Stereochemical and Computational NMR Survey of 1,2,3-Triazoles: in Search of the Original Tauto-Conformers

The conformational analysis of nine functionalized 1,2,3-triazoles was carried out by the correlation of calculated and experimental high-level nuclear magnetic resonance (NMR) chemical shifts. In solution, the studied triazoles are in exchange dynamic equilibrium caused by their prototropic tautomerism of the NH-proton. The experimentally unresolved NMR signals were assigned for most of the compounds. A more thorough survey was conducted for 4-t-butyl-1,2,3-triazole-5-carbaldehyde oxime. The analysis performed within the framework of the DP4+ formalism completely confirmed the hypothesis of the predominance of the 2H-tautomer. Thus, the methodology for estimating stereochemical structures in the absence of some experimental data allowed the most stable conformations for dynamic systems with different tautomeric ratios to be reliably identified.

On the Efficiency of the Density Functional Theory (DFT)-Based Computational Protocol for 1H and 13C Nuclear Magnetic Resonance (NMR) Chemical Shifts of Natural Products: Studying the Accuracy of the pecS-n (n = 1, 2) Basis Sets

The basis set issue has always been one of the most important factors of accuracy in the quantum chemical calculations of NMR chemical shifts. In a previous paper, we developed new pecS-n (n = 1, 2) basis sets purposed for the calculations of the NMR chemical shifts of the nuclei of the most popular NMR-active isotopes of 1-2 row elements and successfully approbated these on the DFT calculations of chemical shifts in a limited series of small molecules. In this paper, we demonstrate the performance of the pecS-n (n = 1, 2) basis sets on the calculations of as much as 713 1H and 767 13C chemical shifts of 23 biologically active natural products with complicated stereochemical structures, carried out using the GIAO-DFT(PBE0) approach. We also proposed new alternative contraction schemes for our basis sets characterized by less contraction depth of the p-shell. New contraction coefficients have been optimized with the property-energy consistent (PEC) method. The accuracies of the pecS-n (n = 1, 2) basis sets of both the original and newly contracted forms were assessed on massive benchmark calculations of proton and carbon chemical shifts of a vast variety of natural products. It was found that less contracted pecS-n (n = 1, 2) basis sets provide no noticeable improvement in accuracy. These calculations represent the most austere test of our basis sets as applied to routine calculations of the NMR chemical shifts of real-life compounds.

Computational studies of [1]benzothieno[2,3-c]naphtho[1,2-f]quinoline

Early NMR studies of several heterohelicenes containing an annular nitrogen atom and a thiophene ring in their structure suggested the possibility of the lengthening of the carbon-carbon bonds in the interior of the helical turn of the molecule based on the progressive more shielded nature of ¹³ C resonances toward the center of the helical turn. Computational chemistry capabilities when those NMR studies were performed were primitive in comparison to what is now possible. We now report the optimized geometry and a comparison of the calculated versus observed ¹ H and ¹³ C NMR chemical shift assignments for [1]benzothieno[2,3-c]naphtho[1,2-f]quinoline that confirms these suspicions.

Reactions of α-Functionally Substituted Enals with Terminal Alkynes: Unexpected Assembly of 2-Amino-2-Cyclopentenones

The reactions of α-chalcogen, α-halo, or α-amino functionally substituted enals with terminal alkynes leading either to corresponding propargyl alcohols (for O-, S-, Cl-, and Br-bearing substrates) or unexpected 2-amino-2-cyclopentenones (for aminoenals) are described. The key feature of these reactions is the rearrangement of adducts bearing amino groups on silica gel that triggered further cyclization to five-membered carbocycles.

Stereochemical Study of the Super Large Tetrakis Alkaloid Alasmontamine A by Means of an Advanced Computational NMR

1H and 13C NMR chemical shifts of the tetrakis monoterpene indole alkaloid alasmontamine A, with a molecular formula of C84H91N8O12, have been calculated within the DFT framework. Six minimum energy conformers of this alkaloid were identified, and three key configurations that contribute to its NMR shielding constants were established. Several ambiguities in the reported assignment of the NMR chemical shifts of alasmontamine A have been resolved.

