Cis-trans isomerization in cyclosporin C dissolved in acetonitrile

Cyclosporin is an 11-amino acid cyclic peptide with pharmacologically valuable properties which has a variety of actual and potential applications. Its activity relies on the cell membrane permeability which, in turn, depends on the structure of cyclosporin and its ability to change the conformation. In this work, conformational exchange processes occurring in cyclosporin C were studied using one- and two-dimensional nuclear magnetic resonance spectroscopy. The free energy barrier separating two major conformers observed in polar solution (acetonitrile) was found to be 77 ± 2 kJ/mol. Less populated conformation states are also present in the solution, which agrees with the ease of formation of multiple forms revealed by MD simulations of cyclosporin C.

One-Step Synthesis of Functionalized Pyrazolo[3,4-b]pyridines via Ring Opening of the Pyrrolinium Ion

Herein, we report a highly regioselective one-pot synthesis of pyrazolo[3,4-b]pyridines via the reaction of 3-arylidene-1-pyrrolines with aminopyrazoles. The reaction proceeds through the sequential nucleophilic addition/electrophilic substitution/C-N bond cleavage and provides easy access to pyrazolo[3,4-b]pyridine derivatives featuring a primary amino group. Moreover, the reaction can be terminated at the electrophilic substitution stage, thus providing convenient entry to the hardly accessible pyrazolopyrrolopyridine scaffold.

Silicas with Polyoxyethylene Branches for Modification of Membranes Based on Microporous Block Copolymers

We have synthesized cubic and linear polysiloxanes containing polyoxyethylene branches (ASiP-Cu) using tetraethoxysilane, polyoxyethylene glycol, and copper chloride as precursors; the products are stable to self-condensation. The effect of copper chloride content on the chemical structure of ASiP-Cu has been established. A special study was aimed at defining the modifying effect of ASiP-Cu on the sorption characteristics of membranes based on microporous, optically transparent block copolymers (OBCs). These OBCs were produced using 2,4-toluene diisocyanate and block copolymers of ethylene and propylene oxides. The study demonstrated significantly increased sorption capacity of the modified polymers. On the basis of the modified microporous block copolymers and 1-(2-pyridylazo)-2-naphthol (PAN) analytical reagent, an analytical test system has been developed. Additionally, the modified OBCs have the benefit of high diffusion permeability for molecules of organic dyes and metal ions. It has been shown that the volume of voids and structural features of their internal cavities contribute to the complex formation reaction involving PAN and copper chloride.

Binding of Different Cyclosporin Variants to Micelles Evidenced by NMR and MD Simulations

Peptides play a critical role in the life of organisms, performing completely different functions. The biological activity of some peptides, such as cyclosporins, can be determined by the degree of membrane permeability. Thus, it becomes important to study how the molecule interacts with lipid bilayers. Cyclosporins C, E, H and L were characterised molecular dynamics simulation; NMR spectroscopy studies were also carried out for cyclosporins C and E. The comparison of one- and two-dimensional spectra revealed certain similarities between spatial structures of the studied cyclosporin variants. Upon dissolving in water containing DPC micelles, which serve as model membranes, subtle changes in the NMR spectra appear, but in a different way for different cyclosporins. In order to understand whether observed changes are related to any structural modifications, simulation of the interaction of the peptide with the phospholipid micelle was performed. The onset of the interaction was observed, when the peptide is trapped to the surface of the micelle. Simulations of this kind are also of interest in the light of the well-known membrane permeability of cyclosporin, which is important for its biological action.

Pervaporation Polyurethane Membranes Based on Hyperbranched Organoboron Polyols

On the basis of aminoethers of boric acid (AEBA), polyurethane vapor-permeable and pervaporative membranes were obtained. AEBAs, the structure of which is modified by bulk adducts (EM) of diphenylol propane diglycidyl ether and ethanolamine, were studied. It turned out that AEBA exists in the form of clusters, and the use of EM as a result of partial destruction of associative interactions leads to a significant decrease in the size of AEBA-EM particles and their viscosity compared to unmodified AEBA. The introduction of EM into the composition of AEBA leads to a threefold increase in the vapor permeability of polyurethanes obtained on their basis. The observed effect is explained by the fact that a decrease in the size of clusters leads to loosening of their dense packing. Areas of clustering due to associative interactions of hydroxyl groups, together with the hydrophilic nature of polyoxyethylene glycol, create channels through which water molecules can penetrate. The increase in vapor permeability is accompanied by a multiple increase in the permeability coefficients in the pervaporative dehydration of isopropanol.

