Exploiting Physical Contacts for Robustness Improvement of a Dot-Painting Mission by a Micro Air Vehicle

In this paper we address the problem of dot painting on a wall by a quadrotor Micro Air Vehicle (MAV), using on-board low cost sensors (monocular camera and IMU) for localization. A method is proposed to cope with uncertainties on the initial positioning of the MAV with respect to the wall and to deal with walls composed of multiple segments. This method is based on an online estimation algorithm that makes use of information of physical contacts detected by the drone during the flight to improve the positioning accuracy of the painted dots. Simulation results are presented to assess quantitatively the efficiency of the proposed approaches

Loading of silica nanoparticles in block copolymer vesicles during polymerization-induced self-assembly: encapsulation efficiency and thermally-triggered release

Poly(glycerol monomethacrylate)-poly(2-hydroxypropyl methacrylate) diblock copolymer vesicles can be prepared in the form of concentrated aqueous dispersions via polymerization-induced self-assembly (PISA). In the present study, these syntheses are conducted in the presence of varying amounts of silica nanoparticles of approximately 18 nm diameter. This approach leads to encapsulation of up to hundreds of silica nanoparticles per vesicle. Silica has high electron contrast compared to the copolymer and its thermal stability enables quantification of the loading efficiency via thermogravimetric analysis. Encapsulation efficiencies can be obtained using disk centrifuge photosedimentometry, since the vesicle density increases at higher silica loadings while the mean vesicle diameter remains essentially unchanged. Small angle X-ray scattering (SAXS) is used to confirm silica encapsulation, since a structure factor is observed at q ~ 0.25 nm-1. A new two-population model provides satisfactory data fits to the SAXS patterns and allows the mean silica volume fraction within the vesicles to be determined. Finally, the thermo-responsive nature of the diblock copolymer enables thermally-triggered release of the encapsulated silica nanoparticles simply by cooling to 0-10 oC, which induces a morphological transition. These silica-loaded vesicles constitute a useful model system for understanding the encapsulation of globular proteins, enzymes or antibodies within block copolymer vesicles for potential biomedical applications. They may also serve as an active payload for self-healing hydrogels or repair of biological tissue. Finally, we also encapsulate a model globular protein, bovine serum albumin, and calculate its loading efficiency using fluorescence spectroscopy. Please click Additional Files below to see the full abstract

Hydration in Deep Eutectic Solvents Induces Non-monotonic Changes in the Conformation and Stability of Proteins

The preservation of labile biomolecules presents a major challenge in chemistry, and deep eutectic solvents (DESs) have emerged as suitable environments for this purpose. However, how the hydration of DESs impacts the behavior of proteins is often neglected. Here, we demonstrate that the amino acid environment and secondary structure of two proteins (bovine serum albumin and lysozyme) and an antibody (immunoglobulin G) in 1:2 choline chloride:glycerol and 1:2 choline chloride:urea follow a re-entrant behavior with solvent hydration. A dome-shaped transition is observed with a folded or partially folded structure at very low (40 wt % H2O) DES hydration, while protein unfolding increases between those regimes. Hydration also affects protein conformation and stability, as demonstrated for bovine serum albumin in hydrated 1:2 choline chloride:glycerol. In the neat DES, bovine serum albumin remains partially folded and unexpectedly undergoes unfolding and oligomerization at low water content. At intermediate hydration, the protein begins to refold and gradually retrieves the native monomer–dimer equilibrium. However, ca. 36 wt % H2O is required to recover the native folding fully. The half-denaturation temperature of the protein increases with decreasing hydration, but even the dilute DESs significantly enhance the thermal stability of bovine serum albumin. Also, protein unfolding can be reversed by rehydrating the sample to the high hydration regime, also recovering protein function. This correlation provides a new perspective to understanding protein behavior in hydrated DESs, where quantifying the DES hydration becomes imperative to identifying the folding and stability of proteinsA.S.F. acknowledges the Spanish Ministerio de Universidades for the awarded Maria Zambrano fellowship. Also, the research in this study was performed with financial support from Vinnova─Swedish Governmental Agency for Innovation Systems within the NextBioForm Competence Centre and from The Crafoord Foundation (grant #20190750). The authors thank the Institute Laue-Langevin for the awarded beamtime (8-03-1049)S

