Biosensors based on laccase for detection of commercially reactive dyes

The results obtained using Trametes versicolor laccase modified graphite electrodes for detection of eleven different commercially reactive dyes are presented for the first time herein. The increase in current upon injection of the analyzed substrate was shown to be approximated by Michaelis–Menten type dependence. The calculated kinetic constants were used to evaluate the applicability of the laccase modified graphite electrode for the detection of reactive dyes in textile effluents.This paper was submitted as part of a Special Memorial Issue honoring George-Emil Baiulescu. This paper is part of the project CEEX 77/2006 "Computerized filtration and separation systems activated by ultrasounds and controlled by biosensors for textile processes-FILTSOFTUS'' and was supported by "Romanian Authority for Scientific Research/MATNANTECH''

MALDI-TOF mass spectrometry in textile industry

In this paper are presented the possibilities of using matrix assisted laser desorption ionization time of flight (MALDI-TOF) mass spectrometry in textile industry. MALDI-TOF mass spectrometry it is a convenient, versatile method for characterization and identification of dyes and pigments, and also for characterization of fibers and contaminants of the fabrics.(undefined

Laccase polymerization of amino-phenol compounds

Abstracts of Papers of the American Chemical Society, 229, POLY331, U955-U955, 2005

Acetylations role in tau structure, electrostatics and interactions: molecular dynamics studies

Tau is a microtubule associated protein which stabilizes and promotes the assembly of microtubules in neurons.1 In its functional form it presents minor modifications, such as phosphorylation, but a large variety of post-translational modifications are also possible.2 Tau post-translational modifications are directly related with tau mal-functioning, aggregation and subsequent tauopathies. Investigation on tau hyperphosphorylation has dominated in the past years, since its known role in Alzheimers disease onset and progression. However, acetylation has gained attention, as this process is also responsible for tau pathological aggregation.3-4 Acetylation is a modification that occurs in lysine amino acids, adding an acyl group to the side chain NH moiety.5 This process changes the charge of this residue, making it neutral and consequently modifying the electrostatics of the whole protein. The presence of charged groups and electrostatic interactions are the major contributors for a final protein fold. The absence of these charges, via acetylation, will contribute to significant changes in taus structure and interactions. Molecular Dynamics (MD) simulations take advantage of precise simulation algorithms and present themselves as a robust way to understand biomolecules behavior, conformational preferences and interactions, even for intrinsically disordered proteins such as tau. Through this technique we are following the acetylation impact on the tau structure and its way of binding to the microtubule. In addition, it is intended to unveil the relationship between acetylation and aggregation, which results in tau associated diseases. In the past year, Castro and co-workers shed light on tau properties by predicting its 3D structure and disclosing the interaction pattern with microtubules and the ions from the intracellular fluid1. The present work took this input information to generate acetylated analogs and follow the impact of this modification on taus dynamic behavior.info:eu-repo/semantics/publishedVersio

Staining of wool using the reaction products of ABTS oxidation by Laccase : synergetic effects of ultrasound and cyclic voltammetry

The effects of ultrasound on 2,2′-Azinobis(3-ethylbenzothiazoline-6-sulfonate) enzymatic oxidation by laccase (Trametes villosa) has been studied by means of cyclic voltammetry. The reaction was allowed to proceed in the presence of a piece of wool and the coloration depth of the wool fabric was measured by means of K/S. It was observed that cyclic voltammetry is influenced the dyeing process and higher K/S values were obtained when the cyclic voltammetry was combined with the ultrasonic irradiation. Moreover, the K/S value is the sum of the values obtained when the wool staining is done in just the presence of cyclic voltammetry or in just the presence of ultrasound. The results obtained on the indigo carmine decolourization gives information on the importance of controlling the amount of ABTS+ formed during the ultrasonication process

Kinetics of direct and substrate-mediated electron transfer of versatile peroxidase-modified graphite electrodes

