Nanodomain structure of single crystalline nickel oxide.

In this work we present a comprehensive study of the domain structure of a nickel oxide single crystal grown by floating zone melting and suggest a correlation between point defects and the observed domain structure. The properties and structure of domains dictate the dynamics of resistive switching, water splitting and gas sensing, to name but a few. Investigating the correlation between point defects and domain structure can provide a deeper understanding of their formation and structure, which potentially allows one to tailor domain structure and the dynamics of the aforementioned applications. A range of inhomogeneities are observed by diffraction and microscopy techniques. X-ray and low-energy electron diffraction reveal domains on the submicron- and nanometer-scales, respectively. In turn, these domains are visualised by atomic force and scanning tunneling microscopy (STM), respectively. A comprehensive transmission electron microscopy (TEM) study reveals inhomogeneities ranging from domains of varying size, misorientation of domains, variation of the lattice constant and bending of lattice planes. X-ray photoelectron spectroscopy and electron energy-loss spectroscopy indicate the crystal is Ni deficient. Density functional theory calculations-considering the spatial and electronic disturbance induced by the favourable nickel vacancy-reveal a nanoscale distortion comparable to STM and TEM observations. The different inhomogeneities are understood in terms of the structural relaxation induced by ordering of nickel vacancies, which is predicted to be favourable.

New kind of interference in the case of X-ray Laue diffraction in a single crystal with uneven exit surface under the conditions of the Borrmann effect. Analytical solution.

The analytical solution of the problem of X-ray spherical-wave Laue diffraction in a single crystal with a linear change of thickness on the exit surface is derived. General equations are applied to a specific case of plane-wave Laue diffraction in a thick crystal under the conditions of the Borrmann effect. It is shown that if a thickness increase takes place at the side of the reflected beam, the related reflected wave amplitude is calculated as a sum of three terms, two of which are complex. If all three terms have a comparable modulus, it can lead to an increase in the reflected beam intensity by up to nine times due to interference compared with the value for a plane parallel shape of the crystal. The equation for the related transmitted wave amplitude contains only two terms. Therefore, the possibility to increase intensity is smaller compared with the reflected beam. The analytical solution is obtained after a solution of the integral equations by means of the Laplace transformation. A general integral form of the Takagi equations derived earlier is used. The results of relative intensity calculations by means of analytical equations coincide with the results of direct computer simulations.

Computer simulations of X-ray spherical wave dynamical diffraction in one and two crystals in the Laue case.

This article reports computer simulations of X-ray spherical wave dynamical diffraction in one and two single crystals in the Laue case. An X-ray compound refractive lens (CRL) as a secondary radiation source of spherical waves was considered for the first time and in contrast to previous simulations with the assumption of the use of a slit. The main properties of the CRL as a secondary source are discussed and two focusing phenomena are analysed. The first one is the diffraction focusing effect for one single crystal in the reflected beam and in the case of a large source-to-detector distance. The second one is the same but for two single crystals and for the twice-reflected beam in the case of a short distance between the source and detector. The first effect is well pronounced in the case of strong absorption. However, it may also be used as an element of an energy spectrometer in the medium and even weak absorption case. The second effect will appear in the case of weak absorption. It is shown that it is not effective to use it in an energy spectrometer. In the case of weak absorption the transverse size of the diffraction focused beam will oscillate together with the reflected beam integral intensity. The oscillation period is close to the extinction length.

A study of X-ray multiple diffraction by means of section topography.

The results of theoretical and experimental study are presented for the question of how the X-ray multiple diffraction in a silicon single crystal influences the interference fringes of section topography for the 400 reflection in the Laue case. Two different cases of multiple diffraction are discovered for zero and very small values of the azimuthal angle for the sample in the form of a plate with the surface normal to the 001 direction. The cases are seen on the same topogram without rotation of the crystal. Accurate computer simulations of the section topogram for the case of X-ray multiple diffraction are performed for the first time. It is shown that the structure of interference fringes on the section topogram in the region of multiple diffraction becomes more complicated. It has a very sharp dependence on the azimuthal angle. The experiment is carried out using a laboratory source under conditions of low resolution over the azimuthal angle. Nevertheless, the characteristic inclination of the interference fringes on the tails of the multiple diffraction region is easily seen. This phenomenon corresponds completely to the computer simulations.

