The A·T(rWC)/A·T(H)/A·T(rH) ↔ A·T*(rwWC)/A·T*(wH)/A·T*(rwH) mutagenic tautomerization via sequential proton transfer: a QM/QTAIM study

In this study for the first time we have revealed by QM and QTAIM calculations at the MP2/aug-cc-pVDZ//B3LYP/6-311++G(d,p) level of QM theory the novel routes of the mutagenic tautomerization of three biologically important A·T DNA base pairs – reverse Watson–Crick A·T(rWC), Hoogsteen A·T(H) and reverse Hoogsteen A·T(rH) – followed by their rebuilding into the wobble (w) A·T*(rw_WC), A·T*(w_H) and A·T*(rw_H) base mispairs by the participation of the mutagenic tautomers of the DNA bases (denoted by asterisk) and vice versa, thus complementing the physico-chemical property of the canonical A·T(WC) Watson–Crick DNA base pair reported earlier (Brovarets'' et al., RSC Adv., 2015, 5, 99594–99605). These non-dissociative tautomeric transformations in the classical A·T(rWC), A·T(H) and A·T(rH) DNA base pairs proceed similarly to the canonical A·T(WC) DNA base pair via the intrapair sequential proton transfer with shifting towards major or minor grooves of DNA followed by further double proton transfer along the intermolecular H-bonds and are controlled by the plane symmetric and highly stable transition states – tight ion pairs formed by the A⁺ nucleobase, protonated by the N1/N7 nitrogen atoms, and T⁻ nucleobase, deprotonated by the N3H imino group. Comparison of the estimated populations of the tautomerised states (10⁻²¹ to 10⁻¹⁴) with similar characteristics for the canonical A·T(WC) DNA base pair (10⁻⁸ to 10⁻⁷) leads authors to the conclusion, that only a base pair with WC architecture can be a building block of the DNA macromolecule as a genetic material, which is able for the evolutionary self-development. Among all four classical DNA base pairs, only A·T(WC) DNA base pair can ensure the proper rate of the spontaneous point errors of replication in DNA.

We discovered tautomeric wobbling of the classical A·T DNA base pairs. This data evidence, that only a base pair with Watson–Crick architecture can be a building block of the DNA macromolecule as a genetic material, which is able for the evolutionary self-development.     

Residual Fire Resistance Testing of Basalt- and Hybrid-FRP Reinforced Concrete Beams

The fire resistance of fiber-reinforced polymer reinforced concrete (FRP-RC) elements depends on the temperature performance of the original concrete member, the fire scenario, and FRP reinforcement behavior. In this study, fire resistance tests are described, along with the characteristics obtained during and after applying elevated temperatures, simulating the effects of fire. The tested beams were reinforced with basalt (BFRP) bars and with a hybrid composite of carbon fibers and basalt fibers (HFRP) bars. Fire tests were performed on full-scale beams, in which the midsections of the beams were heated from below (tension zone) and from the sides for two hours, after which the beams were cooled and subjected to flexural testing. BFRP-RC beams failed before the heating time was completed; the best failure was associated with a BFRP reinforced beam that failed approximately 108 min after heating. Contrary to the BFRP-RC samples, HFRP-RC beams were capable of resisting exposure to elevated temperatures for two hours, but showed a 70% reduction in strength capacity when compared to non-heated reference beams. According to the author, the higher resistance of HFRP-RC beams was the result of the thermal expansion coefficient of carbon fibers employed in HFRP, which “prestresses” the beams and enables smaller deflections. The preliminary findings of this study can increase the feasibility of using FRP materials for engineering purposes.     

Ni–Al–Cr superalloy as high temperature cathode current collector for advanced thin film Li batteries

To obtain full advantage of state-of-the-art solid-state lithium-based batteries, produced by sequential deposition of high voltage cathodes and promising oxide-based electrolytes, the current collector must withstand high temperatures (>600 °C) in oxygen atmosphere. This imposes severe restrictions on the choice of materials for the first layer, usually the cathode current collector. It not only must be electrochemically stable at high voltage, but also remain conductive upon deposition and annealing of the subsequent layers without presenting a strong diffusion of its constituent elements into the cathode. A novel cathode current collector based on a Ni–Al–Cr superalloy with target composition Ni_0.72Al_0.18Cr_0.10 is presented here. The suitability of this superalloy as a high voltage current collector was verified by determining its electrochemical stability at high voltage by crystallizing and cycling of LiCoO₂ directly onto it.

A novel cathode current collector based on a Ni–Al–Cr superalloy is presented here. The suitability of this superalloy as a high voltage current collector was verified by crystallizing and cycling of LiCoO₂ directly onto it.     

