The Interaction of Water-Soluble Nitroxide Radicals with Photosystem II.

In this work, we investigated the redox transients of a number of water-soluble spin labels upon their interactions with Photosystem II (PS II) core complexes isolated from spinach leaves. We have found that the reactivity of nitroxide radicals, determined by the rate of their reduction upon illumination of PS II, depends on the chemical structure of radicals and the capability of their coming close to low-potential redox centers of photoactive PS II complexes. An enhanced capability of nitroxide radicals to accept electrons from PS II correlates with their chemical structure. Nitroxide radicals NTI (2,2,5,5-tetramethyl-4-nitromethylene-3-imidazolidine-N-oxyl) and Tacet (4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl-acetate), containing polar groups, appear to be most efficient acceptors of electrons donated by PS II compared to neutral (TEMPOL, 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl) or positively charged (Tamine, 4-amino-2,2,6,6-tetramethylpiperidine-l-oxyl) spin labels. We assume that enhanced reactivities of polar nitroxide radicals, NTI and Tacet, are determined (1) by their relatively high redox potentials, providing the possibility to accept electrons from PS II, and (2) by their affinities to the closest binding sites on the surface of PS II in the vicinity of the primary plastoquinone acceptor PQA (12-14 Å) or/and in the intraprotein cavity for the secondary plastoquinone PQB (~ 22 Å).

[Role of modified cardiovascular risk factors in development of oncologic diseases].

Cardiovascular (CVD) and oncological diseases (OD) are the main causes of death worldwide and account for a heavy burden on economy, disability and mortality in many countries. Clear understanding of the mechanisms shared by CVD and cancer is important for increasing the life span and quality of life in cancer survivors as well as for preventing comorbidities and correct instructing the patients about risk factors and lifestyle modifications. Both groups of diseases share risk factors, including smoking, obesity, diabetes mellitus, alcohol consumption, unhealthy diet, etc. Along with these factors, inflammation may play a key role as it promotes both types of diseases and accompanies obesity, diabetes mellitus, arterial hypertension, and dyslipidemia. Better understanding of the interaction between CVD and cancer will allow creating common effective diagnostic and preventive strategies and safe approaches to the treatment.

High-resolution structural insights into the heliorhodopsin family.

Rhodopsins are the most abundant light-harvesting proteins. A new family of rhodopsins, heliorhodopsins (HeRs), has recently been discovered. Unlike in the known rhodopsins, in HeRs the N termini face the cytoplasm. The function of HeRs remains unknown. We present the structures of the bacterial HeR-48C12 in two states at the resolution of 1.5 Å, which highlight its remarkable difference from all known rhodopsins. The interior of HeR's extracellular part is completely hydrophobic, while the cytoplasmic part comprises a cavity (Schiff base cavity [SBC]) surrounded by charged amino acids and containing a cluster of water molecules, presumably being a primary proton acceptor from the Schiff base. At acidic pH, a planar triangular molecule (acetate) is present in the SBC. Structure-based bioinformatic analysis identified 10 subfamilies of HeRs, suggesting their diverse biological functions. The structures and available data suggest an enzymatic activity of HeR-48C12 subfamily and their possible involvement in fundamental redox biological processes.

Electron Transfer on the Donor Side of Manganese-Depleted Photosystem 2.

After removal of manganese ions responsible for light-driven water oxidation, redox-active tyrosine YZ (tyrosine 161 of the D1 subunit) still remains the dominant electron donor to the photooxidized chlorophyll P680 (P680+) in the reaction center of photosystem 2 (PS2). Here, we investigated P680+ reduction by YZ under single-turnover flashes in Mn-depleted PS2 core complexes in the presence of weak acids and NH4Cl. Analysis of changes in the light-induced absorption at 830 nm (reflecting P680 redox transitions) at pH 6.0 showed that P680+ reduction is well approximated by two kinetic components with the characteristic times (τ) of ~7 and ~31 µs and relative contributions of ~54 and ~37%, respectively. In contrast to the very small effect of sodium formate (200 mM), addition of sodium acetate and NH4Cl increased the rate of electron transfer between YZ and P680+ approx. by a factor of 5. The suggestion that direct electron transfer from YZ to P680+ has a biphasic kinetics and reflects the presence of two different populations of PS2 centers was confirmed by the data obtained using direct electrometrical technique. It was demonstrated that the submillisecond two-phase kinetics of the additional electrogenic phase in the kinetics of photoelectric response due to the electron transfer between YZ and P680+ is significantly accelerated in the presence of acetate or ammonia. These results contribute to the understanding of the mechanism of interaction between the oxidized tyrosine YZ and exogenous substances (including synthetic manganese-containing compounds) capable of photooxidation of water molecule in the manganese-depleted PS2 complexes.

