Showing papers on "Membrane lipids published in 1976"
TL;DR: The results indicate that Escherichia coli cells radically change their fatty acid composition when grown in the presence of alcohols, which represents an adaptive membrane alteration compensating for the direct physicochemical interaction ofcohols with the membrane.
Abstract: The effects of alcohols of different chain lengths on the fatty acid composition of Escherichia coli K-12 have been examined. My results indicate that these cells radically change their fatty acid composition when grown in the presence of alcohols. These changes represent an adaptive membrane alteration compensating for the direct physicochemical interaction of alcohols with the membrane. Similar adaptive responses of membrane lipids are proposed as a possible biochemical basis for tolerance to alcohol and related drugs.
477 citations
TL;DR: Findings strongly suggest that membrane proteins may be vertically displaced upon changes in lipid fluidity, a mechanism that may play a significant role in modulation of antigens and receptors in vivo.
Abstract: Membrane proteins of intact human erythrocytes were labeled with two fluorescent sulfhydryl reagents. The tagged cells were then subjected to simultaneous liposome treatments for either depletion or enrichment of membrane cholesterol content. Cholesterol depletion, which reduces membrane microviscosity, was followed by a series of fluorescence changes all indicating masking of the membrane proteins. Conversely increasing the membrane microviscosity by cholesterol enrichment resulted in an appreciable increase of the protein exposure to the aqueous surrounding. These findings strongly suggest that membrane proteins may be vertically displaced upon changes in lipid fluidity, a mechanism that may play a significant role in modulation of antigens and receptors in vivo.
233 citations
TL;DR: The change in order of lipid molecules surrounding a protein leads to an indirect, lipid-mediated interaction between membrane integral proteins and the surrounding lipids, which depends sensitively on the bulk lipid order.
232 citations
TL;DR: This work suggests that extensive precautions against oxidative degradation should also be employed in studies of other membrane systems where important deleterious effects of oxygen may be less obvious.
211 citations
TL;DR: A model for increasing solidification of lipid around protein molecules or cholesterol above the transition temperature of the lipid is discussed and Phase diagrams for lipid/cholesterol and lipid/protein systems are proposed which account for many of the available data.
208 citations
TL;DR: The action of neurohormones and drugs on polar lipids of the nervous system has mainly been explored by measuring the 32P metabolism, but studies regarding the hydrophobic moiety of membrane lipids were limited to survey the fatty acid distribution and the uptake of labeled precursors.
Abstract: The action of neurohormones and drugs on polar lipids of the nervous system has mainly been explored by measuring the 32P metabolism (1). Hence studies regarding the hydrophobic moiety of membrane lipids were limited to survey the fatty acid distribution and the uptake of labeled precursors. Moreover very scarce information is available on lipid degradative enzymes acting on endogenous substrates and on the composition, concentration and changes taking place in endogenous lipid pools related with the non-polar side chains of membrane lipids.
200 citations
TL;DR: Thalassemic erythrocytes contain more lipid per cell which is susceptible to peroxidation, and the distribution of fatty acids in these cells suggests that autooxidation of that lipid may have occurred.
174 citations
TL;DR: Evidence is presented here that the electron spin resonance techniques used previously did not in fact detect the gel to liquid-crystalline phase transition of the bulk membrane lipids, which, however, can be reliably measured by differential thermal analysis.
120 citations
TL;DR: The results demonstrate a precise relationship between changes in the molecular ordering of membrane lipids and the physiological response of plants to changes in temperature.
Abstract: Changes in the growth response of mung bean hypocotyl were studied as a function of temperature and related to structural and functional changes in membranes. The temperature coefficient for growth increased abruptly below 28°C and again below 15°C. The Arrhenius activation energy of mitochondrial succinate oxidase also increased below these same temperatures. Changes in molecular ordering were detected in the membrane lipids of both mitochondria and chloroplasts at about 28 and 15°C by electron spin resonance spectroscopy. The results demonstrate a precise relationship between changes in the molecular ordering of membrane lipids and the physiological response of plants to changes in temperature.
115 citations
TL;DR: A re-examination of the conditions under which water and electrolytes leak from the leaves of P. vulgaris indicates that phase changes in the membrane lipids of the plasmalemma and other organelles at 5° C are only of minor importance in determining the extent and speed of chilling-injury.
