Solvent Annealing of Striped Ellipsoidal Block Copolymer Particles: Reversible Control over Lamellae Asymmetry, Aspect Ratio, and Particle Surface

Solvent annealing is a versatile tool to adjust the shape and morphology of block copolymer (BCP) particles. During this process, polar solvents are often used for block-selective swelling. However, such water-miscible solvents can induce (partial) solubilization of one block in the surrounding aqueous medium, thus, causing complex structural variations and even particle disassembly. To reduce the complexity in morphology control, we focused on toluene as a nonpolar polystyrene-selective solvent for the annealing of striped polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) ellipsoids. The selective stretching of PS chains produces unique asymmetric lamellae structures, which translate to an increase in the particle aspect ratio after toluene evaporation. Complete reversibility is achieved by changing to chloroform as a nonselective solvent. Moreover, surfactants can be used to tune block-selective wetting of the particle surface during the annealing; for example, a PS shell can protect the internal lamellae structure from disassembly. Overall, this versatile postassembly process enables the tailoring of the structural features of striped colloidal ellipsoids by only using commercial BCPs and solvents.Fil: Navarro, Lucila. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Thünemann, Andreas F.. No especifíca;Fil: Klinger, Daniel. Freie Universität Berlin; Alemani

Solvent Annealing of Striped Ellipsoidal Block Copolymer Particles: Reversible Control over Lamellae Asymmetry, Aspect Ratio, and Particle Surface

Solvent annealing is a versatile tool to adjust the shape and morphology of block copolymer (BCP) particles. During this process, polar solvents are often used for block-selective swelling. However, such water-miscible solvents can induce (partial) solubilization of one block in the surrounding aqueous medium, thus, causing complex structural variations and even particle disassembly. To reduce the complexity in morphology control, we focused on toluene as a nonpolar polystyrene-selective solvent for the annealing of striped polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) ellipsoids. The selective stretching of PS chains produces unique asymmetric lamellae structures, which translate to an increase in the particle aspect ratio after toluene evaporation. Complete reversibility is achieved by changing to chloroform as a nonselective solvent. Moreover, surfactants can be used to tune block-selective wetting of the particle surface during the annealing; for example, a PS shell can protect the internal lamellae structure from disassembly. Overall, this versatile postassembly process enables the tailoring of the structural features of striped colloidal ellipsoids by only using commercial BCPs and solvents

OGFOD1 catalyzes prolyl hydroxylation of RPS23 and is involved in translation control and stress granule formation

2-Oxoglutarate (2OG) and Fe(II)-dependent oxygenase domain-containing protein 1 (OGFOD1) is predicted to be a conserved 2OG oxygenase, the catalytic domain of which is related to hypoxia-inducible factor prolyl hydroxylases. OGFOD1 homologs in yeast are implicated in diverse cellular functions ranging from oxygen-dependent regulation of sterol response genes (Ofd1, Schizosaccharomyces pombe) to translation termination/mRNA polyadenylation (Tpa1p, Saccharomyces cerevisiae). However, neither the biochemical activity of OGFOD1 nor the identity of its substrate has been defined. Here we show that OGFOD1 is a prolyl hydroxylase that catalyzes the posttranslational hydroxylation of a highly conserved residue (Pro-62) in the small ribosomal protein S23 (RPS23). Unusually OGFOD1 retained a high affinity for, and forms a stable complex with, the hydroxylated RPS23 substrate. Knockdown or inactivation of OGFOD1 caused a cell type-dependent induction of stress granules, translational arrest, and growth impairment in a manner complemented by wild-type but not inactive OGFOD1. The work identifies a human prolyl hydroxylase with a role in translational regulation

Recurrent Campylobacter jejuni Infections with In Vivo Selection of Resistance to Macrolides and Carbapenems: Molecular Characterization of Resistance Determinants

