Publications

2009

• Picosecond Transient Circular Dichroism of the Photoreceptor Protein of the Light-Adapted Form of Blepharisma Japonicum
  
  • Hache François
  • Khuc Mai-Thu
  • Brazard Johanna
  • Plaza Pascal
  • Martin Monique M.
  • Checcucci Giovanni
  • Lenci Francesco
  Chemical Physics Letters, Elsevier, 2009, 483, pp.133. We present a picosecond transient circular dichroism study of OBIP, the putative photoreceptor protein involved in the photophobic response of Blepharisma Japonicum. The probe wavelength was chosen at 230 nm. The results are compared to those of the isolated chromophore, OxyBP, in solution. The CD changes in OBIP and OxyBP do not show the same dynamics: OBIP's signal relaxes in a few ps whereas no such decay is obtained for OxyBP. This observation brings support to the formerly evoked existence of a fast photoinduced reaction in the chromoprotein, and demonstrates the implication of local geometrical changes that accompany this process. (10.1016/j.cplett.2009.10.059)
  DOI : 10.1016/j.cplett.2009.10.059
• Erratum to : Application of time-resolved circular dichroism to the study of conformational changes in photochemical and photobiological processes
  
  • Hache François
  Journal of Photochemistry and Photobiology A: Chemistry, Elsevier, 2009, 205 (1), pp.77. (10.1016/j.jphotochem.2009.05.017)
  DOI : 10.1016/j.jphotochem.2009.05.017
• Interaction of carbon monoxide with the apoptosis-inducing cytochrome c-cardiolipin complex
  
  • Kapetanaki Sofia M.
  • Silkstone G.
  • Husu I.
  • Liebl Ursula
  • Wilson M.T.
  • Vos Marten H.
  Biochemistry, American Chemical Society, 2009, 48 (7), pp.1613. The interaction of mitochondrial cytochrome (cyt) c with cardiolipin (CL) is involved in the initial stages of apoptosis. This interaction can lead to destabilization of the heme−Met80 bond and peroxidase activity [Basova, L. V., et al. (2007) Biochemistry 46, 3423−3434]. We show that under these conditions carbon monoxide (CO) binds to cyt c, with very high affinity (5 × 107 M−1), in contrast to the native cyt c protein involved in respiratory electron shuttling that does not bind CO. Binding of CO to the cyt c−CL complex inhibits its peroxidase activity. Photodissociated CO from the cyt c−CL complex shows <20% picosecond geminate rebinding and predominantly bimolecular rebinding, with a second-order rate constant of 107 M−1 s−1, an order of magnitude higher than in myoglobin. These findings contrast with those of Met80X mutant cyt c, where picosecond geminate recombination dominates due to the rigidity of the protein. Our data imply that CL leads to substantial changes in protein conformation and flexibility, allowing access of ligands to the heme. Together with the findings that (a) 30 CL per cyt c are required for full CO binding and (b) salt-induced dissociation indicates that the two negative headgroup charges interact with 5 positive surface charges of the protein, these results are consistent with a CL anchorage model with an acyl chain impaled in the protein [Kalanxhi, E., and Wallace, C. J. A. (2007) Biochem. J. 407, 179−187]. The affinity of CO for the complex is high enough to envisage an antiapoptotic effect of nanomolar CO concentrations via inhibition of the cyt c peroxidase activity. (10.1021/bi801817v)
  DOI : 10.1021/bi801817v
• NO formation by neuronal NO-synthase can be controlled by ultrafast electron injection from a nanotrigger
  
  • Beaumont Edward
  • Lambry Jean-Christophe
  • Blanchard-Desce M.
  • Martasek P.
  • Panda S.P.
  • van Faassen E.E.H.
  • Brochon J.-C.
  • Deprez E.
  • Slama-Schwok Anny
  ChemBioChem, Wiley-VCH Verlag, 2009, 10 (4), pp.690. Nitric oxide synthases (NOSs) are unique flavohemoproteins with various roles in mammalian physiology. Constitutive NOS catalysis is initiated by fast hydride transfer from NADPH, followed by slower structural rearrangements. We used a photoactive nanotrigger (NT) to study the initial electron transfer to FAD in native neuronal NOS (nNOS) catalysis. Molecular modeling and fluorescence spectroscopy showed that selective NT binding to NADPH sites close to FAD is able to override Phe1395 regulation. Ultrafast injection of electrons into the protein electron pathway by NT photoactivation through the use of a femtosecond laser pulse is thus possible. We show that calmodulin, required for NO synthesis by constitutive NOS, strongly promotes intramolecular electron flow (6.2-fold stimulation) by a mechanism involving proton transfer to the reduced FADb site. Site-directed mutagenesis using the S1176A and S1176T mutants of nNOS supports this hypothesis. The NT synchronized the initiation of flavoenzyme catalysis, leading to the formation of NO, as detected by EPR. This NT is thus promising for time-resolved X-ray and other cellular applications. Cop. 2009 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim. (10.1002/cbic.200800721)
  DOI : 10.1002/cbic.200800721
• New insights into size effects in luminescent oxide nanocrystals
  