Computational NMR of natural products: On the way to super large molecules exemplified with alasmontamine A

¹ H and ¹³ C nuclear magnetic resonance (NMR) chemical shifts of a tetrakis monoterpene indole alkaloid alasmontamine A with a molecular formula of C₈₄ H₉₁ N₈ O₁₂ have been calculated at the PBE0/pcSseg-2//pcseg-2 level of theory on M06-2X/aug-cc-pVDZ geometry. In the course of the preliminary conformational search, six true minimum energy conformers were identified that can contribute to the actual conformation of this huge alkaloid. Calculated chemical shifts generally demonstrated a good agreement with available experimental data characterized with a corrected mean absolute error of 0.10 ppm for the range of about 7 ppm for protons and 1.1 ppm for the range of about 160 ppm for carbons.

Four-component relativistic calculations of NMR shielding constants of the transition metal complexes. Part 1: Pentaammines of cobalt, rhodium, and iridium

The nonrelativistic and four-component fully relativistic calculations of ¹ H, ¹⁵ N, ⁵⁹ Co, ¹⁰³ Rh, and ¹⁹³ Ir shielding constants of pentaammineaquacomplexes of cobalt(III), rhodium(III), and iridium(III) were carried out at the density functional theory (DFT) level of theory. The noticeable deshielding relativistic corrections were observed for nitrogen shielding constants (chemical shifts), whereas those corrections were found to be negligible for protons. For the transition metals cobalt, rhodium, and iridium, relativistic corrections to their nuclear magnetic resonance (NMR) shielding constants were found to be rather small for cobalt and rhodium (some 5-10%), whereas they are essentially larger for iridium (up to 70%).

Combined Computational NMR and Molecular Docking Scrutiny of Potential Natural SARS-CoV-2 Mpro Inhibitors

In continuation of the search for potential drugs that inhibit the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), in this work, a combined approach based on the modeling of NMR chemical shifts and molecular docking is suggested to identify the possible suppressors of the main protease of this virus among a number of natural products of diverse nature. Primarily, with the aid of an artificial neural network, the problem of the reliable determination of the stereochemical structure of a number of studied compounds was solved. Complementary to the main goal of this study, theoretical modeling of NMR spectral parameters made it feasible to perform a number of signal reassignments together with introducing some missing NMR data. Finally, molecular docking formalism was applied to the analysis of several natural products that could be chosen as prospective candidates for the role of potential inhibitors of the main protease. The results of this study are believed to assist in further research aimed at the development of specific drugs based on the natural products against COVID-19.

Digitization of the electron shell via the localized orbital locator formalism: trends in the size and electronegativity changes of atoms across the periodic table

The parameters of the (3,−3) critical point in the topology of the localized orbital locator inside the electron shell reflect regularity in the change of basic atom properties across the periodic table.

Simple and Versatile Scheme for the Stereochemical Identification of Natural Products and Diverse Organic Compounds with Multiple Asymmetric Centers

A simple and versatile scheme of stereochemical identification of the stereochemically rich natural products and organic compounds with multiple asymmetric centers is proposed based on a detailed parsing of calculated ¹H and ¹³C NMR chemical shifts in combination with their DP4+ analysis, as exemplified for three natural products: sungucine, physalin D, and anabsinthin. Performed benchmark calculations of the considered diastereomers provided very good agreement with their known experimental stereochemical structures.

Localized orbital locator as a descriptor for quantification and digital presentation of lone pairs: benchmark calculations of 4-substituted pyridines

The parameters of the (3,-3) critical point in the localized orbital locator topology near a heteroatom have been found to reflect the changes in the size, density and electron energy of the lone pair and correlate with the donor ability of the lone pair carrying heteroatom.

Computational 1 H and 13 C NMR of the trimeric monoterpenoid indole alkaloid strychnohexamine: Selected spectral updates

Very large trimeric indole alkaloid strychnohexamine, with empirical formula C₅₉ H₆₀ N₆ O (66 second-row atoms and 60 protons), has been subjected to the state-of-the-art computation of the ¹ H and ¹³ C nuclear magnetic resonance (NMR) chemical shifts of its configurational isomers at each of the 14 asymmetric centers. Several spectral reassignments and corrections of ¹ H and ¹³ C NMR spectra of this alkaloid were suggested based on the PBE0/pcSseg-2//pcseg-2 calculation of its NMR chemical shifts. Thus, all pairs of diastereotopic protons were assigned together with four aromatic carbon resonances of C-9 and C-11, C-9″, and C-11″. In addition, the unassigned chemical shifts of carbon C-23″ and proton at C-3' in, accordingly, ¹³ C and ¹ H NMR spectra were predicted.

