In Vivo Biotransformation of 3,3′,4,4′-Tetrachlorobiphenyl by Whole Plants−Poplars and Switchgrass

Polychlorinated biphenyls (PCBs) are widely distributed persistent organic pollutants. In vitro research has shown that plant cell cultures might transform lower chlorinated congeners to hydroxylated PCBs, but there are few studies on in vivo metabolism of PCBs by intact whole plants. In this research, poplar plants (Populus deltoides × nigra, DN34) and switchgrass (Panicum vigratum, Alamo) were hydroponically exposed to 3,3′,4,4′-tetrachlorobiphenyl (CB77). Metabolism in plants occurred rapidly, and metabolites were detected after only a 24 h exposure. Rearrangement of chlorine atoms and dechlorination of CB77 by plants was unexpectedly observed. In addition, poplars were able to hydroxylate CB77 and the metabolite 6-hydroxy-3,3′,4,4′-tetrachlorobiphenyl (6-OH-CB77) was identified and quantified. Hybrid poplar was able to hydroxylate CB77, but switchgrass was not, suggesting that enzymatic transformations are plant specific. Sulfur-containing metabolites (from the action of sulfotransferases) were investigated in this study, but they were not detected in either poplar or switchgrass

Co-encapsulation of human serum albumin and superparamagnetic iron oxide in PLGA nanoparticles: Part I. Effect of process variables on the mean size

PLGA (poly d,l-lactic-co-glycolic acid) nanoparticles (NPs) encapsulating magnetite nanoparticles (MNPs) along with a model drug human serum albumin (HSA) were prepared by double emulsion solvent evaporation method. This Part I will focus on size and size distribution of prepared NPs, whereas encapsulation efficiency will be discussed in Part II. It was found that mean hydrodynamic particle size was influenced by five important process variables. To explore their effects, a five-factorial, three-level experimental design and statistical analysis were carried out using STATISTICA® software. Effect of process variables on the mean size of nanoparticles was investigated and finally conditions to minimize size of NPs were proposed. GAMS™/MINOS software was used for optimization. The mean hydrodynamic size of nanoparticles ranged from 115 to 329 nm depending on the process conditions. Smallest possible mean particle size can be achieved by using low polymer concentration and high dispersion energy (enough sonication time) along with small aqueous/organic volume ratio

On the selectivity of oxynitrilases towards \u3b1-oxygenated aldehydes

Different \u3b1-alkoxy and \u3b1,\u3b2-di-alkoxy substituted aldehydes have been submitted to the catalytic action of the oxynitrilases from almond (PaHNL) or from Hevea brasiliensis (HbHNL), in order to explore the possibility of using these enzymes for the preparation of complex cyanohydrins. The selectivity of both enzymes towards these compounds was found to be largely dependent on the substitutents, being low with the aldehydes carrying the sterically more demanding phenyl substituent. Contrary to the chemical addition of HCN, which always occurs with a slight preference for the formation of the anti diastereoisomers, the enzymatic cyanuration - occurring with a facial preference, Si or Re according to the biocatalyst used - gave a mixture of cyanohydrins that, depending on the starting enantiomeric aldehyde, can be enriched in the syn diastereoisomers

High surface stability of magnetite on bi-layer Fe₃O₄/Fe/MgO(0 0 1) films under 1 MeV Kr⁺ ion irradiation