The Role of Hidden Conformers in Determination of Conformational Preferences of Mefenamic Acid by NOESY Spectroscopy

Mefenamic acid has been used as a non-steroidal anti-inflammatory drug for a long time. However, its practical use is quite limited due to a number of side effects on the intestinal organs. Conformational polymorphism provides mefenamic acid with unique properties regarding possible modifications obtained during the micronization process, which can improve pharmacokinetics and minimize side effects. Micronization can be performed by decompression of supercritical fluids; methods such as rapid expansion of the supercritical solution have proven their efficiency. However, this group of methods is poorly applicable for compounds with low solubility, and the modification of the method using a pharmaceutically suitable co-solvent may be useful. In our case, addition of only 2 mol% dimethyl sulfoxide increased the solubility remarkably. Information on the conformational state may be critically important for carrying out micronization. In this work, structural analysis and estimate of conformational preferences of mefenamic acid in dimethyl sulfoxide-d6 (at 25 °C and 0.1 MPa) and in a mixed solvent supercritical carbon dioxide + dimethyl sulfoxide-d6 (45 °C, 9 MPa) were performed based on nuclear Overhauser effect spectroscopy. Results show changes in the conformation fractions depending on the medium used. The importance of allowing for hidden conformers in estimating the conformational state was demonstrated in the analysis. Obtained results may be useful for improving micronization parameters.

Comparison of structural properties of cyclosporin A and its analogue alisporivir and their effects on mitochondrial bioenergetics and membrane behavior

The paper considers the effect of the MPT pore inhibitor cyclosporin A (CsA) and its non-immunosuppressive analogue alisporivir (Ali) on the functioning of rat skeletal muscle mitochondria. We have shown that both agents at a standard in vitro concentration of 1 μM increase the calcium capacity of organelles and have no effect on the parameters of oxidative phosphorylation. However, an increase in their concentration to 5 μM leads to the suppression of oxygen consumption by mitochondria, which is more pronounced in the case of Ali. This effect is accompanied by a decrease in the membrane potential of organelles and, apparently, is based on the inhibition of electron transport along the mitochondrial respiratory chain due to limited mobility of coenzyme Q. We have noted that both agents do not affect the production of hydrogen peroxide by isolated mitochondria. NMR spectroscopy and molecular dynamics simulation did not reveal significant differences in the structure and backbone flexibility of CsA and Ali. Both agents decrease the overall fluidity of the membrane of DPPC liposomes, inducing an increase in laurdan generalized polarization parameter. A similar effect was also found in the case of mitochondrial membranes. We suggested that these effects of CsA and Ali, associated with their lipophilic nature and the ability to accumulate in the lipid phase of membranes, may cause a decrease in the efficiency of electron transport in the respiratory chain of mitochondria and suppression of the bioenergetics of these organelles.

Williams-Beuren Syndrome Related Methyltransferase WBSCR27: From Structure to Possible Function

Williams-Beuren syndrome (WBS) is a genetic disorder associated with the hemizygous deletion of several genes in chromosome 7, encoding 26 proteins. Malfunction of these proteins induce multisystemic failure in an organism. While biological functions of most proteins are more or less established, the one of methyltransferase WBSCR27 remains elusive. To find the substrate of methylation catalyzed by WBSCR27 we constructed mouse cell lines with a Wbscr27 gene knockout and studied the obtained cells using several molecular biology and mass spectrometry techniques. We attempted to pinpoint the methylation target among the RNAs and proteins, but in all cases neither a direct substrate has been identified nor the protein partners have been detected. To reveal the nature of the putative methylation substrate we determined the solution structure and studied the conformational dynamic properties of WBSCR27 in apo state and in complex with S-adenosyl-L-homocysteine (SAH). The protein core was found to form a canonical Rossman fold common for Class I methyltransferases. N-terminus of the protein and the β6–β7 loop were disordered in apo-form, but binding of SAH induced the transition of these fragments to a well-formed substrate binding site. Analyzing the structure of this binding site allows us to suggest potential substrates of WBSCR27 methylation to be probed in further research.