Erratum in: Microbiol Spectr. 2023 Dec 12;11(6):e0312123. doi: 10.1128/spectrum.03121-23. Epub 2023 Oct 10.Free PMC article: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10434052/We present two independent cases of recurrent multidrug-resistant Campylobacter jejuni infection in immunocompromised hosts and the clinical challenges encountered due to the development of high-level carbapenem resistance. The mechanisms associated with this unusual resistance for Campylobacters were characterized. Initial macrolide and carbapenem-susceptible strains acquired resistance to erythromycin (MIC . 256mg/L), ertapenem (MIC . 32mg/L), and meropenem (MIC . 32mg/L) during treatment. Carbapenem-resistant isolates developed an in-frame insertion resulting in an extra Asp residue in the major outer membrane protein PorA, within the extracellular loop L3 that connects b-strands 5 and 6 and forms a constriction zone involved in Ca21 binding. The isolates presenting the highest MIC to ertapenem exhibited an extra nonsynonymous mutation (G167AjGly56Asp) at PorA’s extracellular loop L1. IMPORTANCE Carbapenem susceptibility patterns suggest drug impermeability, related to either insertion and/or single nucleotide polymorphism (SNP) within porA. Similar molecular events occurring in two independent cases support the association of these mechanisms with carbapenem resistance in Campylobacter spp.Importance: Carbapenem susceptibility patterns suggest drug impermeability, related to either insertion and/or single nucleotide polymorphism (SNP) within porA. Similar molecular events occurring in two independent cases support the association of these mechanisms with carbapenem resistance in Campylobacter spp.This work was partially supported by GenomePT (ref. POCI-01-0145-FEDER-022184) from Fundação para a Ciência e Tecnologia, Portugal.info:eu-repo/semantics/publishedVersio

Recurrent Campylobacter jejuni Infections with In Vivo Selection of Resistance to Macrolides and Carbapenems: Molecular Characterization of Resistance Determinants

We present two independent cases of recurrent multidrug-resistant Campylobacter jejuni infection in immunocompromised hosts and the clinical challenges encountered due to the development of high-level carbapenem resistance. The mechanisms associated with this unusual resistance for Campylobacters were characterized. Initial macrolide and carbapenem-susceptible strains acquired resistance to erythromycin (MIC . 256mg/L), ertapenem (MIC . 32mg/L), and meropenem (MIC . 32mg/L) during treatment. Carbapenem-resistant isolates developed an in-frame insertion resulting in an extra Asp residue in the major outer membrane protein PorA, within the extracellular loop L3 that connects b-strands 5 and 6 and forms a constriction zone involved in Ca21 binding. The isolates presenting the highest MIC to ertapenem exhibited an extra nonsynonymous mutation (G167AjGly56Asp) at PorA s extracellular loop L1. IMPORTANCE Carbapenem susceptibility patterns suggest drug impermeability, related to either insertion and/or single nucleotide polymorphism (SNP) within porA. Similar molecular events occurring in two independent cases support the association of these mechanisms with carbapenem resistance in Campylobacter spp

Effects of liraglutide on the metabolism of triglyceride-rich lipoproteins in type 2 diabetes

Aim: To elucidate the impact of liraglutide on the kinetics of apolipoprotein (apo) B48- and apoB100-containing triglyceride-rich lipoproteins in subjects with type 2 diabetes (T2D) after a single fat-rich meal. Materials and Methods: Subjects with T2D were included in a study to investigate postprandial apoB48 and apoB100 metabolism before and after 16 weeks on 1.8 mg/day liraglutide (n = 14) or placebo (n = 4). Stable isotope tracer and compartmental modelling techniques were used to determine the impact of liraglutide on chylomicron and very low-density lipoprotein (VLDL) production and clearance after a single fat-rich meal. Results: Liraglutide reduced apoB48 synthesis in chylomicrons by 60% (p <.0001) and increased the triglyceride/apoB48 ratio (i.e. the size) of chylomicrons (p <.001). Direct clearance of chylomicrons, a quantitatively significant pathway pretreatment, decreased by 90% on liraglutide (p <.001). Liraglutide also reduced VLDL1-triglyceride secretion (p = .017) in parallel with reduced liver fat. Chylomicron-apoB48 production and particle size were related to insulin sensitivity (p = .015 and p <.001, respectively), but these associations were perturbed by liraglutide. Conclusions: In a physiologically relevant setting that mirrored regular feeding in subjects with T2D, liraglutide promoted potentially beneficial changes on postprandial apoB48 metabolism. Using our data in an integrated metabolic model, we describe how the action of liraglutide in T2D on chylomicron and VLDL kinetics could lead to decreased generation of remnant lipoproteins.Peer reviewe

A Study of Porous Transitions of Layer-By-Layer Thin Films and Patterning Multilayers

