PubMed Health⌕ Search

Biomedical subjects

Christophe Moulin

Publications and source records attributed to Christophe Moulin.

At least 19 recordsLinked to original sources
PubMed2006

Experimental and molecular dynamics studies of dysprosium(III) salt solutions for a better representation of the microscopic features used within the binding mean spherical approximation theory.

This work is aimed at a predictive description of the thermodynamic properties of actinide(III) salt solutions at high concentration and 25 degrees C. A new solution of the binding mean spherical approximation (BIMSA) theory, based on the Wertheim formalism, for taking into account 1:1 and also 1:2 complex formation, is used to reproduce, from a simple procedure, experimental osmotic coefficient variation with concentration for three binary salt solutions of the same lanthanide(III) cation: dysprosium(III) perchlorate, nitrate, and chloride. The relevance of the fitted parameters is discussed, and their values are compared with available literature values. UV-vis/near-IR, time-resolved laser-induced fluorescence spectroscopy experiments, and molecular dynamics (MD) calculations were conducted for dilute to concentrated solutions (ca. 3 mol.kg-1) for a study of the microscopic behavior of DyCl3 binary solutions. Coupling MD calculations and extended X-ray absorption fine structure led to the determination of reliable distances. The MD results were used for a discussion of the parameters used in the BIMSA.

Journal Article↗
PubMed2006

Actinide speciation in relation to biological processes.

In case of accidental release of radionuclides into the environment, actinides represent a severe health risk to human beings following internal contamination (inhalation, ingestion or wound). For a better understanding of the actinide behaviour in man (in term of metabolism, retention, excretion) and in specific biological systems (organs, cells or biochemical pathways), it is of prime importance to have a good knowledge of the relevant actinide solution chemistry and biochemistry, in particular of the thermodynamic constants needed for computing actinide speciation. To a large extent, speciation governs bioavailability and toxicity of elements and has a significant impact on the mechanisms by which toxics accumulate in cell compartments and organs and by which elements are transferred and transported from cell to cell. From another viewpoint, speciation is the prerequisite for the design and success of potential decorporation therapies. The purpose of this review is to present the state of the art of actinide knowledge within biological media. It is also to discuss how actinide speciation can be determined or predicted and to highlight the areas where information is lacking with the aim to encourage new research efforts.

Actinoid Series Elements↗
PubMed2006

Sorption of Aldrich humic acid onto hematite: insights into fractionation phenomena by electrospray ionization with quadrupole time-of-flight mass spectrometry.

Sorption induced fractionation of purified Aldrich humic acid (PAHA) on hematite is studied through the modification of electrospray ionization (ESI) quadrupole time-of-flight (QToF) mass spectra of supernatants from retention experiments. The ESI mass spectra show an increase of the "mean molecular masses" of the molecules that constitutes humic aggregates. The low molecular weight fraction (LMWF; m/z < or = 600 Da) is preferentially sorbed compared to two other fractions. The resolution provided by ESI-QToF mass spectrometer in the low-mass range provided evidence of further fractionation induced by sorption within the LMWF. Among the two latter fractions, the high molecular weight fraction (HMWF; m/z approximately 1700 Da) seems to be more prone to sorption compared to the intermediate molecular weight fraction (IMWF; m/z approximately 900 Da). The IMWF seems to be more hydrophilic as it should be richer in O, N, and alkyl C from the proportion of even mass, and poorer in aromatic structures from mass defect analysis in ESI mass spectra.

Adsorption↗
PubMed2006

The early responses of Arabidopsis thaliana cells to cadmium exposure explored by protein and metabolite profiling analyses.

To get more insight into plant cell response to cadmium (Cd) stress, both proteomic and metabolomic "differential display" analyses were performed on Arabidopsis thaliana cells exposed to different concentrations of the toxic chemical. After a 24 h treatment, soluble proteins extracted from untreated and treated cells were separated by 2-D-PAGE and image analyses were performed to quantify and compare protein levels. Proteins up- and down-regulated in response to Cd were identified by MS and mapped into specific metabolic pathways and cellular processes, highlighting probable activation of the carbon, nitrogen, and sulfur metabolic pathways. For some of these proteins, Northern blot and RT-PCR analyses were performed to test transcript accumulation in response to Cd. In parallel, metabolite profiling analyses by LC coupled to ESI MS were initiated to better characterize the metabolic adaptation to the chemical stress. This study revealed that the main variation at the metabolite level came from the presence of six different families of phytochelatins, in A. thaliana cells treated with Cd, whose accumulation increases with Cd concentrations. Taken together these data provide an overview of the molecular and cellular changes elicited by Cd exposure.

