Temperature-induced changes in lecithin model membranes detected by novel covalent spin-labelled phospholipids

1977 ◽  
Vol 55 (2) ◽  
pp. 173-185 ◽  
Author(s):  
L. Stuhne-Sekalec ◽  
N. Z. Stanacev
Keyword(s):  
Transition Temperature ◽  
Fatty Acyl ◽  
Model Membranes ◽  
Head Group ◽  
Polar Head Group ◽  
Polar Group ◽  
Conformational Isomers ◽  
Hydrocarbon Chains ◽  
Acyl Chains ◽  
Induced Changes

Several spin-labelled phospholipids carrying covalently bound 5-doxylstearic acid (2-(3-carboxydecyl)-2-hexyl-4,4-dimethyl-3-oxazolidinoxyl) were intercalated in liposomes of saturated and unsaturated lecithins. Temperature-induced changes of these liposomes, detected by the spin-labelled phospholipids, were found to be in agreement with the previously described transitions of hydrocarbon chains of host lecithins detected by different probes and different techniques, establishing that spin-labelled phosopholipids are sensitive probes for the detection of temperature-induced changes in lecithin model membranes. In addition to the detection of already-known transitions in lecithin liposomes, the coexistence of two distinctly different environments was observed above the characteristic transition temperature. This phenomenon was tentatively attributed to the influence of the lecithin polar group on the fluidity of fatty acyl chains near the polar group. Combined with other results from the literature, the coexistence of two environments could be associated with the coexistence of two conformational isomers of lecithin, differing in the orientation of the polar head group with respect to the plane of bilayer. These findings have been discussed in view of the present state of knowledge regarding temperature-induced changes in model membranes.

scholarly journals Lipid conformation in model membranes and biological membranes

1980 ◽  
Vol 13 (1) ◽  
pp. 19-61 ◽  
Author(s):  
Joachim Seelig ◽  
Anna Seelig
Keyword(s):  
Liquid Crystalline ◽  
Double Helix ◽  
Liquid Paraffin ◽  
Biological Membranes ◽  
Fatty Acyl ◽  
Head Group ◽  
Exact Nature ◽  
Polar Head Group ◽  
Acyl Chains ◽  
Lipid Conformation

Protein molecules in solution or in protein crystals are characterized by rather well-defined structures in which α-helical regions, β-pleated sheets, etc., are the key features. Likewise, the double helix of nucleic acids has almost become the trademark of molecular biology as such. By contrast, the structural analysis of lipids has progressed at a relatively slow pace. The early X-ray diffraction studies by V. Luzzati and others firmly established the fact that the lipids in biological membranes are predominantly organized in bilayer structures (Luzzati, 1968). V. Luzzati was also the first to emphasize the liquid-like conformation of the hydrocarbon chains, similar to that of a liquid paraffin, yet with the average orientation of the chains perpendicular to the lipid–water interface. This liquid–crystalline bilayer is generally observed in lipid–water systems at sufficiently high temperature and water content, as well as in intact biological membranes under physiological conditions (Luzzati & Husson, 1962; Luzzati, 1968; Tardieu, Luzzati & Reman, 1973; Engelman, 1971; Shipley, 1973). In combination with thermodynamic and other spectroscopic observations these investigations culminated in the formulation of the fluid mosaic model of biological membranes (cf. Singer, 1971). However, within the limits of this model the exact nature of lipid conformation and dynamics was immaterial, the lipids were simply pictured as circles with two squiggly lines representing the polar head group and the fatty acyl chains, respectively. No attempt was made to incorporate the well-established chemical structure into this picture. Similarly, membrane proteins were visualized as smooth rotational ellipsoids disregarding the possibility that protruding amino acid side-chains and irregularities of the backbone folding may create a rather rugged protein surface.

scholarly journals Leaf Lipid Alterations in Response to Heat Stress of Arabidopsis thaliana

