The Study of Thermal Stability of Mn-Zr-Ce, Mn-Ce and Mn-Zr Oxide Catalysts for CO Oxidation.

MnOx-CeO2, MnOx-ZrO2, MnOx-ZrO2-CeO2 oxides with the Mn/(Zr + Ce + Mn) molar ratio of 0.3 were synthesized by coprecipitation method followed by calcination in the temperature range of 400-800 °C and characterized by XRD, N2 adsorption, TPR, TEM, and EPR. The catalytic activity was tested in the CO oxidation reaction. It was found that MnOx-CeO2, MnOx-ZrO2-CeO2, MnOx-ZrO2 catalysts, calcined at 400-500 °C, 650-700 °C and 500-650 °C, respectively, show the highest catalytic activity in the reaction of CO oxidation. According to XRD and TEM results, thermal stability of catalysts is determined by the temperature of decomposition of the solid solution Mnx(Ce,Zr)1-xO2. The TPR-H2 and EPR methods showed that the high activity in CO oxidation correlates with the content of easily reduced fine MnOx particles in the samples and the presence of paramagnetic defects in the form of oxygen vacancies. The maximum activity for each series of catalysts is associated with the start of solid solution decomposition. Formation of active phase shifts to the high-temperature region with the addition of zirconium to the MnOx-CeO2 catalyst.

Analysis of the impact on the health care budget and consumers of the use of the preparation of omega-3 acid ethyl esters90 in the treatment of patients with atherogenic dyslipidemia.

Aim      To evaluate economic results of using omega-3 acid ethyl esters 90 for primary prevention of cardiovascular catastrophes in patients with residual hypertriglyceridemia (HTG).Material and methods  The economic evaluation of using the medicine omega-3 acid ethyl esters 90 in the system of drug provision of the population of the Russian Federation was performed by analyzing the effect on the budget using a pharmacoeconomic model developed with the Microsoft Office Excel 2016 software. The effect of omega-3 acid ethyl esters 90 was evaluated in 555 643 patients with residual HGT (Moscow). The study lasted for one year. Results of the meta-analysis by A.A. Bernasconi et al. (2020) were used as a source of efficacy data. The following direct and indirect medical expenses for treatment of cardiovascular complications of residual HTG were taken into account in this study: expenses for drug therapy; expenses for therapy and rehabilitation for nonfatal complications; expenses for fatal outcomes; state support for disability; foregone per capita gross domestic product resulting from losses of earnings due to temporary incapacity to labor by people of work-able age; and salary payments for temporary incapacity to work.Results Using omega-3 acid ethyl esters 90 in 555 643 patients with residual HTG will allow preventing 1 437 fatal ischemic cardiovascular complications (including 564 deaths from ischemic heart disease and 1 128 cases of myocardial infarction (MI), including 558 fatal cases of MI). Furthermore, the difference in expenses compared to the high-dose statin treatment alone will be 359 252 253 rubles or 0.32 %.Conclusion      The results of this comprehensive pharmacoeconomical study showed that the use of omega-3 acid ethyl esters 90 in patients with residual HGT is an economically preferrable strategy compared to high-dose statin treatment alone and does not influence significantly the budgetary expenses as a part of the State Guarantee of Free Medical Care to the Citizens of the Russian Federation (increase in expenses by 0.32 % compared to the current practice). At the same time, the use of omega-3 acid ethyl esters 90 results in a 10% decrease in the number of fatal ischemic cardiovascular complications.

A geochemical study of the Ediacaran discoidal fossil Aspidella preserved in limestones: Implications for its taphonomy and paleoecology.