Abstract: SUMMARY
Drought-hardening at 25° C, 40% R.H. by witholding water from the roots for 4 days is as effective in preventing chilling-injury to the leaves of Phaseolus vulgaris as 4 days chill-hardening at 12° C, 85% R.H. During chill-hardening the degree of unsaturation of the fatty acids associated with the phospholipids increased and this was considered to prevent water loss and electrolyte leakage by lowering the temperature at which phase changes occur in the membrane lipids to below 5° C (Wilson and Crawford, 1974b). However, drought-hardening at 25° C, 40% R.H. resulted in no increase in the degree of unsaturation of the phospholipids or glycolipids suggesting that lipid phase changes are not the primary cause of chilling-injury. Furthermore, a re-examination of the conditions under which water and electrolytes leak from the leaves of P. vulgaris indicates that phase changes in the membrane lipids of the plasmalemma and other organelles at 5° C are only of minor importance in determining the extent and speed of chilling-injury. The primary cause of chilling-injury to P. vulgaris leaves on transfer from 25° C, 85% R.H. to 5° C, 85% R.H. is leaf dehydration due to the opening of the stomata at a time when the permeability of the roots to water is low. The primary factor inducing hardening against chilling-injury in P. vulgaris is a water stress and not low temperature per se.
113 citations
TL;DR: Peroxidation of membrane lipids by this system is equally effective in both intact microsomes and in liposomes, indicating that iodination of microsomal protein is not required for lipid peroxidation to occur.
TL;DR: The results emphasize the importance of the membrane lipid phase for this enzyme, which was examined in mouse LM cell (fibroblast) membranes that were supplemented with ethanolamine and/or fatty acids and incorporated into the plasma membrane phospholipids in significant amounts.
Abstract: Adenylate cyclase [atp pyrophosphate-lyase (cyclizing): EC 4.6.4.4] activities were examined in mouse LM cell (fibroblast) membranes that were supplemented with ethanolamine and/or fatty acids. The supplements were incorporated into the plasma membrane phospholipids in significant amounts. Fatty acid supplementations had distinct effects as compared to polar head group supplementations. All lipid supplementations increased basal adenylate cyclase activity relative to control cells grown in choline-containing medium. Double supplementation with ethanolamine and linoleate increased the specific activity of adenylate cyclase up to 4-fold. Activity in the presence of fluoride was unaffected by ethanolamine supplementation, but was increased by fatty acid supplementation. In contrast, prostaglandin E1 stimulation was 4.2-fold in controls and ethanolamine and/or elaidate supplements, 6-fold in choline plus linoleate supplements, and 3.1-fold in ethanolamine plus linoleate supplements. Differences in activity could not be ascribed to changes in membrane protein composition in supplemented cells, and could be abolished by detergent solublization. Fluidity of the supplemented membranes was monitored by fluorescence polarization, and no correlation was observed between membrane viscosity and adenylate cyclase activity or hormone stimulation. These results emphasize the importance of the membrane lipid phase for this enzyme.
TL;DR: The thermal effects observed on functional parameters and on the character of phospholipid molecular motion exhibit a parallel behavior, suggesting a relationship between enzyme activity and the physical state of the membrane lipids.
Abstract: In biochemically active sarcoplasmic reticulum vesicles (SR) the physical state of the membrane lipids was studied by high angle x-ray diffraction and proton nuclear magnetic resonance (NMR) at 220 MHz, and related to thermal effects observed in SR functional parameters. It is shown by high angle x-ray diffraction that even at temperatures as low as 1 degree C nearly all the SR lipid hydrocarbon chains are in a disordered conformation and only a very small part (less than 3%) are in rigid crystalline order. Consistent with this observation, the NMR data indicate that the majority of SR phospholipid molecules are in a state of restricted anisotropic motion having no apparent crystalline order at temperatures as low as 5 degrees C. At this temperature most of the resonance signal is contained in a broad feature-less line of 700-Hz half-width. On the other hand, as the temperature is raised, high-resolution NMR signals, representing groups with highly isotropic motion, begin to grow in intensity. It is estimated that by 35 degrees C 90-100% of the phosphatidylcholine N-methyl protons and 35% of the hydrocarbon-chain protons give high-resolution signals. Concurrent studies on functional parameters reveal thermal effects giving rise to nonlinear Arrhenius plots for the rates of calcium transport and calcium activated ATPase. The thermal effects observed on functional parameters and on the character of phospholipid molecular motion exhibit a parallel behavior, suggesting a relationship between enzyme activity and the physical state of the membrane lipids.