[A New Enzyme Preparation with High Penicillopepsin Activity Based on the Producer Strain Penicillium canescens].

The producer of fungal penicillopepsin, an aspartate protease, has been created by genetic engineering. The biochemical and physicochemical properties of the penicillopepsin enzyme preparation obtained from the culture liquid of the producer were studied. Properties of the new enzyme preparation and the commercially available aspergillopepsin were compared. Their proteolytic activities were found to be 670-680 U/g of the preparation. The soluble protein yield upon the wheat flour hydrolysis with penicillopepsin was 2.7 times higher than with aspergillopepsin. It is probably caused by the presence of the xylanase activity in the penicillopepsin preparation.

[The polymorphism of catechol-O-methyltransferase (COMT) and hemochromatosis (HFE) genes in the radiocontaminated regions residents with different chromosome aberration frequency].

The association between polymorphisms in genes COMT, HFE that takes part in oxidative stress regulation, and chromosome aberration frequency in lymphocytes was assessed in 278 female residents of radiation polluted regions of Central Russia: Bryansk (322 kBk/m2) and Tula Districts (137Cs - 171 kBk/m2). The C187G, G845A genotyping of HFE and G1947A (H/L) of COMT was done by means of polymerase chain reaction-restriction fragment length polymorphism. Studied population was divided into 3 subgroups by level of chromosome aberrations per cell (0-2, 3-4, >5). There was shown statistically significant difference in distribution of COMTand HFE genotypes between the groups. The high frequency of chromosome aberrations (> or = 5%) was associated with homozygotes of the high activity COMT G/G and HFE CC. Heterozygotes for G1947A COMT and C187G HFE reveal negative association with the high frequency of chromosome aberrations and correspond to "resistance factors".

[The association of TCR-mutant cells with DNA polymorphism in women residing in radiation polluted regions of the Russian Federation].

Using flow-cytometric method the frequency of lymphocytes beaming mutations at T-cell receptor (TCR) locus was assessed in women residing in radiation polluted regions of Bryansk and Tula Districts. Simultaneously genotyping of the 8 polymorph loci for genes involved in detoxication of xenobiotics and oestrogen metabolism was carried out. The increased TCR-mutant cell frequency was found to be characteristic of homozygotes of the low activity appropriated enzymes for 3 loci (HFE187, GSTM1 and MTHFR) at least. This tendency was statistically significant in case of deletion polymorphism of the GSTM1 gene: TCR-mutant cell frequency of the homozygous carriers of a deletion at the GSTM1 locus was (4.63 +/- 0.18) x 10(-4) while it was (4.05 +/- 0.15) x 10(-4) in other groups of persons. The greatest mutant cell frequency was observed in carriers of the minor allele 4889G of the locus CYP1A. More often the increased values of the TCR-mutant cells (outside range "3sigma") were determined in women with genotypes A/G or G/G of the locus CYP1A1 (25%) than in carries of the normal genotype A/A (1.6%) (OR = 20.6; p = 0.0002). The comparison of the groups of women with reproductive system diseases reveals significant elevation in the mean TCR-mutant cell frequency in inhabitants of the most radiation polluted region among others.

[Somatic mutagenesis at T-cell receptor locus in inhabitants of radiation polluted regions as a result of the Chernobyl disaster].

