Thioredoxin and lipoic acid catalyze the denitrosation of low molecular weight and protein S-nitrosothiols

The nitrosation of cellular thiols has attracted much interest as a regulatory mechanism that mediates some of the pathophysiological effects of nitric oxide (NO). In cells, virtually all enzymes contain cysteine residues that can be subjected to S-nitrosation, whereby this process often acts as an activity switch. Nitrosation of biological thiols is believed to be mediated by N2O3, metal-nitrosyl complexes, and peroxynitrite. To date, however, enzymatic pathways for S-denitrosation of proteins have not been identified. Herein, we present experimental evidence that two ubiquitous cellular dithiols, thioredoxin and dihydrolipoic acid, catalyze the denitrosation of S-nitrosoglutathione, S-nitrosocaspase 3, S-nitrosoalbumin, and S-nitrosometallothionenin to their reduced state with concomitant generation of nitroxyl (HNO), the one-electron reduction product of NO. In these reactions, formation of NO and HNO was assessed by ESR spectrometry, potentiometric measurements, and quantification of hydroxylamine and sodium nitrite as end reaction products. Nitrosation and denitrosation of caspase 3 was correlated with its proteolytic activity. We also report that thioredoxin-deficient HeLa cells with mutated thioredoxin reductase denitrosate S-nitrosothiols less efficiently. We conclude that both thioredoxin and dihydrolipoic acid may be involved in the regulation of cellular S-nitrosothiols.     

Strikingly High Activity of 15-Lipoxygenase Towards Di-Polyunsaturated Arachidonoyl/Adrenoyl-Phosphatidylethanolamines Generates Peroxidation Signals of Ferroptotic Cell Death

The vast majority of membrane phospholipids (PLs) include two asymmetrically positioned fatty acyls: oxidizable polyunsaturated fatty acids (PUFA) attached predominantly at the sn2 position, and non-oxidizable saturated/monounsaturated acids (SFA/MUFA) localized at the sn1 position. The peroxidation of PUFA-PLs, particularly sn2-arachidonoyl(AA)- and sn2-adrenoyl(AdA)-containing phosphatidylethanolamines (PE), has been associated with the execution of ferroptosis, a program of regulated cell death. There is a minor subpopulation (≈1–2 mol %) of doubly PUFA-acylated phospholipids (di-PUFA-PLs) whose role in ferroptosis remains enigmatic. Here we report that 15-lipoxygenase (15LOX) exhibits unexpectedly high pro-ferroptotic peroxidation activity towards di-PUFA-PEs. We revealed that peroxidation of several molecular species of di-PUFA-PEs occurred early in ferroptosis. Ferrostatin-1, a typical ferroptosis inhibitor, effectively prevented peroxidation of di-PUFA-PEs. Furthermore, co-incubation of cells with di-AA-PE and 15LOX produced PUFA-PE peroxidation and induced ferroptotic death. The decreased contents of di-PUFA-PEs in ACSL4 KO A375 cells was associated with lower levels of di-PUFA-PE peroxidation and enhanced resistance to ferroptosis. Thus, di-PUFA-PE species are newly identified phospholipid peroxidation substrates and regulators of ferroptosis, representing a promising therapeutic target for many diseases related to ferroptotic death.     

Surfactants in Thin-Layer Chromatography

Data reported in the literature on the use of surfactants as modifiers of mobile and stationary phases in thin-layer chromatography are analyzed. The features of micellar and ion-pair versions of thin-layer chromatography and the dynamic and static modifications of stationary phases with surfactants are considered.     

Isomers of some vinyl and allyl compounds

The structures of two rotational isomers of styrene, methyl methacrylate, N-vinylpyrrolidone, and allyl benzoate found by AM1 calculations are discussed. Their formation is indicated by the presence of two minima on the curves of the rotation barriers around the C¹-C², C²-N³ and C(=O)-O, O-C(H₂) bonds. The structures of the isomers of allyl compounds were detected capable of providing the cyclization reaction and hydrogen atom elimination. It was found that both double bonds were of similar reactivity. The suggested structures of the isomers can participate in intermolecular interactions with the formation of self-associates and heteroassociates (molecular complexes) due to the presence of C=C and C=O groups with different degree of conjugation.     

Optimizing zirconia-based solid electrolyte cell operated as oxidizing reactor and chromatographic sensor

A zirconia-based (0.9ZrO₂ · 0.1Y₂O₃) high-temperature electrochemical reactor with three-electrode connection circuit was shown promising if used as a chromatographic sensor for quantitative organic gas detection as well as an organic gas sample preparation device for carbon isotopic analysis. The optimized parameters and working mode of the herein proposed solid electrolyte reactor provided complete organic gas oxidation to stoichiometric oxides without oxygen addition to the carrier gas flow at the temperature of 900 to 950°C. The maximum hydrocarbon gas sample amount was calculated for complete oxidation in the designed reactor. Due to its simple and reliable design, the solid electrolyte reactor can be used instead of a standard oxidizing reactor in an isotopic mass spectrometer.     

Catalytic Activity of Gold-Containing Nanoclusters in Carbon Tetrachloride Addition to Multiple Bonds

Gold nanoparticles immobilized on oxide supports and Au-Ni bimetallic particles catalyze carbon tetrachloride addition to multiple bonds, as is demonstrated by the examples of octene-1 and allylbenzene. The size and catalytic activity of ultrafine particles are governed by the method by which they are prepared. Reaction rate as a function of the total metal content of the catalyst passes through a maximum, whereas the specific activity increases monotonically with decreasing metal content.     

Algorithmic Search for Mesomorphic Compounds in the Series of 4'-[(5,6-Dihydro-4-methyl-2H-pyran-5-yl)- amino]benzylidene-4-alkoxyanilines

A computer analysis of the relationship between the structure and mesomorphic activity and a search for potentially mesomorphic compounds in the series of azomethines containing a dihydropyranyl fragment, 4'-[(5,6-dihydro-4-methyl-2H-pyran-5-yl)amino]benzylidene-4-alkoxyanilines, were performed using the SARD (Structure Activity Relationship Design) system. The structural fragments exerting positive and negative effects on the manifestation of mesomorphism were revealed. The mesomorphic activity of the training structures and the extent of their similarity with the hypothetical standard of the activity were evaluated. The predictions show 70% agreement with the experiment.     

Structure-mesomorphic activity relationship in the series of nitrogen-containing heterocyclic compounds

The structure-mesomorphic activity relationship was studied using the SARD (Structure Activity Relationship and Design) system for 300 nitrogen-containing heterocyclic compounds of which 178 compounds form a liquid crystal mesophase. Structural fragments exerting positive and negative effects on the manifestation of mesomorphic properties were revealed.     

Effect of annealing on the electrical properties of nitrogen-doped silicon single crystals grown by crucibleless zone melting

The electrical properties of nitrogen-doped silicon single crystals of the n and p types grown by crucibleless zone melting and annealed at 680°C have been studied. It is shown that the annealing brings about the appearance, in the crystals, of nitrogen-containing centers, which form deep donor and acceptor levels in the band gap. The process is accompanied by an increase in the electrical resistivity; the increase is particularly substantial in the initially high-resistance single crystals. On the other hand, in slightly boron-doped single crystals of the n and p types, the conversion of the conduction type is observed. In a converted material of the n-type, the electron mobility is anomalously low, which demonstrates its high electrical spatial inhomogeneity. The energy of the deep acceptor level near E _c ? 0.35 eV introduced during annealing has been determined. The model explaining the phenomena observed is proposed.