The influence of physical-chemical characteristics of surface modified copper nanoparticles on E. coli cell population growth suppression and on electrostatic properties of their membranes
The biological activity of copper nanoparticles, able to suppress growth of E. coli cells population under contact interactions, was explored. Three types of samples with oxide layers of various sizes, thickness and composition were used in experiments. It was found out, that an increase in electron density on the external membrane of E. coli correlated with copper nanoparticles suppression capability and with lower activation energy of electron transfer on bacteria. The analysis of experimental data helps to correct conditions for obtaining nanoparticles with certain properties of their surface oxide layers. The character of temperature dependence of electron density reveals the electron type of conductivity in contact area of E. coli and nano-particles. These results help to find approach to understanding the nature of toxic influence of copper nano-particles on E. coli cells under contact interaction.
Influence of a finely dispersed suspension based on a metal/carbon nanocomposite of copper on growth processes and seeds infection of spring wheat
The article presents the results of laboratory studies on the treatment of spring wheat seeds of the Svecha variety with a fine suspension based on a metal/carbon nanocomposite of copper (MeC NC Cu). The aim of the research is to identify the fungicidal action and stimulate the growth processes of plants at the initial stage of organogenesis. The experimental results showed that the effect of copper nanocomposite on plants is ambiguous and in some cases contradictory. This nanomaterial at a concentration of 0.1% had a toxic effect on the seeds of Triticum aestivum. The drug at a concentration of 0.005% (by 15.7%) had a weak stimulating, but insignificant, effect on root development. It was revealed that an increase in the concentration of MeC NC Cu has an inhibitory effect on plants: the immune system weakens and the resistance to pathogens of seed infection decreases. Development of Bipolaris sorokiniana Syn. increases by 2.90-3.31%, Alternaria sp. - by 1.94%. With an increase in the concentration of NC to 1.00%, the indicators deteriorate in comparison with the control to 3.06%. Infection of seeds with a fungus of the genus Fusarium was observed in the following variants: MeC NC Cu 0.05% by 54.5%, MeC NC Cu 1.0% by 6.90% with the least significant difference (95%) 1.36. Other fungi are noted in descending order; the degree of damage varied from 4.65% to 7.83% with an increase in the concentration of MeC NC Cu (the least significant difference (95%) = 0.67).
[Analysis of the binding site of copper with intact and Escherichia coli bacteria modified by N-ethylmaleimide by ESR].
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.