In the period of 2001-2004, frequency of cells bearing mutations at T-cell receptor (TCR) locus was assessed in 553 inhabitants of radiation polluted regions of the Russian Federation and 154 unexposed control persons. The inhabitants were divided into three groups according to age at the moment of the Chernobyl disaster and 137Cs pollution density: 1) in utero, 37-555 kBq/m2; 2) 0-14 years old, 20-555 kBq/m2; 3) 18 and more years old, highest 137Cs density (185 more than 555 kBq/m2). The most intense changes of the TCR-mutant cell frequency were observed in the group of persons exposed to ionizing radiation in utero. The mean frequency of the mutant cells was higher in the first group than in age-matched control group by about 1.5-fold: 4.0 x 10(-4) vs 2.7 x 10(-4) accordingly (p < 0.0001). Elevation in the mean TCR-mutant cell frequency was less expressed in group of inhabitants aged 0-14 years at the moment of irradiation start: 1.3-fold increase in comparison to age-matched control (3.8 x 10(-4) vs 2.9 x 10(-4), p = 0.0002). It was not found significant differences in mutant cell frequencies between control group and adults consisting in the third group (18 and more years old at the moment of the Chernobyl accident). The changes of the TCR-mutant cell frequency in persons exposed in pre- and postnatal periods differ not only quantitatively, but qualitatively. In the fist case all persons react to irradiation by increasing number of the TCR-mutant cells in some degree. In the second case - only a part of population. Proportion of reacting persons depends on age at the start of irradiation and, perhaps, on dose absorbed. The TCR-mutant frequency was significantly higher in persons with benign tumors of different localizations and nodules in thyroid gland than in persons without this pathology.

Effects of etoposide and fludarabine in subtoxic doses on karyotype of human malignant lymphoid Namalwa cells.

We studied changes in the karyotype of transplanted Namalwa cells induced by DNA-damaging antitumor preparations etoposide and fludarabine in subtoxic doses. The relative number of cells containing increased number of chromosomes and the incidence of chromatid aberrations with primary damage to chromosomes 2, 5, 11, 16, and 17 increased. Cytogenetic changes developed even after short-term incubation of cells with antitumor preparations and were observed during further culturing in a medium not containing etoposide or fludarabine.

[Cytogenetic changes in the Namalwa cell line of human malignant lymphoma induced by inhibitors of DNA replication and synthesis]. / Tsitogeneticheskie izmeneniia v kletkakh perevivaemoi linii Namalwa zlokachestvennoi limfomy cheloveka, indutsirovannye ingibitorami replikatsii i sinteza DNK.

Namalwa cells originating from the malignant human lymphoma have been analyzed cytogenetically upon short-time exposure to subtoxic doses of inhibitors of DNA replication and synthesis, either etoposide or fludarabine. The intact cells were characterized by the modal class of the chromosomes within the diploid range with the proportion of the aberrant cells amounting to 16.0 +/- 0.5%. Upon exposure to etoposide the percentage of the aberrant cells increased amounting to 26.1 +/- 2.9 through 39.8 +/- 1.7% depending on the duration of the exposure and the dose of the drug. At the same time the number of the polyploid cells increased but the modal class retained within the diploid range. Upon exposure to fludarabine the percentage of the cells with the aberrant chromosomes increased to 57.1 +/- 2.9%. Two modal classes appeared--the first approaching the diploid number and the second being polyploid. The exposure to either etoposide or fludarabine resulted in increasing number of the chromatide aberrations with more frequent involvement of #1, #2, #5, #6, #7, #11, #13, #14, #16 and #17 chromosomes. The data obtained have shown the susceptibility of Namalwa cells to the subtoxic concentrations of the inhibitors of DNA synthesis and replication used in the study resulting in the survival of the novel clones resistant to the drugs.

Leukemia-associated gene rearrangements in blood mononuclears of subjects in long terms after radiation exposure.

The results of electron microscopy and molecular genetic study of blood mononuclears of 220 clean-up workers after 7-10 years since Chernobyl accident are presented. An increase of lymphocytes with altered ultrastructure of nuclei and membrane has been observed. Structural polymorphism of leukemia associated bcr and rRNA genes has been analyzed using Southern blot hybridization. Allelic polymorphism of bcr gene with allele distribution characteristic of myeloid leukemia and rearrangements of rRNA genes have been revealed in 11,5% of clean-up workers under study.

Aspartate-132 in cytochrome c oxidase from Rhodobacter sphaeroides is involved in a two-step proton transfer during oxo-ferryl formation.

