Showing papers on "Membrane published in 1971"
1,498 citations
890 citations
TL;DR: This chapter discusses techniques used in the laboratory for both small- and large-scale preparation of bacterial membranes from various gram-positive and gram-negative organisms, which have been extensively characterized with regard to purity, homogeneity, and pertinent physical properties.
Abstract: Publisher Summary This chapter discusses techniques used in the laboratory for both small- and large-scale preparation of bacterial membranes from various gram-positive and gram-negative organisms. The membranes prepared by these methods have been extensively characterized with regard to purity, homogeneity, and pertinent physical properties. In addition, they have been shown to be physiologically active with regard to certain integrated membrane functions, such as amino acid and sugar transport, phospholipid biosynthesis, and electron transport. A procedure employed for the preparation of bacterial membranes consists of two steps—(1) the conversion of the organism into an osmotically sensitive form and (2) the controlled osmotic lysis of the form in the presence of nucleases and a chelating agent. The structures formed as a result of this procedure consist of intact, “unit-membrane”-bound sacs which are essentially devoid of cytoplasmic constituents.
672 citations
TL;DR: The fatty acid pattern is more characteristic of the phospholipid species than of the membrane, and Inner mitochondrial membrane and plasma membrane are the two which differ most among the cytomembranes analyzed.
625 citations
TL;DR: A fraction enriched in synaptic plasma membranes (SPM fraction) can be prepared on a simple discontinuous gradient in relatively good yield and contains β-N- acetylglucosaminidase, which is not completely washed out of the SPM fraction by salt treatment but is released by low concentrations of Triton X-100.
615 citations
TL;DR: It is suggested that the ability of the alkaline earth cations to shift the conductance-voltage curves of a nerve along the voltage axis by 20–26 mv for a 10-fold increase in concentration may be due to essentially a screening rather than a binding phenomenon.
Abstract: Phospholipid bilayer membranes were bathed in a decimolar solution of monovalent ions, and the conductance produced by neutral carriers of these monovalent cations and anions was used to assess the electric potential at the surface of the membrane. When the bilayers were formed from a neutral lipid, phosphatidylethanolamine, the addition of alkaline earth cations produced no detectable surface potential, indicating that little or no binding occurs to the polar head group with these ions. When the bilayers were formed from a negatively charged lipid, phosphatidylserine, the addition of Sr and Ba decreased the magnitude of the surface potential as predicted by the theory of the diffuse double layer. In particular, the potential decreased 27 mv for a 10-fold increase in concentration in the millimolar-decimolar range. A 10-fold increase in the Ca or Mg concentration also produced a 27 mv decrease in potential in this region, which was again due to screening, but it was necessary to invoke some specific binding to account for the observation that these cations were effective at a lower concentration than Ba or Sr. It is suggested that the ability of the alkaline earth cations to shift the conductance-voltage curves of a nerve along the voltage axis by 20–26 mv for a 10-fold increase in concentration may be due to essentially a screening rather than a binding phenomenon.
600 citations
TL;DR: 125I-insulin binding to liver membranes was inhibited by unlabeled insulin at physiological concentrations, and monoiodoinsulin prepared by this method was bound to isolated fat cells and to purified plasma membranes from liver.
552 citations
522 citations
TL;DR: Comparison of the Triton-soluble and TritOn-insoluble proteins from the cell wall and cytoplasmic membrane fractions by polyacrylamide gel electrophoresis and gel filtration in acidified dimethyl formamide indicated that the detergent specifically solubilized proteins of the cy toplasmi membrane.
Abstract: Treatment of a partially purified preparation of cell walls of Escherichia coli with Triton X-100 at 23 C resulted in a solubilization of 15 to 25% of the protein. Examination of the Triton-insoluble material by electron microscopy indicated that the characteristic morphology of the cell wall was not affected by the Triton extraction. Contaminating fragments of the cytoplasmic membrane were removed by Triton X-100, including the fragments of the cytoplasmic membrane which were normally observed attached to the cell wall. Treatment of a partially purified cytoplasmic membrane fraction with Triton X-100 resulted in the solubilization of 60 to 80% of the protein of this fraction. Comparison of the Triton-soluble and Triton-insoluble proteins from the cell wall and cytoplasmic membrane fractions by polyacrylamide gel electrophoresis after removal of the Triton by gel filtration in acidified dimethyl formamide indicated that the detergent specifically solubilized proteins of the cytoplasmic membrane. The proteins solubilized from the cell wall fraction were qualitatively identical to those solubilized from the cytoplasmic membrane fraction, but were present in different proportions, suggesting that the fragments of cytoplasmic membrane which are attached to the cell wall are different in composition from the remainder of the cytoplasmic membrane of the cell. Treatment of unfractionated envelope preparations with Triton X-100 resulted in the solubilization of 40% of the protein, and only proteins of the cytoplasmic membrane were solubilized. Extraction with Triton thus provides a rapid and specific means of separating the proteins of the cell wall and cytoplasmic membrane of E. coli.
