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V Brabec

Publications and source records attributed to V Brabec.

At least 127 records · Page 7Linked to original sources
PubMed1983

Electrochemical approach to the mechanism of urea denaturation of horse heart cytochrome c.

The effect of urea denaturation on the electroactivity of horse heart cytochrome c has been studied by differential pulse polarography and cyclic voltammetry at a gold electrode; the gold electrode was activated by 4,4'-bipyridine. Essentially, two redox couples with E'01 approximately equal to 0.25 V and E'02 approximately equal to -0.05 V (vs. normal hydrogen electrode) have been detected. The experimental results have been interpreted on the basis of the existence of equilibria between native and denatured electroactive forms; transitory species have been assumed to appear on reduction. The scheme that we have proposed agrees well with the conclusions obtained previously by other authors on conformational changes. Moreover, the advantage of electrochemical techniques in investigating the denaturation process has been underlined.

Animals↗
PubMed1983

Unchanged binding of 99molybdenum to red cell membrane proteins in hereditary spherocytosis.

The interaction of 99Mo with red cell membrane proteins was found specific for spectrin both in normal red cells and those of hereditary spherocytosis. In addition, no significant quantitative differences were observed in labeling patterns between these two types of red cells, thus indicating no major alterations in the spectrin molecules of hereditary spherocytosis.

Blood Proteins↗
PubMed1983

Experimental elimination of the splenic function by ethyl and methyl palmitate and significance of these substances from an immunological point of view.

Our experiments with rats dealt with finding a possible functional splenic elimination by using an i.v. injection of ethyl and methyl palmitate emulsion. Simultaneously, immunological effects were determined in both substances. After applying ethyl palmitate an extensive splenic necrosis could be induced resulting in an elimination of the sequestrational splenic function to an extent comparable to surgical splenectomy. Histological examinations of liver, lungs, kidneys, heart, bone marrow, lymph nodes and thymus together with the follow-up of some metabolic indicators in the spleen and liver (determination of proteins, DNA, RNA, EFA, transaminases in blood serum and observations of proteosynthesis) showed that the effect of ethyl palmitate on the spleen is selective and that there is no marked damage of other organs. Methyl palmitate is important for its inhibition of antibody response manifesting itself in a reduced production of heteroagglutinins and in a prolonged survival time of skin semiallografts.

Animals↗
PubMed1983

Spectrin oligomers of the red cell membrane extracts in hereditary spherocytosis.

Spectrin oligomers were extracted from the erythrocyte membrane at 37 degrees C with the low ionic strength buffer. The spectrin extractability of HS membranes was enhanced compared with controls in some cases. The major spectrin component in the extract was dimer which was, apart from a tetramer, purified by gel filtration on the Sepharose 4B column. No changes of dimer-tetramer interconversion in the extract from HS membranes were observed. Similarly, the protein composition of the membrane extracts from two types of red cells remained unchanged.

Erythrocyte Membrane↗
PubMed1983

Electrochemistry of double-stranded complexes of synthetic polyribonucleotides having interferonogenic and antiviral activity.

Double-stranded (ds) complexes of poly(C) with poly(G) and poly(G,I) were studied using differential pulse polarography (DPP) and differential pulse voltammetry at a pyrolytic graphite electrode (DPV). The complex formed by copolymer was found to be DPP inactive. On the other hand, poly(G).poly(C) yielded a small DPP peak corresponding to single-stranded (ss) poly(C). It was suggested that ss poly(C) present in the solutions of poly(G).poly(C) appeared due to the existence of segments in poly(G) during the complex-forming process in which guanine residues were unable to be hydrogen-bonded with bases in poly(C). Polynucleotide complexes investigated in this report yielded a DPV peak corresponding to electrooxidation of guanine residues, which was markedly lower than that yielded by ss polymers. Moreover, this DPV peak yielded by the complex prepared from an equimolar mixture of poly(G) and poly(C) was still markedly higher than that yielded by poly(G,I).poly(C), or by poly(G).poly(C) prepared in the excess of poly(C). The lowering of the DPV peak was explained as being particularly due to the presence of the polynucleotide segments with an intact and regular secondary structure. The results of our electrochemical analysis of the complexes investigated were compared with their biological activity reported earlier. This comparison calls attention to the fact that biological effectiveness of these biopolymers may be dependent on details of their secondary structure which may be monitored using the methods of electrochemical analysis.

