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Abstract: Acrylic polymers with catalytic activity for the oxidative degradation of 2,4,6-trichlorophenol (TCP) were developed. In order to mimic the active site of chloroperoxidase (CPO), chloro-iron(III)-protoporphyrin IX was used as the catalytic centre, and methacrylamide (MA) and 4-vinylpyridine (VPY) were used as the monomers that build up the active sites. Taking as basis 3:1 (w/w) acid:basic aminoacidic composition of CPO, three MA:VPY combinations were tested: one keeping the same ratio (3:1) i.e. 25% VPY in the functional monomer mixture, one with lower content of the basic monomer (9:1) i.e. 10% VPY, and one with higher concentration of it (1:1) i.e. 50% VPY. Polymers synthesized with the lowest VPY content exhibited the highest catalytic efficiency, which was improved by the creation of specific TCP binding sites through molecular imprinting technology. In these way, synthetic enzymes with useful properties for analytical and bioremediation applications were obtained. [Copyright &y& Elsevier]

Abstract: A sigmoidal behaviour of chloroperoxidase for the oxidative dehalogenation of 2,4,6-trichlorophenol is reported for the first time. Kinetic data were adjusted to the Hill equation and the kinetic parameters were obtained: n =1.7±0.2, , the pseudo-Michaelis constant K s*=(8.6±0.5)×10−5 M, k cat =677±84min−1 and the catalytic efficiency=(8.9±0.6)×106 M−1 min−1. The sigmoidal curve could be related to the cooperative binding of the substrate to the enzyme, so that the binding of the first substrate molecule may help the binding of the second one. Further, both substrate molecules could establish Π–Π interactions between them, which would confer more stability to the system. [ABSTRACT FROM AUTHOR]

Abstract: The synthesis, characterization and evaluation of the catalytic properties of a hemin–methacrylamide–ethylene glycol dimethacrylate copolymer are described. This polymer catalyzes the oxidative dechlorination of 2,4,6-trichlorophenol (TCP) in the presence of hydrogen peroxide, yielding 2,6-dichloro-1,4-benzoquinone as the main reaction product. This low-cost material allows the complete removal of TCP from water at concentration level of 20mgL−1 in less than 30min. [Copyright &y& Elsevier]

Abstract: We have studied the potential electrocatalytic activity towards the oxidation of NADH of several oxidation products of guanine and its derivative guanosine-5′-monophosphate (5′-GMP) on pyrolytic graphite electrodes (PGE). The distribution of products generated strongly depends on the experimental conditions. Our investigations focused on the oxidation products that are adsorbed on the electrode surface, are redox active and, exhibited electrocatalytic activity toward the oxidation of NADH. These compounds were electrochemically and kinetically characterized in terms of dependence of the formal potential on pH and electron transfer rate constant (k s). The voltammetric and catalytic behavior of both guanine and 5′-GMP oxidation products was compared with that of other guanine derivatives we have previously studied. Some mechanistic aspects concerning the generation of the catalysts are also discussed. [Copyright &y& Elsevier]

Abstract: We herein explore a novel route for oxidative stress in DNA by using electrochemistry as mimicking tool. Essentially, the electrochemical oxidation of guanine and adenine nucleosides and oligo-homo-nucleotides at pyrolytic graphite electrodes in neutral and alkaline aqueous solutions was studied. Under these experimental conditions all these compounds give rise to an adsorbed product not previously described, which was electrochemically and kinetically characterized. The virtually identical kinetic and electrochemical features exhibited by the oxidized compounds generated from all precursors strongly suggest a common species arising from both adenine and guanine derivatives. Supported by DFT calculations, we propose two convergent pathways for the electrochemical oxidation of adenosine and guanosine. Those calculations indicate that the common oxidized base product forms stable H-bond base pairs with both thymine and cytosine. [Copyright &y& Elsevier]

Following oxidation of 5-hydroxytryptophan (5-HTPP) at a pyrolytic graphite electrode at pH 7.5, two quasi- reversible redox couples emerge at -0.170 and +0.032 V, respectively, due to oxidation products strongly adsorbed to the electrode surface. These redox processes have been electrochemically and kinetically characterized in terms of the dependence of the formal potential (E°') with pH, variation of the current density with scan rate, operational stability, and electro-transfer rate constant (ks). The wave centered at +0.032 V could mediate the oxidation of NADH, exhibiting a strong and persistent electrocatalytic response. A quinone-imine structure has been proposed as the electrocatalytic active species. The kinetics of the reaction between the mediator and NADH has been characterized via rotating disk electrode voltammetry, and it has been found that the rate constant for the reaction is dependent of the solution concentration of NADH. 5-HTPP modified electrodes could be employed in the amperometric detection of NADU with a limit of detection in the nanomolar range. Moreover, 5-HTPP modified electrodes retain their electrocatalytic activity for at least one week. The potential application of these electrodes to amperometric biosensor is demonstrated. [ABSTRACT FROM AUTHOR]

Abstract: A new and simple electrochemical method capable to detect single-base mutations in DNA has been developed. It relies on the electrocatalytic oxidation of NADH by the intercalator Brilliant Cresyl Blue (BCB). Whereas negligible catalytic responses were obtained with graphite electrodes modified by BCB-single-stranded DNA, high catalytic activity is obtained at electrodes modified by the complexes between double-stranded DNA and BCB. The proposed explanation for these results is that charge transport from the intercalated BCB through the DNA base stack is a necessary event for the electrocatalytic activity as disruption by a single-base mismatch leads to a complete suppression of the electrocatalytic voltammetric response. These finds open new possibilities for the detection of DNA hybridization and mutation. [Copyright &y& Elsevier]