Design, Spectral Characteristics, Photostability, and Possibilities for Practical Application of BODIPY FL-Labeled Thioterpenoid

This paper presents the design and a comparative analysis of the structural and solvation factors on the spectral and biological properties of the BODIPY biomarker with a thioterpene fragment. Covalent binding of the thioterpene moiety to the butanoic acid residue of meso-substituted BODIPY was carried out to find out the membranotropic effect of conjugate to erythrocytes, and to assess the possibilities of its practical application in bioimaging. The molecular structure of the conjugate was confirmed via X-ray, UV/vis-, NMR-, and MS-spectra. It was found that dye demonstrates high photostability and high fluorescence quantum yield (to ~100%) at 514–519 nm. In addition, the marker was shown to effectively penetrate the erythrocytes membrane in the absence of erythrotoxicity. The conjugation of BODIPY with thioterpenoid is an excellent way to increase affinity dyes to biostructures, including blood components.

Conjugate of meso-carboxysubstituted-BODIPY with thioterpenoid as an effective fluorescent probe: Synthesis, structure, spectral characteristics, and molecular docking

This paper is devoted to the design of a fluorescent probe based on meso-carboxysubstituted-BODIPY with a thioterpene fragment. The functional replacement of the methoxy group in the BODIPY molecule on a thioterpene fragment was carried out in order to find out the antiplatelet and anticoagulant action mechanisms of thioterpenoids and to assess the membrane and receptor factors contributions. The molecular structure of the conjugate was confirmed via UV/vis-, NMR- and MS-spectra. It is found that the probe is a high fluorescence quantum yield (to ∼ 100%) in the blue-green region at 509-516 nm. Molecular docking of all studied molecules showed that the BODIPY with terpenoid conjugation is an excellent way to increase their affinity to platelet receptor P2Y₁₂.

Open-label use of an aliphatic polyamine immunomodulator in patients hospitalized with COVID-19

Background

Evidence-based therapies used to treat coronavirus disease (COVID-19) remain limited. Azoximer bromide (AZB; Polyoxidonium^®) is an immunomodulating molecule frequently used in the Russian Federation. It offers demonstrable therapeutic benefit in upper respiratory tract infections. This study evaluated the safety and efficacy of AZB when used in combination with standard of care treatment in patients hospitalized with COVID-19.

Methods

Hospitalized patients with COVID-19 (n=81; nine sites) received AZB 12 mg intravenously once daily for 3 days then intramuscularly every other day until day 17. The primary endpoint included clinical status at day 15 versus baseline. Historical control data of 100 patients from a randomized, controlled, open-label trial conducted in China were included to serve as a direct control group.

Results

Notable clinical improvement, assessed by seven-point ordinal scale (OS) score and National Early Warning Score, was observed. Mean duration of hospitalization was 19.3 days. Indicators of pneumonia and lung function showed gradual recovery to normalization. No patients died but, by day 28, one patient still required respiratory support; this patient died on day 34. A higher proportion of patients receiving AZB required invasive or non-invasive ventilation (OS 5 or 6) at baseline compared with the historical control group. Improvement in mean OS score by day 14/15 was not notable in the control group (OS 3.99–3.87) but was clear in the AZB group (OS 4.36–2.90). Mean duration of hospitalization was similar in the control group (16.0 days); however, day 28 mortality was higher, at 25.0% (n=25).

Conclusion

AZB combined with standard of care was safe and well tolerated. An apparent clinical improvement could not be fully evaluated due to the lack of a direct control group; further assessment of AZB for the treatment of COVID-19 in a randomized, placebo-controlled study is warranted.

