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  • Polarization rotation in a second harmonic reflection experiment from an isotropic surface of chiral Tröger base
    • Hache François
    • Boulesteix T.
    • Schanne-Klein Marie-Claire
    • Alexandre M.
    • Lemercier G.
    • Andraud Chantal
    Journal of Physical Chemistry B, American Chemical Society , 2003, 107 (22), pp.5261 . Polarization rotation in second harmonic reflection (ORD-SHR) is carefully investigated. After emphasizing the relevance of this technique for characterization of chiral molecules the optical activity of which arises from electric contributions, we bring an experimental demonstration with a specially synthesized acridine-substituted Tröger base, which displays very strong rotations. Measurements of this rotation for wavelengths spanning the absorption spectrum are satisfactorily reproduced by a model based on coupled, anharmonic oscillators. (10.1021/jp034216+)
    DOI : 10.1021/jp034216+
  • Comment on "coherent nonlinear optical response of single quantum dots studied by ultrafast near-field spectroscopy
    • Joffre Manuel
    Physical Review Letters, American Physical Society , 2003, 90 (13), pp.139701/1 . A Comment on the Letter by Tobias Guenther et al., Phys. Rev. Lett. 89 057401 (2002). The authors of the Letter offer a Reply. (10.1103/PhysRevLett.90.139701)
    DOI : 10.1103/PhysRevLett.90.139701
  • Dynamic saturation of an intersublevel transition in self-organized InAs/In(x)A(1-x)lAs quantum dots
    • Peronne Emmanuel
    • Fossard F.
    • H. Julien F.
    • Brault J.
    • Gendry M.
    • Salem B.
    • Bremond G.
    • Alexandrou Antigoni
    Physical Review B: Condensed Matter and Materials Physics (1998-2015), American Physical Society , 2003, 67 (20), pp.205329 . We have observed a dynamic saturation of an intersublevel transition in InAs/InxAl1-xAs quantum dots related to the discrete nature of electron states using midinfrared femtosecond spectroscopy. This dynamic saturation is a consequence of the gradual filling of the discrete quantum-dot electron states due to the capture of electrons injected in the barrier. Our interpretation of the differential transmission experiments is confirmed by a comparison with a rate-equation model with the capture and intersublevel relaxation time as fit parameters yielding 10 ps and 1 ps, respectively. We discuss the mechanism responsible for these relaxation times. (10.1103/PhysRevB.67.205329)
    DOI : 10.1103/PhysRevB.67.205329
  • Time-domain interferometry for direct electric-field reconstruction by use of an acousto-optic programmable filter and a two-photon detector
    • Monmayrant Antoine
    • Joffre Manuel
    • Oksenhendler Thomas
    • Herzog R.
    • Kaplan D.
    • Tournois Pierre
    Optics Letters, Optical Society of America - OSA Publishing , 2003, 28 (4), pp.278-280 . We introduce a new approach to the characterization of femtosecond optical pulses based on a remarkably simple setup combining a two-photon detector and a pulse shaper consisting of a longitudinal acousto-optic programmable filter. The operation of this setup is demonstrated through the use of a new version of spectral phase interferometry for direct electric-field reconstruction based on time-domain instead of on frequency-domain interferometry. Cop. 2003 Optical Society of America (10.1364/OL.28.000278)
    DOI : 10.1364/OL.28.000278
  • Ligand binding dynamics to the heme domain of the oxygen sensor Dos from Escherichia coli
    • Liebl Ursula
    • Bouzhir-Sima Latifa
    • Kiger Laurent
    • Marden M.C.
    • Lambry Jean-Christophe
    • Négrerie Michel
    • Vos Marten H.
