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.
Significance of surface potential in interaction of 8-anilino-1-naphthalenesulfonate with mitochondria: fluorescence intensity and zeta-potential.
The 8-anilino-1-naphthalenesulfonate (Ans) fluorescence in nonenergized and energized mitochondria was measured at various concentrations of Ans and KCl. Under the same experimental conditions, the zeta potential was determined from measurements of the electrophoretic mobility of mitochondria. The fluorescence intensity under various conditions was represented quantitatively in terms of the Langmuir adsorption isotherm where the electrostatic interaction acting between Ans and mitochondria was properly taken into account. The values of qN (q) proportionally constant related to quantum yield of Ans: N, the maximum number of the adsorption site) and deltaG (nonelectrical part of the free-energy change due to the binding of Ans to mitochondria) were constant irrespective of difference in energy state and in ionic strength in media. It was concluded that changes in the Ans fluorescence in mitochondria are mainly attributed to changes in the surface potential of mitochondria.
Studies by Microelectrophoretic and Microscopic Techniques of the Sorption of Illite and Montmorillonite to Rhizobia
SUMMARY: Electrophoretic measurements indicated that with increasing concentrations of illite or montmorillonite the surfaces of bacteria became progressively enveloped by a layer of adsorbed clay. The amount of clay adsorbed per unit area of cell surface depended mainly on the surface ionogenic properties of the isolates of the Rhizobium species used. For any particular isolate, almost identical amounts of illite and montmorillonite were adsorbed per bacterium. Microscopic studies confirmed the presence of a clay envelope around the bacteria and provided some information on the mode of adsorption of the clays.