Surface characterization and biological assessment of corrosion-resistant a-C:H:SiOx PACVD coating for Ti-6Al-4V alloy

The paper focuses on the SiO_x-doped amorphous hydrocarbon (a-C:H:SiO_x) coating on the titanium (Ti-6Al-4V) alloy substrate obtained by plasma-assisted chemical vapor deposition (PACVD) in a mixture of argon gas and polyphenylmethylsiloxane vapor using a bipolar substrate bias. It is shown that the a-C:H:SiO_x coating deposition results in the formation of a negative surface potential important for application of this coating for medical implants. The a-C:H:SiO_x coatings improve the corrosion resistance of Ti alloy to 0.5 M NaCl solution and phosphate-buffered saline. In particular, the corrosion current density of the a-C:H:SiO_x-coated sample in a 0.5 M NaCl solution at 22 °C decreases from 1∙10^-8 to 1.7∙10^-10 A/cm², that reduces the corrosion rate from 9∙10^-5 to 15∙10^-7 mm/year. The a-C:H:SiO_x coating facilitates the surface endothelization of an implant located in the thoracic aorta of a mini pig, and reduces the risk of thrombosis and implant failure. This effect can be explained by the ability of the a-C:H:SiO_x coating ability to reduce in vitro a 24-hour secretion of pro-inflammatory interleukins (IL-6, IL-12(p70), IL-15, and IL-17) and cytokines (IFN-g and TNF-a) by blood mononuclear cells (MNCs) and elevates the concentration of anti-inflammatory interleukin IL-1Ra. In vitro analysis shows no cytotoxicity of the a-C:H:SiO_x coating for the human blood MNCs, suggesting a promising PACVD on Ti alloys for cardiovascular implants, including pumps for mechanical heart support systems.

Computational 1H and 13C NMR of strychnobaillonine: On the way to larger molecules calculated at lower computational costs

The ¹H and ¹³C NMR chemical shifts of strychnobaillonine, a very large dimeric indole alkaloid, consisting of as many as 46 nonhydrogen atoms, were calculated with using the established earlier the most effective computational protocol, PBE0/pcSseg-2//pcseg-2. A very good result was achieved at this level, characterized by the root mean square deviation of only 0.14 ppm for protons and 2.4 ppm for carbons, which enabled the verification of the configurations of its all 13 asymmetrical centers. Essential deviations of the calculated and experimental ¹H NMR spectrum of strychnobaillonine were established in several cases, which enabled the performance of some additional NMR assignments and reassignments of the originally proposed structure.

[Choice of neuroprotective therapy regimens in patients with chronic cerebral ischemia, taking into account the synergy of drug interactions]

OBJECTIVE

Optimization of the choice of neuroprotective treatment regimens in patients with chronic cerebral ischemia that takes into account the synergy of drug interactions gives the doctor an opportunity for personalized approach that increases the effectiveness of treatment.

MATERIAL AND METHODS

Differential chemoreactomic analysis of the synergism of ethyl methyl hydroxypyridine succinate (EMHPS) and a number of monocomponent neuroprotective agents (piracetam, vinpocetine, citicoline, choline alfoscerate); proteomic analysis of polypeptide neuroprotectors (cerebrolysin, etc.); an expert analysis of multicomponent neuroprotector Cytoflavin.

RESULTS

Piracetam, citicoline (Neupilept) and choline alfoscerate (Cereton) effectively enhance the pharmacological properties of EMHPS and vice versa. Expert assessments of the synergism between the properties of EMHPS, polypeptide neuroprotectors (cerebrolysin) and other multicomponent drugs (cytoflavin), which are also used in adjuvant therapy with EMHPS, are presented.

CONCLUSION

In real clinical practice, of particular interest is the objectification of the appointment of combined therapy regimens. This study indicates that EMHPS can provide a favorable background for maximizing the effectiveness of therapy when used with other drugs.

