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Optical methods (spectroscopy, spectrofluorometry, dynamic light scattering, and refractometry) were used to study the change in the state of hen egg-white lysozyme (HEWL), protein molecules, and gold nanoparticles (AuNPs) in aqueous colloids with changes in pH, and the interaction of protein molecules with nanoparticles was also studied. It was shown that changing pH may be the easiest way to control the protein corona on gold nanoparticles. In a colloid of nanoparticles, both in the presence and absence of protein, aggregation–deaggregation, and in a protein colloid, monomerization–dimerization–aggregation are the main processes when pH is changed. A specific point at pH 7.5, where a transition of the colloidal system from one state to another is observed, has been found using all the optical methods mentioned. It has been shown that gold nanoparticles can stabilize HEWL protein molecules at alkaline pH while maintaining enzymatic activity, which can be used in practice. The data obtained in this manuscript allow for the state of HEWL colloids and gold nanoparticles to be monitored using one or two simple and accessible optical methods. [ABSTRACT FROM AUTHOR]

Myeloperoxidase (MPO) is an oxidant-producing enzyme that can also regulate cellular functions via its nonenzymatic effects. Mature active MPO isolated from normal human neutrophils is a 145 kDa homodimer, which consists of 2 identical protomers, connected by a single disulfide bond. By binding to CD11b/CD18 integrin, dimeric MPO induces neutrophil activation and adhesion augmenting leukocyte accumulation at sites of inflammation. This study was performed to compare the potency of dimeric and monomeric MPO to elicit selected neutrophil responses. Monomeric MPO (hemi-MPO) was obtained by treating the dimeric MPO by reductive alkylation. Analysis of the crucial signal transducer, intracellular [Ca.sup.2+], showed that dimeric MPO induces [Ca.sup.2+] mobilization from the intracellular calcium stores of neutrophils and influx of extracellular [Ca.sup.2+] whereas the effect of monomeric MPO on [Ca.sup.2+] increase in neutrophils was less. It was also shown that monomeric MPO was less efficient than dimeric MPO at inducing actin cytoskeleton reorganization, cell survival, and neutrophil degranulation. Furthermore, we have detected monomeric MPO in the blood plasma of patients with acute inflammation. Our data suggest that the decomposition of dimeric MPO into monomers can serve as a regulatory mechanism that controls MPO-dependent activation of neutrophils and reduces the proinflammatory effects of MPO. Key words: monomeric myeloperoxidase, dimeric myeloperoxidase, inflammation, neutrophils, oxidative/halogenative stress. La myeloperoxydase (MPO) est une enzyme generant des composes oxydants qui peut aussi reguler la fonction des cellules immunitaires et non immunitaires par ses effets non enzymatiques. La MPO active mature isolee des neutrophiles humain normaux est un homodimere de 145 kDa, qui consiste en 2 protomeres identiques, joints par un seul pont disulfure. En se liant a l'integrine CD11b/CD18, la MPO dimere induit l'activation et l'adhesion des neutrophiles, accroissant l'accumulation de ces leucocytes aux sites inflammatoires. Cette etude a ete realisee pour comparer le pouvoir de la MPO sous formes dimere et monomere a provoquer des reponses selectionnees chez le neutrophile. La MPO monomere (hemi-MPO) a ete obtenue en soumettant la MPO dimere a une alkylation reductrice. L'analyse du signal de transduction essentiel, le [Ca.sup.2+] intracellulaire, montrait que la MPO dimere induisait la mobilisation de [Ca.sup.2+] des reserves intracellulaires des neutrophiles et un influx de [Ca.sup.2+] extracellulaire, alors que l'effet de la MPO monomere sur le [Ca.sup.2+] etait moindre. Il s'averait que la MPO monomere etait moins efficace que la MPO dimere a induire la reorganisation du cytosquelette d'actine, la survie cellulaire et la degranulation des neutrophiles. De plus, les auteurs ont detecte de la MPO monomere dans le plasma de patients souffrant d'inflammation aigue. Leurs donnees suggerent que la decomposition de la MPO dimere en monomeres peut servir de mecanisme regulateur qui controle l'activation des neutrophiles dependante de la MPO et reduit les effets pro-inflammatoires de la MPO. [Traduit par la Redaction] Mots-cles : myeloperoxydase monomere, myeloperoxydase dimere, inflammation, neutrophiles, stress oxydant/halogenant., Introduction Myeloperoxidase (MPO; EC 1.11.2.2) is a heme-containing glycosylated oxidoreductase, which displays the halogenating activity catalyzing the 2-electron oxidation of halides ([Cl.sup.-], [Br.sup.-], and [I.sup.-]) and pseudohalide ([SCN.sup.-]) in the [...]

