LE STUDIUM Institute for Advanced Studies

Orléans, France

LE STUDIUM Institute for Advanced Studies

Orléans, France
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Laveuf C.,French National Institute for Agricultural Research | Cornu S.,French National Institute for Agricultural Research | Guilherme L.R.G.,French National Institute for Agricultural Research | Guilherme L.R.G.,Le STUDIUM Institute for Advanced Studies | And 3 more authors.
Geoderma | Year: 2012

Redox processes, which are widespread in soils, need to be quantified for an improved comprehension of the dynamics of Fe- and Mn-oxides and their associated trace elements. The classical methodology used to study these redox processes generally relies on the quantification of all mineral species in the various pedological features that can be related to different redox stages. However, this approach usually encounters the difficulty of precisely quantifying the different forms of poorly crystallised Fe- and Mn-oxides. In this study, we use the signature of rare earth elements (REEs) to visualise and, eventually, quantify the importance of redox processes in soils. Our approach relies on that developed by Laveuf et al. (2008) and the idea that the relative contribution to the mobilisation of REEs that is made by the primary minerals reactive to redox conditions depends on the following factors: (i) their initial proportion in the different pedological features that can be related to various redox processes, (ii) their relative mobilisation during the redox process in question, and (iii) their initial REE signatures. The catena studied is characterised by two stages of redox conditions: the first is related to the formation and subsequent dissolution of Fe-Mn concretions, and the second is related to the bleaching of the soil matrix due to morphological degradation. In this soil, the main minerals reactive to redox conditions are Mn-oxides, ferrihydrite, goethite and (fluor)apatite. The results indicate that the primary redox conditions can be characterised by a positive Ce anomaly on the REE pattern, which has been attributed to a preferential immobilisation of this element, due to its association with Mn-oxides. The results also indicate that the secondary redox conditions can be characterised by depletion in medium REEs (MREEs) in the REE pattern, which has been attributed to a preferential release of these elements during the dissolution of (fluor)apatite and, to a lesser extent, of ferrihydrite. These results emphasise the potential of REE signatures of the visualisation of the various redox processes that have been active in a soil. Additionally, REE signatures are a proxy of the frequency and intensity of the redox conditions. © 2011 Elsevier B.V.

Ulloa-Aguirre A.,French National Institute for Agricultural Research | Ulloa-Aguirre A.,French National Center for Scientific Research | Ulloa-Aguirre A.,University of Tours | Ulloa-Aguirre A.,LE STUDIUM Institute for Advanced Studies | And 13 more authors.
Reviews in Endocrine and Metabolic Disorders | Year: 2011

Gonadotropins play a central role in the control of male and female reproduction. Selective agonists and antagonists of gonadotropin receptors would be of great interest for the treatment of infertility or as non steroidal contraceptive. However, to date, only native hormones are being used in assisted reproduction technologies as there is no pharmacological agent available to manipulate gonadotropin receptors. Over the last decade, there has been a growing perception of the complexity associated with gonadotropin receptors' cellular signaling. It is now clear that the Gs/cAMP/PKA pathway is not the sole mechanism that must be taken into account in order to understand these hormones' biological actions. In parallel, consistent with the emerging paradigm of biased agonism, several examples of ligand-mediated selective signaling pathway activation by gonadotropin receptors have been reported. Small molecule ligands, modulating antibodies interacting with the hormones and glycosylation variants of the native glycoproteins have all demonstrated their potential to trigger such selective signaling. Altogether, the available data and emerging concepts give rise to intriguing opportunities towards a more efficient control of reproductive function and associated disorders. © Springer Science+Business Media, LLC 2011.

Sinturel C.,CNRS Center for Research on Divided Matter | Vayer M.,CNRS Center for Research on Divided Matter | Morris M.,University College Cork | Hillmyer M.A.,University of Minnesota | Hillmyer M.A.,LE STUDIUM Institute for Advanced Studies
Macromolecules | Year: 2013

This Perspective provides a critical analysis of the current knowledge concerning solvent vapor annealing (SVA) of block polymer thin films. Herein, we identify key challenges that will be important to overcome for future development of SVA as a practical, reliable, and universal technique for the valorization of block polymer thin films in a wide range of technologies. The Perspective includes a brief background on thin film block polymer self-assembly, a historical account of the SVA technique, an overview of the SVA fundamentals that are necessary to develop a more comprehensive picture of the overall process, and summaries of relevant and important contributions from the recent literature. We also offer our outlook on SVA and suggest important future directions. © 2013 American Chemical Society.