The Ediacara biota features the rise of macroscopic complex life immediately before the Cambrian explosion. One of the most abundant and widely distributed elements of the Ediacara biota is the discoidal fossil Aspidella, which is interpreted as a subsurface holdfast possibly anchoring a frondose epibenthic organism. It is a morphologically simple fossil preserved mainly in siliciclastic rocks, which are unsuitable for comprehensive stable isotope geochemical analyses to decipher its taphonomy and paleoecology. In this regard, three-dimensionally preserved Aspidella fossils from upper Ediacaran limestones of the Khatyspyt Formation in the Olenek Uplift of northern Siberia offer a rare opportunity to leverage geochemistry for insights into their taphonomy and paleoecology. To take advantage of this opportunity, we analyzed δ13 Ccarb , δ18 Ocarb , δ13 Corg , δ34 Spyr , and iron speciation of the Khatyspyt Aspidella fossils and surrounding sediment matrix in order to investigate whether they hosted microbial symbionts, how they were fossilized, and the redox conditions of their ecological environments. Aspidella holdfasts and surrounding sediment matrix show indistinguishable δ13 Corg values, suggesting they did not host and derive significant amount of nutrients from microbial symbionts such as methanogens, methylotrophs, or sulfide-oxidizing bacteria. δ13 Ccarb , δ18 Ocarb , and δ34 Spyr data, along with petrographic observations, suggest that microbial sulfate reduction facilitated the preservation of Aspidella by promoting early authigenic calcite cementation in the holdfasts before matrix cementation and sediment compaction. Iron speciation data are equivocal, largely because of the low total iron concentrations. However, consideration of published sulfur isotope and biomarker data suggests that Aspidella likely lived in non-euxinic waters. It is possible that Aspidella was an opportunistic organism, colonizing the seafloor in large numbers when paleoenvironments were favorable. This study demonstrates that geochemical data of Ediacaran fossils preserved in limestones can offer important insights into the taphonomy and paleoecology of these enigmatic organisms living on the eve of the Cambrian explosion.

Methods for Studying Interactions Between Atg8/LC3/GABARAP and LIR-Containing Proteins.

LC3/GABARAP proteins (LC3/GABARAPs) are mammalian orthologues of yeast Atg8, small ubiquitin (Ub)-like proteins (UBLs) whose covalent attachment to lipid membranes is crucial for the growth and closure of the double membrane vesicle called the autophagosome. In the past decade, it was demonstrated that Atg8/LC3/GABARAPs are also required for autophagic degradation of cargos in a selective fashion. Cargo selectivity is ensured by receptor proteins, such as p62/SQSTM1, NBR1, Cue5, Atg19, NIX, Atg32, NCOA4, and FAM134B, which simultaneously bind Atg8/LC3/GABARAPs and the cargo together, thereby linking the core autophagic machinery to the target structure: a protein, an organelle, or a pathogen. LC3-interacting regions (LIRs) are short linear motifs within selective autophagy receptors and some other structural and signaling proteins (e.g., ULK1, ATG13, FIP200, and Dvl2), which mediate binding to Atg8/LC3/GABARAPs. Identification and characterization of LIR-containing proteins have provided important insights into the biology of the autophagy pathway, and studying their interactions with the core autophagy machinery represents a growing area of autophagy research. Here, we present protocols for the identification of LIR-containing proteins, i.e., by yeast-two-hybrid screening, glutathione S-transferase (GST) pulldown experiments, and peptide arrays. The use of two-dimensional peptide arrays also represents a powerful method to identify the residues of the LIR motif that are critical for binding. We also describe a biophysical method for studying interactions between Atg8/LC3/GABARAP and LIR-containing proteins and a protocol for preparation and purification of LIR peptides.

A source of a reference spherical wave based on a single mode optical fiber with a narrowed exit aperture.

A new type of a reference spherical wave source (SWS) based on a single mode optical fiber with a narrowed down up to the submicrometer size exit aperture is proposed. It is intended for the precision point diffraction interferometers as a source of a reference wave. Systematic experimental errors which influence the measurement accuracy of the quality of the wave fronts generated by the SWSs are considered. Experimental data on wave front deformations are given. The combined root-mean-square (rms) wave deformation for a couple of the SWSs measured in a numerical aperture of NA=0.27 reaches the value of rms=0.36 nm that corresponds to rms=0.25 nm of a single SWS or about lambda2500 for the red He-Ne laser.