Design, Spectral Characteristics, and Possibilities for Practical Application of BODIPY FL-Labeled Monoterpenoid

This article describes the design and biological properties of a BODIPY FL-labeled monoterpenoid BF₂-meso-(4-((1″R)-6″,6″-dimethylbicyclo[3.1.1]hept-2″-ene-2″)yl-methoxycarbonylpropyl)-3,3',5,5'-tetramethyl-2,2'-dipyrromethene conjugate (BODIPYmyrt). The fluorophore was characterized using X-ray, NMR, MS, and UV/vis spectroscopy. The conjugate exhibits a high quantum yield (to ∼100%) in the region 515-518 nm. BODIPYmyrt effectively penetrates the membranes of the bacterial and fungal cells and therefore can be used to examine the features of a broad spectrum of Gram-positive and Gram-negative bacteria and pathogenic fungi as well. Moreover, BODIPYmyrt exhibits a moderate tropism to the subcellular structures in mammalian cells (e.g., mitochondria), thereby providing an attractive scaffold for fluorophores to examine these particular organelles.

Corrigendum: The effect of azoximer bromide (Polyoxidonium®) in patients hospitalized with coronavirus disease (COVID-19): an open-label, multicentre, interventional clinical study

[This corrects the article DOI: 10.7573/dic.2020-11-1.].

The effect of azoximer bromide (Polyoxidonium®) in patients hospitalized with coronavirus disease (COVID-19): an open-label, multicentre, interventional clinical study

A clinical need for aetiotropic coronavirus disease (COVID-19) treatments is required. The immune modulator azoximer bromide (AZB; Polyoxidonium®) is indicated in Russia for use against acute viral infections and during remission. In this study, adults hospitalized with COVID-19 (n=32) received AZB and standard of care in an open-label, multicentre, interventional study. All patients were symptomatic; 22 had severe disease (National Early Warning Score ≥5) and required mechanical ventilation or oxygen saturation (SpO₂) and 19 patients had co-morbidities. Patients received AZB 12 mg intravenously once daily for 3 days, then intramuscularly every other day (approximately ten injections) until discharge. The primary endpoint was the patient's clinical status (7-point Ordinal Scale; OS) on day 15 versus that at baseline. The mean duration of hospitalization was 20 days. All patients were alive and discharged with normal SpO₂ with no secondary infections or delayed mortality reported by the end-of-study visit (on day 28-72). A decrease in the mean OS and National Early Warning Score values was observed following treatment with AZB. A decrease in OS score was marked in patients identified as severe. Both sets of patients achieved similar scores, which can be classified as an improvement by day 9-10; SpO₂ levels trended to normalization over time. By day 11-12, all patients had a normal body temperature. Serum C-reactive protein levels decreased in patients with severe and mild disease. Most patients had signs of pneumonia at baseline (n=27), with the majority recovering by days 10-12. No major toxicities were observed. AZB was safe and well tolerated when administered in addition to standard of care treatment for COVID-19. Further randomized, placebo-controlled studies are needed to elucidate any potential therapeutic effect in COVID-19.

Backbone resonance assignment and dynamics of 110 kDa hexameric inorganic pyrophosphatase from Mycobacterium tuberculosis

Family I soluble inorganic pyrophosphatases (PPases; EC 3.6.1.1) are enzymes essential for all organisms. They hydrolyze inorganic pyrophosphate, thus providing the driving force for numerous biosynthetic reactions. Soluble PPases retain enzymatic activity only in multimeric forms. PPases from various organisms are extensively studied by X-ray crystallography but until now there was no information on their structure and dynamics in solution. Hexameric 110 kDa (6 × 18.3 kDa) PPase from Mycobacterium tuberculosis (Mt-PPase) is a promising target for the rational design of potential anti-tuberculosis agents. In order to use NMR techniques in functional studies of Mt-PPase and rational design of the inhibitors for this enzyme, it is necessary to have information on the backbone ¹H, ¹³C and ¹⁵N resonance assignments. Samples of Mt-PPase enriched with 99% of ¹³C and ¹⁵N isotopes, and 95% of ²H were obtained using recombinant protein expression in an isotopically-labeled medium and effective heat-shock protocol for the deuterium-to-hydrogen exchange of the amide groups. Backbone resonance assignment was achieved for more than 95% of the residues. It was found that the secondary structure of Mt-PPase in solution corresponds well to the crystal structure of this protein. Protein backbone dynamics were studied using ¹⁵N NMR relaxation experiments. Determined resonance assignments and dynamic properties provide the basis for the subsequent structure-based design of novel inhibitors of Mt-PPase-potential anti-tuberculosis drugs.

