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Showing papers on "Membrane published in 1977"



Book ChapterDOI
TL;DR: The chapter describes hydrophobic adsorption of charged molecules to bilayer membranes, the electro static potential produced by molecular dipoles at membrane-solution interfaces, and the electrostatic boundary potentialproduced by charges located in the interior of the membrane, a few angstroms from the interface.
Abstract: Publisher Summary This chapter discusses electrostatic potentials at membrane solution interfaces. Lipids in the membranes of all cells and subcellular organelles are arranged in the form of a bilayer with the hydrocarbon tails sequestered away from the water and the polar head groups exposed to the aqueous environment. About 10%–20% of the lipids in the membranes of many cells and organelles bear a net negative charge, whereas positively charged lipids are extremely rare. The concentration of monovalent cations at the surface of the bilayer will be an order of magnitude higher than the concentration of these ions in the bulk aqueous phase. The surface potential produced by charged lipids is dependent on the salt concentration in the bulk aqueous phase and a seminal paper. The absence of proteins, polysaccharides, and other macromolecules present in biological membranes can be considered an advantage to test how well the theory of the diffuse double layer describes the electrostatic potential produced by charges on lipids. The chapter describes hydrophobic adsorption of charged molecules to bilayer membranes, the electrostatic potential produced by molecular dipoles at membrane-solution interfaces, and the electrostatic boundary potential produced by charges located in the interior of the membrane, a few angstroms from the interface. Few examples of the possible biological significance of these electrostatic surface potentials are also described.

789 citations


Journal ArticleDOI
04 Aug 1977-Nature
TL;DR: It is shown that the size of these pores can be varied in a controlled manner, and that the leaky membrane can be resealed while the haemolysis is prevented, and foreign molecules have successfully been incorporated into the resealed, but otherwise intact, erythrocytes.
Abstract: APPLICATION of an electric pulse, at field intensities of a few kV cm−1 and of duration in the µs range, to an isotonic suspension of erythrocytes is known to cause haemolysis of the red cells1–4. Studies from different laboratories suggest that the haemolysis is due to the field-induced transmembrane potential1,3,4. Our recent experiments5 indicate that once the transmembrane potential reaches a threshold of approximately 1 V, which corresponds to an applied field of 2.2 kV cm−1, the erythrocyte membrane becomes leaky to normally impermeant ions or molecules. The permeation of solutes leads to the swelling and eventual lysis of the red cells. This type of haemolysis is known as colloid osmotic haemolysis6,7. The voltage-induced permeability change is consistent with the formation of pores in the membrane. We show here that the size of these pores can be varied in a controlled manner, and that the leaky membrane can be resealed while the haemolysis is prevented. Foreign molecules have successfully been incorporated into the resealed, but otherwise intact, erythrocytes.

526 citations


Journal ArticleDOI
TL;DR: In this paper, the formation of asymmetric and symmetric membranes obtained by precipitation of a polymer solution is discussed, and the different membrane structures and especially formation of the "skin" are rationalized on the basis of thermodynamic and kinetic aspects of phase separation processes.

524 citations



Journal ArticleDOI
27 Oct 1977-Nature
TL;DR: A surprisingly precise sequence by which the nascent chain of this membrane glycoprotein is glycosylated in two steps is revealed, which has important implications for the mechanisms of membrane assembly.
Abstract: Studies of the synthesis and incorporation of the vesicular stomatitis virus glycoprotein into membranes in a synchronised cell-free system demonstrate a tight coupling between polypeptide synthesis and membrane insertion, as a result of which the nascent chain crosses the membrane. The studies reveal a surprisingly precise sequence by which the nascent chain of this membrane glycoprotein is glycosylated in two steps. These findings have important implications for the mechanisms of membrane assembly.

506 citations


Journal ArticleDOI
06 May 1977-Science
TL;DR: Ethanol in vitro increased the fluidity of spin-labeled membranes from normal mice, suggesting that the membranes themselves had adapted to the drug, a novel form of drug tolerance.
Abstract: Ethanol in vitro increased the fluidity of spin-labeled membranes from normal mice. Membranes from mice that had been subjected to long-term ethanol treatment were relatively resistant to this fluidizing effect. The data suggest that the membranes themselves had adapted to the drug, a novel form of drug tolerance.