Na+-Translocating Ferredoxin:NAD+ Oxidoreductase Is a Component of Photosynthetic Electron Transport Chain in Green Sulfur Bacteria.

Genomes of photoautotrophic organisms containing type I photosynthetic reaction center were searched for the rnf genes encoding Na+-translocating ferredoxin:NAD+ oxidoreductase (RNF). These genes were absent in heliobacteria, cyanobacteria, algae, and plants; however, genomes of many green sulfur bacteria (especially marine ones) were found to contain the full rnf operon. Analysis of RNA isolated from the marine green sulfur bacterium Chlorobium phaeovibrioides revealed a high level of rnf expression. It was found that the activity of Na+-dependent flavodoxin:NAD+ oxidoreductase detected in the membrane fraction of Chl. phaeovibrioides was absent in the membrane fraction of the freshwater green sulfur bacterium Chlorobaculum limnaeum, which is closely related to Chl. phaeovibrioides but whose genome lacks the rnf genes. Illumination of the membrane fraction of Chl. phaeovibrioides but not of Cba. limnaeum resulted in the light-induced NAD+ reduction. Based on the obtained data, we concluded that in some green sulfur bacteria, RNF may be involved in the NADH formation that should increase the efficiency of light energy conservation in these microorganisms and can serve as the first example of the use of Na+ energetics in photosynthetic electron transport chains.

[Features of Cardiovascular Risk Factors, Target Organ Damage in Patients with Diabetes Mellitus Type 2 and Arterial Hypertension].

AIM: to investigate relationship between arterial hypertension (AH) and risk factors / subclinical damage of target organs in patients with type 2 diabetes mellitus (DM2). METHODS: We included into this clinical epidemiological study 528 patients with DM2 (30.5 % men, 69.5 % women; mean age 54.1±0.3 years; 80.3 % with AH, 19.7 % without AH), who answered questions of the ARIC study questionnaire related to risk factors. Also, we studied features of target organ damage and laboratory indicators. RESULTS: In comparison with normotensives patients with AH more frequently had ischemic heart disease (12.7±1.6 % vs. 5.8±2.3 %, p<0.05), chronic heart failure (CHF) (30.9±2.2 % vs. 9.6±2.9 %, p<0.001), atherosclerosis of vessels of lower extremities (69.8±2.2 % vs. 53.8±4.9 %, p<0.01) and cerebral vessels (50.9±2.4 % vs. 28.8±4.4 %, p<0.001), history of stroke (5.0±1.1 % vs. 0 %, p<0.05), hypertonic angiopathy (14.5±1.8 % vs. 6.5±2.5 %, p<0.05), low level of high density lipoprotein (87.3±2.2 % vs. 74.5±6.4 %, p<0.05), electro- and echocardiographic signs of left ventricular hypertrophy (75.6±2.1 % vs. 45.4±5.1 %, p<0.001; 61.1±2.6 % vs. 24.4±4.7 %, p<0.001, respectively), lowering of left ventricular ejection fraction (12.5±1.7 % vs. 7.8±2.8 %, p<0.001), diastolic disfunction of the left ventricle (52.6±2.7 % vs. 23.2±4.7 %, p<0.001), atherosclerosis of the aorta (38.0±2.6 % vs. 20.7±4.5 %, p<0.01), lowering of the ankle-brachial index (left - 29.8±2.3 % vs. 14.9±3.5 %, p<0.01; right - 31.5±2.3 % vs. 9.9±3.0 %, p<0.001, respectively), increased intima-media thickness of the right carotid artery (84.6±5.0 % vs. 60.0±11.0 %, p<0.05). CONCLUSION: In patients with type 2 diabetes and AH, in order to develop strategy of macro- and microvascular complications prevention, it is necessary to conduct early screening of risk factors and subclinical damage of target organs.

