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Accueil > Départements > Biochimie, Biophysique et Biologie Structurale > Bruno ROBERT : Laboratoire Bioenergétique Membranaire et Stress



  • M. J. Llansola-Portoles, K. Redeckas, S. Streckaité, C. Ilioaia, A. A. Pascal, A. Telfer, M. Vengris, L. Valkunas, et B. Robert, « Lycopene crystalloids exhibit singlet exciton fission in tomatoes », Physical Chemistry Chemical Physics, vol. 20, nᵒ 13, p. 8640-8646, 2018.

  • M. K. Shukla, M. J. Llansola-Portoles, M. Tichý, A. A. Pascal, B. Robert, et R. Sobotka, « Binding of pigments to the cyanobacterial high-light-inducible protein HliC », Photosynthesis Research, vol. 137, nᵒ 1, p. 29-39, juill. 2018.
    Résumé : Cyanobacteria possess a family of one-helix high-light-inducible proteins (HLIPs) that are widely viewed as ancestors of the light-harvesting antenna of plants and algae. HLIPs are essential for viability under various stress conditions, although their exact role is not fully understood. The unicellular cyanobacterium Synechocystis sp. PCC 6803 contains four HLIPs named HliA-D, and HliD has recently been isolated in a small protein complex and shown to bind chlorophyll and β-carotene. However, no HLIP has been isolated and characterized in a pure form up to now. We have developed a protocol to purify large quantities of His-tagged HliC from an engineered Synechocystis strain. Purified His-HliC is a pigmented homo-oligomer and is associated with chlorophyll and β-carotene with a 2:1 ratio. This differs from the 3:1 ratio reported for HliD. Comparison of these two HLIPs by resonance Raman spectroscopy revealed a similar conformation for their bound β-carotenes, but clear differences in their chlorophylls. We present and discuss a structural model of HliC, in which a dimeric protein binds four chlorophyll molecules and two β-carotenes.
    Mots-clés : B3S, Chlorophyll, HliC, HLIPs, LBMS, Raman spectroscopy, Synechocystis, β-Carotene.

  • R. R. Sonani, A. Gardiner, R. P. Rastogi, R. Cogdell, B. Robert, et D. Madamwar, « Site, trigger, quenching mechanism and recovery of non-photochemical quenching in cyanobacteria: recent updates », Photosynthesis Research, mars 2018.

  • M. E. Tejeda-Ferrari, C. L. Brown, G. C. C. C. Coutinho, G. A. Gomes de Sá, J. L. Palma, M. J. Llansola-Portoles, G. Kodis, V. Mujica, J. Ho, D. Gust, T. A. Moore, et A. L. Moore, « Electronic Structure and Triplet-Triplet Energy Transfer in Artificial Photosynthetic Antennas », Photochemistry and Photobiology, juill. 2018.
    Résumé : Three Pd(II) phthalocyanine-carotenoid dyads featuring chromophores linked by amide bonds were prepared in order to investigate the rate of triplet-triplet (T-T) energy transfer from the tetrapyrrole to the covalently attached carotenoid as a function of the number of conjugated double bonds in the carotenoid. Carotenoids having 9, 10 and 11 conjugated double bonds were studied. Transient absorption measurements show that intersystem crossing in the Pd(II) phthalocyanine takes place in 10 ps in each case and that T-T energy transfer occurs in 126 ps, 81 ps and 132 ps in the dyads bearing 9, 10 and 11 double bond carotenoids, respectively. To identify the origin of this variation in T-T energy transfer rates, density functional theory (DFT) was used to calculate the T-T electronic coupling in the three dyads. According to the calculations, the primary reason for the observed T-T energy transfer trend is larger T-T electronic coupling between the tetrapyrrole and the 10-double bond carotenoid. A methyl group adjacent to the amide linker that connects the Pd(II) phthalocyanine and the carotenoid in the 9 and 11-double bond carotenoids is absent in the 10-double bond carotenoid, and this difference alters its electronic structure to increase the coupling. This article is protected by copyright. all rights reserved.
    Mots-clés : B3S, LBMS.


  • A. M. Acuña, C. Lemaire, R. van Grondelle, B. Robert, et I. H. M. van Stokkum, « Energy transfer and trapping in Synechococcus WH 7803 », Photosynthesis Research, oct. 2017.
    Résumé : Excitation energy transfer (EET) and trapping in Synechococcus WH 7803 whole cells and isolated photosystem I (PSI) complexes have been studied by time-resolved emission spectroscopy at room temperature (RT) and at 77 K. With the help of global and target analysis, the pathways of EET and the charge separation dynamics have been identified. Energy absorbed in the phycobilisome (PB) rods by the abundant phycoerythrin (PE) is funneled to phycocyanin (PC645) and from there to the core that contains allophycocyanin (APC660 and APC680). Intra-PB EET rates have been estimated to range from 11 to 68/ns. It was estimated that at RT, the terminal emitter of the phycobilisome, APC680, transfers its energy at a rate of 90/ns to PSI and at a rate of 50/ns to PSII. At 77 K, the redshifted Chl a states in the PSI core were heterogeneous, with maximum emission at 697 and 707 nm. In 72% of the PSI complexes, the bulk Chl a in equilibrium with F697 decayed with a main trapping lifetime of 39 ps.
    Mots-clés : B3S, Excitation energy transfer, Global analysis, LBMS, Light harvesting, LPSM, Target analysis.

