DJ-1 interacts with and regulates paraoxonase-2, an enzyme critical for neuronal survival in response to oxidative stress.

Loss-of-function mutations in DJ-1 (PARK7) gene account for about 1% of all familial Parkinson's disease (PD). While its physiological function(s) are not completely clear, DJ-1 protects neurons against oxidative stress in both in vitro and in vivo models of PD. The molecular mechanism(s) through which DJ-1 alleviates oxidative stress-mediated damage remains elusive. In this study, we identified Paraoxonase-2 (PON2) as an interacting target of DJ-1. PON2 activity is elevated in response to oxidative stress and DJ-1 is crucial for this response. Importantly, we showed that PON2 deficiency hypersensitizes neurons to oxidative stress induced by MPP+ (1-methyl-4-phenylpyridinium). Conversely, over-expression of PON2 protects neurons in this death paradigm. Interestingly, PON2 effectively rescues DJ-1 deficiency-mediated hypersensitivity to oxidative stress. Taken together, our data suggest a model by which DJ-1 exerts its antioxidant activities, at least partly through regulation of PON2

Structure, electrochemical properties and functionalization of amorphous CN films deposited by femtosecond pulsed laser ablation

Amorphous carbon nitride (a-C:N) material has attracted much attention in research and development. Recently, it has become a more promising electrode material than conventional carbon based electrodes in electrochemical and biosensor applications. Nitrogen containing amorphous carbon (a-C:N) thin films have been synthesized by femtosecond pulsed laser deposition (fs-PLD) coupled with plasma assistance through Direct Current (DC) bias power supply. During the deposition process, various nitrogen pressures (0 to 10 Pa) and DC bias (0 to ¿ 350 V) were used in order to explore a wide range of nitrogen content into the films. The structure and chemical composition of the films have been studied by using Raman spectroscopy, electron energy-loss spectroscopy (EELS) and high-resolution transmission electron microscopy (HRTEM). Increasing the nitrogen pressure or adding a DC bias induced an increase of the N content, up to 21 at.%. Nitrogen content increase induces a higher sp2 character of the film. However DC bias has been found to increase the film structural disorder, which was detrimental to the electrochemical properties. Indeed the electrochemical measurements, investigated by cyclic voltammetry (CV), demonstrated that a-C:N film with moderate nitrogen content (10 at.%) exhibited the best behavior, in terms of reversibility and electron transfer kinetics. Electrochemical grafting from diazonium salts was successfully achieved on this film, with a surface coverage of covalently bonded molecules close to the dense packed monolayer of ferrocene molecules. Such a film may be a promising electrode material in electrochemical detection of electroactive pollutants on bare film, and of biopathogen molecules after surface grafting of the specific affinity receptor.This work is produced with the financial support of the Future Program Lyon Saint-Etienne (PALSE) from the University of Lyon (ANR-11-IDEX-0007), under the “Investissements d'Avenir” program managed by the National Agency Research (ANR)

A Collaborative Filtering Approach for Protein-Protein Docking Scoring Functions

A protein-protein docking procedure traditionally consists in two successive tasks: a search algorithm generates a large number of candidate conformations mimicking the complex existing in vivo between two proteins, and a scoring function is used to rank them in order to extract a native-like one. We have already shown that using Voronoi constructions and a well chosen set of parameters, an accurate scoring function could be designed and optimized. However to be able to perform large-scale in silico exploration of the interactome, a near-native solution has to be found in the ten best-ranked solutions. This cannot yet be guaranteed by any of the existing scoring functions

Nano-Architecture of nitrogen-doped graphene films synthesized from a solid CN source

New synthesis routes to tailor graphene properties by controlling the concentration and chemical configuration of dopants show great promise. Herein we report the direct reproducible synthesis of 2-3% nitrogen-doped ‘few-layer’ graphene from a solid state nitrogen carbide a-C:N source synthesized by femtosecond pulsed laser ablation. Analytical investigations, including synchrotron facilities, made it possible to identify the configuration and chemistry of the nitrogen-doped graphene films. Auger mapping successfully quantified the 2D distribution of the number of graphene layers over the surface, and hence offers a new original way to probe the architecture of graphene sheets. The films mainly consist in a Bernal ABA stacking three-layer architecture, with a layer number distribution ranging from 2 to 6. Nitrogen doping affects the charge carrier distribution but has no significant effects on the number of lattice defects or disorders, compared to undoped graphene synthetized in similar conditions. Pyridinic, quaternary and pyrrolic nitrogen are the dominant chemical configurations, pyridinic N being preponderant at the scale of the film architecture. This work opens highly promising perspectives for the development of self-organized nitrogen-doped graphene materials, as synthetized from solid carbon nitride, with various functionalities, and for the characterization of 2D materials using a significant new methodology

Methods to Determine Interaction Interfaces Between β-Arrestins and Their Protein Partners