Williams-Beuren syndrome-related methyltransferase WBSCR27: cofactor binding and cleavage

Williams-Beuren syndrome, characterized by numerous physiological and mental problems, is caused by the heterozygous deletion of chromosome region 7q11.23, which results in the disappearance of 26 protein-coding genes. Protein WBSCR27 is a product of one of these genes whose biological function has not yet been established and for which structural information has been absent until now. Using NMR, we investigated the structural and functional properties of murine WBSCR27. For protein in the apo form and in a complex with S-(5'-adenosyl)-l-homocysteine (SAH), a complete NMR resonance assignment has been obtained and the secondary structure has been determined. This information allows us to attribute WBSCR27 to Class I methyltransferases. The interaction of WBSCR27 with the cofactor S-(5'-adenosyl)-l-methionine (SAM) and its metabolic products - SAH, 5'-deoxy-5'-methylthioadenosine (MTA) and 5'-deoxyadenosine (5'dAdo) - was studied by NMR and isothermal titration calorimetry. SAH binds WBSCR27 much tighter than SAM, leaving open the question of cofactor turnover in the methylation reaction. One possible answer to this question is the presence of weak but detectable nucleosidase activity for WBSCR27. We found that the enzyme catalyses the cleavage of the adenine moiety from SAH, MTA and 5'dAdo, similar to the action of bacterial SAH/MTA nucleosidases. We also found that the binding of SAM or SAH causes a significant change in the structure of WBSCR27 and in the conformational mobility of the protein fragments, which can be attributed to the substrate recognition site. This indicates that the binding of the cofactor modulates the folding of the substrate-recognizing region of the enzyme.

Structure and function of the N-terminal domain of the yeast telomerase reverse transcriptase

The elongation of single-stranded DNA repeats at the 3′-ends of chromosomes by telomerase is a key process in maintaining genome integrity in eukaryotes. Abnormal activation of telomerase leads to uncontrolled cell division, whereas its down-regulation is attributed to ageing and several pathologies related to early cell death. Telomerase function is based on the dynamic interactions of its catalytic subunit (TERT) with nucleic acids—telomerase RNA, telomeric DNA and the DNA/RNA heteroduplex. Here, we present the crystallographic and NMR structures of the N-terminal (TEN) domain of TERT from the thermotolerant yeast Hansenula polymorpha and demonstrate the structural conservation of the core motif in evolutionarily divergent organisms. We identify the TEN residues that are involved in interactions with the telomerase RNA and in the recognition of the ‘fork’ at the distal end of the DNA product/RNA template heteroduplex. We propose that the TEN domain assists telomerase biological function and is involved in restricting the size of the heteroduplex during telomere repeat synthesis.

Polyurethane ionomers based on amino ethers of ortho-phosphoric acid

The etherification of ortho-phosphoric acid with triethanolamine and polyoxypropylene glycol is studied. The reaction process is accompanied by the formation of hyperbranched amino ethers of ortho-phosphoric acid terminated by hydroxyl groups. A specific feature of the chemical structure of the compounds obtained is the existence of ion pairs in their structure separated in space. The reaction of the etherification of ortho-phosphoric acid with glycols becomes possible through the use of tertiary amines. The amino ethers of ortho-phosphoric acid are investigated as a polyol component for the synthesis of polyurethanes with high adhesion characteristics and strength properties. The experimental results presented allow us to relate polyurethanes obtained on the basis of ortho-phosphoric acid amino ethers to polymers of ionomeric nature.

The etherification of ortho-phosphoric acid with triethanolamine and polyoxypropylene glycol is studied.

