Generation Of Electric Potential Difference Research Articles

Generation of electric potential difference by chromatophores from photosynthetic bacteria in the presence of trehalose under continuous illumination

Measurement of the electrical potential difference (Δψ) in membrane vesicles (chromatophores) from the purple bacterium Rhodobacter sphaeroides, associated with the surface of a nitrocellulose membrane filter (MF), impregnated with phospholipid solution in decane, as well as immersed inside it, in the presence of exogenous mediators and disaccharide trehalose, demonstrated an increase in the amplitude and stabilization of the signal under continuous illumination. The ascorbate/N,N,N′N′-tetramethyl-p-phenylenediamine pair and ubiquinone-0 were used as mediators (electron donor and acceptor), respectively. Although the stabilization of photoelectric responses under long-term continuous illumination was observed in both cases of immobilization of chromatophores, only when the samples were immersed inside the MF, the functional activity of the reaction centers was maintained for a month when they were stored in the dark at room temperature. Stable photoresponses are probably associated with the preservation of the integrity of chromatophore proteins inside MF pores. The stabilizing effect of the bioprotector trehalose may be due to both its effect on RC proteins and on the phospholipid bilayer membrane. The results obtained will expand modern ideas about the use of semi-synthetic structures based on various intact photosynthetic systems capable of converting solar energy into an electrochemical form.

Generation of Electric Potential Difference by Chromatophores from Photosynthetic Bacteria in the Presence of Trehalose under Continuous Illumination.

Measurement of electrical potential difference (Δψ) in membrane vesicles (chromatophores) from the purple bacterium Rhodobacter sphaeroides associated with the surface of a nitrocellulose membrane filter (MF) impregnated with a phospholipid solution in decane or immersed into it in the presence of exogenous mediators and disaccharide trehalose demonstrated an increase in the amplitude and stabilization of the signal under continuous illumination. The mediators were the ascorbate/N,N,N'N'-tetramethyl-p-phenylenediamine pair and ubiquinone-0 (electron donor and acceptor, respectively). Although stabilization of photoelectric responses upon long-term continuous illumination was observed for both variants of chromatophore immobilization, only the samples immersed into the MF retained the functional activity of reaction centers (RCs) for a month when stored in the dark at room temperature, which might be due to the preservation of integrity of chromatophore proteins inside the MF pores. The stabilizing effect of the bioprotector trehalose could be related to its effect on both the RC proteins and the phospholipid bilayer membrane. The results obtained will expand current ideas on the use of semi-synthetic structures based on various intact photosynthetic systems capable of converting solar energy into its electrochemical form.

Mechanism of Ion Translocation by Na+-Rhodopsin.

This review provides a brief description of the structure and transport function of the recently discovered family of retinal-containing Na+-translocating rhodopsins. The main emphasis is put on the kinetics of generation of electric potential difference in the membrane during a single transporter turnover. According to the proposed transport mechanism of Na+-rhodopsin, the driving force for the Na+ translocation from the cytoplasm is the local electric field created by the H+ movement from the Schiff base.

The Characteristics of Debye Effect Magnetic Field Under Acoustic Excitation

Debye proposed the generation of electric potential difference under acoustic excitation in electrolyte solution because of ion separation. However, the ion separation can also induce magnetic field, which has always been neglected by researchers. This paper builds a theoretical model of Debye effect magnetic field, and a multi-physics computation method to study the magnetic field. According to the computation results, an acoustic excitation with frequency at 70Hz and amplitude at 0.1m/s can generate magnetic field at the level of one pico-Tesla, which can be detected nowadays.

