Preparation, purification and characterization of aminopropyl-functionalized silica sol

A new, simple and “green” method was developed for the surface modification of 20 nm diameter Stöber silica particles with 3-aminopropyl(diethoxy)methylsilane in ethanol. The bulk polycondensation of the reagent was inhibited and the stability of the sol preserved by adding a small amount of glacial acetic acid after appropriate reaction time. Centrifugation, ultrafiltration and dialysis were compared in order to choose a convenient purification technique that allows the separation of unreacted silylating agent from the nanoparticles without destabilizing the sol. The exchange of the solvent to acidic water during the purification yielded a stable colloid, as well. Structural and morphological analysis of the obtained aminopropyl silica was performed using transmission electron microscopy (TEM), dynamic light scattering (DLS) and zeta potential measurements, Fourier-transform infrared (FTIR), 13C and 29Si MAS nuclear magnetic resonance (NMR) spectroscopies, as well as small angle X-ray scattering (SAXS). Our investigations revealed that the silica nanoparticle surfaces were partially covered with aminopropyl groups, and multilayer adsorption followed by polycondensation of the silylating reagent was successfully avoided. The resulting stable aminopropyl silica sol (ethanolic or aqueous) is suitable for biomedical uses due to its purity

The EntOptLayout Cytoscape plug-in for the efficient visualization of major protein complexes in protein-protein interaction and signalling networks

Motivation: Network visualizations of complex biological datasets usually result in 'hairball' images, which do not discriminate network modules. Results: We present the EntOptLayout Cytoscape plug-in based on a recently developed network representation theory. The plug-in provides an efficient visualization of network modules, which represent major protein complexes in protein-protein interaction and signalling networks. Importantly, the tool gives a quality score of the network visualization by calculating the information loss between the input data and the visual representation showing a 3- to 25-fold improvement over conventional methods. Availability: The plug-in (running on Windows, Linux, or Mac OS) and its tutorial (both in written and video forms) can be downloaded freely under the terms of the MIT license from: http://apps.cytoscape.org/apps/entoptlayout. Contact: [email protected] Supplementary information: Supplementary data are available at Bioinformatics online

Crystal structures of the disease-causing D444V mutant and the relevant wild type human dihydrolipoamide dehydrogenase

We report the crystal structures of the human (dihydro)lipoamide dehydrogenase (hLADH, hE3) and its disease-causing homodimer interface mutant D444V-hE3 at 2.27 and 1.84 Å resolution, respectively. The wild type structure is a unique uncomplexed, unliganded hE3 structure with the true canonical sequence. Based on the structural information a novel molecular pathomechanism is proposed for the impaired catalytic activity and enhanced capacity for reactive oxygen species generation of the pathogenic mutant. The mechanistic model involves a previously much ignored solvent accessible channel leading to the active site that might be perturbed also by other disease-causing homodimer interface substitutions of this enzyme. © 2018 Elsevier Inc

A warfarin-nátrium permetil-monoamino-béta-ciklodextrinnel képzett zárványkomplexének szerkezete és stabilitása | Structure and stability of warfarin-sodium inclusion complexes formed with permethylated monoamino-β-cyclodextrin

Kapilláris elektroforézis (CE) és kétdimenziós NMR módszereket kombináltunk a warfarin-Na/PMMA komplexek vízben történő szerkezeti jellemzésében. E technikák kiegészítették egymást a komplexek stabilitásának és szerkezetének meghatározásában. CE-ben a migrációs sorrend megváltozását tapasztaltuk a pH függvényében. NMR-ben kétdimenziós korrelációs mérésekkel elvégeztük az izomertiszta ciklikus heptaszaccharid teljes 1H és 13C jelhozzárendelését. Az 1H-NMR asszignáció birtokában értelmeztük a kémiai eltolódás változásokat a kémiailag különböző szénhidrát gyűrűk esetében. Megállapítottuk, hogy mindkét nyílt formájú warfarin enantiomer esetében a kumarin gyűrű a primer oldal irányából ékelődik a ciklodextrin üregébe, melyet a CH/pi interakciók mellett egy ionpár kölcsönhatás is stabilizál. | Inclusion complexes of warfarin enantiomers with permethylated monoamino-β-cyclodextrin (PMMABCD) were characterized using CE and 1H NMR spectroscopy in aqueous solution. These techniques gave complementary information on the stability and the structure of the diastereomeric host–guest inclusion complexes. The stability constants were determined from CE experiments in a wide pH range. Change in the migration order on the variation of the pH was observed. 1H NMR assignments have been established for the seven non-equivalent carbohydrate units of the host in the complex at pH 7–9. Specific H–H distance restraints were obtained from NOESY experiments and were introduced into molecular modeling to establish the geometry of the inclusion complexes. It was found that the open side chain warfarin enters the cavity from the primary side of the CD. The orientation of the coumarin ring within the cavity has the same preference for the two warfarin enantiomers owing to an ionic interaction with the amino group of the CD. Accordingly, enantioselectivity at pH 8.5 arises from the difference in the CH/π interactions between warfarin aromatics and the manifold of CH groups of the CD

Magnetic Nanoparticles with Dual Surface Functions—Efficient Carriers for Metalloporphyrin-Catalyzed Drug Metabolite Synthesis in Batch and Continuous-Flow Reactors

The dual functionalization of magnetic nanoparticles with inert (methyl) and reactive (aminopropyl) groups enables efficient immobilization of synthetic metalloporphyrins (such as 5,10,15,20-tetrakis(2,3,4,5,6-pentafluorophenyl)iron(II) porphyrin and 5,10,15,20-tetrakis-(4-sulfonatophenyl)iron(II) porphyrin) via covalent or ionic interactions. The proportion of reactive function on the surface has significant effect on the biomimetic activity of metalloporphyrins. The optimized magnetic nanocatalyst containing porphyrin was successfully applied for biomimetic oxidation of antihypertensive drug Amlodipine in batch and continuous-flow reactors as well