Time-resolved electron spin resonance studies of spin-labelled lipids in membranes

Bartucci, Rosa; Erilov, Denis A.; Guzzi, Rita; Sportelli, Luigi; Dzuba, Sergei A.; Marsh, Derek

doi:10.1016/j.chemphyslip.2006.02.009

Cited by 56 publications

(61 citation statements)

References 33 publications

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“…Because the rotational rate of these probes reflects the orientational dynamics of the surrounding phospholipids, we propose that cholesterol incorporation induces an increase in orientational dynamics at the deep region of the phospholipid acyl chains and a corresponding orientational dynamics decrease at the region close to the lipid polar head groups. Our conclusion is in agreement with Bartucci and co-workers [32], who proposed that the methyl terminal of the chain moves more freely in the presence of cholesterol. Cholesterol incorporation affects the structure: the order increases at the deep acyl chain level (except in DPPC LUVs in the gel state where no change is observed), whereas the order decreases at the glycerol backbone level (although other effects were also observed).…”

Section: Discussionsupporting

confidence: 94%

Differential Dynamic and Structural Behavior of Lipid-Cholesterol Domains in Model Membranes

et al. 2012

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Changes in the cholesterol (Chol) content of biological membranes are known to alter the physicochemical properties of the lipid lamella and consequently the function of membrane-associated enzymes. To characterize these changes, we used steady-state and time resolved fluorescence spectroscopy and two photon-excitation microscopy techniques. The membrane systems were chosen according to the techniques that were used: large unilamellar vesicles (LUVs) for cuvette and giant unilamellar vesicles (GUVs) for microscopy measurements; they were prepared from dipalmitoyl phosphatidylcholine (DPPC) and dioctadecyl phosphatidylcholine (DOPC) in mixtures that are well known to form lipid domains. Two fluorescent probes, which insert into different regions of the bilayer, were selected: 1,6-diphenyl-1,3,5-hexatriene (DPH) was located at the deep hydrophobic core of the acyl chain regions and 2-dimethylamino-6-lauroylnaphthalene (Laurdan) at the hydrophilic-hydrophobic membrane interface. Our spectroscopy results show that (i) the changes induced by cholesterol in the deep hydrophobic phospholipid acyl chain domain are different from the ones observed in the superficial region of the hydrophilic-hydrophobic interface, and these changes depend on the state of the lamella and (ii) the incorporation of cholesterol into the lamella induces an increase in the orientation dynamics in the deep region of the phospholipid acyl chains with a corresponding decrease in the orientation at the region close to the polar lipid headgroups. The microscopy data from DOPC/DPPC/Chol GUVs using Laurdan generalized polarization (Laurdan GP) suggest that a high cholesterol content in the bilayer weakens the stability of the water hydrogen bond network and hence the stability of the liquid-ordered phase (Lo).

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Section: Discussionsupporting

confidence: 94%

Differential Dynamic and Structural Behavior of Lipid-Cholesterol Domains in Model Membranes

et al. 2012

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“…It has previously been assumed that polarity profile reported by spin labels for fluid and frozen membranes containing cholesterol in general follows the membrane water penetration profile 48,40,49 . However, the exact features of the ESR spectrum may be defined by interplay of this water penetration and the flexibility of spin-labeled lipid chains, see below.…”

Section: Resultsmentioning

confidence: 99%

Conformational Distributions and Hydrogen Bonding in Gel and Frozen Lipid Bilayers: A High Frequency Spin-Label ESR Study

2012

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The ESR parameters of PC spin labels in frozen membranes do not simply represent the membrane polarity or water penetration profile. Instead, they show a distribution between hydrogen-bonded (HB) and non-hydrogen bonded (non-HB) states, which is affected by a number of factors in the membrane composition. Similar to the exclusion of solutes from crystallizing solvents, the pure bulk gel phase excludes nitroxides, forcing acyl chains to take bent conformations. In these conformations the nitroxide is hydrogen-bonded. Furthermore, upon gradual cooling in the supercooled gel PC labels undergo slow lateral aggregation resulting in a broad background signal. However, if the sample is instantly frozen, this background is replaced by the HB component. In membranes with cholesterol the observed HB/ non-HB ratio can best be described by a partition-like equilibrium between nitroxides located in defects of lipid structure within the hydrophobic core and those close to the membrane surface.

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“…where a N o;1 and a N o;2 are the limiting values of a N o at the polar headgroup and terminal methyl ends of the lipid chain and k is an exponential decay length (see also [43,44]). The correlations established here between the polarity dependence of the TOAC or MTSSL spin labels and that of the DOX-YL fatty acid or phospholipid spin labels allow one to develop calibrations for the positional dependence of the [45,46], and by g xx -inhomogeneities arising from hydrogen bonding that are observed in high-field EPR [10].…”

Section: Calibration Of Penetration Depth For Toac and Mtssl In Membrmentioning

confidence: 99%

Polarity dependence of EPR parameters for TOAC and MTSSL spin labels: Correlation with DOXYL spin labels for membrane studies

Marsh

Toniolo

2008

Journal of Magnetic Resonance

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TOAC (2,2,6,6-tetramethylpiperidine-1-oxyl-4-amino-4-carboxylic acid) is a nitroxyl amino acid that can be incorporated in the backbone of peptides. DOXYL (4,4-dimethyl-oxazolidine-1-oxyl) is a nitroxyl ring that can be attached rigidly at specific C-atom positions in the acyl chains of phospholipids. Spin-labelled phosphatidylcholines of the DOXYL type have been used previously to establish the transmembrane polarity profile in biological lipid bilayers [D. Marsh, Polarity and permeation profiles in lipid membranes, Proc. Natl. Acad. Sci. USA 87 (2001) 7777-7782]. Here, we determine the polarity dependence of the isotropic (14)N-hyperfine couplings, a(o)(N), and g-values, g(o), in a wide range of protic and aprotic media, for a TOAC-containing dipeptide (Fmoc-TOAC-Aib-OMe) and for a DOXYL-containing fatty acid (12-DOXYL-stearic acid). The correlation between datasets for TOAC and DOXYL nitroxides in the various solvents is used to establish the polarity profile for isotropic hyperfine couplings of TOAC in a transmembrane peptide. This calibration can be used to determine the location of TOAC at selected residue positions in a transmembrane or surface-active peptide. A similar calibration procedure is also applied to a(o)(N) and g(o) for the pyrroline methanethiosulphonate nitroxide (MTSSL) that is used in site-directed spin-labelling studies of membrane proteins.

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Time-resolved electron spin resonance studies of spin-labelled lipids in membranes

Cited by 56 publications

References 33 publications

Differential Dynamic and Structural Behavior of Lipid-Cholesterol Domains in Model Membranes

Differential Dynamic and Structural Behavior of Lipid-Cholesterol Domains in Model Membranes

Conformational Distributions and Hydrogen Bonding in Gel and Frozen Lipid Bilayers: A High Frequency Spin-Label ESR Study

Polarity dependence of EPR parameters for TOAC and MTSSL spin labels: Correlation with DOXYL spin labels for membrane studies

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