[Prevention of disoders of activity which associated with the risk of dynapenia and sarcopenia by combined aerobic-anaerobic training.]

The article presents the data of the study of different models of aerobic and anaerobic exercise in 208 elderly people (89 men and 119 women), which were divided into three groups. The 1st group (control) received standard recommendations of the doctor on the regime of physical activity (daily walks of at least 30 minutes). The 2nd group in addition to the standard recommendations received training in the form of Nordic walking with the regime of classes twice per week for 60 minutes. The 3rd group in addition to the standard recommendations received combined aerobic exercise in the form of Nordic walking twice per week for 60 minutes + anaerobic exercises with a frequency of training twice per week for 30 minutes. It was found that the best results of the increase in total activity, improved gait and stability, as well as increased muscle strength were achieved in the 3rd group of patients. Such, combined aerobic-anaerobic exercise can be recommended as a program of geriatric prevention of disorders associated with the risk of dynapenia and sarcopenia.

Hydroxyectoine protects Mn-depleted photosystem II against photoinhibition acting as a source of electrons.

In the present study, we have investigated the effect of hydroxyectoine (Ect-OH), a heterocyclic amino acid, on oxygen evolution in photosystem II (PS II) membrane fragments and on photoinhibition of Mn-depleted PS II (apo-WOC-PS II) preparations. The degree of photoinhibition of apo-WOC-PS II preparations was estimated by the loss of the capability of exogenous electron donor (sodium ascorbate) to restore the amplitude of light-induced changes of chlorophyll fluorescence yield (∆F). It was found that Ect-OH (i) stimulates the oxygen-evolving activity of PS II, (ii) accelerates the electron transfer from exogenous electron donors (K4[Fe(CN)6], DPC, TMPD, Fe2+, and Mn2+) to the reaction center of apo-WOC-PS II, (iii) enhances the protective effect of exogenous electron donors against donor-side photoinhibition of apo-WOC-PS II preparations. It is assumed that Ect-OH can serve as an artificial electron donor for apo-WOC-PS II, which does not directly interact with either the donor or acceptor side of the reaction center. We suggest that the protein conformation in the presence of Ect-OH, which affects the extent of hydration, becomes favorable for accepting electrons from exogenous donors. To our knowledge, this is the first study dealing with redox activity of Ect-OH towards photosynthetic pigment-protein complexes.

[Annual Scientific Session of American College of Cardiology 2018: Results of Clinical Studies].

The article contains report of 15 most important clinical studies presented at 67­th Annual Scientific Session of American College of Cardiology (Orlando, USA, March 10-12, 2018).

Congress of the European Society of Cardiology (Barcelona, 2017): Results of the Most Important Clinical Trials.

A report was presented on all four Hot Line: Late-Breaking Clinical Trials sessions of the European Society of Cardiology Congress 2017 on the results of new clinical research in cardiology.

[HEPATITIS C INFECTION SPECIFIC MARKERS AMONG PATIENTS WITH BREAST CANCER IN AZERBAIJAN].

The article presents results of comparative investigation of blood serum in 2682 breast cancer (BC) patients and 3323 healthy persons. At the onset of the study, all the specimens were tested for serum antibodies to hepatitis C virus (HCV). At the later stage, the serum specimens containing the antibodies were examined for detecting RNA GCV. Based on the obtained study results the authors concluded that BC patients can be considered as a high risk group for parenteral contamination with HCV. In addition, the authors have determined that HCV-infection course among BC patients is characterized by a low rate of recovery accompanied with spontaneous virus elimination and a high level of «viral load¼.

[Review of International Clinical Trials in the Field of Cardiology Reported in 2016].