Ubiquitin binding mediates the NF-kappaB inhibitory potential of ABIN proteins.

Deregulated nuclear factor kappaB (NF-kappaB) activation plays an important role in inflammation and tumorigenesis. ABIN proteins have been characterized as negative regulators of NF-kappaB signaling. However, their mechanism of NF-kappaB inhibition remained unclear. With the help of a yeast two-hybrid screen, we identified ABIN proteins as novel ubiquitin-interacting proteins. The minimal ubiquitin-binding domain (UBD) corresponds to the ABIN homology domain 2 (AHD2) and is highly conserved in ABIN-1, ABIN-2 and ABIN-3. Moreover, this region is also present in NF-kappaB essential modulator/IkappaB kinase gamma (NEMO/IKKgamma) and the NEMO-like protein optineurin, and is therefore termed UBD in ABIN proteins and NEMO (UBAN). Nuclear magnetic resonance studies of the UBAN domain identify it as a novel type of UBD, with the binding surface on ubiquitin being significantly different from the binding surface of other UBDs. ABIN-1 specifically binds ubiquitinated NEMO via a bipartite interaction involving its UBAN and NEMO-binding domain. Mutations in the UBAN domain led to a loss of ubiquitin binding and impaired the NF-kappaB inhibitory potential of ABINs. Taken together, these data illustrate an important role for ubiquitin binding in the negative regulation of NF-kappaB signaling by ABINs and identify UBAN as a novel UBD.

[Chronic glomerulonephritis and pregnancy]. / Khronicheskii glomerulonefrit i beremennost'.

AIM: To clarify factors of risk for unfavourable variants of gestational chronic glomerulonephritis (CGN) and poor pregnancy outcomes in CGN; to determine prognostic implications of changes in some renal and uteroplacental indices. MATERIAL AND METHODS: Variants of CGN gestational course and pregnancy outcomes have been analysed for 156 CGN patients. The women were examined before pregnancy, in the course of pregnancy and 3-24 months after the delivery. Measurements were made of 24 h proteinuria, glomerular filtration rate, blood transaminases activity, functional renal reserve (FRR), uricemia, blood level of alpha-phetoprotein. Placentas were studied morphologically, uterine and umbilical artery circulation was assessed by dopplerometry. RESULTS: The following abnormalities were registered: high proteinuria (34.6%), progression of hypertension (29.5%), renal function deterioration (15.4%), fetal and neonatal losses (15.4%), fetal underdevelopment (25%), preterm delivery (17.3%), preeclampsia (7.7%), preterm placental detachment (1.9%). There is morphological, dopplerometric and biochemical evidence for placental insufficiency in CGN pregnant women. CONCLUSION: Activity of CGN (nephritic or acute nephritic syndromes), hypertension, renal failure, disorders of renal hemodynamics are factors of risk for unfavourable gestational course of CGN and pregnancy complications. Placental insufficiency deteriorates pregnancy outcomes in CGN, but changes in uterine and umbilical circulation as well as blood levels of alpha-fetoprotein are not prognostically significant.

[Endothelium and platelets in pregnant women with chronic glomerulonephritis and therapeutic efficacy of acetylsalicylic acid and dipiridamol]. / Sostoianie endoteliia i trombotsitov u beremennykh s khronicheskim glomerulonefritom i lechebnymi vozvozhnosti atsetilsalitsilovoi kisloty i dipiridamola.

