Zinc Switch in Pig Heart Lipoamide Dehydrogenase: Steady-State and Transient Kinetic Studies of the Diaphorase Reaction

Elevation of intracellular Zn2+ following ischemia contributes to cell death by affecting mitochondrial function. Zn2+ is a differential regulator of the mitochondrial enzyme lipoamide dehydrogenase (LADH) at physiological concentrations (K_a = 0.1 µM free zinc), inhibiting lipoamide and accelerating NADH dehydrogenase activities. These differential effects have been attributed to coordination of Zn2+ by LADH active-site cysteines. A detailed kinetic mechanism has now been developed for the diaphorase (NADH-dehydrogenase) reaction catalyzed by pig heart LADH using 2,6-dichlorophenol-indophenol (DCPIP) as a model quinone electron acceptor. Anaerobic stopped-flow experiments show that two-electron reduced LADH is 15-25-fold less active towards DCPIP reduction than four-electron reduced enzyme, or Zn2+-modified reduced LADH (the corresponding values of the rate constants are (6.5 ± 1.5) × 10³ M^-1·s^-1, (9 ± 2) × 10⁴ M^-1·s^-1, and (1.6 ± 0.5) × 10⁵ M^-1·s^-1, respectively). Steady-state kinetic studies with different diaphorase substrates show that Zn2+ accelerates reaction rates exclusively for two-electron acceptors (duroquinone, DCPIP), but not for one-electron acceptors (benzoquinone, ubiquinone, ferricyanide). This implies that the two-electron reduced form of LADH, prevalent at low NADH levels, is a poor two-electron donor compared to the four-electron reduced or Zn2+-modified reduced LADH forms. These data suggest that zinc binding to the active-site thiols switches the enzyme from one- to two-electron donor mode. This zinc-activated switch has the potential to alter the ratio of superoxide and H2O2 generated by the LADH oxidase activity.

[Evaluating the effectiveness of the new mouthguard design in athletes involved in power sports]

The aim of the study was to assess the effectiveness of the new mouthguard design for functional rehabilitation of dental system in athletes involved in contact power sports. The functional state of dental system was evaluated by interferential electromyography of masticatory muscles and Doppler ultrasound examination of periodontal tissues. Before mouthguard use the asynchrony of masticatory muscles was seen which was released after the mouthguard application: electromyographic activity of the left and right masticatory muscles was balanced and the decrease in biopotentials amplitude was found out. The mouthguard also caused no functional disorders in periodontal tissues.

[Prospects for the use of nanomaterials and high technology in dentistry. Part 1]

The paper presents the possibility of using biologically inert nanomaterials and high technology in prosthetic dentistry. Protective coating of nanostructured titanium VT1-00 magnetic elements of the locking system of removable dentures provides durability and biological inertness and high quality aesthetic design. In assessing the microstructure of titanium protective coating of ferromagnetic elements and samarium-cobalt magnets found that the nanocrystalline coating is formed, resistant to external influences, can significantly improve strength, technical and biological characteristics of samarium-cobalt magnets and ferromagnetic alloys. Fifteen patients were manufactured dentures with magnetic locks. The analysis of performance evaluation prosthetic treatment of patients with the use of the proposed prosthetic shows that the majority of patients (86.6%) obtained a good result. Patients registered restoration of aesthetic standards and the basic functions of dentition.

[Complex treatment approach in patients with lower jaw defects]

The aim of the study was to evaluate the clinical efficiency of modern materials in complex treatment of patients with lower jaw defects. The study demonstrates the advantages of biologically inert materials (carbon composite material "Uglekon-M" and titanium alloys) for lower jaw defect restoration.

[The assessment of the radiation quality of marine sediments]

The processes of ecosystems secondary pollution owing to interaction with bottom sediment are analyzed. Long-run consequences of contamination are investigated using the model describing the radionuclide migration dynamic in bottom sediment on account of transport processes due to diffusion and convection. Intricate bottom sediment forming procedure in water bodies of this kind is allowed. Model structure, numerical technique solution generation and analysis of results are represented.

[Relation between radiation safety criteria of human and the environment]

System approach is used for developing of procedures of complex radiation safety of human and the environment. Relation between radiation safety criteria of human and the environment is considered by the example of different strategies of water bodies using. It is demonstrated that as to water bodies (though the methodology and conclusions are correct to terrestrial ecosystems too) observance of human radiation safety standards on condition that environment resources are used unrestrictedly (considering radiation factor) is necessary and sufficient to protection of objects of the environment. It allows reaching compromise between anthropocentric and ecological approaches to radiation protection of the environment from general biospheric principles.