Septal myectomy with mitral valve surgery in patients after alcohol septal ablation

Open in a separate window OBJECTIVESWe studied 16 patients after failed alcohol septal ablation who underwent extended septal myectomy to analyse the results of surgical correction and identify technical pitfalls the surgeons may be confronted by.METHODSBetween October 2017 and March 2019, 16 patients underwent surgical extended septal myectomy with accompanying anomalous secondary chordae resection, papillary muscles mobilization [in 9 (56.3%) patients], and anterior mitral leaflet plication after previously failed alcohol septal ablation. Routine preoperative computed tomography or cardiac magnetic resonance planning and intraoperative transoesophageal echocardiography were performed in each of the studied patients. Major technical features were identified and complemented during septal myectomy of the calcified interventricular septum.RESULTSThe mean age of the studied patients accounted 50.5 ± 14.6, median—54; males—5 (31.3%). Mean cross-clamp time accounted 52 ± 7.2 min. Calcified basal interventricular septum was identified in 2 (12.5%) patients. No iatrogenic ventricular septal defect (0%) was made during surgical correction. Peak systolic pressure gradient decreased from 86 (interquartile range: 75–104.7) to 20 (16–22) mmHg (P< 0.001). No patients with moderate or severe mitral regurgitation were identified, whereas before the procedure, the number of those accounted 13 (81.2%) individuals. In-hospital and overall mortality after septal myectomy accounted 0%.CONCLUSIONSExtended septal myectomy in patients who previously underwent alcohol septal ablation is a safe procedure that affects all pathological manifestations of the disease. Routine preoperative computed tomography or cardiac magnetic resonance provides detailed anatomy of the anomalous left ventricle and subvalvular structures and allows to measure the extension of myectomy preventing the occurrence of iatrogenic ventricular septal defect. Septal myectomy of the calcified interventricular septum requires avoidance of ‘one-piece technique’ since fragmental myectomy allows visually control the adequacy of the left ventricle outflow tract release.     

Modelling of the Fine-Grained Materials Briquetting Process in a Roller Press with the Discrete Element Method

By using the Altair^® EDEM™ software, which implements the discrete element method, modelling and further study of the processes occurring in the roller press’s deformation area were carried out. It was shown that the discrete element method makes it possible to accurately describe the phenomena occurring in the area of roller press deformation compared with the finite element method. Models of material compaction in a roller press are developed using calcium hydroxide (slaked lime) and copper ore concentrate. The developed model makes it possible to determine the process’s energy parameters and the material’s compaction characteristics, taking into account the characteristics of its constituent particles. It was shown that discrete element modelling could be used effectively to create roller presses that provide rational characteristics of the briquetting process, taking into account the properties of the material being briquetted and the operating modes of the equipment. The results of the studies provided the basis for the applicability of the development of the discrete element method for describing the phenomena occurring in roller presses and accelerating the design of press equipment and briquetting technological processes.     

Synthesis and mode of action studies of novel {2‐(3‐R‐1H‐1,2,4‐triazol‐5‐yl)phenyl}amines to combat pathogenic fungi

Due to their high specificity and efficacy, triazoles have become versatile antifungals to treat fungal infections in human healthcare and to control phytopathogenic fungi in agriculture. However, azole resistance is an emerging problem affecting human health as well as food security. Here we describe the synthesis of 10 novel {2‐(3‐R‐1H‐1,2,4‐triazol‐5‐yl)phenyl}amines. Their structure was ascertained by liquid chromatography–mass spectrometry, ¹H and ¹³C NMR, and elemental analysis data. Applying an in vitro growth assay, these triazoles show moderate to significant antifungal activity against the opportunistic pathogen Aspergillus niger, 12 fungi (Fusarium oxysporum, Fusarium fujikuroi, Colletotrichum higginsianum, Gaeumannomyces graminis, Colletotrichum coccodes, Claviceps purpurea, Alternaria alternata, Mucor indicus, Fusarium graminearum, Verticillium lecanii, Botrytis cinerea, Penicillium digitatum) and three oomycetes (Phytophtora infestans GL‐1, P. infestans 4/91; R+ and 4/91; R?) in the concentration range from 1 to 50 µg/ml (0.003–2.1 μM). Frontier molecular orbital energies were determined to predict their genotoxic potential. Molecular docking calculations taking into account six common fungal enzymes point to 14α‐demethylase (CYP51) and N‐myristoyltransferase as the most probable fungal targets. With respect to effectiveness, structure–activity calculations revealed the strong enhancing impact of adamantyl residues. The shown nonmutagenicity in the Salmonella reverse‐mutagenicity assay and no violations of drug‐likeness parameters suggest the good bioavailability and attractive ecotoxicological profile of the studied triazoles.     

Measurements of Surface Impedance in MgB2 in DC Magnetic Fields: Insights in Flux-Flow Resistivity

We present the multifrequency measurements of the surface resistance of spark-plasma-sintered MgB2 performed through a dielectric loaded resonator operating at 16.5 and 26.7 GHz. By normally applying magnetic fields ≤1.2 T to the sample surface, we drove it in the mixed state. By means of data-rooted analysis, we found that the sample vortex dynamics could be fully described within a single-component approach. Pinning phenomena were present and characterized by a depinning frequency smaller than the measurement ones. The multiband nature of the superconductor emerged in the flux-flow resistivity, whose field dependence could be interpreted well within theoretical models. By exploiting them, the upper critical field was extracted in the low-temperature range, which exhibited a consistent temperature trend with the values obtained at the onset of the resistive transition near Tc, and was well in line with literature data on other polycrystalline samples.