The aspartate-132 in subunit I (D(I-132)) of cytochrome c oxidase from Rhodobacter sphaeroides is located on the cytoplasmic surface of the protein at the entry point of a proton-transfer pathway used for both substrate and pumped protons (D-pathway). Replacement of D(I-132) by its nonprotonatable analogue asparagine (DN(I-132)) has been shown to result in a reduced overall activity of the enzyme and impaired proton pumping. The results from this study show that during oxidation of the fully reduced enzyme the reaction was inhibited after formation of the oxo-ferryl (F) intermediate (tau congruent with 120 microseconds). In contrast to the wild-type enzyme, in the mutant enzyme formation of this intermediate was not associated with proton uptake from solution, which is the reason the DN(I-132) enzyme does not pump protons. The proton needed to form F was presumably taken from a protonatable group in the D-pathway (e.g., E(I-286)), which indicates that in the wild-type enzyme the proton transfer during F formation takes place in two steps: proton transfer from the group in the pathway is followed by faster reprotonation from the bulk solution, through D(I-132). Unlike the wild-type enzyme, in which F formation is coupled to internal electron transfer from CuA to heme a, in the DN(I-132) enzyme this electron transfer was uncoupled from formation of the F intermediate, which presumably is due to the impaired charge-compensating proton uptake from solution. In the presence of arachidonic acid which has been shown to stimulate the turnover activity of the DN(I-132) enzyme (Fetter et al. (1996) FEBS Lett. 393, 155), proton uptake with a time constant of approximately 2 ms was observed. However, no proton uptake associated with formation of F (tau congruent with 120 micros) was observed, which indicates that arachidonic acid can replace the role of D(I-132), but it cannot transfer protons as fast as the Asp. The results from this study show that D(I-132) is crucial for efficient transfer of protons into the enzyme and that in the DN(I-132) mutant enzyme there is a "kinetic barrier" for proton transfer into the D-pathway.

Observation of a novel transient ferryl complex with reduced CuB in cytochrome c oxidase.

The reaction between mixed-valence (MV) cytochrome c oxidase from beef heart with H2O2 was investigated using the flow-flash technique with a high concentration of H2O2 (1 M) to ensure a fast bimolecular interaction with the enzyme. Under anaerobic conditions the reaction exhibits 3 apparent phases. The first phase (tau congruent with 25 micros) results from the binding of one molecule of H2O2 to reduced heme a3 and the formation of an intermediate which is heme a3 oxoferryl (Fe4+=O2-) with reduced CuB (plus water). During the second phase (tau congruent with 90 micros), the electron transfer from CuB+ to the heme oxoferryl takes place, yielding the oxidized form of cytochrome oxidase (heme a3 Fe3+ and CuB2+, plus hydroxide). During the third phase (tau congruent with 4 ms), an additional molecule of H2O2 binds to the oxidized form of the enzyme and forms compound P, similar to the product observed upon the reaction of the mixed-valence (i.e., two-electron reduced) form of the enzyme with dioxygen. Thus, within about 30 ms the reaction of the mixed-valence form of the enzyme with H2O2 yields the same compound P as does the reaction with dioxygen, as indicated by the final absorbance at 436 nm, which is the same in both cases. This experimental approach allows the investigation of the form of cytochrome c oxidase which has the heme a3 oxoferryl intermediate but with reduced CuB. This state of the enzyme cannot be obtained from the reaction with dioxygen and is potentially useful to address questions concerning the role of the redox state in CuB in the proton pumping mechanism.

Examination of the reaction of fully reduced cytochrome oxidase with hydrogen peroxide by flow-flash spectroscopy.