This thesis research focuses on fundamental understanding regarding the morphological transitions of weak polyelectrolyte multilayers (PEMs) formed by the layer-by-layer (LbL) electrostatic assembly of oppositely charged polymers. he first part of this thesis focuses on patterning polyelectrolyte multilayers that are able to undergo transitions from continuous films to porous materials by using hydrogel stamps. The stamping process is able to locally etch and pattern the porous transition in the LbL films by using reactive wet stamping (r-WETS). It was found that r-WETS of PEMs can also enable the modification of chemical functionality. The second part is an investigation about morphological changes of weak polyelectrolyte multilayers assembled with PAH and PAA using r-WETS in which hydrogel stamp material was soaked into various salt solutions and then applied to the LbL films. Also, in this study we presented a novel strategy to create a continuous gradient structure in thickness or porosity along the lateral direction of the thin films using concentration gradient salt stamping. The third part is an investigation regarding the mechanism of the transition from a continuous morphology to a porous morphology within weak polyelectrolyte multilayers. These morphological changes were able to be created by both acidic and basic post-assembly treatments, showing various morphological transitions from the introduction of porosity to the collapse of these porous structures and the eventual dissolution of the films. A similar observation of morphological transitions in weak polyelectrolyte multilayers was obtained by applying an electric field to the films in the fourth part of this thesis. Exposure to an electric field resulted in the creation of a porous structure, which can be ascribed to local changes in pH and subsequent structural rearrangements of the weak polyelectrolyte constituents. The final part of this thesis is to make PEMs into nanostructured matrices for inorganic synthesis. Multilayers possessing ion-exchangeable carboxylic acid groups were used for binding metal catalysts such as platinum (Pt) nanoparticles (NPs) within the film. Therefore, polyelectrolyte multilayers were able to stabilize catalytic Pt NPs in order to increase the useful time of catalyst materials suitable for use in proton exchange membrane fuel cells

Instrumentation concepts and requirements for a space vacuum research facility

An earth-orbiting molecular shield that offers a unique opportunity for conducting physics, chemistry, and material processing experiments under a combination of environmental conditions that are not available in terrestrial laboratories is equipped with apparatus for forming a molecular beam from the freestream. Experiments are carried out using a moderate energy, high flux density, high purity atomic oxygen beam in the very low density environment within the molecular shield. As a minimum, the following instruments are required for the molecular shield: (1) a mass spectrometer; (2) a multifunction material analysis instrumentation system; and (3) optical spectrometry equipment. The design is given of a furlable molecular shield that allows deployment and retrieval of the system (including instrumentation and experiments) to be performed without contamination. Interfaces between the molecular shield system and the associated spacecraft are given. An in-flight deployment sequence is discussed that minimizes the spacecraft-induced contamination in the vicinity of the shield. Design approaches toward a precursor molecular shield system are shown

Nanopatterns of Zinc Phthalocyanines, Gold Nanoparticles, and Porphyrins Prepared Using Particle Lithography: Characterization of Patterning Steps with Scanning Probe Microscopy

The growth and self-assembly of molecules on surfaces can be directly visualized at the molecular level using studies which combine nanoscale lithography and high-resolution imaging. Nanopatterning provides a unique and practical approach for direct views of surface changes after the key chemical steps of nanopatterning, providing landmarks and baselines for measuring growth in vertical and lateral dimensions. Controlling the arrangement of materials on surfaces at the nanoscale can be achieved using particle lithography. Arrays of well-defined nanostructures can be prepared with reproducible geometries and arrangement. Results for the preparation of nanopatterns produced with particle lithography are presented using high resolution images acquired with scanning probe microscopy (SPM). Samples were prepared using steps for depositing nanoparticles, porphyrins, and phthalocyanines on patterned surfaces to generate multicomponent nanopatterns. Studies of surface chemistry at the molecular level have practical applications for emerging technologies with photovoltaic and photoelectronic devices. Atomic force microscopy (AFM) was used to characterize samples to gain insight on the changes in surface chemistry after patterning organosilanes, organothiols and nanoparticles. For studies of surface chemistry at the nanoscale, AFM has unique capabilities for molecular visualization and ultrasensitive measurements of surface properties. The history of SPM, instrument set-up, and results for particle lithography with porphyrins, zinc phthalocyanines and gold nanoparticles are described in this dissertation. Protocols for patterning porphyrin nanostructures on Au(111) were developed based on steps with immersion combined with particle lithography. Porphyrins with a central metal ion, 5,10,15,20-tetraphenyl-21H,23H-porphine (TPP) and free-base 5,10,15,20-tetraphenyl-21H,23H-porphine nickel(II) (TPN) were studied. Samples of zinc phthalocyanines were prepared using particle lithography with surfaces that were patterned with organosilanes. The dimensions and spacing can be selectively tuned by using selected sizes of latex ad silica spheres as a surface mask. The metallated phthalocyanines bound selectively to the spatially confined sites of nanopatterns, and did not bind to areas of the organosilane resist. Bare gold nanoparticles and organosilane coated nanoparticles were synthesized for characterizations with AFM. At the nanoscale, variations in the sizes of patterns provide a surface test platform for evaluating size dependent physical properties