International audienceβ-arrestins are so-called hub proteins: they make complexes with many different partners, assembling functional complexes, and thereby fulfilling their biological function. The importance of this process in G protein-coupled receptor (GPCR) signalling has been fully demonstrated for many different receptors. For direct interactions, determining the interface regions, on β-arrestins and on the partners, is crucial for understanding the function of the complex. Indeed, this brings information on which proteins can interact simultaneously with β-arrestins, or on the contrary, which partners are exclusive. We present here a method in two steps: protein-protein docking allows finding a limited number of peptides predicted to be involved in the interaction; and then experimental that might be used for validating the prediction. Keywords Protein complex β-arrestin partners Interface region Protein-protein docking Running title Interfaces between b-arrestins and their partner

Pyridinic dominance nitrogen doped graphene by femtosecond pulsed laser deposition

International audienceCarbon-based materials represent an attractive prospective in fuel cell, electrochemical and biosensors applications [1]. Recently, nitrogen doped carbon materials have raised attention in research and development to enhance their practical applications. Especially, the direct controllable nitrogen doping in graphene synthesis routes have been an attracting area of research in catalysis and sensor applications [2,3]. Here, we present the direct growth of N doped graphene from ultrashort-pulsed laser deposition technique, based on previous works related to direct synthesis of graphene [4]. The N doped graphene has been synthesized by femtosecond pulsed laser deposition and characterized by different characterization techniques to study microstructural, surface morphology and chemical bonding information. The Multi-wavelength Raman spectroscopy confirms the doping in graphene network. The nitrogen doping in graphene decreases the 2D band intensity and the correlation length. The Raman mapping has confirmed the homogenous doping of nitrogen in the graphene network. By doping, the G peak is blue shifted by 4 cm-1 and the 2D peak is red shifted by 5 cm-1; which corresponds to the n-type doping behaviour and could open a bandgap in the graphene. The surface morphology has been studied by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The films shows the layered type structures and the low roughness values were estimated in both graphene and N doped graphene. The chemical composition and bonding have been studied by X-ray Photoelectron Spectroscopy (XPS), the nitrogen doping was estimated 3 at.%. The C1s spectra shifted to higher binding energy and the N1s spectra revealed three bonding structures, which are assigned to pyridinic-N, pyrrolic-N and graphitc-N type. The pyridinic-N dominance is high in our N doped graphene. The pyridinic-N dominance N doped graphene is attractive as a catalyst in Oxygen Reduction Reactions (ORR) to enhance their applications in fuel cells and electrochemical sensors. Compared to other carbon-based electrodes, N doped graphene will be a better electrode in electrochemical sensors. It can be used for the detection of hazardous pollutants and bio-pathogens at low concentrations.References(1) Fortgang, P.; Tite, T.; Barnier, V.; Zehani, N.; Maddi, C.; Lagarde, F.; Loir, A.-S.; Jaffrezic-Renault, N.; Donnet, C.; Garrelie, F.; et al. Robust Electrografting on Self-Organized 3D Graphene Electrodes. ACS Appl. Mater. Interfaces 2016, 8, 1424–1433.(2) Wu, J.; Ma, L.; Yadav, R. M.; Yang, Y.; Zhang, X.; Vajtai, R.; Lou, J.; Ajayan, P. M. Nitrogen-Doped Graphene with Pyridinic Dominance as a Highly Active and Stable Electrocatalyst for Oxygen Reduction. ACS Appl. Mater. Interfaces 2015, 7, 14763–14769.(3) Wang, Y.; Shao, Y.; Matson, D. W.; Li, J.; Lin, Y. Nitrogen-Doped Graphene and Its Application in Electrochemical Biosensing. ACS Nano 2010, 4, 1790–1798.(4) Tite, T.; Donnet, C.; Loir, A.-S.; Reynaud, S.; Michalon J.-Y.; Vocanson, F.; Garrelie, F.; Graphene-based textured surface by pulsed laser deposition as a robust platform forsurface enhanced Raman scattering applications. Applied Physics Letters 104 (2014) 041912-1 – 0419012-4

Thermally activated resonant grating using a vanadium dioxide waveguide

International audienceIn this work, we report on the design of a one-dimensional subwavelength resonant grating comprised of a fused silica substrate and a bi-layer waveguide, consisting of a solgel synthetized anatase TiO 2 layer followed by a thin VO 2 layer that is applied using pulsed laser deposition and rapid thermal annealing. A TE waveguide mode is excited under normal incidence in the VO 2 /TiO 2 bi-layer via a positive photoresist based grating printed on top, leading to high resonant reflection at room temperature. Increasing the temperature to about 68°C causes the VO 2 to undergo a dielectric to metallic transition accompanied by optical modifications in the IR region, canceling the resonance effect. This thermally triggered absorber/emitter tunable configuration enabling the on and off switching of optical resonant excitation in a reversible manner is proposed for passive Q-switching self-protecting devices for high power lasers in the IR wavelength range. Modeling of the optimized temperature dependent resonant waveguide and preliminary experimental results are presented