Publications

2022

• Fundamental Processes in Flavoprotein Photochemistry
  
  • Zhuang Bo
  , 2022. Flavins are derivatives of vitamin B2 that form a highly versatile group of chromophores found in a large variety of enzymes and photoreceptor proteins. They can adopt three different redox states with various protonation states, leading to at least five physiologically relevant forms, with distinct electronic absorption spectra. Despite the diverse photophysical properties of the flavin cofactors, there are only very few natural photo-responsive flavoproteins. The vast majority of flavoproteins perform non-light-driven physiological functions (“non-photoactive”), although ultrafast, reversible photoinduced redox reactions between flavins and surrounding residues still widely occur in these systems, which can be viewed as photo-protective “self-quenching”. The past few decades have seen a blooming in the study of flavoproteins for their photocatalytic and photo-biotechnological applications. Moreover, a newly emerging approach in the development of novel photocatalysts from canonical “non-photoactive” flavoenzymes is making use of the photochemistry of reduced flavins instead of the oxidized resting state. Furthermore, practical implications of photochemistry of yet different flavin species are envisaged, but a basic understanding of their mechanisms is still required. In this thesis, applying ultrafast absorption and fluorescence spectroscopy combined with molecular simulations and quantum chemistry approaches, a variety of fundamental photochemical processes in flavoproteins is investigated. First the photoreduction of oxidized flavins was revisited in a flavoprotein, ferredoxin-NADP+ oxidoreductase (FNR), with closely packed reactant configurations, allowing ultrafast formation of intermediate radical pairs. Combining experimental and modeling techniques allowed a detailed assessment of the influence of the environment on the spectral properties of both the anionic flavin and the cationic amino acid (tyrosine or tryptophan) radicals. We further investigated the photochemistry of protein-bound flavin species in different chemical states that are largely unexplored in the literature. It is demonstrated that photooxidation of anionic flavin radicals, which act as reaction intermediates in many biochemical reactions, efficiently occurs within ~100 fs in several flavoprotein oxidases. This process, effectively the reverse of the well-known photoreduction of oxidized flavin may constitute a universal decay pathway. The excited-state properties of fully reduced flavins were studied in several FNR systems where they are involved as functional intermediates, and compared with those in solution. Valuable information concerning their electronic structures and the flavin flexibility was obtained and compared with atomic simulations, with important catalytic implications. Finally, an unprecedented photo-dissociation phenomenon was revealed for a non-covalent charge transfer complex of flavin and a inhibitor in the flavoenzyme monomeric sarcosine oxidase. This process occurs on the timescale of a few hundred femtoseconds and can be attributed to a well-defined photoinduced isomerization of the inhibitor. Altogether, the described findings, which include the discovery of two hitherto undocumented photochemical processes in flavoproteins, expand the repertoire of photochemistry involving flavin cofactors. This work may open new avenues for the exploration of flavin photochemistry with ultimately possible practical implications as novel photocatalysts and optogenetic tools.
• Nouvelle méthode objective pour extraire une mesure quantitative de la transparence cornéenne à partir d’images résolues en profondeur
  
  • Bocheux Romain
  • Rivière Bathilde
  • Georgeon Cristina
  • Borderie Vincent
  • Pernot Pascal
  • Irsch Kristina
  • Plamann Karsten
  , 2022.
• Small photo-activatable molecules to control biological processes with light
  
  • Joyeux Benjamin
  • Gamet Antoine
  • Nay Bastien
  • Romero Stéphane
  • Marteau Maurine
  • Gautreau Alexis
  • Le Clainche Christophe
  • Changenet-Barret, Pascale
  • Perrin Auriane
  • Hache François
  • Réfrégiers Matthieu
  • Wien Frank
  , 2022.
• nAdder: A scale-space approach for the 3D analysis of neuronal traces
  
