Bioelectrochemistry and bioenergetics (Lausanne, Switzerland)最新文献

A rectangular electric pulse was applied to Saccharomyces cerevisiae suspensions in NaCl solutions. The relationship between field strength, pulse width and conductivity of extracellular media of key—factors to determine the yield of electropermeability—was examined at the time when the same permeability occurred. The results showed that the dependence of the yield of permeability upon the width of applied pulse was mutually related with the conductivity of extracellular media. Namely at one field strength, the value of pulse width is inversely proportional to that of conductivity of media and its relationship holds true for any field strength. Further, the relationship between parameters considered bears a close resemblance to that recognized between stress amplitude and the number of cycles to failure in the fatigue fracture of materials.

The creation of surface modified human term placental amnion by electrofusing human cells onto its surface has been thought of. A multiple-pulse electrofusion protocol with 10 square pulses of 10-μs pulse length, and electric field of 0.2 kV cm⁻¹, can make erythrocyte–amnion tissue electrofusion possible. The protocol devised merge the cell-tissue-adherence steps with fusogenic pulse. The finding opens up a new avenue of cell electrofusion onto human tissue with minimal procedural complexities.

When Escherichia coli B was aerobically grown at 37°C under inhomogeneous 5.2–6.1 Tesla (T) magnetic fields in the superconducting magnet biosystem (SBS), the cell number in the stationary phase after the growth had leveled off, was about 3 times higher than that under a geomagnetic field. When the E. coli defective in the rpoS gene which encodes a sigma factor, σ^s of RNA polymerase and is specifically expressed in the stationary phase was cultivated at 37°C in SBS, such enhancement of cell survival was significantly reduced. The E. coli cells carrying rpoS–lacZ fusion gene or other rpoS dependent genes fused with lacZ were grown, significant increase in the activity of β-galactosidase was observed in the stationary phase under high magnetic field. These data suggest that enhancement of the transcription activity in stationary phase is involved in the higher survival of the cells under magnetic field.

Relaxation of the multivibron soliton in molecular chain on lattice vibrations is investigated within the simple microscopic model. It was shown that its dynamics is governed by the nonlinear Schrödinger equation containing damping term. Its appearance is the consequence of the emission and absorption of real phonons arising when soliton velocity approaches the phase speed of sound. Explicit time dependence of the soliton parameters results as a consequence of these perturbations. In particular, soliton amplitude decreases while its width increases.

Molecules of NH₃ are capable of emitting stimulated radiation (MASER). Their organic derivates could have a similar effect, as is suggested by the new results published in Electron Correlations in Molecules and Solids [P. Fulde, Electron Correlations in Molecules and Solids, Springer-Verlag, Berlin, Heidelberg, 1993].

By modelling the non-linear effects of membranous enzymes on an applied oscillating electromagnetic field using supervised multivariate analysis methods, Non-Linear Dielectric Spectroscopy (NLDS) has previously been shown to produce quantitative information that is indicative of the metabolic state of various organisms. The use of Genetic Programming (GP) for the multivariate analysis of NLDS data recorded from yeast fermentations is discussed, and GPs are compared with previous results using Partial Least Squares (PLS) and Artificial Neural Nets (NN). GP considerably outperforms these methods, both in terms of the precision of the predictions and their interpretability.

Generalization of the Marcus transfer rate is derived for the case of a dissipative long-range donor–acceptor electron transfer (ET) mediated by specific bridging electron pathways in biological systems and driven by ac-electric field. High-frequency electric field is shown to block and even to invert the transfer if a specific relation between amplitude and frequency of the ac-field is fulfilled.

Supported thiol/lipid bilayer assembly, one of the most spectacular bilayer systems in recent years, has provided a good model to study biomembranes because of its high mechanical stability. In this work, the structural and conducting property of unmodified Au supported octadecanethiol/phosphatidylcholine bilayers were investigated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The forming process of bilayer was monitored by capacitance plane plot. The normalized membrane capacitance of supported bilayer is 0.52 μF cm⁻². Kinetically controlled voltammograms determined by Butler–Volmer equation were obtained for both thiol monolayer and thiol/lipid bilayer in linear sweep voltammetry. Results of EIS experiment indicate that collapsed sites and pinhole defects exist in thiol monolayer and lipid monolayer, respectively. The difference between the values of experimental and theoretical standard electron transfer rate constant indicates that the conducting mechanism of Au supported thiol monolayer is electron tunneling at collapsed sites. The conducting mechanism of Au supported thiol/lipid bilayer is attributed as the following: the electroactive species could diffuse through pinholes in the lipid monolayer and reach collapsed sites in thiol monolayer, where electron transfer occurs via a tunneling process. The fractional coverage of the lipid monolayer measure by EIS experiments is about 0.98 or higher.

A single pulse-mediated electrofusion of freely suspending widely separated cells could reduce steps in the protocol. Prediction of such electrofusion is still unsolved. In pre-pulse condition, quantitative estimation with three-layered model cell surface reveals electrostatic repulsion (due to negative surface charge) is the major hindrance to membrane-to-membrane contact. On theoretical grounds we predict that designed single high voltage pulsing on widely separated model cell surface can counteract the non-specific repulsive interaction and favor approach of two apposed membranes. But hydrodynamic modulation of pulse exposed cell surface interaction can hamper approach of membranes contact when cells are held at a gap of more than ∼450 Å.