Complete plastome sequence of Paeonia lactiflora Pall. (Paeoniaceae: Saxifragales)

Paeonia lactiflora has been listed as an Endangered species in Russian Federation. The complete plastome was assembled from Next-Generation Sequencing data. It is 152,747 bp in length. It consists of a pair of Inverted Repeat regions (25,651 bp), separated by a small single copy region of 17,033 bp and a large single copy region of 84,412 bp. The plastome encoded 128 genes, including 83 protein coding genes, 37 tRNA, eight rRNA genes, four pseudogenes, and is characterized by loss of the rpl32 and infA genes. Phylogenetic analysis of Paeoniaceae plastomes revealed that P. lactiflora clustered with Eurasian peonies (section Paeoniae).

NMR assignments of the WBSCR27 protein related to Williams-Beuren syndrome

Williams-Beuren syndrome is a genetic disorder characterized by physiological and mental abnormalities, and is caused by hemizygous deletion of several genes in chromosome 7. One of the removed genes encodes the WBSCR27 protein. Bioinformatic analysis of the sequence of WBSCR27 indicates that it belongs to the family of SAM-dependent methyltransferases. However, exact cellular functions of this protein or phenotypic consequences of its deficiency are still unknown. Here we report nearly complete ¹H, ¹⁵N, and ¹³C chemical shifts assignments of the 26 kDa WBSCR27 protein from Mus musculus in complex with the cofactor S-adenosyl-L-methionine (SAM). Analysis of the assigned chemical shifts allowed us to characterize the protein's secondary structure and backbone dynamics. The topology of the protein's fold confirms the assumption that the WBSCR27 protein belongs to the family of class I methyltransferases.

Evidence of oligomerization of bovine insulin in solution given by NMR

The protein hormone insulin exists in several forms in nature, and a large number of modified sequences are used in pharmacy. They differ by physicochemical properties and efficiency of biological action. Pancreatic bovine insulin was studied in an acidic solution by nuclear magnetic resonance spectroscopy. [Formula: see text]H and [Formula: see text]C NMR signal assignment of backbone and side chains was made by analysis of a set of 2D spectra obtained on a sample with natural isotope abundance. The presence of certain secondary structure elements was revealed on a qualitative level based on nuclear Overhauser effect spectroscopy, which are similar to those observed in the crystal structure. The C-terminus of the B-chain possessed a remarkable flexibility. The molecule was shown to exist in exchange with oligomers based on its self-diffusion coefficient and correlation time measurements performed at different concentrations. Certain signals in the NOESY and HSQC spectra are consistent with the presence of minor conformers; this is an obstacle in simulating the molecular structure under the conditions used in the experiment.

Chemical shift assignments and the secondary structure of the Est3 telomerase subunit in the yeast Hansenula polymorpha

Telomerase is a multisubunit ribonucleoprotein enzyme that is essential for continuous cellular proliferation. A key role of telomerase in cancer and ageing makes it a promising target for the development of cancer therapies and treatments of other age-associated diseases, since telomerase allows unlimited proliferation potential of cells in the majority of cancer types. However, the structure and molecular mechanism of telomerase action are still poorly understood. In budding yeast, telomerase consists of the catalytic subunit, the telomerase reverse transcriptase or Est2 protein, telomerase RNA (TLC1) and two regulatory subunits, Est1 and Est3. Each of the four subunits is essential for in vivo telomerase function. Est3 interacts directly with Est1 and Est2, and stimulates Est2 catalytic activity. However, the exact role of the Est3 protein in telomerase function is still unknown. Determination of the structure, dynamic and functional properties of Est3 can bring new insights into the molecular mechanism of telomerase activity. Here we report nearly complete ¹H, ¹³C and ¹⁵N resonance assignments of Est3 from the yeast Hansenula polymorpha. Analysis of the assigned chemical shifts allowed us to identify the protein's secondary structure and backbone dynamic properties. Structure-based sequence alignment revealed similarities in the structural organization of yeast Est3 and mammalian TPP1 proteins.

Tandem dihetero-Diels–Alder and Huisgen cycloaddition reactions. Synthesis, crystal structure and hydrolysis of the novel cage phosphoranes

The reaction of 2-(1-phenylvinyloxy)benzo-1,3,2-dioxaphosphole with activated carbonyl compounds leads to the stereoselective formation of cage phosphoranes.