  • Phan Minh Son
  • Matho Katherine
  • Beaurepaire Emmanuel
  • Livet Jean
  • Chessel Anatole
  PLoS Computational Biology, PLOS, 2022, 18 (7), pp.e1010211. Tridimensional microscopy and algorithms for automated segmentation and tracing are revolutionizing neuroscience through the generation of growing libraries of neuron reconstructions. Innovative computational methods are needed to analyze these neuronal traces. In particular, means to characterize the geometric properties of traced neurites along their trajectory have been lacking. Here, we propose a local tridimensional (3D) scale metric derived from differential geometry, measuring for each point of a curve the characteristic length where it is fully 3D as opposed to being embedded in a 2D plane or 1D line. The larger this metric is and the more complex the local 3D loops and turns of the curve are. Available through the GeNePy3D open-source Python quantitative geometry library ( https://genepy3d.gitlab.io ), this approach termed nAdder offers new means of describing and comparing axonal and dendritic arbors. We validate this metric on simulated and real traces. By reanalysing a published zebrafish larva whole brain dataset, we show its ability to characterize different population of commissural axons, distinguish afferent connections to a target region and differentiate portions of axons and dendrites according to their behavior, shedding new light on the stereotypical nature of neurites’ local geometry. (10.1371/journal.pcbi.1010211)
  DOI : 10.1371/journal.pcbi.1010211
• Classification de cornées humaines saines et pathologiques par la quantification d’images SD-OCT cliniques
  
  • Vilbert Maëlle
  • Soubeiran Corentin
  • Memmi Benjamin
  • Georgeon Cristina
  • Borderie Vincent
  • Chessel Anatole
  • Plamann Karsten
  , 2022.
• Generation of Femtosecond Pulses
  
  • Bonvalet Adeline
  , 2022. Femtosecond lasers that appeared in the 1980s have since undergone numerous developments, while the scope of their applications has broadened. The first applications mainly exploited the duration of femtosecond pulses to improve the temporal resolution of spectroscopic experiments seeking to observe the very first steps of physical or biological processes. Since then, a wide range of applications have emerged, taking advantage of the remarkable properties of femtosecond pulses. The concentration of the energy, in space and time, has led to many scientific and industrial developments from material processing to new imaging techniques to name a few. The very particular characteristics of the spectrum of these pulses, equivalent to a frequency comb, have also revolutionized metrology. In this docu- ment, we present the properties of femtosecond pulses and provide some tools to describe them. We briefly present the central concept of spectral phase and discuss the key elements of a femtosecond laser cavity, namely modelocking and group velocity management. Some basic oscillator architectures are presented, keeping in mind that the world of femtosecond lasers is today extremely vast. (10.1051/978-2-7598-2719-0.c002)
  DOI : 10.1051/978-2-7598-2719-0.c002
• Construire un système d’imagerie 3D de tomographie par cohérence optique (OCT)
  
  • Latour Gaël
  Photoniques, EDP Sciences, 2022 (114), pp.21-25. Les étudiants ont la fierté de construire - de toute pièce - un microscope produisant des images tridimensionnelles (3D) d’objets transparents ou faiblement diffusants. Le projet laisse le temps aux étudiants de progresser en toute autonomie et de surmonter les difficultés théoriques et expérimentales rencontrées. Leur rigueur et leur ténacité sont récompensées par la beauté des films 3D qu’ils réalisent avec leur propre microscope. (10.1051/photon/202111421)
  DOI : 10.1051/photon/202111421
• G-quadruplex structure of the C. elegans telomeric repeat: a two tetrads basket type conformation stabilized by a non-canonical C–T base-pair
  
  • Marquevielle Julien
  • de Rache Aurore
  • Vialet Brune
  • Morvan Estelle
  • Mergny Jean-Louis
  • Amrane Samir
  Nucleic Acids Research, Oxford University Press, 2022, 50 (12), pp.7134-7146. The Caenorhabditis elegans model has greatly contributed to the understanding of the role of G-quadruplexes in genomic instability. The GGCTTA repeats of the C. elegans telomeres resemble the GGGTTA repeats of the human telomeres. However, the comparison of telomeric sequences (Homo sapiens, Tetrahymena, Oxytricha, Bombyx mori and Giardia) revealed that small changes in these repeats can drastically change the topology of the folded G-quadruplex. In the present work we determined the structure adopted by the C. elegans telomeric sequence d[GG(CTTAGG)3]. The investigated C. elegans telomeric sequence is shown to fold into an intramolecular two G-tetrads basket type G-quadruplex structure that includes a C–T base pair in the diagonal loop. This work sheds light on the telomeric structure of the widely used C. elegans animal model. (10.1093/nar/gkac523)
  DOI : 10.1093/nar/gkac523
• Photoswitching Behavior of Flavin–Inhibitor Complex in a Nonphotocatalytic Flavoenzyme
  