503 citations


Journal Article
TL;DR: The data suggest that nonlethal concentrations of ethanol may increase membrane fluidity in vivo, and this effect was dose-related up to 0.35 M in all the membranes except myelin.
Abstract: The effects of ethanol on membrane fluidity at 37° have been assessed by a sensitive electron paramagnetic resonance technique. Erythrocyte and brain membranes from DBA/2J mice were spin-labeled with 5-doxylstearic acid ( N -oxyl-49,49-dimethyloxazolidine derivative of 5-ketostearic acid). The molecular motion of the spin label was measured from the EPR spectrum by determining the order parameter S , an index of membrane fluidity. The fluidity of both erythrocyte and synaptosomal membranes was greater than that of myelin but less than that of mitochondrial membranes. The addition of low concentrations (0.02 or 0.04 M) of ethanol in vitro increased fluidity in erythrocyte, mitochondrial, and synaptosomal membranes. This fluidizing effect of ethanol was dose-related up to 0.35 M in all the membranes except myelin. These data suggest that nonlethal concentrations of ethanol may increase membrane fluidity in vivo .

457 citations


Journal ArticleDOI
TL;DR: Reconstitution experiments with GTP-binding fractions obtained from isoproterenol-treated membranes suggested that the characteristic synergistic amplification of hormone action by guanylnucleotides is mediated via the guanyl nucleotide binding protein.

412 citations


Patent
13 Sep 1977
TL;DR: In this article, the multicomponent membranes for gas separation are disclosed which are effective for separating at least one gas from gaseous mixtures by permeation wherein the multic-component membranes are comprised of a coating in occluding contact with a porous separation membrane.
Abstract: Multicomponent membranes for gas separation are disclosed which are effective for separating at least one gas from gaseous mixtures by permeation wherein the multicomponent membranes are comprised of a coating in occluding contact with a porous separation membrane. The multicomponent membranes advantageously exhibit less resistance to permeate gas flow for the at least one gas than for at least one remaining gas in the gaseous mixture. For at least one pair of gases the separation factor of the multicomponent membrane is significantly greater than the determined intrinsic separation factor of the material of the coating. Processes and apparatus for gas separation utilizing the multicomponent membranes are also disclosed.

399 citations



Journal ArticleDOI
TL;DR: Isotonic suspensions of human erythrocytes were exposed to single electric pulses of intensity at a few kV/cm and duration in microseconds, and the cell membranes became permeable to Na+ and K+ and hemolysed through the colloid osmotic effect of hemoglobin.

Journal ArticleDOI
TL;DR: A method is described for the large-scale purification of membrane fragments very rich in acetylcholine (nicotinic) receptor from the electric organ of Torpedo marmorata and a striking variability of the ratios of the 40000-Mr band to the 50000 and 66000-Mr ones is revealed.
Abstract: A method is described for the large-scale purification of membrane fragments very rich in acetylcholine (nicotinic) receptor from the electric organ of Torpedo marmorata. The preparations of purified membrane fragments have a specific activity of more than 4000 nmol α-toxin binding sites/g protein and give only four main polypeptide bands by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. Observations by electron microscopy show that the purified preparation of receptor-rich membrane fragments is composed of only one class of membrane fragments covered with 8-nm rosettes identified as acetylcholine receptor molecules. This preparation is used as a starting material for the detergent solubilization and the large-scale purification of the acetylcholine receptor protein, without using affinity chromatography. A sucrose gradient centrifugation of a Triton X-100 extract of receptor-rich membranes done in the presence of 2-mercaptoethanol yields large quantities of receptor protein in a homogeneous form as indicated by polyacrylamide gel electrophoresis, isoelectric focussing and electron microscopy. Polyacrylamide gel electrophoresis of the purified protein in the presence of sodium dodecylsulfate reveals three bands of apparent molecular weights 40000 ± 1000, 50000 ± 2000 and 66000 ± 2000, the two heaviest ones being present in significantly lower amounts than the 40000-Mr one. The comparison of several samples of purified protein with different specific activities reveals a striking variability of the ratios of the 40000-Mr band to the 50000 and 66000-Mr ones.