The 1 H and 13 C NMR chemical shifts of Strychnos alkaloids revisited at the DFT level

The density functional theory calculation of ¹ H and ¹³ C NMR chemical shifts in a series of ten 10 classically known Strychnos alkaloids with a strychnine skeleton was performed at the PBE0/pcSseg-2//pcseg-2 level. It was found that calculated ¹ H and ¹³ C NMR chemical shifts provided a markedly good correlation with experiment characterized by a mean absolute error of 0.08 ppm in the range of 7 ppm for protons and 1.67 ppm in the range of 150 ppm for carbons, so that a mean absolute percentage error was as small as ~1% in both cases.

DFT computational schemes for 1 H and 13 C NMR chemical shifts of natural products, exemplified by strychnine

A number of computational schemes based on different Density Functional Theory (DFT) functionals in combination with a number of basis sets were tested in the calculation of ¹ H and ¹³ C NMR chemical shifts of strychnine, as a typical representative of the vitally important natural products, and used as a challenging benchmark and a rigorous test for such calculations. It was found that the most accurate computational scheme, as compared with experiment, was PBE0/pcSseg-4//pcseg-3 characterized by a mean absolute error of 0.07 ppm for the range of about 7 ppm for ¹ H NMR chemical shifts and that of only 1.13 ppm for ¹³ C NMR chemical shifts spread over the range of about 150 ppm. For more practical purposes, including investigation of larger molecules from this series, a much more economical computational scheme, PBE0/pcSseg-2//pcseg-2, characterized by almost the same accuracy and much less computational demand, was recommended.

Calculation of 15N NMR Chemical Shifts in a Diversity of Nitrogen-Containing Compounds Using Composite Method Approximation at the DFT, MP2, and CCSD Levels

Computations of ¹⁵N NMR chemical shifts in 93 diverse nitrogen-containing compounds representing almost all known classes are performed at the density functional theory (DFT), second-order Møller-Plesset perturbation theory (MP2), and coupled cluster singles and doubles (CCSD) levels using the composite method approximation (CMA) in comparison with experimental results. It is shown that the CMA-DFT and CMA-CCSD methods provided the best performance characterized by a normalized mean absolute error of 1.1-1.3% as compared to 2.3% for the CMA-MP2 results. Taking into account solvent effects within the conductor-like polarizable continuum model decreased the normalized mean absolute error by 0.4% for the CMA-DFT and by 0.2% for the CMA-CCSD calculations.

DFT computational schemes for 15 N NMR chemical shifts of the condensed nitrogen-containing heterocycles

A systematic density functional theory (DFT) study of the accuracy factors (functionals, basis sets, and solvent effects) for the computation of ¹⁵ N NMR chemical shifts has been performed in the series of condensed nitrogen-containing heterocycles. The behavior of the most representative functionals was examined based on the benchmark calculations of ¹⁵ N NMR chemical shifts in the reference set of compounds. It was found that the best agreement with experiment was achieved with OLYP functional in combination with aug-pcS-3(N)//pc-2 locally dense basis set scheme providing mean absolute error of 5.2 ppm in the range of about 300 ppm. Taking into account solvent effects was performed within a general Tomasi's polarizable continuum model scheme. It was also found that computationally demanding supermolecular solvation model computations essentially improved some "difficult" cases, as was illustrated with phenanthroline dissolved in methanol. Based on the performed calculations, some 200 unknown ¹⁵ N NMR chemical shifts were predicted with a high level of confidence for about 50 real-life condensed nitrogen-containing heterocycles, which could serve as a practical guide in structural elucidation of this class of compounds.

[Experience with mexidol in neurological practice]

Antihypoxic, antioxidant and nootropic effects of mexidol contribute to the improvement of patients with cerebrovascular pathology. The results of clinical studies show that the sequential scheme of using mexidol (first i.v. or i.m., then per os) is effective in the complex therapy of ischemic diseases of the brain, vascular surgery, therapy and rehabilitation of patients with degenerative-dystrophic changes of the spine, treatment of neurodegenerative pathology (including multiple sclerosis, Parkinson's disease and diabetic polyneuropathy), infectious neuropathies (ARVI, herpes, tick-borne encephalitis), neuropsychological and autonomic disorders.

