Pure Isotropic Proton NMR Spectra in Solids using Deep Learning

The resolution of proton solid-state NMR spectra is usually limited by broadening arising from dipolar interactions between spins. Magic-angle spinning alleviates this broadening by inducing coherent averaging. However, even the highest spinning rates experimentally accessible today are not able to completely remove dipolar interactions. Here, we introduce a deep learning approach to determine pure isotropic proton spectra from a two-dimensional set of magic-angle spinning spectra acquired at different spinning rates. Applying the model to 8 organic solids yields high-resolution ¹H solid-state NMR spectra with isotropic linewidths in the 50–400 Hz range.     

May thermal imaging be useful in the assessment of dental anaesthesia? Preliminary study

Journal of Thermal Analysis and Calorimetry - The main goal of this study was to find out if thermal imaging may be useful in the evaluation of two types of anaesthetic injections—with and...     

Phosphorylated flavonoids as selective carboxylesterase inhibitors

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Transalkylation of alkyl aryl sulfides with alkylating agents

The reaction of methyl iodide with tert-butylphenylsulfide in DMF leads to a transalkylation that produces methylphenylsulfide. This transalkylation reaction was further studied by ¹H NMR spectroscopy. The polarity of the solvent, the electron density on the sulfur atom, and the strength of the alkylating agent (MeI, EtI, BuI, dimethyl sulfate, or dimethyl carbonate) played important roles in the reaction. The suggested mechanism of the reaction involves the formation of a dialkyl aryl sulfonium salt that subsequently eliminates the radical. This mechanism was supported by the observation of higher conversion rates for compounds with more branched alkyl groups on the sulfur atom, which may lead to the formation of more stable radicals.     

Firefly Luciferase‐based Fusion Proteins and their Applications in Bioanalysis

Firefly luciferase is widely used in molecular biology and bioanalytical systems as a reporter molecule due to the high quantum yield of the bioluminescence, availability of stable mutant forms of the enzyme with prescribed spectral characteristics and abundance of bacterial expression systems suitable for production of recombinant proteins in limitless quantities. In this review, we described fusion proteins of luciferase with biotin‐binding domain and streptavidin, with proteins A and G, antibodies, with DNA‐ and RNA‐binding proteins, as well as fusion proteins designed for BRET systems. The firefly luciferase‐based fusion proteins are represented as an effective tool for the development of different bioanalytical systems such as (1) systems in which luciferase is attached to the surface of the target and the bioluminescence signal is detected from the specific complexes formed; (2) BRET‐based systems, in which the specific interaction induces changes in the bioluminescence spectrum; and (3) systems that use modified or split luciferases, in which the luciferase activity changes under the action of the analyte. All these systems have wide application in biochemical analysis of physiologically important compounds, for the detection of pathogenic bacteria and viruses, for evaluation of protein–protein interactions, assaying of metabolites involved in cell communication and cell signaling.     

Persulfate treatment as a method of modifying carbon electrode material for aqueous electrochemical capacitors

The activated carbon was modified by the wet method with a solution of ammonium persulfate at room temperature with different times. Kinetics studies showed that the modification took place mostly during the first 60 min of the process. The physicochemical properties of the obtained carbon were evaluated by thermogravimetric studies, Raman and FTIR spectroscopy, elementary and BET analyses. Furthermore, the fabricated material was applied in symmetric capacitors operated on the three aqueous electrolytes (1 M H₂SO₄, 6 M KOH and 1 M Na₂SO₄). Mild conditions of the modification process are optimal to obtain electroactive groups on the carbon surface, which make this material useful in a supercapacitor application. In our studies, we noticed that this type of functional groups mainly appears on the surface of the activated carbon, in the first oxidation stage. With prolonged oxidation, they may transform into undesirable groups. The results show that this kind of modification improves the capacity of all the tested supercapacitors. It was connected mainly with an increase of the carbon material’s wettability and in the case of capacitor operated in acid and base electrolytes due to a redox reaction of oxygen functional groups.

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Graphical abstract Persulfate treatment of carbon material.

     

New Approach to the Formation of Physically Adsorbed Capillary Coatings Consisting of Hyperbranched Poly(Ethylene Imine) with a Maltose Shell to Enhance the Separation of Catecholamines and Proteins in CE

Core–shell-type polymers based on a hyperbranched (hb) poly(ethylenimine) core and a shell with a variable maltose content were applied as coating materials for fused silica capillaries. A new, simple, fast, and reproducible way of modifying the capillary walls through the physical adsorption of the core–shell-type polymers using a Cu²⁺ support was developed. The coating created by this method was found to be very stable compared to the coating created using a solution of the polymer only. Capillaries modified with the core–shell-type polymers were tested by applying them to the electrophoretic separation of catecholamines and proteins. The modified capillaries showed high efficiencies (up to 800,000 theoretical plates per meter for lysozyme) and separation selectivities. The highest efficiency was achieved using capillaries modified with the polymer containing the lowest content of maltose in the shell and the most accessible positively charged core. Various online concentration techniques were also tested as a means to lower detection limits further, making it possible to analyze proteins in biological fluids (saliva) as well as catecholamines in human urine after SPE using activated alumina.     

The molecular structure of selected minerals of the rosasite group – An XRD,SEM and infrared spectroscopic study

Minerals in the rosasite mineral group namely rosasite, glaucosphaerite, kolwezite, mcguinnessite have been studied by powder X-ray diffraction, scanning electron microscopy and infrared spectroscopy. X-ray diffraction shows the minerals to be complex mixtures with more than one rosasite mineral observed in each sample. SEM analysis shows the minerals to be fibrous in nature and the use of EDAX enabled the chemical composition of the minerals to be determined. The spectral patterns for the minerals rosasite, glaucosphaerite, kolwezite and mcguinnessite are similar to that of malachite implying the molecular structure is similar to malachite. A comparison is made with the spectrum of malachite. The rosasite mineral group is characterised by two OH stretching vibrations at ∼3401 and 3311 cm⁻¹. Two intense bands observed at ∼1096 and 1046 cm⁻¹ are assigned to ν₁ (CO₃)²⁻ symmetric stretching vibration and the δ OH deformation mode. Multiple bands are found in the 800–900 and 650–750 cm⁻¹ regions attributed to the ν₂ and ν₄ bending modes confirming the symmetry reduction of the carbonate anion in the rosasite mineral group as C_2v or C_s. A band at ∼560 cm⁻¹ is assigned to a CuO stretching mode.     

A Multifield Study on Dimethyl Acetylenedicarboxylate: A Reagent Able to Build a New Cycle on Diaminoimidazoles

A new effective method for the synthesis of imidazo[1,5-b]pyridazines derivatives (yields = 68–89%) by the interaction of 1,2-diamino-4-phenylimidazole with DMAD, in methanol and in the presence of a catalytic amount of acetic acid, is proposed. The course of reaction has been examined by classical organic methods, HPLC-MS analysis, and quantum-chemical calculations.