Journal ArticleDOI
17 Feb 1977-Nature
TL;DR: A theory to support the hypothesis that bioelectric fields may segregate charged components floating in the plasma membranes of cells by a process of electrophoresis along the membrane is presented.
Abstract: Bioelectric fields may segregate charged components floating in the plasma membranes of cells by a process of electrophoresis along the membrane. Molecules in cell membranes may be sorted to different portions of the cell surface by such electrical gradients. We present here a theory to support this hypothesis.

Journal ArticleDOI
TL;DR: This study confirms the usefulness of applied isotopic markers for isolating plasma membranes in high yield from cultured fibroblasts and shows large membrane vesicles essentially free from contaminating organelles.
Abstract: 1. A method was developed which allows the rapid preparation of pure plasma membranes in high yield from cultured fibroblasts. 2. Cells are lysed in hypo-osmotic borate/EDTA and, after differential centrifugation, the membranes collected by centrifugation on a sucrose barrier. 3. Electron microscopy of the isolated material shows large membrane vesicles essentially free from contaminating organelles. 4. There is no detectable activity of the endoplasmic-reticulum enzyme marker, NADH2--lipoamide oxidoreductase (EC 1.6.4.3), and that of succinate dehydrogenase (EC 1.3.99.1), a marker for mitochondria, is substantially decreased. Chemical compositions are in good agreement with previous observations. 5. This study confirms the usefulness of applied isotopic markers for isolating plasma membranes.

Journal ArticleDOI
TL;DR: The finding of protein- depleted blebs in regions of plasma and granule membrane interaction raises the interesting possibility that blebbing may be a process for exposing the granule contents to the extracellular space and for the elimination of excess lipid while conserving membrane proteins.
Abstract: We have used thin section and freeze-fracture electron microscopy to study membrane changes occurring during exocytosis in rat peritoneal mast cells. By labeling degranulating mast cells with ferritin-conjugated lectins and anti-immunoglobulin antibodies, we demonstrate that these ligands do not bind to areas of plasma membrane or granule membrane which have fused with, or are interacting with, granule membrane. Moreover, intramembrane particles are also largely absent from both protoplasmic and external fracture faces of plasma and granule membranes in regions where these membranes appear to be interacting. Both the externally applied ligands and intramembrane particles are sometimes concentrated at the edges of fusion sites. The results indicate that membrane proteins are displaced laterally into adjacent membrane regions before the fusion process and that fusion occurs between protein-depleted lipid bilayers. The finding of protein-depleted blebs in regions of plasma and granule membrane interaction raises the interesting possibility that blebbing may be a process for exposing the granule contents to the extracellular space and for the elimination of excess lipid while conserving membrane proteins.

Journal ArticleDOI
TL;DR: The ability of the oxidized and singly reduced species of several bipyridylium cations to cross the cytoplasmic membrane of Escherichia coli was studied to locate the sites of reaction of the dyes with anaerobic respiratory enzymes.
Abstract: The ability of the oxidized and singly reduced species of several bipyridylium cations to cross the cytoplasmic membrane of Escherichia coli was studied to locate the sites of reaction of the dyes with anaerobic respiratory enzymes Benzyl Viologen radical crossed the membrane rapidly, whereas the oxidized species did not The oxidized or radical species of Methyl Viologen, Morfamquat or Diquat did not rapidly cross the membrane It was also shown that the dithionite anion does not cross the cytoplasmic membrane of E coli Diquat radical donates electrons to the nitrate reductase pathway at the periplasmic aspect of the membrane, whereas Benzyl Viologen radical reacted directly with nitrate reductase itself (EC 17994) at the cytoplasmic aspect of the membrane Thus the pathway of electron transfer in the nitrate reductase pathway is transmembranous Formate hydrogenlyase (EC 1212) and an uncharacterized nitrite reductase activity react with bipyridylium dyes at the periplasmic aspect of the membrane Fumarate reductase (succinate dehydrogenase; EC 13991) reacts with bipyridylium radicals, and formate dehydrogenase (cytochrome) (EC 1221) with ferricyanide, at the cytoplasmic aspect of the membrane The differing charge and membrane permeation of oxidized and radical species of bipyridylium dyes greatly complicate their use as potentiometric mediators in suspensions of cells or membrane vesicles