  • Mialon G.
  • Türkcan Silvan
  • Alexandrou Antigoni
  • Gacoin Thierry
  • Boilot Jean-Pierre
  Journal of Physical Chemistry C, American Chemical Society, 2009, 113 (43), pp.18699. We here investigate the emission properties of rare-earth-doped oxide nanoparticles with the aim to understand the commonly observed altered properties of nanoparticles as compared to the bulk counterparts. This is usually attributed to the detrimental effect of surface states that quench the excited states involved in the emission process. We study the influence of crystalline defects that are present due to the low temperature of the synthesis of 30 nm sized YVO4/Eu nanoparticles. Annealing treatments up to 1000 °C in a porous silica matrix allow the recovery of perfectly crystalline particles as colloidal suspensions and compare their properties to those of the pristine particles obtained by conventional colloid chemistry. Emission properties of pristine and annealed particles are compared with those of the bulk material. A simple model of the emission process allows an accurate fit of the luminescence decay and of the dependence of the quantum yield on europium content. Our results show that pristine particles exhibit altered emission properties mainly due to quenching from defects, among which are surface OH groups, and altered energy transfers within the particle. Annealed particles exhibit properties that are almost the same as those of the bulk material, except that the emission yield for the optimum Eu content is limited to 40 instead of 70% for the bulk material. We show that the difference may be simply explained by the difference of the radiative lifetime that results from the lower effective refractive index in the case of the particles. This effect then seems to be the ultimate limitation for the emission properties of perfectly well-crystallized nanoparticles as compared to those of the bulk material. This work provides an example of a general strategy toward the investigation of the physical properties of nanocrystals which may be altered by crystalline defects. Cop. 2009 American Chemical Society. (10.1021/jp907176x)
  DOI : 10.1021/jp907176x
• Suppression of perturbed free-induction decay and noise in experimental ultrafast pump-probe data
  
  • Nuernberger Patrick
  • Lee Kevin F.
  • Bonvalet Adeline
  • Polack Thomas
  • Vos Marten H.
  • Alexandrou Antigoni
  • Joffre Manuel
  Optics Letters, Optical Society of America - OSA Publishing, 2009, 34 (20), pp.3226-3228. We apply a Fourier filtering technique for the global removal of coherent contributions, like perturbed freeinduction decay, and noise, to experimental pump-probe spectra. A further filtering scheme gains access to spectra otherwise only recordable by scanning the probe's center frequency with adjustable spectral resolution. These methods cleanse pump-probe data and allow improved visualization and simpler analysis of the contained dynamics. We demonstrate these filters using visible pump/mid-infrared probe spectroscopy of ligand dissociation in carboxyhemoglobin. Cop. 2009 Optical Society of America. (10.1364/OL.34.003226)
  DOI : 10.1364/OL.34.003226
• Heme ligand binding properties and intradimer interactions in the full-length sensor protein Dos from Escherichia coli and its isolated heme domain
  
