Studies on the purified Na+,Mg2+-ATPase from Acholeplasma laidlawii B membranes: a differential scanning calorimetric study of the protein–phospholipid interactions

1990 ◽  
Vol 68 (1) ◽  
pp. 161-168 ◽  
Author(s):  
Rajan George ◽  
Ruthven N.A.H. Lewis ◽  
Ronald N. McElhaney
Keyword(s):  
Phase Transition ◽  
Liquid Crystalline ◽  
Lipid Phase ◽  
Scanning Calorimetry ◽  
Lipid Phase Transition ◽  
Acholeplasma Laidlawii ◽  
Lipid Ratios ◽  
Dimyristoyl Phosphatidylcholine ◽  
Transition Enthalpy ◽  
Crystalline Phase Transition

The purified Na+, Mg2+-ATPase from the Acholeplasma laidlawii B plasma membrane was reconstituted with dimyristoyl phosphatidylcholine and the lipid thermotropic phase behavior of the proteoliposomes formed was investigated by differential scanning calorimetry. The effect of this ATPase on the host lipid phase transition is markedly dependent on the amount of protein incorporated. At low protein/lipid ratios, the presence of increasing quantities of ATPase in the proteoliposomes increases the temperature and enthalpy while decreasing the cooperativity of the dimyristoyl phosphatidylcholine gel to liquid–crystalline phase transition. At higher protein/lipid ratios, the incorporation of increasing amounts of this enzyme does not further alter the temperature and cooperativity of the phospholipid chain-melting transition, but progressively and markedly decreases the transition enthalpy. Plots of lipid phase transition enthalpy versus protein concentration suggest that at the higher protein/lipid ratios each ATPase molecule removes approximately 1000 dimyristoyl phosphatidylcholine molecules from participation in the cooperative gel to liquid–crystalline phase transition of the bulk lipid phase. These results indicate that this integral transmembrane protein interacts in a complex, concentration-dependent manner with its host phospholipid and that such interactions involve both hydrophobic interactions with the lipid bilayer core and electrostatic interactions with the lipid polar head groups at the bilayer surface.Key words: Acholeplasma laidlawii B, Na+,Mg2+-ATPase, differential scanning calorimetry, lipid-protein interactions.

Synthesis, characterisation and liquid-crystalline phase transition studies on two higher homologues of 4O.m (m=14 and 16) series

2001 ◽  
Vol 709 ◽  
Author(s):  
C. Rama Chandra Prabhu ◽  
V.G.K.M. Pisipati
Keyword(s):  
Phase Transition ◽  
Liquid Crystalline ◽  
Scanning Calorimetry ◽  
First Order ◽  
Smectic A ◽  
Phase Transition Temperatures ◽  
Crystalline Phase Transition ◽  
M 14 ◽  
Enthalpy Data ◽  
Transition Studies

ABSTRACTThe synthesis, characterization and phase transition studies of higher homologues of N(p-nbutoxybenzylidene)p-n-alkylanilines, Viz., 4O.m series (m=14 and 16) are carried out by thermal microscopy, differential scanning calorimetry and density. The compounds exhibit a phase variant of nematic and smectic-A. Density studies reveal a first order nature of IN transitions and a weak first order NA transitions. An estimate of pressure dependence of the phase transition temperatures using the volume and enthalpy data are presented. A comparison of these results with other reported results in nO.m and other compounds are presented.

Reconstitution of the glycosylphosphatidylinositol-anchored protein Thy-1: interaction with membrane phospholipids and galactosylceramide

1999 ◽  
Vol 77 (3) ◽  
pp. 189-200 ◽  
Author(s):  
Kara L Reid-Taylor ◽  
Joseph WK Chu ◽  
Frances J Sharom
Keyword(s):  
Phase Transition ◽  
Differential Scanning Calorimetry ◽  
Lipid Bilayer ◽  
Liquid Crystalline ◽  
Membrane Surface ◽  
Membrane Phospholipids ◽  
Scanning Calorimetry ◽  
Transition Enthalpy ◽  
Striking Change ◽  
Lipid Bilayer Vesicles