Self-assembly of short chain Poly-N-isopropylacrylamid (PNIPAM) induced by superchaotropic Keggin Polyoxometalates: from globules to sheets

We show here for the first time that short chain poly(N-isopropylacrylamide) (PNIPAM), one of the most famous thermoresponsive polymers, self-assembles in water to form (i) discrete nanometer-globules and (ii) micrometric sheets with nm-thickness upon addition of the well-known Keggin-type polyoxometalate (POM) H3PW12O40 (PW). The type of self-assembly is controlled by PW concentration: at low PW concentrations, PW adsorbs on PNIPAM chains to form globules consisting of homogeneously distributed PWs in PNIPAM droplets of several nm in size. Upon further addition of PW, a phase transition from globules to micrometric sheets is observed for PNIPAMs above a polymer critical chain length, between 18 and 44 repeating units. The thickness of the sheets is controlled by the PNIPAM chain length, here from 44 to 88 repeating units. The PNIPAM sheets are electrostatically stabilized PWs accumulated on each side of the sheets. The shortest PNIPAM chain with 18 repeating units produces PNIPAM/PW globules with 5 -20 nm size but no sheets. The PW/ PNIPAM self-assembly arises from a solvent mediated mechanism associated with the partial dehydration of PW and of the PNIPAM, which is related to the general propensity of POMs to adsorb on neutral hydrated surfaces. This effect, known as superchaotropy, is further highlighted by the significant increase in the lower critical solubilization temperature (LCST) of PNIPAM observed upon the addition of PW in the mM range. The influence of the POM nature on the self-assembly of PNIPAM was also investigated by using H4SiW12O40 (SiW) and H3PMo12O40 (PMo), i.e. changing the POM's charge density or polarizability in order to get deeper understanding on the role of electrostatics and polarizability in the PNIPAM self-assembly process. We show here that the superchaotropic behavior of POMs with PNIPAM polymers enables the formation and the shape control of supramolecular organic-inorganic hybrids

Loading of Silica Nanoparticles in Block Copolymer Vesicles during Polymerization-Induced Self-Assembly: Encapsulation Efficiency and Thermally Triggered Release

Poly(glycerol monomethacrylate)-poly(2-hydroxypropyl methacrylate) diblock copolymer vesicles can be prepared in the form of concentrated aqueous dispersions via polymerization-induced self-assembly (PISA). In the present study, these syntheses are conducted in the presence of varying amounts of silica nanoparticles of approximately 18 nm diameter. This approach leads to encapsulation of up to hundreds of silica nanoparticles per vesicle. Silica has high electron contrast compared to the copolymer which facilitates TEM analysis, and its thermal stability enables quantification of the loading efficiency via thermogravimetric analysis. Encapsulation efficiencies can be calculated using disk centrifuge photosedimentometry, since the vesicle density increases at higher silica loadings while the mean vesicle diameter remains essentially unchanged. Small angle X-ray scattering (SAXS) is used to confirm silica encapsulation, since a structure factor is observed at q ≈ 0.25 nm–1. A new two-population model provides satisfactory data fits to the SAXS patterns and allows the mean silica volume fraction within the vesicles to be determined. Finally, the thermoresponsive nature of the diblock copolymer vesicles enables thermally triggered release of the encapsulated silica nanoparticles simply by cooling to 0–10 °C, which induces a morphological transition. These silica-loaded vesicles constitute a useful model system for understanding the encapsulation of globular proteins, enzymes, or antibodies for potential biomedical applications. They may also serve as an active payload for self-healing hydrogels or repair of biological tissue. Finally, we also encapsulate a model globular protein, bovine serum albumin, and calculate its loading efficiency using fluorescence spectroscopy

Liquid – liquid phase separation morphologies in ultra-white beetle scales and a synthetic equivalent