[Genetic monitoring of the Crimean-Congo Hemorrhagic Fever virus in Kazakhstan and Tajikistan in 2001-2003]

Blood specimens obtained from 32 CCHF patients were tested for the presence of CCHF virus markers. In addition, 3210 ticks of the genera Hyalomma asiaticum, Hyalomma anatolicum, and Dermacentor niveus were examined to identify the CCHF virus antigen and RNA. This material was obtained during the 2001-2003 local outbreaks of CCHF in Kazakhstan and Tajikistan. The nucleotide sequence in the region 983-1282 of S segment of the CCHF virus for 12 wild type strains was determined. The phylogenetic relationships among the established biovariants of CCHF virus, and also between these biovariants and those from other regions of the world were identified. We were the first to demonstrate the presence of an African-like genotype of CCHF virus in the territory of Kazakhstan. The conclusion was made that two genotypes of CCHF virus were in circulation in Kazakhstan. It was also demonstrated that CCHF virus, circulating in the territories of Kazakhstan and Tajikistan, was genetically heterogeneous.

[ELISA and RT-PCR-based research of viruses in the ticks collected in the foci of Crimean-Congo fever in Kazakhstan and Tajikistan in 2001-2002]

Different species of ticks were found, in the territories of Kazakhstan and Tajikistan, to be infected with the virus of Crimean-Congo hemorrhagic fever (CKHF). The virologic evaluation included determination of antigen and RNA of the CKHF virus by ELISA and RT-PCR, respectively. The below tick species were found to be involved in the epidemic process: Hyalomma asiaticum, Dermacentor niveus (Kazakhastan) and Hyalomma anatolicum (Tajikistan). The results testify to the fact that Hyalomma ticks are the main carrier of the above virus in the Middle Asia. At the same time, Dermacentor niveus ticks are infection carriers in Kazakhstan.

[Study of virus contamination of Ixodes ticks in the foci of Crimean-Congo hemorrhagic fever in Kazakhstan and Tajikistan]

The data on the contamination of different of ticks with Crimean-Congo hemorrhagic fever (CCHF) virus on the territory of Kazakhstan and Tajikistan were obtained. The methods of the evaluation of the virus contamination of ticks included the determination of the antigen and CCHF virus RNA by the methods of the enzyme immunoassay and the reverse transcription PCR respectively. Different tick species were found to be involved in the epidemic process: Hyalomma asiaticum, Dermatocentor niveus (Kazakhstan) and Hyalomma anatolicum (Tajikistan). The results obtained in this study confirmed that the main vector of CCHF virus in Central Asia were ticks of the genus Hyalomma, and in Kazakhstan the vectors of this virus also included ticks Dermatocentor niveus.

[The principles of radiological quality assessment of water resources]

In the paper the main approaches to radiation safety of water objects have been analyzed. It is shown that radiation safety requirements for drinking water, fixed in the Rules and Regulations on radiation safety, do not ensure radiation safety of water objects used for the complex national economy needs. Application of the conservatism principle (choosing of the worst variant) for radiation safety ensuring is considered and proved. On the base of this principle the model is developed comparing the anthropocentric (sanitary--hygienic) with ecological (biota) principles for ensuring safety of water objects. It is proved, that the application of the Water Radiation Safety Rules currently in force, based on the norms of dose quotas, reserved for regulation of nuclear power plants and industry impact, ensures safety of the water ecological systems.

[On hygienic and ecological approaches in radiation protection]

In this paper the problem of substantiation of one of the basic radiation protection ensurance principle is considered: sufficiency of a man radiation safety ensuring for guaranteed ensuring of radiation safety of the environment living components. This paradigm formulated in ICRP recommendations and is often referred to as hygienic or anthropocentric approach to environment radiation protection is laid down the basis of all national, including Russian, regulations in the field of radiation safety. During the last 5-10 years a lot of papers have been published, in which the hygienic principle of environmental safety ensuring is considered as a matter of dispute and the certain logical basis and the quantitative comparative estimations of human exposure doses and most irradiated vulnerable parts of nature doses are given. Change of one of the main radiation protection paradigms will demand for resolution of the enormously difficult and labor-consuming scientific problems. In the present paper, on the basis of UNSCEAR models of critical population groups dose formation and consistent application of conservativeness principle it is shown that for the ground ecosystems today there is no strong reasons for refusal of a hygienic radiation protection principle for benefit of ecological one.