We present in this article the review of 6 scientific Hot Line sessions of the 2016 European Congress of Cardiology devoted to novel approaches to treatment of heart failure, strategies of prevention of complications of cardiovascular diseases, dyslipidemia, imaging methods of investigation, and stenting in coronary heart disease.

[Laser technologies in treatment of posttraumatic rectal fistulas]. / Lechenie bol'nykh posttravmaticheskimi svishchami priamoi kishki s ispol'zovaniem lazernykh tekhnologii.

AIM: To assess the results of surgical treatment of posttraumatic rectal fistulas using current laser technology. MATERIAL AND METHODS: Surgical treatment of 134 (10.9%) patients with posttraumatic rectal fistulas was analyzed. The control group of conventional treatment included 58 (43.3±3.4%) patients, the main group - 76 (56.7±3.4%) patients. In the main group we used carbon dioxide laser device 'Lancet-2' (Russia) with a wavelength of 10.6 microns, capacity up to 20 W, and contact laser device 'Atkus-15' (Russia) with a wavelength of 0.81 microns and output power up to 15W. In postoperative period all patients underwent daily infrared laser irradiation of wound surface with an exposure of 5-10 min, wavelength of 0.635±0.005 microns, output power 25 mW ('UZOR-3 KS' (Russia, Kaluga)). RESULTS: The complex surgical treatment with modern laser technologies have reduced the incidence of complications from 19.0±5.1% to 7.9±3.1% (OR=0.37; 95% CI; 0.13-1.06, p<0.05). The long-term results improved in 50.0±13.4% of the control group and in 77.8±6.9% of the main group (χ2=5.22; p<0.05). CONCLUSION: Thus, laser technology has reduced twice the number of postoperative complications and improved long-ter. RESULTS: 98.2% of patients achieved medical and social rehabilitation in main group and 96.4% of patients in control group.

[Assessment of Relationship Between Cardiovascular Risk and Risk of Development of Diabetes Mellitus].

AIM: to analyze interrelationship between cardiovascular risk (CVR) and risk of development of diabetes mellitus (DM) in a cohort of working age men. MATERIAL AND METHODS: We enrolled in this study 300 men aged 40-59 years with more or equal 1 risk factors. Examination included questionnaire, standard clinical, instrumental, and laboratory studies. CVR and risk of developing DM was estimated using European SCORE scale and The Finnish Diabetes Risk Score (FINDRISC) respectively. RESULTS: In a group of men with low risk of DM prevailed subjects with low-moderate CVR; every fourth person in this group had high and every tenth - very high CVR. In the group of men with moderately high risk of DM every second subject had high and every third - very high CVR. In the group of men with high and very high risk of DM every second subject had very high CVR. DM risk correlated most closely with metabolic risk factors. Less pronounced but significant correlation existed between levels of DM and CVR risk and parameters of arterial pressure, lipid spectrum, age, and sedentary lifestyle. There was no significant correlation between DM risk and left ventricular hypertrophy, smoking, and tachycardia. CONCLUSION: Highest rate of very high CVR was revealed among men with high and very high risk of DM, while rate of high CVR in groups with moderately high and high risk of DM appeared to be comparable.

Trehalose protects Mn-depleted photosystem 2 preparations against the donor-side photoinhibition.

Recently, it has been shown that the addition of 1M trehalose leads to the increase of the rate of oxygen photoconsumption associated with activation of electron transport in the reaction center of photosystem 2 (PS2) in Mn-depleted PS2 membranes (apo-WOC-PS2) [37]. In the present work the effect of trehalose on photoinhibition of apo-WOC-PS2 preparations (which are characterized by a high sensitivity to the donor side photoinhibition of PS2) was investigated. The degree of photoinhibition was estimated by the loss of the capability of exogenous electron donor (sodium ascorbate) to reactivate the electron transport (measured by light-induced changes of chlorophyll fluorescence yield (∆F)) in apo-WOC-PS2. It was found that 1M trehalose enhanced the Mn2+-dependent suppression of photoinhibition of apo-WOC-PS2: in the presence of trehalose the addition of 0.2µM Mn2+ (corresponding to 2 Mn2+ per one reaction center) was sufficient for an almost complete suppression of the donor side photoinhibition of the complex. In the absence of trehalose it was necessary to add 100µM Mn2+ to achieve a similar result. The effect of trehalose was observed during photoinhibition of apo-WOC-PS2 at low (15µmolphotons-1m-2) and high (200µmolphotons-1m-2) light intensity. When Mn2+ was replaced by other PS2 electron donors (ferrocyanide, DPC) as well as by Ca2+ the protective effect of trehalose was not observed. It was also found that 1M trehalose decreased photoinhibition of apo-WOC-PS2 if the samples contained endogenous manganese (1-2 Mn ions per one RC was enough for the maximum protection effect). It is concluded that structural changes in PS2 caused by the addition of trehalose enhance the capability of photochemical reaction centers of apo-WOC-PS2 to accept electrons from manganese (both exogenous and endogenous), which in turn leads to a considerable suppression of the donor side photoinhibition of PS2.

