Analysis and toxicity of methomyl and ametryn after biodegradation

The controlled biodegradation of ametryn and methomyl has been performed, in accordance with the OECD Zahn-Wellens/EMPA procedure, by use of an enriched mixture of activated sludge collected from three domestic waste-water-treatment plants (WWTP). During the process concentrations of ametryn and methomyl in the water samples were isolated by solid-phase extraction (SPE); recovery rates were 98.9 and 93.2 for methomyl and ametryn, respectively. Liquid chromatography-mass spectrometry (LC-MS) was used to determine final pesticide concentrations and for metabolite identification.The efficiency of aerobic biodegradation of ametryn and methomyl was evaluated by measuring both the decrease in the concentration of the pesticides and global properties such as the chemical oxygen demand (COD). The acute toxicity of ametryn and methomyl was evaluated by use of the ToxAlert100 biological test, which is based on inhibition of the bioluminescence of Vibrio fischeri. There was significant correlation between results from primary and ultimate biodegradation and those from determination of toxicity. Pesticide concentrations were always reduced to below the limit of detection in less than 17 days. High COD removal (90-96%) was achieved in 28 and 18 days for methomyl and ametryn, respectively.     

Core/valence partition and relativistic effects in effective potentials for transition metals

Two different versions, relativistic and nonrelativistic, of the “shape-consistent” effective potential (EP ) formalism are analyzed in ab initio calculations for transition metals. The influence of alternative core/valence partitions on the reliability of the procedure is discussed. The accuracy of EP results for transition metals is shown to depend on adequate choices of the valence subspace and proper inclusion of relativistic effects.     

Major histocompatibility complex (MHC) protein analysis by optimised two-dimensional electrophoretic methods

Human histocompatibility molecules HLA-Class I and Class II (DR, DQ, DP) were analysed using three two-dimensional protocols: nonequilibrium pH gradient electrophoresis (NEPHGE), isoelectric focusing-acidic gradient (IEF-AG) and isoelectric focusing-basic gradient (IEF-BG). The three methods differ in their carrier ampholyte combinations and electrophoretic conditions. They provide different pH gradients and therefore different electrofocusing profiles. The NEPHGE protocol was adequate for separating proteins across a broad range of pI mobilities, i.e. 4.4 pH units between the acidic and the basic end. In contrast, the IEF-AG and the IEF-BG protocols gave a separation power across a narrow pH range, 1.9 and 1.7 pH units respectively. Thus, whereas the NEPHGE protocol provides a tool for a global major histocompatibility complex (MHC) antigen profile analysis, the IEF-AG and -BG allows one to investigate subcomponents of the individual MHC chains. For example, NEPHGE analysis of the HLA Class I heavy chain revealed a single spot. However, IEF-BG revealed the presence of six equidistantly spaced spots spanning a short pH gradient with identical molecular weight. Similar improved resolution was seen for the HLA-DR, DQ, and DP molecules. The IEF acidic gradient was adequate for separating the alpha chain; the IEF basic gradient gave better resolution of the beta chains. This data provides a baseline set of conditions for both analytical and preparative MHC protein studies prior to amino acid sequencing.     

Hydrolytic protein cleavage mediated by unusual mononuclear copper(II) complexes: X-ray structures and solution studies

The crystal structures and redox and UV-vis/EPR spectroscopic properties of two new mononuclear copper(II) complexes, [Cu(HL1)Cl2] (1) and [Cu(L1)Cl] (2), prepared through the reaction between copper(II) chloride and the ligand 2-[(bis(pyridylmethyl)amino)methyl]-4-methyl-6-formylphenol (HL1) under distinct base conditions, are reported along with solution studies. Also, we demonstrate that these CuII complexes are able to cleave unactivated peptide bonds from bovine serum albumin (BSA) and the thermostable enzyme Taq DNA polymerase at micromolar concentration, under mild pH and temperature conditions. The cleavage activity seems to be specific with defined proteolytic fragments appearing after protein treatment. The location of the specific cleavage sites was tentatively assigned to solvent-accessible portions of the protein. These are two of the most active Cu(II) complexes described to date, since their cleavage activity is detected in minutes and evidence is here presented for a hydrolytic mechanism mediating protein cleavage by these complexes.     

Nitrite catalyzes reductive nitrosylation of the water-soluble Ferri-Heme model FeIII(TPPS) to FeII(TPPS)(NO)

Quantitative investigation of the reaction of the ferri-heme model compound Fe(III)(TPPS)(H(2)O)(2) (1) to give Fe(II)(TPPS)(NO) (2) (TPPS = tetra(4-sulfonato-phenyl)porphinato) in buffered aqueous solution demonstrates a slow pH-independent reductive nitrosylation pathway in the pH range 4-6. The rate of this reaction is subject to modest general base catalysis. In the course of this study, a surprising catalytic pathway whereby nitrite ion (NO(2)(-)) strongly catalyzes the reduction of 1 to 2 under reductive nitrosylation conditions was demonstrated.