We investigate the stability of the bi-layer Fe₃O₄/Fe/MgO(0 0 1) films grown epitaxially on MgO(0 0 1) substrates with the layer thickness in the range of 25–100 nm upon 1 MeV Kr⁺ ion irradiation. The layer structure and layer composition of the films before and after ion irradiation were studied by XRR, RBS and RBS-C techniques. The interdiffusion and intermixing was analyzed. No visible change in the RBS spectra was observed upon irradiation with ion fluence below 10¹⁵ Kr cm⁻². The bi-layer structure and the stoichiometric Fe₃O₄ layer on the surface were well preserved after Kr+ ion irradiation at low damage levels, although the strong intermixing implied a large interfacial (FexOy) and (Fe, Mg)Oy layer respective at Fe₃O₄–Fe and Fe–MgO interface. The high ion fluence of 3.8 × 10¹⁶ Kr cm⁻² has induced a complete oxidization of the buffer Fe layer. Under such Kr fluence, the stoichiometry of the Fe₃O₄ surface layer was still preserved indicating its high stability. The entire film contains FexOy -type composition at ion fluence large than 5.0 × 10¹⁶ Kr cm⁻²

High surface stability of magnetite on bi-layer Fe3O4/Fe/MgO(0 0 1) films under 1 MeV Kr+ ion irradiation

We investigate the stability of the bi-layer Fe3O4/Fe(0 0 1) films grown epitaxially on MgO(0 0 1) substrates with the layer thickness in the range of 25–100 nm upon 1 MeV Kr+ ion irradiation. The layer structure and layer composition of the films before and after ion irradiation were studied by XRR, RBS and RBS-C techniques. The interdiffusion and intermixing was analyzed. No visible change in the RBS spectra was observed upon irradiation with ion fluence below 1015 Kr cm−2. The bi-layer structure and the stoichiometric Fe3O4 layer on the surface were well preserved after Kr+ ion irradiation at low damage levels, although the strong intermixing implied a large interfacial (FexOy) and (Fe, Mg)Oy layer respective at Fe3O4–Fe and Fe–MgO interface. The high ion fluence of 3.8 × 1016 Kr cm−2 has induced a complete oxidization of the buffer Fe layer. Under such Kr fluence, the stoichiometry of the Fe3O4 surface layer was still preserved indicating its high stability. The entire film contains FexOy -type composition at ion fluence large than 5.0 × 1016 Kr cm−2

Selectivity of the (S)-oxynitrilase from Hevea brasiliensis towards \u3b1- and \u3b2-substituted aldehydes

The performance of (S)-oxynitrilase from Hevea brasiliensis (HbHNL) has been investigated with several \u3b1- and \u3b2-substituted alkyl or alkoxy aldehydes and the results have been compared to the data previously obtained with the (R)-specific enzyme from almonds (PaHNL). With both enzymes there was no chiral discrimination between the enantiomers of the racemic substrates, therefore this reaction cannot be used as a preparative method to achieve both the kinetic resolution of the starting racemic aldehyde and the production of diastereomerically pure (or enriched) cyanohydrins. Additionally, in comparison with the (R)-PaHNL the (S)-selective enzyme from Hevea gave products with higher de, but was more negatively effected by oxygenated substituents

Non-Linear Effects In The Formation Of DNA Damage In Medaka Fish Fibroblast Cells Caused by Combined Action of Cadmium And Ionizing Radiation

Ionizing radiation-induced formation of genomic DNA damage can be modulated by nearby chemical species such as heavy metal ions, which can lead to non-linear dose response. To investigate this phenomenon, we studied cell survival and formation of 8-hydroxyguanine (8-OHG) base modifications and double strand breaks (DSB) caused by combined action of cadmium (Cd) and gamma radiation in cultured medaka fish (Oryzias latipes) fibroblast cells. Our data show that the introduction of Cd leads to a significant decrease in the fraction of surviving cells and to increased sensitivity of cells to ionizing radiation (IR). Cd also appears to cause non-linear increases in radiation-induced yields of 8-OHG and DSB as dose-yield plots of these lesions exhibit non-linear S-shaped curves with a sharp increase in the yields of lesions in the 10–20 μM range of Cd concentrations. The combined action of ionizing radiation and Cd leads to increased DNA damage formation compared to the effects of the individual stressors. These results are consistent with a hypothesis that the presence of Cd modulates the efficiency of DNA repair systems thus causing increases in radiation-induced DNA damage formation and decreases in cell survival