Amino Acids↗
PubMed2005

Sulfate complexation of trivalent lanthanides probed by nanoelectrospray mass spectrometry and time-resolved laser-induced luminescence.

Sulfate complexation of lanthanides is of great interest for predicting speciation of radionuclides in natural environments. The formation of LaSO4+(aq) in HNO3/H2SO4 aqueous solutions of low ionic strength (I) was studied by nanoelectrospray ionization mass spectrometry (nanoESI-MS). Several gaseous species containing LaSO4+ were detected. The formation constant of LaSO4+(aq) was determined and extrapolated to I = 0 (log = 3.5 +/- 0.3) by using a simple specific ion interaction theory (SIT) formula. This value supports the potential of nanoESI-MS for the study of kinetically labile species. The species La(SO4)(2-) was also detected. In addition, time-resolved laser-induced luminescence (TRLIL) was used to study Eu(III) speciation under ionic conditions of 0.02-0.05 M H+ (H2SO4/HClO4) and 0.4-2.0 M Na+ (Na2SO4/NaClO4). The data were interpreted with the species EuSO4+ (log = 3.7(8) +/- 0.1) and Eu(SO4)(2-) (log = 1.5 +/- 0.2). For extrapolating to I = 0, all of the major ions were taken into account through several SIT ion-pair parameters, epsilon. Most of the epsilon values were estimated by analogy to known parameters for similar ion-pair interactions using linear correlations, while epsilon(Eu)3+,SO4(2-) = 0.8(6) +/- 0.5 was fitted to the experimental data because, to date, SIT coefficients between multicharged species are not reported. The formation constants obtained here confirm some of those previously measured for Ln(III) and An(III) by various experimental techniques, and conversely do not give credit to the idea that in equilibrium conditions TRLIL and other spectroscopic techniques would provide stability constants of only inner-sphere complexes. The fluorescence lifetimes measured for EuSO4+ and Eu(SO4)(2-) were consistent with the replacement of one H2O molecule in the first coordination sphere of Eu3+ for each added SO4(2-) ligand, suggesting a monodentate SO4(2-) coordination.

Lanthanoid Series Elements↗
PubMed2005

Stabilities of the aqueous complexes Cm(CO3)33- and Am(CO3)33- in the temperature range 10-70 degrees C.

The carbonate complexation of curium(III) in aqueous solutions with high ionic strength was investigated below solubility limits in the 10-70 degrees C temperature range using time-resolved laser-induced fluorescence spectroscopy (TRLFS). The equilibrium constant, K(3), for the Cm(CO(3))(2-) + CO(3)(2-) right harpoon over left harpoon Cm(CO(3))(3)(3-) reaction was determined (log K(3) = 2.01 +/- 0.05 at 25 degrees C, I = 3 M (NaClO(4))) and compared to scattered previously published values. The log K(3) value for Cm(III) was found to increase linearly with 1/T, reflecting a negligible temperature influence on the corresponding molar enthalpy change, Delta(r)H(3) = 12.2 +/- 4.4 kJ mol(-1), and molar entropy change, Delta(r)S(3) = 79 +/- 16 J mol(-1) K(-1). These values were extrapolated to I = 0 with the SIT formula (Delta(r)H(3) degrees = 9.4 +/- 4.8 kJ mol(-1), Delta(r)S(3) degrees = 48 +/- 23 J mol(-1) K(-1), log K(3) degrees = 0.88 +/- 0.05 at 25 degrees C). Virtually the same values were obtained from the solubility data for the analogous Am(III) complexes, which were reinterpreted considering the transformation of the solubility-controlling solid. The reaction studied was found to be driven by the entropy. This was interpreted as a result of hydration changes. As expected, excess energy changes of the reaction showed that the ionic strength had a greater influence on Delta(r)S(3) than it did on Delta(r)H(3).

Journal Article↗
PubMed2005

Discovery of powerful uranyl ligands from efficient synthesis and screening.

New tripodal gem-(bis-phosphonates) uranophiles were discovered by a screening method that allowed for the selection of ligands with strong uranyl-binding properties in a convenient microtiter-plate format. The method is based on competitive uranium binding by using Sulfochlorophenol S as chromogenic chelate. This dye compound was found to present high uranyl complexation properties and allowed to highlight ligands presenting association constants for UO(2+)(2) up to 10(18) at pH 7.4 and 10(20) at pH 9. A collection of 40 known ligands including polycarboxylate, hydroxamate, catecholate, hydroxypyridonate and hydroxyquinoline derivatives was tested. Also screened was a combinatorial library prepared from seven amine scaffolds and eight acrylates bearing diverse chelating moieties. Among these 96 tested candidates, a tripod derivative bearing gem-bis-phosphonates moieties was found to present the highest complexation properties over a wide range of pH and was further studied.