Deficit of Magnesium and States of Hypercoagulation: Intellectual Analysis of Data Obtained From a Sample of Patients Aged 18-50 years From Medical and Preventive Facilities in Russia

The states characterized by pronounced hypercoagulable components (deep vein thrombosis, cardio- and cerebro-vascular pathologies) are caused by multiple pathophysiological factors, including insufficient supply of magnesium (Mg) and other micronutrients.

AIM

to present results of analysis of the Institute of Microelements Data Base (IMDB) performed from point of view of interrelationships of Mg deficit and hypercoagulable states in adults treated in medico-preventive facilities of Central, Northwestern, Northern, and Siberian federal districts of Russia.

METHODS

The analysis was realized as analysis of data obtained in a cross-sectional study. In the cohort of patients (n=1453) formed from the IMBD adequacy of Mg supply was assessed by magnesium levels in blood plasma (MgBP) (0.69±0.15 mmol/L) and estimates of daily Mg consumption according to dietary diaries (MgD) (185±90 mg/day).

RESULTS

Mg supply was adequate (MgBP >0.80 mmol/L, MgD >300 mg/day) in not more than 6% of patients. Presence of "Hypercoagulation" label in data base was associated with greater number of chronic diseases (2.3±2.1 and 0.83±0.8 with and without this label, respectively, р=0.0006) and elevated risk of the presence on 4 comorbid pathologies (odds ratio [OR] 18, 95% confidence interval [CI] 10-25, р=0.0006). Mg deficit (MgBP.

GIAO-DFT calculation of 15 N NMR chemical shifts of Schiff bases: Accuracy factors and protonation effects

¹⁵ N NMR chemical shifts in the representative series of Schiff bases together with their protonated forms have been calculated at the density functional theory level in comparison with available experiment. A number of functionals and basis sets have been tested in terms of a better agreement with experiment. Complimentary to gas phase results, 2 solvation models, namely, a classical Tomasi's polarizable continuum model (PCM) and that in combination with an explicit inclusion of one molecule of solvent into calculation space to form supermolecule 1:1 (SM + PCM), were examined. Best results are achieved with PCM and SM + PCM models resulting in mean absolute errors of calculated ¹⁵ N NMR chemical shifts in the whole series of neutral and protonated Schiff bases of accordingly 5.2 and 5.8 ppm as compared with 15.2 ppm in gas phase for the range of about 200 ppm. Noticeable protonation effects (exceeding 100 ppm) in protonated Schiff bases are rationalized in terms of a general natural bond orbital approach.

Substitution effects in the 15 N NMR chemical shifts of heterocyclic azines evaluated at the GIAO-DFT level

A systematic study of the accuracy factors for the computation of ¹⁵ N NMR chemical shifts in comparison with available experiment in the series of 72 diverse heterocyclic azines substituted with a classical series of substituents (CH₃ , F, Cl, Br, NH₂ , OCH₃ , SCH₃ , COCH₃ , CONH₂ , COOH, and CN) providing marked electronic σ- and π-electronic effects and strongly affecting ¹⁵ N NMR chemical shifts is performed. The best computational scheme for heterocyclic azines at the DFT level was found to be KT3/pcS-3//pc-2 (IEF-PCM). A vast amount of unknown ¹⁵ N NMR chemical shifts was predicted using the best computational protocol for substituted heterocyclic azines, especially for trizine, tetrazine, and pentazine where experimental ¹⁵ N NMR chemical shifts are almost totally unknown throughout the series. It was found that substitution effects in the classical series of substituents providing typical σ- and π-electronic effects followed the expected trends, as derived from the correlations of experimental and calculated ¹⁵ N NMR chemical shifts with Swain-Lupton's F and R constants.

[Deficit of Magnesium and States of Hypercoagulation: Intellectual Analysis of Data Obtained From a Sample of Patients Aged 18-50 years From Medical and Preventive Facilities in Russia]

The states characterized by pronounced hypercoagulable components (deep vein thrombosis, cardio- and cerebro-vascular pathologies) are caused by multiple pathophysiological factors, including insufficient supply of magnesium (Mg) and other micronutrients.

AIM

to present results of analysis of the Institute of Microelements Data Base (IMDB) performed from point of view of interrelationships of Mg deficit and hypercoagulable states in adults treated in medico-preventive facilities of Central, Northwestern, Northern, and Siberian federal districts of Russia.