  • T. Djebaili, S. Abel, M. Marchi, et J. Richardi, « Influence of Force-Field Parameters on the Atomistic Simulations of Metallic Surfaces and Nanoparticles », The Journal of Physical Chemistry C, vol. 121, nᵒ 49, p. 27758-27765, déc. 2017.

  • K. Feilke, G. Ajlani, et A. Krieger-Liszkay, « Correction to ‘Overexpression of plastid terminal oxidase in <i>Synechocystis</i> sp. PCC 6803 alters cellular redox state’ », Philosophical Transactions of the Royal Society B: Biological Sciences, vol. 372, nᵒ 1736, p. 20170277, déc. 2017.

  • K. Feilke, G. Ajlani, et A. Krieger-Liszkay, « Overexpression of plastid terminal oxidase in Synechocystis sp. PCC 6803 alters cellular redox state », Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences, vol. 372, nᵒ 1730, sept. 2017.
    Résumé : Cyanobacteria are the most ancient organisms performing oxygenic photosynthesis, and they are the ancestors of plant plastids. All plastids contain the plastid terminal oxidase (PTOX), while only certain cyanobacteria contain PTOX. Many putative functions have been discussed for PTOX in higher plants including a photoprotective role during abiotic stresses like high light, salinity and extreme temperatures. Since PTOX oxidizes PQH2 and reduces oxygen to water, it is thought to protect against photo-oxidative damage by removing excess electrons from the plastoquinone (PQ) pool. To investigate the role of PTOX we overexpressed rice PTOX fused to the maltose-binding protein (MBP-OsPTOX) in Synechocystis sp. PCC 6803, a model cyanobacterium that does not encode PTOX. The fusion was highly expressed and OsPTOX was active, as shown by chlorophyll fluorescence and P700 absorption measurements. The presence of PTOX led to a highly oxidized state of the NAD(P)H/NAD(P)(+) pool, as detected by NAD(P)H fluorescence. Moreover, in the PTOX overexpressor the electron transport capacity of PSI relative to PSII was higher, indicating an alteration of the photosystem I (PSI) to photosystem II (PSII) stoichiometry. We suggest that PTOX controls the expression of responsive genes of the photosynthetic apparatus in a different way from the PQ/PQH2 ratio.This article is part of the themed issue 'Enhancing photosynthesis in crop plants: targets for improvement'.
    Mots-clés : B3S, cellular redox state, chlorophyll fluorescence, LBMS, MROP, NAD(P)H fluorescence, P700 absorption, plastid terminal oxidase, Synechocystis sp. PCC 6803.

  • G. Folpini, T. Siebert, M. Woerner, S. Abel, D. Laage, et T. Elsaesser, « Water Librations in the Hydration Shell of Phospholipids », The Journal of Physical Chemistry Letters, p. 4492-4497, sept. 2017.
    Résumé : The hydrophilic phosphate moiety in the headgroup of phospholipids forms strong hydrogen bonds with water molecules in the first hydration layer. Time-domain terahertz spectroscopy in a range from 100 to 1000 cm(-1) reveals the influence of such interactions on rotations of water molecules. We determine librational absorption spectra of water nanopools in phospholipid reverse micelles for a range from w0 = 2 to 16 waters per phospholipid molecule. A pronounced absorption feature with maximum at 830 cm(-1) is superimposed on a broad absorption band between 300 and 1000 cm(-1). Molecular dynamics simulations of water in the reverse micelles suggest that the feature at 830 cm(-1) arises from water molecules forming one or two strong hydrogen bonds with phosphate groups, while the broad component comes from bulk-like environments. This behavior is markedly different from water interacting with less polar surfaces.
    Mots-clés : B3S, LBMS.

  • M. Guettari, A. Belaidi, S. Abel, et T. Tajouri, « Polyvinylpyrrolidone Behavior in Water/Ethanol Mixed Solvents: Comparison of Modeling Predictions with Experimental Results », Journal of Solution Chemistry, vol. 46, nᵒ 7, p. 1404-1417, 2017.

  • J. Ho, E. Kish, D. D. Méndez-Hernández, K. WongCarter, S. Pillai, G. Kodis, J. Niklas, O. G. Poluektov, D. Gust, T. A. Moore, A. L. Moore, V. S. Batista, et B. Robert, « Triplet-triplet energy transfer in artificial and natural photosynthetic antennas », Proceedings of the National Academy of Sciences of the United States of America, juin 2017.
    Résumé : In photosynthetic organisms, protection against photooxidative stress due to singlet oxygen is provided by carotenoid molecules, which quench chlorophyll triplet species before they can sensitize singlet oxygen formation. In anoxygenic photosynthetic organisms, in which exposure to oxygen is low, chlorophyll-to-carotenoid triplet-triplet energy transfer (T-TET) is slow, in the tens of nanoseconds range, whereas it is ultrafast in the oxygen-rich chloroplasts of oxygen-evolving photosynthetic organisms. To better understand the structural features and resulting electronic coupling that leads to T-TET dynamics adapted to ambient oxygen activity, we have carried out experimental and theoretical studies of two isomeric carotenoporphyrin molecular dyads having different conformations and therefore different interchromophore electronic interactions. This pair of dyads reproduces the characteristics of fast and slow T-TET, including a resonance Raman-based spectroscopic marker of strong electronic coupling and fast T-TET that has been observed in photosynthesis. As identified by density functional theory (DFT) calculations, the spectroscopic marker associated with fast T-TET is due primarily to a geometrical perturbation of the carotenoid backbone in the triplet state induced by the interchromophore interaction. This is also the case for the natural systems, as demonstrated by the hybrid quantum mechanics/molecular mechanics (QM/MM) simulations of light-harvesting proteins from oxygenic (LHCII) and anoxygenic organisms (LH2). Both DFT and electron paramagnetic resonance (EPR) analyses further indicate that, upon T-TET, the triplet wave function is localized on the carotenoid in both dyads.
    Mots-clés : artificial photosynthesis, B3S, DFT calculations, LBMS, Photoprotection, Resonance Raman, triplet–triplet energy transfer.

