Articles

Comment on "Coherent control of retinal isomerization in bacteriorhodopsin
- Joffre Manuel
Science, American Association for the Advancement of Science (AAAS) , 2007, 317, pp.1137011 .
True near field versus contrast near field imaging. II. imaging with a probe
- Masson Jean-Baptiste
- Gallot Guilhem
Optics Express, Optical Society of America - OSA Publishing , 2007, 15 (6), pp.3078 . In this letter, we extend the results previously found in near field imaging with aperture [Opt. Express 14, 11566 (2006)], where we demonstrated that interaction between light and sample can be divided into two main areas: the true near field and the contrast near field domain. Here, we show that in near field with a probe, the same division of space exists, and thus we show that a much simpler way to model theses experiments can be given. Cop. 2007 Optical Society of America. (10.1364/OE.15.003078)
DOI : 10.1364/OE.15.003078
1-kHz table-top ultrashort hard x-ray source for time-resolved x-ray protein
- Bonvalet Adeline
- Darmon Adeline
- Lambry Jean-Christophe
- Martin Jean-Louis
- Audebert Patrick
Optics Letters, Optical Society of America - OSA Publishing , 2006, 31 (18), pp.2753 . We describe a compact, reliable, and high-average-power femtosecond x-ray source and its first application to diffraction on protein crystal. The setup relies on a homemade Ti: sapphire system delivering 12 mJ at a 1 kHz repetition rate, associated with a small vacuum chamber especially designed for laser-plasma interaction and x-ray applications. This device allows the generation of 5×109 photons/s/sr at 8 keV and optimized x-ray irradiation of the studied sample, which can be placed close to the source. We present the diffraction pattern of a protein crystal in a divergent beam geometry, which is a first step to a subpicosecond x-ray diffraction experiment. (10.1364/OL.31.002753)
DOI : 10.1364/OL.31.002753
Catalytic mechanism and structure of viral flavin-dependent thymidylate synthase ThyX.
- Graziani Sébastien
- Bernauer Julie
- Skouloubris Stéphane
- Graille Marc
- Zhou Cong-Zhao
- Marchand Christophe
- Decottignies Paulette
- van Tilbeurgh Herman
- Myllykallio Hannu
- Liebl Ursula
Journal of Biological Chemistry, American Society for Biochemistry and Molecular Biology , 2006, 281 (33), pp.24048-57 . By using biochemical and structural analyses, we have investigated the catalytic mechanism of the recently discovered flavin-dependent thymidylate synthase ThyX from Paramecium bursaria chlorella virus-1 (PBCV-1). Site-directed mutagenesis experiments have identified several residues implicated in either NADPH oxidation or deprotonation activity of PBCV-1 ThyX. Chemical modification by diethyl pyrocarbonate and mass spectroscopic analyses identified a histidine residue (His53) crucial for NADPH oxidation and located in the vicinity of the redox active N-5 atom of the FAD ring system. Moreover, we observed that the conformation of active site key residues of PBCV-1 ThyX differs from earlier reported ThyX structures, suggesting structural changes during catalysis. Steady-state kinetic analyses support a reaction mechanism where ThyX catalysis proceeds via formation of distinct ternary complexes without formation of a methyl enzyme intermediate. (10.1074/jbc.M600745200)
DOI : 10.1074/jbc.M600745200
Ultrafast heme dynamics in ferrous versus ferric cytochrome c studied by time-resolved resonance Raman and transient absorption spectroscopy.
- Négrerie Michel
- Cianetti Simona
- Vos Marten H.
- Martin Jean-Louis
- Kruglik Sergei G.
Journal of Physical Chemistry B, American Chemical Society , 2006, 110 (25), pp.12766-12781 . Cytochrome c (Cyt c) is a heme protein involved in electron transfer and also in apoptosis. Its heme iron is bisaxially ligated to histidine and methionine side chains and both ferric and ferrous redox states are physiologically relevant, as well as a ligand exchange between internal residue and external diatomic molecule. The photodissociation of internal axial ligand was observed for several ferrous heme proteins including Cyt c, but no time-resolved studies have been reported on ferric Cyt c. To investigate how the oxidation state of the heme influences the primary photoprocesses, we performed a comprehensive comparative study on horse heart Cyt c by subpicosecond time-resolved resonance Raman and femtosecond transient absorption spectroscopy. We found that in ferric Cyt c, in contrast to ferrous Cyt c, the photodissociation of an internal ligand does not take place, and relaxation dynamics is dominated by vibrational cooling in the ground electronic state of the heme. The intermolecular vibrational energy transfer was found to proceed in a single phase with a temperature decay of 7 ps in both ferric and ferrous Cyt c. For ferrous Cyt c, the instantaneous photodissociation of the methionine side chain from the heme iron is the dominant event, and its rebinding proceeds in two phases, with time constants of 5 and 16 ps. A mechanism of this process is discussed, and the difference in photoinduced coordination behavior between ferric and ferrous Cyt c is explained by an involvement of the excited electronic state coupled with conformational relaxation of the heme. (10.1021/jp0559377)
DOI : 10.1021/jp0559377
Ultrashort laser pulses and ultrashort electron bunches generated in relativistic laser-plasma interaction
- Faure Jérôme
- Glinec Y.
