[Mechanism of the toxic action of copper nanoparticles on Escherichia coli bacteria].

Some features of contact interaction of Escherichia coli with Cu nanoparticles 75-100 nm in diameter have been studied. The analysis of variations in the amplitude of fluorescence of the negatively charged probe 1-anilinonaphthalene-8-sulfonate (ANS) in Gouy-Chapmen coordinates indicates an increase (in the absolute value) in the electrostatic potential of E. coli external membrane during the contact with Cu nanoparticles. The increase in the electrostatic potential correlates with the bacteriostatic influence on the growth of bacterial population. The calculations of tryptophan fluorescence quenching by iodide in the presence of Cu nanoparticles with the use of the Stern-Volmer equation revealed an increase in the constant of dynamic quenching and the availability of the fluorophore to suppressor.

[Structural modifications of the surface of Escherichia coli bacteria and copper-induced permeability of plasma membrane].

The effect of Cu2+ on the structural organization of the cell surface of Escherichia coli bacteria during the induction of conductivity of a plasma membrane was studied. A fluorescent study did not reveal any substantial changes in the microviscosity of lipids by the action of copper ions. At the same time, a substantial reorganization of membrane proteins during plasmolysis was observed. A model of the copper-induced structural reorganization of membrane lipids was constructed, according to which the reorganization leads to the opening in the membrane of channels of nonspecific conductivity for cations. The opening of conductivity channels results from the break of disulfide bonds in critical membrane proteins during the interaction with Cu+, which form either due to the reduction of Cu2+ on specific sites of cell surface or by means of external reducing agents.

[The role of reactive oxygen species in copper-induced permeability of plasma membranes in Escherichia coli]. / Rol' aktivnykh form kisloroda v med'-indutsirovannoi pronitsaemosti plazmaticheskoi membrany bakterii Escherichia coli.

The role of active oxygen species in the induction of nonselective cationic permeability of the plasma membrane of bacteria Escherichia coli B by the action of Cu2+ ions was studied. It was found that the increase in the amount of active oxygen species in the suspension after treating cells with copper occurred synchronously with the leakage of K+ cations from them. Evidence is presented that active oxygen species formed during the interaction of copper ions with bacteria under aerobic conditions are not involved in the induction of channel conductivity in the membrane. Moreover, the ability of oxygen to protect the membrane from the toxic action of copper was shown, and the activation of membrane damage by external reductants was confirmed. These data suggest that the barrier properties of the membrane are disturbed during the interaction of Cu+ ions with critical targets on the surface, the concentration of Cu+ being determined by all redox processes in the near-membrane space.

[Reducing centers on the surface of Escherichia coli bacteria and their role in copper-induced plasma membrane permeability]. / Vosstanavlivaiushchie tsentry na poverkhnosti bakterii Escherichia coli i ikh rol' v med'indutsirovannoi pronitsaemosti plazmaticheskoi membrany.

The reducing properties of Escherichia coli and their role in the induction of nonselective cationic permeability of plasma membrane by the action of Cu2+ ions were studied. The ability of cells to reduce exogenous dithiopyridine was shown to be maximal in freshly collected culture and to decrease upon starvation or exhaustion of bacteria by dinitrophenol, in the presence of other oxidants of cell thiols in the medium, and after the disturbance of the barrier properties of membrane by tetrachloracetic acid or butanol. The alkylation of cell thiols accessible for N-ethyl maleimide completely disrupted the reducing activity of bacteria. These data are consistent with the conception that the reduction of dithiopyridine and Cu2+ ions by bacteria occurs on the thiol-containing centers of the cell surface, which are continuously reduced by the transfer of cell reducing equivalents from the inner to the outer surface of plasma membrane. The analysis of data on the effect of external oxidizing and reducing agents on the copper-induced plasmolysis of bacteria showed that the induction of membrane permeability by the action of copper can occur upon interaction with critical targets on the surface of Cu+ ions formed in the periplasmic space in the reaction of Cu2+ ions with reducing centers.

[Cu2+-induced permeability of the Escherichia coli cytoplasmic membrane]. / Cu2+-indutsirovannaia pronitsaemost' tsitoplazmaticheskoi membrany Escherichia coli.

