Publications

2005

• 11th Congress of the European Society for Photobiology
  
  • Dartigalongue Thibault
  • Hache François
  , 2005.
• Geminate carbon monoxide rebinding to a c-type haem
  
  • Silkstone G.
  • Jasaitis Audrius
  • Vos Marten H.
  • Wilson M.
  Dalton Transactions, Royal Society of Chemistry, 2005, 21 (7), pp.3489. A chemically modified form of cytochrome c (cyt. c), termed carboxymethyl cytochrome c (cm cyt. c), possesses a vacant sixth coordination site to the haem iron that is available to bind external ligands. We present data on the rapid flash photolysis of CO from the ferrous haem iron of cm cyt. c and describe the kinetics and spectral transitions that accompany the recombination. This was achieved using 30-femtosecond laser pulses and a white light continuum to monitor spectral transitions. Whereas the photo-dissociation quantum yield is close to 1, the yield of CO escape from the protein (the apparent quantum yield, φ) relative to myoglobin (φ = 1) is small due to rapid geminate recombination of CO. On ligand photo-dissociation the haem undergoes a spin-state transition from low-spin ferrous CO bound to penta-coordinate high-spin. Subsequently the system reverts to the CO bound form. The data were fitted with a minimum number of exponentials using global analysis. Recombination of CO with the haem iron of cm cyt. c is multiphasic (τ = 16 ps, 120 ps and 1 ns), involving three spectrally distinct components. The fraction of haem (0.11) not recombining with CO within 4 ns is similar to the value of φ (0.12) measured on the same preparation by the "pulse method" (M. Brunori, G. Giacometti, E. Antonini and J. Wyman, Proc. Natl. Acad. Sci. USA, 1973, 70, 3141-3144, ). This implies that no further geminate recombination occurs at t > 4 ns. This unusually efficient CO-haem geminate recombination indicates the sterically hindered ("caged") nature of the distal haem pocket in cm cyt. c from which it is difficult for CO to escape. The large geminate phase may be contrasted with the behaviour of myoglobin in which geminate recombination is small. This is in general agreement with the well-documented extensive structural dynamics in myoglobin that allow ligand passage, and a higher structural rigidity in cyt. c imposed by the restraints of minimising reorganisation energy for electron transfer (M. Brunori, D. Bourgeois and D. Vallone, J. Struct. Biol., 2004, 147, 223-234, ). The high pH ferrous form of cm cyt. c is a low-spin species having a lysine bound to the central iron atom of the haem (M. Brunori, M. Wilson and E. Antonini, J. Biol. Chem., 1972, 247, 6076-6081; G. Silkstone, G. Stanway, P. Brzezinski and M. Wilson, Biophys. Chem., 2002, 98, 65-77, ). This high pH (pH 8) form of deoxy cm cyt. c undergoes photo-dissociation of lysine (although the proximal histidine is possible) after photo-excitation. Recombination occurs with a time constant (τ) of 7 ps. This is similar to that observed for the geminate rebinding of the Met80 residue in native ferrous cyt. c (τ 6 ps) following its photo-dissociation (S. Cianetti, M. Negrerie, M. Vos, J.-L. Martin and S. Kruglik, J. Am. Chem. Soc., 2004, 126, 13932-13933; W. Wang, X. Ye, A. Demidov, F. Rosca, T. Sjodin, W. Cao, M. Sheeran and P. Champion, J. Phys. Chem., 2000, 104, 10789-10801, ). (10.1039/B508183C)
  DOI : 10.1039/B508183C
• Calculation of the circular dichroism spectra of carbon monoxy- and deoxy myoglobin: interpretation of a time-resolved circular dichroism experiment.
  
  • Dartigalongue Thibault
  • Hache François
  The Journal of Chemical Physics, American Institute of Physics, 2005, 123 (18), pp.184901. A calculation of the circular dichroism (CD) spectra of carbon monoxy- and deoxy myoglobin is carried out in relation with a time-resolved CD experiment. The calculation is based on the polarizability theory and the parameters are adjusted to fit the experimental absorption and CD spectra. By performing the calculation for intermediate configurations of the protein, we are able to propose an explanation of the CD structure observed on a sub-100 ps time scale. The role of the proximal histidine is, in particular, clearly demonstrated in the first step of the myoglobin relaxation from its liganded to it deliganded form. (10.1063/1.2041467)
  DOI : 10.1063/1.2041467
• The temperature dependence of the ultrafast electron transfer in cytochrome c oxidase
  
