Columnar DNA Superlattices in Lamellaro-Ethylphosphatidylcholine Lipoplexes:  Mechanism of the Gel-Liquid Crystalline Lipid Phase Transition

Nano Letters ◽  
2004 ◽  
Vol 4 (8) ◽  
pp. 1475-1479 ◽  
Author(s):  
Rumiana Koynova ◽  
Robert C. MacDonald
Keyword(s):  
Phase Transition ◽  
Liquid Crystalline ◽  
Lipid Phase ◽  
Lipid Phase Transition

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.

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.

Effect of Inhalation Anesthetics on Spin-Labeled Cholesterol Containing DPPC Vesicles

1988 ◽  
Vol 43 (3-4) ◽  
pp. 264-268 ◽  
Author(s):  
N. Gulfo ◽  
R. Bartucci ◽  
L. Sportelli
Keyword(s):  
Phase Transition ◽  
Diethyl Ether ◽  
Liquid Crystalline ◽  
Main Phase ◽  
Molar Ratio ◽  
Lipid Phase ◽  
Interfacial Region ◽  
Hydrophobic Core ◽  
Hydrophobic Region ◽  
Inhalation Anesthetics

We have investigated by means of electron spin resonance (ESR) spectroscopy the influence of three inhalation anesthetics, i.e. halothane, chloroform and diethyl ether, on the interfacial and hydrophobic region as well of 38 mol% cholesterol containing DPPC unilamellar vesicles. The study has been carried out in the temperature range 25-45 °C. The variation of the order parameter, S, vs temperature of the lipid phase indicates that with this content of cholesterol the characteristic gel → liquid crystalline main phase transition of DPPC, normally occurring at Tt ~ 41 °C, disappears. When halothane and chloroform are added to the vesicles suspension up to [DPPC]/[anesthetic] molar ratio of 1:1 the main phase transition, as detected with the stearic acid spin label I(12,3), reappears again and it results down shifted at Tt ~ 35 and 39 °C, respectively. In presence of diethyl ether, instead, the main phase transition is not observable also at the highest concentration of anesthetic used. Moreover, halothane and chloroform affect similarly the hydrophobic core of cholesterol-!- DPPC vesicles which, in turn, results to be different from the action exerted by diethyl ether in the same region. The ESR findings are discussed in terms of competitive effects shown by cholesterol and inhalation anesthetics. Moreover, the interfacial region of CHOL + DPPC vesicles results to be the target of anesthetics.

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