Modélisation du poly-époxy DGEBA-EDA et de sa réactivité vis-à-vis du cuivre : approche expérimentale et numérique

Grâce à la métallisation de leur surface, des pièces en polymères peuvent substituer certains composants métalliques dans les industries de l'aérospatiale et du transport. Les polymères ont des masses volumiques plus faibles que les métaux et une réactivité chimique limitée, ce qui en fait des candidats idéaux pour les applications spatiales. En combinant techniques expérimentales et simulations numériques, nous avons étudié les mécanismes fondamentaux de la métallisation de surface d'un polymère poly-époxy (DGEBA / EDA). L'objectif de notre étude était de développer un modèle non empirique prenant en compte les mécanismes régissant la nucléation et la croissance des films minces métalliques. Notre groupe a une longue expérience des dépôts chimiques en phase vapeur, CVD. Mais cette technique n'a pas été choisie pour la métallisation de nos surfaces de polymères car les températures requises dans le réacteur étaient trop élevées. Comme alternative, nous avons effectué une évaporation sous ultravide de Cu à température ambiante, conduisant à une diffusion des atomes en phase gazeuse sans énergie cinétique. Les processus d'adsorption et de diffusion sont donc plus proches des conditions thermodynamiques associées aux calculs. Un protocole expérimental a été mis en place afin de créer une surface polymère chimiquement homogène présentant une faible rugosité. Le polymère obtenu a été caractérisé (i) par spectroscopie infrarouge à transformée de Fourier, pour déterminer le taux de polymérisation (supérieur à 90%), (ii) par calorimétrie différentielle à balayage pour obtenir la température de transition vitreuse (Tg) ( 118,1 °C), (iii) par microscopie à force atomique (AFM) pour estimer la rugosité de la surface (Ra ˜ 1 nm), et (iv) par spectroscopie de photoélectrons X (XPS) pour caractériser les liaisons chimiques de surface. La surface de polymère a ensuite été métallisée. Grâce à des analyses AFM, l'épaisseur du film mince a été estimée à 6 nm. Nous avons ensuite utilisé l'XPS pour caractériser les liaisons interfaciales Cu / Poly-époxy. Nous avons déduit de l'interprétation des spectres XPS que le Cu est adsorbé préférentiellement sur un atome d'oxygène spécifique du polymère. Pour identifier clairement ces sites d'adsorption de Cu, nous avons ensuite simulé les spectres XPS du polymère non revêtu, par des calculs quantiques, en utilisant un modèle moléculaire (dimère : 1 molécule de DGEBA liée à 1 molécule d'EDA). Les méthodes Hartree-Fock (HF) et de la théorie de la fonctionnelle de la densité (DFT) nous ont permis de simuler des spectres XPS pour la surface nue, en prenant en compte les effets d'état final et initial. Grâce à ces résultats, nous avons pu décomposer le spectre expérimental en 8 contributions, ce qui conduit à des résultats beaucoup plus précis que les résultats habituels obtenus par l'utilisation exclusive des expériences et de la littérature. Nous avons ensuite effectué des simulations de dynamique moléculaire classique (MD) pour passer d'un modèle moléculaire (dimère) à un modèle de polymère amorphe. Nous avons utilisé le champ de force Amber généralisé (GAFF) et nous avons développé un code de réticulation des molécules de monomères. Le système initial était un mélange stœchiométrique de molécules DGEBA et EDA qui a été équilibré à 700K. Lorsque l'équilibre a été atteint, certaines propriétés structurales (par exemple, la distribution des liaisons) ont été extraites des simulations NPT. À partir de ce mélange liquide de monomères, notre code de réticulation a identifié et relié les atomes réactifs (à une distance interatomique prédéfinie < 3 Å). Après chaque étape de polymérisation, le système a été rééquilibré à 700K (simulations NPT). Après plusieurs cycles de réticulation/simulation de dynamique moléculaire, nous avons pu atteindre un taux de polymérisation de 93% et la fonction de distribution radiale (RDF), la masse volumique (1.115 à 300K) et la température de transition vitreuse Tg (115,5 °C) ont été calculées. La Tg est en accord avec la valeur expérimentale de 118,1 °C, validant notre approche numérique pour développer un modèle pour les polymères poly-époxy.Metallization of polymer surfaces can lead to the substitution of metallic components. Polymers have lower densities and limited chemical reactivity, making them ideal candidates for the space applications. Through experiments and calculations, we studied the fundamental mechanisms of surface metallization of a poly-epoxy polymer (DGEBA/EDA). The objective of our study was to develop a non-empirical model that could take into account the mechanisms governing the nucleation and growth of thin metal films. Our group has a long experience in chemical vapor deposition, CVD, and metallization of polymer composites. But we did not applied CVD at first because of the high temperatures required in the reactor. We alternatively used ultrahigh vacuum evaporation of Cu at ambient temperature. Therefore, we make sure that atoms diffuse in the gas phase without kinetic energy. Adsorption and diffusion processes are thus closer to thermodynamic conditions that prevails in calculations. An experimental protocol was refined in order to create a chemically homogeneous polymer surface with a low roughness (Ra<1nm). The bulk and the surface of the pristine polymer were characterized (i) by Fourier Transform Infrared Spectroscopy, to determine the polymerization rate (above 90%), (ii) by differential scanning calorimetry in order to obtain the glass transition temperature (Tg) (118.1 °C), (iii) by atomic force microscopy (AFM) to calculate surface roughness (Ra ˜ 1 nm), and (iv) by X-ray photoelectron spectroscopy (XPS) to characterize surface chemical bonding. The surface was then metallized. Through AFM, the thickness of the thin film was estimated at 6 nm. We then used XPS to characterize the Cu/Poly-epoxy interfacial bonding. We deduced that Cu adsorbed preferentially on a specific oxygen atom of the polymer. To clearly identify this Cu adsorption site, we further simulated the XPS spectra of our clean or metallized polymer by quantum calculations, using a dimer model (1 molecule of DGEBA connected to 1 molecule of EDA). In the Hartree-Fock (HF) and Density Functional Theory (DFT) framework, we first simulated the XPS spectra for the pristine surface taking into account initial and final state effects. Thanks to these results, we were able to analyze the experimental spectrum with 8 contributions, leading to much more accurate results than the usual results obtained by the exclusive use of experiments and literature. We then performed classical Molecular Dynamics (MD) simulations to move from a dimer model to an amorphous polymer model. We used the general Amber force field (GAFF) and we developed a code to mimic the reticulation of monomers molecules. We started from a stoichiometric mixture of DGEBA and EDA molecules. When equilibration was reached, structural properties at 700K (e.g. distribution of bonds) were extracted from the results of the NPT simulations. From this melt of monomers, the homemade reticulation code identified and connected reactive atoms (at a pre-defined inter-atomic distance < 3Å). After each step of polymerization, the system was equilibrated at 700K (NPT simulations). After multiple reticulation/MD cycles we could achieve a polymerization rate of 93% and the Radial Distribution Function (RDF), the density and the glass transition temperature Tg were calculated. The value of the computed density was 1.115 at 300K and the calculated Tg (115.5 °C) was in good agreement with the experimental Tg of 118.1 °C, validating our numerical approach to develop a model for poly-epoxies

