrolase proved to be insensitive to Ca2+. Phospholipase D was unaffected by calmodulin, but the activity of phosphatidic acid phosphatase was additionally stimulated by nanomolar levels of calmodulin in the presence of 15 micromolar free Ca2+. Calmidazolium, a calmodulin antagonist, inhibited phosphatidic acid phosphatase activity at IC50 values ranging from 10 to 15 micromolar. Thus the Ca2+-induced stimulation of phosphatidic acid phosphatase appears to be mediated through calmodulin, whereas the effect of Ca2+ on phospholipase D is independent of calmodulin. The role of Ca2+ as a second messenger in the initiation of membrane lipid degradation is discussed. 相似文献
17.
Sechan Wee Janet M. Dowding Mathew J. Nadakavukaren Brian J. Wilkinson 《Antonie van Leeuwenhoek》1994,65(1):35-39
Paracoccus denitrificans grown on complex medium deficient in Mg2+ and Ca2+ are rendered lysozyme susceptible by washing with NaCl, whereas cells grown in a succinate-salts medium (Mg2+ and Ca2+ sufficient) or complex medium supplemented with Mg2++Ca2+ are not. The material released by water washing of cells grown on complex medium and complex medium supplemented with Mg2+ and Ca2+ was characterized by a high protein content. There was a high lipid: protein ratio and an appreciable amount of 3-deoxyoctulosonic acid in the material released by NaCl washing of cells grown under all conditions, indicating release of outer membrane material. The lipid ornithine: lipid phosphorous ratios of NaCl wash from cells grown on complex medium and complex medium supplemented with Mg2+ and Ca2+ were 0.54 and 0.34, respectively. Although NaCl washing removed outer membrane material from cells grown under all conditions, only divalent cation deficient cells were rendered lysozyme susceptible. This might be explained by the increased outer membrane ornithine-containing lipid to phospholipid ratio in these cells yielding a more permeable outer membrane. 相似文献
18.
Nejat Düzgünes Jan Wilschut Robert Fraley Demetrios Papahadjopoulos 《生物化学与生物物理学报:生物膜》1981,642(1):182-195
We have investigated the contribution of various phospholipids to membrane fusion induced by divalent cations. Fusion was followed by means of a new fluorescence assay monitoring the mixing of internal aqueous contents of large (0.1 μm diameter) unilamellar liposomes. The rate and extent of fusion induced by Ca2+ in mixed phosphatidylserine/phosphatidylcholine vesicles were lower compared to those in pure phosphatidylserine vesicles. The presence of 50% phosphatidylcholine completely inhibited fusion, although the vesicles aggregated upon Ca2+ addition. When phosphatidylserine was mixed with phosphatidylethanolamine, however, rapid fusion could be induced by Ca2+ even in mixtures that contained only 25% phosphatidylserine. Phosphatidylethanolamine also facilitated fusion by Mg2+ which could not fuse pure phosphatidylserine vesicles. In phosphatidylserine/phosphatidylethanolamine/phosphatidylcholine mixtures, in which the phosphatidylcholine content was kept at 25%, phosphatidylethanolamine could not substitute for phosphatidylserine, and the fusogenic capacity of Mg2+ was abolished by the presence of merely 10% phosphatidylcholine. The initial rate of release of vesicle contents was slower than the rate of fusion in all the mixtures used. The presence of phosphate effected a considerable decrease in the threshold concentration of Ca2+ and also enhanced 相似文献
19.
P.J. Konigsberg 《生物化学与生物物理学报:生物膜》1982,685(3):355-366
Ca2+-ATPase and other membrane proteins of the sarcoplasmic reticulum membrane from rabbit skeletal muscle have been reconstituted into lipid vesicles with increasing amounts of phosphatidylcholine. The protein composition and phospholipid concentration of these vesicles were analyzed by determining the density of the reconstituted membrane vesicles on linear H2O-2H2O gradients, in a constant concentration of sucrose. In all combinations of the Ca2+-ATPase with a weight excess of phosphatidylcholine, the reconstituted vesicles had a phospholipid-to-protein ratio similar to that of the native sarcoplasmic reticulum membrane, even though both solubilization and mixing had occurred. These vesicles of low phospholipid and high protein content exhibited all the original Ca2+-ATPase activity and ATP-stimulated calcium transport. The Ca2+-ATPase, and the calcium-binding proteins to a lesser extent, may order the lipid in such a manner so as to maintain the initial stoichiometry of lipid to protein observed in the native sarcoplasmic reticulum membrane. 相似文献
20.
The effect of Ca2+ and Mg2+ on relative fluidity of phosphatidylcholine liposomes was studied by measuring the degree of chlorophyll fluorescence polarization.
An increase in the degree of fluorescence polarization was observed on incubation of liposomes with different concentrations
of Ca2+ or Mg2+. The results have been interpreted on the basis of increase in the size of liposomes which could be brought about by calcium
or magnesium induced fusion of small unilamellar liposomes to form larger vesicles. Fusion of liposomes has also been confirmed
by the experiments on efficiency of energy transfer from chlorophyll b to chlorophyll a, and transmission electron microscopy
of liposomes before and after incubation with Ca2+ and Mg2+. 相似文献