The reaction of cytochrome c oxidase with hydrogen peroxide has been of great value in generating and characterizing oxygenated species of the enzyme that are identical or similar to those formed during turnover of the enzyme with dioxygen. Most previous studies have utilized relatively low peroxide concentrations (millimolar range). In the current work, these studies have been extended to the examination of the kinetics of the single turnover of the fully reduced enzyme using much higher concentrations of peroxide to avoid limitations by the bimolecular reaction. The flow-flash method is used, in which laser photolysis of the CO adduct of the fully reduced enzyme initiates the reaction following rapid mixing of the enzyme with peroxide, and the reaction is monitored by observing the absorbance changes due to the heme components of the enzyme. The following reaction sequence is deduced from the data. (1) The initial product of the reaction appears to be heme a(3) oxoferryl (Fe(4+)=O(2)(-) + H(2)O). Since the conversion of ferrous to ferryl heme a(3) (Fe(2+) to Fe(4+)) is sufficient for this reaction, presumably Cu(B) remains reduced in the product, along with Cu(A) and heme a. (2) The second phase of the reaction is an internal rearrangement of electrons and protons in which the heme a(3) oxoferryl is reduced to ferric hydroxide (Fe(3+)OH(-)). In about 40% of the population, the electron comes from heme a, and in the remaining 60% of the population, Cu(B) is oxidized. This step has a time constant of about 65 micros. (3) The third apparent phase of the reaction includes two parallel reactions. The population of the enzyme with an electron in the binuclear center reacts with a second molecule of peroxide, forming compound F. The population of the enzyme with the two electrons on heme a and Cu(A) must first transfer an electron to the binuclear center, followed by reaction with a second molecule of peroxide, also yielding compound F. In each of these reaction pathways, the reaction time is 100-200 micros, i.e., much faster than the rate of reaction of peroxide with the fully oxidized enzyme. Thus, hydrogen peroxide is an efficient trap for a single electron in the binuclear center. (4) Compound F is then reduced by the final available electron, again from heme a, at the same rate as observed for the reduction of compound F formed during the reaction of the fully reduced oxidase with dioxygen. The product is the fully oxidized enzyme (heme a(3) Fe(3+)OH(-)), which reacts with a third molecule of hydrogen peroxide, forming compound P. The rate of this final reaction step saturates at high concentrations of peroxide (V(max) = 250 s(-)(1), K(m) = 350 mM). The data indicate a reaction mechanism for the steady-state peroxidase activity of the enzyme which, at pH 7.5, proceeds via the single-electron reduction of the binuclear center followed by reaction with peroxide to form compound F directly, without forming compound P. Peroxide is an efficient trap for the one-electron-reduced state of the binuclear center. The results also suggest that the reaction of hydrogen peroxide to the fully oxidized enzyme may be limited by the presence of hydroxide associated with the heme a(3) ferric species. The reaction of hydrogen peroxide with heme a(3) is very substantially accelerated by the availability of an electron on heme a, which is presumably transferred to the binuclear center concomitant with a proton that can convert the hydroxide to water, which is readily displaced.

[The viral genome status studied under the conditions of a mixed infection in lymphoblastoid cells by adenovirus and the Epstein-Barr virus]. / Izuchenie sostoianiia virusnykh genomov v usloviiakh smeshannoi infektsii limfoblastoidnykh kletok adenovirusom i virusom Epshteina-Barr.

Some indices have been studied which characterized the state of Epstein-Barr virus genome and adenovirus in the implanted lines of lymphoblastoid cells of B and T phenotype under the mixed or monoinfection. It has been shown that super infection by type 2 adenovirus rather sharply affects the state of Epstein-Barr virus genome in the Raji cells containing integrated Epstein-Barr virus genome. The state of adenovirus genome in the studied cells is less subject to changes. Its early area is revealed by hybridization using DNA-DNA method in a form of two fragments of different intensity which is maximum in the Raji and Jurkat cells, which evidences for the more expressivity of adenovirus genome in these cells.

[Genomic disorders in the mononuclear blood cells of those who worked in the cleanup of the accident at the Chernobyl Atomic Electric Power Station]. / Issledovanie genomnykh narushenii v mononuklearakh krovi likvidatorov avarii na ChAES.

The results of molecular investigations of blood mononuclears from 120 clean-up workers after 7-9 years of Chernobyl accident with the total exposure radiation doses ranging from 5 to 76 cGr are presented. Structural polymorphism of the leukemia associated bcr and ribosomal RNA (rRNA) genes were studied using Southern blot hybridization. Allelic polymorphism of bcr gene with characteristic for leukemia allele distribution was detected in 16.6%. Rearrangements of rRNA genes were observed in 13% of Chernobyl accident clean-up workers.

HOQNO interaction with cytochrome b in succinate:menaquinone oxidoreductase from Bacillus subtilis.