Glycosylphosphatidylinositol (GPI)-anchored membrane proteins are proposed to interact preferentially with glycosphingolipids and cholesterol to form microdomains, which may play an important role in apical targeting and signal transduction. The objective of the present study was to investigate the interaction of the GPI-anchored protein Thy-1 with phospholipids and a glycosphingolipid. Purified Thy-1 was reconstituted into lipid bilayer vesicles of dimyristoyl-phosphatidylcholine (DMPC) alone or in combination with galactosylceramide (GC). The ability of Thy-1 to perturb the gel to a liquid-crystalline phase transition of DMPC was examined by differential scanning calorimetry. As the mole fraction of Thy-1 increased, the phase transition enthalpy, deltaH, declined. Analysis indicated that each molecule of Thy-1 perturbed over 50 phospholipids, suggesting that, in addition to the anchor insertion into the bilayer, the protein itself may interact with the membrane surface. Inclusion of 5% w/w GC in the bilayer resulted in a striking change in the interaction of Thy-1 with phospholipids. At low Thy-1 content, there was a reduction in the phase transition temperature and an increase in phospholipid cooperativity, suggesting the formation of Thy-1/GC-enriched domains. deltaH initially decreased with increasing Thy-1 content of the bilayer; however, at higher Thy-1 mole ratios, deltaH rose again. These results are interpreted in terms of a model whereby, at low protein:lipid mole ratios, Thy-1 preferentially sequesters GC to form enriched microdomains. At high protein:lipid mole ratios, Thy-1 may alter its conformation in response to steric crowding within these domains such that its interaction with the bilayer surface is reduced.Key words: glycosylphosphatidylinositol anchor, Thy-1 antigen, reconstitution, lipid bilayer, glycosphingolipid, differential scanning calorimetry, dynamic light scattering.

scholarly journals Verapamil prevents the effects of daunomycin on the thermotropic phase transition of model lipid bilayers

1991 ◽  
Vol 279 (2) ◽  
pp. 413-418 ◽  
Author(s):  
J M Canaves ◽  
J A Ferragut ◽  
J M Gonzalez-Ros
Keyword(s):  
Phase Transition ◽  
Lipid Bilayer ◽  
Lipid Bilayers ◽  
Drug Binding ◽  
Lipid Phase ◽  
Dependent Manner ◽  
Binding Studies ◽  
Scanning Calorimetry ◽  
Lipid Phase Transition ◽  
Fluorescence Depolarization

High-sensitivity differential scanning calorimetry and fluorescence-depolarization techniques were used to study how the presence of daunomycin and/or verapamil affect the thermotropic behaviour of dipalmitoyl phosphatidylcholine (DPPC) vesicles. Daunomycin, a potent anti-cancer agent, perturbs the thermodynamic parameters associated with the lipid phase transition: it decreases the enthalpy change, lowers the transition temperature and reduces the co-operative behavior of the phospholipid molecules. Verapamil, on the other hand, produces smaller alterations in the lipid phase transition. However, when daunomycin and verapamil are present simultaneously in the DPPC vesicles, it is observed that verapamil prevents, in a concentration-dependent manner, the alteration in the phospholipid phase transition expected from the presence of daunomycin in the bilayer. Furthermore, drug-binding studies suggest that the observed interference of verapamil in the daunomycin/phospholipid interaction occurs without a decrease in the amount of daunomycin bound to the lipid bilayer and without the formation of a daunomycin-verapamil complex. Because of the importance of drug-membrane interactions in anthracycline cytotoxicity, we speculate that the lipid bilayer of biological membranes may provide appropriate sites at which the presence of verapamil influences the activity of daunomycin.

