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Reversible photoregulation of G-quadruplex DNA structures by non-covalent azobenzene derivatives
No full textInternational audienceG-quadruplexes (G4) are non-canonical DNA structures involved in important cell regulatory functions associated with their folding mechanism. The design of small ligands capable of modulating their formation/stabilization is therefore of growing interest for the development of new anti-cancer therapies. In particular, the reversible control of G4s using bistable photoswitches offers promising perspectives for applications in photopharmacology and DNA nanotechnology, but remains largely unexploited [1]. It has long been demonstrated that the folding/unfolding of human telomeric (HT) G4 sequences can be induced by azobenzene-derived photoswitches [2]. However, the dynamics and mechanisms underlying these processes have never been investigated. Here we present a comprehensive study of complexes made of non-covalent azobenzenes bearing quaternary ammonium substituents (AZO) with different G4 sequences, by using a combination of stationary and time-resolved optical and chiroptical spectroscopic methods. This study revealed a non-cooperative binding mode of AZO with HT G4 sequences of the type 5'-GGG(TTAGGG)3-3' and the thrombin-binding aptamer G4 sequence, 5'-GGTTGGTGTGGTTGG-3' (TBA), in the absence of physiological cations. The binding of AZO to DNA induces the formation of parallel G4 topologies that can be reversibly unfolded under UV/visible excitation without noticeable fatigue. Femtosecond transient absorption measurements show that the isomerization of AZO is slowed by a factor of 4 in the presence of G4 (62ps vs. 16ps), while millisecond time-resolved circular dichroism provides evidence that G4 unfolding takes place within a few tens of milliseconds [3]
Supercritical CO2 extraction of solid-state cultivation fungus producing azaphilone polyketides
No full textInternational audienceSupercritical Fluid Extraction (SFE) methods dedicated to microorganisms specialized metabolites are very scarce in the literature and limited to liquid cultivation. We proposed here a new sample preparation method to achieve SFE of specialized metabolites from solid-state cultivation. SFE parameters, including CO2 pressure, temperature of extraction cell and percentage of co-solvent, were optimized in the case of solid-state cultures of Penicillium sclerotiorum SNB-CN111, a filamentous fungus producing azaphilone pigments. The metabolic composition of the extracts was then analyzed by reverse-phase liquid chromatography coupled to electrospray ionization and tandem mass spectrometry in data dependent acquisition mode. The resulting molecular networks generated by MetGem software allowed the annotation of the extracted metabolites in the different conditions, confirming the enrichment of fractions according to the polarity of azaphilone subfamilies. First, the 100% CO2 fraction a yield ten times higher than hexane maceration The optimization of SFE method led to an extraction yield twice as high as ethyl acetate maceration when mixing CO2 with ethanol and, indicating that CO2/ethanol SFE is more environmentally-friendly and efficient than standard maceration methods for the extraction of azaphilones from solid-state fermentation.</div
Storms and convection on Uranus and Neptune: impact of methane abundance revealed by a 3D cloud-resolving model
No full textInternational audienceContext. Uranus and Neptune have atmospheres dominated by molecular hydrogen and helium. In the upper troposphere (between 0.1 and 10 bars), methane is the third main molecule and condenses, yielding a vertical gradient in CH 4 . This condensable species being heavier than H 2 and He, the resulting change in mean molecular weight due to condensation comes as a factor countering convection, traditionally considered as ruled by temperature only. It makes both dry and moist convection more difficult to start. As observations also show latitudinal variations in methane abundance, one can expect different vertical gradients from one latitude to another. Aims. In this paper, we investigate the impact of this methane vertical gradient and the different shapes it can take, on the atmospheric regimes, especially on the formation and inhibition of moist convective storms in the troposphere of ice giants. Methods. We develop a 3D cloud-resolving model to simulate convective processes at the required scale. This model is nonhydrostatic and includes the effect of the mean molecular weight variations associated with condensation. Results. Using our simulations, we conclude that typical velocities of dry convection in the deep atmosphere are rather low (of the order of 1 m/s) but sufficient to sustain upward methane transport, and that moist convection at methane condensation level is strongly inhibited. Previous studies derived an analytical criterion on the methane vapor amount above which moist convection should be inhibited in saturated environments. In ice giants, this criterion yields a critical methane abundance of 1.2% at 80 K (this corresponds approximately to the 1 bar level). We first validate this analytical criterion numerically. We then show that this critical methane abundance governs the inhibition and formation of moist convective storms, and we conclude that the intensity and intermittency of these storms should depend on the methane abundance and saturation. -In the regions where CH 4 exceeds this critical abundance in the deep atmosphere (at the equator and the middle latitudes on Uranus, and all latitudes on Neptune), a stable layer almost entirely saturated with methane develops at the condensation level. In this layer, moist convection is inhibited, ensuring stability. Only weak moist convective events can occur above this layer, where methane abundance becomes lower than the critical value. The inhibition of moist convection prevents strong drying and maintains high relative humidity, which favors the frequency of these events. -In the regions where CH 4 remains below this critical abundance in the deep atmosphere (possibly at the poles on Uranus), there is no such layer. More powerful storms can form, but they are also a bit rarer. Conclusions. In ice giants, dry convection is weak, and moist convection is strongly inhibited. However, when enough methane is transported upwards, through dry convection and turbulent diffusion, sporadic moist convective storms can form. These storms should be more frequent on Neptune than on Uranus, because of Neptune's internal heat flow and larger methane abundance. Our results can explain the observed sporadicity of clouds in ice giants and can help us guide future observations to test the conclusions of this work
