Bioelectrochemistry and bioenergetics (Lausanne, Switzerland)最新文献

In this work, the long-range interaction between the pairs of nucleotides situated on the opposite ends of a double broken DNA helix have been studied theoretically. The long-range energy was considered as a sum of electrodynamics Van der Waals and electrostatic Coulomb interactions. The most important region for the problem under consideration is about 5–15 Å between the nucleotides. The calculations of the energy of long-range interaction have shown that during the interaction between the pairs CG–CG, there is a potential repulsive barrier with the amplitude of about 4 kT at the distance of 7–9 Å, and during the interaction between the pairs TA–TA, there is a potential repulsive barrier with the amplitude of about 1.5 kT at the same distance, which can prevent DNA from enzyme selfrepairing after a double DNA break. This barrier vanishes as the pH of intracellular medium increases. The remainder pairs of nucleotides do not have such barrier, and there is always an attraction like interaction.

In this paper we investigate the nonlinear dynamics of a DNA chain in the presence of endogenous AC fields (EACF) generated by the living cell itself. The dynamics of the DNA chain is described in the framework of the nonlinear breather mode. The transition of breather localized modes into open states, affected by AC fields is calculated by using Kubo's formalism for the linear response of the system.

Mechanism of organization and order in biological systems is not satisfactorily explained yet. Biophysical theories predicted that coherent endogenous electric field of high frequency can play a significant role in organization. The polarity of vibration structures, spectral energy transfer caused by nonlinearities, and energy supply can lead to energy condensation and excitation of coherent states. These conditions are satisfied in the polymer structures of the cytoskeleton, in particular, in the microtubules as follows from experimental findings. Nonetheless, experimental verification of energy condensation and coherent vibrations in the cytoskeleton is still missing.

The Wu–Austin Hamiltonian as the basis for deriving Fröhlichs rate equations from a microscopical point of view has been investigated. In addition to an earlier paper we show in a very easy manner that this or similar Hamiltonians have no lower bound and are therefore unphysical. The perturbation expansion which is the tool to derive Fröhlichs rate equations with this Hamiltonian is not converging. Therefore, the usual derivation of this rate equation is not valid.

The use of quartz crystal microbalance (QCM) for monitoring in situ the enzymatic cleavage of surface-confined nucleic acids by nucleases is described. Such real-time monitoring of mass changes associated with the enzymatic digestion indicates that the activity and specificity of nucleases is preserved at the gold surface, and can be used for manipulating surface-confined DNAs and RNAs. These observations indicate great promise for using QCM for elucidating the interactions of nucleic acids with enzymes, and for enhancing the power of hybridization biosensors.

The changes in the electroporation process of human erythrocytes membrane due to the direct action of high energy electron radiation were investigated. To avoid the indirect effects caused by radiolytic products of water, the irradiation was performed at liquid nitrogen temperature. The irradiated cells have been exposed to square-wave electric pulses at 4°C in isotonic suspensions to induce membrane electropores. The pores resealing were quantified by monitoring the cell hemolysis. A significant decrease of the resealing process was found for irradiation doses higher than 100 Gy. The mass of molecular structures affected by the direct action of radiation was estimated using the target analysis method. We found a molecular weight M_m≈930 kDa roughly corresponding to spectrin tetramer of the cytoskeleton. This suggests that spectrin network plays an important role in the pores resealing of the electropermeabilized erythrocyte membrane.

Microelectronic sensors are used for measurements of electromagnetic fields generated by synchronized cultures of yeast cells. Cold sensitive mutant tub2-401 of Saccharomyces cerevisiae is used. The measured electromagnetic signals in the frequency range from 8 to 9 MHz are compared with evolution of the reassembled microtubules. The detected signals peak in the time interval 25–30 min and 45–60 min after the release of the cells from the restrictive to the permissive temperature. The first maximum corresponds to the stage when the mitotic spindle is formed and binds chromatids. The second maximum is measured when the processes of anaphase A and of anaphase B take place.

Hydration of the various residues of phospholipids was inferred from the shift in the wave number of their vibration bands, obtained from the amplitudes of their positive and negative peaks in the difference spectra between those of the hydrated and the dry phospholipid multibilayers. The effect of aligned phospholipid layers on the orientation of their hydrating water molecules was inferred from the dichroic ratio of the OH stretching band, measured by polarized attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) with a germanium prism, as a function of the water-to- lipid ratio in the surface film. The results indicate that about seven water molecules are oriented by one phosphatidyl serine molecule in the surface film. About 8 to 11 additional water molecules contribute to the hydration of the polar residues as revealed by the effect on the difference spectra. The hydration appears to be cooperative. A water molecule that initiates hydration of a site facilitates access of additional water molecules, until the hydration of the whole site composed of many different interacting polar residues is completed.

Frequency-dependent lactose uptake via the H⁺/lactose symporter in an externally applied low-intensity alternating electric field was demonstrated, using tracer flux experiments. The uptake of radiolabeled lactose was significantly inhibited with the electric field-strength of 30 V/cm and at frequencies below 10 Hz.