  • C. Ilioaia, T. P. J. Krüger, O. Ilioaia, B. Robert, R. van Grondelle, et A. Gall, « Apoprotein heterogeneity increases spectral disorder and a step-wise modification of the B850 fluorescence peak position », Biochimica Et Biophysica Acta, nov. 2017.
    Résumé : It has already been established that the quaternary structure of the main light-harvesting complex (LH2) from the photosynthetic bacterium Rhodopseudomonas palustris is a nonameric 'ring' of PucAB heterodimers and under low-light culturing conditions an increased diversity of PucB synthesis occurs. In this work, single molecule fluorescence emission studies show that different classes of LH2 'rings' are present in "low-light" adapted cells and that an unknown chaperon process creates multiple sub-types of 'rings' with more conformational sub-states and configurations. This increase in spectral disorder significantly augments the cross-section for photon absorption and subsequent energy flow to the reaction centre trap when photon availability is a limiting factor. This work highlights yet another variant used by phototrophs to gather energy for cellular development.
    Mots-clés : B3S, LBMS, light harvesting complexes, photosynthesis, purple bacteria, single molecule spectroscopy.

  • E. Karakas, C. Taveneau, S. Bressanelli, M. Marchi, B. Robert, et S. Abel, « Derivation of original RESP atomic partial charges for MD simulations of the LDAO surfactant with AMBER: applications to a model of micelle and a fragment of the lipid kinase PI4KA », Journal of Biomolecular Structure and Dynamics, vol. 35, nᵒ 1, p. 159-181, janv. 2017.
    Mots-clés : Amber, B3S, Dimethylamines, fluorescence spectroscopy, IMAPP, LBMS, LDAO surfactant, lipid kinase PI4KA, Lipids, MD simulation, micelle, Micelles, Minor Histocompatibility Antigens, Molecular Conformation, Molecular Dynamics Simulation, molecular modeling, Phosphotransferases (Alcohol Group Acceptor), Protein Binding, Proteins, Static Electricity, Surface-Active Agents.

  • J. Keirsse-Haquin, T. Picaud, L. Bordes, A. G. de Gracia, et A. Desbois, « Modulation of the flavin-protein interactions in NADH peroxidase and mercuric ion reductase: a resonance Raman study », European biophysics journal: EBJ, sept. 2017.
    Résumé : NADH peroxidase (Npx) and mercuric ion reductase (MerA) are flavoproteins belonging to the pyridine nucleotide:disulfide oxidoreductases (PNDO) and catalyzing the reduction of toxic substrates, i.e., hydrogen peroxide and mercuric ion, respectively. To determine the role of the flavin adenine dinucleotide (FAD) in the detoxification mechanism, the resonance Raman (RR) spectra of these enzymes under various redox and ligation states have been investigated using blue and/or near-UV excitation(s). These data were compared to those previously obtained for glutathione reductase (GR), another enzyme of the PNDO family, but catalyzing the reduction of oxidized glutathione. Spectral differences have been detected for the marker bands of the isoalloxazine ring of Npx, MerA, and GR. They provide evidence for different catalytic mechanisms in these flavoproteins. The RR modes of the oxidized and two-electron reduced (EH2) forms of Npx are related to very tight flavin-protein interactions maintaining a nearly planar conformation of the isoalloxazine tricycle, a low level of H-bonding at the N1/N5 and O2/O4 sites, and a strong H-bond at N3H. They also indicate minimal changes in FAD structure and environment upon either NAD(H) binding or reduction of the sulfinic redox center. All these spectroscopic data support an enzyme functioning centered on the Cys-SO(-)/Cys-S(-) redox moiety and a neighbouring His residue. On the contrary, the RR data on various functional forms of MerA are indicative of a modulation of both ring II distortion and H-bonding states of the N5 site and ring III. The Cd(II) binding to the EH2-NADP(H) complexes, biomimetic intermediates in the reaction of Hg(II) reduction, provokes important spectral changes. They are interpreted in terms of flattening of the isoalloxazine ring and large decreases in H-bonding at the N5 site and ring III. The large flexibility of the FAD structure and environment in MerA is in agreement with proposed mechanisms involving C4a(flavin) adducts.
    Mots-clés : B3S, Detoxification mechanism, Flavin–protein interactions, Isoalloxazine modes, LBMS, LSOD, Resonance Raman.

