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Biomedical subjects

E Palecek

Publications and source records attributed to E Palecek.

6 recordsLinked to original sources
PubMed1979

Changes in the circular dichroic spectrum of calf thymus solubilized chromatin caused by ultraviolet irradiation.

UV irradiation of the chromatin caused an increase of the positive circular dichroic band in the vicinity of 275 nm (corresponding to DNA) and a deepening of the negative band of proteins at about 225 nm. These changes in the circular dichroic spectrum are monotonous in the range of doses studied (less than 6 X 10(4) J.m-2). The increase of the positive circular dichroic band probably reflects the occurrence of local conformational changes in DNA, which include changes in base position (tilting, distance from helix axis) in the close neighborhood of photoproducts. The presence of photoproducts in chromatin reduces changes in its circular dichroic spectra with temperature.

Animals↗
PubMed1978

Changes in properties of DNA caused by gamma and ultraviolet radiation. Dependence of conformational changes on the chemical nature of the damage.

Changes in the pulse-polarographic behaviour and circular dichroism spectra of DNA were investigated after gamma and ultraviolet irradiations and after degradation by DNAse I. It was found that moderate doses of radiation cause local conformational changes in the double helix, which are dependent on the chemical nature of the damage. Only the accumulation of structural changes after high doses of the radiations or after extensive enzymic treatment may cause formation of single-stranded regions in DNA.

Animals↗
PubMed1976

Interaction of nucleic acids with electrically charged surfaces. II. Conformational changes in double-helical polynucleotides.

The influence of adsorption of double-stranded (ds) DNA, ds RNA and homopolymeric pairs at a mercury electrode on conformation of these polynucleotides was studied. Changes in the polarographic reducibility of polynucleotides, which were followed by means of normal pulse polarography and linear sweep peak voltammetry at the dropping mercury electrode were exploited to indicate conformational changes. It was found that, as a consequence of adsorption of ds polynuclotides on the negatively charged electrode conformational changes similar to denaturation take place in a narrow potential region around -1.2 V (the region U). After sufficiently long time of the contact with the electrode (under our conditions about 10 s) these changes reach limiting values, which can approach total denaturation. Upon adsorption of ds polynucleotides on the electrode charged to more positive potentials than the region U either (1) no conformational changes occur or (2) only a small part of the polynucleotide (probably labile regions of the ds molecule) is very quickly denatured - the remainder of the molecule preserves its ds structure. Conformational changes of adsorbed ds polynucleotides are influenced by factors which change the stability of ds polynucleotides in solution. It is supposed that denaturation of ds polynucleotides in the region U might result from the strains connected with the repulsion of certain segments of the molecule anchored on the electrode from the negatively charged surface.

Animals↗
PubMed1975

Studies on electron transfer between mercury electrode and hemoprotein.

The electrochemical behaviour of ferricytochrome c, metmyoglobin and methemoglobin was studied using d.c., a.c. and differential pulse polarography, and controlled potential electrolysis. 1. The three hemoproteins yield d.c. polarographic steps, and peaks in differential pulse polarograms, the height of which is proportional to concentration. The charge transfer is influenced by strong adsorption. 2. The concentration dependence of the a.c. polarograms indicates structural changes in the adsorbed molecules. 3. The reduction products of controlled potential electrolysis of metmyoglobin and methemoglobin have absorption spectra identical with the native control samples. The affinity for oxygen and the cooperativity in hemoglobin are not affected by the reaction at the electrode. 4. The charge transfer proceeds via adsorbed, already reduced, molecules to freely diffusible proteins.

Binding Sites↗