Non-enzymatic interaction of reaction products and substrates in peroxidase catalysis

A quantitative approach for estimation of the non-enzymatic interaction between ammonium 2,2;-azino-bis(3-ethylbenzthiazoline-6-sulfonate) (ABTS) oxidation product and a poorly oxidized substrate was developed using a system including tobacco peroxidase, a mediator substrate (ABTS), and a second substrate. The approach is based on the establishment of a pseudo-steady-state concentration of the ABTS oxidation product in the course of co-oxidation with a poor substrate. A mathematical description of the experimental curve shape has been proposed to linearize the kinetic data and estimate the rate constant for such non-enzymatic interaction. The rate constants calculated from the steady-state kinetics for the non-enzymatic interaction of ABTS oxidation product with phenol and resorcinol were 360 +/- 40 and 770 +/- 60 M(-1).sec(-1), respectively. The values obtained have the same order of magnitude as the rate constant for ABTS oxidation product interaction with veratryl alcohol, calculated from electrochemical measurements (170 M(-1).sec(-1)) by Donal Leech's group. However, the kinetic curves for co-oxidation of ABTS and veratryl alcohol catalyzed by tobacco peroxidase exhibit a pronounced lag-period, which either points to the high rate of the non-enzymatic interaction between ABTS oxidation product and veratryl alcohol and thus, contradicts the electrochemical calculations, or indicates an enzymatic nature of the co-oxidation phenomenon in this particular case.

[Genetic identification of the Crimean-Congo hemorrhagic fever virus during epidemic outbreak in Kazakhstan in 2000]

Sera samples from patients suspected of Crimean-Congo hemorrhagic fever (CCHF) taken during epidemic outbreak at the territory of Sarysusky and Moiynkumsky districts of the Zhambyl region in Kazakhstan, in 2000, were analysed by means of reverse transcription-polymerase chain reaction (RT-PCR) and sequencing of virus genome fragments. Genome RNA of CCHF virus was found in 2 assays. Analysis of nucleotide sequences of fragments of S-segment of viral genome revealed in the Sarysusky districts circulation of CCHF virus, genetically resembled to close phylogenetically to CCHF virus strains from China.

Thermosensitive copolymers of N-vinylimidazole as displacers of proteins in immobilised metal affinity chromatography

Synthetic copolymers of N-vinylcaprolactam (VCL) and N-vinylimidazole (VI) were studied as thermosensitive, reusable displacers for immobilised metal affinity chromatography (IMAC) of proteins. The copolymer with weight-average molecular mass of 11700 g/mol prepared by free radical polymerisation at a 9:1 monomer molar ratio was separated into several fractions by IMAC and thermal precipitation. The fraction with an average VI content of 8.5% was most efficient as a reusable displacer for IMAC of ovalbumin, lysozyme and other proteins of egg white on Cu2+-IDA-Sepharose. The displacer exhibited a sharp breakthrough curve and binding capacity of 16-20 mg/ml gel, depending on the flow-rate. The recovery of egg white proteins in the course of displacement chromatography was >95%. The displacer could be removed quantitatively from the protein fractions by thermal precipitation at 48 degrees C. Co-precipitation of lysozyme with the displacer was minimal in the presence of 3% (v/v) acetonitrile, while the lysozyme enzymatic activity in the supernatant was completely retained. Addition of free imidazole to the mobile phase increased the rate of protein desorption and allowed better separation of egg white proteins and the displacer in the course of chromatography. The displacement profile of the egg white extract consisted of three zones with different distributions of individual proteins characterised by SDS-PAGE. Regeneration of the column was easily performed with 0.02 M EDTA in 0.15 M sodium chloride, pH 8.0, followed by washing with distilled water and reloading with Cu2+. The displacer could also be regenerated by thermal precipitation at 48 degrees C and subsequent dialysis against dilute hydrochloric acid (pH 2.5).

Interaction of antibodies and antigens conjugated with synthetic polyanions: on the way of creating an artificial chaperone

Recently we have initiated the use of synthetic polyelectrolytes to mimic the action of chaperones in living cells [Dainiak et al., Biochim. Biophys. Acta 1381 (1998) 279-285]. The next step in this direction is done by the synthesis of conjugates of poly(methacrylic acid) (PMAA) with antigen, denatured glyceraldehyde-3-phosphate dehydrogenase (dGAPDH), and with monoclonal antibodies specific for dGAPDH (but not for the native protein). The pH-dependent properties of the conjugates have been studied using turbidimetry and light scattering. The antibody-PMAA and dGAPDH-PMAA conjugates were shown to interact with free dGAPDH and antibodies respectively as well as with each other. Insoluble aggregates of dGAPDH with antibody-PMAA and of antibodies with dGAPDH-PMAA are formed in acidic media. The same situation occurs in the mixture of antibody-PMAA and dGAPDH-PMAA: precipitation takes place in acidic media, whereas soluble associates are formed in neutral solutions. The size of the soluble associates and the number of conjugates in the associate could be regulated by pH. The competition of free dGAPDH and dGAPDH-PMAA for binding with antibody-PMAA and the dynamic release of refolded GAPDH, with no affinity to antibody-PMAA, into solution could be used for simulating chaperone action.