Electron transfer (ET) of versatile peroxidase (VP) was studied in the bioelectrocatalytic reduction reaction of H2O2 at peroxidase- modified graphite electrodes to obtain additional information on the kinetic characteristics of this novel ligninolytic peroxidase. Rotating disk electrodes (RDE) experiments were performed at 0 V (vs. SCE) in two different buffers (tartrate buffer, pH 5.0; and citrate buffer, pH 3.0). From measurements of the mediated and mediatorless currents of H2O2 reduction at the RDE, the percentage of VP molecules involved in direct ET (≈55%) was calculated. The peroxidase-modified electrodes were used for determination of the donor substrates in RDE mode, and the results were interpreted in terms of catalytic efficiencies

Sono-enzymatic polymerization of catechol

"Abstracts of papers presented at the 232nd American Chemical Society National Meeting"The potential of laccase enzymes for polymerizing, crosslinking and functionalizing various compounds was studied extensively and increasing interest has been focused on the application of this enzyme as a new biocatalyst in organic synthesis.[1-6] Laccases (EC 1.10.3.2) are a class of multi-copper-containing oxidoreductase enzymes able to catalyze the transformation of various aromatic compounds, specifically phenols and anilines, through the formation of a free cation radical after the transfer of a single electron to laccase. The radical can further react on non-enzymatic oxidation polymerizing various halogen, alkyl-, alkoxy-substituted anilines and phenols.[7-8] The phenolic derivatives resulting in the production of polymeric aggregates are usually less soluble and much stable than their parent compounds.[9,10] Unfortunately the relatively short catalytic lifetime of the laccases in the polymerization processes and the mass transfer limitations, restrict their applications. This effect can be attributed to the inactivation of the enzyme active site due to phenoxy radicals and polymers produced during enzyme treatment.[11] To overcome this limitations the use of ultrasound, under proper conditions, has shown to enhance significantly the mass transfer as well as the structure stability, substrate binding, and activity of the enzyme.[12,13] Ultrasound alone or in combination with other methods is known to enhance a wide variety of chemical and physical processes, mainly due to the phenomenon known as cavitation in a liquid medium that is the growth and explosive collapse of microscopic bubbles.[14-16] These localized ‘‘hot spots’’ generate high local temperature and pressure rise, capable of decompose water to hydrogen atoms and hydroxyl radicals and of break several chemical bonds.[17,18] Therefore in this work laccase from Trametes villosa was tested in combination with ultrasound to improve the radical polymerization of catechol. A solid-state “in situ” sono-enzymatic synthesis of poly(catechol) was also performed by coloration of wool. The results were analyzed by spectrophotometric and HPLC analyses

Protein disulphide isomerase-assisted functionalization of keratin-based matrices

In living systems, protein disulphide isomerase (PDI, EC 5.3.4.1) regulates the formation of new disulphide bonds in proteins (oxidase activity) and catalyzes the rearrangement of non-native disulphide bonds (isomerase activity), leading proteins towards their native configuration. In this study, PDI was used to attach cysteine-containing compounds (CCCs) onto hair, to enhance compound migration within hair fibre and to trigger protein release. A fluorescent (5(6)-TAMRA)-labelled keratin peptide was incorporated into hair by using PDI. Similarly, PDI promoted the grafting of a cysteine-functionalized dye onto wool, as suggested by matrix-assisted laser desorption and ionization time-of-flight results. These reactions were thought to involve oxidation of disulphide bonds between CCCs and wool or hair cysteine residues, catalyzed by the oxidized PDI active site. On the other hand, PDI was demonstrated to enhance the migration of a disulphide bondfunctionalized dye within the keratin matrix and trigger the release of RNase A from wool fibres’ surface. These observations may indicate that an isomerisation reaction occurred, catalyzed by the reduced PDI active site, to achieve the thiol-disulphide exchange, i.e. the rearrangement of disulphide bonds between CCCs and keratin. The present communication aims to highlight promising biotechnological applications of PDI, derived from its almost unique properties within the isomerase family.We thank to FCT "Fundacao para a Ciencia e Tecnologia" (scholarship SFRH/BD/38363/2007) for providing Margarida Fernandes the grant for PhD studies