Plants ◽  
2020 ◽  
Vol 9 (7) ◽  
pp. 845 ◽  
Author(s):  
Sunitha Shiva ◽  
Thilani Samarakoon ◽  
Kaleb A. Lowe ◽  
Charles Roach ◽  
Hieu Sy Vu ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Heat Stress ◽  
Elevated Temperatures ◽  
Membrane Lipids ◽  
Fatty Acyl ◽  
Head Group ◽  
Wild Type ◽  
Lipid Levels ◽  
Acyl Chains ◽  
Severe Heat Stress

In response to elevated temperatures, plants alter the activities of enzymes that affect lipid composition. While it has long been known that plant leaf membrane lipids become less unsaturated in response to heat, other changes, including polygalactosylation of galactolipids, head group acylation of galactolipids, increases in phosphatidic acid and triacylglycerols, and formation of sterol glucosides and acyl sterol glucosides, have been observed more recently. In this work, by measuring lipid levels with mass spectrometry, we confirm the previously observed changes in Arabidopsis thaliana leaf lipids under three heat stress regimens. Additionally, in response to heat, increased oxidation of the fatty acyl chains of leaf galactolipids, sulfoquinovosyldiacylglycerols, and phosphatidylglycerols, and incorporation of oxidized acyl chains into acylated monogalactosyldiacylglycerols are shown. We also observed increased levels of digalactosylmonoacylglycerols and monogalactosylmonoacylglycerols. The hypothesis that a defect in sterol glycosylation would adversely affect regrowth of plants after a severe heat stress regimen was tested, but differences between wild-type and sterol glycosylation-defective plants were not detected.

scholarly journals Head-Group Acylation of Chloroplast Membrane Lipids

Molecules ◽  
2021 ◽  
Vol 26 (5) ◽  
pp. 1273
Author(s):  
Yu Song ◽  
Zolian S. Zoong Lwe ◽  
Pallikonda Arachchige Dona Bashanee Vinusha Wickramasinghe ◽  
Ruth Welti
Keyword(s):  
Mass Spectrometry ◽  
Arabidopsis Thaliana ◽  
Abiotic Stresses ◽  
Membrane Lipids ◽  
Fatty Acyl ◽  
Head Group ◽  
Biological Functions ◽  
Biotic And Abiotic Stresses ◽  
Acyl Chains ◽  
The 1960S

Head group-acylated chloroplast lipids were discovered in the 1960s, but interest was renewed about 15 years ago with the discovery of Arabidopsides E and G, acylated monogalactosyldiacylglycerols with oxidized fatty acyl chains originally identified in Arabidopsis thaliana. Since then, plant biologists have applied the power of mass spectrometry to identify additional oxidized and non-oxidized chloroplast lipids and quantify their levels in response to biotic and abiotic stresses. The enzyme responsible for the head-group acylation of chloroplast lipids was identified as a cytosolic protein closely associated with the chloroplast outer membrane and christened acylated galactolipid-associated phospholipase 1 (AGAP1). Despite many advances, critical questions remain about the biological functions of AGAP1 and its head group-acylated products.

Intestinal microsomes: polyunsaturated fatty acid metabolism and regulation of enterocyte transport properties

1990 ◽  
Vol 68 (5) ◽  
pp. 636-641 ◽  
Author(s):  
M. L. Garg ◽  
M. Keelan ◽  
A. B. R. Thomson ◽  
M. T. Clandinin
Keyword(s):  
Acyl Chain ◽  
Lipid Synthesis ◽  
Fatty Acyl ◽  
Fine Tuning ◽  
Membrane Properties ◽  
Head Group ◽  
Fatty Acyl Chain ◽  
Polar Head Group ◽  
Intestinal Microsomes ◽  
Main Determinants