METHODS

The analysis was realized as analysis of data obtained in a cross-sectional study. In the cohort of patients (n=1453) formed from the IMBD adequacy of Mg supply was assessed by magnesium levels in blood plasma (Mg BP) (0.69±0.15 mmol/L) and estimates of daily Mg consumption according to dietary diaries (Mg D) (185±90 mg/day).

RESULTS

Mg supply was adequate (Mg BP >0.80 mmol/L, Mg D >300 mg/day) in not more than 6 % of patients. Presence of "Hypercoagulation" label in data base was associated with greater number of chronic diseases (2.3±2.1 and 0.83±0.8 with and without this label, respectively, р=0.0006) and elevated risk of the presence on 4 comorbid pathologies (odds ratio [OR] 18, 95 % confidence interval [CI] 10-25, р=0.0006). Mg deficit (Mg BP.

On the accuracy factors and computational cost of the GIAO-DFT calculation of 15 N NMR chemical shifts of amides

The main factors affecting the accuracy and computational cost of Gauge-independent Atomic Orbital-density functional theory (GIAO-DFT) calculation of ¹⁵ N NMR chemical shifts in the benchmark series of 16 amides are considered. Among those are the choice of the DFT functional and basis set, solvent effects, internal reference conversion factor and applicability of the locally dense basis set (LDBS) scheme. Solvent effects are treated within the polarizable continuum model (PCM) scheme as well as at supermolecular level with solvent molecules considered in explicit way. The best result is found for Keal and Tozer's KT3 functional used in combination with Jensen's pcS-3 basis set with taking into account solvent effects within the polarizable continuum model. The proposed LDBS scheme implies pcS-3 on nitrogen and pc-2 elsewhere in the molecule. The resulting mean average error for the calculated ¹⁵ N NMR chemical shifts is about 6 ppm. The application of the LDBS approach tested in a series of 16 amides results in a dramatic decrease in computational cost (more than an order of magnitude in time scale) with insignificant loss of accuracy.

[INTERACTION OF GLUTAMATE AND GABA RECEPTORS IN THE CENTRAL NERVOUS SYSTEM]

The article provides an overview of postsynaptic interaction of GABA and glutamate receptors in central neurons. Co-localization of GABA and glutamate in synapses, structure and function of their receptors and interaction of both ionotropic and metabotropic glutamate and GABA receptors are being discussed.

Theoretical and experimental (15)N NMR study of enamine-imine tautomerism of 4-trifluoromethyl[b]benzo-1,4-diazepine system

The tautomeric structure of 4-trifluoromethyl[b]benzo-1,4-diazepine system in solution has been evaluated by means of the calculation of (15)N NMR chemical shifts of individual tautomers in comparison with the averaged experimental shifts to show that the enamine-imine equilibrium is entirely shifted toward the imine form. The adequacy of the theoretical level used for the computation of (15)N NMR chemical shifts in this case has been verified based on the benchmark calculations in the series of the push-pull and captodative enamines together with related azomethynes, which demonstrated a good to excellent agreement with experiment.

Theoretical and experimental study of 15N NMR protonation shifts

A combined theoretical and experimental study revealed that the nature of the upfield (shielding) protonation effect in 15N NMR originates in the change of the contribution of the sp(2)-hybridized nitrogen lone pair on protonation resulting in a marked shielding of nitrogen of about 100 ppm. On the contrary, for amine-type nitrogen, protonation of the nitrogen lone pair results in the deshielding protonation effect of about 25 ppm, so that the total deshielding protonation effect of about 10 ppm is due to the interplay of the contributions of adjacent natural bond orbitals. A versatile computational scheme for the calculation of 15N NMR chemical shifts of protonated nitrogen species and their neutral precursors is proposed at the density functional theory level taking into account solvent effects within the supermolecule solvation model.