Hydrogen-Ion Concentration↗
PubMed2005

On the use of spectroscopic techniques for interaction studies, part I: complexation between europium and small organic ligands.

In the framework of environmental studies, it is important to understand the interaction of humic substances with cations (heavy metals, radionuclides) and to determine their complexation constants in order to evaluate their potential impact on their fate. For this purpose, two techniques have been used: electrospray ionization mass spectrometry, a newly used technique in speciation studies, and time-resolved laser-induced fluorescence spectrometry, a well-known technique for such studies. As a first step, for simplification purposes and to compare both techniques, simple molecules having functional groups present in humic substances have been selected, such as acetic, glycolic, and 4-hydroxyphenylacetic acids. Both techniques have been used to obtain stoichiometries and complexation constants between these simple molecules and europium (III).

Europium↗
PubMed2005

Cobalt speciation study in the cobalt-cysteine system by electrospray ionization mass spectrometry and anion-exchange chromatography inductively coupled plasma atomic emission spectrometry.

This paper describes the ability of the combination of electrospray ionization mass spectrometry (ESI-MS) and anion-exchange chromatography coupled with inductively coupled plasma atomic emission spectrometry (AEC-ICP-AES) for cobalt speciation study in the binary cobalt-cysteine system. ESI-MS, allowing the identification and the characterization of the analytes, is used as a technique complementary to AEC-ICP-AES, providing elemental information on the separated species. The methods have been developed through the study of samples containing Co2+ and 1-fold to 5-fold molar ratios of cysteine over a pH range 2.5 to 11. In each case, cobalt-cysteine complexes were characterized by ESI-MS in negative ion mode. AEC-ICP-AES allowed further separation and detection of the cobalt species previously characterized. The strong influence of pH and ligand-to-metal ratios on the nature and stoichiometry of the species is demonstrated. For the first time, a direct experimental speciation diagram of cobalt species has been established owing to these analytical techniques. This work is a promising basis for the speciation analysis of cobalt, since a good knowledge of cobalt speciation is of prime importance to better understanding its fate in biological and environmental media.

Anion Exchange Resins↗
PubMed2004

Europium(III) interaction with a polyaza-aromatic extractant studied by time-resolved laser-induced luminescence: a thermodynamical approach.

The 2,6-bis(5,6-dialkyl-1,2,4-triazin-3-yl)pyridines (DATPs) belong to a new family of extracting agents recently developed in the framework of nuclear fuel reprocessing. These molecules exhibit exceptional properties to separate actinides(III) from lanthanides(III) in nitric acid solutions. In a previous work, the use of electrospray ionization mass spectrometry (ESI-MS) provided data such as stoichiometries and conditional stability constants of various DATP complexes with europium and evidenced the unusual capability of DiPTP [bis(di-iso-propyltriazinyl)pyridine] ligand to form 1:3 complexes in nitric acid solution. This latter result has then been further investigated by considering DiPTP complexation features with the complete lanthanide family. Moreover, a complementary study of equilibria in solution with a non intrusive technique such as time-resolved laser-induced luminescence (TRLIL) seemed quite promising to determine thermochemical data such as enthalpy and entropy variations associated with the complexation reaction between Eu(III) and DiPTP. Furthermore, this TRLIL study may also allow ensuring that the observations made on mass spectra actually reflected the equilibrium in solution and not an intermediate state between liquid phase and gaseous phase. The investigation of europium(III) complexation with DiPTP by TRLIL described in this paper first led to highlight the exclusive formation of a 1:3 complex between europium(III) and the DiPTP ligand, specificity already pointed out by ESI-MS. Two different calculation methods, using either luminescence spectra and luminescence decay curves, have then been used to measure the conditional stability constant of the [Eu(DiPTP)(3)](3+) complex. Both methods gave similar results (log beta3(app)= 14.3 +/- 0.6 at pH 2.8) in good agreement with the one previously reported in ESI-MS studies (log beta3(app)= 14.0 +/- 0.6 at pH 2.8). Moreover, while considering the influence of temperature on the value of the stability constant, it was possible to estimate the enthalpy (DeltaH(beta3) = -29 +/- 3 kJ mol(-1) at pH 2.8) and entropy variations (DeltaS(beta3) = 173 +/- 10 J K(-1) mol(-1) at pH 2.8) associated with the [Eu(DiPTP)(3)](3+) complex formation.

Journal Article↗
PubMed2003

Investigation of the interaction between 1-hydroxyethane-1,1'-diphosphonic acid (HEDP) and uranium(VI).