TL;DR: The fluorescence probe 1,6-diphenyl-1,3,5-hexatriene was used to study and compare the dynamic properties of the hydrophobic region of vesicular stomatitis virus, plasma membrane of L-929 cells prepared by two different methods, liposomes prepared from virus lipids and plasma membrane lipids, and intact L- 929 cells.
Abstract: The fluorescence probe 1,6-diphenyl-1,3,5-hexatriene was used to study and compare the dynamic properties of the hydrophobic region of vesicular stomatitis virus grown on L-929 cells, plasma membrane of L-929 cells prepared by two different methods, liposomes prepared from virus lipids and plasma membrane lipids, and intact L-929 cells. The rate of penetration of the probe into the hydrophobic region of the lipid bilayer was found to be much faster in the lipid vesicle bilayer as compared with the intact membrane, but in all cases the fluorescence anisotropy was constant with time. The L-cell plasma membranes, the vesicles prepared from the lipids derived from the plasma membranes, and intact cells are found to have much lower microviscosity values than the virus or virus lipid vesicles throughout a wide range of temperatures. The microviscosity of plasma membrane and plasma membrane lipid vesicles was found to depend on the procedure for plasma membrane preparation as the membranes prepared by different methods had different microviscosities. The intact virus and liposomes prepared from the virus lipids were found to have very similar microviscosity values. Plasma membrane and liposomes prepared from plasma membrane lipids also had similar microviscosity values. Factors affecting microviscosity in natural membranes and artificially mixed lipid membranes are discussed.
TL;DR: In this investigation, data on phosphatidylserine-induced effects in vivo are presented and it is shown that sonicated dispersion of bovine brain phospholipids can induce in mice modification of glucose distribution.
Abstract: PHARMACOLOGICAL studies on diacylphospholipids develop along two lines of investigation. In the first, preparations of liposomes are used as carriers of drugs either bound to the bilayer or entrapped inside the vesicles. Sonicated liposomes have been shown to be able to transport inhibitors or drugs to target sites in vitro1 and in vivo2. In the second, liposome preparations are administered and pharmacological effects are recorded. In this context significant effects have been observed on cholesterol distribution5. The molecular mechanism underlying the possibility of pharmacological effects in vivo by long chain diacylphospholipids is indicated by a series of investigations4–7 showing the capacity of phospholipid vesicles to fuse with cellular membrane in vitro. As a consequence of changed composition of membrane lipids, alteration in the permeability properties, transport systems and other functions of biological membranes are expected to occur. It has been shown8 that sonicated dispersion of bovine brain phospholipids can induce in mice modification of glucose distribution. Purification of lipid mixtures indicated that phosphatidylserine was one of the active components. Phosphatidylserine liposomes have shown great capability to interact in vitro with biologically active compounds (histamine9 or calcium10), with phospholipid-dependent enzymatic systems (Na+–K+-stimulated ATPase11 or tyrosine hydroxylase12), or with intact cells (enhancement of histamine release during antigen–antibody interaction13; promotion of cell fusion4). In this investigation data on phosphatidylserine-induced effects in vivo are presented.
TL;DR: It is demonstrated that Escherichia coli normally maintains a heterogeneous mixture of lipid molecules and, by so doing, prevents strong lipid-lipid associations that lead to the formation of lipid domains in the membrane.