Cu(2+)-induced permeability of cytoplasmic membranes of Escherichia coli for different cations and neutral molecules of saccharose was estimated by studying their effect on cell plasmolysis during uncharged exchange of cytoplasmic K+ ions by periplasmic space cations. The addition of copper resulted in the exchange of K+ ions by periplasmic Na+, Tris+, streptomycin2+, Cu2+, Ca2+, Mg2+, Cd2+, and Mn2+. It is concluded that Cu(2+)-induced conducting pathways in bacterial membranes are hydrophilic channels with a radius of approximately 0.5 nm and a nonselective permeability for different cations.

[Analysis of the binding site of copper with intact and Escherichia coli bacteria modified by N-ethylmaleimide by ESR]. / Analiz mest sviazyvaniia medi s intaktnymi i modifitsirovannymi N-étilmaleimidom bakteriiami Escherichia coli metodom EPR.

Characteristics of copper binding sites in the bacteria E. coli were studied using ESR spectroscopy. It was found that these cations had high local density on the strong binding range represented by the two type sites. The former include nitrogen and oxygen ligands and the second ones--sulfur of the thiol biomolecules. The weak coupling Cu(II) sites of E. coli represent more polar nitrogen-oxygen environment. Blocking SH-groups by N-ethylmaleimide makes them inaccessible for copper ligation, sharply increases the percentage of ESR-detectable copper of the strong-binding sites and prevents the membrane breakdown by these cations. The results suggest that the Cu(2+)-induced membrane damage is the effect of Cu2+ binding with the SH-containing sites of the bacterial membrane.

[The role of oxygen in the inhibition of Escherichia coli respiration by copper ions]. / Rol' kisloroda v ingibirovanii dykhaniia Escherichia coli ionami medi.

Effect of Cu2+ on E. coli respiration and the role of oxygen in toxic action of copper has been studied. Stimulation of respiration is observed at initial time after introduction of Cu2+. It is based on a nonspecific cell response to membrane damage. After finishing of transitory processes, Cu2+ influenced respiration by noncompetitive inhibition, i.e. copper-sensitive enzyme can be oxygenated or nonoxygenated, and only the latter form of the enzyme is inhibited.

[The copper-dependent accumulation of magnesium in Escherichia coli]. / Med'-zavisimoe nakoplenie magniia v Escherichia coli.

Cu2(+)-induced accumulation of Mg ions by E. coli cells has been studied. The accumulation was demonstrated to take place only when the cell had endogenous energetic resources. The data obtained and their correlation with the data on Cu2+ binding by bacterial cells and Cu2(+)-dependent streptomycin accumulation allowed to conclude that copper induced nonspecific potential-dependent influx of cations into cells.

[Heavy metal cation-induced increase in the antimicrobial activity of gramicidin S. Increased sensitivity of metal-resistant mutants of Escherichia coli B to the antibiotic]. / Usilenie antimikrobnoi aktivnosti gramitsidina S kationami tiazhelykh metallov. Povyshennaia chuvstvitel'nost' k antibiotiku metallorezistentnykh mutanyov Escherichia coli B.

Gramicidin S response of metal resistant mutants of E. coli B and the effect of concentrations of Cu2+, Ag+, Co2+ and Cd2+ on the growth and sensitivity of E. coli B to cationic antibiotics, i.e. gramicidin S2+ and streptomycin2+, were studied. It was shown that the metal-cumulating mutants of E. coli B with two different mechanisms of cross resistance to Cu2+, Cd2+ and Ag+ had higher sensitivity to gramicidin S than the initial wild type strain of E. coli B. It was found that in the threshold or higher doses the salts of Cu, Ag, Co and Cd increased the gramicidin S antimicrobial action on actively metabolizing cells of E. coli B. Analysis of the experimental data as well as the literature ones suggested that the synergic action of gramicidin S and the heavy metals stemmed from an increase in the cationic conductivity of the cytoplasma membrane modified by the metals in the threshold doses which induced an increase in the transport and accumulation of the cations in the bacterial cells by the electric field gradient (with the negative sign inside). Withdrawal of Ca2+ and Mg2+ from the E. coli outer structures into the cytoplasm impaired the barrier properties of the outer membrane and promoted binding of the gramicidin S cations to the liberated anionic groups of the E. coli outer structures and potentiation of the gramicidin S antimicrobial activity as was shown in our experiments.

[The trace element composition of the organs and tissues of animals administered a highly dispersed powder and copper sulfate]. / Mikroélementnyi sostav organov i tkanei zhivotnykh pri vvedenii vysokodispersnogo poroshka i sul'fata medi.