AIM: To estimate platelet and endothelial condition in pregnant women with chronic glomerulonephritis (CGN), prognostic value of these changes and efficacy of acetylsalicylic acid (ASA) and dipiridamol in prevention of unfavourable outcomes of pregnancy in CGN. MATERIAL AND METHODS: The examination covered 74 CGN pregnant patients, 14 non-pregnant CGN patients, 11 pregnant women with preeclampsia, 19 healthy pregnant women. The levels of fibronectin, endothelin-1,2, 6-keto-PGF1a, thromboxane B2 (TxB2) secretory beta-thromboglobulin in the blood, activity of intrathrombocytic lactate dehydrogenase (LHG), platelet aggregation. ASA (125 mg/day) was given to 33 CGN pregnant women in combination with dipiridamol (150-225 mg/day). Control group consisted of 32 CGN pregnant women. RESULTS: Content of fibronectin, endothelin, TxB2 and beta-thromboglobulin in blood plasm, aggregation with ADP in CGN pregnant women were higher than in healthy pregnant women and nonpregnant CGN patients. Plasmic 6-keto-PGF1a was low. Preeclampsia was accompanied with elevated fibronectin, TxB2 and beta-thromboglobulin, hyperactive LDH. Platelet aggregation was suppressed. Blood beta-thromboglobulin directly correlated with systolic and diastolic arterial pressure, 24-h proteinuria and blood creatinine. Reverse Correlation was seen in blood beta-thromboglobulin with albuminemia, glomerular filtration rate, body mass of the newborn and term of labor. A direct correlation was found between the activity of intrathrombocytic LDH and systolic and diastolic arterial pressure, a weak reverse correlation--between platelet count in capillary blood and systolic pressure, platelet aggregation with ADP and terms of labor. Of the highest prognostic value were the level of beta-thromboglobulin and fibronectin, the activity of intrathrombocytic LDH and platelet aggregation in response to ADP. ASA and dipiridamol reduced the risk of fetal retardation and fetal loss. CONCLUSION: Pregnant women with CGN have endothelial-thrombocytic dysfunction because of unidirectional influence of both CGN and pregnancy. We think that endothelial-platelet dysfunction connects renal impairment and placental failure in pregnant women with CGN deteriorating a gestational CGN and pregnancy complications. Correction of endothelial-platelet state with ASA and dipiridamol is effective in prevention of fetal retardation and fetal loss in pregnant women with CGN.

[Renal and uterine hemodynamics in pregnancy with chronic glomerulonephritis of the hypertonic type]. / Pochechnaia i matochnaia gemodinamika u beremennykh s khronicheskim glomerulonefritom gipertonicheskogo tipa.

AIM: To study gestational changes in renal and uterine hemodynamics and their relation to systemic and intracardiac hemodynamics in pregnant hypertensive women with chronic glomerulonephritis (CGN). MATERIAL AND METHODS: Echocardiography, ultrasonic dopplerography of renal and uterine arteries were made in 16 pregnant women with CGN and AH syndrome in trimester II-III and 1-3 months after the delivery. Hemodynamic indices in pregnancy were compared to those after the delivery which were considered baseline. RESULTS: In CGN pregnant women with AH syndrome resistance of renal arteries did not change in pregnancy and were similar postpartum. With advancing pregnancy, the resistance of the uterine arteries diminished. The indices of the resistance in the main trunk of the renal artery correlated with volumetric cardiohemodynamic indices, heart rate and total peripheral resistance in segmental interlobular arteries. No significant correlation were found between uterine, systemic and cardiac hemodynamics though it existed between renal and uterine blood flow. CONCLUSION: Pregnancy does not affect vascular resistance of renal arteries in CGN pregnant women with AH syndrome, but contrary to pregnancy with essential hypertension in that with CGN and AH syndrome renal circulation responds to changes in systemic hemodynamics and volumetric indices of cardiohemodynamics. These findigns may reflect disturbances in autoregulation of renal circulation and additional effects on pregnancy outcome in women with CGN and AH syndrome.

[Use of angiotensin-converting enzyme inhibitors in chronic kidney insufficiency]. / Primenenie ingibitorov angiotenzinprevrashchaiushchego fermenta pri khronicheskoi pochechnoi nedostatochnosti.