Myeloperoxidase (MPO), found mainly in neutrophils, is released in inflammation. MPO produces reactive halogen species (RHS), which are bactericidal agents. However, RHS overproduction, i.e., halogenative stress, can also damage host biomolecules, and MPO itself may be targeted by RHS. Therefore, we examined the susceptibility of MPO to inactivation by its primary products (HOCl, HOBr, HOSCN) and secondary products such as taurine monochloramine (TauCl) and taurine monobromamine (TauBr). MPO was dose-dependently inhibited up to complete inactivity by treatment with HOCl or HOBr. TauBr diminished the activity but did not eliminate it. TauCl had noeffect. MPO became inactivated when producing HOClorHOBr but not HOSCN. Taurine protected MPO against inactivation when MPO was catalyzing oxidation of [Cl.sup.-] to HOCl, whereas taurine failed to prevent inactivation when MPO was working with [Br.sup.-], either alone or in combination with [Cl.sup.-]. [SCN.sup.-] interfered with HOCl-mediated MPO inhibition. UV-vis spectra showed that heme degradation is involved in HOCl- and HOBr-mediated MPO inactivation. A negative linear correlation between the remaining chlorinating activity of HOCl- or HOBr-modified MPO and Escherichia coli survival upon incubation with MPO/[H.sub.2][O.sub.2]/[Cl.sup.-] was found. This study elucidated the possibility of MPO downregulation by MPO-derived RHS, which could counteract halogenative stress. Key words: halogenative stress, reactive halogen species, myeloperoxidase, enzymatic activity, bactericidal activity. La myeloperoxydase (MPO) trouvee principalement dans les neutrophiles est liberee lors de l'inflammation. La MPO produit des derives reactifs d'halogenes (DRH) qui agissent comme agents bactericides. Cependant, la surproduction de DRH, c.-a-d. le stress halogenant, peut aussi endommager les biomolecules de l'hote, et la MPO elle-meme peut etre ciblee par les DRH. Consequemment, les auteurs ont examine la susceptibilite de la MPO a l'inactivation par ses produits primaires (HOCl, HOBr, HOSCN) et secondaires comme la monochloramine de taurine (TauCl) et la monobromamine de taurine (TauBr). La MPO etait inhibee de maniere dependante de la concentration jusqu'a une inactivite complete par un traitement au HOCl ou au HOBr. La TauBr diminuait l'activite de la MPO mais ne l'eliminait pas. La TauCl n'exercait pas d'effet. La MPO devenait inactivee en produisant du HOCl et du HOBr, mais pas du HOSCN. La taurine protegeait la MPO de l'inactivation lorsqu'elle catalysait l'oxydation du [Cl.sup.-] en HOCl, alors qu'elle etait incapable de prevenir l'inactivation lorsque la MPO agissait sur le [Br.sup.-], soit seul ou en combinaison avec le [Cl.sup.-]. Les [SCN.sup.-] interferaient avec l'inhibition de la MPO dependante du HOCl. Les spectres UV-vis montraient que la degradation de l'heme est impliquee dans l'inactivation de la MPO par le HOCl et le HOBr. Une correlation lineaire negative entre l'activite de chloration residuelle de la MPO modifiee par le HOCl ou le HOBr et la survie de Escherichia coli incube en presence de MPO/[H.sub.2][O.sub.2]/[Cl.sup.-] a ete trouvee. Cette etude a elucide a possibilite d'une regulation negative de la MPO par les DRH derives de la MPO, ce qui pourrait contrecarrer le stress halogenant. [Traduit par la Redaction] Mots-cles : stress halogenant, derives reactifs d'halogenes, myeloperoxydase, activite enzymatique, activite bactericide., Introduction The enzyme myeloperoxidase (MPO; chloride:hydrogen-peroxide oxidoreductase, EC 1.11.2.2), a heme-containing glycoprotein of 145 kDa, is found in leukocytes, mainly neutrophils, where it is present in high amounts as a [...]

The article is devoted to the study of melted ingots, plates rolled from them, and the resulting spherical powder made of corrosion-resistant 316L steel with the addition of 0.2 wt.% and 0.5 wt.% Ag. The study of antibacterial properties, microstructure, and distribution of silver concentrations, as well as qualitative analysis of silver content was carried out. The optimal mode of homogenization annealing of the ingot was 1050 °C for 9 h, which leads to the formation of an austenitic structure. It is shown that the addition of a small amount of silver does not affect the formation of the austenitic structure and silver is distributed evenly throughout the volume of the ingot. The austenitic structure also prevails in the plates after rolling. Silver is distributed evenly throughout the entire volume of the plate. It is noted that the addition of 0.2 wt.% Ag does not affect the strength, elongation, and microhardness of steel, and the addition of 0.5 wt.% Ag does not significantly reduce the strength of steel, however, all samples meet the mechanical characteristics according to the ASTM A240 standard. The qualitative chemical composition of samples made of corrosion-resistant steels was confirmed by X-ray fluorescence analysis methods. By the method of energy-dispersion analysis, the presence of a uniform distribution of silver over the entire volume of the powder particle was determined. The particles have a spherical shape with a minimum number of defects. The study of the antibacterial activity of plates and powder shows the presence of a clear antibacterial effect (bacteria of the genus Xanthomonas campestris, Erwinia carotovora, Pseudomonas marginalis, Clavibacter michiganensis) in samples No. 2 and No. 3 with the addition of 0.2 wt.% and 0.5 wt.% Ag. [ABSTRACT FROM AUTHOR]