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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.

External gamma irradiation of rats under 0.1-2 Gy causes decreasing of histone H1(0) contents on the first two days after irradiation and increasing in fare later in brain cortices neurones. These changes are observed in fraction of chromatin, which has high sensitivity to DNA digestion.

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.

Effect of natural and enriched with pectin tanned fruits on radiation-induced metabolic disorders was studied in persons subjected to radiation due to Chernobyl accident. It was shown that products in question beneficially influenced blood antioxidant system as well as brought to the norm contents of triglicerides and albumins in patients with IIa and IV types of hyperlipoproteinaemia.

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).

The influence of external single gamma-irradiation with a dose of 1 Gy on the isoenzyme composition of lactate dehydrogenase, malate dehydrogenase, esterase and acid phosphatase in the cytoplasm of rat brain cells has been investigated. Irradiation was shown to cause differently directed changes in the ratio of the isoenzymes under study at different times after exposure. The isoenzyme spectrum of lactate dehydrogenase and malate dehydrogenase was shown to be normalized on day 30 after irradiation, whereas the isoform composition of esterase and acid phosphatase was not stabilized at that time.

Single external gamma-irradiation in a dose of 0.5-2 Gy as well as the long-term (30 days) internal irradiation caused by the everyday influx of Cs-137 and Sr-85 isotopes to the organism have been studied for their effect on the activity and properties of histone-specific proteinase from the nuclei of the rat brain cortex cells. It is found out that external irradiation induces a dose-dependent increase of the activity during the first 24 hours after irradiation followed by its decrease 7-30 days later. Internal irradiation induces a decrease of the enzyme activity at the 30th day as well. Certain specificity of the studied indices depending on the type of irradiation has been also observed.

Exposure of rats to radiation in a dose of 1 Gy changes sensitivity of chromatin in the cerebral cortex cells to the action of DNAase 1, which promotes an increase of the DNA hydrolysis level and content of dissolved chromatin fractions. A day after irradiation the chromatin structure restores only partially and then (7-30 days after irradiation) it passes into a new, less compact state. The irradiation changes the chromatin ability to aggregation in the presence of Mg2+ and spermidine.

A method for isolating histone proteinase of rat brain chromatin is described, including ammonium sulphate fractionation gel filtration on sefacryl 5200, ion exchange chromatography on mono S and affinity chromatography with benzamidine sefarose. The enzyme molecular weight equals 25 kDa. It is purified 15621 times in comparison with initial nuclear extract.

Irradiation of rats with doses of 0.5 to 2 Gy was shown to cause dose-dependent changes in the sensitivity of brain cell chromatin to the effect of DNAase I that were manifested by the increased level of DNA hydrolysis and a high content of the chromatin soluble fractions. The chromatin structure was only partially restored 24 h after irradiation. Changes in the chromatin structure were accompanied by the increase in the histone-specific proteinase activity.

The accessibility to trypsin of "core" histones within the dimer (H2A-H2B), tetramer (H3-H4)2, octamer (H2A-H2B-H3-H4)2 and in chromatin was studied. It was shown that the hydrolysis of histones H2A and H2B within the dimer and octamer occurs in essentially the same way. The tetramer (H2-H4)2 becomes more compact with an increase in the ionic strength. Some of the tetramer (H3-H4)2 sites within the octamer are protected against trypsin. It was demonstrated that in terms of the histone accessibility to trypsin chromatin can exist in three states, i.e., tightly packed (in the presence of histone H1 and bivalent cations), intermediate (in the absence of histone H1 or bivalent cations) and folded (in the absence of histone H1 and bivalent cations). The folding of histones in neither of these chromatin states coincides with that within the octamer in 2M NaCl.

By optical methods it has been previously shown that the globular "head" of histone H1 forms a hydrophobic cavity containing Tyr72. The latter is screened from the polar water surrounding and its intramolecular mobility is drastically hindered. As a consequence of the alteration in the micromilieu are a long wave shift (lambda max = 279,5 nm) and a more pronounced longwave absorption spectra, higher anisotropy (A = 0,11), augmented quantum yield of fluorescence (approximately 0,2) and a decrease of the Stern-Volmer constant for Hl at fluorescence quenching by acrylamide. It was found that changes in fluorescence intensity of histones are connected with alterations in the quantum yield of fluorescence at lambda exc = = 265 nm, but not at lambda exc = 280 nm. The changes in fluorescence intensity at light excitation 280 nm (F280) and 265 nm (F265) are in good accordance with shift delta E286 in differential absorption spectra. Introduction of parameter Cf = F280/F265 allows to study shifts of excitation spectra instead of shifts in absorption spectra of histones. This method has certain advantages, since it permits investigations with lower protein concentrations and in turbid solutions. The data obtained allow to draw out Tyr72 of histone Hl into a special class of fluorescent-tyrosyls, that differ in properties from those of other tryptophandevoided proteins: RNAse, insulin and core-histones H2A, H2B, H3 and H4.

Kinetics of pyruvate transport through the envelope chloroplast vesicles has been studied. For wheat cultivar Bezostaya-1 Km is 26 mM, Vmax--33 Mmol/l h per 1 mg of protein, Hill's coefficient--0.56 and the coefficient of temperature inactivation at 40 degrees C is 0.045 min-1. 7 mM Mg or Ca ions for optimal activity of the system are needed. Chloroplast treatment with trypsin increases the pyruvate transport intensity. The simple analytical method is suggested for pyruvate determination at the concentration of 10-150 micrograms/ml.