Debroye E.,Catholic University of Leuven | Eliseeva S.V.,CNRS Center for Molecular Biophysics | Eliseeva S.V.,Le Studium Institute for Advanced Studies | Laurent S.,University of Mons | And 4 more authors.
Dalton Transactions | Year: 2014

The synthesis and characterization of two novel DTPA bisamide derivatives DTPA-BC12PheA and DTPA-BC14PheA functionalized with p-dodecylaniline and p-tetradecylaniline are described. The ligands were coordinated to Gd(iii) and Eu(iii), resulting in highly paramagnetic and luminescent complexes, respectively. Mixed micelles consisting of Gd/Eu-DTPA-BC12PheA and DTPA-BC14PheA with a homogeneous size distribution (33-40 nm) were prepared by the assembly of the amphiphilic complexes with phospholipid DPPC and a surfactant Tween 80®. Taking into account the sensitivity difference between magnetic resonance and optical imaging techniques, the ratios of Gd and Eu complexes (Gd/Eu) 1:1, 2:1, 3:1, 20:1 and 50:1 were combined in one single micelle and their optical and relaxometric properties were characterized in detail. Upon excitation at 290 nm, the micelles display characteristic red emission bands due to the 5D0→7FJ (J = 0-4) transitions of Eu(iii). The number of water molecules in the first coordination sphere of Eu(iii) (qEu = 0.1-0.2) was calculated from the lifetime measurements performed in H2O and D2O solutions. Micelles composed of exclusively europium complexes display quantum yields in the range of 1.0%, decreasing with the europium concentration when going from 1:1 to 50:1 Gd/Eu contents. The ligand-to-lanthanide sensitization efficiency for micelles consisting of Eu-DTPA-BC12PheA and Eu-DTPA-BC14PheA equals 3.8% and 4.1%, respectively. The relaxivity r1 per Gd(iii) ion at 40 MHz and 310 K reaches a maximum value of 14.2 s-1 mM-1 for the Gd-DTPA-BC12PheA assemblies and 16.0 s-1 mM -1 for the micellar Gd-DTPA-BC14PheA assemblies compared to a value of 3.5 s-1 mM-1 for Gd-DTPA (Magnevist®). Theoretical fitting of the 1H NMRD profiles results in τR values of 4.2 to 6.6 ns. The optimal concentration ratio of Gd/Eu compounds in the micelles in order to provide the required bimodal performance has been determined to be 20:1. In the search for other bimodal systems, this discovery can be used as a guideline concerning the load of paramagnetic agents with respect to luminescent probes. © 2014 The Royal Society of Chemistry.

Debroye E.,Catholic University of Leuven | Eliseeva S.V.,CNRS Center for Molecular Biophysics | Eliseeva S.V.,Le STUDIUM Institute for Advanced Studies | Laurent S.,University of Mons | And 5 more authors.
European Journal of Inorganic Chemistry | Year: 2013

Diethylenetriaminepentaacetic acid (DTPA)-bisamide derivatives functionalized with p-toluidine, 6-aminocoumarin, 1-naphthalene methylamine and 4-ethynylaniline were synthesized and fully characterized by mass spectrometry, NMR spectroscopy, FTIR spectroscopy and elemental analysis. LnIII complexes (Ln = Gd, Eu, Tb, Y) of the ligands DTPA-bis-p-toluidineamide (DTPA-BTolA), DTPA-bis-6-coumarinamide (DTPA-BCoumA), DTPA-bis-1- naphthylmethylamide (DTPA-BNaphA) and DTPA-bis-4-ethynylphenylamide (DTPA-BEthA) were prepared and studied for their bimodal magnetic resonance imaging/optical properties. EuIII and TbIII derivatives in aqueous solutions exhibit characteristic red and green emission, respectively, with quantum yields of 0.73 % for EuIII-DTPA-BNaphA and 2.5 % for Tb III-DTPA-BEthA. Ligand-centred photophysical properties of the GdIII complexes were investigated to gain insight into energy-transfer processes that take place in these systems. The GdIII complexes were also analyzed by nuclear magnetic relaxation dispersion (NMRD) techniques. The relaxivity (r1) at 20 MHz and 310 K equals 4.1 s -1 mM-1 for Gd-DTPA-BTolA, 5.1 s-1 mM -1 for Gd-DTPA-BCoumA, 6.4 s-1 mM-1 for Gd-DTPA-BNaphA and 5.7 s-1 mM-1 for Gd-DTPA-BEthA. These values are higher than the value of 3.8 s-1 mM-1 for Gd-DTPA (Magnevist). The improved relaxivity is due to the increase in the rotational tumbling time τR with a factor of 1.6 for Gd-DTPA-BTolA, 2.1 for Gd-DTPA-BCoumA, 3.1 for Gd-DTPA-BNaphA and 6.5 for Gd-DTPA-BEthA. In a 4 % human serum albumin solution, the apparent relaxivity at 20 MHz increases to values of 13.9 and 19.1 s-1 mM-1 for Gd-DTPA-BNaphA and Gd-DTPA-BEthA, respectively. All these features assist the search for optimal bimodal optical and magnetic resonance imaging probes. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Zaim A.,University of Geneva | Favera N.D.,University of Geneva | Guenee L.,University of Geneva | Nozary H.,University of Geneva | And 5 more authors.
Chemical Science | Year: 2013