  • Zhuang Bo
  • Vos Marten
  Journal of the American Chemical Society, American Chemical Society, 2022, 144, pp.11569-11573. (10.1021/jacs.2c04763)
  DOI : 10.1021/jacs.2c04763
• Spatial distribution of air bubbles created by an imping water jet into a free water surface
  
  • Bense Alexandre
  • Lizee Mathieu
  • Guillet Thibault
  • Gallot Guilhem
  Emergent Scientist, EDP Sciences, 2022, 6 (3), pp.7. In this paper we study the rise to the surface, radial motion and disappearance of the bubbles created by a water jet pouring into a container, in particular their density at the surface as a function of the impact velocity. We first focus on their emergence radius at the surface which follows a log-normal distribution. Next, we establish experimentally a law relating the bubble velocity to the distance to the jet. We also investigate their disappearance, caused at low density mainly by explosion, and at high density predominantly by coalescence. Finally, we build an accurate model for the density of bubbles. (10.1051/emsci/2022001)
  DOI : 10.1051/emsci/2022001
• Conflits environnementaux en Afrique sahélienne : regards croisés sur les aires protégées sahéliennes camerounaises
  
  • Dzokom Alexis
  Sahel Nature Consulting Revue, Sahel Nature Consulting Revue (March 2025), 2022, 6 (1), pp.1-13. <div><p>En Afrique sahélienne, les aires protégées jouent un rôle central dans la conservation de la biodiversité. Cependant, leur mise en oeuvre suscite de nombreux conflits entre les communautés locales et les gestionnaires de l'environnement. Cette étude analyse les types, causes et conséquences des conflits environnementaux liés aux aires protégées sahéliennes camerounaises, en particulier dans le Parc National de Waza, la Réserve de Kalamaloué et les zones de chasse de l'Extrême-Nord. À partir d'une méthodologie qualitative basée sur des enquêtes de terrain, des entretiens semi-directifs et une revue documentaire, nous montrons que les conflits intercommunautaires (5,2 ±1,2) sont souvent exacerbés par l'exclusion des populations des ressources vitales(8,7 ±1,0), à l'inadéquation des politiques de conservation (7,9±1,4), et à l'influence des dynamiques climatiques et sécuritaires. L'analyse révèle aussi l'émergence d'initiatives communautaires et de mécanismes de gestion participative (5,9±1,9) encore embryonnaires. Les résultats soulignent la nécessité d'une gouvernance environnementale inclusive, tenant compte des réalités locales et des enjeux géopolitiques sahéliens.</p></div>
• High-throughput tuning of ovarian cancer spheroids for on-chip invasion assays
  
  • Chen Changchong
  • He Yong
  • Lopez Elliot
  • Carreiras Franck
  • Yamada Ayako
  • Schanne-Klein Marie-Claire
  • Lambert Ambroise
  • Chen Yong
  • Aimé Carole
  Micro and Nano Engineering, Elsevier, 2022, 15, pp.100138. We developed an invasion assay by using microfabricated culture devices. First, ovarian tumor spheroids were generated with a culture patch device consisting of an agarose membrane formed with a honeycomb microframe – the patch – and gelatin nanofiber backbone. By changing the dimensions of the honeycomb compartments we were able to control the number of cells and size of the spheroids. When the spheroids were placed on a patch coated with a thin membrane of fibrillary type I collagen, spheroid disruption was observed due to substrate induced cell migration. This process is straightforward and should be applicable to other cancer types, as well as assays under microfluidic conditions, thereby holding the potential for use in tumor modeling and anti-cancer drug development. (10.1016/j.mne.2022.100138)
  DOI : 10.1016/j.mne.2022.100138
• Erratum: Electric field measurements in plasmas: how focusing strongly distorts the E-FISH signal (2020 Plasma Sources Sci. Technol. 29 125002)
  