Journal ArticleDOI
TL;DR: A selective release of membrane domains that lack peripheral membrane proteins and are enriched in acetylcholinesterase is suggested, which could represent an acceleration of the physiological aging process.
Abstract: Human erythrocytes incubated without glucose at 37 degrees C (in vitro aging) release spectrin-free vesicles after 12 or more hours. The release of vesicles is dependent upon ATP depletion. If the endogenous level of ATP is maintained, vesicle release is completely inhibited up to 54 h. Vesicle release is independent of hemolysis because in vitro aged cells and cells that maintain their ATP levels lose identical amounts of hemoglobin up to 45 h. 93 percent of all membrane particles released constitute a uniform population of spheres with a diameter of 185 +/- 23nm. These vesicles are of slightly varying densities due to varying contents of hemoglobin. Vesicles contain half the amount of membrane protein that is found in intact membranes when referred to the content of phospholipids phosphorus. This is primarily due to the absence of spectrin. However, their content of protein component III, glycophorin, and cholesterol remains the same as in intact membranes. Thus, the major integral membrane proteins are present in vesicles in similar quantities were surface area as in cells except for the enzyme acetylcholinesterase that is enriched up to twofold. The phospholipids composition of these vesicles is representative of the intact membrane except that the amount of phosphatidic acid is 10-fold higher and the amount of phosphatidylethanolamine is slightly lower than in erythrocytes. These results suggest a selective release of membrane domains that lack peripheral membrane proteins and are enriched in acetylcholinesterase. This release of spectrin-free vesicles from cells aged in vitro could represent an acceleration of the physiological aging process.

Journal ArticleDOI
TL;DR: It is shown that the use of low cation media enhances the separation of intact and broken chloroplasts in a new method of obtaining chloroplast retaining their outer membranes.

Journal ArticleDOI
TL;DR: It is proposed that the anesthetic-modified phase separation behavior of the membrane may alter neural function by a combination of the following effects: inhibition of conformational changes of intrinsic membrane proteins; prevention of the association of protein subunits to form polymeric ion channels; depression of transmitter release by preventing fusion of vesicles containing synaptic transmitter with the membrane of the presynaptic terminal.
Abstract: This paper relates research on anesthetic effects on lipid membrane systems to mechanisms of neural function. A unitary theory of anesthesia based on anesthetic-induced changes in fluid-solid-phase separations in the lipid region of nerve membranes is presented. It is suggested that anesthetics act

Journal ArticleDOI
03 Mar 1977-Nature
TL;DR: The abiotic synthesis of various lipids, including membranogenic phospholipids, are reported here, which are obvious candidates for prebiotic membrane components.
Abstract: IT is generally agreed that stable membranes were prerequisite to the assembly of the earliest self-replicating systems1–4. Phospholipids, which are ubiquitous in biological membranes and which self-assemble in aqueous environments into stable lipid bilayers and vesicles4, are obvious candidates for prebiotic membrane components. We report here the abiotic synthesis of various lipids, including membranogenic phospholipids.

Journal ArticleDOI
TL;DR: The binding of hemoglobin to red cell membranes was found to be reversible and electrostatic in nature.
Abstract: Hemoglobin quenching of the fluorescence intensity of 12-(9-anthroyl)stearic acid (AS) embedded in the red blood cell membrane occurs through an energy transfer mechanism and can be used to measure the binding of hemoglobin to the membrane. The binding of hemoglobin to red cell membranes was found to be reversible and electrostatic in nature. Using a theory of energy transfer based on Forster formulation, the quantitative data for the binding were derived. The number of binding sites was found to be 1.4 +/- 0.2 X 10(6) molecules per cell and the binding constant was 0.85 X 10(8) M-1.