Recent evidence has suggested that transport of nutrients from the lumen to the interior of the gastrointestinal epithelium and exit of nutrients from the enterocyte to the circulation is governed by physicochemical properties of brush border and basolateral membranes, respectively. The main determinants of membrane properties are phospholipid, cholesterol, and fatty acyl chain composition (chain length and degree of unsaturation). Lipid synthesis occurs in enterocyte microsomes and the fine tuning of lipid composition is done at other subcellular sites by deacylation–reacylation or by changing the polar head group (e.g., by phosphatidylethanolamine methyltransferase). The present paper will focus on the mechanisms by which enterocyte membranes adapt functional properties in response to external stimuli. It is proposed that under the influence of internal or external stress, the enzymes of lipid metabolism in microsomes are modulated. These changes in lipid synthesis are reflected in other subcellular membranes, changing their physicochemical status and thus transport phenomena. One of the initial events appears to be alteration in desaturase enzyme activity. Our results suggest that desaturase activity and the fatty acyl profiles of the intestinal mucosal phospholipid rapidly respond to physiological conditions such as fasting and dietary fat treatment.Key words: polyunsaturated fatty acids, desaturases, enterocyte, intestinal microsomes, adaptation.

Modifications of lipid structure and their influence on mesomorphism in model membranes: the influence of hydrocarbon chains

1986 ◽  
Vol 64 (1) ◽  
pp. 44-49 ◽  
Author(s):  
K. M. W. Keough
Keyword(s):  
Liquid Crystalline ◽  
Analytical Data ◽  
Model Membranes ◽  
Positional Isomers ◽  
Double Bonds ◽  
Enthalpy Changes ◽  
Hydrocarbon Chains ◽  
Acyl Chains ◽  
Crystalline Phase Transition ◽  
Subsequent Introduction

The influence of hydrocarbon chains on the temperature (TG–LC) of the gel to liquid-crystalline phase transition of model membranes has been investigated over an extensive variety of phosphatidylcholines (PC). The TG–LC is dependent upon the length of the hydrocarbon chains, on whether or not the chains are saturated or have been modified in some way, and on the position of any modification along the chain. For PC having two different acyl chains (heteroacid PC) in the sn-1 and sn-2 positions, the TG–LC is dependent on the chain position and on the inequivalence of chain penetration into the bilayer. Positional isomers of PC have different TG–LC. The first two double bonds introduced in each chain of a PC cause a much greater reduction in TG–LC and in the enthalpy change of the transition than does the subsequent introduction of additional double bonds. Dipolyunsaturated PC have uncooperative (broad) transitions that occur at low temperatures and have small enthalpy changes. While each PC has unique transitional characteristics, there are a number of patterns in the TG–LC which emerge on consideration of all the available data. One such pattern may be useful in predicting TG–LC from analytical data on the composition and positions of acyl chains of various lipids.

scholarly journals Interaction of plant lipids with 14 kDa phospholipase A2 enzymes

1996 ◽  
Vol 320 (1) ◽  
pp. 93-99 ◽  
Author(s):  
Bannikuppe S VISHWANATH ◽  
Waldemar EICHENBERGER ◽  
Felix J FREY ◽  
Brigitte M. FREY
Keyword(s):  
Enzyme Activity ◽  
Phospholipase A2 ◽  
Fatty Acyl ◽  
Polar Head Group ◽  
Dependent Manner ◽  
Pla2 Activity ◽  
Group I ◽  
Plant Lipids ◽  
Acyl Chains ◽  
Dose Dependent