  • Chng Tat Loon
  • Starikovskaia Svetlana
  • Schanne-Klein Marie-Claire
  Plasma Sources Science and Technology, IOP Publishing, 2022, 31 (5), pp.059601. (10.1088/1361-6595/ac601d)
  DOI : 10.1088/1361-6595/ac601d
• Efficient Biocatalytic System for Biosensing by Combining Metal–Organic Framework (MOF)-Based Nanozymes and G-Quadruplex (G4)-DNAzymes
  
  • Mao Xuanxiang
  • He Fangni
  • Qiu Dehui
  • Wei Shijiong
  • Luo Rengan
  • Chen Yun
  • Zhang Xiaobo
  • Lei Jianping
  • Monchaud David
  • Mergny Jean-Louis
  • Ju Huangxian
  • Zhou Jun
  Analytical Chemistry, American Chemical Society, 2022, 94 (20), pp.7295-7302. A high catalytic efficiency associated with a robust chemical structure are among the ultimate goals when developing new biocatalytic systems for biosensing applications. To get ever closer to these goals, we report here on a combination of metal-organic framework (MOF)-based nanozymes and a G-quadruplex (G4)-based catalytic system known as G4-DNAzyme. This approach aims at combining the advantages of both partners (chiefly, the robustness of the former and the modularity of the latter). To this end, we used MIL-53(Fe) MOF and linked it covalently to a G4-forming sequence (F3TC), itself covalently linked to its cofactor hemin. The resulting complex (referred to as MIL-53(Fe)/G4-hemin) exhibited exquisite peroxidase-mimicking oxidation activity and an excellent robustness (being stored in water for weeks). These properties were exploited to devise a new biosensing system based on a cascade of reactions catalyzed by the nanozyme (ABTS oxidation) and an enzyme, the alkaline phosphatase (or ALP, ascorbic acid 2-phosphate dephosphorylation). The product of the latter poisoning the former, we thus designed a biosensor for ALP (a marker of bone diseases and cancers), with a very low limit of detection (LOD, 0.02 U L-1), which is operative in human plasma samples. (10.1021/acs.analchem.2c00600)
  DOI : 10.1021/acs.analchem.2c00600
• Ultra-broadband, tunable mid-IR source based on enhanced-efficiency intrapulse difference-frequency generation
  
  • Bournet Quentin
  • Guichard Florent
  • Natile Michele
  • Zaouter Yoann
  • Joffre Manuel
  • Bonvalet Adeline
  • Pupeza I.
  • Hofer C.
  • Druon Frédéric
  • Hanna Marc
  • Georges Patrick
  , 2022, pp.SF4E.7. We report on an ultra-broadband mid-infrared source based on intrapulse difference-frequency-generation delivering 135 nJ, 50 fs-long pulses at 250 kHz repetition-rate. A bichromatic waveplate is used, enhancing the number of photons for the mid-infrared generation. (10.1364/CLEO_SI.2022.SF4E.7)
  DOI : 10.1364/CLEO_SI.2022.SF4E.7
• Objective assessment of corneal transparency in the clinical setting: Identification and correction of acquisition artifacts in SD-OCT images
  
  • Vilbert Maëlle
  • Bocheux Romain
  • Lama Hugo
  • Georgeon Cristina
  • Borderie Vincent
  • Pernot Pascal
  • Irsch Kristina
  • Plamann Karsten
  , 2022.
• Stabilization of a DNA aptamer by ligand binding
  