Solvent effects in the GIAO-DFT calculations of the 15N NMR chemical shifts of azoles and azines

The calculation of (15)N NMR chemical shifts of 27 azoles and azines in 10 different solvents each has been carried out at the gauge including atomic orbitals density functional theory level in gas phase and applying the integral equation formalism polarizable continuum model (IEF-PCM) and supermolecule solvation models to account for solvent effects. In the calculation of (15)N NMR, chemical shifts of the nitrogen-containing heterocycles dissolved in nonpolar and polar aprotic solvents, taking into account solvent effect is sufficient within the IEF-PCM scheme, whereas for polar protic solvents with large dielectric constants, the use of supermolecule solvation model is recommended. A good agreement between calculated 460 values of (15)N NMR chemical shifts and experiment is found with the IEF-PCM scheme characterized by MAE of 7.1 ppm in the range of more than 300 ppm (about 2%). The best result is achieved with the supermolecule solvation model performing slightly better (MAE 6.5 ppm).

On the accuracy of the GIAO-DFT calculation of 15N NMR chemical shifts of the nitrogen-containing heterocycles--a gateway to better agreement with experiment at lower computational cost

The main factors affecting the accuracy and computational cost of the gauge-independent atomic orbital density functional theory (GIAO-DFT) calculation of (15)N NMR chemical shifts in the representative series of key nitrogen-containing heterocycles--azoles and azines--have been systematically analyzed. In the calculation of (15)N NMR chemical shifts, the best result has been achieved with the KT3 functional used in combination with Jensen's pcS-3 basis set (GIAO-DFT-KT3/pcS-3) resulting in the value of mean absolute error as small as 5 ppm for a range exceeding 270 ppm in a benchmark series of 23 compounds with an overall number of 41 different (15)N NMR chemical shifts. Another essential finding is that basically, the application of the locally dense basis set approach is justified in the calculation of (15)N NMR chemical shifts within the 3-4 ppm error that results in a dramatic decrease in computational cost. Based on the present data, we recommend GIAO-DFT-KT3/pcS-3//pc-2 as one of the most effective locally dense basis set schemes for the calculation of (15)N NMR chemical shifts.

[Effect of oregano essential oil on the engraftment and development of Lewis carcinoma in F1 DBA C57 black hybrid mice]

The effect of a low uptake dose of oregano essential oil with drinking water for three months (Origanum vulgare L.) on the degree of Lewis carcinoma engraftment and some parameters of oxidative stress has been studied in vivo using F1 DBA C57 Black hybrid mice. Oregano essential oil has been established to possess an anticancer activity. The degree of tumor engraftment decreased by 1.8 times, its size decreased by 1.5 times, and the development of tumor was significantly suppressed in sick mice under the effect of oregano essential oil. It was found that the uptake of essential oil did not affect the intensity of lipid peroxidation in the brain of mice and resulted in a significantly (by 36%) decreased content of secondary lipid oxidation products in the liver as shown in a reaction with thiobarbituric acid as compared to control subjects. The activity of antioxidant enzymes was found to increase after three months of essential oil uptake (by 1.5-3 times) as compared to the control group. This effect of essential oil supports the presence of bioantioxidant properties in this essential oil.

[Diagnosis of mixed tick-borne encephalitis and tick-borne borreliosis in the early stages of the disease]

The paper describes a method of prognosis for the possible development of mixed tick-borne encephalitis and borreliosis based on a comparison of clinical manifestations of the disease and results of laboratory tests.

[The effect of volatile antioxidants of plant origin on leukemogenesis in mice]

The effect of savory essential oil added with drinking water (150 ng/ml) or with feed (2.5 microg/g) on the lifetime of AKR mice and the parameters of oxidative stress in animal blood were investigated. It was found for the first time that long-term administration of an essential oil in low doses increased the average lifetime of mice by 20-35% and was accompanied by a decrease in the hemolysis level and the content of lipid peroxidation products in erythrocytes of mice, as well as alteration in the structural state of their membranes and stabilization of polyunsaturated fatty acids level in mice liver cells.

High-power picosecond laser pulse recirculation

We demonstrate a nonlinear crystal-based short pulse recirculation cavity for trapping the second harmonic of an incident high-power laser pulse. This scheme aims to increase the efficiency and flux of Compton-scattering-based light sources. We demonstrate up to 40x average power enhancement of frequency-doubled submillijoule picosecond pulses, and 17x average power enhancement of 177 mJ, 10 ps, 10 Hz pulses.