Journal ArticleDOI
Peter M. Ray1
TL;DR: The results raise the possibility that primary auxin action occurs at ER membranes and could represent facilitation of the transfer of hydrogen ions and nascent secretory protein into the ER lumen followed by secretory transport of these products to the cell exterior via the Golgi system.
Abstract: Sites in maize (Zea mays L.) coleoptile homogenates that reversibly bind naphthalene-1-acetic acid with high affinity and may represent receptor sites for auxins are located primarily on cellular membranes that show the enzymic and buoyant density characteristics of membranes of the rough endoplasmic reticulum. The sites remain attached to the endoplasmic reticulum (ER) membranes after the ribosomes have been stripped off them. Binding sites for naphthylphthalamic acid, an inhibitor of auxin transport, are located on membranes different from those that carry the naphthalene-1-acetic-acid (NAA)-binding sites, and which are probably plasma membrane. The two kinds of binding sites can be largely separated by appropriate density gradient centrifugation. The results raise the possibility that primary auxin action occurs at ER membranes and could represent facilitation of the transfer of hydrogen ions and nascent secretory protein into the ER lumen followed by secretory transport of these products to the cell exterior via the Golgi system.

Journal ArticleDOI
TL;DR: Experiments are presented which suggest that a single positive charge crosses the vesicle membrane with each molecule of 5-hydroxytryptamine, providing direct evidence for Na+-coupled active 5-HydroxyTryptamine transport by the platelet plasma membrane.

Journal ArticleDOI
TL;DR: The fluidity of synaptosomal membrane preparations isolated from goldfish acclimated to 5, 15 and 25 degrees C and from rat has been estimated using the fluorescence polarisation technique with 1,6-diphenyl-1,3,5-hexatriene as probe, indicating a temperature-dependent regulation of this parameter.

Journal ArticleDOI
TL;DR: The structure of two-dimensional crystals of cytochrome oxidase (Vanderkooi et al. , 1972) has been investigated and pairs of molecules are related by a crystallographic 2-fold axis perpendicular to the plane of the membrane, suggesting the possible occurrence of dimers in the natural state.

Journal ArticleDOI
TL;DR: Cell-survival curves during hyperthermic exposure can be used to elucidate the effects of membrane modifying procedures on cell death and support the hypothesis that membrane disorganization occurs as a result of temperature increasing to a point where a lipid transition causes a membrane structural change, which results in cell-death.
Abstract: SummaryThe mechanism of hyperthermic killing, a component of some cancer therapy, is not known. Cell-survival curves during hyperthermic exposure can be used to elucidate the effects of membrane modifying procedures on cell death. Experiments were designed to test whether procedures that were reported to increase membrane fluidity also resulted in increased killing on hyperthermic exposure. An E. coli K12 mutant, K1060, is used to predictably alter the degree and amount of unsaturated fatty acids incorporated into membranes. Changing from an 18 : 1 to an 18 : 3 unsaturated fatty acid increases killing. Decreasing the amount of unsaturated fatty acid cells incorporated by increasing growth temperature decreases killing. Procaine, a drug known to decrease membrane viscosity, increases heat killing. These data are most simply explained by the hypothesis that membrane disorganization occurs as a result of temperature increasing to a point where a lipid transition causes a membrane structural change, which res...

Journal ArticleDOI
15 Jul 1977-Science
TL;DR: NSF Science Education: Basic Issues Still Unresolved.... as discussed by the authors, GAO Decision on NSF Claim Favors Curriculum Study Group, and NAS and Justice Panels Pan Federal Crime Research Effort.
Abstract: NSF Science Education: Basic Issues Still Unresolved. . . . . . . . . . . . . . . . 233 GAO Decision on NSF Claim Favors Curriculum Study Group . . . . . . . . . . . 234 NAS and Justice Panels Pan Federal Crime Research Effort .... . . . . . . . . 236 Asbestos: Trouble in the Air from Maryland Rock Quarry . . . . . . . . . . . . . . 237 Speaking Up for an Imperiled CEQ. ........................ 240

