Sorry, you need to enable JavaScript to visit this website.
Laboratoire d'optique et biosciences
Recherchez dans le site
Tutelle https://www.cnrs.fr/fr Tutelle https://www.polytechnique.edu/ Tutelle https://www.inserm.fr/
Partager

Articles

  • Photodissociation of heme distal methionine in ferrous cytochrome c revealed by subpicosecond time-resolved resonance raman spectroscopy
    • Cianetti Simona
    • Négrerie Michel
    • Vos Marten H.
    • Martin Jean-Louis
    • Kruglik Sergei G.
    Journal of the American Chemical Society, American Chemical Society , 2004, 126 (43), pp.13932 . Cytochrome c (cyt c) is anelectron-transfer heme protein that also binds nitric oxide (NO). In resting cyt c, two endogenous ligands of the heme iron are histidine-18 (His) and methionine-80 (Met) side chains, and NO binding requires the cleavage of one of the axial bonds. Previous femtosecond transient absorption studies suggested the photolysis of either Fe-His or Fe-Met bonds. We aimed at unequivocally identifying the internal side chain that is photodissociated in ferrous cyt c and at monitoring heme structural dynamics, by means of time-resolved resonance Raman (TR3) spectroscopy with ~0.6 ps time resolution. The Fe-His stretching mode at 216 cm-1 has been observed in photoproduct TR3 spectra for the first time for a c-type heme. The same transient mode was observed for a model ferrous cyt c N-fragment (residues 1-56) ligated with two His in the resting state. Our TR3 data reveal that upon ferrous cyt c photoexcitation, (i) distal Met side chain is instantly released, producing a five-coordinated domed heme structure, (ii) proximal His side chain, coupled to the heme, exhibits distortion due to strain exerted by the protein, and (iii) alteration in heme-cysteine coupling takes place along with the relaxation of the protein-induced deformations of the heme macrocycle. Copyright 2004 American Chemical Society. (10.1021/ja046442i)
    DOI : 10.1021/ja046442i
  • Functional evidence for active site location of tetrameric thymidylate synthase X at the interphase of three monomers
    • Leduc Damien
    • Graziani Sébastien
    • Lipowski Gérard
    • Marchand C.
    • Le Maréchal P.
    • Liebl Ursula
    • Myllykallio Hannu
    Proceedings of the National Academy of Sciences of the United States of America, National Academy of Sciences , 2004, 101 (19), pp.7252-7257 . Little is known about the catalytic mechanism of the recently discovered ThyX family of flavin-dependent thymidylate synthases that are required for thymidylate (deoxythymidine 5'-monophosphate) synthesis in a large number of microbial species. Using a combination of site-directed mutagenesis and biochemical measurements, we have identified several residues of the Helicobacter pylori ThyX protein with crucial roles in ThyX catalysis. By providing functional evidence that the active site(s) of homotetrameric ThyX proteins is formed by three different subunits, our findings suggest that ThyX proteins have evolved through multimerization of inactive monomers. Moreover, because the active-site configurations of ThyX proteins, present in many human pathogenic bacteria, and of human thymidylate synthase ThyA are different, our results will aid in the identification of compounds specifically inhibiting microbial growth. (10.1073/pnas.0401365101)
    DOI : 10.1073/pnas.0401365101
  • Dynamic regulation of the inducible nitric-oxide synthase by NO - Comparison with the endothelial isoform
    • Gautier Clément
    • Négrerie Michel
    • Wang Zq
    • Lambry Jean-Christophe
    • Stuehr Dennis
    • Collin Fabrice
    • Martin Jean-Louis
    • Slama-Schwok Anny
    Journal of Biological Chemistry, American Society for Biochemistry and Molecular Biology , 2004, 279 (6), pp.4358 . We studied by ultrafast time-resolved absorption spectroscopy the geminate recombination of NO to the oxygenase domain of the inducible NO synthase, iNOSoxy, and to mutated proteins at position Trp-457. This tryptophan interacts with the tetrahydrobiopterin cofactor BH4, and W457A/F mutations largely reduced the catalytic formation of NO. BH4 decreases the rate of NO rebinding to the ferric iNOSoxy compared with that measured in its absence. The pterin has a larger effect on W457A/F than on the WT protein by increasing NO release from the protein. Therefore, BH4 raises the energy barrier for NO recombination to the mutated proteins in contrast with our observations on eNOS (SlamaSchwok, A., Negrerie, M., Berka, V., Lambry, J: C., Tsai, A.-L., Vos, M., and Martin, J.-L. (2002) J. Biol. Chem. 277, 7581-7586). Thus, we show a differential effect of BH4 on NO release from eNOS and iNOS. Compared with the position of this residue in the BH4-repleted enzyme, simulations of the NO dissociation dynamics point out at a swing of Trp-457 toward the missing pterin in the absence of BH4. NO geminate-rebinding data show a more efficient NO release from eNOS than from iNOS once NO is formed. Consistently, NO produced by iNOS is regulated by its ferric nitrosyl complex in contrast with eNOS. We show that the small enhancement of the NO geminate recombination rate in W457A/F compared with that in the WT enzyme cannot explain the decrease of NO yield because of the mutation; the major effect of the mutation thus arises from an uncoupled catalysis (Wang, Z. Q., Wei, C. C., Ghosh, S., Meade, A. L., Hemann, C., Hille, R., and Stuehr, D. J. (2001) Biochemistry 40, 12819-12825). (10.1074/jbc.M305048200)
    DOI : 10.1074/jbc.M305048200
  • Laser spectroscopic visualization of hydrogen bond motions in liquid water
    • Bratos S.
