Swelling behavior of poly(vinyl alcohol) cryogels employed as matrices for cell immobilization

Poly(vinyl alcohol) cryogels are prepared from aqueous solutions of the polymer by freezing and thawing and are employed as matrices for cell immobilization. The swelling behavior of these macroporous gel carriers in pure water and in solutions of certain compounds (salts, amino acids, and glucose) was studied to elucidate the osmotic properties of the cryogels during long-term exposure to aqueous media. It was shown that after the initial sol fraction was washed out, the residual gel matrix possessed high stability even at extreme pH conditions (acid or alkali concentration up to 1.0 mol l⁻¹) or in the presence of strong chaotropic salts such as sodium rhodanide. Although the macroporous supermolecular structure of the carriers under consideration underwent certain changes as a result of aging processes during prolonged washing of the gel, the high porous morphology of the material was retained.     

Purification of sialic acid binding protein from saprophytic bacteria by hydrophobic-interaction chromatography on butyl-toyopearl and polymer-coated porous glass

Summary Two rigid sorbents with identical nominal hydrophobic functions (Butyl-Toyopearl and poly(N-butylacrylamide)-coated porous glass (Butyl-WPG)) were compared upon chromatographic purification of lectin from Bacillus subtilis. Hydrophobic-interaction chromatography on the Butyl-WPG promotes the better resolution of nonactive contaminants from the active lectin. There were found optimal conditions for HPLC-analysis of purified lectin preparations. One step of chromatography on the butyl-WPG provided a considerable purification of lectin (98% of contaminants were removed), which retained 62,5% of its initial hemagglutinating activity.     

Changes in the currents across sodium channels as affected by blood serum on cultured neuroblastoma cells

Adding of 5% bovine serum to internally perfused voltage-clamped serum deprived neuroblastoma cells rapidly stimulates transient sodium current. This stimulating effect is mainly due to the increase in the peak sodium conductance by almost 24 per cent, on the average. Besides that a modifying effect was observed resulting in the 6 mV shift of the sodium peak conductance curve towards more negative potentials and in the 5 mV shift of steady inactivation curve towards more positive ones. The sign of the latter shift was changed to the opposite under the action of serum thermally pretreated at 100 degrees C. This procedure led also to more than two fold lowering of the stimulating effect. Experiments with serum deprivation demonstrate different degrees of reversibility of the serum effects, the most reversible being the inactivation curve shift. EGF, insulin, dexamethasone, transferrin, ATP, serotonin and their combinations in physiological concentrations failed to give the typical whole serum effects. The serum is supposed to contain at least two active components of unknown nature, one of which being thermoresistant.     

Binding and activation of the first component of human complement on artificial matrices

Artificial sorbents that comprise macroporous glass covered by the copolymer of N-vinylpyrrolidone and N-substituted acrylamide have been synthesized. Aminoethanol is bound to acrylic acid residue in one sorbent (AE-glass), whereas the other sorbent involves immunoglobulin G with the hexamethylenediamine spacer (IgG-glass). C1q binds specifically to IgG-glass with Ka 4,07(+/- 0,32) X 10(7) M-1. Free energy of the C1q binding to IgG-glass is twice higher than that of its binding to monomeric IgG. This evidences that one C1q molecule associates with two IgG molecules of the sorbent. A weak nonspecific sorption of C1q to AE-glass was found. Both specific (on IgG-glass) and nonspecific (on AE-glass) sorption of the first component of complement activate the classical pathway in human serum as manifested in the consumption of the C4, C2, C3 and C5 components. IgG-glass was employed for C1q isolation from human serum by affinity chromatography, whereas unbound part of serum may be used as a reagent R1q. The yield of highly purified C1q after IgG-glass affinity chromatography and gel filtration on Sephacryl S-300 is 63,6%.     

Preparing Modified Hyaluronic Acid with Tunable Content of Vinyl Groups for Use in Fabrication of Scaffolds by Photoinduced Crosslinking

Russian Journal of Bioorganic Chemistry - Materials based on hyaluronic acid (HA) are extensively used in tissue engineering as scaffolds. Photoinduced crosslinking is one way to prepare them, and,...     

Properties of the sodium channels of the membrane of neuroblastoma clone N18 A-1 cultured cells

Ionic currents through sodium channels of dialyzed mouse neuroblastoma N18 A-1 cells were measured under voltage clamp conditions. The PNa/PK ratio evaluated by reversal potential shifts was 10.4 +/- 0.7. Parameters of steady-state fast inactivation curves (h--V) and peak sodium conductance curves (gNa--V) were determined. The inactivation kinetics had usually a two-exponential time course. The internal perfusion of cells by trypsin and pronase caused a slowing-down of the sodium current falling phase, pronase being more specific in this respect. An external application of the purified scorpion toxin in concentration of 1.42 X 10(-7) M leads to a fast and sharp slowing-down of sodium inactivation. The same toxin in concentration of 5 X 10(-6) M, applied internally was quite unaffective. Experimental results demonstrate similarities in the main features between the sodium channels of neuroblastoma cells and those of other excitable cell membranes.     

Acetylcholinesterase expression and changes in the electrical excitability of neuroblastoma cells during their morphological differentiation induced by an increase in the pH of the medium

Inhibition of cell division and outgrowth of neurites with average rate of 31.5 +/- 4.4 micrometers per hour were observed in neuroblastoma cultures of the Neuro 2a clonal line 24 hours after the increase in the culture medium pH from 7.4 to 8.2. The total neurite length per one cell was about 298 +/- 36 micron in average by the 9-10th days of treatment. Simultaneously, a gradual enhancement of acetylcholinesterase cytochemical appearance took place attaining its maximum level by the same time. The peak sodium conductance, taken as a measure of sodium tetrodotoxin-sensitive potential-dependent channel density, was the same both in nondifferentiated cells grown in suspension or monolayer cultures, and in morphologically differentiated ones. The data lead to a conclusion that biochemical (acetylcholinesterase probe) and electrophysiological (sodium channel density) signs can express independently of morphological differentiation.     

A New Approach to the Synthesis of Trinucleotide Phosphoramidites - Synthons for the Generation of Oligonucleotide/Peptide Libraries

Abstract

Trinucleotide phosphoramidites that correspond to the codons of all 20 amino acids were synthesized in high yield in 5g scale. Precursors of those amidites - trinucleotide phosphotriesters - have been prepared using the phosphotriester approach without protection of the 3′-hydroxyl function. More than 10 oligonucleotides up to 90 bases long have been synthesized by a phosphite-triester approach using new synthons. The 67-mer (12 random codons) has been used to generate a display library of 2 × 10⁸ complexity.     

Synthesis of polymerizable phospholipid derivatives and creation of polymer monolayers and liposomes with immobilized bacteriorhodopsin

Polymerizable phospholipid derivatives with N-acryloyl groups have been synthesised; monomeric and polymeric monolayers and liposomes based on these compounds have been prepared and investigated. Bacteriorhodopsin immobilized in the monomeric and polymeric liposomes was shown to retain its native activity.