Changes in the content of microelements in blood, heart and liver after a single subcutaneous injection of aquatic suspension of highly dispersed powder and copper sulphate in different doses were investigated. Injection of highly dispersed powder and copper sulphate was shown increase phase fluctuations of copper, zinc and iron level in all organs under study. It was demonstrated that irrespective of the form and dose of injection copper does not break interrelation modus between zinc and copper, characteristic of the control and does not change zinc/copper ratio. Bioavailability of highly dispersed copper powder injected in organism at the dose 0.2 mg/kg was found to be somewhat higher than that of sulphate.

[The effect of CuCl2 on the efflux of inorganic phosphate from Escherichia coli]. / Vliianie CuCl2 na utechku neorganicheskogo fosfata iz Escherichia coli.

The influence of CuCl2 on inorganic phosphate efflux from resting E. coli and those treated with glucose has been studied. Maintaining of high phosphate gradient on the membrane is possibly only in case of continuous supply of external metabolic energy. Treatment with CuCl2 does not lead to the increase in permeability of the resting cell membrane for phosphates, but it causes the efflux of phosphates in glucose-treated cells. The above data suggest that the efflux is determined by inhibition of energy influx into cell by CuCl2, not by damaging the cytoplasmic membrane.

[Changes in the level of sulfhydryl groups in the organs and blood of mice administered a highly dispersed iron powder against a background of developing anemia]. / Izmenenie urovnia sul'gidril'nykh grupp v organakh i krovi myshei pri vvedenii vysokodispersnogo poroshka zheleza na fone razvitii anemii.

Alimentary iron deficiency causes significant changes in thiol content: the increase in the content of protein sulfhydryl groups in organs at late stages and the decrease in that of non-protein sulfhydryl groups at early stages of experiment. A preliminary introduction of 10 mg/kg fine iron powder (FIP) into animals fed iron-free food leads to the decrease in sulfhydryl group content in organs and blood of experimental mice. The decrease in sulfhydryl group content at FIP introduction might be connected with changes in activity of glutathione-dependent enzymes.

[The role of surface and transmembrane potentials in copper binding by Escherichia coli cells]. / Rol' poverkhnostnogo i transmembrannogo potentsialov v sviazyvaniia medi kletkami Escherichia coli.

Cu2+-induced accumulation of Mg2+ ions by E. coli cells has been studied. The accumulation was demonstrated to take place only when the cell had endogenous energy resources. The data obtained and their correlation with the data on Cu2+ binding by bacterial cells and Cu2+-dependent streptomycin accumulation allowed to conclude that copper induced nonspecific potential-dependent influx of cations into cell.

[Effect of a highly dispersed copper powder on superoxide dismutase and glutathione peroxidase activities in experimental myocardial infarct]. / Vliianie vysokodispersnogo poroshka medi na aktivnost' superoksiddismutazy i glutationperoksidazy pri éksperimental'nom infarkte miokarda.

Administration of highly dispersed copper powder in a dose 0.2 mg/kg three days before modelled coronary-occlusion myocardial infarction caused transitory increase in activity of antioxidant enzymes--superoxide dismutase and glutathione peroxidase in the necrotic zone of myocardium of rats, and also staunch increase in the activity of these enzymes in noninfarction region.

[The effect of surface and membrane potential on 1-anilino-8-naphthalenesulfonate binding with E. coli membrane]. / Vliianie poverkhnostnogo i membrannogo potentsiala na sviazyvanie 1-anilino-8-naftalinsul'fonata s membranoi E. coli.

Dependence of ANS fluorescence on the surface potential of E. coli under lowered resistance of the bacterial membrane and after application of the positive diffusion potential inside the cell was investigated. It was shown that in the absence of the latter ANS binding in de-energised bacteria occurs mainly at the outside surface. It may be due to the high negative charge of the inner side of the cytoplasmic membrane. According to produced evaluation the potential of this surface is 120 +/- 25 mV. The data obtained suggest that low ANS fluorescence in intact cells is due to the membrane modification on energisation.

[Characteristics of copper-induced streptomycin transport in Escherichia coli]. / Zakonomernosti indutsirovannogo med'iu transporta streptomitsina v Escherichia coli.

Copper dependent uptake of streptomycin by resting E. coli cells was studied. It was shown that copper stimulates the aminoglycoside uptake only when bacteria possess endogenic energy sources. Additional accumulation of positive charged molecules of the antibiotic is accompanied by partial depolarisation of the membrane, its steady state distribution between cells and the medium corresponding to the resulted value of the membrane potential. On the basis of the data obtained it was suggested that under the influence of copper membrane permeability for streptomycin increases.