On the thermodynamic characterization of membrane gating particles by their Boltzmann distribution

The characterizations of gating particles of ionic channels in nerve membranes by their equivalent valencies and their electric dipole moment changes are compared. The gating particle is represented as a system of electric charges in fixed positions in an external electric field and the potential energy of such a system is calculated in the approximation of a constant electric field. The proper expression of the Boltzmann distribution of the gating particles is presented. It is shown that the dipole moment of transition of the gating particle is the only proper thermodynamic (macroscopic) characteristics of the gating particles based on the available experimental information and does not depend on any microscopic assumption as the equivalent valency does.     

Influence of DNA length on spermine-induced condensation. Importance of the bending and stiffening of DNA

Using DNA restriction fragments of 258 to 4362 base-pairs, we have investigated the influence of the DNA length on the condensation process induced by spermine, with the aid of electric dichroism measurements. The 258- and 436 bp fragments condensed into rod-like particles, while the fragments of 748 bp or more condensed into torus-shaped particles. Our results suggest that a DNA molecule longer than the circumference of the toroids observed previously (680 bp) is required to serve as a nucleus for the growth of the condensed particles. The toroids were more stable in the electric field than the rod-shaped particles, suggesting that rapid fluctuations of the bound spermine counterions can provide one of the main attractive forces yielding to the condensation process. Relaxation time data for the 436 bp fragment revealed that the structure of DNA was altered at a spermine concentration as low as one-tenth of that required for condensation: the DNA became bent in the presence of spermine. Moreover, the field strength dependence of the relaxation times, as well as the fitting of the decay curves at 12.5 kV/cm, showed an increase of the stiffness of the DNA double helix upon spermine addition. We estimated that, in the case of DNA condensation by spermine, a decrease in the measured persistence length may occur, irrespective of the DNA flexibility, owing to the bending of the DNA molecule.     

Influence of DNA length on spermine-induced condensation: Importance of the bending and stiffening of DNA

Using DNA restriction fragments of 258 to 4362 base-pairs, we have investigated the influence of the DNA length on the condensation process induced by spermine, with the aid of electric dichroism measurements. The 258- and 436 bp fragments condensed into rod-like particles, while the fragments of 748 bp or more condensed into torus-shaped particles. Our results suggest that a DNA molecule longer than the circumference of the toroids observed previously (680 bp) is required to serve as a nucleus for the growth of the condensed particles. The toroids were more stable in the electric field than the rod-shaped particles, suggesting that rapid fluctuations of the bound spermine counterions can provide one of the main attractive forces yielding to the condensation process. Relaxation time data for the 436 bp fragment revealed that the structure of DNA was altered at a spermine concentration as low as one-tenth of that required for condensation: the DNA became bent in the presence of spermine. Moreover, the field strength dependence of the relaxation times, as well as the fitting of the decay curves at 12.5 kV/cm, showed an increase of the stiffness of the DNA double helix upon spermine addition. We estimated that, in the case of DNA condensation by spermine, a decrease in the measured persistence length may occur, irrespective of the DNA flexibility, owing to the bending of the DNA molecule.     

Radial electric field and rotation of the ensemble of plasma particles in tokamak

The velocity of macroscopic rotation of an ensemble of charged particles in a tokamak in the presence of an electric field has been calculated in a collisionless approximation. It is shown that the velocity of toroidal rotation does not reduce to a local velocity of electric drift and has opposite directions on the inner and outer sides of the torus. This result is supplemented by an analysis of the trajectories of motion of individual particles in the ensemble, which shows that the passing and trapped particles of the ensemble acquire in the electric field, on the average, different toroidal velocities. For the trapped particles, this velocity is equal to that of electric drift in the poloidal magnetic field, while the velocity of passing particles is significantly different. It is shown that, although the electric-field-induced shift of the boundaries between trapped and passing particles in the phase space depends on the particle mass and charge and is, in the general case, asymmetric, this does not lead to current generation.     