    Biochemistry, American Chemical Society , 2003, 42 (21), pp.6527 . In the heme-based oxygen sensor Dos from Escherichia coli, one of the axial ligands (Met 95) of a six-coordinate heme can be replaced by external ligands such as O2, NO, and CO, which causes a switch in phosphodiesterase activity. To gain insight into the bidirectional switching mechanism, we have studied the interaction of ligands with the sensor domain DosH by flash photolysis experiments with femtosecond time resolution. The internal ligand can be photodissociated from the ferrous heme and recombines with time constants of 7 and 35 ps. This is somewhat slower than recombination of the external ligands NO, with which picosecond rebinding occurs with unprecedented efficiency (>99%) with a predominant phase of 5 ps, and O2 (97% in 5 ps, Liebl, U., Bouzhir-Sima, L., Négrerie, M., Martin, J.-L., and Vos, M. H. (2002) Proc. Natl. Acad. Sci. U.S.A. 99, 12771−12776). Dissociated CO displays geminate rebinding in 1.5 ns with a very high yield (60%). Together these results indicate that the heme environment provides a very tight pocket for external ligands, presumably preventing frequent switching events. Additional CO dissociation and rebinding experiments on a longer time scale reveal that (a) Met 95 binding, in 100 μs, occurs in competition with bimolecular CO binding, and (b) subsequent replacement of Met 95 by CO on the millisecond time scale occurs faster than in rapid-mixing experiments, suggesting a slow further relaxation. A minimal ligand binding model is proposed that suggests that Met 95 displacement from the heme is facilitated by the presence of an external ligand in the heme environment. Furthermore, the orders of magnitude difference between Met 95 binding after dissociation of internal and external ligands, as well as the spectral characteristics of photodissociation intermediates, indicate substantial rearrangement of the heme environment associated with ligand sensing. Further remarkable observations include evidence for stable (>4 ns) photooxidation of six-coordinate ferrous heme, with a quantum yield of 4−8%. (10.1021/bi027359f)
    DOI : 10.1021/bi027359f
  • Ionic mechanisms involved in the nodal swelling of myelinated axons caused by marine toxins
    • Mattei César
    • Benoit Evelyne
    • Mattei Cesar
    • Ouanounou Gilles
    • Meunier Frederic A
    • Suput Dusan
    • Gall Frederic Le
    • Marquais Michel
    • Dechraoui Marie Y
    • Molgo Jordi
    • Benoit Evelyne
    • Mattei Cesar
    • Ouanounou Gilles
    • Meunier Frederic A
    • Suput Dusan
    • Gall Frederic Le
    • Marquais Michel
    • Dechraoui Marie Y
    • Molgo Jordi
    • Benoit Evelyne
    • Mattei Cesar
    • Ouanounou Gilles
    • Meunier Frederic A
    • Suput Dusan
    • Gall Frederic Le
    • Marquais Michel
    • Dechraoui Marie Y
    • Molgo Jordi
    Cellular and Molecular Biology Letters, Springer Verlag (Germany) , 2002 . This review describes the ionic mechanisms involved in the nodal swelling of frog myelinated axons caused by specific marine neurotoxins (ciguatoxins, brevetoxins, Conus consors toxin and equinatoxin-II), analysed using confocal laser scanning microscopy. We have focussed on toxins that either target neuronal voltage-dependent Na+ channels, or that form cation-selective pores and indirectly affect the functioning of the Na(+)-Ca(++)exchanger.
  • Does lindane (gamma-hexachlorocyclohexane) increase the rapid delayed rectifier outward K+ current (IKr) in frog atrial myocytes?
    • Sauviat Martin-Pierre
    • Colas Anthony
    • Pages Nicole
    BMC Pharmacology, BioMed Central , 2002, 2, pp.15 . BACKGROUND: The effects of lindane, a gamma-isomer of hexachlorocyclohexane, were studied on transmembrane potentials and currents of frog atrial heart muscle using intracellular microelectrodes and the whole cell voltage-clamp technique. RESULTS: Lindane (0.34 microM to 6.8 microM) dose-dependently shortened the action potential duration (APD). Under voltage-clamp conditions, lindane (1.7 microM) increased the amplitude of the outward current (Iout) which developed in Ringer solution containing TTX (0.6 microM), Cd2+ (1 mM) and TEA (10 mM). The lindane-increased Iout was not sensitive to Sr2+ (5 mM). It was blocked by subsequent addition of quinidine (0.5 mM) or E-4031 (1 microM). E-4031 lengthened the APD; it prevented or blocked the lindane-induced APD shortening. CONCLUSIONS: In conclusion, our data revealed that lindane increased the quinidine and E-4031-sensitive rapid delayed outward K+ current which contributed to the AP repolarization in frog atrial muscle.
  • Interactions between heme d and heme b(595) in quinol oxidase bd from Escherichia coli: A photoselection study using femtosecond spectroscopy
    • Borisov Vitaly
    • Liebl Ursula
    • Rappaport F.