Journal ArticleDOI
TL;DR: During outward current pulses, the membrane shows marked rectification and action potentials can never be generated, so this smooth muscle tissue is classified as a single‐unit type.
Abstract: 1 The membrane potential of the smooth muscle cells of the rabbit main pulmonary artery amounts to -57 mV, the length constant of the tissue is 148 mm and the time constant of the membrane 182 msec On the basis of the electrical properties of its membrane, this smooth muscle tissue is classified as a single-unit type During outward current pulses, the membrane shows marked rectification and action potentials can never be generated2 Tetraethylammonium (10 mM) and procaine (5 mM) depolarize the membrane and increase the membrane resistance By studying the effect of both substances on the (42)K efflux, it could be concluded that they reduce the K-permeability of the membrane They also suppress the rectification of the membrane and increase the length constant of the membrane In the presence of TEA and procaine, a graded response of the membrane can be induced by outward current pulses, but overshoot potentials never occur3 Noradrenaline, in concentrations between 2 x 10(-8) and 10(-7)M, evokes contraction without depolarizing the membrane When the concentration is increased above 2 x 10(-7)M, noradrenaline depolarizes the membrane and reduces the membrane resistance A study of the effect of noradrenaline on the K, Cl and Na fluxes has revealed that it increases the permeability of the membrane for these three ions4 The tissue concentrations of Na and K are 80 and 38 m-mole/kg wet wt, respectively The amount of Cl in the cellular compartment was measured by an extrapolation procedure and found to be 13 m-mole/kg wet wt The extracellular space measured with [(14)C]sorbitol is 550 ml/kg wet wt and the dry wt/wet wt ratio 19% The calculated equilibrium potentials for K, Na and Cl (E(K), E(Na) and E(Cl)) are -83, +59 and -26 mV, respectively In efflux experiments under steady-state conditions, the following rate constants have been calculated: 0092 min(-1) for Na, 0029 min(-1) for Cl and 00054 min(-1) for K The calculated value for the ratio P(Na)/P(K) was 022 and for P(Cl)/P(K) 0635 K-free solution and 2 x 10(-6)M ouabain depolarize the cells by about 8 mV After exposure of the cells to K-free solution, they hyperpolarize on readmission of K, suggesting that part of the membrane potential could be due to electrogenic transport of ions6 A decrease of external Ca depolarizes the cells and increases the membrane resistance Na-deficiency hyperpolarizes these smooth muscle cells but this procedure does not prevent the depolarization induced by Ca deficiency

Journal ArticleDOI
TL;DR: It is demonstrated that the incompletely developed plastids have a smaller photosynthetic unit size; this is primarily due to the absence of a major light-harvesting pigment-protein complex which is present in the mature membranes.
Abstract: We have previously demonstrated (Armond, P A, C J Arntzen, J-M Briantais, and C Vernotte 1976 Arch Biochem Biophys 175:54-63; and Davis, D J, P A Armond, E L Gross, and C J Arntzen 1976 Arch Biochem Biophys 175:64-70) that pea seedlings which were exposed to intermittent illumination contained incompletely developed chloroplasts These plastids were photosynthetically competent, but did not contain grana We now demonstrate that the incompletely developed plastids have a smaller photosynthetic unit size; this is primarily due to the absence of a major light-harvesting pigment-protein complex which is present in the mature membranes Upon exposure of intermittent-light seedlings to continuous white light for periods up to 48 h, a ligh-harvesting chlorophyll-protein complex was inserted into the chloroplast membrane with a concomitant appearance of grana stacks and an increase in photosynthetic unit size Plastid membranes from plants grown under intermediate light were examined by freeze-fracture electron microscopy The membrane particles on both the outer (PF) and inner (EF) leaflets of the thylakoid membrane were found to be randomly distributed The particle density of the PF fracture face was approx four times that of the EF fracture face While only small changes in particle density were observed during the greening process under continuous light, major changes in particle size were noted, particularly in the EF particles of stacked regions (EFs) of the chloroplast membrane Both the changes in particle size and an observed aggregation of the EF particles into the newly stacked regions of the membrane were correlated with the insertion of light-harvesting pigment-protein into the membrane Evidence is presented for identification of the EF particles as the morphological equivalent of a "complete" photosystem II complex, consisting of a phosochemically active "core" complex surrounded by discrete aggregates of the light-harvesting pigment protein A model demonstrating the spatial relationships of photosystem I, photosystem II, and the light-harvesting complex in the chloroplast membrane is presented