Electrical Sizing of Particles in Suspensions: I. Theory

The processes involved during the passage of a suspended particle through a small cylindrical orifice across which exists an electric field are considered in detail. Expressions are derived for the resulting change in current in terms of the ratios of particle to orifice volume and particle to suspending fluid resistivity, and particle shape. Graphs are presented of the electric field and of the fluid velocity as functions of position within the orifice, and of the shape factor of spheroids as a function of their axial ratio and orientation in the electric field. The effects of the electric and hydrodynamic fields on the orientation of nonspherical particles and on the deformation of nonrigid spheres is treated, and the migration of particles towards the orifice axis is discussed. Oscillograms of current pulses produced by rigid, nonconducting spheres in various orifices are shown and compared with the theoretical predictions.     

Electro-optic evidence for the control of the structure of bacteriophage f1 by a minor coat protein

The structures of the filamentous bacteriophage f1 and its gene 3 amber mutant R4 have been compared using electric birefringence, electric dichroism, and ultrasonic vibration. The electro-optic experiments showed that the phage particles can be oriented in an electric field. The birefringence and dichroism as a function of field strength are not the same for the A-protein mutant and for the wild-type particle. Studies using ultrasonic vibration to fragment the bacteriophage show that the stabilities of the f1 and R4 particles differ.     

Energy of electrons emitted as a result of separation of surfaces

Experiments indicating acceleration of charged particles as a result of separation of solid surfaces are analyzed. As a possible mechanism of such acceleration, generation of surface charge on the separated surfaces of a cleaved ionic crystal is considered. The maximum electric field generated due to the charging of the separated surfaces and the energy of electrons accelerated in such a field are estimated. It is shown that, for the maximum attainable electric field, conditions are created for the generation of runaway electrons that, even at atmospheric pressure, electrons are accelerated to high energies, not experiencing collisions with gas particles.     

The trajectories of particles suspended in electrolytes under the influence of crossed electric and magnetic fields. Possible explanation of the sensitivity of organism to magnetic fields

We observed that particles, suspended in an electrolyte and brought into crossed magnetic and electric fields of low intensities, will deviate in the central part of the electrophoresis chamber of a standard Zeiss Cytopherometer with a component vertical to both fields. The direction and magnitude, however, were sharply at variance with what would be expected by the action of the Lorentz force (EMF) on the surface of the particles. The magnitude of the deviation depends upon the magnetic and electric field strength, the ion concentration of the suspension medium and the geometry of the chamber. The movement of the particles is due to streaming of the electrolyte which is mainly caused by inhomogeneities of the electric field in the electrophoresis chamber. The magnitude of the effect is high enough to occur physiological conditions. Magneto-electrophoretic streaming might eventually act as a transducer mechanism which could explain the ability of some animals to orientate themselves in the geomagnetic field.     

Electrical Counting and Sizing of Mammalian Cells in Suspension

A recently developed method of determining the number and size of particles suspended in a conducting solution is to pump the suspension through a small orifice having an immersed electrode on each side to supply electrical current. The current changes due to the passage of particles of resistivity different from that of the solution. Theoretical expressions are developed which relate the current change caused by such particles to their volume and shape. It is found that most biological cells may be treated as dielectric particles whose capacitive effects are negligible. Electrolytic tank measurements on models confirm the theoretical development, and electric field plots of model orifices are used to predict the observed pulse shapes. An equivalent circuit of the orifice-electrode system is analyzed and shows that the current pulse may be made conductivity-independent when observed with a zero input impedance amplifier.     

Analysis of the differential cross sections for bremsstrahlung during collisions between two charged particles in a uniform electric field

Under the nonrelativistic Born approximation, differential cross sections are derived for elastic collisions between two point charged particles in an external constant uniform electric field and for bremsstrahlung during these collisions.An analysis of the cross sections obtained shows that, due to the interference of the wave functions of two colliding particles during their reflection from the potential barrier of an external electric field, the differential cross sections for elastic collisions and for unpolarized bremsstrahlung (i) are both oscillatory in character and (ii), instead of being linearly proportional to one another (as in the case without an externale electric field), are related in a more complicated manner.     