- Gallot Guilhem
- Malka Victor
Physics of Plasmas, American Institute of Physics , 2006, 13 (5), pp.056706 . An experimental study of the interaction of ultrashort laser pulses with underdense plasmas in the relativistic regime is presented. A parameter regime of particular interest was found: the so-called bubble regime. In this regime, the laser pulse is focused to relativistic intensities and its pulse duration is comparable to or shorter than the plasma period. A wealth of physical phenomena occurs for such physical parameters. These phenomena have multiple signatures which have been investigated experimentally: (i) the generation of a high quality electron beam (high energy, very collimated, quasimonoenergetic energy distribution); (ii) the laser pulse temporal shortening in nonlinear plasma waves. In addition, experimental results suggest that the electron beam produced in this way has temporal structures shorter than 50 fs. (10.1063/1.2180727)
DOI : 10.1063/1.2180727
Fourier-transform coherent anti-Stokes Raman scattering microscopy.
- Ogilvie Jennifer P.
- Beaurepaire Emmanuel
- Alexandrou Antigoni
- Joffre Manuel
Optics Letters, Optical Society of America - OSA Publishing , 2006, 31 (4), pp.480-2 . We report a novel Fourier-transform-based implementation of coherent anti-Stokes Raman scattering (CARS) microscopy. The method employs a single femtosecond laser source and a Michelson interferometer to create two pulse replicas that are fed into a scanning multiphoton microscope. By varying the time delay between the pulses, we time-resolve the CARS signal, permitting easy removal of the nonresonant background while providing high resolution, spectrally resolved images of CARS modes over the laser bandwidth (approximately 1500 cm(-1)). We demonstrate the method by imaging polystyrene beads in solvent. (10.1364/OL.31.000480)
DOI : 10.1364/OL.31.000480
Insight into Framework Destruction in Ultramarine Pigments
- del Federico Eleonora
- Shöfberger Wolfgang
- Schelvis Johannes
- Kapetanaki Sofia
- Tyne Lindsey
- Jerschow Alexej
Inorganic Chemistry, American Chemical Society , 2006, 45 (3), pp.1270-1276 . (10.1021/ic050903z)
DOI : 10.1021/ic050903z
Use of coherent control for selective two-photon fluorescence microscopy in live organisms.
- Ogilvie Jennifer P.
- Débarre Delphine
- Solinas Xavier
- Martin Jean-Louis
- Beaurepaire Emmanuel
- Joffre Manuel
Optics Express, Optical Society of America - OSA Publishing , 2006, 14 (2), pp.759-766 . We demonstrate selective fluorescence We demonstrate selective fluorescence excitation of specific molecular species in live organisms by using coherent control of two-photon excitation. We have acquired quasi-simultaneous images in live fluorescently-labeled Drosophila embryos by rapid switching between appropriate pulse shapes. Linear combinations of these images demonstrate that a high degree of fluorophore selectivity is attainable through phase-shaping. Broadband phase-shaped excitation opens up new possibilities for single-laser, multiplex, in-vivo fluorescence microscopy. © 2006 Optical Society of America (10.1364/OPEX.14.000759)
DOI : 10.1364/OPEX.14.000759
Observer les neurones grâce aux ondes térahertz
- Gallot Guilhem
La Recherche, Sciences et avenir , 2006, 397, pp.26 . Des chercheurs de l'École polytechnique ont développé un dispositif d'imagerie des neurones, fondée sur l'utilisation d'ondes térahertz [1]. Ils observent ainsi les mouvements d'ions et d'eau à l'intérieur et à proximité des neurones.
Micrometer scale ex vivo multiphoton imaging of unstained arterial wall structure
- Boulesteix Thierry
- Pena Ana-Maria
- Pagès Nicole
- Godeau G.
