Comparison of human blood serum DSC profiles in aqueous and PBS buffer solutions

Journal of Thermal Analysis and Calorimetry - The results of studies of physiological fluids by differential scanning calorimetry (DSC) for the purpose of diagnosis and monitoring of diseases are...     

A Study of the Activity of Recombinant Mn-Superoxide Dismutase in the Presence of Gold and Silver Nanoparticles

Applied Biochemistry and Biotechnology - Superoxide dismutase (SOD) is one of the best characterized enzyme maintaining the redox state in the cell. A bacterial expression system was used to...     

The influence of Lewis acid catalyst on the kinetic and molecular mechanism of nitrous acid elimination from 5-nitro-3-phenyl-4,5-dihydroisoxazole: DFT computational study

Chemistry of Heterocyclic Compounds - The molecular mechanism of nitrous acid elimination from 5-nitro-3-phenyl-4,5-dihydroisoxazole systems has been explored using DFT computational study. It was...     

Stereoselective synthesis of isoindolinones and tert-butyl sulfoxides

A reaction of Grignard reagents with an optically pure N-sulfinylimine derived from methyl 2-formylbenzoate yields enantioenriched isoindolinones and tert-butyl sulfoxides. The products are formed by the addition of the nucleophile to N-sulfinylimine followed by cyclization to form N-tert-butylsulfinylisoindolinone, which readily undergoes substitution with a second equivalent of Grignard reagent. The reaction can be carried out in dichloromethane at room temperature or at elevated temperatures without any loss of stereoselectivity. The use of nucleophiles other than Grignard reagents has also been investigated.     

Thermal parameters determination of Co–Al–W as-cast alloy homogenization by DTA analysis

The γ–γ′ Co-based superalloys are newly developed class of refractory alloys which may replace commercial Ni-based superalloys owing to their favorable properties at high temperature. In case of new Co-based superalloys, the heat treatment aims to obtain microstructure composed of appropriate volume fraction of small cuboidal γ′-Co₃(Al,W) precipitates within the γ-Co matrix. However, due to a high tendency to interdendritic segregations of alloying elements, the alloys based on Co–Al–W system should be normally homogenized before further steps of heat treatment (solutionizing and aging). In this study, thermal analysis was applied for determination of temperature range for primary heat treatment of the Co–9Al–9W (at.%). The differential thermal analysis (DTA) measurements were carried out on the thermal analyzer NETZSCH STA 449 F3 Jupiter. On the base of obtained results, respectively, solvus of γ′ phase and solidus temperatures were determined, as well as the thermal range of Co₃W (DO₁₉) phase precipitation. As a consequence, the heat treatment without homogenizing (only solution and aging) was proposed as a most suitable way to obtain beneficial microstructure.     

NMR studies of the Zn2+ interactions with rat and human beta-amyloid (1-28) peptides in water-micelle environment

Alzheimer's disease is a fatal neurodegenerative disorder involving the abnormal accumulation and deposition of peptides (amyloid-beta, Abeta) derived from the amyloid precursor protein. Here, we present the structure and the Zn2+ binding sites of human and rat Abeta(1-28) fragments in water/sodium dodecyl sulfate (SDS) micelles by using 1H NMR spectroscopy. The chemical shift variations measured after Zn2+ addition at T>310 K allowed us to assign the binding donor atoms in both rat and human zinc complexes. The Asp-1 amine, His-6 Ndelta, Glu-11 COO-, and His-13 Nepsilon of rat Abeta28 all enter the metal coordination sphere, while His-6 Ndelta, His-13, His-14 Nepsilon, Asp-1 amine, and/or Glu-11 COO- are all bound to Zn2+ in the case of human Abeta28. Finally, a comparison between the rat and human binding abilities was discussed.     

Particulate matter analysis at elementary schools in Curitiba,Brazil

The particulate matter indoors and outdoors of the classrooms at two schools in Curitiba, Brazil, was characterised in order to assess the indoor air quality. Information concerning the bulk composition was provided by energy-dispersive x-ray fluorescence (EDXRF). From the calculated indoor/outdoor ratios and the enrichment factors it was observed that S-, Cl- and Zn-rich particles are of concern in the indoor environment. In the present research, the chemical compositions of individual particles were quantitatively elucidated, including low-Z components like C, N and O, as well as higher-Z elements, using automated electron probe microanalysis low Z EPMA. Samples were further analysed for chemical and morphological aspects, determining the particle size distribution and classifying them according to elemental composition associations. Five classes were identified based on major elemental concentrations: aluminosilicate, soot, organic, calcium carbonate and iron-rich particles. The majority of the respirable particulate matter found inside of the classroom was composed of soot, biogenic and aluminosilicate particles. In view of the chemical composition and size distribution of the aerosol particles, local deposition efficiencies in the human respiratory system were calculated revealing the deposition of soot at alveolar level. The results showed that on average 42% of coarse particles are deposited at the extrathoracic level, whereas 24% are deposited at the pulmonary region. The fine fraction showed a deposition rate of approximately 18% for both deposition levels.     

Two isomorphous ZnII/CoII complexes with tri‐tert‐butoxysilanethiol and histamine,and (4‐hydroxymethyl‐1H‐imidazole‐κN)bis(tri‐tert‐butoxysilanethiolato‐κ2O,S)zinc(II)

The complexes [2‐(1H‐imidazol‐4‐yl‐κN³)ethylamine‐κN]bis(tri‐tert‐butoxysilanethiolato‐κS)cobalt(II), [Co(C₁₂H₂₇O₃SSi)₂(C₅H₉N₃)], and [2‐(1H‐imidazol‐4‐yl‐κN³)ethylamine‐κN]bis(tri‐tert‐butoxysilanethiolato‐κS)zinc(II), [Zn(C₁₂H₂₇O₃SSi)₂(C₅H₉N₃)], are isomorphous. The central Zn^II/Co^II ions are surrounded by two S atoms from the tri‐tert‐butoxysilanethiolate ligand and by two N atoms from the chelating histamine ligand in a distorted tetrahedral geometry, with two intramolecular N—H...O hydrogen‐bonding interactions between the histamine NH₂ groups and tert‐butoxy O atoms. Molecules of the complexes are joined into dimers via two intermolecular bifurcated N—H...(S,O) hydrogen bonds. The Zn^II atom in [(1H‐imidazol‐4‐yl‐κN³)methanol]bis(tri‐tert‐butoxysilanethiolato‐κ²O,S)zinc(II), [Zn(C₁₂H₂₇O₃SSi)₂(C₄H₆N₂O)], is five‐coordinated by two O and two S atoms from the O,S‐chelating silanethiolate ligand and by one N atom from (1H‐imidazol‐4‐yl)methanol; the hydroxy group forms an intramolecular hydrogen bond with sulfur. Molecules of this complex pack as zigzag chains linked by N—H...O hydrogen bonds. These structures provide reference details for cysteine‐ and histidine‐ligated metal centers in proteins.