Cryostructured and Crosslinked Viable Cells Forming Monoliths Suitable for Bioreactor Applications

Applications of immobilized biocatalysts in both research and industry require highly active catalysts, preferably at a low cost. In this study, cryogels with high catalyst density were produced through cryostructuration of whole Escherichia coli (E.coli) cells. Prepared cryogels are macroporous materials composed of metabolically active cells crosslinked to each other via polymeric structures. Different macromolecular reagents: oxidized dextran (OxDex), polyvinyl alcohol (PVA) and polyethyleneimine (PEI), the two latter activated with glutaraldehyde (GTA) have been synthesized. Prepared polymers were tested as effective and mild crosslinkers for cells during the cryostructuration procedure. Combination of the two synthetic polymers: PEI+GTA and PVA+GTA was found most suitable for formation of macroporous and stable structures from cells without any toxic effect on them. About 90 % of β-glucosidase activity in cells was retained after crosslinking with a combination of synthetic polymers, whereas E. coli crosslinked using GTA showed complete loss of activity. Preserved viability of cells in cryogel offers possibility to induce protein expression in cells after crosslinking. For β-glucosidase induction post immobilization yielded 50 % activity of that from cells induced in free form before cryo-structurization. The results of the post immobilization studies indicate an interesting potential for handling very sensitive enzymes.     

Analysis by capillary electrophoresis of the kinetics of charge ladder formation for bovine carbonic anhydrase

A series of charge ladders of bovine carbonic anhydrase II were synthesized and the relative abundances of the rungs analyzed by capillary electrophoresis as a function of the quantity of acylating agent used. A simulation that models the kinetics of formation of the members of the charge ladders is described. The observed rate constants decreased as the extent of acylation increased. These rate constants correlated adequately with theoretical rate constants calculated using Debye-Hückel theory. The data are compatible with, but do not demand, a model for the formation of this charge ladder in which all unacetylated amino groups in each rung have indistinguishable reactivity and in which the reactivity of the amines in each rung decreases as the net charge on the protein increases; in this model, decreased reactivity is due to increased extent of protonation. This agreement between experiment and model suggests that the charge shielding that results from an ionic strength of 130 mM is not sufficient to suppress the influence of the increasingly negative charge of the protein with acetylation on the extent of protonation of Lys epsilon-NH2 groups.     

Acousto-optic interaction in alpha-BaB(2)O(4)and Li(2)B(4)O(7) crystals

Experimental studies and analysis of acousto-optic diffraction in alpha-BaB(2)O(4) and Li(2)B(4)O(7) crystals are given. Ultrasonic wave velocity, elastic compliance and stiffness coefficients, and piezo-optic and photoelastic coefficients of alpha-BaB(2)O(4) and Li(2)B(4)O(7) crystals are determined. The acousto-optic figure of merit has been estimated for different possible geometries of acousto-optic interaction. It is shown that the acousto-optic figures of merit for alpha-BaB(2)O(4) crystals reach the value M(2)=(270 +/- 70) x 10(-15) s(3)/kg for the case of interaction with the slowest ultrasonic wave. The directions of propagation and polarization of those acoustic waves are obtained on the basis of construction of acoustic slowness surfaces. The acousto-optic diffraction is experimentally studied for alpha-BaB(2)O(4) and Li(2)B(4)O(7) crystals.     

Gold nanoparticles into Ti1−xZnxO2 films: Synthesis,structure and application

The gold particles of certain size were incorporated into Ti_1−xZn_xO₂ films by sol–gel method. The synthesis conditions predetermine the size and shape of gold nanoparticles, which were monitored by the absorption spectra and SEM images. The results of Raman spectra measurements indicate that Au nanoparticles inhibit the grain growth of anatase within the film. The photocatalytic activity of Au/Ti_1−xZn_xO₂ films in the degradation of tetracycline hydrochloride depends on the sizes of Au particles.     

Photoinduced interfacial charging and "explosion" of monolayer pentacene islands

Electrostatic force microscopy shows that the electric field gradients above pentacene monolayer islands on 2-nm SiO2/Si substrates, in a dark, dry nitrogen environment, display a wide distribution of signs and magnitude that is dependent on sample history. Under 12 mW/cm2 green (532 nm) illumination, pentacene islands accumulate positive charge because of photoexcited electron transfer across the oxide to the Si substrate. At a strong illumination of 60 mW/cm2, pentacene islands reform into small spherical particles, apparently because the positive charge Coulomb repulsion energy becomes comparable to the cohesive energy of the pentacene monolayer.     

Current transfer processes in a hydrated layer localized in a two-layer porous structure of nanosized ZrO2

Journal of Materials Science: Materials in Electronics - The current transfer through a two-layer structure saturated with absorbed water, each layer of which consists of pressed ZrO2 nanoparticles...     

Anisotropy of acousto–optic figure of merit in lithium tetraborate crystals

We analyse anisotropy of acousto–optic figure of merit (AOFM) for Li₂B₄O₇ crystals in order to estimate the prospects of these crystals in acousto–optics. We find that the maximal AOFM, 3.44 × 10^?15 s³/kg, is peculiar for the isotropic acousto–optic interaction of the incident ordinary optical wave with the quasi-longitudinal acoustic wave. For the case of anisotropic diffraction in Li₂B₄O₇, the maximum 1.87 × 10^?15 s³/kg can be reached using the interaction of the extraordinary optical wave with the quasi-longitudinal acoustic wave. The case of collinear diffraction is characterized by small AOFMs, with the largest value 0.26 × 10^?15 s³/kg.     

Improved lithium-ion batteries and their communication with hydrogen power

Self-contained power supplies and energy storage continue to improve. The criteria that determine their development include efficiency, safety, adaptability, modifiability, and a number of others. In this work, one of the ways to improve the lithium-ion battery by using a new negative electrode is considered. The possibilities of applicability of the improved lithium-ion battery are discussed, its advantages and disadvantages in relation to a hydrogen fuel cell and power sources using hydrogen fuel are considered. The study of the functioning of the new anode, the material of which is a two-layer silicene on a nickel substrate, is carried out at the atomic level. Improvement of the anode characteristics can be achieved by subjecting it to the neutron doping. Li-ion batteries with an improved anode will have higher charging capacity and power, faster charging and improved safety.