Antiviral Agents↗
PubMed1982

Electrochemical reactions of horse heart cytochrome c at graphite electrodes.

The interaction of cytochrome c with a paraffin-wax-impregnated spectroscopic graphite electrode (WISGE) was studied in a medium consisting of 0.1 M potassium phosphate, pH 7.0, by means of differential pulse and cyclic voltammetry. Ferricytochrome c yields on voltammograms a single cathodic peak C around a potential of -0.3 V (vs. Ag/AgCl) and two anodic peaks AI and AII around the potentials of 0.66 and 0.89 V, respectively. Cathodic peak C corresponds to a catalytic reaction during which ferricytochrome c is reduced to ferrocytochrome c: ferricytochrome c is then regenerated by chemical oxidation of ferrocytochrome c by oxygen adsorbed at the WISGE surface. The first, more negative anodic peak AI corresponds to anodic electrochemical oxidation of tyrosine residues, whereas the second, more positive anodic peak (peak AII) corresponds to an anodic reaction of haemin. Voltammetry at a WISGE may provide a valuable technique for obtaining data about cytochrome c properties on electrically charged surface.

Animals↗
PubMed1982

The sequestration capacity of "hypersplenic" rat spleens for heat-damaged erythrocytes.

The sequestration capacity of the spleens of controls and hypersplenic rats was examined. Hypersplenism was induced by long-term intraperitoneal application of methyl cellulose. The animals were injected single doses of various amounts of heat-damaged 51Cr-labelled erythrocytes (0.1 ml to 1.5 ml); radioactivity in spleen was determined 4 hrs. following application. The amount of red cells sequestrated in the spleens of hypersplenic animals was significantly increased against the controls, after administration of massive volumes of cells. The maximum amount of erythrocytes sequestrated in the spleens of the control rats amounted to an average weight of spleens 1.25 g to 0.158 ml (0.126 ml per g of spleen), and in hypersplenic animals to an average weight of the spleen of 4.87 g to 0.283 ml (0.058 ml/l g of spleen weight).

Animals↗
PubMed1981

Relation between differential pulse voltammetric oxidation of polyriboinosinic acid and its structure.

Electrooxidation of poly (I) at a paraffin wax-impregnated spectroscopic graphite electrode was studied by means of differential pulse voltammetry. It was found that the transition of single-stranded poly (I) to its multistranded form, induced by increasing the ionic strength of neutral medium, is accompanied by a lowering of the oxidation current of poly (I). The marked lowering of the oxidation current is also observable as a consequence of the formation of double-stranded complex of poly (I). poly (C). The voltammetry at carbon electrodes provides for the study of poly(I) structure in principle identical information as optical methods.

Journal Article↗
PubMed1980

Electrochemical behaviour of proteins at graphite electrodes. I. Electrooxidation of proteins as a new probe of protein structure and reactions.

Electrochemical oxidation of proteins at a paraffin-wax-impregnated spectroscopic graphite electrode was studied by means of linear sweep and differential pulse voltametric techniques. It was found that proteins at the graphite electrode yield an oxidation current in the vicinity of potentials of 0.7-0.8 V in the range of neutral pH values. This current has the characteristics of adsorption currents. It was shown that irreversible electrooxidation of tyrosine or tryptophan residues is responsible for the occurrence of these protein currents. This previously undescribed electrochemical activity of proteins was exploited for the demonstration of the influence of urea on the accessibility of both tyrosine and tryptophan residues in protein molecules for interaction with their environment. It was also demonstrated that voltammetry at graphite electrodes permits an electrochemical analysis of proteins that do not contain cystine or cysteine residues.

Animals↗