Propagated disturbances of transverse potential gradient in intracellular fibrils as the source of motive forces for longitudinal transport in cells

Summary It is proposed as a working hypothesis that conformational changes propagated like waves along intracellular fibrils (tubules, microtubules, microfilaments) have an electric component,i.e., there are waves of disturbance of electric potential in the fibrils. The paper considers the unavoidable consequences of the wave. The latter is accompanied by local electric field in the boundary layer of cytoplasmic fluid. Both positively and negatively charged particles may be attracted to the fibril in certain regions of the field and, being attracted, the particle may be under the action of longitudinal component of electric force. When the force is strong enough to move the particle with wave velocity, the particle will travel smoothly along the fibril, otherwise the movement will be saltatory or of agitation type. Net electroosmotic flow in one direction in the boundary layer of fluid may be expected when the waves are propagated in series. Turbulent motion of the fluid caused by the waves may provide the basis for activated diffusion. Asymmetry of the wave may account for polar transport of this sort. The electric field transmitted along the fibril across a sieve pore in phloem may facilitate electroosmotically the flow through the pore. Quantitative requirements of the hypothesis that electric field generated by the waves may account for different aspects of longitudinal transport in cells are apparently met.     

The trajectories of particles suspended in electrolytes under the influence of crossed electric and magnetic fields

We observed that particles, suspended in an electrolyte and brought into crossed magnetic and electric fields of low intensities, will deviate in the central part of the electrophoresis chamber of a standard Zeiss Cytopherometer with a component vertical to both fields. The direction and magnitude, however, were sharply at variance with what would be expected by the action of the Lorentz force (EMF) on the surface of the particles. The magnitude of the deviation depends upon the magnetic and electric field strength, the ion concentration of the suspension medium and the geometry of the chamber. The movement of the particles is due to streaming of the electrolyte which is mainly caused by inhomogeneities of the electric field in the electrophoresis chamber. The magnitude of the effect is high enough to occur under physiological conditions. Magneto-electrophoretic streaming might eventually act as a transducer mechanism which could explain the ability of some animals to orientate themselves in the geomagnetic field.     

Experimental and Simulation Studies of Electro-rheology

Abstract

Electro-rheological fluids are colloidal dispersions that, under the influence of an applied electric field, can show a spectacular increase in yield stress and viscosity. Despite many technological roles for fluids with a viscosity that can be controlled electrically, progress at making them commercially viable products has been slow, partly due to a lack of understanding of this phenomenon at the microscopic level. In this report, simulation and experimental data are combined to provide insights into the microscopic origins of this effect. The simulations produce electric field-induced “strings” of particles that span the electrodes, in agreement with the experimental observation, and are responsible for the major enhancements in the viscosity. The field also causes a strong distortion in the first coordination shell of colloidal particles. The combination of shear and electric field produces a long-range microstructure that is periodically forming and decaying, caused by the competing effects of electric field and shear rate. Comparison with experiment reveals that the Electro-rheological effect is driven by the applied field-induced Stokesian diffusion of the solid particles and relies little on the accompanying Brownian motion.     

The ac field patterns about living cells

The presence of the small ac electric fields produced by living cells is shown by the gentle dielectrophoretic force on tiny dielectric particles. The beauty of the field patterns is made evident as the cell and particles settle in a hanging drop. Patterns characteristic of repulsion and of attraction, as well as of a dipolar and quadripolar nature, are observable.     

The ac field patterns about living cells

The presence of the small ac electric fields produced by living cells is shown by the gentle dielectrophoretic force on tiny dielectric particles. The beauty of the field patterns is made evident as the cell and particles settle in a hanging drop. Patterns characteristic of repulsion and of attraction, as well as of a dipolar and quadripolar nature, are observable.     

