Formation of 1-pyrazoline 1,2-dioxides by oxidation of 1,3-hydroxylamino oximes

Cyclization with the formation of an N-N bond and simultaneous bromination, which lead to 3-bromo-1-pyrazoline 1,2-dioxides, apparently through a step involving the dinitroso derivative, occur in the reaction of sodium hypobromite with 1,3-hydroxylamino oximes. Dehydrobromination of the bromopyrazoline leads to the corresponding 3H-pyrazole. The same treatment of acetylacetone dioxime gives 4H-dibromo-3,5-dimethyl-4H-pyrazole 1,2-dioxide. which is readily hydrolyzed to the corresponding 4-oxo derivative. Data from the IR, UV, and PMR spectra are presented.     

Parameters of the oscillation reaction bromate-malonic acid-manganese(II,III) and state of the catalyst

Theoretical and Experimental Chemistry -     

Catalytic oxidation-reduction disproportionation of phenylhydrazine by the action of [Ru(NH3)5Cl]Cl2

Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 943–944, April, 1988.     

Ionization and stabilization of an atom in a quantum electromagnetic field

The dynamics of a model atomic system interacting with a quantum electromagnetic field has been investigated. The effect of statistics and average number of photons in a quantum state of the field on the ionization and stabilization of the atomic subsystem has been studied. The formation of a state with the maximum entanglement between the atomic and field subsystems in the case of interaction with a single-photon field has been demonstrated.     

Σ3 CSL boundary distributions in an austenitic stainless steel subjected to multidirectional forging followed by annealing

The effect of processing and annealing temperatures on the grain boundary characters in the ultrafine-grained structure of a 304-type austenitic stainless steel was studied. An S304H steel was subjected to multidirectional forging (MDF) at 500–800°C to total strains of ~4, followed by annealing at 800–1,000°C for 30 min. The MDF resulted in the formation of ultrafine-grained microstructures with mean grain sizes of 0.28–0.85 μm depending on the processing temperature. The annealing behaviour of the ultrafine-grained steel was characterized by the development of continuous post-dynamic recrystallization including a rapid recovery followed by a gradual grain growth. The post-dynamically recrystallized grain size depended on both the deformation temperature and the annealing temperature. The recrystallization kinetics was reduced with an increase in the temperature of the preceding deformation. The grain growth during post-dynamic recrystallization was accompanied by an increase in the fraction of Σ3ⁿ CSL boundaries, which was defined by a relative change in the grain size, i.e. a ratio of the annealed grain size to that evolved by preceding warm working (D/D₀). The fraction of Σ3ⁿ CSL boundaries sharply rose to approximately 0.5 in the range of D/D₀ from 1 to 5, which can be considered as early stage of continuous post-dynamic recrystallization. Then, the rate of increase in the fraction of Σ3ⁿ CSL boundaries slowed down significantly in the range of D/D₀ > 5. A fivefold increase in the grain size by annealing is a necessary condition to obtain approximately 50% Σ3ⁿ CSL boundaries in the recrystallized microstructure.     

Atomistic insights into rhodopsin activation from a dynamic model

Rhodopsin, the light sensitive receptor responsible for blue-green vision, serves as a prototypical G protein-coupled receptor (GPCR). Upon light absorption, it undergoes a series of conformational changes that lead to the active form, metarhodopsin II (META II), initiating a signaling cascade through binding to the G protein transducin (G(t)). Here, we first develop a structural model of META II by applying experimental distance restraints to the structure of lumi-rhodopsin (LUMI), an earlier intermediate. The restraints are imposed by using a combination of biased molecular dynamics simulations and perturbations to an elastic network model. We characterize the motions of the transmembrane helices in the LUMI-to-META II transition and the rearrangement of interhelical hydrogen bonds. We then simulate rhodopsin activation in a dynamic model to study the path leading from LUMI to our META II model for wild-type rhodopsin and a series of mutants. The simulations show a strong correlation between the transition dynamics and the pharmacological phenotypes of the mutants. These results help identify the molecular mechanisms of activation in both wild type and mutant rhodopsin. While static models can provide insights into the mechanisms of ligand recognition and predict ligand affinity, a dynamic model of activation could be applicable to study the pharmacology of other GPCRs and their ligands, offering a key to predictions of basal activity and ligand efficacy.     

Antioxidant activity of hydrazones with sterically hindered phenol fragments

Kinetic parameters of the antiradical activity of derivatives of hydrazones of 4-hydroxy-3,5-di-tert-butyl-benzaldehyde are determined photocolorimetrically in their reactions with a stable diphenylpicrylhydrazyl radical, and by chemiluminescence from the capture of peroxide radicals upon the initiated oxidation of ethylbenzene. It is found that during inhibited oxidation, the reactive centers (N-H and O-H) in hetaryl- and acylhydrazone molecules operate in parallel. Regularities of the compounds?? inhibiting effect are studied in heterogeneous systems upon the initiated oxidation of ethylbenzene in emulsion, and in a water-lipid model of the oxidation of phosphatidylcholine dispersion. It is established that hydrazone derivatives are antioxidants of combined action in heterophase processes of the oxidation of unsaturated substrates, displaying properties of hydroperoxide deactivators in addition to their antiradical activity.