Abstract: Differential scanning calorimetry (DSC) and electron spin resonance (ESR) measurements were made to characterize how modifications in the fatty acid composition of Escherichia coli affected the thermotropic phase transition(s) of the membrane lipd. When the fatty acid composition contained between 20 and 60% saturated fatty acids, the DSC curves for isolated phospholipids and cytoplasmic membranes showed a broad (15-25 degree C) gel to liquid-crystalline phase transition, the position of which depended on the particular fatty acid composition. Utilizing multiple lipid mutants, enrichment of the membrane phospholipids with a single long-chain cis-monoenoic fatty acid in excess of that possible in a fatty acid levels less than 20% and gradually replaced the broad peak as the cis-monoenoic fatty acid content increased. These results were obtained with phospholipids, cytoplasmic membranes, and whole cells. With these same phopholipids, plots of 2,2,6,6-tetramethylpiperidinyl-1-oxy partitioning and ESR order parameters vs. 1/T revealed discontinuities at temperatures 40-60 degrees C above the calorimetrica-ly measured gel to liquid-crystalline phase transitions. Moreover, when the membrane phospholipids were enriched with certain combinations of cis-monenoic fatty acids (e.g., cis-delta 9-16:1 plus cis-delta 11-18:1) the DSC curve showed a broad gel to liquid crystalline phase change below 0 degrees C but the ESR studies revealed no discontinuities at temperatures above those of the gel to liquid-crystalline transition. These results demonstrated that enrichment of the membrane lipids with molecules in which both fatty acyl chains are identical cis-monoenoic residues led to a distinct type of liquid-crystalline phase. Furthermore, a general conclusion from this study is that Escherichia coli normally maintains a heterogeneous mixture of lipid molecules and, by so doing, prevents strong lipid-lipid associations that lead to the formation of lipid domains in the membrane.
TL;DR: Lipid peroxidation was increased in the cells by the addition of either NADPH or CCl4, and the effect of the two agents together was more than additive; however, Mitochondrial fatty acids were not decreased by any treatments described.
TL;DR: A correlation was found between dephosphorylation of chicken erythrocyte membrane proteins, aggregation of intramembrane particles, increase in the lipid bilayer phase of the membrane and exposure of membrane phospholipids toward phospholIPase A and trinitrobenzene sulfonic acid.
TL;DR: The results obtained emphasize that the close biochemical similarities noted between rER and nuclear membranes of animal cells extend to these fractions from plant cells.
Abstract: Nuclei, nuclear membranes and rough endoplasmic reticulum (rER) were isolated from onion root tips and stems. Structural preservation and purity of the fractions was determined by electron microscopic and biochemical methods. Gross compositional data (protein, phospholipid, nonpolar lipids, sterols, RNA, DNA), phospholipid and fatty acid patterns, enzyme activities (ATPases, ADPase, IDPase, glucose-6-phosphatase, 5'-nucleotidase, acid phosphatase, and NADH- and NADPH-cytochrome C reductases), and cytochrome contents were determined. A stable, high salt-resistant attachment of some DNA with the nuclear membrane was observed as well as the association of some RNA with high salt-treated nuclear and rER membranes. The phospholipid pattern was identical for both nuclear and rER membranes and showed a predominance of lecithin (about 60%) and phosphatidyl ethanolamine (20-24%). Special care was necessary to minimize lipid degradation by phospholipases during isolations. Nonpolar lipids, mostly sterols and triglycerides, accounted for 35-45% of the membrane lipids. Sterol contents were relatively high in both membrane fractions (molar ratios of sterols to phospholipids ranged from 0.12 to 0.43). Sitosterol accounted for about 80% of the total sterols. Palmitic, oleic, and linoleic acids were the most prevalent acids in membrane-bound lipids as well as in storage lipids and occurred in similar proportions in phospholipids, triglycerides and free fatty acids of the membrane. About 80% of the fatty acids in membrane phospholipids and triglycerides were unsaturated. A cytochrome of the b5 type was characterized in these membranes, but P-450-like cytochromes could not be detected. Both NADH and NADPH-cytochrome c reductases were found in nuclear and rER membranes and appeared to be enriched in rER membranes. Among the phosphatases, Mg2+-ATPase and, to lesser extents, ADPase, IDPase and acid phosphatase activities occurred in the fractions, but significant amounts of monovalent ion-stimulated ATPase, 5'-nucleotidase and glucose-6-phosphatase activities did not. The results obtained emphasize that the close biochemical similarities noted between rER and nuclear membranes of animal cells extend to these fractions from plant cells.