AIM: To study effects of ACE inhibitors in patients with diffuse renal diseases at the stage of chronic renal failure (CRF). MATERIAL AND METHODS: Acute changes in renal filtration and in renal hemodynamics in response to 100-200 mg captopril were studied in 7 patients with CRF and 6 patients with intact renal function. Effects of long-term ACE inhibitors were retrospectively studied in 50 patients with CRF (27 men, 23 women, mean age 46.0 +/- 1.9 years, 7 patients were over 60 years old). Sixteen patients were selected from this group who were followed up for a long time. They were examined for CRF progression rate when given conventional antihypertensive treatment and after treatment with ACE inhibitors. RESULTS: Acute response to ACE inhibitors was the following: SCF fell by 18.4% on the average by the end on therapy week 1; by the end of week 3 renal hemodynamics showed stability, SCF returned to normal, effective renal plasm flow rose by 16.9%, serum potassium rose significantly after 7 days of treatment but did not reach 6 mmol/l. Effects of long-term ACE inhibitor in CRF: the treatment was discontinued after 30-60 days in 12 of 50 patients because of high creatinine (> 20%); in 38 patients ACE inhibitor had a pronounced antihypertensive and antiproteinuric action for 2-3 years, creatinine growth inhibited. Progression of CRF became slow. CONCLUSION: ACE-inhibitors in CRF had a nephroprotective effect but blood creatinine levels should be controlled especially within the first 1-2 months of treatment.

Solution structure and dynamics of the functional domain of Paracoccus denitrificans cytochrome c(552) in both redox states.

A soluble and fully functional 10.5 kDa fragment of the 18.2 kDa membrane-bound cytochrome c(552) from Paracoccus denitrificans has been heterologously expressed and (13)C/(15)N-labeled to study the structural features of this protein in both redox states. Well-resolved solution structures of both the reduced and oxidized states have been determined using high-resolution heteronuclear NMR. The overall protein topology consists of two long terminal helices and three shorter helices surrounding the heme moiety. No significant redox-induced structural differences have been observed. (15)N relaxation rates and heteronuclear NOE values were determined at 500 and 600 MHz. Several residues located around the heme moiety display increased backbone mobility in both oxidation states, while helices I, III, and V as well as the two concatenated beta-turns between Leu30 and Arg36 apparently form a less flexible domain within the protein structure. Major redox-state-dependent differences of the internal backbone mobility on the picosecond-nanosecond time scale were not evident. Hydrogen exchange experiments demonstrated that the slow-exchanging amide proton resonances mainly belong to the helices and beta-turns, corresponding to the regions with high order parameters in the dynamics data. Despite this correlation, the backbone amide protons of the oxidized cytochrome c(552) exchange considerably faster with the solvent compared to the reduced protein. Using both differential scanning calorimetry as well as temperature-dependent NMR spectroscopy, a significant difference in the thermostabilities of the two redox states has been observed, with transition temperatures of 349.9 K (76.8 degrees C) for reduced and 307.5 K (34.4 degrees C) for oxidized cytochrome c(552). These results suggest a clearly distinct backbone stability between the two oxidation states.

[Renal and uterine hemodynamics in pregnant women with hypertension]. / Pochechnaia i matochnaia gemodinamika u beremennykh s gipertonicheskoi bolezn'iu.

AIM: To study gestational alterations of renal and uterine hemodynamics, their relationships with systemic and intracardiac hemodynamics in pregnant women (PW) with essential hypertension (EH). MATERIAL AND METHODS: Echocardiography, ultrasound dopplerography of renal and uterine arteries, roll-over test were made in the course of trimester II-III and 3 months after the delivery in 48 PW with EH degree 1-2 and control 20 healthy PW. Hemodynamic parameters in pregnancy were compared to postpartum ones. The latter were supposed to be basal. RESULTS: Changes in systemic and intracardiac hemodynamics in EH and control women were in many respects similar but systolic blood pressure in EH changed insignificantly, minute volume increased owing to increased heart rate. PW with EH of the second degree have in the III trimester more frequent positive roll-over test this evidencing for high pressor reactivity of the vascular system. PW with EH showed higher speed of the blood flow in the renal arteries in unchanged resistance. With growing gestation time the resistance of the uterine arteries declined. The resistance of the main stem of the renal artery went up in enhanced cardiac contraction regardless of total peripheral vascular resistance (TPVR). Blood flow in the uterine arteries worsened in elevation of arterial pressure, TPVR, lowering of the heart rate and systolic function of the heart. Renal and uterine hemodynamics were independent. CONCLUSION: Hemodynamic changes in control and EH PW were similar in many respects but higher arterial pressure, abnormal systolic function of the left ventricle, bradycardia disturb uterine blood flow. Renal circulation was independent of systemic and intracardiac hemodynamics and is unrelated to changes in the uterine circulation.