    • Martin Jean-Louis
    • Zhang Jie
    • Gennis Robert
    • Konstantinov Alexander
    • Vos Marten H.
    Biochemistry, American Chemical Society , 2002, 41 (5), pp.1654 . Femtosecond spectroscopy was performed on CO-liganded (fully reduced and mixed-valence states) and O-2-liganded quinol oxidase bd from Escherichia coli. Substantial polarization effects, unprecedented for optical studies of heme proteins, were observed in the CO photodissociation spectra, implying interactions between heme d (the chlorin ligand binding site) and the close-lying heme b(595) on the picosecond time scale; this general result is fully consistent with previous work [Vos, M. H., Borisov, V. B., Liebl, U., Martin, J.-L., and Konstantinov, A. A. (2000) Proc. Natl. Acad. Sci. U.S.A. 97, 15541559]. Analysis of the data obtained under isotropic and anisotropic polarization conditions and additional flash photolysis nanosecond experiments on a mutant of cytochrome bd mostly lacking heme b595 allow to attribute the features in the well-known but unusual CO dissociation spectrum of cytochrome bd to individual heme d and heme b595 transitions. This renders it possible to compare the spectra of CO dissociation from reduced and mixed-valence cytochrome bd under static conditions and on a picosecond time scale in much more detail than previously possible. CO binding/dissociation from heme d is shown to perturb ferrous heme b595, causing induction/loss of an absorption band centered at similar to435 nm. In addition, the CO photodissociation-induced absorption changes at 50 ps reveal a bathochromic shift of ferrous heme b595 relative to the static spectrum. No evidence for transient binding of CO to heme b595 after dissociation from heme d is found in the picosecond time range. The yield of CO photodissociation from heme d on a time scale of INFERIEUR 15 ps is found to be diminished more than 3-fold when heme b(595) is oxidized rather than reduced. In contrast to other known heme proteins, molecular oxygen cannot be photodissociated from the mixed-valence cytochrome bd at all, indicating a unique structural and electronic configuration of the diheme active site in the enzyme. (10.1021/bi0158019)
    DOI : 10.1021/bi0158019
  • Picosecond dynamics and mechanisms of photoexcited Cu(II)-5,10,15,20-meso-tetrakis(4-N-methylpyridyl)porphyrin quenching by oxygen-containing Lewis-base solvents
    • Chirvony V.
    • Martin Jean-Louis
    • Négrerie Michel
    • Turpin P.-Y.
    Journal of Physical Chemistry A, American Chemical Society , 2002, 106 (24), pp.5760 . Deactivation of the lowest excited triplet (pi,pi*) state, (3)(pi,pi*), of the cationic water-soluble Cu(II)-5,10,15,20-meso-tetrakis(4-N-methylpyridyl)porphyrin (CuTMpyP4) was studied by femtosecond transient absorption spectroscopy in three oxygen-containing solvents (Lewis bases) of various polarity, water, methanol, and dimethyl sulfoxide (DMSO). In all of these solvents, the (3)(pi,pi*) state depopulation follows biexponential kinetics. A majority of the (3)(pi,pi*) state population (similar to80%) deactivates very quickly with a time constant of about 1-2 ps to give rise to formation of an exciplex (CuTMpyP4)*-L between the porphyrin in its excited (d,d) state and a solvent molecule, L, the latter playing the role of porphyrin axial ligand. The exciplex lifetime is found to depend on the solvent dielectric constant E and increases from 7 ps in water (epsilon = 78.3) to 27 ps in methanol (epsilon = 32.7), through 23 ps in DMSO (epsilon = 46.5). A minor part of the initial (3)(pi,pi*) state population (similar to20%) deactivates to the ground state, without any detectable intermediate, with time constants of 25, 8, and 11 ps in water, DMSO, and methanol, respectively. These rather fast pathways (picosecond time scale) of excitation deactivation to the ground state are interpreted in terms of quenching influence of some low-lying intramolecular charge-transfer states that belong to four- and five-coordinate CuTMpyP4. A partitioning mechanism of (3)(pi,pi*) state CuTMpyP4 molecules into two populations decaying by different paths, that is, through exciplex formation and "directly" to the ground state, is proposed. (10.1021/jp0134998)
    DOI : 10.1021/jp0134998
  • Wavelength dependence of nonlinear circular dichroism in a chiral ruthenium-tris(bipyridyl) solution
    • Mesnil H.