Non-photochemical Fluorescence Quenching in Photosystem II Antenna Complexes by the Reaction Center Cation Radical.

In direct experiments, rate constants of photochemical (kP) and non-photochemical (kP(+)) fluorescence quenching were determined in membrane fragments of photosystem II (PSII), in oxygen-evolving PSII core particles, as well as in core particles deprived of the oxygen-evolving complex. For this purpose, a new approach to the pulse fluorometry method was implemented. In the "dark" reaction center (RC) state, antenna fluorescence decay kinetics were measured under low-intensity excitation (532 nm, pulse repetition rate 1 Hz), and the emission was registered by a streak camera. To create a "closed" [P680(+)QA(-)] RC state, a high-intensity pre-excitation pulse (pump pulse, 532 nm) of the sample was used. The time advance of the pump pulse against the measuring pulse was 8 ns. In this experimental configuration, under the pump pulse, the [P680(+)QA(-)] state was formed in RC, whereupon antenna fluorescence kinetics was measured using a weak testing picosecond pulsed excitation light applied to the sample 8 ns after the pump pulse. The data were fitted by a two-exponential approximation. Efficiency of antenna fluorescence quenching by the photoactive RC pigment in its oxidized (P680(+)) state was found to be ~1.5 times higher than that of the neutral (P680) RC state. To verify the data obtained with a streak camera, control measurements of PSII complex fluorescence decay kinetics by the single-photon counting technique were carried out. The results support the conclusions drawn from the measurements registered with the streak camera. In this case, the fitting of fluorescence kinetics was performed in three-exponential approximation, using the value of τ1 obtained by analyzing data registered by the streak camera. An additional third component obtained by modeling the data of single photon counting describes the P680(+)Pheo(-) charge recombination. Thus, for the first time the ratio of kP(+)/kP = 1.5 was determined in a direct experiment. The mechanisms of higher efficiency for non-photochemical antenna fluorescence quenching by RC cation radical in comparison to that of photochemical quenching are discussed.

The efficiency of non-photochemical fluorescence quenching by cation radicals in photosystem II reaction centers.

In a direct experiment, the rate constants of photochemical k p and non-photochemical k p+ quenching of the chlorophyll fluorescence have been determined in spinach photosystem II (PS II) membrane fragments, oxygen-evolving PS II core, as well as manganese-depleted PS II particles using pulse fluorimetry. In the dark-adapted reaction center(s) (RC), the fluorescence decay kinetics of the antenna were measured at low-intensity picosecond pulsed excitation. To create a "closed" P680+Q A- state, RCs were illuminated by high-intensity actinic flash 8 ns prior to the measuring flash. The obtained data were approximated by the sum of two decaying exponents. It was found that the antennae fluorescence quenching efficiency by the oxidized photoactive pigment of RC P680+ was about 1.5 times higher than that of the neutral P680 state. These results were confirmed by a single-photon counting technique, which allowed to resolve the additional slow component of the fluorescence decay. Slow component was assigned to the charge recombination of P680+Pheo- in PS II RC. Thus, for the first time, the ratio k p+ /k p â‰… 1.5 was found directly. The mechanism of the higher efficiency of non-photochemical quenching comparing to photochemical quenching is discussed.