Stereoselective PCO/POC-Rearrangement of P-C-Cage Phosphorane in the Reaction of 4,5-Dimethyl-2-(2-oxo-1,2-diphenyl)ethoxy-1,3,2-dioxaphospholane with Hexafluoroacetone

Interaction of 4,5-dimethyl-2-(2-oxo-1,2-diphenyl)ethoxy-1,3,2-dioxaphospholane, bearing a carboxyl group in the γ-position with respect to the phosphorus atom and obtained from d,l-butanediol, with hexafluoroacetone (CCl4, -40 °C) leads to the simultaneous formation of regio- and stereoisomeric cage-like phosphoranes with phosphorus-carbon and phosphorus-oxygen bonds with a high stereoselectivity (>95%), whose structure was determined by 1D and 2D NMR spectroscopy and XRD. When stored as a solution in dichloromethane for one month, the PCO-isomer rearranges into the thermodynamically more stable POC-isomer of the cage-like phosphorane. Mild hydrolysis of the PCO/POC-isomers proceeds with a high chemoselectivity and leads to the formation of P(IV)-dioxaphospholane derivatives. Acidic hydrolysis of the POC-isomer leads to the formation of an oxirane derivative with an unexpectedly high stereoselectivity (>95%). DFT calculations (using the PBE functional) allowed us to obtain structures and energies of the initial phospholane, reaction products (PCO/POC-isomers), and an intermediate P(V)-oxaphosphirane.

NMR assignments of the N-terminal domain of Ogataea polymorpha telomerase reverse transcriptase

Telomerase is a ribonucleoprotein enzyme that adds telomeric DNA fragments to the ends of chromosomes. This enzyme is the focus of substantial attention, both because its structure and mechanism of action are still poorly studied, and because of its pivotal roles in aging and cellular proliferation. The use of telomerase as a potential target for the design of new anticancer drugs is also of great interest. The catalytic protein subunit of telomerase (TERT) contains an N-terminal domain (TEN) that is essential for activity and processivity. Elucidation of the structure and dynamics of TEN in solution is important for understanding the molecular mechanism of telomerase activity and for the design of new telomerase inhibitors. To approach this problem, in this study we report the (1)H, (13)C, and (15)N chemical shift assignments of TEN from Ogataea polymorpha. Analysis of the assigned chemical shifts allowed us to identify secondary structures and protein regions potentially involved in interaction with other participants of the telomerase catalytic cycle.

Antimicrobial peptide protegrin-3 adopt an antiparallel dimer in the presence of DPC micelles: a high-resolution NMR study

A tendency to dimerize in the presence of lipids was found for the protegrin. The dimer formation by the protegrin-1 (PG-1) is the first step for further oligomeric membrane pore formation. Generally there are two distinct model of PG-1 dimerization in either a parallel or antiparallel β-sheet. But despite the wealth of data available today, protegrin dimer structure and pore formation is still not completely understood. In order to investigate a more detailed dimerization process of PG-1 and if it will be the same for another type of protegrins, in this work we used a high-resolution NMR spectroscopy for structure determination of protegrin-3 (RGGGL-CYCRR-RFCVC-VGR) in the presence of perdeuterated DPC micelles and demonstrate that PG-3 forms an antiparallel NCCN dimer with a possible association of these dimers. This structural study complements previously published solution, solid state and computational studies of PG-1 in various environments and validate the potential of mean force simulations of PG-1 dimers and association of dimers to form octameric or decameric β-barrels.