  • M. J. Llansola-Portoles, R. Litvin, C. Ilioaia, A. A. Pascal, D. Bina, et B. Robert, « Pigment structure in the violaxanthin-chlorophyll-a-binding protein VCP », Photosynthesis Research, juill. 2017.
    Résumé : Resonance Raman spectroscopy was used to evaluate pigment-binding site properties in the violaxanthin-chlorophyll-a-binding protein (VCP) from Nannochloropsis oceanica. The pigments bound to this antenna protein are chlorophyll-a, violaxanthin, and vaucheriaxanthin. The molecular structures of bound Chl-a molecules are discussed with respect to those of the plant antenna proteins LHCII and CP29, the crystal structures of which are known. We show that three populations of carotenoid molecules are bound by VCP, each of which is in an all-trans configuration. We assign the lower-energy absorption transition of each of these as follows. One violaxanthin population absorbs at 485 nm, while the second population is red-shifted and absorbs at 503 nm. The vaucheriaxanthin population absorbs at 525 nm, a position red-shifted by 2138 cm(-1) as compared to isolated vaucheriaxanthin in n-hexane. The red-shifted violaxanthin is slightly less planar than the blue-absorbing one, as observed for the two central luteins in LHCII, and we suggest that these violaxanthins occupy the two equivalent binding sites in VCP at the centre of the cross-brace. The presence of a highly red-shifted vaucheriaxanthin in VCP is reminiscent of the situation of FCP, in which (even more) highly red-shifted populations of fucoxanthin are present. Tuning carotenoids to absorb in the green-yellow region of the visible spectrum appears to be a common evolutionary response to competition with other photosynthetic species in the aquatic environment.
    Mots-clés : B3S, Carotenoids, LBMS, Light-harvesting complex, Nannochloropsis oceanica, Resonance Raman, VCP.

  • M. J. Llansola-Portoles, A. A. Pascal, et B. Robert, « Electronic and vibrational properties of carotenoids: from in vitro to in vivo », Journal of the Royal Society, Interface, vol. 14, nᵒ 135, oct. 2017.
    Résumé : Carotenoids are among the most important organic compounds present in Nature and play several essential roles in biology. Their configuration is responsible for their specific photophysical properties, which can be tailored by changes in their molecular structure and in the surrounding environment. In this review, we give a general description of the main electronic and vibrational properties of carotenoids. In the first part, we describe how the electronic and vibrational properties are related to the molecular configuration of carotenoids. We show how modifications to their configuration, as well as the addition of functional groups, can affect the length of the conjugated chain. We describe the concept of effective conjugation length, and its relationship to the S0 → S2 electronic transition, the decay rate of the S1 energetic level and the frequency of the ν1 Raman band. We then consider the dependence of these properties on extrinsic parameters such as the polarizability of their environment, and how this information (S0 → S2 electronic transition, ν1 band position, effective conjugation length and polarizability of the environment) can be represented on a single graph. In the second part of the review, we use a number of specific examples to show that the relationships can be used to disentangle the different mechanisms tuning the functional properties of protein-bound carotenoids.
    Mots-clés : B3S, Carotenoids, electronic properties, LBMS, Resonance Raman, vibrational properties.

  • M. J. Llansola-Portoles, R. Sobotka, E. Kish, M. K. Shukla, A. A. Pascal, T. Polívka, et B. Robert, « Twisting a β-Carotene, an Adaptive Trick from Nature for Dissipating Energy during Photoprotection », Journal of Biological Chemistry, vol. 292, nᵒ 4, p. 1396-1403, janv. 2017.
    Mots-clés : B3S, carotenoid, Chlorophyll, Cyanobacteria, LBMS, light-harvesting complex (antenna complex), photosynthesis.

  • F. Ma, L. - J. Yu, M. J. Llansola-Portoles, B. Robert, Z. - Y. Wang-Otomo, et R. van Grondelle, « Metal Cations Induced αβ-BChl a Heterogeneity in LH1 as Revealed by Temperature-Dependent Fluorescence Splitting », Chemphyschem: A European Journal of Chemical Physics and Physical Chemistry, juin 2017.
    Résumé : Two spectral forms of the core light-harvesting complex (LH1) of the purple bacterium Thermochromatium (Tch.) tepidum, the native Ca(2+) -binding and the Ba(2+) -substituted one, exhibit different fluorescence (FL) emission spectra at low temperature (T). While Ca-LH1 exhibits one emission band, an unusual splitting of the fluorescence is observed for Ba-LH1. These two sub-bands display the same spectral-width dependence according to T, but their intensity evolves differently with T. Based on the crystal structures, we propose that the FL splitting originates from a large αβ-BChl a transition energy heterogeneity, ≈600 cm(-1) , which is much larger compared with other LH1 and LH2 complexes (80-200 cm(-1) ). This large heterogeneity is induced by the inhomogeneous Coulomb (and possibly hydrogen-bonding) interactions exerted by Ba(2+) . The energy levels of the two LH1s were compared using exciton calculations in combination with Redfield theory. To simulate the FL splitting, an electronic transition containing two resonant bands was considered. This work shows how metal cations incorporated into the polypeptide modulate the electronic properties of BChl a aggregates.
    Mots-clés : B3S, core light-harvesting complex, fluorescence spectroscopy, LBMS, Redfield theory, transition energy, αβ-BChl a heterogeneity.

