Diagnostic difficulties of Lactobacillus casei bacteraemia in immunocompetent patients: A case report

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Insights into the Partitioning Behavior of Secondary Surfactants in a Microemulsion-Based Synthesis of Metal Nanoparticles: A DLS and 2D NMR Spectroscopic Investigation

Diffusion-ordered NMR spectroscopy (DOSY) and nuclear Overhauser effect spectroscopy (NOESY) have been used to explore the diffusion and partitioning behavior of secondary surfactants added to suspensions of reverse micelles (RMs) containing either silver or gold nanoparticles (NPs), with an aim of advancing our understanding of the mechanism of metal NP extraction and/or surface functionalization with specific capping agents as performed during a microemulsion-based synthesis. We have coupled these NMR techniques with corresponding dynamic light scattering (DLS) measurements of RMs, with and without encapsulated metal NPs, upon addition of secondary surfactants. Using oleylamine (OAm), oleic acid (OA), dodecylamine (DDAm), and dodecanethiol (DDT), we show that all four secondary surfactants can rapidly diffuse into/out of the RM environment with their head groups in close proximity to the RM interior and encapsulated water molecules; however, surfactant molecules containing a terminal −NH₂ or −COOH group undergo a persistent association with the molecules of the RMs, thus solubilizing and partially sequestering a portion of the total concentration of these secondary agents within the RM interface for a lengthened period of time (in relation to the time frame of the DOSY experiments) and slowing their rate of exchange with freely diffusing molecules in the bulk solvent. The extraction of Ag or Au NPs from RMs into organic phase was determined to be critically dependent on the type and concentration of secondary surfactant added to the system, with DDT proving to be most efficient for the extraction of Ag NPs, while OA was shown to be most efficient for Au NPs. Consideration of the results obtained from this particular combination of techniques has provided new knowledge with respect to dynamic metal NP-containing microemulsion systems

The Effect of Cholesterol on Membrane Dynamics on Different Timescales in Lipid Bilayers from Fast Field-Cycling NMR Relaxometry Studies of Unilamellar Vesicles

The general applicability of fast field-cycling nuclear magnetic resonance relaxometry in the study of dynamics in lipid bilayers is demonstrated through analysis of binary unilamellar liposomes composed of 1,2-dioleoyl-sn-glycero-3-posphocholine (DOPC) and cholesterol. We extend an evidence-based method to simulating the NMR relaxation response, previously validated for single-component membranes, to evaluate the effect of the sterol molecule on local ordering and dynamics over multiple timescales. The relaxometric results are found to be most consistent with the partitioning of the lipid molecules into affected and unaffected portions, rather than a single averaged phase. Our analysis suggests that up to 25 mol%, each cholesterol molecule orders three DOPC molecules, providing experimental backup to the findings of many molecular dynamics studies. A methodology is established for studying dynamics on multiple timescales in unilamellar membranes of more complex compositions.Fil: Fraenza, Carla Cecilia. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; ArgentinaFil: Meledandri, Carla J.. Universidad de Dublin; Irlanda. University of Otago; Nueva ZelandaFil: Anoardo, Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; ArgentinaFil: Brougham, Dermot F.. Universidad de Dublin; Irland

Development of Solvent-Dispersible Coordination Polymer Nanocrystals and Application as Efficient Heterogeneous Catalysts

Nonporous coordination polymers (CPs) constructed from flexible bridging ligands have seldom been utilized in practical applications, owing to limited solubility and/or stability in most solvents. Here we have produced nanocrystal coordination polymers (NCPs) with identical crystalline structure to their macroscale counterparts, high solvent dispersibility, and large effective surface area for catalytic application. A microemulsion system has been developed for the mild synthesis of the Zn^II- and Cu^II-NCPs, resulting in control over the size, morphology, and reactivity. Both Zn^II- and Cu^II-NCPs demonstrated high catalytic activity in a ring opening reaction of cyclohexene oxide with aniline; furthermore, reduced Cu-NCPs were employed as efficient, reusable catalysts for an azide–alkyne cycloaddition “click” reaction in the nonpolar solvent heptane. In contrast, all macroscale CP equivalents, prepared by conventional methods, were catalytically inactive