    • Leicknam J.-C.
    • Pommeret S.
    • Gallot Guilhem
    Journal of Molecular Structure, Elsevier , 2004, 708 (1-3), pp.197-203 . Ultrafast pump-probe experiments are described permitting a visualization of molecular motions in diluted HDO/D2O solutions. The experiments were realized in the mid-infrared spectral region with a time resolution of 150 fs. They were interpreted by a careful theoretical analysis, based on the correlation function approach of statistical mechanics. Combining experiment and theory, stretching motions of the OH?O bonds as well as HDO rotations were 'filmed' in real time. It was found that molecular rotations are the principal agent of hydrogen bond breaking and making in water. Recent literatures covering the subject, including molecular dynamics simulations, are reviewed in detail. Cop. 2004 Elsevier B.V. All rights reserved. (10.1016/j.molstruc.2004.06.036)
    DOI : 10.1016/j.molstruc.2004.06.036
  • Spectroscopie d'émission infrarouge femtoseconde des protéines photoréceptrices orientées
    • Colonna Anne
    • Lambry Jean-Christophe
    • Groma G.I.
    • Martin Jean-Louis
    • Vos Marten H.
    Journal de Physique IV Proceedings, EDP Sciences , 2004, 119, pp.161-162 . Ce travail a pour but l'étude de la dynamique primaire des protéines et de leur rôle dans la fonction du complexe protéique. La technique utilisée est une spectroscopie femtoseconde non linéaire ( $\chi ^{(2)}$) dans le domaine moyen infrarouge. L'ensemble des mouvements de charge induits par une excitation ultra-brève (~11fs) d'un échantillon de membranes orientées de bactériorhodopsine, un analogue bactérien de la protéine photoréceptrice du système visuel chez les mammifères, donne lieu à une émission directionnelle infrarouge (redressement optique). Les caractéristiques de cette émission (fréquence, phase, amplitude, direction) reflètent la réponse électronique et vibrationnelle de la molécule. (10.1051/jp4:2004119037)
    DOI : 10.1051/jp4:2004119037
  • Dynamique ultrarapide du proton dans l'eau : étude expérimentale
    • Amir Wafa
    • Gallot Guilhem
    • Hache François
    Journal de Physique IV Proceedings, EDP Sciences , 2004, 119, pp.111-112 . Nous présentons une étude de la dynamique femtoseconde du proton dans l'eau liquide par spectroscopie vibrationnelle femtoseconde résolue en temps. C'est à ce jour la première observation expérimentale d'une forme limite du proton en solution, et une première étape vers la compréhension du mécanisme de Grotthuss. (10.1051/jp4:2004119015)
    DOI : 10.1051/jp4:2004119015
  • Spectroscopy of electronic states in InAs quantum dots grown on In(x)Al(1-x)As/InP(001)
    • Fossard F.
    • Helman A.
    • Fishman G.
    • H Julien F.
    • Brault J.
    • Gendry M.
    • Peronne Emmanuel
    • Alexandrou Antigoni
    • E Schacham S.
    • Bahir G.
    • Finkman E.