  • E. Peuchant, M. - L. Bats, I. Moranvillier, M. Lepoivre, J. Guitton, D. Wendum, M. - L. Lacombe, F. Moreau-Gaudry, M. Boissan, et S. Dabernat, « Metastasis suppressor NM23 limits oxidative stress in mammals by preventing activation of stress-activated protein kinases/JNKs through its nucleoside diphosphate kinase activity », FASEB journal: official publication of the Federation of American Societies for Experimental Biology, vol. 31, nᵒ 4, p. 1531-1546, avr. 2017.
    Résumé : NME1 (nonmetastatic expressed 1) gene, which encodes nucleoside diphosphate kinase (NDPK) A [also known as nonmetastatic clone 23 (NM23)-H1 in humans and NM23-M1 in mice], is a suppressor of metastasis, but several lines of evidence-mostly from plants-also implicate it in the regulation of the oxidative stress response. Here, our aim was to investigate the physiologic relevance of NDPK A with respect to the oxidative stress response in mammals and to study its molecular basis. NME1-knockout mice died sooner, suffered greater hepatocyte injury, and had lower superoxide dismutase activity than did wild-type (WT) mice in response to paraquat-induced acute oxidative stress. Deletion of NME1 reduced total NDPK activity and exacerbated activation of the stress-related MAPK, JNK, in the liver in response to paraquat. In a mouse transformed hepatocyte cell line and in primary cultures of normal human keratinocytes, MAPK activation in response to H2O2 and UVB, respectively, was dampened by expression of NM23-M1/NM23-H1, dependent on its NDPK catalytic activity. Furthermore, excess or depletion of NM23-M1/NM23-H1 NDPK activity did not affect the intracellular bulk concentration of nucleoside di- and triphosphates. NME1-deficient mouse embryo fibroblasts grew poorly in culture, were more sensitive to stress than WT fibroblasts, and did not immortalize, which suggested that they senesce earlier than do WT fibroblasts. Collectively, these results indicate that the NDPK activity of NM23-M1/NM23-H1 protects cells from acute oxidative stress by inhibiting activation of JNK in mammal models.-Peuchant, E., Bats, M.-L., Moranvillier, I., Lepoivre, M., Guitton, J., Wendum, D., Lacombe, M.-L., Moreau-Gaudry, F., Boissan, M., Dabernat, S. Metastasis suppressor NM23 limits oxidative stress in mammals by preventing activation of stress-activated protein kinases/JNKs through its nucleoside diphosphate kinase activity.
    Mots-clés : B3S, hepatocyte, keratinocyte, LBMS, MAPK, NDPK.

  • R. Ranjbar Choubeh, R. R. Sonani, D. Madamwar, P. C. Struik, A. N. Bader, B. Robert, et H. van Amerongen, « Picosecond excitation energy transfer of allophycocyanin studied in solution and in crystals », Photosynthesis Research, juill. 2017.
    Résumé : Cyanobacteria perform photosynthesis with the use of large light-harvesting antennae called phycobilisomes (PBSs). These hemispherical PBSs contain hundreds of open-chain tetrapyrrole chromophores bound to different peptides, providing an arrangement in which excitation energy is funnelled towards the PBS core from where it can be transferred to photosystem I and/or photosystem II. In the PBS core, many allophycocyanin (APC) trimers are present, red-light-absorbing phycobiliproteins that covalently bind phycocyanobilin (PCB) chromophores. APC trimers were amongst the first light-harvesting complexes to be crystallized. APC trimers have two spectrally different PCBs per monomer, a high- and a low-energy pigment. The crystal structure of the APC trimer reveals the close distance (~21 Å) between those two chromophores (the distance within one monomer is ~51 Å) and this explains the ultrafast (~1 ps) excitation energy transfer (EET) between them. Both chromophores adopt a somewhat different structure, which is held responsible for their spectral difference. Here we used spectrally resolved picosecond fluorescence to study EET in these APC trimers both in crystallized and in solubilized form. We found that not all closely spaced pigment couples consist of a low- and a high-energy pigment. In ~10% of the cases, a couple consists of two high-energy pigments. EET to a low-energy pigment, which can spectrally be resolved, occurs on a time scale of tens of picoseconds. This transfer turns out to be three times faster in the crystal than in the solution. The spectral characteristics and the time scale of this transfer component are similar to what have been observed in the whole cells of Synechocystis sp. PCC 6803, for which it was ascribed to EET from C-phycocyanin to APC. The present results thus demonstrate that part of this transfer should probably also be ascribed to EET within APC trimers.
    Mots-clés : Allophycocyanin crystals, B3S, Cyanobacteria, Excitation energy transfer, LBMS, Phycobilisome, Time-resolved fluorescence spectroscopy.

  • S. Sokolova, C. Lamy, J. Peixoto, et M. Lepoivre, « [The loss of SCRIB ignites the macrophages] », Medecine Sciences: M/S, vol. 33, nᵒ 10, p. 849-851, oct. 2017.