TL;DR: It has been shown that cardiotoxin first associates rapidly and reversibly to membrane lipids, then, in a second step, it induces a rearrangement of the membrane structure which produces and irreversible deactivation of the sodium-potassium activated adenosine triphosphatase.
Abstract: Cardiotoxin isolated from Naja mossambica mossambica selectively deactivates the sodium-potassium activated adenosine triphosphatase of axonal membranes. Tetrodotoxin binding and acetylcholinesterase activities are unaffected by cardiotoxin treatment. The details of association of cardiotoxin with the axonal membrane were studied by following the deactivation of the sodium-potassium activated adenosine triphosphatase and by direct binding measurements with a tritiated derivative of the native cardiotoxin. The maximal binding capacity of the membrane is 42-50 nmol of cardiotoxin/mg of membrane protein. The high amount of binding suggests association of the toxin with the lipid phase of the membrane. It has been shown that cardiotoxin first associates rapidly and reversibly to membrane lipids, then, in a second step, it induces a rearrangement of the membrane structure which produces and irreversible deactivation of the sodium-potassium activated adenosine triphosphatase. Solubilization of the membrane-bound ATPase with Lubrol WX gives an active enzyme species that is resistant to cardiotoxin-induced deactivation. Cardiotoxin binding to the membrane is prevented by high concentrations of Ca 2+ and dibucaine. Although cardiotoxins and neurotoxins of cobra venom have large sequence homologies, their mode of action on membranes is very different. The cardiotoxin seems to bind to the lipid phase of the axonal membrane and inhibits the sodium-potassium activated adenosine triphosphatase, whereas the neurotoxin associates with a protein receptor in the post-synaptic membrane and blocks acetylcholine transmission.
01 Jan 1976
TL;DR: It appears that LM cells maintain the characteristic temperatures which are a measure of the physical properties of their membranes, despite large alterations of the phospholipid polar head group composition.
TL;DR: Data negate one criterion of the theory that an asymmetric distribution of characteristic temperatures exist across the membranes of LM cells.
TL;DR: It is postulated that biguanides act only on membranes and by alteration of membrane properties in general by the demonstrated generation of a positive surface potential, which provides a unique molecular basis for an understanding of the large variety of biguanide effects.
TL;DR: The degree of membrane fluidity of normal and leukemic lymphocyte populations both from experimental animals and humans is determined and a marked increase in the fluidity in the surface membrane lipid core of the malignant cells is revealed.
TL;DR: It was established that sufficient exogenous lipid was associated with the membrane to account for the enhancement of opiate binding, and it was suggested that phosphatidyl serine may be an important component of the opiate pharmacophore.
TL;DR: The development of the changes in fatty acid composition occurred relatively slowly in the course of transformation, indicating that the observed compositional alterations are not likely to be a primary cause of the early changes in membrane function associated with malignant transformation.
Abstract: The acyl group composition of the phospholipids from normal chick embryo fibroblasts and from cells transformed by Rous sarcoma virus was determined by gas-liquid chromatography. Rous-transformed cells had less arachidonate (20:4) and more oleate (18:1) in membrane lipids than normal, growing cells. Normal density-inhibited cells had the lowest ratio of 18:1/20:4. Associated with the decreased content of 20:4 in the transformed cells was a decreased motional freedom of an incorporated spin-labeled fatty acid analogue. Arrhenius plots for uptake of 2-deoxyglucose revealed an increased apparent activation energy in the transformed cells, suggesting that the hexose transport carriers were sensitive to the changes in membrane composition and structure in fully transformed cells. However, the development of the changes in fatty acid composition occurred relatively slowly in the course of transformation, indicating that the observed compositional alterations are not likely to be a primary cause of the early changes in membrane function associated with malignant transformation.
TL;DR: The activation of C55-isoprenoid alcohol phosphokinase by a variety of lipids has been investigated in this paper, and the structure of those lipids which are most effective, as well as an analysis of their temperature profiles, suggests that bulk physical properties are significant.
TL;DR: An attempt to understand the mechanism by which a structural transition in the membrane lipids of a bacterial cytoplasmic membrane affects the transport functions of the membrane.