Microscopic model of diffusion limited aggregation and electrodeposition in the presence of levelling molecules

A microscopic model of the effect of unbinding in diffusion limited aggregation based on a cellular automata approach is presented. The geometry resembles electrochemical deposition - ``ions'' diffuse at random from the top of a container until encountering a cluster in contact with the bottom, to which they stick. The model exhibits dendritic (fractal) growth in the diffusion limited case. The addition of a field eliminates the fractal nature but the density remains low. The addition of molecules which unbind atoms from the aggregate transforms the deposit to a 100% dense one (in 3D). The molecules are remarkably adept at avoiding being trapped. This mimics the effect of so-called ``leveller'' molecules which are used in electrochemical deposition

Sensitive Detection of Organophosphorus Pesticides Using a Needle Type Amperometric Acetylcholinesterase-based Bioelectrode. Thiocholine Electrochemistry and Immobilised Enzyme Inhibition

International audienceAn acetylcholinesterase (AChE) based amperometric bioelectrode for a selective detection of low concen¬ trations of organophosphorus pesticides has been developed. The amperometric needle type bioelectrode consists of a bare cavity in a PTFE isolated Pt-Ir wire, where the AChE was entrapped into a photopolymerised polymer of polyvinyl alcohol bearing styrylpyridinium groups (PVA-SbQ). Cyclic voltammetry, performed at Pt and AChE/Pt disk electrodes, confirmed the irreversible, monoelectronic thiocholine oxidation process and showed that a working potential of + 0.410 V vs. Ag/AgCl, KClSat was suitable for a selective and sensitive amperometric detection of thiocholine. The acetylthio-choline detection under enzyme kinetic control was found in the range of 0.01-0.3 U cm~" of immobilised AChE. The detection limit, calculated for an inhibition ratio of 10%, was found to reach 5 jxM for dipterex and 0.4 jaIVI for paraoxon. A kinetic analysis of the AChE-pesticide interaction process using Hanes-Woolf or Lineweaver-Burk linearisations and secondary plots allowed identification of the immobilised enzyme inhibition process as a mixed one (non/uncompetitive) for both dipterex and paraoxon. The deviation from classical Michaelis Menten kinetics induced from the studied pesticides was evaluated using Hill plots

Abstract 579: <i>In vitro</i> Models Concur With Clinical Results to Confirm Pleiotropic Mechanisms of Action for Gemcabene

Introduction: Gemcabene, a fraudulent fatty acid, induces biological properties in nonclinical models, of which many translate to clinical findings in dyslipidemia patients. Its known mechanism of action includes reduction of the overall hepatic de novo triglyceride and cholesterol synthesis, and increase in VLDL clearance. Clinical benefits in various human populations infer that other mechanisms are involved that warrant evaluation. Methods and Results: We assessed the gemcabene effects in other molecular mechanistic models, particularly to study inhibition of human ATP Citrate Lyase (hACL), apolipoprotein gene expression in Sandwich-Cultured Transporter Certified TM Human Hepatocytes (SCHH), and expression of genes related to inflammation and cell signaling. Gemcabene, MEDICA-16, palmitic acid and their CoA thioesters were studied in a recombinant hACL in vitro assay system. Gemcabene-CoA thioester, but not the parent compound, inhibited recombinant hACL activity in vitro in a dose-dependent manner, in agreement with results obtained with palmitoyl-CoA and palmitic acid. Unlike palmitic acid, MEDICA-16, and bempedoic acid, gemcabene does not form a CoA ester in human hepatocytes: radioisotope studies show 98.8% parent gemcabene. Further, gemcabene potential on the gene expression of lipogenesis and inflammation markers was assessed in SCHH. Gemcabene showed significant regulation of HMG-CoA synthase 2 (HMGCS2) and CRP mRNAs. A marked induction response of the HMGCS2 mRNA content was observed, ranging from 2.26- to 2.73-fold (p ≤ 0.05) over control in SCHH treated with all concentrations of gemcabene (500, 1000, and 1500 μM). Also, a clear and statistically significant (p-value ≤ 0.05) concentration-related suppression response of CRP mRNA content was observed, ranging from (-2.58)- to (-2.65)-fold below control in SCHH treated with 1000 and 1500 μM gemcabene. Finally, RT-PCR analysis of liver samples from STAM TM mice treated with gemcabene revealed its downregulating effect on inflammatory, lipogenic, lipoprotein metabolism, and cell signaling genes: TNF-α, MCP-1, NF-κB, ApoC-III, and ACC1. Conclusion: Gemcabene manifests its pharmacological profile in lipid management and inflammation by multiple mechanisms of action. </jats:p

Effects of additives on zinc electrowinning from industrial waste products

International audienceAn investigation of the effects of some additives on zinc electrowinning from a weak acidic sulphate electrolyte prepared from an industrial waste product has been carried out. Experiments were done in the presence of additives such as aluminium sulphate, animal glue and an extract of horse-chestnut nuts (HCE), used alone or in different mixtures.Using a rotating disc electrode (RDE) and cyclic voltammetry, the influence of the additives on the polarization curves and on the voltammograms was studied. SEM was used to determine the structure and the morphology of deposits.The results indicated that the additives tested exert a beneficial effect on the quality of the zinc deposits. They increase the cathodic polarization and promote levelling. Al2(SO4)3 influences the reduction of zinc ions, increasing the nucleation overpotential and the deposition rate of zinc on the cathode. The conjoint use of Al2(SO4)3, animal glue and HCE results in smooth, slightly bright deposits, showing a beneficial effect of the mixture on zinc electrodeposition. The analysis of deposit purity suggested that the additives inhibit the discharge rate of impurity metal ions, such as copper and lead, whose deposition is diffusion controlled