Fatty acyl chain structure, orientational order, and the lipid phase transition in Acholeplasma laidlawii B membranes. A review of recent 19F nuclear magnetic resonance studies

1984 ◽  
Vol 62 (11) ◽  
pp. 1134-1150 ◽  
Author(s):  
P. M. Macdonald ◽  
B. D. Sykes ◽  
R. N. McElhaney
Keyword(s):  
Phase Transition ◽  
Fatty Acids ◽  
Nuclear Magnetic Resonance ◽  
Acyl Chain ◽  
Orientational Order ◽  
Membrane Lipid ◽  
Fatty Acyl ◽  
Fatty Acyl Chain ◽  
Lipid Phase ◽  
Lipid Phase Transition

The orientational order parameters of monofluoropalmitic acids biosynthetically incorporated into membranes of Acholeplasma laidlawii B in the presence of a large excess of a variety of structurally diverse fatty acids have been determined via 19F nuclear magnetic resonance (19F NMR) spectroscopy. It is demonstrated that these monofluoropalmitic acids are relatively nonperturbing membrane probes based upon physical (differential scanning calorimetry), biochemical (membrane lipid analysis), and biological (growth studies) criteria. 19F NMR is shown to convey the same qualitative and quantitative picture of membrane lipid order provided by 2H-NMR techniques and to be sensitive to the structural characteristics of the membrane fatty acyl chains, as well as to the lipid phase transition. Representatives of each naturally occurring class of fatty acyl chain structures, including straight-chain saturated, methyl-branched, monounsaturated, and alicyclic-ring-substituted fatty acids, were studied and the 19F-NMR order parameters were correlated with the lipid phase transitions (determined calorimetrically). The lipid phase transition was the prime determinant of overall orientational order regardless of fatty acid structure. Effects upon orientational order attributable to specific structural substituents were discernible, but were secondary to the effects of the lipid phase transition. In the gel state, relative overall order was directly proportional to the temperature of the particular lipid phase transition. Not only the overall order, but also the order profile across the membrane was sensitive to the presence of particular structural substituents. In particular, in the gel state specific fatty acyl structures demonstrated a characteristic disordering effect in the membrane order profile. These various observations can be merged to provide a unified picture of the manner in which fatty acyl chain chemistry modulates the physical state of membrane lipids.

Structures and properties of mixtures of branched chain compounds and lecithin: phytol, α-tocopherol (vitamin E), and phytanic acid

1979 ◽  
Vol 57 (4) ◽  
pp. 458-465 ◽  
Author(s):  
Robert J. Cushley ◽  
Bruce J. Forrest ◽  
Anne Gillis ◽  
Jenifer Tribe
Keyword(s):  
Differential Scanning Calorimetry ◽  
Vitamin E ◽  
Phytanic Acid ◽  
Liquid Crystalline ◽  
Egg Yolk ◽  
Scanning Calorimetry ◽  
Chain Molecules ◽  
Structures And Properties ◽  
Branched Chain ◽  
Crystalline Phase Transition

Phospholipid bilayers containing branched chain molecules, phytol (1), vitamin E (2), and phytanic acid (3), have been investigated by 31P nmr, esr, and differential scanning calorimetry (dsc).A 31P lanthanide induced shift study indicated varying permeabilities to Pr3+ in the order phytanic acid > vitamin E > phytol > egg yolk lecithin alone; the half-lives (in days) were 0.002, 0.14, 0.83, and 6.5, respectively. The activation energy for Pr3+ permeation through the egg yolk lecithin–phytol membrane was found to be 84.9 ± 0.8 kJ.The following esr order parameters, S3, were obtained using the extrinsic spin label, 5-doxylpalmitic acid, in oriented mixed multibilayers: S3 (1) = 0.29, S3 (2) = 0.50, and S3 (3) = 0.02.Differential scanning calorimetry revealed a lowering of the gel–liquid crystalline phase transition temperature, Tc, as the concentration of incorporated isoprenoid compound increases, with eventual disappearance of the endotherm. Specific entropy, s, calculated for dipalmitoyl lecithin +25 mol% 3 is 126 J kg−1 K−1 compared to s = 114.2 J kg−1 K−1 for 1and s = 85 J kg−1 K−1 for 2.

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