Antibodies against Pneumococcal Capsular Polysaccharides and Natural Anti-Galactosyl (Alpha-Gal) in Patients with Humoral Immunodeficiencies

Humoral deficiencies represent a broad group of disorders. The aim of the study was to compare the levels of antibodies against pneumococcal capsular polysaccharides (anti-PCP) and natural anti-galactosyl (anti-Gal) antibodies in (1) patients with chronic lymphocytic leukaemia (CLL), (2) patients with common variable immunodeficiency (CVID), and (3) a healthy population and to explore their diagnostic and prognostic potential. Serum immunoglobulin levels and levels of anti-Gal IgG, IgA, and IgM and anti-PCP IgG and IgG2 were determined in 59 CLL patients, 30 CVID patients, and 67 healthy controls. Levels of IgG, IgA, IgM, anti-Gal IgA, anti-Gal IgM, and anti-PCP IgA were lower in CLL and CVID patients than in healthy controls (p value for all parameters < 0.0001). Decrease in the levels of IgA, IgM, anti-Gal IgA, and anti-PCP IgA was less pronounced in the CLL group than in the CVID group. IgA decline, anti-Gal IgA, anti-PCP IgA, and anti-PCP IgG2 were negatively correlated with CLL stage. We devise the evaluation of anti-Gal antibodies to be a routine test in humoral immunodeficiency diagnostics, even in cases of immunoglobulin substitution therapy. Significant reductions, mainly in anti-Gal IgA, IgM, and anti-PCP IgA levels, may have prognostic importance in CLL patients

Supplementary Material for: Immunogenicity and Safety of the Spikevax® (Moderna) mRNA SARS-CoV-2 Vaccine in Patients with Primary Humoral Immunodeficiency