  • Santos Tiago
  • Lopes-Nunes Jéssica
  • Alexandre Daniela
  • Miranda André
  • Figueiredo Joana
  • Silva Micael
  • Mergny Jean-Louis
  • Cruz Carla
  Biochimie, Elsevier, 2022, S0300-9084 (22), pp.00114-6. G-rich aptamers such as AS1411 are small oligonucleotides that present several benefits comparatively to monoclonal antibodies, since they are easier to manufacture and store, have small size and do not stimulate an immune response. We analyzed AT11-B1, a modified sequence of AT11 (itself a modified version of AS1411), in which one thymine was removed from the bulge region. We studied G-quadruplex (G4) formation/stabilization using PhenDC3, PDS, BRACO-19, TMPyP4 and 360A ligands by different biophysical techniques, namely circular dichroism (CD), Förster resonance energy transfer (FRET-melting) and nuclear magnetic resonance (NMR). The CD spectra showed that AT11-B1 adopts a predominant G4 of parallel topology when the buffer contains KCl or when ligands are added. PhenDC3 induced a ΔTm of 30 °C or more of the G4 structure as shown by CD- and FRET-melting experiments. The ligands demonstrate high affinity for AT11-B1 G4 and the NMR studies revealed that the AT11-B1 G4 involves four G-tetrad layers. The in silico studies suggest that all ligands bind AT11-B1 G4, namely, by stacking interactions, except PDS that may bind to the loop/groove interface. In addition, molecular dynamics simulations revealed that nucleolin (NCL) interacts with the AT11-B1 G4 structure through the RNA binding domain (RBD) 2 and the 12-residue linker between RBD1,2. Moreover, AT11-B1 G4 was internalized into a NCL-positive tongue squamous cell carcinoma cell line. In a nutshell, this study may help the identification of the ligands scaffolds to bind and stabilize AT11-B1, improving the targeting towards NCL that is overexpressed in cancer cells. (10.1016/j.biochi.2022.05.002)
  DOI : 10.1016/j.biochi.2022.05.002
• Molecular insights into the role of heme in the transcriptional regulatory system AppA/PpsR.
  
  • Kapetanaki Sofia
  • Fekete Zsuzsanna
  • Dorlet Pierre
  • Vos Marten
  • Liebl Ursula
  • Lukacs Andras
  Biophysical Journal, Biophysical Society, 2022, 121, pp.2135-2151. Heme has been shown to have a crucial role in the signal transduction mechanism of the facultative photoheterotrophic bacterium Rhodobacter sphaeroides. It interacts with the transcriptional regulatory complex AppA/PpsR, in which AppA and PpsR function as the antirepressor and repressor, respectively, of photosynthesis gene expression. The mechanism, however, of this interaction remains incompletely understood. In this study, we combined electron paramagnetic resonance (EPR) spectroscopy and Förster resonance energy transfer (FRET) to demonstrate the ligation of heme in PpsR with a proposed cysteine residue. We show that heme binding in AppA affects the fluorescent properties of the dark-adapted state of the protein, suggesting a less constrained flavin environment compared with the absence of heme and the light-adapted state. We performed ultrafast transient absorption measurements in order to reveal potential differences in the dynamic processes in the full-length AppA and its heme-binding domain alone. Comparison of the CO-binding dynamics demonstrates a more open heme pocket in the holo-protein, qualitatively similar to what has been observed in the CO sensor RcoM-2, and suggests a communication path between the blue-light-using flavin (BLUF) and sensing containing heme instead of cobalamin (SCHIC) domains of AppA. We have also examined quantitatively the affinity of PpsR to bind to individual DNA fragments of the puc promoter using fluorescence anisotropy assays. We conclude that oligomerization of PpsR is initially triggered by binding of one of the two DNA fragments and observe a ∼10-fold increase in the dissociation constant Kd for DNA binding upon heme binding to PpsR. Our study provides significant new insight at the molecular level on the regulatory role of heme that modulates the complex transcriptional regulation in R. sphaeroides and supports the two levels of heme signaling, via its binding to AppA and PpsR and via the sensing of gases like oxygen. (10.1016/j.bpj.2022.04.031)
  DOI : 10.1016/j.bpj.2022.04.031
• Tunable, Broadband Mid-Infrared Source Based on Amplified Intrapulse Difference Frequency Generation
  
  • Bournet Quentin
  • Guichard François
  • Natile Michele
  • Zaouter Yoann
  • Joffre M.
  • Bonvalet A.
  • Druon Frédéric
  • Hanna Marc
  • Georges Patrick
  , 2022.
• Thiosugar naphthalene diimide conjugates: G-quadruplex ligands with antiparasitic and anticancer activity
  