- Sauviat Martin-Pierre
- Beaurepaire Emmanuel
- Schanne-Klein Marie-Claire
Cytometry Part A, Wiley , 2006, 69A (1), pp.20-26 . We characterize the application of multiphoton microscopy to the observation of the extracellular matrix of fresh unstained vessels. Combined two-photon-excited fluorescence (2PEF) and second harmonic generation (SHG) imaging of large arteries reveals the architecture of elastin and collagen fibers in the vessel wall with remarkable specificity. We present elastin/collagen imaging in unstained rat vessels at both micrometer and whole vessel scales, and we characterize the optical properties of rat carotid artery and aorta walls. We apply this method to evidence deleterious effects of residual doses of a pesticide on the vessel wall. This study illustrates the potential of 2PEF/SHG microscopy for pharmacological studies in unlabeled arteries. © 2005 Wiley-Liss, Inc. (10.1002/cyto.a.20196)
DOI : 10.1002/cyto.a.20196
Chiroptical effects in the second harmonic generation from collagens I and IV: applications in nonlinear microscopy
- Pena Ana-Maria
- Boulesteix Thierry
- Dartigalongue Thibault
- Strupler Mathias
- Beaurepaire Emmanuel
- Schanne-Klein Marie-Claire
Nonlinear optics, quantum optics, Old City Pub. , 2006, 35 (1-3), pp.235-240 . An emerging application of multiphoton microscopy is the observation of unstained intact biological tissues based on intrinsic sources of nonlinear signals. However, reliable biomedical imaging requires a thorough analysis of these endogenous signals. Looking at skin biopsies, we focused on 2-Photon Excited Fluorescence (2PEF) arising from cytokeratins in the epidermis, and second harmonic generation (SHG) from collagen fibers in the dermis. We determined the 2PEF excitation spectrum and action cross section of purified keratins from human epidermis, and obtained a good agreement with in situ measurements. In order to analyze the role of chirality and collagen type in SHG signal, we performed polarization-resolved surface SHG experiments on thin films of collagens I and IV molecules. We observed that collagen I and IV molecules exhibit comparable SHG signals, except for the chiral contributions which are absent for collagen IV and represent typically 50% of the signal for collagen I. We concluded that the large collagen I SHG efficiency is dominated by coherent effects due to the high density and quasi-crystalline order in collagen fibrils, whereas the lack of any alignment within the collagen IV molecules explains the absence of signal from this collagen type in SHG microscopy.
Functional implications of the propionate 7 Arginine 220 interaction in the FixLH oxygen sensor from Bradyrhizobium japonicum
- Balland Véronique
- Bouzhir-Sima Latifa
- Anxolabéhère-Mallart E.
- Boussac A.
- Vos Marten H.
- Liebl Ursula
- Mattioli T.
Biochemistry, American Chemical Society , 2006, 45, pp.2072-2084 .
Role of Heme Iron Coordination and Protein Structure in the Dynamics and Geminate Rebinding of Nitric Oxide to H93G Myoglobin : Implications for NO-Sensors
- Négrerie Michel
- Kruglik Sergei
- Lambry Jean-Christophe
- Vos Marten H.
- Martin Jean-Louis
- Franzen Stefan
Journal of Biological Chemistry, American Society for Biochemistry and Molecular Biology , 2006, 281, pp.10389-10398 .
Role of distal arginine in early sensing intermediates in the heme domain of the oxygen sensor FixL
- Jasaitis Audrius
- Hola Klara
- Bouzhir-Sima Latifa
- Lambry Jean-Christophe
- Balland Véronique
- Vos Marten H.
- Liebl Ursula
Biochemistry, American Chemical Society , 2006, 45, pp.6018-6026 .
Evaluation of 23S rRNA PCR primers for use in phylogenetic studies of bacterial diversity
- Hunt D.E.
- Klepac-Ceraj V.
- Acinas S.G.
- Bertilsson S.
- Gautier Christian
- Polz M.F.
Applied and Environmental Microbiology, American Society for Microbiology , 2006, 72 (3), pp.2221 . The availability of a diverse set of 23S rRNA gene sequences enabled evaluation of the specificity of 39 previously published and 4 newly designed primers specific for bacteria. An extensive clone library constructed using an optimized primer pair resulted in similar gene richness but slightly differing coverage of some phylogenetic groups, compared to a 16S rRNA gene library from the same environmental sample. Copyright Cop. 2006, American Society for Microbiology. All Rights Reserved. (10.1128/AEM.72.3.2221-2225.2006)
DOI : 10.1128/AEM.72.3.2221-2225.2006
A filtering procedure for systematic removal of pump-perturbed polarization artifacts
- Polack Thomas
Optics Express, Optical Society of America - OSA Publishing , 2006, 14, pp.5823 .