Generation of electric potential difference across the electrodes of the microbial fuel cell in the anaerobic oxidation of substrates by microbial associations

Several microbial associations were obtained from natural and anthropogenic sources. All of the associations grow well on glucose and significantly worse on acetate. We observed 80–95% glucose consumption during 3–5 days of growth. The oxidation of substrates by the cultures generates an electric potential difference between anode and cathode electrodes of a microbial fuel cell (MFC). The value of the potential difference depends on the nature of the association and the substrate and reaches 400–500 mV. The potential difference generation accompanied by a shift to the negative region of the medium redox potential (Eh) to — (400–500) mV. This indicates H2 evolution by the association cultures during oxidation of carbohydrates. Artificial redox mediators, such as tetramethyl-p-phenylenediamine, phenazine methosulfate, and benzyl viologen, were able to increase up to 15% the difference in electrical potential across the electrodes of the MFC. It is assumed that an increase in the potential difference across the electrodes induced by the redox mediators is due to their direct involvement in the transfer of electrons from the bacteria in the incubation medium to the MFC anode electrode. The direct measurement of current and potential difference on the electrodes in a short-circuit mode shows that the internal resistance of the MFC is equal to 1 kΩ and the power reaches 5 μW. Undoubtedly, this testifies to the low efficiency developed by the MFE.

Functional identification of electrogenic Na +-translocating ATPase in the plasma membrane of the halotolerant microalga Dunaliella maritima

The hypothesis that the primary Na +-pump, Na +-ATPase, functions in the plasma membrane (PM) of halotolerant microalga Dunaliella maritima was tested using membrane preparations from this organism enriched with the PM vesicles. The pH profile of ATP hydrolysis catalyzed by the PM fractions exhibited a broad optimum between pH 6 and 9. Hydrolysis in the alkaline range was specifically stimulated by Na + ions. Maximal sodium dependent ATP hydrolysis was observed at pH 7.5–8.0. On the assumption that the ATP-hydrolysis at alkaline pH values is related to a Na +-ATPase activity, we investigated two ATP-dependent processes, sodium uptake by the PM vesicles and generation of electric potential difference (Δ ψ) across the vesicle membrane. PM vesicles from D. maritima were found to be able to accumulate 22Na + upon ATP addition, with an optimum at pH 7.5–8.0. The ATP-dependent Na + accumulation was stimulated by the permeant NO 3 - anion and the protonophore CCCP, and inhibited by orthovanadate. The sodium accumulation was accompanied by pronounced Δ ψ generation across the vesicle membrane. The data obtained indicate that a primary Na + pump, an electrogenic Na +-ATPase of the P-type, functions in the PM of marine microalga D. maritima.

Investigation of the direct and inverse piezoeffect in the dynamic problem of electroelasticity for an unbounded medium with a tunnel opening

An effective approach to the investigation of antiplane electroacoustic wave fields in an unbounded piezoelectric medium weakened by a tunnel opening with the given system of surface electrodes is suggested. The approach is based on the method of boundary integral equations. It is assumed that the medium excitation occurs due to the effect of the given electrodes electric potential differences (inverse piezoeffect). The solution of the boundary-value problem of electroelasticity is also considered in the case of the direct piezoeffect when as a result of diffraction on the opening of monochromatic shear waves the generation of electric potential difference takes place on electrode coverings. An approximate scheme of numerical realization of the solvable system of singular integro-differential equations of the second kind with discontinuous kernels is given. There are presented some examples.

Light-induced generation of electric potential difference in membranes of purple and green sulfur bacteria

When associated with a planar phospholipid membrane, chromatophores isolated from photosynthetic sulfur bacteria Chromatium minutissimum, Ectothiorhodospira shaposhnikovii, and Chlorobium limicola f. thiosulfatophilum were shown to generate a light-induced transmembrane electric potential difference measured by a direct method using macroelectrodes and a voltmeter. The maximal photoelectric responses were observed upon the addition of 1,4-naphthoquinone in combination with phenazine methosulfate (or TMPD) and ascorbate. The photoeffects were inhibited by CCCP and gramicidin. The data demonstrate that similar mechanisms of photoelectric generation function in membranes of the different bacteria studied.