  • Belmonte-Reche Efres
  • Benassi Alessandra
  • Peñalver Pablo
  • Cucchiarini Anne
  • Guédin Aurore
  • Mergny Jean Louis
  • Rosu Frèdèric
  • Gabelica Valerie
  • Freccero Mauro
  • Doria Filippo
  • Morales Juan Carlos
  European Journal of Medicinal Chemistry, Elsevier, 2022, 232, pp.114183. Glycosyl conjugation to drugs is a strategy being used to take advantage of glucose transporters (GLUT) overexpression in cancer cells in comparison with non-cancerous cells. Its extension to the conjugation of drugs to thiosugars tries to exploit their higher biostability when compared to O-glycosides. Here, we have synthesized a series of thiosugar naphthalene diimide conjugates as G-quadruplex ligands and have explored modifications of the amino sidechain comparing dimethyl amino and morpholino groups. Then, we studied their antiproliferative activity in colon cancer cells, and their antiparasitic activity in T. brucei and L. major parasites, together with their ability to bind quadruplexes and their cellular uptake and location. We observed higher toxicity for the sugar-NDI-NMe2 derivatives than for the sugar-NDI-morph compounds, both in mammalian cells and in parasites. Our experiments indicate that a less efficient binding to quadruplexes and a worse cellular uptake of the carb-NDI-morph derivatives could be the reasons for these differences. We found small variations in cytotoxicity between O-carb-NDIs and S-carb-NDIs, except against non-cancerous human fibroblasts MRC-5, where thiosugar-NDIs tend to be less toxic. This leads to a notable selectivity for β-thiomaltosyl-NDI-NMe212 (9.8 fold), with an IC50 of 0.3 μM against HT-29 cells. Finally, the antiparasitic activity observed for the carb-NDI-NMe2 derivatives against T. brucei was in the nanomolar range with a good selectivity index in the range of 30- to 69- fold. (10.1016/j.ejmech.2022.114183)
  DOI : 10.1016/j.ejmech.2022.114183
• Screening of Scaffolds for the Design of G-Quadruplex Ligands
  
  • Figueiredo Joana
  • Peitinho David
  • Cabral Campello Maria Paula
  • Oliveira Maria Cristina
  • Paulo António
  • Mergny Jean-Louis
  • Cruz Carla
  Applied Sciences, Multidisciplinary digital publishing institute (MDPI), 2022, 12, pp.2170. In the last decade, progress has been made in G-quadruplex (G4) ligands development, but for most compounds, the ligand binding mode is speculative or based on low resolution methods, with its discovery based on structure-based approaches. Herein, we report the synthesis of small (MW < 400 Da) heterocycle compounds, containing different aromatic scaffolds, such as phenyl, quinoline, naphthalene, phenanthroline and acridine moieties, in order to explore their stabilization effect towards different DNA G4s, such as those found in c-MYC, KRAS21 and VEGF promoters, 21G human telomeric motif and pre-MIR150. The fluorescence resonance energy transfer (FRET) melting assay indicates that the acridine moiety is the most active scaffold, followed by phenanthroline. The different scaffolds are promising in terms of drug-like properties and, in general, the IC50 values of the respective heterocycle compounds are lower in a cancer cell line, when compared with a normal cell line. The acridine derivative C5NH2 has the most favorable cytotoxic profile in terms of cell selectivity. (10.3390/app12042170)
  DOI : 10.3390/app12042170
• Intravital deep-tumor single-beam 3-photon, 4-photon, and harmonic microscopy
  