Electric birefringence study of the purple membrane of Halobacterium halobium

An electric birefringence study was carried out on aqueous suspensions of the purple membrane of Halobacterium halobium. In addition to the characterization of both native and modified membrane samples, the dependence of electric birefringence on pH and ionic strength was also investigated. The results indicate that purple membrane shows electric birefringence at a field strength as low as 200 V/cm. The permanent dipole moment and polarizability ranged from 20,500 debyes and 1.01 × 10^?14 cm³ for a purple membrane concentration of 0.40 mg/mL to 41,000 debyes and 2.05 × 10^?14 cm³ for a concentration of 0.80 mg/mL. It was also found that removal of the retinyl group of bacteriorhodopsin substantially decreases but does not eliminate the electric birefringence of the membrane. The solubilization of the membrane by Triton X-100, however, completely abolishes the electric birefringence. These experiments indicate that there is an interaction between adjacent bacteriorhodopsin molecules within the purple membrane via the retinyl chromophore moiety that builds up the permanent dipole moment. They also suggest that there are two types of response when purple membrane suspensions are placed in an electric field. One is an alignment of the disk-shaped particles with the field. The other is a stacking of the particles following their alignment by the electric field, which is promoted by the induced dipole moment.     

Forces on Biological Particles in Electric Fields

The forces exerted by electric fields on particles suspended in biological fluids are examined. Both charged particles and polarlzable bodies are treated and expressions for the current flow under the influence of an electric field are obtained.     

High Permittivity CaCu3Ti4O12 Particle‐Induced Internal Polarization Amplification for High Performance Triboelectric Nanogenerators

Here, a composite material based on the butylated melamine formaldehyde (BMF) and high permittivity CaCu₃Ti₄O₁₂ (CCTO) particles as a triboelectric dielectric material for stable high output triboelectric nanogenerators (TENGs) is proposed. CCTO particles, which have the high permittivity of 7500, can potentially result in the formation of strong internal polarization into the dielectric material under the electric field from triboelectric charges. As a consequence, the charge induction on the bottom electrode is enhanced thereby increasing the triboelectric output performance. A rotation‐type freestanding mode TENG based on BMF–CCTO 1 wt% composite material demonstrates high performance power output of a root‐mean‐square voltage and current density with 268 V and 25.8 mA m^?2, respectively. The strategy of incorporating the high permittivity CCTO particles can be universally applied to any triboelectric polymer matrix in order to enhance the output performance of TENGs.     

Electric field generated by axial longitudinal vibration modes of microtubule

Microtubules are electrically polar structures fulfilling prerequisites for generation of oscillatory electric field in the kHz to GHz region. Energy supply for excitation of elasto-electrical vibrations in microtubules may be provided from GTP-hydrolysis; motor protein–microtubule interactions; and energy efflux from mitochondria. We calculated electric field generated by axial longitudinal vibration modes of microtubules for random, and coherent excitation. In case of coherent excitation of vibrations, the electric field intensity is highest at the end of microtubule. The dielectrophoretic force exerted by electric field on the surrounding molecules will influence the kinetics of microtubule polymerization via change in the probability of the transport of charge and mass particles. The electric field generated by vibrations of electrically polar cellular structures is expected to play an important role in biological self-organization.     

Seasonal changes in the human constant electrical field in various age groups]

Seasonal changes of the constant electric field of healthy people of various age groups were studied. The constant electric field was shown to be characterized by a fine structure of distribution of electric potential differences (EPD) along the skin in relation to a referent point located on the neck in the intersection region of trapeziform and clavicular-nipple muscles. The constant electric field of the people of all ages undergoes seasonal changes involving displacement of all EPD values to the positive region during autumn-winter period as compared to the spring-summer one. It is suggested that such EPD change is conditioned by a change of the organism metabolic activity. The discovered differences in EPD displacement values of various age groups can serve as physiological characteristics of transitional processes in the growing organisms.