Membrane transmembrane potential

The electrochemical interface between biomolecules cellular membranes, transmembrane potentials, bilayer lipid membranes, electroporation... 

If the intensity and duration of the applied electric pulse are controlled properly, the created nanopores will be reversible and the cell will remain alive during and after the electroporation. The created nanopores on the cell membrane may be treated as a pathway to insert different biological nanoparticles such as qdots and DNA into the cells. Because of the difference of the electric potential on two sides of the cell membrane (transmembrane potential), the electrokinetics plays a decisive role on transporting... 

Conductivity. Conductivity is an electrical property of excitable tissue which ensures that if one area of a membrane is excited to full activity, that area excites adjacent areas. Conduction of an impulse varies direcdy with the rate of development of phase 0 and the ampHtude of the action potential. Phase 0 is faster, and ampHtude of the action potential is greater, the more negative the transmembrane potential at the time of initiation of the impulse. Conduction velocity is faster when phase 0 is fast. 

The transmembrane potential derived from a concentration gradient is calculable by means of the Nemst equation. If K+ were the only permeable ion then the membrane potential would be given by Eq. 1. With an ion activity (concentration) gradient for K+ of 10 1 from one side to the other of the membrane at 20 °C, the membrane potential that develops on addition of Valinomycin approaches a limiting value of 58 mV87). This is what is calculated from Eq. 1 and indicates that cation over anion selectivity is essentially total. As the conformation of Valinomycin in nonpolar solvents in the absence of cation is similar to that of the cation complex 105), it is quite understandable that anions have no location for interaction. One could with the Valinomycin structure construct a conformation in which a polar core were formed with six peptide N—H moieties directed inward in place of the C—O moieties but... 

Fig. 5. Tentative mixed potential model for the sodium-potassium pump in biological membranes the vertical lines symbolyze the surface of the ATP-ase and at the same time the ordinate of the virtual current-voltage curves on either side resulting in different Evans-diagrams. The scale of the absolute potential difference between the ATP-ase and the solution phase is indicated in the upper left comer of the figure. On each side of the enzyme a mixed potential (= circle) between Na+, K+ and also other ions (i.e. Ca2+ ) is established, resulting in a transmembrane potential of around — 60 mV. This number is not essential it is also possible that this value is established by a passive diffusion of mainly K+-ions out of the cell at a different location. This would mean that the electric field across the cell-membranes is not uniformly distributed.

Mansueto et al. suggested that the susceptibility of embryos to toxicants could be first related to their interaction with egg membrane where they could provoke changes of permeability, of transmembrane potential, and of receptors distribution which could in turn drastically interfere with normal cell physiology. Cima et al. observed that TBT alters, immediately after the entry of... 

When the original compositions of the outer phases are different, the permselective membrane will prevent the complete leveling of these compositions. Some equilibrium component distribution between phases (a) and (p) will be established, and between points A and B a potential difference called the membrane potential (or transmembrane potential) (p will develop. This potential difference is determined by... 

The involvement of mitochondria in the pro-apoptotic effects of carotenoids has been clearly demonstrated by the fact that P-carotene induces the release of cytochrome c from mitochondria and alters the mitochondrial membrane potential (Aym) in different tumor cells (Palozza et al., 2003a). Moreover, the highly polar xanthophyll neoxanthin has been reported to induce apoptosis in colon cancer cells by a mechanism that involves its accumulation into the mitochondria and a consequent loss of mitochondrial transmembrane potential and releas of cytochrome c and apoptosis-inducing factor (Terasaki et al., 2007). 

Fig. 6 The electrical potential, ij/, profile across a lipid bilayer. The transmembrane potential, Aij/, is due to the difference in anion and cation concentrations between the two bulk aqueous phases. The surface potential, ij/s, arises from charged residues at the membrane-solution interface. The dipole potential, J/d, results from the alignment of dipolar residues of the lipids and associated water molecules within the membrane...

Slow dyes that respond via a redistribution across the entire membrane (sometimes called Nemstain dyes) do so because of a change in the transmembrane electrical potential. As such, they can only be used as probes of the transmembrane potential and not as probes of the surface potential or the dipole potential. Dyes whose electric field sensing mechanism involves a movement between the aqueous medium and its adjacent membrane interface on one side of the membrane can, in principle, respond to changes in both the transmembrane electrical potential and the surface potential. Fast dyes that remain totally in the membrane phase (e.g., styrylpyridinium, annellated hemicyanine, and 3-hydroxyflavone dyes) respond to their local electric field strength, whatever its origin. Therefore, these dyes can, in principle, be used as probes of the transmembrane electrical potential, the surface potential, or the dipole potential. 

Finally, separation of charge across the membrane gives rise to a transmembrane potential. The transmembrane potential is defined as the electric potential... 

In addition to the differences in phospholipid content between microbial and host cell membranes, it has been demonstrated that disparity exists between the transmembrane potentials of both organisms. The transmembrane potential is defined by the proton flux between the inner and outer bilayers of the cytoplasmic membrane and ranges from —90 to —110 mV in normal mammalian cells in contrast to transmembrane potentials of —130 to —150mV for logarithmic phase microbes. The differences in these electrochemical gradients have been postulated to drive the influx of peptides into the cell and thus act as a crucial barrier for defining host defense peptide selectivity. ... 

The transient change in the transmembrane potential upon excitation. An action potential cycle consists of a transient depolarization of the cell membrane of an excitable cell (such as a neuron) as a result of increased permeability of ions across the membrane, followed by repolarization, hyperpolarization, and finally a return to the resting potential. This cycle typically lasts 1-2 milliseconds and travels along the axon from the cell body (or, axon hillock) to the axonal terminus at a rate of 1-100 meters per second. See Membrane Potential... 

The voltage difference, sometimes referred to as the transmembrane potential or the membrane electric potential, that is due to the difference of concentrations of ions on either side of the membrane. Typically, such potentials are measured in millivolts (mV) and usually have values between —30 and —70 mV. In most cells, the interior of a cell is negative with respect to the exterior. 

Aizawa et al. developed immunosensors of the first type for syphilis and blood typing [228-230] based on measurements of the transmembrane potential across an immunoresponsive membrane. The potentiometric immunosensor using an antibody against human chorionic gonadotropin (hCG)... 

---