Cyphochilus beetle scales are amongst the brightest structural whites in nature, being highly opacifying whilst extremely thin. However, the formation mechanism for the voided intra- scale structure is unknown. Here we report 3D x-ray nanotomography data for the voided chitin networks of intact white scales of Cyphochilus and Lepidiota stigma. Chitin-filling frac- tions are found to be 31 ± 2% for Cyphochilus and 34 ± 1% for Lepidiota stigma, indicating previous measurements overestimated their density. Optical simulations using finite- difference time domain for the chitin morphologies and simulated Cahn-Hilliard spinodal structures show excellent agreement. Reflectance curves spanning filling fraction of 5-95% for simulated spinodal structures, pinpoint optimal whiteness for 25% chitin filling. We make a simulacrum from a polymer undergoing a strong solvent quench, resulting in highly reflective ( 94%) white films. In-situ X-ray scattering confirms the nanostructure is formed through spinodal decomposition phase separation. We conclude that the ultra-white beetle scale nanostructure is made via liquid–liquid phase separation

Extracorporeal Membrane Oxygenation for Severe Acute Respiratory Distress Syndrome associated with COVID-19: An Emulated Target Trial Analysis.

RATIONALE: Whether COVID patients may benefit from extracorporeal membrane oxygenation (ECMO) compared with conventional invasive mechanical ventilation (IMV) remains unknown. OBJECTIVES: To estimate the effect of ECMO on 90-Day mortality vs IMV only Methods: Among 4,244 critically ill adult patients with COVID-19 included in a multicenter cohort study, we emulated a target trial comparing the treatment strategies of initiating ECMO vs. no ECMO within 7 days of IMV in patients with severe acute respiratory distress syndrome (PaO2/FiO2 <80 or PaCO2 ≥60 mmHg). We controlled for confounding using a multivariable Cox model based on predefined variables. MAIN RESULTS: 1,235 patients met the full eligibility criteria for the emulated trial, among whom 164 patients initiated ECMO. The ECMO strategy had a higher survival probability at Day-7 from the onset of eligibility criteria (87% vs 83%, risk difference: 4%, 95% CI 0;9%) which decreased during follow-up (survival at Day-90: 63% vs 65%, risk difference: -2%, 95% CI -10;5%). However, ECMO was associated with higher survival when performed in high-volume ECMO centers or in regions where a specific ECMO network organization was set up to handle high demand, and when initiated within the first 4 days of MV and in profoundly hypoxemic patients. CONCLUSIONS: In an emulated trial based on a nationwide COVID-19 cohort, we found differential survival over time of an ECMO compared with a no-ECMO strategy. However, ECMO was consistently associated with better outcomes when performed in high-volume centers and in regions with ECMO capacities specifically organized to handle high demand. This article is open access and distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives License 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/)

Etude physico-chimique de nouveaux tensioactifs fonctionnalisés complexants au comportement démixant thermoréversible (application à l'extraction de l'uranyle)