    • Schanne-Klein Marie-Claire
    • Hache François
    • Alexandre M.
    • Lemercier G.
    • Andraud Chantal
    Physical Review A : Atomic, molecular, and optical physics [1990-2015], American Physical Society , 2002, 66 (1), pp.138021 . Nonlinear circular dichroism is studied in a solution of ruthenium-tris(bipyridyl) salt in one-beam and pump-probe experiments by tuning the laser wavelength across the circular dichroism structure. The dispersion of the nonlinear circular dichroism is measured. This wavelength dependence is well accounted for by a model calculation where nonlocality is included in the optical response of a two-coupled-oscillator system. This calculation also allows us to address the question of the contribution of electric quadrupolarization to the nonlinear optical activity of an isotropic liquid of chiral molecules. © 2002 The American Physical Society (10.1103/PhysRevA.66.013802)
    DOI : 10.1103/PhysRevA.66.013802
  • Coherent infrared emission from myoglobin crystals: An electric field measurement
    • Groot Marie-Louise
    • Vos Marten H.
    • Schlichting I.
    • van Mourik F.
    • Joffre Manuel
    • Lambry Jean-Christophe
    • Martin Jean-Louis
    Proceedings of the National Academy of Sciences of the United States of America, National Academy of Sciences , 2002, 99 (3), pp.1323 . We introduce coherent infrared emission interferometry as a X(2) vibrational spectroscopy technique and apply it to studying the initial dynamics upon photoactivation of myoglobin (Mb). By impulsive excitation (using 11-fs pulses) of a Mb crystal, vibrations that couple to the optical excitation are set in motion coherently. Because of the order in the crystal lattice the coherent oscillations of the different proteins in the crystal that are associated with charge motions give rise to a macroscopic burst of directional multi-teraHertz radiation. This radiation can be detected in a phase-sensitive way by heterodyning with a broad-band reference field. In this way both amplitude and phase of the different vibrations can be obtained. We detected radiation in the 1,000-1,500 cm-1 frequency region, which contains modes sensitive to the structure of the heme macrocycle, as well as peripheral protein modes. Both in carbonmonoxy-Mb and aquomet-Mb we observed emission from six modes, which were assigned to heme vibrations. The phase factors of the modes contributing to the protein electric field show a remarkable consistency, taking on values that indicate that the dipoles are created "emitting" at t = 0, as one would expect for impulsively activated modes. The few deviations from this behavior in Mb-CO we propose are the result of these modes being sensitive to the photodissociation process and severely disrupted by it. (10.1073/pnas.251662698)
    DOI : 10.1073/pnas.251662698
  • Carbon nanotubes for optical limiting
    • Vivien L.
    • Lançon P.
    • Riehl D.
    • Hache François
    • Anglaret E.
    Carbon, Elsevier , 2002, 40 (10), pp.1789-1797 . This paper reviews the optical limiting properties of carbon nanotubes. The nonlinear optical properties of nanotubes were investigated in water and in chloroform suspensions. Nonlinear transmittance measurements were reported for various pulse durations and wavelengths and show that carbon nanotubes are good candidates for effective optical limiting over broad temporal and laser energy ranges. Z-Scans and pump-probe time-resolved experiments were achieved to identify the origin of optical limiting in nanotubes. The main phenomenon is a strong nonlinear scattering, originating from solvent vapour bubble growth and sublimation of nanotubes at high fluences. Heat transfer from particles to solvent is particularly effective as compared to carbon black suspensions because of the large surface area of the carbon nanotubes. (10.1016/S0008-6223(02)00046-5)
    DOI : 10.1016/S0008-6223(02)00046-5
  • Optical limiting properties of carbon nanotubes
    • Vivien L.
    • Riehl D.
    • Hache François
    • Anglaret E.