[Lupus nephritis and pregnancy]. / Volchanochnyi nefrit i beremennost'.

AIM: To evaluate effects of pregnancy on the course and prognosis of lupus nephritis and fetal outcome, in particular, in patients with lupus nephritis (LN) and antiphospholipid syndrome (APS). MATERIAL AND METHODS: A retrospective analysis was made of the course of LN in 31 females (44 pregnancies). RESULTS: A favorable outcome of pregnancy is possible in LN women if they had a persistent remission at conception. However, one third of these women had exacerbations of LN in pregnancy and early postpartum period. Pregnancy developing in active LN aggravated LN course in all the women. Fetal outcome was unfavorable. LN was especially severe if it arose in the course of pregnancy or early postpartum period. It seems that the presence of APS affected pregnancy outcome in a less degree than LN activity. CONCLUSION: Both in pregnancy and postpartum period, LN showed frequent exacerbations, but if the conception takes place during a persistent remission of LN, under adequate care and treatment, a delivery of a viable child is possible without an extraordinary risk for the mother.

Secondary structure and oligomerization behavior of equilibrium unfolding intermediates of the lambda cro repressor.

The thermal unfolding of the wild-type Cro repressor, its disulfide-bridged mutant Cro-V55C (with the Val-55 --> Cys single amino acid substitution), and a CNBr-fragment (13-66)2 of Cro-V55C was studied by Fourier transform infrared spectroscopy and dynamic light scattering. The combined approach reveals that thermal denaturation of Cro-WT and Cro-V55C proceeds in two steps through equilibrium unfolding intermediates. The first thermal transition of the Cro-V55C dimer involves the melting of the alpha-helices and the short beta-strand localized in the N-terminal part of the molecule. This event is accompanied by the formation of tetramers, and also impacts on the hydrogen-bonding interactions of the C-terminal beta-strands. The beta-sheet formed by the C-terminal parts of each polypeptide chain is the major structural feature of the intermediate state of Cro-V55C and unfolds during a second thermal transition, which is accompanied by the dissociation of the tetramers. Cutting of 12 amino acids in the N-terminal region is sufficient to prevent the formation of alpha-helical structure in the CNBr-fragment of Cro-V55C, and to induce tetramerization already at room temperature. The tetramers may persist over a broad temperature range, and start to dissociate only upon thermal unfolding of the beta-sheet structure formed by the C-terminal regions. The wild-type protein is a dimer at room temperature and at protein concentrations of 1.8-5.8 mg/mL. At lower concentrations, the dimers are stable until the onset of thermal unfolding, which is accompanied by the dissociation of the dimers into monomers. At higher protein concentrations, the unfolding is more complex and involves the formation of tetramers at intermediate temperatures. At these intermediate temperatures, the Cro-WT has lost all of its alpha-helical structure and also most of its native beta-sheet structure. Upon further temperature increase, a tendency for an intermolecular association of the beta-strands is observed, which may result in irreversible beta-aggregation at high protein concentrations.

Cooperative thermal transitions of bovine and human apo-alpha-lactalbumins: evidence for a new intermediate state.