    Physical Review Letters, American Physical Society , 2004, 69, pp.155333 . We have investigated optical properties of high-density InAs self-assembled quantum dots (QDs) in an InxAl1-xAs matrix, lattice matched to an InP (001) substrate. The weak lattice mismatch (~3%) results in a 90% coverage of the InxAl1-xAs surface with InAs QDs. By means of interband and intraband spectroscopies crossed with atomic force microscopy (AFM) measurements, we have determined that the InAs QDs optical properties depend on the deposited amount of InAs. Photoinduced absorption spectroscopy has been used to investigate midinfrared intraband absorptions. For three monolayers (ML) InAs deposit thickness, just above two-dimensional (2D)/3D growth mode transition (2.5 ML), the islands form as isolated elliptical dots elongated along the [10] direction and exhibit intraband resonances polarized either along the [110] or the [10] direction. For thicker deposition (>3 ML), InAs islands form chains of elliptical dots along the [10] direction where the quantum confinement is lost, resulting in a quantum-wire-like behavior. In this paper, we also report on photoluminescence and photocurrent spectroscopies, in order to get insight into the InAs/InxAl1-xAs island band structure. These experimental results are in good agreement with that of a multiband k*p model. (10.1103/PhysRevB.69.155333)
    DOI : 10.1103/PhysRevB.69.155333
  • Dissection of the triple tryptophan electron transfer chain in Escherichial coli DNA photolyase: Trp382 is the primary donor in photoactivation
    • Byrdin Martin
    • Eker André
    • Vos Marten H.
    • Brettel Klaus
    Proceedings of the National Academy of Sciences of the United States of America, National Academy of Sciences , 2003, 100 (15), pp.8676 . In Escherichia coli photolyase, excitation of the FAD cofactor in its semireduced radical state (FADH*) induces an electron transfer over ≈15 Å from tryptophan W306 to the flavin. It has been suggested that two additional tryptophans are involved in an electron transfer chain FADH* ← W382 ← W359 ← W306. To test this hypothesis, we have mutated W382 into redox inert phenylalanine. Ultrafast transient absorption studies showed that, in WT photolyase, excited FADH* decayed with a time constant τ ≈ 26 ps to fully reduced flavin and a tryptophan cation radical. In W382F mutant photolyase, the excited flavin was much longer lived (τ ≈ 80 ps), and no significant amount of product was detected. We conclude that, in WT photolyase, excited FADH* is quenched by electron transfer from W382. On a millisecond scale, a product state with extremely low yield (≈0.5% of WT) was detected in W382F mutant photolyase. Its spectral and kinetic features were similar to the fully reduced flavin/neutral tryptophan radical state in WT photolyase. We suggest that, in W382F mutant photolyase, excited FADH* is reduced by W359 at a rate that competes only poorly with the intrinsic decay of excited FADH* (τ ≈ 80 ps), explaining the low product yield. Subsequently, the W359 cation radical is reduced by W306. The rate constants of electron transfer from W382 to excited FADH* in WT and from W359 to excited FADH* in W382F mutant photolyase were estimated and related to the donor-acceptor distances. (10.1073/pnas.1531645100)
    DOI : 10.1073/pnas.1531645100
  • Picosecond Dynamics of a Peptide from the Acetylcholine Receptor Interacting with a Neurotoxin Probed by Tailored Tryptophan Fluorescence
    • Chowdhury P.