Isotope-specific detection of low-density materials with laser-based monoenergetic gamma-rays

What we believe to be the first demonstration of isotope-specific detection of a low-Z and low density object shielded by a high-Z and high-density material using monoenergetic gamma rays is reported. The isotope-specific detection of LiH shielded by Pb and Al is accomplished using the nuclear resonance fluorescence line of L7i at 478 keV. Resonant photons are produced via laser-based Compton scattering. The detection techniques are general, and the confidence level obtained is shown to be superior to that yielded by conventional x-ray and gamma-ray techniques in these situations.

[Effect of antioxidant beta-(4-hydroxy-3,5-ditertbutylphenyl) propionic acid (phenosan) on the development of malignant neoplasms]

The effect of different doses of synthetic antioxidant beta-(4-hydroxy-3,5-ditertbutylphenyl)propionic acid (phenosan) on the development of spontaneous leukemia in AKR mice was studied. The drug efficiency was determined from the survival curves, animal life spans, and the incidence of leukemia. Phenosan exhibited a pronounced antitumor activity at therapeutic (10(-4) mol/kg, 4 administrations) and ultra-low (10(-14) mol/kg, 4 administrations) doses. The dose of 10(-4) mol/kg proved most efficient to increase the life span of the shortlived subpopulation, while the dose of 10(-14) mol/kg increased the life span of the long-lived subpopulation. The ultra-low dose of the drug seems promising as a prophylactic agent.

[Diagnosis, prevention and treatment of renal lesion in extracorporeal shock wave lithotripsy]

The diagnosis and treatment of 120 patients with urolithiasis were made. The following examinations were made: the study of immune status and lipid peroxidation, detection of selective proteinuria, leukocyte migration inhibition reaction with autoantigens obtained from the tissues of the renopelvic segment providing additional information about renal parenchyma and immune system. The patients were divided into two groups: 70 patients of the study group received pre-, intra- and postoperative preventive pharmacotherapy, while 50 patients of the control group received standard therapy. It is shown that preventive measures in the patients of the study group aimed at raising resistance of the kidney to the shock wave and prevention of infectious-inflammatory process evidence for necessity of the above measures not only before extracorporeal shock wave lithotripsy, but also in intra- and postoperative periods.

[Effect of low-level irradiation on incidence rate and development of malignant neoplasms]

Low-level irradiation (1.2-2.4 cGy, dose-rate 0.6 cGy/day) leads to a significant acceleration of the development of spontaneous leukosis in AKR mice: decrease in the average and the maximum life-span of animals leukosis-carriers (by 20 and 120 days, respectively) and an increase in the leukosis incidence rate (%). The introduction of antioxidant phenozan (beta-(4-hydroxy-3,5-ditertbutylphenyl) propionic acid) results in a considerable antileukosis effect: the average life-span increases by more than 40 days and the leukosis incidence rate decreases by 6%.

[A rare complication after surgical correction of the rupture of Valsalva's sinus aneurysm into the right heart ventricle]

Postsurgical myocardial infarction in a 68-year-old female was observed after occasional compression of the coronary artery by a teflon gasket when P-like suture was applied on the anterior wall of the right ventricle in the course of surgical intervention for closure of the aortic-right-ventricular fistula. The latter had formed after the rupture of Valsalva's sinus aneurysm into the right ventricle this being the cause of the surgery. The authors propose how to document the diagnosis and medical death certificate in similar cases.

[Modification of pathologo-anatomic method of heart dissection after valve prosthesises implantation]

Modification of the method of heart dissection in patients who died after valve replacement is suggested. After standard atrial cutting dissection of the ventricles is made from the apex along the interatrial fissure without cutting the proximal regions of the coronary arteries. The method allows good inspection of the ventricular cavities and elucidation of the relationships between anatomical structures and artificial valves.

[Dearterialization of the liver as a treatment method in hemangiomas]

The article is devoted to the experiences with treatment of hemangiomatous lesions of the liver. Results of palliative treatment of 65 patients by methods of dearterialization of the liver (ligation and embolization of the hepatic artery) are presented. The authors make a conclusion that dearterialization of the liver is a sufficiently effective method of treatment resulting in sclerosing the hemangiomas and substitution of them with the fibrous tissue. It is not followed by the development of pronounced complications and lethality. With clinical manifestations retained after embolization of the hepatic artery it is possible to perform resection of the liver with hemangioma, the operative intervention in this case being accompanied by less blood loss, and it is easier technically than when it is fulfilled without preliminary dearterialization of the liver.