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The bacterium Escherichia coli was used as a model microorganism to study the interaction between a model microorganism and the tritium-labeled humic substances (HS) material. The measured amounts of HS that penetrated into the cells under optimum and salt conditions indicated increased penetration of HS into E. coli cells under salt stress.

A conventional UV-vis spectroscopy at pH 3-7 and 25 degree Celsius is employed to study the reactivity of the acido [Ru.sup.II] complexes toward laccase from Coriolus hirsutus. The acido and cyclometalated complexes readily oxidized into the corresponding [Ru.sup.III] species, but differed substantially in reactivity and obey different rate laws.

Laccases are members of a large family of multicopper oxidases that catalyze the oxidation of a wide range of organic and inorganic substrates accompanied by the reduction of dioxygen to water. A new laccase was isolated from the basidiomycete Coriolopsis caperata strain 0677 and its amino-acid sequence was determined. According to its physicochemical properties and spectroscopic features, the laccase from C. caperata is a high redox-potential blue laccase. Attempts to crystallize the native enzyme were unsuccessful. The copper type 2-depleted (T2D) laccase was prepared and crystallized. The structure of T2D laccase from C. caperata was solved at 1.6 Å resolution, and attempts to reconstruct the T2 copper centre were performed using Cu+ and Cu2+ ions. The structure of T2D+Cu+ laccase was solved at 1.89 Å resolution. It was shown that the T2D+Cu+ laccase structure contained four copper ions in the active site. Reconstruction could not be achieved when the T2D laccase crystals were treated with CuSO4. [ABSTRACT FROM AUTHOR]

Mycotoxins are low molecular weight fungal metabolites that pose a threat as toxic contaminants of food products, thereby necessitating their effective monitoring and control. Microplate ELISA can be used for this purpose, but this method is characteristically time consuming, with a duration extending to several hours. This report proposes a variant of the ELISA method for the detection and quantification of three mycotoxins, ochratoxin A, aflatoxin B1 and zearalenone, in the kinetic regime. The main requirement for the proposed kinetic protocol was to provide a rapid method that combined sensitivity and accuracy. The use of biotin with an extended spacer together with a streptavidin-polyperoxidase conjugate provided high signal levels, despite these interactions occurring under non-equilibrium conditions. Duration of the individual mycotoxin assays was 20 min, whereas the analysis of all three mycotoxins in parallel reached a maximum duration of 25 min. Recovery of at least 95% mycotoxins in water-organic extracts was shown. The developed assays were successfully validated using poultry processing products and corn samples spiked with known quantities of mycotoxins. The detection limits for aflatoxin B1, ochratoxin A and zearalenone in these substances were 0.24, 1.2 and 3 ng/g, respectively. [ABSTRACT FROM AUTHOR]

This paper describes the structural analysis of the native form of laccase from Trametes hirsuta at 1.8 Å resolution. This structure provides a basis for the elucidation of the mechanism of catalytic action of these ubiquitous proteins. The 1.8 Å resolution native structure provided a good level of structural detail compared with many previously reported laccase structures. A brief comparison with the active sites of other laccases is given. [ABSTRACT FROM AUTHOR]

An addendum to the article "Rapid Multiple Immunoenzyme Assay of Mycotoxins," by A. E. Uruzov and colleagues published om the June 11, 2015 issue is presented.

Laccase from the fungus Coriolus hirsutus has been purified. Crystals of the enzyme suitable for X-ray structure analysis have been obtained under optimized crystallization conditions using polyethylene glycol as a precipitant. The crystals belong to space group P2(1)2(1)2(1), with unit-cell parameters a = 50.65, b = 74.01, c = 124.83 A, and contain 40% solvent and a single molecule of laccase in the asymmetric unit. X-ray data were collected to 1.85 A at the copper edge and the four copper sites have been located from the anomalous signal. The obtained SAD phases with subsequent density modification produced a promising initial electron-density map.