    Physica B: Condensed Matter, Elsevier , 2002, 323 (1-4), pp.233-234 . We review a series of investigations on nonlinear optical properties of carbon nanotube suspensions for optical limiting application. Z-scan, pump-probe, and shadowgraphics experiments allowed us to study the mechanism responsible for optical limiting. The main effect is nonlinear scattering, which is due to heat transfer from particles to solvent, leading to solvent bubble formation and to sublimation of carbon nanotubes. (10.1016/S0921-4526(02)00974-2)
    DOI : 10.1016/S0921-4526(02)00974-2
  • Muscarinic effects of the Caribbean ciguatoxin C-CTX-1 on frog atrial heart muscle
    • Sauviat Martin-Pierre
    • Marquais Michel
    • Vernoux Jean-Paul
    Toxicon, Elsevier , 2002, 40 (8), pp.1155 . The effects of Caribbean ciguatoxin (C-CTX-1) isolated from horse-eye jack (Caranx latus) on the electrical and mechanical activities of frog auricle were studied. C-CTX-1 (1pM-50nM) dose-dependently shortened the duration of the plateau and the repolarizing phase of the action potential (AP). The AP shortening induced by C-CTX-1 (50nM) was suppressed or prevented either by tetrodotoxin (TTX; 0.6nM) or by atropine (0.1mM). C-CTX-1 (50nM) prolonged the TTX (0.6nM)-sensitive electrical response of the vagus nerve branches, which innervate the auricle. The C-CTX-1 (50nM)-induced shortening of the plateau and of the repolarization phase were prevented or reversed by gallamine (20µM) and pirenzepine (0.5µM), respectively. C-CTX-1 (50nM) decreased the amplitude of the peak contraction and shortened its duration. In the presence of gallamine (20µM), C-CTX-1 decreased the amplitude of the peak contraction and shortened its duration in the presence of pirenzepine (0.5µM). C-CTX-1 (50nM) decreased the time constant of the relaxation phase of the peak contraction suggesting that it increased the Na+/Ca2+ exchange activity. Acetylcholine (ACh; 1pM) shortened APD, decreased the peak contraction and mimics the effects of C-CTX-1. In conclusion, the presented data show that C-CTX-1 released ACh from atrial cholinergic nerve terminals which activated M1 and M2 muscarinic receptors subtype (mAChR). Our findings suggest that M1 and M2 mAChR are present in frog atrial tissue and play a previously unrecognized role in the modulation of the AP duration and of the mechanical activity of cardiac tissue. Cop. 2002 Elsevier Science Ltd. All rights reserved. (10.1016/S0041-0101(02)00117-4)
    DOI : 10.1016/S0041-0101(02)00117-4
  • Spectroscopie non-linéaire femtoseconde cohérente à deux dimensions spectrales [Coherent femtosecond nonlinear spectroscopy with two spectral dimensions]
    • Belabas Nadia
    • Joffre Manuel
    Journal de Physique IV Proceedings, EDP Sciences , 2002, 12 (5), pp.393-395 . La spectroscopie non-linéaire femtoseconde cohérente multidimensionnelle est une technique optique analogue à la résonance magnétique nucléaire multidimensionnelle. Elle repose sur l'utilisation d'impulsions femtosecondes et est démontrée ici dans le cas d'un processus de génération d'infrarouge par différence de fréquence dans une cristal non-linéaire avec accord de phase. Dans le domaine de l'infrarouge moyen, elle permet notamment la spectroscopie vibrationnelle de molécules et l'étude de nanostructures semiconductrices. (10.1051/jp4:20020205)
    DOI : 10.1051/jp4:20020205
  • Coupling between molecular rotations and OH***O motions in liquid water: Theory and experiment
    • Gallot Guilhem
    • Bratos S.
    • Pommeret S.
    • Lascoux Noëlle
    • Leicknam J.-Cl.
    • Kozinski M.
    • Amir W.
    • Gale Geoffrey
    The Journal of Chemical Physics, American Institute of Physics , 2002, 117 (24), pp.11301 . A new theory is proposed to describe spectral effects of the coupling between molecular rotations and OH⋯O motions in liquid water. The correlation function approach is employed together with a special type of development in which the coupling energy of these two motions is the expansion parameter. The isotropy of the liquid medium plays an essential role in this study. Based on this theory, a new infrared pump-probe experiment is described permitting a visualization of molecular rotations at subpicosecond time scales. Full curves relating the mean squared rotational angle and time, and not only the rotational relaxation time, are measured by this experiment. However, very short times where the incident pulses overlap must be avoided in this analysis. The lifetime of OH⋯O bonds in water is rotation-limited. © 2002 American Institute of Physics. (10.1063/1.1522378)
    DOI : 10.1063/1.1522378
  • Eau liquide : le film" à l'échelle femtoseconde
    • Gallot Guilhem
    • Bratos S.