The thermal denaturation of bovine and human apo-alpha-lactalbumins at neutral pH has been studied by intrinsic protein fluorescence, circular dichroism (CD), and differential scanning microcalorimetry (DSC) methods. Apo-alpha-lactalbumin possesses a thermal transition with a midpoint about 25-30 degrees C under these conditions (pH 8.1, 10 mM borate, 1 mM EGTA), which is reflected in changes in both fluorescence emission maximum and quantum yield. However, the CD showed a decrease in ellipticity at 270 nm with a midpoint at about 10-15 degrees C, while DSC shows the transition within the region of 15-20 degrees C. The non-coincidence of transition monitored by different methods suggests the existence of an intermediate state in the course of the thermal denaturation process. This intermediate state is not the classical molten globule state which occurs at higher temperature (i.e. denatured state at these conditions) [D.A. Dolgikh, R.I. Gilmanshin, E.V. Brazhnikov, V.E. Bychkova, G.V. Semisotnov, S.Y. Venyaminov and O.B. Ptitsyn, FEBS Letters, 136 (1981) 311-315] and has physical properties intermediate between the native and molten globule states.

[Nitric oxide: its role in the development of pregnancy complications and in their prevention in women with hypertension and chronic glomerulonephritis]. / Oksid azota: rol' v razvitii oslozhnenii beremennosti i v ikh profilaktike u zhenshchin s gipertonicheskoi bolezn'iu i khronicheskim glomerulonefritom.

The activity of NO-synthase and formation of NO (EDRF) were assessed by an increase in the activity of NO-dependent hyanilate cyclase in response to L-arginine in vitro in platelets of 61 pregnant females (39, 8 14 with essential hypertension, preeclampsia and healthy controls, respectively) and in 9 hypertensive nonpregnant females. Compared to healthy pregnant females, EDRF synthesis activity was inhibited in hypertensive gravidas but enhanced in preeclampsia patients. Effectiveness of exogenic donator NO (transdermal nitroglycerine, Nitroderm NNS 5) was studied in a randomised trial of 76 gravidas with essential hypertension (EH), EH and chronic glomerulonephritis (GN). 39 of them were given transdermal nitroglycerine, 37 received acetylsalicilic acid and curantil. The number of treatment failures was the same in both groups. The conclusion is made that nitro compounds are adequate for use in EH and chronic GN gravidas.

Study of tyrosine-containing mutants of ribosomal protein L7/L12 from Escherichia coli.

Three mutant forms of the ribosomal protein L7/L12 with replacements of Ser1, Met14 and Met26 to Tyr were studied by the methods of fluorescence spectroscopy, circular dichroism and microcalorimetry. The amino-acid residue Tyr14 in the protein L7/L12 Tyr14 is located in a region with a more organized structure than Tyr26 in protein L7/L12 Tyr26. The replacements Ser1-->Tyr1 and Met14-->Tyr14 do not affect the secondary structure of protein L7/L12. The replacement Met26-->Tyr26 stabilizes the secondary structure of protein L7/L12. A pH-induced temperature transition was observed in the pH range 5.0-7.3 in protein L7/L12 Tyr14 by tyrosine fluorescence. Analogous transitions were observed for protein L7/L12 Tyr26 by Tyr fluorescence and for the wild type protein L7/L12 by Phe fluorescence. Three pH-dependent states of protein L7/L12 and its mutant forms L7/L12 Tyr1 and L7/L12 Tyr14 were found on the microcalorimetric melting curves. The characteristics of protein L7/L12 Tyr14 are very close to the wild type protein L7/L12 and it is a suitable object for studying the structure of the N-terminal part of molecule by two-dimentional 1H-NMR.

Circularly permuted dihydrofolate reductase possesses all the properties of the molten globule state, but can resume functional tertiary structure by interaction with its ligands.

It is obvious that functional activity of a protein molecule is closely related to its structure. On the other hand, the understanding of structure-function relationship still remains one of the intriguing problems of molecular biology. There is widespread belief that mutagenesis presents a real way to solve this problem. Following this assumption, we have investigated the effect of circular permutation in dihydrofolate reductase from E. coli on protein structure and functioning. It has been shown that in the absence of ligands two circularly permuted variants of dihydrofolate reductase possess all the properties of the molten globule state. However, after addition of ligands they gain the native-like structural properties and specific activity. This means that the in vitro folding of permuted dihydrofolate reductase is terminated at the stage of the molten globule formation. Interaction of permuted protein with ligands leads to the structural adjustment and formation of active protein molecules.