Introduction: Reports on the immunogenicity and efficacy of the Spikevax® vaccine against SARS-CoV-2 in immunodeficient patients are still scarce. We aimed to evaluate the safety and immunogenicity of the vaccine in patients with primary humoral immunodeficiency. Methods: We enrolled 46 patients, including 34 patients with common variable immunodeficiency (CVID), 10 patients with unclassified hypogammaglobulinemia (HypoIg), and 2 patients with X-linked agammaglobulinemia. We collected the blood samples before vaccination (D 0), and 10 days (D +38) and 90 days (D +118) after the second vaccination. Further, we quantified SARS-CoV-2-specific T-cell response (QuantiFERON ELISA test), serum anti-RBD IgG, and anti-RBD IgA-specific antibodies (enzyme immunoassay). Results: We found that the vaccination elicited predominantly mild adverse events, comparable to healthy population. Vaccination response negatively correlated with a value of Immune Deficiency and Dysregulation Activity in all measured parameters. D +38, seroconversion for anti-RBD IgG and anti-RBD IgA was observed in 65% and 21% CVID patients, respectively. SARS-CoV-2-specific T-cell response was detected in less than 50% of CVID patients. Meanwhile, HypoIg patients had 100%, 90%, and 60% positivity rates for anti-RBD IgG, anti-RBD IgA, and T-cell response, respectively. Three months after the second vaccination, 82% of the responders remained positive for anti-RBD IgG, but only less than 50% remained positive for T-cell activity in CVIDs. Low immunogenicity was observed in patients with lung involvement and/or rituximab treatment history. No SARS-CoV-2 infection was reported within 6 months after the second vaccination. Conclusion: Spikevax® seems to be safe with satisfactory immunogenicity in patients with primary humoral immunodeficiency

Proteome-wide structural changes measured with limited proteolysis-mass spectrometry: an advanced protocol for high-throughput applications

Proteins regulate biological processes by changing their structure or abundance to accomplish a specific function. In response to a perturbation, protein structure may be altered by various molecular events, such as post-translational modifications, protein-protein interactions, aggregation, allostery or binding to other molecules. The ability to probe these structural changes in thousands of proteins simultaneously in cells or tissues can provide valuable information about the functional state of biological processes and pathways. Here, we present an updated protocol for LiP-MS, a proteomics technique combining limited proteolysis with mass spectrometry, to detect protein structural alterations in complex backgrounds and on a proteome-wide scale. In LiP-MS, proteins undergo a brief proteolysis in native conditions followed by complete digestion in denaturing conditions, to generate structurally informative proteolytic fragments that are analyzed by mass spectrometry. We describe advances in the throughput and robustness of the LiP-MS workflow and implementation of data-independent acquisition-based mass spectrometry, which together achieve high reproducibility and sensitivity, even on large sample sizes. We introduce MSstatsLiP, an R package dedicated to the analysis of LiP-MS data for the identification of structurally altered peptides and differentially abundant proteins. The experimental procedures take 3 d, mass spectrometric measurement time and data processing depend on sample number and statistical analysis typically requires ~1 d. These improvements expand the adaptability of LiP-MS and enable wide use in functional proteomics and translational applications

Spectrum and Management of Complement Immunodeficiencies (Excluding HAE) Across Europe

16th Biennial Meeting of the European-Society-for-Immunodeficiencies (ESID) -- OCT 29-NOV 01, 2014 -- Prague, CZECH REPUBLICWOS: 000347389100734European Soc Immunodeficiencie

Spectrum and Management of Complement Immunodeficiencies (Excluding Hereditary Angioedema) Across Europe

WOS: 000350886300014PubMed ID: 25663093Complement immunodeficiencies (excluding hereditary angioedema and mannose binding lectin deficiency) are rare. Published literature consists largely of case reports and small series. We collated data from 18 cities across Europe to provide an overview of primarily homozygous, rather than partial genotypes and their impact and management. Patients were recruited through the ESID registry. Clinical and laboratory information was collected onto standardized forms and analyzed using SPSS software. Seventy-seven patients aged 1 to 68 years were identified. 44 % presented in their first decade of life. 29 % had C2 deficiency, defects in 11 other complement factors were found. 50 (65 %) had serious invasive infections. 61 % of Neisseria meningitidis infections occurred in patients with terminal pathway defects, while 74 % of Streptococcus pneumoniae infections occurred in patients with classical pathway defects (p < 0.001). Physicians in the UK were more likely to prescribe antibiotic prophylaxis than colleagues on the Continent for patients with classical pathway defects. After diagnosis, 16 % of patients suffered serious bacterial infections. Age of the patient and use of prophylactic antibiotics were not associated with subsequent infection risk. Inflammatory/autoimmune diseases were not seen in patients with terminal pathway, but in one third of patients classical and alternative pathway defects. The clinical phenotypes of specific complement immunodeficiencies vary considerably both in terms of the predominant bacterial pathogen, and the risk and type of auto-inflammatory disease. Appreciation of these phenotypic differences should help both immunologists and other specialists in their diagnosis and management of these rare and complex patients.The Sir Jules Thorn Charitable Trust [12JTA