    • Gale Geoffrey
    • Lascoux Noëlle
    • Leicknam J.-Cl.
    • Pommeret S.
    • Amir Wafa
    Bulletin de la Societe Francaise de Physique , 2002, 134 (1), pp.8 . L'eau est de loin le liquide le plus important sur terre. Il est présent à tous les échelons de l'écosystème terrestre, des océans qui couvrent les 3/5 de la surface, au corps humain dont il représente 70% du volume. Sans l'eau, les systèmes biologiques ne fonctionneraient pas et la vie telle que nous la connaissons n'existerait pas. Si l'eau joue un rôle aussi fondamental dans la nature [1], c'est grâce à ses propriétés exceptionnelles qui proviennent essentiellement de la liaison hydrogène [2, 3]. Dans ces conditions, il n'est pas surprenant que D'immenses efforts aient été portés par le passé, efforts qui continuent de nos jours, pour mieux comprendre ce liquide si particulier. Ses propriétés mécaniques, physicochimiques et moléculaires ont ainsi été étudiées en détails et ont été soigneusement décrites dans un grand nombre d'ouvrages [4, 5]. L'arrivée au début des années 90 de lasers délivrant des impulsions pico- puis femtoseconde va cependant bouleverser la situation en ouvrant la voie à la femtochimie de l'eau liquide. Grâce à ces impulsions incroyablement brèves, la dynamique moléculaire de l'eau peut maintenant être étudiée. Il est même possible de " filmer " les mouvements des molécules d'eau et de la liaison hydrogène en temps réel. C'est ce thème qUE NOUS ALLONS MAINTENANT TRAITER.
  • Influence of the hole population on the transient reflectivity signal of annealed low-temperature-grown GaAs
    • Ortiz Valentin
    • Nagle J.
    • Alexandrou Antigoni
    Applied Physics Letters, American Institute of Physics , 2002, 80 (14), pp.2505 . We study the influence of the carrier dynamics on the transient reflectivity of low-temperature-grown GaAs samples. We report a precise modeling of the recorded reflectivity data, which exhibit multiexponential decays and changes in sign, using a standard point defect model and taking into account the effects of the band filling, band gap renormalization, and trap absorption. We show that the valence-band hole population plays an important role in the behavior of the signals, and that it must be taken into account in order to optimize low-temperature-grown GaAs-based devices. Cop. 2002 American Institute of Physics. (10.1063/1.1463209)
    DOI : 10.1063/1.1463209
  • Cardiotoxicité du lindane, un isomère gamma de l'hexachlorocyclohexane [Cardiotoxicity of lindane, a gamma isomer of hexachlorocyclohexane ]
    • Sauviat Martin-Pierre
    • Pages Nicole
    Journal de la Société de Biologie , 2002, 196 (4), pp.339 . The goal of the present review is to collect information concerning membrane effects induced by lindane intoxication, a y isomer of hexachiorocyclohexane (gamma-HCH) that has been largely used as an insecticide and disinfectant in agriculture and entered also in the composition of some lotions, creams and shampoos used against parasites (lice and scabies). Absorbed through respiratory, digestive or transcutaneous pathways, lindane accumulates within lipid rich tissues. Lindane accumulation depends on the duration of the exposure and affects tissues in the following order: adipose tissues > brain > kidney > muscle > lungs > heart > liver > blood. Whatever the mode of lindane absorption, it accumulates in blood and is distributed throughout the body. It may affect human health by exerting systemic, immunologic, teratogenic, and/or cancerogenic effects. The symptoms of lindane intoxication are different according to the mode of intoxication, acute or chronic. The absorption of high doses of gamma-HCH is particularly toxic for the central nervous system and for the female and male reproduction apparatus in mammals where lindane is considered as an endocrine disruptor. Lindane is highly lipophilic and incorporates into biological membranes according to the following sequence: mitochondria > sarcoplasmic reticulum > myelin > brain microsomes > erythrocytes. Lindane exerts a stimulating action on synaptic transmission and inhibits the chloride current activated by gamma-amino butyric acid (GABA) of many muscular and nervous preparations by interacting with the receptors GABA-chloride channel complex. It seems to affect calcium homeostasis of many tissues. The similarity between lindane and inositol (1, 4, 5) phosphate (IP3) suggested that lindane releases Ca2+ from IP3-sensitive intracellular stores in macrophages and myometrial cells. Ca2+ release from reticulum endoplasmic, mitochondria and other Ca2+ stores has been reported in cat kidney cells. Lindane altered energetic metabolism of hepatic mitochondria and the inositol-phosphate