PubMed Health⌕ Search

Biomedical subjects

A F Protas

Publications and source records attributed to A F Protas.

27 records · Page 2Linked to original sources
PubMedDate not supplied

[Stages of assembly and structural forms of histone oligomers-- (H2A-H2B) dimer, (H3-H4)2 tetramer and (H3-H4-H2A-H2B)2 octamer].

The process of dimer (H2A-H2B), tetramer (H3-H4)2 and octamer (H3-H4-H2A-H2B)2 formation was analyzed by the methods of gel-filtration and differential spectrophotometry. Histone octamer with the parameters most close to the native ones is established to be reconstructed only from denaturated monomers at neutral pH. The necessary condition for formation of histone octamer is the stage of tetramer (H3-H4)2 and (H2A-H2B) formation. Histone H3 with intramolecular disulphide bond (formula: see text) does not form tetramer (H3-H4)2 and is not a part of octamer. When passing through the dimer (H3-H4) stage it produces nonspecific high-molecular aggregates. Structural changes preceding the formation of histone octamer may play a significant role for transition of chromatin and nucleosomes into the transcription-active, repressed and other states.

Animals↗
PubMedDate not supplied

[Spatial organization of the histone dimer H2A-H2B in solutions of different ionic strengths].

The spatial organization of histone dimer H2A-H2B in a solution of 0.1-1.0 M NaCl is characterized by the inclusion of 38% of radicals in the composition of alpha-helical segments, fluorescence quantum yield of 0.085 +/- 0.003, long-wave shift of absorbtion (lambda max = = 278.4 +/- 0.5 nm) and fluorescence spectra (lambda max = 304.4 +/- 0.3 nm) as compared to respective spectra of free tyrosine. The changing of position lambda max of tyrosine fluorescence of histones during denaturation has been shown. The degree of alpha-helicity of histone dimer H2A-H2B, fluorescence quantum yield and the number of tyrosyls perturbed by ethylene glycol do not change within the range of 0.1-1.0 M NaCl pH 7.6. At the same time dimer denaturation takes place at greater urea concentrations as the ionic strength of the medium increases. The quenching of tyrosine fluorescence of histone dimer H2A-H2B was performed using ions I-, Cs+ and acrylamide. It has been shown that, at a concentration of NaCl 0.5 M, dimer compactization takes place, as well as the screening of some part of tyrosyls for the quenching effect of Cs+. Our experiments made it possible to identify three zones in the composition of histone dimer H2A-H2B and determine the number (ni) and fluorescence quantum yields (qi) of tyrosyls included in the following specific zones:zone I--n1 = 2, q1 = 0.136, zone II--n2 = 3, q2 = 0.08, zone III--n3 = 3, q3 = 0.055.

Animals↗
PubMedDate not supplied

[Isolation and physico-chemical properties of native histone complexes: dimer (H2-H2B), tetramer (H3-H4)2 and octamer (H3-H4-H2A-H2B)2].

The paper is concerned with the isolation of the native histone complexes: dimer (H2A-H2B), tetramer (H3-H4)2 and octamer (H3-H4-H2A-H2B)2 from the calf thymus chromatin under soft conditions (hydroxyl apatite) fractionation with the subsequent gel filtration). Parameters of hydroxyl apatite saturation with chromatin are determined. The complexes obtained are free of DNA and nonhistone proteins. Absorption spectra parameters, quantum efficiencies and fluorescence spectra typical of the corresponding histone oligomers are established. Comparison of free tyrosine fluorescence spectra with histone tyrosyl ones revealed a long-wave shift in the latter.

Animals↗
PubMedDate not supplied

[Heterogeneity of the structure of histone (H2A-H2B) dimers].

It has been found that at pH 7.4 and 100 mM NaCl only about one third of histones (H2A-H2B) dimers are able to bind the fluorescent probe I-anilinonaphthalene-8-sulphonate. The binding constant equals 2 divided by 2.7 X 10(4) M-1. The heterogenic pattern of these dimers may be genetically important and along with other factors it can determine the structural changes of the protein core of the nucleosome and of the nucleosome proper.

Anilino Naphthalenesulfonates↗
PubMedDate not supplied

[Anomalous mobility of histone dimer H3 in gel-filtration on Acrylex P-60].

Under gel-filtration on acrylex P-60 the total histone of the calf thymus is divided into 5 fractions - [H1], [H2A], [H2A, H3+(H3)2, H2B], [H2B] and [H4]. It is established that the yield volume of histone H3 dimer formed due to the intermolecular disulphide bond is the same as that of the monomeric form. It may be explained by a compact structure of the histone H3 dimer.

Animals↗
PubMedDate not supplied

[Superoxide dismutase in the nuclei of cerebral cortex cells of rats: isolation, properties, effect of ionizing radiation].

Superoxide dismutase (SOD) from rat brain cell nuclei has been distinguished. After chromatography on hydroxylapatite Sephacryl S200 and Mono S SOD can be purified 1200 times. It is Mn-depending enzyme, which has molecular weight 10 kDa and firmly associated with transcriptionally active chromatin. SOD is most active at high ion strength (1.2-2 M NaCl). The more sensitive method for SOD activity determination is suggested (modification of adrenaline autoxidation at pH 10.2).

Animals↗
PubMedDate not supplied

[Effect of low doses of irradiation on synthesis of DNA, RNA and proteins in cerebral cortex cells].

Short-term external gamma-irradiation (0.1-5 Gy) and long-term (30 days) internal irradiation of rats by everyday intake of 137Cs and 85Sr isotopes into their organisms induced, most probably, irreversible changes in the level of synthetic processes in the rat brain cortex neurons. Synthesis of RNA and proteins decreased significantly after 2h-long irradiation. Irradiation which lasted for 30 days has somewhat shortened the level of reparative DNA synthesis and has almost twice increased RNA synthesis. It was accompanied by changes in the relative activity of RNA-polymerases A, B and C. Doses over 1 Gy have induced an exponential delay of dose-dependent changes in the level of synthetic processes.

Animals↗
PubMedDate not supplied

[The characteristics of DNA repair in the neurons of the rat cerebral cortex after gamma irradiation at low doses].

External gamma irradiation of rats under 0.1-5 Gy causes nonreversible decreasing of DNA synthesis in brain cortices neurones in fare later (30 days after irradiation). The relative points number of excision initiation, which were calculated with the method of BrdU photolysis are much more than under normal condition and than just after irradiation also.

Animals↗