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(474) Production(s) de l'année 2018
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A conserved mechanism drives partition complex assembly on bacterial chromosomes and plasmids
Auteur(s): Debaugny Roxanne, Sanchez Aurore, Rech Jérôme, Labourdette Delphine, Dorignac J., Geniet F., Palmeri J., Parmeggiani A., Boudsocq François, Le Berre Véronique, Walter J.-C., Bouet Jean-Yves
(Article) Publié:
Molecular Systems Biology, vol. 14 p.e8516 (2018)
Texte intégral en Openaccess :
Ref HAL: hal-01926457_v1
PMID 30446599
DOI: 10.15252/msb.20188516
WoS: 000451579500003
Exporter : BibTex | endNote
14 Citations
Résumé: Chromosome and plasmid segregation in bacteria are mostly driven by ParABS systems. These DNA partitioning machineries rely on large nucleoprotein complexes assembled on centromere sites (parS). However, the mechanism of how a few parS-bound ParB proteins nucleate the formation of highly concentrated ParB clusters remains unclear despite several proposed physico-mathematical models. We discriminated between these different models by varying some key parameters in vivo using the plasmid F partition system. We found that ‘Nucleation & caging’ is the only coherent model recapitulating in vivo data. We also showed that the stochastic self-assembly of partition complexes (i) does not directly involve ParA, (ii) results in a dynamic structure of discrete size independent of ParB concentration, and (iii) is not perturbed by active transcription but is by protein complexes. We refined the ‘Nucleation & Caging’ model and successfully applied it to the chromosomally-encoded Par system of Vibrio cholerae, indicating that this stochastic self-assembly mechanism is widely conserved from plasmids to chromosomes.
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Multiwall MoS2 tubes as optical resonators
Auteur(s): Kazanov Dmitrii, Poshakinskiy A. V., Davydov V Yu, Smirnov A.N., Eliseyev A., Kirilenko D.A., Remskar M., Fathipour S, Mintairov A, Seabaugh A, Gil B., Shubina T.
(Article) Publié:
Applied Physics Letters, vol. 113 p.101106 (2018)
Ref HAL: hal-01871322_v1
DOI: 10.1063/1.5047792
WoS: WOS:000444037000006
Exporter : BibTex | endNote
27 Citations
Résumé: We study the optical properties of MoS2 nanotubes (NTs) with walls comprising dozens of monolayers. We reveal strong peaks in micro-photoluminescence (l-PL) spectra when detecting the light polarized along the NT axis. We develop a model describing the optical properties of the nanotubes acting as optical resonators which support the quantization of whispering gallery modes inside the NT wall. The experimental observation of the resonances in l-PL allows one to use them as a contactless method of the estimation of the wall width. Our findings open a way to use such NTs as polarization-sensitive components of nanophotonic devices.
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The Static and Dynamic Properties of Liquids and Disordered Systems
Auteur(s): Kob W.
Conférence invité: 2018 Summer School on Soft Matter and Biophysics (Shanghai, CN, 2018-07-01)
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Fracture of Sodium-Silicate Glasses: Insights from computer simulations
Auteur(s): Kob W.
Conférence invité: 7th International Congress on Ceramics (Iguacu Falls, BR, 2018-06-17)
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On the effect of local sample slope during modulus measurements by contact-resonance atomic force microscopy
Auteur(s): Heinze K., Arnould Olivier, Delenne Jean-Yves, Lullien-Pellerin V., Ramonda M., George M.
(Article) Publié:
Ultramicroscopy, vol. 194 p.78 - 88 (2018)
Texte intégral en Openaccess :
Ref HAL: hal-01869770_v1
DOI: 10.1016/j.ultramic.2018.07.009
WoS: 000450281700010
Exporter : BibTex | endNote
1 Citation
Résumé: Contact-resonance atomic force microscopy (CR-AFM) is of great interest and very valuable for a deeper understanding of the mechanics of biological materials with moduli of at least a few GPa. However, sample surfaces can present a high topography range with significant slopes, where the local angle can be as large as ± 50°. The non-trivial correlation between surface slope and CR-frequency hinders a straightforward interpretation of CR-AFM indentation modulus measurements on such samples. We aim to demonstrate the significant influence of the surface slope on the CR-frequency that is caused by the local angle between sample surface and the AFM cantilever and present a practical method to correct the measurements. Based on existing analytical models of the effect of the AFM set-up's intrinsic cantilever tilt on CR-frequencies, we compute the non-linear variation of the first two (eigen)modes CR-frequency for a large range of surface angles. The computations are confirmed by CR-AFM experiments performed on a curved surface. Finally, the model is applied to directly correct contact modulus measurements on a durum wheat starch granule as an exemplary sample.
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Selection of hexagonal buckling patterns by the elastic Rayleigh-Taylor instability
Auteur(s): Chakrabarti Aditi, Mora S., Richard Franck, Phou T., Fromental J.-M., Pomeau Yves, Audoly Basile
(Article) Publié:
Journal Of The Mechanics And Physics Of Solids, vol. 121 p.234 - 257 (2018)
Texte intégral en Openaccess :
Ref HAL: hal-01869797_v1
DOI: 10.1016/j.jmps.2018.07.024
WoS: 000446291200012
Exporter : BibTex | endNote
11 Citations
Résumé: We investigate the non-linear buckling patterns produced by the elastic Rayleigh-Taylor instability in a hyper-elastic slab hanging below a rigid horizontal plane, using a combination of experiments, weakly non-linear expansions and numerical simulations. Our experiments reveal the formation of hexagonal patterns through a discontinuous transition. As the unbuckled state is transversely isotropic, a continuum of linear modes become critical at the first bifurcation load: the critical wavevectors form a circle contained in a horizontal plane. Using a weakly non-linear post-bifurcation expansion, we investigate how these linear modes cooperate to produce buckling patterns: by a mechanism documented in other transversely isotropic structures, three-modes coupling make the unbuckled configuration unstable with respect to hexagonal patterns by a transcritical bifurcation. Stripe and square patterns are solutions of the post-bifurcation expansion as well but they are unstable near the threshold. These analytical results are confirmed and complemented by numerical simulations.
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