synthesis in neuronal cells. However, lindane does not compete with the IP3 receptor. Lindane produces a Ca2+ influx in mice peritoneal macrophage cells responsible for the Ca2+ induced Ca2+ release produced by phospholipase C via IP3 pathway and resulting in a maintained increase of the free cytosolic Ca2+ concentration. Lindane decreased the membrane erythrocyte and cerebral cell concentration of phosphatidyl inositol PI, PIP and PIP2 in rats repetitively exposed to lindane for 3 or 6 months. Lindane induces oxidative stress; it modifies the activity of the scavenger enzymes. This effect is involved in the inhibition of intercellular gap junctions. Modifications of the electrocardiogram (ECG), sinusal rhythm alteration and negative and dysphasic variations of T wave, similar to those produced by hyperkaliemia, have been reported after lindane absorption. During acute lindane poisoning, the activities of serum transaminases (SGOT, SGTP), and lactate deshydrogenase (LDH) increase. Lindane produces histological alterations of cardiac tissues and a cardio-vascular dystrophy (contracture, degenerescence and necrosis) mainly in the left ventricular wall and a hypertrophy of the left ventricle. Chronic application of residual doses of lindane shortened the action potential duration in rat papillary muscle. These effects were similar to those induced by hyperthyroidism. Lindane increases the triiodothyronine (T3) serum level in hyperthyroid rats. T3 plays an important role in the postnatal development of the rat ventricle by increasing the density of potassium channels which contribute to action potential shortening during the development. Thyroid hormones influence the regulation and the expression of messengers ARN which encode different potassium channels involved in action potential repolarization (Kvl.2; Kvl.4; Kvl.5; Kv2.1; Kv4; HCN2). The thyrotropine-releasing hormone (TRH) modulates the HERG-type rapid delayed potassium channel (IKr) encoded by the human gene ether-a-go-go in rat anterior pituitary cells GH3/B6. This channel is involved in the cardiac long QT syndrome. TRH modifies the current kinetics of human HERG potassium channel co-expressed in Xenopus oocytes with the TRH receptor, whose activity is modulated via the protein kinase C pathway linked to a G protein-coupled receptor and is regulated by changes in the PIP2 concentration in the membrane. IKr channels regulation is also dependent on sexual hormones. In conclusion, lindane affects the excitable membranes and the cardio circulatory system. These alterations (may) represent a potential risk for human health.
  • Shadowgraphic imaging of carbon nanotube suspensions in water and in chloroform
    • Vivien L.
    • Moreau J.
    • Riehl D.
    • Alloncle P.A.
    • Autric M.
    • Hache François
    • Anglaret E.
    Journal of the Optical Society of America B, Optical Society of America , 2002, 19 (11), pp.2665 . Carbon nanotube suspensions are known to display interesting optical limiting properties as a result of the formation of solvent or carbon-vapor bubbles that scatter the laser beam. In this study we present an original experiment that permits direct observation of the changes that occur in the focal zone in carbon nanotube suspensions by using a shadowgraphic experiment coupled with a monochromatic pump-probe experiment. We have observed a clear correlation between the radius of the scattering centers and the evolution in transmittance of the sample. We compared bubble growth in chloroform and water and found good agreement with previously obtained results. We also observed the presence of compression waves, which propagate parallel to the laser beam and can produce secondary cavitation phenomena after reflection on the cell walls. Cop. 2002 Optical Society of America. (10.1364/JOSAB.19.002665)
    DOI : 10.1364/JOSAB.19.002665
  • Visible-infrared two-dimensional Fourier-transform spectroscopy
    • Belabas Nadia
    • Joffre Manuel
    Optics Letters, Optical Society of America - OSA Publishing , 2002, 27 (22), pp.2043 . We report on a new class of optical multidimensional Fourier-transform spectroscopy associated with a visible excitation-infrared emission configuration, in which the emitted field results from second-order optical nonlinearities. This configuration is demonstrated on a phase-matched sample of known nonlinear response by coherent measurement of the mid-infrared field emitted after a femtosecond visible double-pulse excitation. (C) 2002 Optical Society of America. (10.1364/OL.27.002043)
    DOI : 10.1364/OL.27.002043
  • Nitric oxide (NO) traffic in endothelial NO synthase. Evidence for a new NO binding site dependent on tetrahydrobiopterin?