Terahertz achromatic quarter-wave plate
- Masson Jean-Baptiste
- Gallot Guilhem
Optics Letters, Optical Society of America - OSA Publishing , 2006, 31 (2), pp.265 . Phase retardera usually present a strong frequency dependence. We discuss the design and characterization of a terahertz achromatic quarter-wave plate. This wave plate is made from six birefringent quartz plates precisely designed and stacked together. Phase retardation has been measured over the whole terahertz range by terahertz polarimetry. This achromatic wave plate demonstrates a huge frequency bandwidth (?max/?min ˜ 7), and therefore can be applied to terahertz time domain spectroscopy and polarimetry. Cop. 2006 Optical Society of America. (10.1364/OL.31.000265)
DOI : 10.1364/OL.31.000265
Photoinduced electron transfer from a novel nanotrigger addressed to the NADPH site within the endothelial NO-synthase to the flavin moieties of the protein
- Beaumont Edward
- Robin Anne-Claire
- Berka Vladimir
- Tsai Ah-Lim
- Blanchard-Desce Mireille
- Lambry Jean-Christophe
- Slama-Schwok Anny
Nitric Oxide: Biology and Chemistry, Elsevier , 2006, 14 (4), pp.14-15 . We developed a new selective molecular tool to trigger enzymatic activity in a synchronous manner and monitor the sequence of the kinetic events by ultra-fast transient spectroscopy. Our approach is based on a synthetic nanotrigger addressing a selected site within proteins, namely the conserved NADPH binding site common to many enzymes involved in bioreductive processes [1]. The nanotrigger combines a "docking" subunit responsible for the recognition of NADPH sites within proteins and a "chromophoric" subunit responsive to light excitation and able to transfer electrons to the flavin moieties of proteins. We present the first spectroscopic data on such a nanotrigger [1] in the presence of the reductase domain of the endothelial nitric oxide synthase eNOSred. (10.1016/j.niox.2006.04.050)
DOI : 10.1016/j.niox.2006.04.050
Nouvelle approche des fibroses par microscopie multiphotonique avec génération de second harmonique [New approach of fibrosis by multiphoton microscopy with second harmonic generation]
- Hernest Monica
- Pena Ana-Maria
- Strupler Mathias
- Beaurepaire Emmanuel
- Martin Jean-Louis
- Schanne-Klein Marie-Claire
- Tharaux Pierre-Louis
Médecine/Sciences, EDP Sciences , 2006, 22 (10), pp.820-821 . La fibrose est une réponse adaptative pathologique qui détruit non spécifiquement les tissus. Il s'agit d'un processus universel de réparation des tissus qui survient en réaction à de nombreux types d'agressions telles les contraintes mécaniques, les brûlures, les radiations ionisantes, l'ischémie, l'inflammation. Ces agressions concourent de manière intriquée à la physiopathologie des maladies infectieuses, tumorales ou auto-immunes, de l'hypertension artérielle et des maladies cardio-vasculaires. Le terme de fibrose décrit précisément l'accumulation nouvelle de protéines de la matrice extra-cellulaire selon un arrangement spatial fibrillaire caractéristique. Il s'agit essentiellement de molécules de collagènes de type I et III (voire de type II, V ou XI) synthétisées sous forme de triples hélices elles-mêmes assemblées en fibrilles par les cellules fibroblastiques. L'apparition des collagènes fibrillaires marque un changement qualitatif et quantitatif de composition des collagènes des tissus. Réciproquement, ces changements de la matrice extracellulaire influencent le phénotype des cellules qui y résident. Ainsi dans le rein normal, le collagène de type I n'existe que dans l'adventice artériel. Son apparition au sein des autres structures de cet organe marque une fibrose tubulo-interstitielle qui constitue le meilleur marqueur pronostic défavorable d'une évolution vers l'insuffisance rénale terminale, et ce quelle que soit la maladie causale. Ainsi, comme lors des fibroses compliquant les hépatopathies et les pneumopathies chroniques, les séquelles de brûlures ou d'abrasions cutanées-muqueuses ou encore le remodelage cardiaque et vasculaire, le réarrangement de la géométrie de la matrice extracellulaire altère l'organisation fonctionnelle du tissu considéré. De ce fait, ce processus de réparation a des effets fonctionnels délétères qui constituent un enjeu médical majeur. Les fibrilles de collagène ont des capacités d'auto-assemblage qui sont aussi catalysées et stabilisées ou au contraire empêchées par les enzymes de la matrice extracellulaire. Le développement de la fibrose ou sa régression dépend donc ainsi du bilan des équilibres biologiques de ces mécanismes. Il est donc crucial de caractériser les changements extracellulaires et cellulaires qui font du restutio ad integrum de l'architecture et de la fonction tissulaire un défi biomédical. (10.1051/medsci/20062210820)
DOI : 10.1051/medsci/20062210820
Role of the middle residue in the triple tryptophan electron transfer chain of DNA photolyase: ultrafast spectroscopy of a Trp→Phe mutant
- Lukacs Andras
- Eker A.P.M.