Several structurally related plant lipids were isolated and their effect was assessed on the enzyme activity of group I (pancreatic and Naja mocambique venom) and group II (Crotalus atrox venom) phospholipase A2 (PLA2) enzymes, with labelled Escherichia coli as an enzyme substrate. The neutral monogalactosyldiacylglycerol (MGDG) and negatively charged diacylglyceryl α-D-glucuronide (DGGA) did not influence the enzyme activity of either group. Digalactosyldiacylglycerol (DGDG), another uncharged glycolipid, inhibited PLA2 activity in a dose-dependent manner to 60–70% of the control. Sulphoquinovosyldiacylglycerol (SQDG), which is also anionic, activated both groups of PLA2 enzyme. A similar activation was observed with the zwitterionic diacylglyceryl-O-(N,N,N-trimethylhomoserine) (DGTS) and diacylglyceryl-O-(hydroxymethyl)(N,N,N-trimethyl)-β-alanine (DGTA). DGDG, SQDG and DGTS are dispersed homogeneously with low critical micelle concentrations (CMCs). The hydrodynamic radius of neutral DGDG is an order of magnitude larger than the charged lipids SQDG and DGTS. The inhibition of pig pancreatic PLA2 by DGDG was dependent on substrate concentration. The intrinsic fluorescence spectra of the enzyme was not changed in the presence of native or hydrogenated DGDG. Thus the inhibition is most probably due to a non-specific interaction of plant lipids with the substrate. Different lengths and saturations of the fatty acyl chains of DGDG did not alter the inhibition of PLA2, whereas deacylation abrogated the inhibitory effect. Both SQDG and DGTS activated pig pancreatic PLA2 in a dose-dependent manner. Saturation of the double bonds of these lipids decreased the activating effect. The fluorescence of pig pancreatic PLA2 incubated with SQDG and DGTS was enhanced by 2-fold and 3-fold respectively, suggesting the formation of a complex between enzyme and lipids. In conclusion, the effect of different plant lipids on PLA2 activity depends on different structural elements of the polar head group and their charge as well as the degree of unsaturation of the fatty acyl chains.

scholarly journals Profile of Phosphatidylserine Modifications under Nitroxidative Stress Conditions Using a Liquid Chromatography-Mass Spectrometry Based Approach

Molecules ◽  
2018 ◽  
Vol 24 (1) ◽  
pp. 107 ◽  
Author(s):  
Bruna Neves ◽  
Pedro Domingues ◽  
Maria Oliveira ◽  
Maria Domingues ◽  
Tânia Melo
Keyword(s):  
Mass Spectrometry ◽  
Liquid Chromatography ◽  
Acyl Chain ◽  
Fatty Acyl ◽  
Head Group ◽  
Fatty Acyl Chain ◽  
Polar Head Group ◽  
Derivatives Of

Nitrated lipids have been detected in vitro and in vivo, usually associated with a protective effect. While nitrated fatty acids have been widely studied, few studies reported the nitration and nitroxidation of the phospholipid classes phosphatidylcholine, and phosphatidylethanolamine. However, no information regarding nitrated and nitroxidized phosphatidylserine can be found in the literature. This work aims to identify and characterize the nitrated and nitroxidized derivatives of 1-palmitoyl-2-oleoyl-sn-3-glycero-phosphoserine (POPS), obtained after incubation with nitronium tetrafluoroborate, by liquid chromatography (LC) coupled to mass spectrometry (MS) and tandem MS (MS/MS). Several nitrated and nitroxidized products were identified, namely, nitro, nitroso, nitronitroso, and dinitro derivatives, as well as some nitroxidized species such as nitrosohydroxy, nitrohydroxy, and nitrohydroperoxy. The fragmentation pathways identified were structure-dependent and included the loss of HNO and HNO2 for nitroso and nitro derivatives, respectively. Combined losses of PS polar head group plus HNO or HNO2 and carboxylate anions of modified fatty acyl chain were also observed. The nitrated POPS also showed antiradical potential, demonstrated by the ability to scavenge the ABTS●+ and DPPH● radicals. Overall, this in vitro model of nitration based on LC-MS/MS provided additional insights into the nitrated and nitroxidized derivatives of PS and their fragmentation fingerprinting. This information is a valuable tool for targeted analysis of these modified PS in complex biological samples, to further explore the new clues on the antioxidant potential of nitrated POPS.

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