  • S. Abel, N. Galamba, E. Karakas, M. Marchi, W. H. Thompson, et D. Laage, « On the Structural and Dynamical Properties of DOPC Reverse Micelles », Langmuir: the ACS journal of surfaces and colloids, oct. 2016.
    Résumé : The structure and dynamics of phospholipid reverse micelles are studied by molecular dynamics. We report all-atom unconstrained simulations of 1,2-dioleoyl-sn-phosphatidylcholine (DOPC) reverse micelles in benzene of increasing sizes, with water-to-surfactant number ratios ranging from W0 = 1 to 16. The aggregation number, i.e., the number of DOPC molecules per reverse micelle, is determined to fit experimental light-scattering measurements of the reverse micelle diameter. The simulated reverse micelles are found to be approximately spherical. Larger reverse micelles (W0 > 4) exhibit a layered structure with a water core and the hydration structure of DOPC phosphate head groups is similar to that found in phospholipid membranes. In contrast, the structure of smaller reverse micelles (W0 ≤ 4) cannot be described as a series of concentric layers successively containing water, surfactant head groups, and surfactant tails, and the head groups are only partly hydrated and frequently present in the core. The dynamics of water molecules within the phospholipid reverse micelles slow down as the reverse micelle size decreases, in agreement with prior studies on AOT and Igepal reverse micelles. However, the average water reorientation dynamics in DOPC reverse micelles is found to be much slower than in AOT and Igepal reverse micelles with the same W0 ratio. This is explained by the smaller water pool and by the stronger interactions between water and the charged head groups, as confirmed by the red-shift of the computed infrared line shape with decreasing W0.
    Mots-clés : B3S, LBMS.

  • E. Kish, K. Wang, M. J. Llansola-Portoles, C. Ilioaia, A. A. Pascal, B. Robert, et C. Yang, « Probing the pigment binding sites in LHCII with resonance Raman spectroscopy: The effect of mutations at S123 », Biochimica et Biophysica Acta (BBA) - Bioenergetics, vol. 1857, nᵒ 9, p. 1490-1496, 2016.
    Mots-clés : B3S, carotenoid, Electronic absorption, LBMS, LHCII, Lutein, Neoxanthin, Resonance Raman.

  • F. Lebourg, S. Paulcan, et M. Lepoivre, « [The two-faced Sestrin2 against age-related pathologies] », Medecine Sciences: M/S, vol. 32, nᵒ 6-7, p. 580-582, juill. 2016.

  • X. Liang, M. Marchi, C. Guo, Z. Dang, et S. Abel, « Atomistic Simulation of Solubilization of Polycyclic Aromatic Hydrocarbons in a Sodium Dodecyl Sulfate Micelle », Langmuir: the ACS journal of surfaces and colloids, vol. 32, nᵒ 15, p. 3645-3654, avr. 2016.
    Résumé : Solubilization of two polycyclic aromatic hydrocarbons (PAHs), naphthalene (NAP, 2-benzene-ring PAH) and pyrene (PYR, 4-benzene-ring PAH), into a sodium dodecyl sulfate (SDS) micelle was studied through all-atom molecular dynamics (MD) simulations. We find that NAP as well as PYR could move between the micelle shell and core regions, contributing to their distribution in both regions of the micelle at any PAH concentration. Moreover, both NAP and PYR prefer to stay in the micelle shell region, which may arise from the greater volume of the micelle shell, the formation of hydrogen bonds between NAP and water, and the larger molecular volume of PYR. The PAHs are able to form occasional clusters (from dimer to octamer) inside the micelle during the simulation time depending on the PAH concentration in the solubilization systems. Furthermore, the micelle properties (i.e., size, shape, micelle internal structure, alkyl chain conformation and orientation, and micelle internal dynamics) are found to be nearly unaffected by the solubilized PAHs, which is irrespective of the properties and concentrations of PAHs.
    Mots-clés : B3S, LBMS.

  • M. J. Llansola-Portoles, C. Uragami, A. A. Pascal, D. Bina, R. Litvin, et B. Robert, « Pigment structure in the FCP-like light-harvesting complex from Chromera velia », Biochimica et Biophysica Acta (BBA) - Bioenergetics, vol. 1857, nᵒ 11, p. 1759-1765, 2016.
    Mots-clés : B3S, Carotenoids, Chlorophylls, CLH, LBMS, light harvesting complexes, photosynthesis, Resonance Raman.

  • M. Marchi, « A first principle particle mesh method for solution SAXS of large bio-molecular systems », The Journal of Chemical Physics, vol. 145, nᵒ 4, p. 045101, juill. 2016.
    Résumé : This paper will show that the solution small angle X-ray scattering (SAXS) intensity of globular and membrane proteins can be efficiently and accurately computed from molecular dynamics trajectories using 3D fast Fourier transforms (FFTs). A suitable particle meshing interpolation, similar to the one used in smooth particle mesh Ewald for electrostatic energies and forces, was combined with a uniform solvent density FFT padding scheme to obtain a convenient SAXS spectral resolution. The CPU time scaling of the method, as a function of system size, is highly favorable and its application to large systems such as solutions of solvated membrane proteins is computationally undemanding. Differently from other approaches, all contributions from the simulation cell are included. This means that the subtraction of the buffer from the solution scattering intensity is straightforward and devoid of artifact due to ad hoc definitions of proximal and distal solvent intensity contributions.
    Mots-clés : Animals, Aquaporins, B3S, Cattle, Chickens, Chymotrypsinogen, Computer Simulation, Eye Proteins, Fourier Analysis, LBMS, Micelles, Molecular Dynamics Simulation, Muramidase, Scattering, Small Angle, Solutions, Solvents, Static Electricity, X-Ray Diffraction.


