Marie-France Renou-Gonnord

Optimization of a capillary electrophoresis–electrospray mass spectrometry method for the quantitation of the 20 natural amino acids in childrens blood

This paper describes useful information on the capillary electrophoresis-electrospray ionization mass spectroscopy (CE-ESIMS) interfacing for the analysis of amino acids (AAs) in standard mixtures and in child plasma blood serum. The developed procedure allows quantitation of the 20 natural AAs, in a single run, without any derivatization. Limits of detection as low as 3-20 micromol/l (5-30 pg injected) per analyte were obtained with an efficiency of about 100,000 plates and a peak area relative standard deviation below 4%.

Spectroscopic characterization of cell membranes and their constituents of the plant-associated soil bacterium Azospirillum brasilense

Abstract Structural and compositional features of bacterial membranes and some of their isolated constituents (cell surface lipopolysaccharide, phospholipids) of the plant-growth-promoting diazotrophic rhizobacterium Azospirillum brasilense (wild-type strain Sp245) were characterized using Fourier transform infrared (FTIR) spectroscopy and some other techniques. FTIR spectra of the cell membranes were shown to comprise the main vibration modes of the relevant lipopolysaccharide and protein components which are believed to be involved in associative plant–bacterium interactions, as well as of phospholipid constituents. The role and functions of metal cations in the structural organization and physicochemical properties of bacterial cell membranes are also discussed considering their accumulation in the membranes from the culture medium.

SPECTROSCOPIC CHARACTERIZATION OF THE UPTAKE OF ESSENTIAL AND XENOBIOTIC METAL CATIONS IN CELLS OF THE SOIL BACTERIUM AZOSPIRILLUM BRASILENSE

The results of flame (FAAS) or graphite furnace atomic absorption spectrometric (GFAAS) analyses are presented and discussed on the accumulation of essential metals (Mg, Ca, Mn and Fe contained in the cultivation medium) and traces of each one of the conventionally xenobiotic elements from the group V, Co, Ni, Cu, Zn or Pb, added to the medium in concentrations (0.2 mM) which do not essentially suppress growth of the bacterial culture, in cells of the plant root‐associated nitrogen‐fixing bacterium Azospirillum brasilense. Along with the essential cations assimilated by the bacterium, Zn and Cu were found to effectively accumulate in the biomass from the environment. The uptake of Co and Ni was significantly less pronounced, whereas Pb and V appeared to be present in cells in much lower concentrations than in the cultivation medium evidently showing no tendency to be assimilated by azospirilla. The effect of the above xenobiotics on the uptake level of the four essential elements provided evidence that they may compete for the formation of biologically active complexes with substances of both intracellular and extracellular localization. The analytical data obtained are compared with Fourier transform infrared (FTIR) spectra of intact vacuum‐dried bacterial cells grown in a standard medium and under the conditions of an increased metal uptake.

Proton affinities of polybenzenoid aromatic hydrocarbons and those with five‐membered rings

Proton affinities of PAHs including one five‐membered ring are calculated by using the AM1 Hamiltonian for the determination of ΔHfo of the neutral and protonated molecules. The calculated PAs are compared to experimental PAs measured by chemical ionization mass spectrometry, using a new method based on competition between charge transfer and proton transfer occurring during the ionization process. A procedure is proposed to validate AM1‐calculated PAs from experimental PAs after rescaling the calculated and measured PA values. The site of protonation is first determined on the criterion of the lowest loss of aromaticity, then on the criterion of the largest HOMO coefficient. For indene, the corrected result is compared to an ab initio calculation at the MP2/6‐31G*//HF/6‐31G* level and to a DFT calculation at the B3LYP/6‐31G* and the B3LYP/6‐311 + G** levels. Five new PAs are thus established and one published experimental PA is revised.

Mass Spectrometric Differentiation of Isomeric Polycyclic Aromatic Hydrocarbons by Chemical Ionization with Diethylether, Tetrahydrofuran and Dimethylcarbonate

Chemical ionization of polycyclic aromatic hydrocarbons (PAHs) with three different reactants, diethylether, dimethylcarbonate and tetrahydrofuran, has been used to differentiate PAH isomers. The mechanisms of formation of the molecular ion, the protonated molecular ion and adducts have been elucidated in order to optimize the analytical diagnosis from the measurement of the relative abundances of ions observed on the PAHs chemical ionization mass spectra. As a practical application, chrysene and triphenylene have been determined quantitatively in a diesel exhaust particles sample.

Atomic Absorption Spectroscopic Investigation of the Mineral Fraction of Pectins Obtained from Pumpkin and Sugar Beet

SummaryData on the mineral composition of plant cell wall carboxypolysaccharides (pectins), obtained from non-traditional vegetable sources (pumpkin and sugar beet) using a biotechnological process of enzymatic extraction (biopectin) and the traditional method of acid treatment, are presented. The results have been obtained by flame (FAAS) or graphite furnace atomic absorption spectroscopy (GFAAS) and include trace analyses of the heavy metal content. It is shown that biopectin has an unusually high total mineral content, due mainly to markedly increased contents of Ca and Mg. The content of a series of alkaline, alkaline earth, and heavy metals in the pectins is compared considering the effect of the extraction method.ZusammenfassungDie Zusammensetzung des mineralischen Anteils von Carboxypolysacchariden (Pektinen), die mittels eines biotechnologischen Prozesses (enzymatische Extraktion; “Biopektin”) bzw. der üblichen Methode (Behandlung mit Säure) aus den Zellwänden von Pflanzen (Kürbis, Zuckerrübe) gewonnen wurden, wird diskutiert. Die Ergebnisse wurden mittels Flammenatomabsorptionsspektroskopie (FAAS) oder im Graphitofen (GFAAS) bestimmt und beinhalten Spurenanalysen des Schwermetallgehalts. Es wird gezeigt, daß Biopektin einen unüblich hohen Mineralanteil aufweist, der hauptsächlich auf den hohen Gehalt an Ca und Mg zurückzuführen ist. Der Gehalt an einer Reihe von Alkali-, Erdalkali- und Schwermetallen wird verglichen und zur Isolationsmethode der Pektine in Beziehung gesetzt.

FTIR spectroscopic study of lipopolysaccharide-containing cell components of the bacteria Azospirillum brasilense

Lipopolysaccharide (LPS) is one of the main components of the bacterial cell surface. For plant-associated bacteria, including azospirilla, there is some evidence for the involvement of bacterial LPSs in contacting with plant roots [1–3]. Here we present and discuss FTER spectra of LPS-containing cell surface components from two strains of A. brasilense, viz. Sp7 and Sp245, which are known to differ in the mode of plant root colonization [4] and in the responses of the host plant induced by the latter process [5].