- Byrdin M.
- Villette Sandrine
- Pan J.
- Brettel K.
- Vos Marten H.
Journal of Physical Chemistry B, American Chemical Society , 2006, 110 (32), pp.15654-15658 .
Endothelial nitric oxide synthase reduces nitrite anions to NO under anoxia
- Gautier Clément
- van Faassen E.
- Mikula I.
- Martasek P.
- Slama-Schwok Anny
Biochemical and Biophysical Research Communications, Elsevier , 2006, 341 (3), pp.816-821 . In this work, we demonstrate that endothelial nitric oxide synthase is capable of anoxic reduction of nitrite anions to nitric oxide at physiological pH by absorption and EPR spectroscopy and electrochemical measurements. The nitrite reduction is achieved at the oxygenase domain of the protein and proceeds even in the absence of the tetrahydrobiopterin cofactor. The nitrite pathway increases by sixfold the NO production with respect to the regular arginine pathway under hypoxia, which is largely blocked. Therefore, basal levels of NO release could be sustained by anoxic nitrite reduction. The reaction suggests a new pathway for fast NO delivery under hypoxia, precisely when the vasodilating properties of nitric oxide are most needed. (c) 2006 Elsevier Inc. All rights reserved. (10.1016/j.bbrc.2006.01.031)
DOI : 10.1016/j.bbrc.2006.01.031
Mechanisms involved in the swelling of erythrocytes caused by Pacific and Caribbean ciguatoxins
- Sauviat Martin-Pierre
- Boydron-Le Garrec Raphaële
- Masson Jean-Baptiste
- Lewis Richard L.
- Vernoux Jean-Paul
- Molgó Jordi
- Laurent Dominique
- Benoit Evelyne
Blood Cells, Molecules and Diseases, Elsevier , 2006, 36(1), pp.1-9 . The mechanisms underlying the swelling of frog red blood cells (RBC), induced by Pacific (P-CTX-1) and Caribbean (C-CTX-1) ciguatoxins (CTXs), were investigated by measuring the length, width and surface of their elliptic shape. P-CTX-1 (0.5 to 5 nM) and C-CTX-1 (1 nM) induced RBC swelling within 60 min. The CTXs-induced RBC swelling was blocked by apamin (1 μM) and by Sr2+ (1 mM). P-CTX-1-induced RBC swelling was prevented and inhibited by H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (27 μM), an inhibitor of soluble guanylate cyclase (sGC), and NOS blockade by NG methyl-l-arginine (l-NMA; 10 μM). Cytochalasin D (cytD, 10 μM) increased RBC surface and mimicked CTX effect but did not prevent the P-CTX-1-induced l-NMA-sensitive extra increase. Calculations revealed that P-CTX-1 and cytD increase RBC total surface envelop and volume. These data strongly suggest that the molecular mechanisms underlying CTXs-induced RBC swelling involve the NO pathway by an activation of the inducible NOS, leading to sGC activation which modulates intracellular cGMP and regulates L-type Ca2+ channels. The resulting increase in intracellular Ca2+ content, in turn, disrupts the actin cytoskeleton, which causes a water influx and triggers a Ca2+-activated K+ current through SK2 isoform channels. (10.1016/j.bcmd.2005.10.007)
DOI : 10.1016/j.bcmd.2005.10.007
Single Lanthanide-doped Oxide Nanoparticles as Donors in Fluorescence Resonance Energy Transfer Experiments
- Casanova Didier
- Giaume D.
- Gacoin Thierry
- Boilot Jean-Pierre
- Alexandrou Antigoni
Journal of Physical Chemistry B, American Chemical Society , 2006, 110(39), pp.19264-19270 .
Coupling between surface plasmons in subwavelength hole arrays
- Masson Jean-Baptiste
- Gallot Guilhem
Physical Review B: Condensed Matter and Materials Physics (1998-2015), American Physical Society , 2006, 73, pp.121401 .