  • A. - A. Arteni, M. Fradot, D. Galzerano, M. M. Mendes-Pinto, J. - A. Sahel, S. Picaud, B. Robert, et A. A. Pascal, « Structure and Conformation of the Carotenoids in Human Retinal Macular Pigment », PLOS ONE, vol. 10, nᵒ 8, p. e0135779, août 2015.
    Mots-clés : B3S, Humans, LBMS, Lutein, Macular Pigment, Molecular Conformation, PF, Retinal Pigments, SE, Spectrum Analysis, Raman, Zeaxanthins.

  • V. Butkus, A. Gelzinis, R. Augulis, A. Gall, C. Büchel, B. Robert, D. Zigmantas, L. Valkunas, et D. Abramavicius, « Coherence and population dynamics of chlorophyll excitations in FCP complex: Two-dimensional spectroscopy study », The Journal of Chemical Physics, vol. 142, nᵒ 21, p. 212414, juin 2015.

  • T. Djebaili, J. Richardi, S. Abel, et M. Marchi, « Atomistic Simulations of Self-Assembled Monolayers on Octahedral and Cubic Gold Nanocrystals », The Journal of Physical Chemistry C, vol. 119, nᵒ 36, p. 21146-21154, sept. 2015.

  • A. Gall, C. Ilioaia, T.  P. J. Krüger, V.  I. Novoderezhkin, B. Robert, et R. van Grondelle, « Conformational Switching in a Light-Harvesting Protein as Followed by Single-Molecule Spectroscopy », Biophysical Journal, vol. 108, nᵒ 11, p. 2713-2720, 2015.

  • A. Gall, A. A. Pascal, et B. Robert, « Vibrational techniques applied to photosynthesis: Resonance Raman and fluorescence line-narrowing », Biochimica et Biophysica Acta (BBA) - Bioenergetics, vol. 1847, nᵒ 1, p. 12-18, 2015.
    Mots-clés : B3S, carotenoid, Carotenoids, Chlorophyll, LBMS, Light-harvesting, PF, photosynthesis, Pigments, Biological, Reaction center, Spectrometry, Fluorescence, Spectrum Analysis, Raman, SV, Vibration.

  • A. Gelzinis, V. Butkus, E. Songaila, R. Augulis, A. Gall, C. Büchel, B. Robert, D. Abramavicius, D. Zigmantas, et L. Valkunas, « Mapping energy transfer channels in fucoxanthin–chlorophyll protein complex », Biochimica et Biophysica Acta (BBA) - Bioenergetics, vol. 1847, nᵒ 2, p. 241-247, 2015.

  • E. Kish, M. M. M. Pinto, D. Kirilovsky, R. Spezia, et B. Robert, « Echinenone vibrational properties: From solvents to the orange carotenoid protein », Biochimica et Biophysica Acta (BBA) - Bioenergetics, vol. 1847, nᵒ 10, p. 1044-1054, 2015.
    Mots-clés : B3S, Biophysics, carotenoid, Density functional theory, LBMS, MROP, Orange carotenoid protein (OCP), Photoprotection, Raman spectroscopy.

  • M. Macernis, D. Galzerano, J. Sulskus, E. Kish, Y. - H. Kim, S. Koo, L. Valkunas, et B. Robert, « Resonance Raman spectra of carotenoid molecules: influence of methyl substitutions », The Journal of Physical Chemistry. A, vol. 119, nᵒ 1, p. 56-66, janv. 2015.
    Résumé : We report here the resonance Raman spectra and the quantum chemical calculations of the Raman spectra for β-carotene and 13,13'-diphenyl-β-carotene. The first aim of this approach was to test the robustness of the method used for modeling β-carotene, and assess whether it could accurately predict the vibrational properties of derivatives in which conjugated substituents had been introduced. DFT calculations, using the B3LYP functional in combination with the 6-311G(d,p) basis set, were able to accurately predict the influence of two phenyl substituents connected to the β-carotene molecule, although these deeply perturb the vibrational modes. This experimentally validated modeling technique leads to a fine understanding of the origin of the carotenoid resonance Raman bands, which are widely used for assessing the properties of these molecules, and in particular in complex media, such as binding sites provided by biological macromolecules.
    Mots-clés : B3S, Carotenoids, LBMS, Models, Molecular, Molecular Structure, Quantum Theory, Spectrum Analysis, Raman.

  • S. Manet, A. - S. Cuvier, C. Valotteau, G. C. Fadda, J. Perez, E. Karakas, S. Abel, et N. Baccile, « Structure of Bolaamphiphile Sophorolipid Micelles Characterized with SAXS, SANS, and MD Simulations », The Journal of Physical Chemistry B, vol. 119, nᵒ 41, p. 13113-13133, oct. 2015.

  • M. Marchi et S. Abel, « Modeling the Self-Aggregation of Small AOT Reverse Micelles from First-Principles », The Journal of Physical Chemistry Letters, vol. 6, nᵒ 1, p. 170-174, janv. 2015.

  • A. Mezzetti, E. Kish, B. Robert, et R. Spezia, « Assignment of IR bands of isolated and protein-bound Peridinin in its fundamental and triplet state by static FTIR, time-resolved step-scan FTIR and DFT calculations », Journal of Molecular Structure, vol. 1090, p. 58-64, 2015.

  • E.  G. Petrov, B. Robert, S.  H. Lin, et L. Valkunas, « Theory of Triplet Excitation Transfer in the Donor-Oxygen-Acceptor System: Application to Cytochrome b 6 f », Biophysical Journal, vol. 109, nᵒ 8, p. 1735-1745, 2015.