This work demonstrates how minor structural and electronic changes between Ln(NO3)3 and Ln(hfac)3 lanthanide carriers (Ln = trivalent lanthanide, hfac = hexafluoroacetylacetonate) lead to opposite thermodynamic protocols for the metal loading of luminescent polynuclear single-stranded oligomers. Whereas metal clustering is relevant for Ln(hfac)3, the successive fixation of Ln(NO3)3 provides stable microspecies with an alternated occupancy of the binding sites. Partial anion dissociation and anion/ligand bi-exchange processes occur in polar aprotic solvents, which contribute to delay the unambiguous choice of a well-behaved neutral lanthanide carrier for the selective complexation of different trivalent lanthanides along a single ligand strand. Clues for further improvement along this stepwise strategy are discussed. © 2013 The Royal Society of Chemistry.

Tranchant T.,CNRS Physiology of Reproduction and Behaviors | Tranchant T.,French National Center for Scientific Research | Tranchant T.,University of Tours | Tranchant T.,Laboratoire Of Biologie Of La Reproduction | And 20 more authors.
Molecular and Cellular Endocrinology | Year: 2011

The A189 V inactivating mutation of the human FSH receptor (FSHR) leads to subfertility in men and primary ovarian failure in women. This mutation has previously been associated with intracellular retention of the FSHR and impaired cAMP production. Here, we show that the A189 V FSHR stably expressed in HEK293N cells provoked ERK MAP kinases phosphorylation through β-arrestins, independently of the canonical cAMP/PKA pathway. Interesting, both the A189 V and wild-type (Wt) FSHRs selectively activated cAMP-independent ERK phosphorylation when expressed at low plasma membrane densities. These data indicate that the selective intracellular signalling triggered by the A189 V FSHR resulted from reduced membrane expression rather than by switching receptor coupling. Hence, receptor density at the plasma membrane might control the balance between distinct signal transduction mechanisms. Furthermore, our results help to clarify why mutations of FSHβ are more deleterious to human fertility than the FSHR A189 V mutation which preserves parts of receptor signalling repertoire. © 2010 Elsevier Ireland Ltd.

Westall F.,CNRS Center for Molecular Biophysics | Campbell K.A.,CNRS Center for Molecular Biophysics | Campbell K.A.,LE STUDIUM Institute for Advanced Studies | Campbell K.A.,University of Auckland | And 10 more authors.
Geology | Year: 2015

Interacting, diverse microbe-sediment systems exist in natural environments today but have not yet been recognized in the oldest records of life on Earth (older than 3.3 Ga) because of lack of distinctive biomarker molecules and patchy preservation of microbial paleocommunities. In an in-situ outcrop- to microbial-scale study, we have differentiated probable phototrophic, chemolithotrophic, and chemo-organotrophic fossil microbial signatures in a nearshore volcanogenic sedimentary setting in 3.33 Ga rocks of the Josefsdal Chert, Barberton greenstone belt, South Africa, while demonstrating the importance of contemporaneous hydrothermal activity. Hydrothermal fluids, as a nutrient source, strongly controlled the development and distribution of the microbial communities and, as a silicifying agent, contributed to their rapid fossilization. We thus show that intricate microbe-sediment systems are deep-rooted in time and that at least some early life may indeed have been thermophilic. © 2015 Geological Society of America.

van Putten M.J.A.M.,University of Twente | van Putten M.H.P.M.,Le Studium Institute for Advanced Studies
Clinical Neurophysiology | Year: 2010

Objective: In patients suffering from severe hypoxia, the EEG may show a burst-suppression pattern, characterized by low-voltage activity and the occurrence of high amplitude burst-like events. We describe the two-timescale burst phenomenology of this postanoxic condition. Methods: We present EEG recordings showing remarkable burst phenomenology in two postanoxic patients and consider potential mechanisms responsible for the generation of the burst-suppression patterns. We quantify the postanoxic condition in terms of the dimension (number of degrees of freedom) of its dynamics by comparing our data with a system of three ordinary differential equations with two timescales subject to varying degrees of noise. Results: EEGs displayed extreme similarity of the bursts, separated by interburst intervals up to more than 300. s. This pattern reflects a significant reduction in the number of functional brain states. This post-anoxic condition is found to have dimension 3, consisting of fast dynamics responsible for the bifurcation to bursting behavior, and a long time-scale responsible for burst termination and the interburst intervals. Conclusions: Low-dimensional postanoxic brain states, as manifested by burst-similarity, appears to indicate an irreversible loss of brain function and consciousness. Significance: Evidence of brain functionality in a persistent low dimensional state due to severe hypoxia is indicative of permanent loss of consciousness with essentially no chance for recovery. Quantitative evidence for such degenerate states is important for clinical decision making. © 2010 International Federation of Clinical Neurophysiology.

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