Tocochromanols composition in kernels recovered from different apricot varieties: RP-HPLC/FLD and RP-UPLC-ESI/MSn study

Composition of tocochromanols in kernels recovered from 16 different apricot varieties (Prunus armeniaca L.) was studied. Three tocopherol (T) homologues, namely α, γ and δ, were quantified in all tested samples by an RP-HPLC/FLD method. The γ-T was the main tocopherol homologue identified in apricot kernels and constituted approximately 93% of total detected tocopherols. The RP-UPLC-ESI/MSⁿ method detected trace amounts of two tocotrienol homologues α and γ in the apricot kernels. The concentration of individual tocopherol homologues in kernels of different apricots varieties, expressed in mg/100 g dwb, was in the following range: 1.38–4.41 (α-T), 42.48–73.27 (γ-T) and 0.77–2.09 (δ-T). Moreover, the ratio between individual tocopherol homologues α:γ:δ was nearly constant in all varieties and amounted to approximately 2:39:1.     

Studying the active-site loop movement of the S?o Paolo metallo-β-lactamase-1

Metallo-β-lactamases (MBLs) catalyse the hydrolysis of almost all β-lactam antibiotics. We report biophysical and kinetic studies on the São Paulo MBL (SPM-1), which reveal its Zn(ii) ion usage and mechanism as characteristic of the clinically important di-Zn(ii) dependent B1 MBL subfamily. Biophysical analyses employing crystallography, dynamic ¹⁹F NMR and ion mobility mass spectrometry, however, reveal that SPM-1 possesses loop and mobile element regions characteristic of the B2 MBLs. These include a mobile α3 region which is important in catalysis and determining inhibitor selectivity. SPM-1 thus appears to be a hybrid B1/B2 MBL. The results have implications for MBL evolution and inhibitor design.     

Thermal air-oxidized coating on Yb14−xRExMnSb11 ceramics

Journal of Thermal Analysis and Calorimetry - A high sublimation rate of Yb14MnSb11 as a promising thermoelectric material at working temperatures is a critical factor for its space power...     

Stripping Analysis of Trace Metals at a Flow-Through Reticulated Vitreous Carbon Electrode after the Preconcentration by Supported Liquid Membrane Technique

Abstract

The performance of a flow-through mercury coated reticulated vitreous carbon (RVC) electrode in the potentiometric stripping analysis (PSA) of trace metals has been examined. A wall-jet glassy carbon cell was used for the comparative experiments. Experimental parameters influencing the stripping signals have been optimised in order to use the stripping analysis after the preconcentration and matrix isolation by supported liquid membrane (SLM) technique. The SLM with di-2-ethylhexyl-phosphoric acid (DEHPA) as the extractant in the membrane liquid for proton driven transport of trace metals across the membrane has been chosen. Results presented for lead determination in river water demonstrate the analytical advantages of coupled technique SLM-PSA.     

Concentration-Dependent Interactions of Amphiphilic PiB Derivative Metal Complexes with Amyloid Peptides Aβ and Amylin**

Metal chelates targeted to amyloid peptides are widely explored as diagnostic tools or therapeutic agents. The attachment of a metal complex to amyloid recognition units typically leads to a decrease in peptide affinity. We show here that by separating a macrocyclic GdL chelate and a PiB targeting unit with a long hydrophobic C10 linker, it is possible to attain nanomolar affinities for both Aβ_1-40 (K_d=4.4 nm ) and amylin (K_d=4.5 nm ), implicated, respectively in Alzheimer's disease and diabetes. The Scatchard analysis of surface plasmon resonance data obtained for a series of amphiphilic, PiB derivative GdL complexes indicate that their Aβ_1-40 or amylin binding affinity varies with their concentration, thus micellar aggregation state. The GdL chelates also affect peptide aggregation kinetics, as probed by thioflavin-T fluorescence assays. A 2D NMR study allowed identifying that the hydrophilic region of Aβ_1-40 is involved in the interaction between the monomer peptide and the Gd³⁺ complex. Finally, ex vivo biodistribution experiments were conducted in healthy mice by using ¹¹¹In labeled analogues. Their pancreatic uptake, ∼3 %ID g⁻¹, is promising to envisage amylin imaging in diabetic animals.     

Aerosol source (biomass,traffic and coal emission) apportionment in Lithuania using stable carbon and radiocarbon analysis*

In the present study, a combination of the stable carbon isotope ratio (¹³C/¹²C) with radiocarbon data (¹⁴C) allowed us to perform the aerosol source apportionment. Filter samples of PM₁ were collected during the warm and cold periods in rural and urban sites in Lithuania. The ¹⁴C/¹²C ratio of total carbon (TC) was measured using the single stage accelerator mass spectrometer quantifying of fossil and non-fossil derived aerosol emissions. The δ¹³C value was measured using an elemental analyser interfaced with an isotope ratio mass spectrometer. We have found that the highest fraction of contemporary carbon (f_c?=?0.82) was measured during a warm period in a rural location. A higher fraction of fossil fuel-derived carbon was observed for air masses transported from highly industrialized Western European regions during both seasons. Isotope mass balance calculations revealed that the traffic emissions composed 15 and 25?% in rural and urban sites, respectively, and did not change during either season. Input from coal-derived aerosol particles was estimated to be 15?% at an urban site during the cold period. The combination of the stable carbon isotope ratio with the radiocarbon data allowed us to distinguish coal, liquid fossil fuel combustion, and non-fossil derived aerosol particle emissions.     

Effect of conformational parameters on physical properties of polymers containing pendant phenoxyphthalonitrile substituents

Heteroaromatic polymers are considered to be high performance organic materials due to their unique and highly attractive properties, including outstanding thermal and mechanical resistance, that arise from their aromatic structure and strong interactions between macromolecular chains. Modification or designing new molecular architectures with tailored physico-chemical characteristics allows expanding the applications of these materials in various advanced technologies. Herein, a series of polymers containing bulky phenoxyphthalonitrile pendant units was synthesized and their physical properties were studied and correlated with their conformational parameters, as well as free and van der Waals volumes. For comparison, the related polymers without lateral moieties were also investigated to highlight the effect of bulky substituent on the polymer rigidity. Thus, it is shown that conformational rigidity determines the packing of macromolecules in solid state, and, therefore, the free volume, glass transition, and decomposition temperatures. The values found experimentally for T _g correlate well with those obtained using the conformational rigidity parameters. The dependence of T _g of these polymers on Kuhn segment is described by linear equations, with very good factors of convergence. The correlations established by Monte Carlo method allow obtaining the T _g values for related polymers where the experimental measurement of this parameter is difficult.