2-n-Heptyl 4-hydroxyquinoline-N-oxide (HOQNO) inhibits the succinate:quinone oxidoreductase activity of isolated and membrane-bound succinate:menaquinone oxidoreductase of B. subtilis. The inhibition pattern resembles closely that observed for alpha-thenoyltrifluoroacetone and carboxins in the mitochondrial succinate:ubiquinone oxidoreductase: ca. 90% of the activity is highly sensitive to HOQNO (Ki ca. 0.2 microM for the isolated enzyme) whereas the rest 10% proves to be resistant to the inhibitor. HOQNO binding is shown to perturb the absorption spectrum of the ferrous di-heme cytochrome b of the B. subtilis succinate:quinone oxidoreductase both in the alpha and Soret bands. In addition, the inhibitor is shown to bring about a negative shift of Em of the low-potential heme b. It is suggested that HOQNO interacts with a menasemiquinone binding site near the low-potential heme and suppresses the MQ.(-)-to-MQH2 step of the quinone reductase reaction but allows partly for the MQ-to-MQ.- transition to occur; dismutation of MQ. formed in the latter reaction to MQ and MQH2 may account for the 10% of the enzyme activity insensitive to HOQNO.

Rapid kinetics of membrane potential generation by cytochrome c oxidase with the photoactive Ru(II)-tris-bipyridyl derivative of cytochrome c as electron donor.

Yeast iso-1-cytochrome c covalently modified at cysteine-102 with (4-bromomethyl-4'-methylbipyridine)[bis(bipyridine)]Ru2+ (Ru-102-Cyt c) has been used as a photoactive electron donor to mitochondrial cytochrome c oxidase (COX) reconstituted into phospholipid vesicles. Rapid kinetics of membrane potential generation by the enzyme following flash-induced photoreduction of Ru-102-Cyt c heme has been measured and compared to photovoltaic responses observed with Ru(II)(bipyridyl)3 (RuBpy) as the photoreductant [D.L. Zaslavsky et al. (1993) FEBS Lett. 336, 389-393]. At low ionic strength, when Ru-102-Cyt c forms a tight electrostatic complex with COX, flash-activation results in a polyphasic electrogenic response corresponding to transfer of a negative charge to the interior of the vesicles. The initial rapid phase is virtually identical to the 50 microsecond transient observed in the presence of RuBpy as the photoactive electron donor which originates from electrogenic reduction of heme a by CuA. CuA reduction by Ru-102-Cyt c turns out to be not electrogenic in agreement with the peripheral location of visible copper in the enzyme. A millisecond phase (tau ca. 4 ms) following the 50 microsecond initial part of the response and associated with vectorial translocation of protons linked to oxygen intermediate interconversion in the binuclear centre, can be resolved both with RuBpy and Ru-102-Cyt c as electron donors; however, this phase is small in the absence of added H2O2. In addition to these two transients, the flash-induced electrogenic response in the presence of Ru-102-Cyt c reveals a large slow phase of delta psi generation not observed with RuBpy. This phase is completely quenched upon inclusion of 100 microM ferricyanide in the medium and originates from a second order reaction of COX with the excess Ru-102-Cyt c2+ generated by the flash in a solution.

[Oxygenated cytochrome bd from Escherichia coli could be transformed into an oxidized form by lipophilic electron acceptors]. / Oksigenirovannyi tsitokhrom bd iz Escherichia coli mozhet byt' prevrashchen v okislennuiu formu lipofil'nymi aktseptorami élektronov.

The cytochrome bd complex as isolated from Escherichia coli under aerobic conditions is in a stable oxygenated form [formula: see text], characterized by an intense peak at 650 nm in an absolute absorption spectrum. The commonly used oxidants ferricyanide and persulfate have no effect on the oxygenated form, whereas the addition of lipophilic electron acceptors, such as tetrachlorobenzoquinone or ferricinium, results in the decay of the heme d oxy-complex and the enzyme transition into the fully oxidized form, [formula: see text]. Interaction of the oxygenated cytochrome bd complex with both tetrachlorobenzoquinone and ferricinium is suppressed by pentachlorophenol, an inhibitor of the enzyme ubiquinol oxidase activity. It is suggested that redox centers of cytochrome bd reside in the hydrophobic environment which can prevent their interaction with the hydrophilic oxidants.