High-resolution NMR structure of the antimicrobial peptide protegrin-2 in the presence of DPC micelles

PG-1 adopts a dimeric structure in dodecylphosphocholine (DPC) micelles, and a channel is formed by the association of several dimers but the molecular mechanisms of the membrane damage by non-α-helical peptides are still unknown. The formation of the PG-1 dimer is important for pore formation in the lipid bilayer, since the dimer can be regarded as the primary unit for assembly into the ordered aggregates. It was supposed that only 12 residues (RGGRL-CYCRR-RFCVC-V) are needed to endow protegrin molecules with strong antibacterial activity and that at least four additional residues are needed to add potent antifungal properties. Thus, the 16-residue protegrin (PG-2) represents the minimal structure needed for broad-spectrum antimicrobial activity encompassing bacteria and fungi. As the peptide conformation and peptide-to-membrane binding properties are very sensitive to single amino acid substitutions, the solution structure of PG-2 in solution and in a membrane mimicking environment are crucial. In order to find evidence if the oligomerization state of PG-1 in a lipid environment will be the same or not for another protegrins, we investigate in the present work the PG-2 NMR solution structure in the presence of perdeuterated DPC micelles. The NMR study reported in the present work indicates that PG-2 form a well-defined structure (PDB: 2MUH) composed of a two-stranded antiparallel β-sheet when it binds to DPC micelles.

[Unusual alternations of floral organs in Paeonia: structure and possible mechanism of formation]

Morphological analysis of flowers was carried out in Paeonia cultivars. Some unusual alternations of floral organs were described: sepal-(petal-stamen) x N-carpel, where 2 < or = n < or = 4 (appearance of an additional zone of petal and stamen formation in the medial flower part). The identity of floral organs was not affected in the flowers with this unusual alternation. It was shown on the basis of mathematical simulation of the genes responsible for flower development that these alternations may be determined by increased pool of stem cells, which may lead to delayed termination of flower development.

[The characteristics of the corticosteroid receptors in the hormonal modification of the stress reactivity of rats]

After neonatal administration of hydrocortisone the rat litter preserve inhibition of function of the hypophyseal-adrenal system at the age under 2 months. During the inhibition period, the number of corticosteroid receptors was decreased in the hypothalamus and hippocampus and increased in the hypophysis. At the 3-month age, binding of corticosteroids in these structures is restored.

[The evaluation of corticosteroid hormone receptor status in the brain structures of stressed and adrenalectomized rats]

The value of receptor capacity in respect to cytosol concentration was shown to vary, therefore two criteria are proposed for estimation of condition of the cytosol corticosteroid receptors: the density of the receptors in tissue and the range of intermediate (active) complex. The number of receptors in the hypophysis was shown to reduce after adrenalectomy whereas in the hypothalamus, hippocampus and striatum it increased. The range of intermediate complex was shown to change differently in different structures after stress.

[The properties of the glucocorticoid receptors in the striatum and hypothalamus of rats selected for the threshold of excitability of their nervous systems]

In rats selected by their threshold sensitivity to electrical current, linear differences were found both at the receptor level and in stress-reactivity, the receptor lability being very high in the rats highly sensitive to electricity. The lower sensitivity rats were found to be more conservative in these parameters. The role of the hypothalamus and striatum in regulation of the hypophyseal-adrenocortical system through a feed-back mechanism, is discussed.

[The kinetic characteristics and stoichiometry of corticosterone interaction with cytosol receptors]

The interaction of molybdate-stabilised cytosol receptor of the rat brain and liver with corticosterone was studied in conditions of equilibrium and non-equilibrium in vitro. The hormone-receptors complexes with varying number of the receptor molecules were found to form consequentially. During their formation the complexes revealed the properties of disperse phases. The concentration of the receptors seems to be one of the regulating factors of activity of the complexes. An original experimental technique is described.

[The dynamics of the microbiocenosis in the burrows of the little suslik]

Microbiocoenoses being formed in burrows of little souslik have been investigated. Microbiocoenoses of sloping burrows have most simple organization. Comparative analysis of the fauna and functional structure, conducted during the spring-summer period, has not shown the existence of any directed process in the development of microbiocoenoses of sloping burrows. On the contrary, microbiocoenoses of vertical nest burrows can be regarded as biocoenotic systems dynamic in space and time. Here in the period of rodent's vital activity occurs a constant construction of underground passages and periodical change of nests. In this case the fauna of new nests is formed largely at the expense of migration of nidicols along free or obstructed with loose earth underground horizontal passages. Microbiocoenoses in burrows of different types are not connected between each other by morphoprocess and their development is of independent character.