  • L. Premvardhan, B. Robert, et R. G. Hiller, « Pigment organisation in the membrane-intrinsic major light-harvesting complex of Amphidinium carterae: Structural characterisation of the peridinins and chlorophylls a and c2 by resonance Raman spectroscopy and from sequence analysis », Biochimica et Biophysica Acta (BBA) - Bioenergetics, vol. 1847, nᵒ 10, p. 1187-1199, 2015.

  • T. Ragot, C. Provost, A. Prignon, R. Cohen, M. Lepoivre, et S. Lausson, « Apoptosis induction by combination of drugs or a conjugated molecule associating non-steroidal anti-inflammatory and nitric oxide donor effects in medullary thyroid cancer models: implication of the tumor suppressor p73 », Thyroid Research, vol. 8, p. 13, 2015.
    Résumé : BACKGROUND: Medullary thyroid cancer (MTC) is a C-cell neoplasm. Surgery remains its main treatment. Promising therapies based on tyrosine kinase inhibitors demand careful patient selection. We previously observed that two non-steroidal anti-inflammatory drugs (NSAID), indomethacin, celecoxib, and nitric oxide (NO) prevented tumor growth in a model of human MTC cell line (TT) in nude mice. METHODS: In the present study, we tested the NO donor: glyceryl trinitrate (GTN), at pharmacological dose, alone and in combination with each of the two NSAIDs on TT cells. We also assessed the anti-proliferative potential of NO-indomethacin, an indomethacin molecule chemically conjugated with a NO moiety (NCX 530, Nicox SA) on TT cells and indomethacin/GTN association in rMTC 6-23 cells. The anti-tumoral action of the combined sc. injections of GTN with oral delivery of indomethacin was also studied on subcutaneous TT tumors in nude mice. Apoptosis mechanisms were assessed by expression of caspase-3, TAp73α, TAp73α inhibition by siRNA or Annexin V externalisation. RESULTS: The two NSAIDs and GTN reduced mitotic activity in TT cells versus control (cell number and PCNA protein expression). The combined treatments amplified the anti-tumor effect of single agents in the two tested cell lines and promoted cell death. Moreover, indomethacin/GTN association stopped the growth of established TT tumors in nude mice. We observed a significant cleavage of full length PARP, a caspase-3 substrate. The cell death appearance was correlated with a two-fold increase in TAp73α expression, with inhibition of apoptosis after TAp73α siRNA addition, demonstrating its crucial role in apoptosis. CONCLUSION: Association of NO with NSAID exhibited amplified anti-tumoral effects on in vitro and in vivo MTC models by inducing p73-dependent apoptotic cell death.
    Mots-clés : Apoptosis, B3S, LBMS, Medullary thyroid carcinoma, NO-donors, Non-steroidal anti-inflammatory drugs, rMTC 6–23 cells, TT cells.

  • A. Tebbi, O. Guittet, K. Tuphile, A. Cabrié, et M. Lepoivre, « Caspase-dependent Proteolysis of Human Ribonucleotide Reductase Small Subunits R2 and p53R2 during Apoptosis », Journal of Biological Chemistry, vol. 290, nᵒ 22, p. 14077-14090, mai 2015.

  • C. Valéry, S. Deville-Foillard, C. Lefebvre, N. Taberner, P. Legrand, F. Meneau, C. Meriadec, C. Delvaux, T. Bizien, E. Kasotakis, C. Lopez-Iglesias, A. Gall, S. Bressanelli, M. - H. Le Du, M. Paternostre, et F. Artzner, « Atomic view of the histidine environment stabilizing higher-pH conformations of pH-dependent proteins », Nature Communications, vol. 6, p. 7771, juill. 2015.
    Mots-clés : B3S, Crystallography, X-Ray, Histidine, Hydrogen-Ion Concentration, IMAPP, INTGEN, LBMS, Models, Molecular, Nanotubes, Peptide, Optical Imaging, Protein Conformation, Protein Structure, Secondary, Spectroscopy, Fourier Transform Infrared, Spectrum Analysis, Raman, Triptorelin Pamoate.
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- Probing the carotenoid content of intact Cyclotella cells by resonance Raman spectroscopy. Alexandre MTA, Gundermann K, Pascal AA, van Grondelle R, Buchel C, Robert B. Photosynth. Res. 119 (3), 273-281, 2014.

- Electrochemical formation and reactivity of a manganese peroxo complex : acid driven H2O2 generation vs. O-O bond cleavage. Ching HYV, Anxolabehere-Mallart E, Colmer HE, Costentin C, Dorlet P, Jackson TA, Policar C, Robert M. Chem. Sci. 5 (6), 2304-2310, 2014.

- Fermi Resonance as a Tool for Probing Peridinin Environment. Kish E, Pinto MMM, Bovi D, Basire M, Guidoni L, Vuilleumier R, Robert B, Spezia R, Mezzetti A. J. Phys. Chem. B 118 (22), 5873-5881, 2014.

- Resonance Raman Spectra and Electronic Transitions in Carotenoids : A Density Functional Theory Study. Macernis M, Sulskus J, Malickaja S, Robert B, Valkunas L
J. Phys. Chem. A 118 (10), 1817-1825, 2014.

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