Michel Picquart

Vibrational Spectroscopic Study of Glutathione Complexation in Aqueous Solutions

A spectroscopic study of glutathione (GSH) and glutathione disulfide (GSSG) has been performed using Fourier-transformed infrared absorption and Raman scattering in order to pinpoint the sites of complexation of these two species with water and particularly with H2O2. Molecules of GSH and GSSG were studied in KBr pellets, and in aqueous solutions of H2O, D2O, and H2O with H2O2 (1 mol L(-1)) to characterize the specific influence of the solvent molecules. A time-resolved Raman study was performed for GSH/H2O2, in aqueous solution at 1:1 molar ratio in order to observe the formation of GSSG and to discuss the mechanism of this redox reaction.

Structural study of lithium titanium mixed oxides prepared by sol-gel process

A structural study, using TGA-DSC analysis, X-ray diffraction, Raman scattering and FT Infrared absorption, is performed on mixed titanium lithium oxide with 20% of lithium prepared by sol-gel process. The structure is investigated as a function of the annealing temperature. At low temperatures the sample is in the anatase phase and transforms to the rutile phase near 500°C. The crystallite size of rutile TiO2 increases from 40 to 100 nm as the temperature increases. However the size increase presents some discontinuity at temperature around 600°C. At thermal treatment temperatures from 500°C to 850°C the presence of LiTi2O4 in the sample is clearly observed. Finally at 1000°C the sample is composed by a mixture of rutile TiO2 and Li2Ti3O7.

Spectroscopic study of N-acetylcysteine and N-acetylcystine/hydrogen peroxide complexation

Abstract A spectroscopic study of N-acetylcysteine (RSH) and N-acetylcystine (RSSR) has been performed using infrared absorption and Raman scattering in order to pinpoint the sites of complexation of these two species with H 2 O 2 . Molecules of RSH and RSSR were studied in KBr pellets, and in aqueous solutions of H 2 O, D 2 O and H 2 O with H 2 O 2 (1 mol l −1 ) to characterize the specific influence of the solvent molecules. A time-resolved Raman study was performed for RSH-H 2 O 2 in aqueous solution at 1:1 molar ratio in order to observe the formation of RSSR and to discuss the mechanism of this redox reaction.

The Mexican Cactus as a New Environmentally Benign Material for the Removal of Contaminants in Drinking Water

The use of natural environmentally benign agents in the treatment of drinking water is rapidly gaining interest due to their inherently renewable character and low toxicity. We show that the common Mexican cactus produces a gum-like substance, cactus mucilage, which shows flocculating abilities superior to the commonly used aluminum sulfate with respect to settling time and shows promise as a socially viable alternative for low-income communities. Cactus mucilage is a neutral mixture of approximately 55 high-molecular weight sugar residues composed basically of arabinose, galactose, rhamnose, xylose, and galacturonic acid. We show how this natural product was characterized for its use as a flocculating agent. Our results show the mucilage efficiency for reducing arsenic and particulates from drinking water as determined by light scattering, Atomic Absorption and Hydride Generation-Atomic Fluorescence Spectroscopy. Flocculation studies proved the mucilage to be a much faster flocculating agent when compared to Al2(SO4)3 with the efficiency increasing with mucilage concentration. Jar tests revealed that lower concentrations of mucilage provided the optimal effectiveness for supernatant clarity, an important factor in determining the potability of water. Initial filter results with the mucilage embedded in a silica matrix prove the feasibility of applying this technology as a method for heavy metal removal. This project provides fundamental, quantitative insights into the necessary and minimum requirements for natural flocculating agents that are innovative, environmentally benign, and cost-effective.

Elastic vibrations of spheroidal nanometric particles

Particles of nanometric size show low-frequency vibrational modes that can be observed by Raman spectroscopy. These modes involve the collective motion of large numbers of atoms and it is possible to calculate their frequency using elasticity theory. In this work a simple model for oblate-shaped nanoparticles is developed and compared with experimental results obtained in bismuth nanoparticles. It is found that the agreement between theory and experiment is improved in comparison to the spherical model usually employed. However for the smallest particles the elastic model is no longer valid and lattice discreteness has to be considered.

Development of a Nanostructured Platform for Identifying HER2-Heterogeneity of Breast Cancer Cells by Surface-Enhanced Raman Scattering

Biosensor technology has great potential for the detection of cancer through tumor-associated molecular biomarkers. In this work, we describe the immobilization of the recombinant humanized anti-HER2 monoclonal antibody (trastuzumab) on a silver nanostructured plate made by pulsed laser deposition (PLD), over a thin film of Au(111). Immobilization was performed via 4-mercapto benzoic acid self-assembled monolayers (4-MBA SAMs) that were activated with coupling reagents. A combination of immunofluorescence images and z-stack analysis by confocal laser scanning microscopy (CLSM) allowed us to detect HER2 presence and distribution in the cell membranes. Four different HER2-expressing breast cancer cell lines (SKBR3 +++, MCF-7 +/−, T47D +/−, MDA-MB-231 −) were incubated during 24 h on functionalized silver nanostructured plates (FSNP) and also on Au(111) thin films. The cells were fixed by means of an ethanol dehydration train, then characterized by atomic force microscopy (AFM) and surface-enhanced Raman scattering (SERS). SERS results showed the same tendency as CLSM findings (SKBR3 > MCF-7 > T47D > MDA-MB-231), especially when the Raman peak associated with phenylalanine amino acid (1002 cm−1) was monitored. Given the high selectivity and high sensitivity of SERS with a functionalized silver nanostructured plate (FSNP), we propose this method for identifying the presence of HER2 and consequently, of breast cancer cells.

Production of Di-isopropyl ether (DIPE) over 12-Molybdophosphoric Acid Supported on ZrO 2 . An Alternative Octane Enhancer for Lead-free Petrol

Solid acid catalysts of 12-Molybdophosphoric acid (MoP) supported on hydrous zirconia have been synthesized using impregnation method. Structural transformations due to thermal effects have been studied by different techniques including X-Ray diffraction, thermogravimetric analysis (TGA), infrared absorption (DRIFT), Raman spectroscopy and 31 P MAS NMR. These techniques showed that the heteropolyacid present undegraded Keggin structure. The transformation of heteropoly anion of pure HPMo to MoO 3 begins at a temperature lower than that for its ZrO 2 -supported counterpart. The activity of ZrO 2 -supported (MoP-Z) catalysts in the 2-propanol decomposition presents a high selectivity to the formation of DIPE and propene, this selectivity is related with acid sites determined by thermodesorption (TPD) of NH 3 .

Vibrational Spectroscopy of Biological Membrane Models

The purpose of this paper is to outline in the field of biological science the kinds of problems to which vibrational spectroscopy (infrared absorption and Raman scattering) can provide solutions. Emphasis is given here to the use of vibrational spectra in the study of molecular structures of biomembranes and interactions of biologically important materials. The main aspect will concern the changes observed in the lipid spectrum when host molecules are interacting: vitamin E, antibiotic (sodium lasalocid) and in the water molecules.

Elastic Vibrational of Nanoparticles

Low frequency acoustic vibrations have been observed by Raman spectroscopy in a wide variety of nano-metric objects in various conditions. A simple elastic model has been used in many cases to give account for the observed results. In this work results obtained on bismuth nanocrystals embedded in an amorphous matrix, free standing zirconia powders and a monoclonal antibody molecule are analyzed and compared.