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.

It has been found that histone octamer of calf thymus (H2A--H2B--H3--H4)2 can exist in two structural states--"loose" (2M NaCl) and "compact" one (4M NaCl). The compact state of the octamer is characterized by screening of part of tyrosyls for quenching effect of ions I-, longer relaxation time of tyrosyls, greater stability of histone H3 towards trypsinolysis, complete absence of interactions between histone H3 SH-groups and parachlormercuribenzoate.

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.

The spatial organization of the histone dimer (H2A-H2B) in 0.1-1.0 M NaCl is characterized by the inclusion of 38% of the residues in alpha-helical segments, an average fluorescence quantum yield of 0.085 +/- 0.003, a red shift of absorption (lambda max = 278 +/- 0.5 nm) and fluorescent spectra (lambda max = 304.4 +/- 0.3 nm) as compared to the respective spectra of free tyrosine. The changing of position lambda max of tyrosine fluorescence of histones during denaturation has been shown. The dimer (H2A-H2B) exhibited a conformational change in a transition centred at about 0.5 M NaCl. The dimer denaturation takes place at higher urea concentrations as the ionic strength of the medium increases. The quenching of tyrosine fluorescence of the histone dimer (H2A-H2B) was performed using the ions I-, Cs+ and acrylamide. It has been shown that, at a concentration of NaCl over 0.5 M, dimer compactization takes place, as well as the screening of some part of tyrosyls for te against the quenching effect of Cs+. Our experiments made it possible to identify three zones in the composition of the 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.

Molecules of histones H1 isolated from the calf thymus, carp testicles and spermatozoa as well as trypsin-stable fragments of these proteins have been studied from the standpoint of their structure and interaction using methods of differential spectrophotometry, gel filtration and turbidimetry. The globular structure of histone H1 of the calf thymus is formed with an increase in the ionic strength of the medium and it is eluted as dimer with gel chromatography. With a considerable local increase of ionic strength (by addition of NaCl crystals) molecules of histones H1 form high-molecular aggregates from all the studied tissues. This aggregation is a result of interaction of globular trypsin-stable sites. Molecules of histone H1 from carp testicles and spermatozoa as well as their trypsin-stable fragments revealed no differences in the ability to form dimers and aggregates.

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.

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.

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.

Structure of the (H2A-H2B-H3-H4)2 histone octamer isolated from calf thymus chromatin at ionic strength 0.1 to 4.0 M NaCl, pH 7.6, was studied spectrofluorometrically. Sensitivity of lambda max tyrosine fluorescence position to structural changes of histone oligomers and to the processes of their association was shown. It were detect two ranges of cooperative changes in histone optical parameters at 0.6-1.4 M NaCl (transition I) and at 2.4-3.4 M NaCl (transition II): Transition I corresponds to the formation of equilibrium system (hexamer) + (dimer) in equilibrium octamer. Transition II corresponds to the structural changes of the histone octamer. Thus, fluorescence anisotropy increases, lambda max for fluorescence spectrum is shifted to the longer wavelengths, contributions of two components to fluorescence decay change, a fraction of fluorescence accessible to the quenching by I- decreases. Histone octamer formation is characterized by making specific contacts between the (H2A-H2B) dimer and (H3-H4)2 tetramer. These contacts are realized at gradual changing of ionic strengths (by dialysis). In the case of abrupt local changes of the environment the process is irreversibly shifted to formation of unspecific high molecular aggregates. The important function role for energetically degenerated states of histone oligomers, energy barriers between which can be overcome by changing total conditions of histone microenvironment in chromatin is discussed.

Ca2+, phospholipid-dependent proteinkinase was isolated from intact and exposed (1 h following whole body X-irradiation with a dose of 0.21 C/kg) gray substance of rat brain, and the dependence of this enzyme on pH and temperature, and substrate specificity were studied. Changes were shown to occur in some Ca2+, phospholipid-dependent proteinkinase properties under the effect of X-radiation while the substrate specificity remained unchanged.

The native oligomers of histones isolated from calf thymus nuclear chromatin were investigated. After mild treatment with trypsin, the tetramer, (H3-H4)2, has a molecular weight of 36 000, whereas Mr of the dimer, H2a-H2b, is equal to 25 000. Intact oligomers have Mr of 55 000 (tetramer) and 33 000 (dimer). Analysis of the fluorescence intensity changes indicates that the native tetramer can exist in three, while the dimer in two conformational states. The (H2a-H2b) dimer persists, but the (H3-H4)2 tetramer does not persist these transitions after proteolytic degradation. The trypsin-treated dimer H2a-H2b is highly labile and readily aggregates, while the tetramer (H3-H4)2 loses its aggregation capacity. It is assumed that the conformational features observed during the aggregation of histone oligomers may play a role in the assembly and structural transitions in nucleosomes and chromatin.

In the region of 50 mM NaCl histone HI has the structure with a great number of binding sites with fluorescent probe 1.8-ANS as compared to the structure formed in solution of 0.6-1.0 M NaCl. These sites, however, have a lower constant of binding with the probe and are characterized by a higher surrounding polarity. At local significant increase of the ionic strength histone HI molecules form stable oligomers having hydrophobic cavities. A conclusion is made about the importance of cationic envelope formed by N- and C-ends around the globular "head", for manifesting effective interactions between several molecules of histone HI.