    • Gondry Muriel
    • Genet Roger
    • Martin Jean-Louis
    • Ménez André
    • Négrerie Michel
    • Petrich Jacob
    Photochemistry and Photobiology, Blackwell Wiley [1962-....] , 2003, 77 (2), pp.151 . A tryptophan analog, dehydro-N-acetyl-l-tryptophanamide (Δ-NATA), which is produced enzymatically vial-tryptophan 2′,3′-oxidase from Chromobacterium violaceum, is newly used for time-resolved fluorescence. The absorption and emission maxima of Δ-NATA at 332 and 417 nm, respectively, in 20% dimethylformamide-water are significantly shifted to the red with respect to those of tryptophan in water, permitting us to measure its fluorescence in the presence of tryptophan residues. We demonstrate that the steady-state spectra and the fluorescence decay of Δ-NATA are very sensitive to environment, changing dramatically with solvent as the chromophore is localized within a protein and when this tagged protein binds to a peptide. The tryptophan oxidase was also used to modify the single Trp of a neurotoxin from snake (Naja nigricollis) venom. Modification of the toxin α (dehydrotryptophan-toxin α) permitted its investigation in complex with a synthetic 15-amino acid peptide corresponding to a loop of the agonist-binding site of acetylcholine receptor (AchR) from Torpedo marmorata species. The peptide α-185 possesses a single Trp at the third position (Trp187 of AchR) and a disulfide bridge between Cys192 and Cys193. A single-exponential rotational diffusion time with a constant of 1.65 ns is measured for the isolated 15-amino acid peptide. This suggests that Trp motion in the peptide in solution is strongly correlated with the residues downstream the peptide sequence, which may in part be attributed to long-range order imposed by the disulfide bond. The dynamics of the bound peptide are very different: the presence of two correlation times indicates that the Trp187 of the peptide has a fast motion (τr1= 140 ps and r(0)1= 0.14) relative to the overall rotation of the complex (τr2= 3.4 ns and r(0)2= 0.04). The correlation of the Trp residue with its neighboring amino acid residues and with the overall motion of the peptide is lost, giving rise to its rapid restricted motion. Thus, the internal dynamics of interacting peptides change on binding. (10.1562/0031-8655(2003)0770151PDOAPF2.0.CO2)
    DOI : 10.1562/0031-8655(2003)0770151PDOAPF2.0.CO2
  • Life without dihydrofolate reductase FolA
    • Myllykallio H.
    • Leduc D.
    • Filee J.
    • Liebl Ursula
    Trends in Microbiology, Elsevier , 2003, 11 (5), pp.220 . Reduced folate derivatives participate in numerous reactions of bacterial intermediary metabolism. Consequently, the well-characterized enzyme implicated in the formation of tetrahydrofolate - dihydrofolate reductase FolA - was considered to be essential for bacterial growth. However, comparative genomics has revealed several bacterial genome sequences that appear to lack the folA gene. Here, we provide in silico evidence indicating that folA-lacking bacteria use a recently discovered class of flavin-dependent thymidylate synthases for deoxythymidine-5'-monophosphate synthesis, and propose that many bacteria must contain uncharacterized sources for reduced folate molecules that are still waiting to be discovered. (10.1016/S0966-842X(03)00101-X)
    DOI : 10.1016/S0966-842X(03)00101-X
  • Time-domain interferometry for direct electric-field reconstruction of mid-infrared femtosecond pulses
    • Ventalon Cathie
    • Raser James-M.
    • Joffre Manuel
    Optics Letters, Optical Society of America - OSA Publishing , 2003, 28 (19), pp.1826-1828 . Mid-infrared ultrashort pulses of 9.2-mu;m center wavelength are characterized in both amplitude and phase. This is achieved by use of a variant of spectral phase interferometry for direct electric field reconstruction in which spectral interferometry has been replaced with time-domain interferometry, a technique that is well suited for infrared pulses. The setup permits simultaneous recording of the second-order interferometric autocorrelation, thus providing an independent check on the retrieved spectral phase. Mid-infrared ultrashort pulses of 9.2-mu;m center wavelength are characterized in both amplitude and phase. This is achieved by use of a variant of spectral phase interferometry for direct electric field reconstruction in which spectral interferometry has been replaced with time-domain interferometry, a technique that is well suited for infrared pulses. The setup permits simultaneous recording of the second-order interferometric autocorrelation, thus providing an independent check on the retrieved spectral phase. Cop. 2003 Optical Society of America (10.1364/OL.28.001826)
    DOI : 10.1364/OL.28.001826
  • Precise alignment of a longitudinal Pockels cell for time-resolved circular dichroism experiments
    • Dartigalongue Thibault
    • Hache François
    Journal of the Optical Society of America B, Optical Society of America , 2003, 20 (8), pp.1780 . Artifacts in time-resolved circular dichroism experiments are carefully analyzed. We show that alignment of the longitudinal Pockels cell that modulates the laser polarization in such experiments is crucial. By developing a calculation of the behavior of a slightly misaligned Pockels cell, we are able to propose a simple alignment procedure. This procedure is based on the use of an analyzer at 0° or 45° of the Pockels cell axes, and it allows us to improve the alignment by 3 orders of magnitude and to reduce the artifact below the noise level in our experimental setup. Cop. 2003 Optical Society of America. (10.1364/JOSAB.20.001780)
    DOI : 10.1364/JOSAB.20.001780
  • 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
  • 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+
  • 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
  • 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
  • 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
  • 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.
  • 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.
  • 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
  • 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
  • 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
  • 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