506 citations
TL;DR: Each membrane is found to have an identifiable glycoprotein subunit pattern composed of at least 6 to 11 different sized subunits, and most of the staining intensity is present in one to three subunits.
TL;DR: A glycoprotein has been extracted in water-soluble form from human red cell membranes with lithium diiodosalicylate and obtained a homogeneous preparation which contains AB and MN blood group antigens, receptors for influenza virus, and various phytohemagglutinins.
Abstract: A glycoprotein has been extracted in water-soluble form from human red cell membranes with lithium diiodosalicylate. After extraction of the membranes and phosphocellulose chromatography a homogeneous preparation is obtained which was 60 percent carbohydrate and 40 percent protein (by weight). The preparation contains AB and MN blood group antigens, receptors for influenza virus, and various phytohemagglutinins.
TL;DR: Plasma membranes prepared from rat livers treated with digitonin or phospholipase A under conditions which result in substantial loss of glucagon- Stimulated adenyl cyclase activity but no loss of fluoride-stimulated activity are thought to reflect extensive modification of the structures responsible for hormone sensitivity without destruction of the catalytic component of the adeny cyclase system.
TL;DR: Fractionation by aqueous two-phase polymer systems appears to be a rapid and effective method for the isolation of surface membranes.
Abstract: A dextran-polythylene glycol aqueous two-phase system has been used to separate cell surface membranes from other cellular organelles. The surface membranes have been identified on the basis of morphology, content of Na+, K+-ATPase, and presence of surface antigen as detected by a51Cr release method. Contamination of the surface membrane preparations by smooth endoplasmic reticulum, mitochondria, and nuclei has been found to be minimal. An average of 6.5% of the total protein was found in the membrane fraction. Less than two hours is required to isolate the membrane fraction after preparation of a Dounce homogenate. Fractionation by aqueous two-phase polymer systems appears to be a rapid and effective method for the isolation of surface membranes.
TL;DR: The structure of the purple membrane and its localization in the bacterial cell envelope are described and it is shown that it contains retinal bound in a mole ratio of 1 : 1 to a protein of molecular weight 26,000 which is the only protein present.
Abstract: IN the preceding article1 it has been shown that a cell membrane fragment, the purple membrane, isolated from Halobacterium halobium2 contains retinal bound in a mole ratio of 1 : 1 to a protein of molecular weight 26,000 which is the only protein present. We now describe the structure of the purple membrane and its localization in the bacterial cell envelope.
TL;DR: The polypeptide part of the principal glycoprotein on the surface of human erythrocytes extends through the membrane barrier to the interior surface of the cell membrane.
Abstract: The polypeptide part of the principal glycoprotein on the surface of human erythrocytes extends through the membrane barrier to the interior surface of the cell membrane.
TL;DR: A model for the flow of molecules through lipid membranes based on thermal fluctuations in the hydrocarbon chains of the membrane lipids results in the formation of conformational isomers, so-called kink-isomers of the hydro carbon chains.
Abstract: The movement of molecules across membranes is discussed in terms of thermal fluctuations in the hydrocarbon chains of the membrane lipids. The thermal motion of the hydrocarbon chains results in the formation of conformational isomers, so-called kink-isomers of the hydrocarbon chains. “Kinks” may be pictured as mobile structural defects which represent small, mobile free volumes in the hydrocarbon phase of the membrane. The diffusion coefficient of kinks is calculated to be 10−5 cm2/sec; thus kinks diffusion is a fast process. Small molecules can enter into the free volumes of kinks and migrate across the membrane together with the kinks; thus kinks may be regarded as intrinsic carriers of lipid membranes. An expression is derived from this model for the flow of molecules through lipid membranes. The calculated value for the water permeability is compatible with measurements on lipid bilayers.
TL;DR: Evidence is presented to identify plasma membranes of liver as the major locus of binding for circulating glycoproteins and the binding process involves a dual role for sialic acid in that its presence on the membranes is essential, whereas its existence on the glycoprotein is incompatible with binding.
TL;DR: X-ray diffraction studies show that lipid hydrocarbon chains are uniformly packed in bilayers and oriented so that their free ends are near the centre, which provides a model for biological membranes.
Abstract: X-ray diffraction studies show that lipid hydrocarbon chains are uniformly packed in bilayers and oriented so that their free ends are near the centre. This provides a model for biological membranes.
TL;DR: Molecular motion data from a spin-labeled fatty acid presented on Arrhenius graphs allow melting points or phase transitions to be inferred in local domains such as membranes and indicate that some membrane-bound enzymes are sensitive to the physical state of membrane lipids.
TL;DR: The action of thrombin on intact human platelets has been studied with the aid of polyacrylamide gel electrophoresis in sodium dodecylsulfate and suggests that hydrolysis of this membrane protein may trigger the physiological effects of thROMbin on platelets.