A detailed study, using a panel of spectroscopic analytical methods, of the complexation between 1-hydroxyethane-1,1'-diphosphonic acid (HEDP) and uranyl ion (UO(2)(2+)) is reported. Results suggest that the metal complex is present as only 1:1 (metal/ligand) species at low concentration (<10(-)(4) M). The conditional constants of this complex were determined at various pH using time-resolved laser-induced fluorescence (TRLIF) and electrospray ionization mass spectrometry (ESI-MS). Further investigations indicate the presence of a 1:2 (metal/ligand) complex at higher concentrations ( approximately 10(-)(2) M). Selectivity studies as well as structural aspects are presented.

Journal Article↗
PubMed2003

Trivalent lanthanide interactions with a terdentate bis(dialkyltriazinyl)pyridine ligand studied by electrospray ionization mass spectrometry.

The 2,6-bis(5,6-dialkyl-1,2,4-triazin-3-yl)pyridines (DATPs) belong to a new family of extracting agents recently developed in the framework of nuclear fuel reprocessing. These molecules exhibit exceptional properties to separate actinides(III) from lanthanides(III) in nitric acid solutions. A previous work showed that electrospray ionization mass spectrometry (ESI-MS) is a reliable technique to provide solution data such as stoichiometries and conditional stability constants of various DATP complexes with europium and evidenced the unusual capability of DiPTP [bis(di-iso-propyltriazinyl)pyridine] ligand to form 1:3 complexes in nitric acid solution. This latter result is further investigated by considering DiPTP complexation features with the complete lanthanide family. As a starting point of the experimental procedure used for stability constant evaluation, the intensity distribution of ions detected by ESI-MS is studied for solutions containing Ln(NO(3))(3) in water/methanol (1:1 v/v) with the pH value set at 2.8 and 4.6 by HNO(3) additions. At pH 2.8, the nitrate anions are found to prevent lanthanides from processes occurring within the ion source: redox phenomena or gas-phase reactions with methanol which give species such as [Ln(MeO)(2)](+). Thus, the total intensity of MS signals from [Ln(NO(3))(2)(H(2)O)(p)(MeOH)(n)](+) ions is found proportional to the metal ion concentration. At pH 4.6, with lower nitrate concentration, the nature of the species identified on mass spectra depends on the electronic properties of the lanthanide elements. It is shown that Ln(III) complexation with DiPTP leads to the exclusive formation of 1:3 complexes with the whole lanthanide series which may be due not only to the hydrophobic exterior of the ligand but also to the unusual electronic density distribution in DATP ligands as compared with other aza-aromatic ligands. The conditional stability constants of the 1:3 lanthanide(III) complexes with DiPTP have been determined at pH 2.8 and are found to increase almost regularly from La (log beta(3)(app) = 11.7 +/- 0.1) to Lu (log beta(3)(app) = 16.7 +/- 0.8). Moreover, the kinetic stability of the gas-phase 1:3 complexes obtained by electrospray has been investigated by energy-resolved collision-induced dissociation and provides useful information on the bonding and structure.

Journal Article↗
PubMed2003

Analysis of the metal-binding selectivity of the metallochaperone CopZ from Enterococcus hirae by electrospray ionization mass spectrometry.

Metallochaperones are soluble proteins involved in metal transport and regulation in vivo. Copper metallochaperones belong to a structural family of metal binding domains displaying a ferredoxin-like fold (betaalphabetabetaalphabeta) and a consensus metal-binding motif MXCXXC. The metal-binding selectivities for this class of proteins are poorly documented so far. The present study focuses on the measurement of the selectivity of the copper metallochaperone CopZ from Enterococcus hirae for different metal ions using an experimental approach based on electrospray ionization mass spectrometry (ESI-MS). All the metal cations tested, i.e. Cu(I), Cu(II), Hg(II), Cd(II) and Co(II), form specific metal complexes with CopZ. The study of a chemically modified CopZ as well as variants of CopZ in the active site demonstrated that the complexes observed by ESI-MS, i.e. in the gas phase, corresponded to the complexes previously observed by other analytical methods in solution. Competition experiments allowed the classification of the metal ions by increasing affinities for CopZ as follows: Co << Cd < Hg < Cu. A dissociation constant in the range of 20 microM was determined for cobalt. The affinity of CopZ for the other metals tested was found to be higher, with dissociation constants smaller than micromolar.

Bacterial Proteins↗
PubMed2003

Gas-phase reactivity of silver and copper coordinated monosaccharide cations studied by electrospray ionization and tandem mass spectrometry.