  • Jasaitis Audrius
  • Rappaport Fabrice
  • Pilet Eric
  • Vos Marten H.
  , 2005.
• Unstained Drosophila embryo development analysed by velocimetric third harmonic generation microscopy
  
  • Débarre Delphine
  • Supatto Willy
  • Farge Emmanuel
  • Moulia Bruno B.
  • Schanne-Klein Marie-Claire
  • Beaurepaire Emmanuel
  , 2005.
• Sensibilité structurale et sources de contraste en microscopie par génération de troisième harmonique (THG) appliquée à la biologie
  
  • Débarre Delphine
  • Supatto Willy
  • Pena Ana-Maria
  • Fabre Aude
  • Tordjmann T.
  • Combettes Laurent
  • Schanne-Klein Marie-Claire
  • Beaurepaire Emmanuel
  , 2005.
• Nonlinear optical spectroscopy of chiral molecules
  
  • Hache François
  , 2005.
• Electrical activity alterations induced by chronic absorption of lindane (gamma-hexachlorocyclohexane) trace concentrations in adult rat heart
  
  • Sauviat Martin-Pierre
  • Bouvet Suzanne
  • Godeau Gaston
  • Pages Nicole
  Canadian Journal of Physiology and Pharmacology, NRC Research Press, 2005, 83 (3), pp.243. The heart of adult rat offspring, born to mothers treated with trace concentrations of lindane (0.5 to 2 ppb) through a beverage and to mothers chronically treated with lindane (CL-T) with the same trace concentration, also through a beverage, during lactation and growth has a round shape and accumulates lindane. The left ventricle (LV) presents a hypertrophied area, atrophied papillary muscles, and unorganized collagen bundles and layers. These observations led us to study the electrical activity of their left ventricle papillary muscles (LVPM) by recording action potential using intracellular microelectrodes. CL-T shortened LVPM action potential duration (APD): 1 ppb shortened the plateau; 2 ppb shortened the plateau and the slow repolarizing phase. In CL-T (2 ppb) and untreated groups, low temperature (22 degrees C) decreased the resting potential and prolonged APD. TEA (tetraethylammonium; 1-2 mmol/L) partially lengthened CL-T (2 ppb lindane) APD. Quinidine (0.2 mmol/L) and E-4031 (10 nmol/L) prolonged CL-T APD, suggesting that the rapid delayed outward K+ current (I-Kr) was increased. Our results indicate the silent effects of chronic exposure to trace concentrations of lindane on the morphological and electrical activity of heart muscle. They demonstrate that chronic lindane treatment of female rats alters the tissue integrity and electrical activity in the LV of their offspring. (10.1139/Y04-132)
  DOI : 10.1139/Y04-132
• Chiroptical effects in the second harmonic signal of collagens I and IV
  
  • Pena Ana-Maria
  • Boulesteix Thierry
  • Dartigalongue Thibault
  • Schanne-Klein Marie-Claire
  Journal of the American Chemical Society, American Chemical Society, 2005, 127 (29), pp.10314. We performed polarization-resolved surface second harmonic generation (SHG) experiments on thin films of collagen I and IV molecules, as well as conventional CD measurements. We found that collagen IV presents little CD and no SHG optical activity, whereas collagen I exhibits large chiroptical effects involving both one-electron and excitonic coupling mechanisms. We estimated that these chiral components enhance the SHG signal from fibrillar collagen in biological tissues by typically a factor of 2. By comparing the distinct behaviors of collagens I and IV in SHG microscopy and in surface SHG experiments, we concluded that SHG microscopy is a sensitive probe of the micrometer-scale structural organization of collagen in biological tissues. Cop. 2005 American Chemical Society. (10.1021/ja0520969)
  DOI : 10.1021/ja0520969
• Fourier transform measurement of two-photon excitation spectra: applications to microscopy and optimal control
  
  • Ogilvie Jennifer P.
  • Kubarych Kevin J.
  • Alexandrou Antigoni
  • Joffre Manuel
  Optics Letters, Optical Society of America - OSA Publishing, 2005, 30, pp.911. We report a novel Fourier transform method for measuring two-photon excitation spectra. We demonstrate this method using simple dye molecules and discuss its applications in two-photon fluorescence microscopy and optimal control. This method facilitates an intuitive interpretation of recent control experiments in terms of tuning the nonlinear spectrum of the exciting laser source.