  • Bakker Gert-Jan
  • Weischer Sarah
  • Ferrer Ortas Júlia
  • Heidelin Judith
  • Andresen Volker
  • Beutler Marcus
  • Beaurepaire Emmanuel
  • Friedl Peter
  eLife, eLife Sciences Publication, 2022, 11, pp.e63776. Three-photon excitation has recently been demonstrated as an effective method to perform intravital microscopy in deep, previously inaccessible regions of the mouse brain. The applicability of 3-photon excitation for deep imaging of other, more heterogeneous tissue types has been much less explored. In this work, we analyze the benefit of high-pulse-energy 1 MHz pulse-repetition-rate infrared excitation near 1300 and 1700 nm for in-depth imaging of tumorous and bone tissue. We show that this excitation regime provides a more than 2-fold increased imaging depth in tumor and bone tissue compared to the illumination conditions commonly used in 2-photon excitation, due to improved excitation confinement and reduced scattering. We also show that simultaneous 3- and 4-photon processes can be effectively induced with a single laser line, enabling the combined detection of blue to far-red fluorescence together with second and third harmonic generation without chromatic aberration, at excitation intensities compatible with live tissue imaging. Finally, we analyze photoperturbation thresholds in this excitation regime and derive setpoints for safe cell imaging. Together, these results indicate that infrared high-pulse-energy low-repetition-rate excitation opens novel perspectives for intravital deep-tissue microscopy of multiple parameters in strongly scattering tissues and organs. (10.7554/eLife.63776)
  DOI : 10.7554/eLife.63776
• Live 3D imaging and mapping of shear stresses within tissues using incompressible elastic beads
  
  • Souchaud Alexandre
  • Boutillon Arthur
  • Charron Gaëlle
  • Asnacios Atef
  • Noûs Camille
  • David Nicolas
  • Graner François
  • Gallet François
  Development (Cambridge, England), Company of Biologists, 2022, 149 (4), pp.dev199765. To investigate the role of mechanical constraints in morphogenesis and development, we have developed a pipeline of techniques based on incompressible elastic sensors. These techniques combine the advantages of incompressible liquid droplets, which have been used as precise in situ shear stress sensors, and of elastic compressible beads, which are easier to tune and to use. Droplets of a polydimethylsiloxane mix, made fluorescent through specific covalent binding to a rhodamin dye, are produced by a microfluidics device. The elastomer rigidity after polymerization is adjusted to the tissue rigidity. Its mechanical properties are carefully calibrated in situ, for a sensor embedded in a cell aggregate submitted to uniaxial compression. The local shear stress tensor is retrieved from the sensor shape, accurately reconstructed through an active contour method. In vitro, within cell aggregates, and in vivo, in the prechordal plate of the zebrafish embryo during gastrulation, our pipeline of techniques demonstrates its efficiency to directly measure the three dimensional shear stress repartition within a tissue. (10.1242/dev.199765)
  DOI : 10.1242/dev.199765
• Portrait of a Family of Highly Stabilizing and Selective Guanine Quadruplex Platinum(II)‐Based Binders
  
  • Miron Caitlin
  • Chen Mickey
  • Mergny Jean‐louis
  • Petitjean Anne
  Chemistry - A European Journal, Wiley-VCH Verlag, 2022, 28 (7), pp.e202103839. The long-standing history of platinum coordination complexes in nucleic acid recognition attests to the unique suitability of such species for therapeutic applications. Here, we report the synthetic exploration and development of a family of di-imine ligands, and their platinum(II) complexes, elaborated on a 3-(2-pyridyl)-[1,2,4]triazolo[4,3-a]pyridine platform which, in its unsubstituted form, has recently been shown to display exceptional capabilities for guanine quadruplex (G4) targeting. The identification of facile, high-yielding synthetic methods for the derivatization of this platform for the incorporation of additional sites of interactions with guanine quadruplex loops and grooves, along with the optimization of platinum(II) complexation methods, are discussed. Gratifyingly, preliminary biophysical screening of this novel family of binders validates all but one family members as robust G4 binders and highlights enhanced selectivity for quadruplex versus duplex DNA compared to the parent compound. These results bear promise for practical developments based on this platform. (10.1002/chem.202103839)
  DOI : 10.1002/chem.202103839
• Highly Sensitive Biosensing Applications of a Magnetically Immobilizable Covalent G-Quadruplex-Hemin DNAzyme Catalytic System
  
  • Chen Yun
  • Qiu Dehui
  • Zhang Xiaobo
  • Liu Yuan
  • Cheng Mingpan
  • Lei Jianping
  • Mergny Jean-Louis
  • Ju Huangxian
  • Zhou Jun
  Analytical Chemistry, American Chemical Society, 2022, 94 (2212-2219), pp.acs.analchem.1c04842. (10.1021/acs.analchem.1c04842)
  DOI : 10.1021/acs.analchem.1c04842