    • Slama-Schwok Anny
    • Négrerie Michel
    • Berka V.
    • Lambry Jean-Christophe
    • Tsai Ah-Lim
    • Vos Marten H.
    • Martin Jean-Louis
    Journal of Biological Chemistry, American Society for Biochemistry and Molecular Biology , 2002, 277 (9), pp.7581 . Nitric oxide (NO) traffic within the reduced ferrous-nitrosyl complex of endothelial nitric-oxide synthase (eNOS) has been studied by ultrafast time-resolved absorption spectroscopy. In the presence of tetrahydrobiopterin, the rate of NO rebinding to the heme upon photodissociation depends on the NO concentration. The time scale of this process, picoseconds to nanoseconds, precludes a diffusion from the solution toward the protein medium, and altogether the data point at a new NO binding site within the protein. Comparison of the kinetics of pterin-bound and -depleted eNOS points out that the existence of this new site depends on the presence of tetrahydrobiopterin. The new non-heme site may act as a "doorstep" to the heme pocket and control NO escape from eNOS. (10.1074/jbc.M108657200)
    DOI : 10.1074/jbc.M108657200
  • Strong chiroptical effects in surface second harmonic generation obtained for molecules exhibiting excitonic coupling chirality
    • Schanne-Klein Marie-Claire
    • Boulesteix T.
    • Hache François
    • Alexandre M.
    • Lemercier G.
    • Andraud Chantal
    Chemical Physics Letters, Elsevier , 2002, 362 (1-2), pp.103 . We measured nonlinear optical activity in second harmonic generation (SHG) by reflection on a thin film of chiral molecules. We selected the structure of our molecules in order to obtain very large chiroptical effects. We indeed measured an angle of rotation of the second harmonic polarization as large as 66° for an acridine substituted Tröger base. This is in good agreement with our theoretical expectations for such an excitonic coupling chirality. Cop. 2002 Elsevier Science B.V. All rights reserved. (10.1016/S0009-2614(02)01030-8)
    DOI : 10.1016/S0009-2614(02)01030-8
  • Nonlinear optical activity in chiral molecules: Surface second harmonic generation and nonlinear circular dichroism
    • Hache François
    • Schanne-Klein Marie-Claire
    • Mesnil Hugues
    • Alexandre M.
    • Lemercier G.
    • Andraud Chantal
    Comptes Rendus. Physique, Académie des sciences (Paris) , 2002, 3 (4), pp.429 . Nonlinear optical activity in chiral molecules is investigated. We first examine the importance of the nonlocality of the light-matter interaction in optical activity and extend this concept to second-order (surface second harmonic generation) and third-order (nonlinear circular dichroism) nonlinear optical phenomena. Microscopic models are also discussed. Various phenomena derived from these considerations are demonstrated experimentally with specially-synthesized chiral molecules. Cop. 2002 Académie des sciences/Éditions scientifiques et médicales Elsevier SAS. (10.1016/S1631-0705(02)01327-0)
    DOI : 10.1016/S1631-0705(02)01327-0
  • Rotation moléculaire en temps réel dans l'eau liquide [Real-time molecular rotation in water]
    • Amir W.
    • Lascoux Noëlle
    • Gallot Guilhem
    • Gale Geoffrey
    • Pommeret S.
    • Leicknam J.-Ci.
    • Bratos S.
    Journal de Physique IV Proceedings, EDP Sciences , 2002, 12 (5), pp.381 . La connaissance déjà acquise sur la dynamique de la liaison hydrogène dans l'eau liquide grâce au développement de laser délivrant des impulsions ultra-courtes dans l'infrarouge moyen nous permet de filmer la rotation de molécules HDO dans une solution D2O. L'expérience réalisée au laboratoire est basée sur la technique de spectroscopie pompe sonde résolue en polarisation. L'anisotropie mesurée permet de détecter en temps réel l'angle de déflexion du moment dipolaire de transition dont le point de départ est la direction du faisceau laser de pompe. (10.1051/jp420020200)
    DOI : 10.1051/jp420020200