Modelling of atmospheric concentrations of fungal spores: a 2-year simulation over France using CHIMERE
No full textInternational audienceFungal spore organic aerosol emissions have been recognised as a significant source of particulate matter as PM10; however, they are not widely considered in current air quality models. In this work, we have implemented the parameterisation of fungal spore organic aerosol (OA) emissions introduced by Heald and Spracklen (2009) (H&S) and further modified by Hoose et al. (2010) in the CHIMERE regional chemistry-transport model. This simple parameterisation is based on two variables, leaf area index (LAI) and specific humidity. We have validated the geographical and temporal representativeness of this parameterisation on a large scale by using yearly polyol observations and primary biogenic organic aerosol factors from positive matrix factorisation (PMF) analysis at 11 French measurement sites. For a group of sites in northern and eastern France, the seasonal variation of fungal spore emissions, displaying large summer and small winter values, is correctly depicted. However, the H&S parameterisation fails to capture fungal spore concentrations for a smaller group of Mediterranean sites with less data availability in terms of both absolute values and seasonal variability, leading to strong negative biases, especially during the autumn and winter seasons. Two years of CHIMERE simulations with the H&S parameterisation have shown a significant contribution of fungal spore OA to PM10 mass, which is lower than 10 % during winter and reaches up to 20 % during summer in high-emission zones, especially over large forested areas. In terms of contributions to organic matter (OM) concentrations, the simulated fungal spore contribution in autumn is as high as 40 % and reaches at most 30 % of the OM for the other seasons. As a conclusion, the fungal spore OA contribution to the total OM concentrations is shown to be substantial enough to be considered a major PM10 fraction and should then be included in state-of-the-art chemistry-transport models
Electronic excitation spectra of molecular hydrogen in phase I from quantum Monte Carlo and many-body perturbation methods
No full textInternational audienceWe study the electronic excitation spectra in solid molecular hydrogen (phase I) at ambient temperature and 5to 90-GPa pressures using quantum Monte Carlo methods and many-body perturbation theory. In this range, the system changes from a wide-gap molecular insulator to a semiconductor, altering the nature of the excitations from localized to delocalized. Computed gaps and spectra agree with experiments, proving the ability to predict accurately band gaps of many-body systems in the presence of nuclear quantum and thermal effects
Glass for photonics: insight in the glass properties obtained under laser fs writing via point defects analysis
No full textInternational audiencePhotonics is becoming a key enable technology for the future. In particular, the ability to use direct laser writing for shaping and inscribing functionality in glass material has open a way for the versatile production of multi-scale subwavelength photonic architectures..
Measurement of prompt and production in collisions at TeV
No full textInternational audienceThe production of prompt and mesons is studied in proton-lead collisions at a centre-of-mass energy of TeV. The data sample corresponding to an integrated luminosity of is collected by the LHCb experiment at the LHC. The differential production cross-sections are measured using and candidates with transverse momentum in the range of and rapidities in the ranges of and in the nucleon-nucleon centre-of-mass system. For both particles, the nuclear modification factor and the forward-backward production ratio are determined. These results are compared with theoretical models that include initial-state nuclear effects. In addition, measurements of the cross-section ratios between , and mesons are presented, providing a baseline for studying the charm hadronization in lead-lead collisions at LHC energies
Socioeconomic agents as active matter in nonequilibrium Sakoda-Schelling models
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Probing a scale dependent gravitational slip with galaxy strong lensing systems
No full textInternational audienceObservations of galaxy-scale strong gravitational lensing systems enable unique tests of departures from general relativity at the kpc-Mpc scale. In this work, the gravitational slip parameter , measuring the amplitude of a hypothetical fifth force, is constrained using 130 elliptical galaxy lens systems. We implement a lens model with a power-law total mass density and a deprojected De Vaucouleurs luminosity density, favored over a power-law luminosity density. To break the degeneracy between the lens velocity anisotropy, , and the gravitational slip, we introduce a new prior on the velocity anisotropy based on recent dynamical data. For a constant gravitational slip, we find in agreement with general relativity at the 68% confidence level. Introducing a Compton wavelength , effectively screening the fifth force at small and large scales, the best fit is obtained for Mpc and . A local minimum is found at Mpc and . We conclude that there is no evidence in the data for a significant departure from general relativity and that using accurate assumptions and having good constraints on the lens galaxy model is key to ensure reliable constraints on the gravitational slip
On a multi-dimensional McKean-Vlasov SDE with memorial and singular interaction associated to the parabolic-parabolic Keller-Segel model
No full text23 pages, to be publishedInternational audienceIn this work we firstly prove the well-posedness of the non-linear martingale problem related to a McKean-Vlasov stochastic differential equation with singular interaction kernel in for . The particularity of our setting is that the McKean-Vlasov process we study interacts at each time with all its past time marginal laws by means of a singular space-time kernel. Secondly, we prove that our stochastic process is a probabilistic interpretation for the parabolic-parabolic Keller-Segel system in . We thus obtain a well-posedness result to the latter under explicit smallness condition on the parameters of the model