De nouveaux tensioactifs fonctionnalisés associant un bloc complexant dérivé d'acide aminé et un bloc tensioactif thermoréversible polyéthoxylé (CiEj) ont été synthétisés et étudiés. En solution aqueuse, ces molécules conservent les propriétés de tensioactif thermoréversible du bloc CiEj, et la propriété de complexation du cation uranyle par le ligand diamide.Le bloc complexant apporte une contribution hydrophile aux composés avec une augmentation de leur surface par tête. En solution aqueuse diluée, ces composés s auto-associent en micelles sphériques, caractérisées par diffusion de rayons X et de neutrons aux petits angles. A forte concentration, l auto-association conduit à des structures de courbures plus faibles que les CiEj précurseurs.Le complexe formé avec le nitrate d'uranyle en solution aqueuse a été caractérisé par RMN et spectrométrie de masse electrospray : il est de stœchiométrie 1:1 et possède deux ligands nitrate ; la constante de complexation associée, très faible, a été évaluée. L'effet de sels de nitrate à fortes concentrations a été étudié notamment avec LiNO3 utilisé pour déplacer l'équilibre de complexation. Les nitrates d'alcalins induisent des variations de point de trouble semblables pour les tensioactifs fonctionnalisés et les CiEj.La complexation du nitrate d uranyle provoque une diminution du point de trouble associée à une diminution de surface par tête. L effet diminue quand le volume polaire du CiEj précurseur augmente. Les tests d'extractions par point de trouble démontrent l'efficacité des tensioactifs fonctionnalisés et l'intérêt du couplage covalent d'un bloc complexant et d'un bloc tensioactif.New thermosensitive functionalized surfactants with metal-chelating properties have been developed and their physical-chemistry studied. They associate a polyethoxylated nonionic surfactant (CiEj) block and a amino-acid residue as a chelating group. Functionalization preserves both properties of the thermosensitive surfactant moiety and the chelating group, a diamide closed to uranyl ionophore.The complexing group participates to the polar head group of the surfactant, increasing the area per molecule. As a result, functionalized surfactants form spherical micelles when diluted in water, and the concentrated part of their phase diagrams exhibits structures having higher curvatures than the nonionic precursor CiEj.The structure of the uranyl - diamide complex has been elucidated by NMR and ESI-MS and is of the type UO2(NO3)2.L; the associated complexation constant, which is very low, has been evaluated by 1H NMR.A nitrate salt, LiNO3, is added at high concentration to improve complexation. The effect of this salt has been analyzed, and was found to be rather similar to the effect on classical CiEj.When uranyl nitrate complexation occurs, the cloud point decreases dramatically, together with the reduction of the area per head group at micelle / solution interface. This effect can be minimized by using a nonionic precursor having a larger polar head group. The functionalized surfactants have been tested in the cloud point extraction of uranyl nitrate, and have proved their efficiency. Those results demonstrate the viability of the functionalized surfactants design, with a covalent link between a thermosensitive surfactant block and a chelating group.VERSAILLES-BU Sciences et IUT (786462101) / SudocSudocFranceF

Pepsi-SAXS/SANS -small-angle scattering-guided tools for integrative structural bioinformatics

International audienceI will present some recent developments of our Pepsi package for integrative modeling of macromolecules guided by small-angle scattering profiles. These include very fast tools for the all-atom computations of X-ray and neutron small-angle scattering profiles, called Pepsi-SAXS and Pepsi-SANS, respectively [1,2]. These tools implement algorithms specifically designed to handle two notable properties of large macromolecules and their complexes, such as for instance viral capsids, namely their high flexibility and high degree of symmetry. Flexibility of macromolecules is not spontaneous but linked with their structure and function. Computationally, it can be often approximated with just a few collective coordinates, which can be computed e.g. using the Normal Mode Analysis (NMA). NMA determines low-frequency motions at a very low computational cost and these are particularly interesting to the structural biology community because they give insight into protein function and dynamics. On our side, we have proposed a computationally efficient nonlinear NMA method that can be applied to largest complexes from the Protein Data Bank (PDB), and which also very well preserves local stereochemistry [3-5]. Flexibility of macromolecules is often linked with their structure and function. Computationally, it can be approximated with just a few collective coordinates computed using the Normal Mode Analysis (NMA). NMA determines low-frequency motions at a very low computational cost. This technique is particularly interesting for the structural biology community as it allows extrapolating biologically relevant motions starting from high-resolution structures. Recently, we have shown that it can be extended to model local deformations and to better preserve the stereochemistry of the protein. We have developed a computationally efficient nonlinear NMA method that can be applied to the largest complexes from the Protein Data Bank (PDB) [3-5]. Large symmetrical protein structures have seemingly evolved in many organisms because they carry specific morphological and functional advantages compared to small individual protein molecules. Recently we have proposed a novel free-docking method for protein complexes with arbitrary point-group symmetry [6]. It assembles complexes with cyclic symmetry, dihedral symmetry, and also those of high order (tetrahedral, octahedral, and icosahedral). We also proposed an efficient analytical solution to the inverse problem, that is the identification of symmetry group with the corresponding axes and their continuous symmetry measures in a protein assembly [7-8]. With Pepsi-SAXS and Pepsi-SANS, one can leverage the above-mentioned developments, by optimizing structures along lowfrequency « normal modes », performing automatic and adaptive coarse-graining of molecular models, rescoring free-docking predictions, including those of symmetric assemblies, and also optimizing structural transitions. Structural models produced by Pepsi-SAXS/SANS were ranked top in the recent data-assisted protein structure prediction sub-challenge in CASP13 [9]