Isabelle Leray

In this study, electrical impedance spectroscopy measurements are performed during electroporation of monolayers of differentiated myotubes. The time resolution of the system (1spectrum/ms) enable 860 full spectra (21 frequencies from 5kHz to 1.3MHz) to be acquired during the time gap between consecutive pulses (interpulse) of a classical electroporation treatment (8 pulses, 100μs, 1Hz). Additionally, the characteristics of the custom microelectrode assembly used allow the experiments to be performed directly in situ in standard 24 multi-well plates. The impedance response dynamics are studied for three different electric field intensities (400, 800 and 1200V/cm). The multifrequency information, analysed with the Cole model, reveals a short-term impedance recovery after each pulse in accordance with the fast resealing of the cell membrane, and a long-term impedance decay over the complete treatment in accordance with an accumulated effect pulse after pulse. The analysis shows differences between the lowest electric field condition and the other two, suggesting that different mechanisms that may be related with the reversibility of the process are activated. As a result of the multifrequency information, the system is able to measure simultaneously the conductivity variations due to ion diffusion during electroporation. Finally, in order to reinforce the physical interpretation of the results, a complementary electrical equivalent model is used.

New fluorescent molecular sensors based on a calix[4]arene biscrown-6 ether as coordination site and BODIPY derivative as signaling unit were synthesized and their photophysical properties were characterized. The complexation properties of these sensors with potassium and cesium cations were investigated using both steady-state and time-resolved fluorescence methods. The studies show that the sensitivity with cations depends upon the position of substituted coordination site on the BODIPY core. The complexation with cations does not have much effect on the absorption and emission wavelength when the coordination site (calix[4]arene biscrown-6 ether) is introduced at the meso position of the BODIPY core. In contrast, the same calix[4]arene biscrown-6 ether attached via a styryl linker to the α-position of BODIPY core leads to a sensitive sensor for alkali cations thanks to the better conjugation between the coordination site and the BODIPY core. The complexation of cations induces a ...

... de Cachan, CNRS UMR 8537, Cachan, France 2 Laboratoire de Photophysique et Photochimie Supramoléculaires et Macromoléculaires, Institut d'Alembert (IFR 121 ... and J. Zyss, in Practical applications of microresonators in optics and photonics, A. Matsko, (CRC Press, 2009). ...

Complex formations between calix[4]arene-bis(crown-6-ether) calix-COU2 (A1) and the tetrasulfonated species calix-COUSULF (A2) with Cs(+) are investigated in water and ethanol, and in 9:1 (M1) and 1:9 (M2) H(2)O/EtOH v:v mixtures, by chemical relaxation and molecular modeling. In ethanol and M2, two Cs(+) are included in A1 in two kinetic steps, whereas complex formation in M1 becomes controlled by a slow first-order kinetic process, which is accompanied by very fast Cs(+) inclusions, second-order rate constant: k'(1) = (3.4 +/- 0.8) x 10(7) M(-1) s(-1). In water and M1, A2 forms 1:1 and 1:2 cesium complexes in a single kinetic step, whereas in M2, two Cs(+) are included in two kinetic steps. The rate and thermodynamic constants involved are reported. They show that the second-order rate constants increase with the ethanol-to-water ratio, e.g., A2, second-order rate constant for the first Cs(+) in water: k(1A2water) = (9.7 +/- 0.3) x 10(4) M(-1) s(-1) and in M2: k(1A2M2) = (6.3 +/- 0.4) x 10(9) M(-1) s(-1). The affinities of both A1 and A2 for Cs(+) also increase with the ethanol-to-water ratio, e.g., first inclusion of A1 in M1: K(1A1M1) = (5 +/- 1.3) x 10(3) and in ethanol: K(1A1EtOH) = (7 +/- 3) x 10(6). The deviation from the expected mechanism of complex formation with alkali is attributed to the comparatively more difficult access of Cs(+) to the inclusion cavity of the capped calixarene. An analysis of calix-COU2 and calix-COUSULF and their Cs(+) complexes with only one rim capped by the crown ether confirms the thermodynamic and kinetic results, by showing that the inclusion cavity of calix-COUSULF is more adapted to Cs(+) than that of calix-COU2. This added to the presence of the shielding effect of the negative sulfonates can explain that the affinity of calix-COUSULF for Cs(+) is higher than that of calix-COU2. These results can be of interest in the search of an efficient Cs(+) decontaminant.

The photophysical properties of a complex based on diphenylphosphanoethane (DPPE) fluorescent ligands linked to a europium ion have been investigated by different spectroscopic methods. Upon complexation with europium, the interaction of the phosphane oxide group with europium leads to a red shift of the absorption spectrum and a strong quenching of the ligand emission. The typical sensitized emission of Eu(3+) is observed upon excitation of the ligand with a fluorescence quantum yield of 1%. Time-resolved absorption and emission experiments have been performed in order to investigate the photophysical mechanism involved in this complex. Photophysical studies show that an energy-transfer mechanism occurs from both the first excited singlet and triplet states of the ligand, and the population of the europium ion to the (5)D(1) state takes place, from which the (5)D(0) state is populated. Additionally, electron transfer from the excited singlet state of the ligand to the europium ion appears as a very efficient process.