  • Lechauve C.
  • Bouzhir-Sima Latifa
  • Yamashita Taku
  • Marden M.C.
  • Vos Marten H.
  • Liebl Ursula
  • Kiger L.
  Journal of Biological Chemistry, American Society for Biochemistry and Molecular Biology, 2009, 284 (52), pp.36146. Dos from Escherichia coli is a bacterial gas sensor protein comprising a heme-containing gas sensor domain and a phosphodiesterase catalytic domain. Using a combination of static light scattering and gel filtration experiments, we established that, as are many other sensor proteins, the full-length protein is dimeric. The full-length dimer (association constant <10 nm) is more stable than the dimeric heme domain (association constant ∼1 μm), and the dimer interface presumably includes both sensor and catalytic domains. Ultrafast spectroscopic studies showed little influence of the catalytic domain on kinetic processes in the direct vicinity of the heme. By contrast, the properties of ligand (CO and O2) binding to the heme in the sensor domain, occurring on a microsecond to second time scale, were found to be influenced by (i) the presence of the catalytic domain, (ii) the dimerization state, and in dimers, (iii) the ligation state of the other subunit. These results imply allosteric interactions within dimers. Steady-state titrations demonstrated marked cooperativity in oxygen binding to both the full-length protein and the isolated heme domain, a feature not reported to date for any dimeric sensor protein. Analysis of a variety of time-resolved experiments showed that Met-95 plays a major role in the intradimer interactions. The intrinsic binding and dissociation rates of Met-95 to the heme were modulated ∼10-fold by intradimer and sensor-catalytic domain interactions. Dimerization effects were also observed for cyanide binding to the ferric heme domains, suggesting a similar role for Met-95 in ferric proteins. (10.1074/jbc.M109.066811)
  DOI : 10.1074/jbc.M109.066811
• Removing cross-phase modulation from midinfrared chirped-pulse upconversion spectra
  
  • Lee Kevin F.
  • Nuernberger Patrick
  • Bonvalet Adeline
  • Joffre Manuel
  Optics Express, Optical Society of America - OSA Publishing, 2009, 17 (21), pp.18738-18744. We observe that narrow spectral features in mid-infrared spectra obtained by chirped-pulse up-conversion are strongly distorted by crossphase modulation between the mid-infrared field and the chirped pulse. We discuss the consequences of this effect on spectral resolution, and introduce a correction method that recovers masked lines. This simple correction can be applied either when the upconverted field is fully characterized, such as in multidimensional spectroscopy, or when causality can be used, such as in absorption spectroscopy, which we demonstrate experimentally. Cop.2009 Optical Society of America. (10.1364/OE.17.018738)
  DOI : 10.1364/OE.17.018738
• Femto-second ultrashort laser wakefield electron bunch-duration measurements: a prism-based dispersion visible-to-IR spectrometer
  
  • Lim J.
  • Faure Jérôme
  • Gallot Guilhem
  • Lundh O.
  • Rechatin C.
  • Malka Victor
  , 2009, pp.735919. (10.1117/12.829134)
  DOI : 10.1117/12.829134
• Extended fano model of extraordinary electromagnetic transmission through subwavelength hole arrays in the terahertz domain
  
  • Masson Jean-Baptiste
  • Podzorov Alexander
  • Gallot Guilhem
  Optics Express, Optical Society of America - OSA Publishing, 2009, 17 (17), pp.15280-15291. We developed an extended Fano model describing the Extraordinary Electromagnetic Transmission (EET) through arrays of subwavelength apertures, based on terahertz transmission measurements of arrays of various hole size and shapes. Considering a frequency-dependent coupling between resonant and non-resonant pathways, this model gives access to a simple analytical description of EET, provides good agreement with experimental data, and offers new parameters describing the influence of the hole size and shape on the transmitted signal. Cop. 2009 Optical Society of America. (10.1364/OE.17.015280)
  DOI : 10.1364/OE.17.015280
• HIV-1 IN alternative molecular recognition of DNA induced by raltegravir resistance mutations
  
  • Mouscadet J.-F.
  • Arora Rakesh
  • André J.
  • Lambry Jean-Christophe
  • Delelis O.
  • Malet I.
  • Marcelin A.-G.
  • Calvez V.
  • Tchertanov L.
  Journal of Molecular Recognition, Wiley, 2009, 22 (6), pp.480-494. Virologic failure during treatment with raltegravir, the first effective drug targeting HIV integrase, is associated with two exclusive pathways involving either Q148H/R/K, G140S/A or N155H mutations. We carried out a detailed analysis of the molecular and structural effects of these mutations. We observed no topological change in the integrase core domain, with conservation of a newly identified V-shaped hairpin containing the Q148 residue, in particular. In contrast, the mutations greatly altered the specificity of DNA recognition by integrase. The native residues displayed a clear preference for adenine, whereas the mutant residues strongly favored pyrimidines. Raltegravir may bind to N155 and/or Q148 residues as an adenine bioisoster. This may account for the selected mutations impairing raltegravir binding while allowing alternative DNA recognition by integrase. This study opens up new opportunities for the design of integrase inhibitors active against raltegravir-resistant viruses. Copyright Cop. 2009 John Wiley and Sons, Ltd. Supporting information may be found in the online version of this article. (10.1002/jmr.970)
  DOI : 10.1002/jmr.970