The analytical distinction of the most common isomeric underivatized hexoses was investigated by means of mass spectrometry experiments. Electrospray ionization and tandem mass spectrometry were used in the analysis of silver and copper-coordinated monosaccharides (D-glucose, D-galactose, D-fructose, O-methyl-alpha-D-glucose and O-methyl-beta-D-glucose). The results show that cationization by Ag(+) allows the differentiation of the three first monosaccharides while the complexes formed by association of Cu(+) with these three monosacharides display a similar reactivity that prevents stereoisomer distinction. Unlike copper, silver adduct-ions of both alpha and beta anomeric O-methyl-D-glucoses exhibit specific decomposition patterns (i.e. a loss of methanol for the alpha-anomer and a loss of silver hydride for the beta-anomer), which allow an easy characterization. A theoretical survey of selected complexes, based on the use of DFT calculations were carried out on both anomers in order to rationalize the experimental findings.

Cations↗
PubMed2003

Aqueous solutions of uranium(VI) as studied by time-resolved emission spectroscopy: a round-robin test.

Results of an inter-laboratory round-robin study of the application of time-resolved emission spectroscopy (TRES) to the speciation of uranium(VI) in aqueous media are presented. The round-robin study involved 13 independent laboratories, using various instrumentation and data analysis methods. Samples were prepared based on appropriate speciation diagrams and, in general, were found to be chemically stable for at least six months. Four different types of aqueous uranyl solutions were studied: (1) acidic medium where UO2(2+)aq is the single emitting species, (2) uranyl in the presence of fluoride ions, (3) uranyl in the presence of sulfate ions, and (4) uranyl in aqueous solutions at different pH, promoting the formation of hydrolyzed species. Results between the laboratories are compared in terms of the number of decay components, luminescence lifetimes, and spectral band positions. The successes and limitations of TRES in uranyl analysis and speciation in aqueous solutions are discussed.

Chemistry Techniques, Analytical↗
PubMed2003

Speciation studies on DTPA using the complementary nature of electrospray ionization mass spectrometry and time-resolved laser-induced fluorescence.

Decorporation of radionuclides is of continuous interest in order to reduce doses in case of occupational or accidental human exposure. In the present study, insights into the non-covalent interactions that hold the well-known chelating agent DTPA (diethylenetriaminepentaacetic acid) with inorganic elements of interest, such as europium and strontium, and their ability to form stable complexes, are investigated with two spectroscopic techniques, i.e., electrospray ionization mass spectrometry (ESI-MS) and time-resolved laser-induced fluorescence (TRLIF). First investigations are on DTPA and europium alone and end with a complete study of the Eu-DTPA system. The pH variation allows one to readily investigate whether different species (protonated, hydrolyzed, etc.) exist in the pH range 2-9 and evaluate the stoichiometry and conditional stability constant for the Eu-DTPA complex. Additional experiments by ESI-MS are reported for Sr(II) in interaction with DTPA and EDTA.

Decontamination↗
PubMed2002

Use of electrospray mass spectrometry (ESI-MS) for the study of europium(III) complexation with bis(dialkyltriazinyl)pyridines and its implications in the design of new extracting agents.

ESI mass spectrometry was used to investigate the europium complexation by tridentate ligands L identical with 2,6-bis(5,6-dialkyl-1,2,4-triazin-3-yl)-pyridines (DATP) that have shown unique separation properties of actinides(III) from lanthanides(III) in nitric acid solutions. Complexes of three ligands, namely methyl (DMTP), n-propyl (DnPTP), and iso-propyl (DiPTP), have been investigated in acidic solutions to check the aqueous-phase stability of Eu(L)(3)(3+) ions identified previously in the solid state. The data obtained show, first, the presence of stable Eu(L)(3)(3+) ions with DnPTP (log beta(3)(app) = 12.0 +/- 0.5) and DiPTP (log beta(3)(app) = 14.0 +/- 0.6) in methanol/water (1:1 v/v) solutions under pH range 2.8-4.6 and, second, a mechanism whereby alkyl moieties contribute to a self-assembling process leading to the formation of Eu(L)(3)(3+) ions. Other complexes such as Eu(L)(2)(3+) ions are only observed for DnPTP (log beta(2)(app) = 6.7 +/- 0.5) and DMTP (log beta(2)(app) = 6.3 +/- 0.1) and Eu(L)(3+) only for DMTP (log beta(1)(app) = 2.9 +/- 0.2). The log beta(n)(app) values for the Eu(L)(n)(3+) (n = 1-3) complexes were determined at pH 2.8. Better insight was given in this study concerning the role of the hydrophobic exterior of the ligands for the design of a new range of extracting agents.

Journal Article↗