Etude de la Rameb par resonance paramagnétique électronique et diffusion de neutrons aux petits angles

Conference (2007, November)

Electron spin resonance, a powerful method to investigate cell membrane viscosity change induced by drug.

Conference (2007, September)

Does propofol alter membrane fluidity at clinically relevant concentrations? An ESR spin label study

in Biophysical Chemistry (2007), 129(1), 82-91

General anesthetics have been shown to perturb the membrane properties of excitable tissues. Due to their lipid solubility, anesthetics dissolve in every membrane, penetrate into organelles and interact ... [more ▼]

General anesthetics have been shown to perturb the membrane properties of excitable tissues. Due to their lipid solubility, anesthetics dissolve in every membrane, penetrate into organelles and interact with numerous cellular structures in multiple ways. Several studies indicate that anesthetics alter membrane fluidity and decrease the phase-transition temperature. However, the required concentrations to induce such effects on the properties of membrane lipids are by far higher than clinically relevant concentrations. In the present study, the fluidizing effect of the anesthetic agent propofol (2,6-diisopropyl phenol: PPF), a general anesthetic extensively used in clinical practice, has been investigated on liposome dimyristoyi-L-alpha phosphatidylcholine (DMPC) and cell (erythrocyte, Neuro-2a) membranes using electron spin resonance spectroscopy (ESR) of nitroxide labeled fatty acid probes (5-, 16-doxyl stearic acid). A clear effect of PPF at concentrations higher than the clinically relevant ones was quantified both in liposome and cell membranes, while no evident fluidity effect was measured at the clinical PPF doses. However, absorption spectroscopy of merocyanine 540 (MC540) clearly indicates a PPF fluidizing capacity in liposome membrane even at these clinical concentrations. PPF may locally influence the structure and dynamics of membrane domains, through the formation of small-scale lipid domains, which would explain the lack of ESR information at low PPF concentrations. (c) 2007 Elsevier B.V. All rights reserved. [less ▲]

. Electron spin resonance, a powerful method to investigate membrane micro-viscosity

Poster (2007)

Investigation of SDS, DTAB and CTAB micelle microviscosities by electron spin resonance

in Colloids and Surfaces A : Physicochemical and Engineering Aspects (2006), 290(1-3), 206-212

Electron spin resonance spectroscopy (ESR) of the nitroxide labelled fatty acid probes (5-, 16-doxyl stearic acid) was used to monitor the micelle microviscosity of three surfactants at various ... [more ▼]

Electron spin resonance spectroscopy (ESR) of the nitroxide labelled fatty acid probes (5-, 16-doxyl stearic acid) was used to monitor the micelle microviscosity of three surfactants at various concentrations in aqueous solution: sodium dodecyl sulphate (SDS), dodecyltrimethylammonium bromide (DTAB) and cetyltrimethylammonium bromide (CTAB). At low surfactant concentration, there is no micelle, the ESR probe is dissolved in water/surfactant homogeneous phase and gives his microviscosity. At higher surfactant concentration, an abrupt increase in microviscosity indicates the apparition of micelles and, the solubilization of the probes in micelles. The microviscosity of the three surfactants, in a large surfactant range, was obtained as well as the critical micelle concentration (CMC). The microviscosity increased slightly with the increase in surfactant concentration. Phosphate buffer lowered the CMC value and generally increased the microviscosity. (c) 2006 Elsevier B.V. All rights reserved. [less ▲]

ESR investigation of micelle microviscosity of sodium taurocholate and taurodeoxycholates in aquouse media.

Poster (2006, May)

Quantification of lipid bilayer effective microviscosity and fluidity effect induced by propofol

in Biophysical Chemistry (2005), 114(1), 53-61

Electron spin resonance (ESR) spectroscopy with nitroxide spin probes was used as a method to probe the liposome microenvironments. The effective microviscosities have been determined from the calibration ... [more ▼]

Electron spin resonance (ESR) spectroscopy with nitroxide spin probes was used as a method to probe the liposome microenvironments. The effective microviscosities have been determined from the calibration of the ESR spectra of the probes in solvent mixtures of known viscosities. In the first time, by measuring ESR order parameter (S ) and correlation time (s c) of stearic spin probes, we have been able to quantify the value of effective microviscosity at different depths inside the liposome membrane. At room temperature, local microviscosities measured in dimyristoyl-l-a phosphatidylcholine (DMPC) liposome membrane at the different depths of 7.8, 16.95, and 27.7 2 were 222.53, 64.09, and 62.56 cP, respectively. In the gel state (10 °C), those microviscosity values increased to 472.56, 370.61, and 243.37 cP. In a second time, we have applied this technique to determine the modifications in membrane microviscosity induced by 2,6-diisopropyl phenol (propofol; PPF), an anaesthetic agent extensively used in clinical practice. Propofol is characterized by a unique phenolic structure, absent in the other conventional anaesthetics. Indeed, given its lipophilic property, propofol is presumed to penetrate into and interact with membrane lipids and hence to induce changes in membrane fluidity. Incorporation of propofol into dimyristoyl-L-alpha-phosphatidylcholine liposomes above the phase-transition temperature (23.9 °C) did not change microviscosity. At 10 °C, an increase of propofol concentration from 0 to 1.0 10 [less ▲]

Determination of the critical micelle concentration using ESR spin label method.

Poster (2005)

Study in human colon cancer cells HCT-116 of PPME photodynamic effect solubilized in DMPC liposomes

Conference (2005)

Improvement by solubilization in DMPC liposomes of PPME photodynamic effect - A study in human colon cancer cells HCT-116

Conference (2005)