Olfactory receptors (ORs) are expressed in the olfactory epithelium, where they detect odorants, but also in other tissues with additional functions. Some ORs are even overexpressed in tumor cells. In this study, we identified ORs expressed in enterochromaffin tumor cells by RT-PCR, showing that single cells can co-express several ORs. Some of the receptors identified were already reported in other tumors, but they are orphan (without known ligand), as it is the case for most of the hundreds of human ORs. Thus, genes coding for human ORs with known ligands were transfected into these cells, expressing functional heterologous ORs. The in vitro stimulation of these cells by the corresponding OR odorant agonists promoted cell invasion of collagen gels. Using LNCaP prostate cancer cells, the stimulation of the PSGR (Prostate Specific G protein-coupled Receptor), an endogenously overexpressed OR, by β-ionone, its odorant agonist, resulted in the same phenotypic change. We also showed the involvement of a PI3 kinase γ dependent signaling pathway in this promotion of tumor cell invasiveness triggered by OR stimulation. Finally, after subcutaneous inoculation of LNCaP cells into NSG immunodeficient mice, the in vivo stimulation of these cells by the PSGR agonist β-ionone significantly enhanced metastasis emergence and spreading.

A new fluorescent molecular sensor for Hg2+ based on the phosphane sulfide derivative exhibits a very low detection limit in an aqueous medium (3.8 nM) with a very high selectivity over other interfering cations. The reversibility of the complexation process was also examined and was found to be successful. [structure: see text]

A series of fluorescent sensor molecules based on a phosphane sulfide derivative were designed and synthesized. The effect of the distance between the complex entities as well as the number and the length of fluorophores was investigated using both steady-state and time-resolved fluorescence methods. The complexation behavior of these sensor molecules, which have a distinct affinity for Hg(2+), is reported. The coordination of Hg(2+) induces a photoinduced electron transfer from fluorophore to the complexed mercury and results in a significant decrease of the fluorescence. Theses sensors exhibit very low detection limits in CH(3)CN/H(2)O (80/20 v:v) and excellent sensitivity to Hg(2+) over other potentially interfering cations such as Na(+), K(+), Mg(2+), Ca(2+), Cu(2+), Ag(+), Zn(2+), Cd(2+) and Pb(2+).

Aggregation-induced emission and aggregation-induced emission enhancement have attracted much attention due to their great potential in real-world applications. Up to now most of the reports are based on the restriction of free rotation of the luminogens in the aggregates. In the present work, we found that the dansyl fluorophore with typical intramolecular charge transfer characteristic also exhibited aggregation-induced emission enhancement, which was based on the change of micro-environmental polarity of the fluorophore. In the light of the phenomenon, a new water-soluble ligand bearing a tetrasulfonated calix[4]arene was constructed for ratiometric detection of Al(3+) based on an aggregation-induced emission enhancement mechanism. It displayed a distinct selectivity to Al(3+) among the tested cations in lutidine buffer solution (pH 6-7) with a detection limit of 1.8 μM. A reversible response was also demonstrated by the addition of EDTA or F(-).

A continuous effort has been devoted to the design of new fluorescent molecules in view to different applications such as molecular materials [1], probes [2] and sensors [3]. Among these fluorescent molecules, push-pull chromophores (D-π-A) undergoing photoinduced charge transfer ...

... View Within Article. 3.2. Anisyl ether substrates and the photoreaction. The anisylethers and were prepared according to the Pandey route [12] and the photoreaction used for the comparison between heterogeneous and homogeneous reaction is summarized in Scheme 3. ...

The thermodynamics and kinetics of the complexation reaction between lead ions and the fluorescent sensor Calix-DANS4 are determined to optimize the geometry of the microreactor used for the flow-injection analysis of lead and to tune the working conditions of this microdevice. Under our experimental conditions (pH 3.2, low concentration of Calix-DANS4) the 1:1 Pb(2+)-Calix-DANS4 complex is predominantly formed with a high stability constant (log K(1:1)=6.82) and a slow second-order rate constant (k=9.4×10(4) L mol(-1) s(-1)). Due to this sluggish complexation reaction, the microchannel length must be longer than 130 mm and the flow rate lower than 0.25 mL h(-1) to have an almost complete reaction at the output of the microchannel and a high sensitivity for the heavy metal detection. After determination of the values of the reaction times in our different microdevices, it is possible to simulate the calibration curves for the fluorimetric detection of lead under different conditions. An original method is also presented to determine mixing times in microreactors.

The use of a crown-ether-linked merocyanine, DCM-crown, for producing photoinduced, long-lived and reversible concentration jumps of metal cations is reexamined. In this new investigation, the excited-state behavior of DCM-crown complexed with a strontium ion in acetonitrile is found to exhibit the same trends as those previously reported with calcium and lithium ions. However, some new features provide evidence for cation photorelease to the bulk. Subpicosecond transient absorption experiments confirm the initial fast photodisruption of the interaction between the ion and the crown, and the formation of a loose complex after intramolecular charge transfer within the chromophore. Two additional steps are observed. Firstly, a continuous red shift of the gain spectrum is seen on the subnanosecond scale. It is assigned to the movement of the Sr2+ cation away from the chromophore, partly to the bulk of the solvent and partly towards the formation of an ultraloose complex with oxygen atoms of the crown. Secondly, a free-ligand-like absorption remains after the complete decay of the excited state. This band, which signals a total photorelease of the Sr2+ ion, disappears with a characteristic time of about 110 ns, attributed to the recomplexation of the crown in the ground state of the dye.