Abstract: The action of thrombin on intact human platelets has been studied with the aid of polyacrylamide gel electrophoresis in sodium dodecylsulfate. A single major membrane protein band with a molecular weight of 190,000 disappears after thrombin treatment, while a new membrane protein with a molecular weight of 107,000 appears. This may represent hydrolysis of the thrombin-sensitive protein. When platelets are disrupted or when the thrombin-sensitive protein is solubilized from membranes prior to thrombin treatment, no hydrolysis occurs. The effect of thrombin on the platelet membrane protein is complete within 2 min which suggests that hydrolysis of this membrane protein may trigger the physiological effects of thrombin on platelets.
TL;DR: Putative neuronal membrane markers, gangliosides and sodium, potassium-dependent ATPase, were enriched over 10-fold in these membranes in comparison to the homogenate, which suggests some contamination with glial cell plasma membrane.
TL;DR: Diffraction analysis of dispersions of membranes makes it possible to study membranes not in regular arrays and shows that a phospholipid bilayer is a predominant structural component of membranes with various different functions.
Abstract: Diffraction analysis of dispersions of membranes makes it possible to study membranes not in regular arrays. Such analysis shows that a phospholipid bilayer is a predominant structural component of membranes with various different functions.
TL;DR: Evidence is presented that the transport of lipid-soluble ions through bilayer membranes occurs in three distinct steps: adsorption to the membranesolution interface; passage over an activation barrier to the opposite interface; and desorption into the aqueous solution.
Abstract: Evidence is presented that the transport of lipid-soluble ions through bilayer membranes occurs in three distinct steps: (1) adsorption to the membranesolution interface; (2) passage over an activation barrier to the opposite interface; and (3) desorption into the aqueous solution Support for this mechanism comes from a consideration of the potential energy of the ion, which has a minimum in the interface The formal analysis of the model shows that the rate constants of the individual transport steps can be determined from the relaxation of the electric current after a sudden change in the voltage Such relaxation experiments have been carried out with dipicrylamine and tetraphenylborate as permeable ions In both cases the rate-determining step is the jump from the adsorption site into the aqueous phase Furthermore, it has been found that with increasing ion concentration the membrane conductance goes through a maximum In accordance with the model recently developed by L J Bruner, this behavior is explained by a saturation of the interface, which leads to a blocking of the conductance at high concentrations
TL;DR: Chromatographic studies on CM-cellulose of collagens isolated from basement membranes of the glomerulus, lens capsule and Descemet's membrane indicate that the molecule is composed of three identical α -1 chains.
TL;DR: It is concluded that the purified ATPase enzyme is a functional subunit and is likely to be a structural subunit of the sarcoplasmic reticulum membrane.
TL;DR: An electron microscopic stain for specific saccharides was prepared by the conjugation of ferritin to concanavalin A, a plant agglutinin that specifically binds to oligosaccharides containing terminal d-glucose, d-mannose, or sterically related sugar residues.
Abstract: An electron microscopic stain for specific saccharides was prepared by the conjugation of ferritin to concanavalin A, a plant agglutinin that specifically binds to oligosaccharides containing terminal d-glucose, d-mannose, or sterically related sugar residues A technique was developed to allow topological visualization of erythrocyte and other membranes by means of transmission electron microscopy, and the distribution of the binding sites for ferritin-concanavalin A on such membrane preparations was determined The conjugate was found to bind specifically to the outer, but not the inner, surface of erythrocyte membranes The number of conjugate molecules bound per unit area of the membrane was larger for rabbit than for human erythrocytes
TL;DR: A very reactive, highly radioactive reagent designed to acylate amino groups has been synthesized: this compound, the sulphone of 35 S-labelled formylmethionyl methyl phosphate, cannot pass through the red blood cell membrane.
TL;DR: It is concluded that dicyclohexylcarbodi-imide inhibits mitochondrial oxidative phosphorylation by reacting covalently with a group on this chloroform–methanol-soluble protein.
Abstract: Mitochondrial membranes were incubated with NN′-dicyclohexyl[14C]carbodi-imide, which irreversibly inhibited the partial reactions of oxidative phosphorylation by 95–100%. Solutions of the membranes were analysed on polyacrylamide gels. Of the radioactivity recovered from the gels 90% was shown to be associated with a single protein of molecular weight about 10000. The radioactive protein and associated phospholipid was solubilized from the membrane by extraction with chloroform–methanol mixtures and was concentrated 50-fold by solvent fractionation and adsorption chromatography on Sephadex LH-20. Several protein–radioactivity peaks were obtained by Sephadex LH-20 chromatography. However, 90–100% of the radioactivity in each peak was shown to be associated with a single protein similar to the major radioactive protein observed in electrophoretograms of the membrane solutions. It is concluded that dicyclohexylcarbodi-imide inhibits mitochondrial oxidative phosphorylation by reacting covalently with a group on this chloroform–methanol-soluble protein. The possible role of this protein in oxidative phosphorylation is discussed.
TL;DR: The results suggest that the temperature-induced change in activation energy of the membrane-bound enzymes is associated with a phase change in the lipid component of the membranes which induces a configurationalchange in the enzyme proteins.