Synthesis of 10-(N′-phenyl)imidoyl derivatives of phenothiazine,and their reactions with o,o-dialkylthio- and dithiophosphates

Condensation of phenothiazine with phenyl isocyanide dichloride has given 10(N-phenylchloroformimidoyl)phenothiazine, exchange reactions of which with salts of diakylthio- and dithiophosphoric acids result in rearrangement of the initially formed 10-[N-phenyldialkoxy(thio)phosphorylthioformimidoyl]phenothiazines to 10-{N-phenyl-N-[dialkoxy(thio)phosphoryl]thiocarbamoyl}phenothiazines, while reaction with diisopropyl dithiophosphoric acid affords diisopropyl chlorothiophosphate, phenyl isothiocyanate, and phenothiazine. 10-(N-Phenylethoxyformimidoyl)phenothiazine alkylates dithiophosphoric acid to give 10-(N-phenylcarbamoyl)phenothiazine, while N²-phenyl-N¹,N¹-diethyl-(10-phenothiazinyl)formamidine reacts with diisopropyl dithiophosphoric acid, affording the salt N²-phenyl-N¹,N¹-diethyl-(10-phenothiazinyl)formamidinium O,O-diisopropyl dithiophosphate.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2596–2601, November, 1989.     

Multiphoton Dissociation of Sulfur Hexafluoride in a Vibrationally Cooled Compression Shock

Multiphoton IR dissociation of SF₆ (in a mixture with CH₄) under nonequilibrium conditions of a compression shock formed by an intense, gas dynamically cooled, pulsed molecular beam impacting a solid surface was studied using the HF* luminescence detection ( 2.5 m) technique. The dependences of the HF* luminescence intensity on the distance x between the region in which molecules were excited and the surface and on the laser radiation frequency at different values of x were obtained. It was shown that, as the distance x decreased from 4 to 1.5 mm, the HF* luminescence intensity increased by more than an order of magnitude as compared to the case of excitation of molecules in an undisturbed flow, whereas the frequency dependences of luminescence intensity (SF₆ dissociation yield) were broadened only insignificantly.     

Topography of the free-energy landscape probed via mechanical unfolding of proteins

Single-molecule experiments in which proteins are unfolded by applying mechanical stretching forces generally force unfolding to proceed along a reaction coordinate that is different from that in chemical or thermal denaturation. Here we simulate the mechanical unfolding and refolding of a minimalist off-lattice model of the protein ubiquitin to explore in detail the slice of the multidimensional free-energy landscape that is accessible via mechanical pulling experiments. We find that while the free-energy profile along typical "chemical" reaction coordinates may exhibit two minima, corresponding to the native and denatured states, the free energy G(z) is typically a monotonic function of the mechanical coordinate z equal to the protein extension. Application of a stretching force along z tilts the free-energy landscape resulting in a bistable (or multistable) free energy G(z)-fz probed in mechanical unfolding experiments. We construct a two-dimensional free-energy surface as a function of both chemical and mechanical reaction coordinates and examine the coupling between the two. We further study the refolding trajectories after the protein has been prestretched by a large force, as well as the mechanical unfolding trajectories in the presence of a large stretching force. We demonstrate that the stretching forces required to destabilize the native state thermodynamically are larger than those expected on the basis of previous experimental estimates of G(z). This finding is consistent with the recent experimental studies, indicating that proteins may refold even in the presence of a substantial stretching force. Finally, we show that for certain temperatures the free energy of a polyprotein chain consisting of multiple domains is a linear function of the chain extension. We propose that the recently observed "slow phase" in the refolding of proteins under mechanical tension may be viewed as downhill diffusion in such a linear potential.     

Measuring Contact Angles at Copper Electrodes

Potential dependences of the angle of contact between perfluorodecaline C₁₀F₁₈ and copper, copper(I) sulfide, and copper telluride Cu₄Te₃ in 0.1 M CH₃COONa are measured. The data are in good agreement with the metal hardness measured in 1 M KOH. The uncharged-surface potentials (USP) for copper, copper(I) sulfide, and copper telluride equal 0.05–0.07, –0.02 to –0.04, and 0.05–0.07 V (NHE) in 0.1 M CH₃COONa. Studying the effect of Br^– ions shows that USP for copper and Cu₂S shift in, respectively, the negative and positive directions with an increase in [Br^–]. For copper telluride, USP shifts in the positive direction at low Br^– concentrations, and at NaBr concentrations in excess of 0.04 M, in the negative direction.     

1,2-Diisophthalimidoethane. X-ray diffraction evidence for the structure of the product of acylation of 1,2-diaminoethane with phthaloyl chloride

It was demonstrated by x-ray diffraction investigation of the product of the reaction of 1,2-diaminoethane with phthalic acid dichloride that the resulting compound has the 1,2-diisophthalimidoethane structure. An improved method for its synthesis is proposed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1320–1323, October, 1987.     

Gas phase photoreaction of SO2 with n-pentane in the presence of NO

The spectrum of an intermediate, ascribed to nitrosopentane, has been detected in the photolysis of SO₂-pentane-NO mixtures. This may be explained by a radical photolysis mechanism involving an initial H-atom abstraction from the pentane molecule by SO₂.

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SO₂--NO , . , H .

     

Nature of the activity and the kinetics of cyclohexene hydrogenation by the catalytic system (C5H5)2 TiCl2?LiC4H9

The reaction of tributylphosphine with the catalytic system (C₅H₅)₂ TiCl₂–LiC₄H₉ prepared in an atmosphere of H₂ has been investigated in toluene solution. By using the ESR technique, a hydride complex Cp₂Ti(H) (PBu₃) has been detected. The proportionality between the rate of cyclohexene hydrogenation and the complex concentration has been established. The kinetics of cyclohexene hydrogenation has been investigated and a reaction mechanism is proposed.

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Cp₂TiCl₂–LiC₄H₉ (Cp–C₅H₅), H₂, Cp₂Ti(H) (PBu₃). Ti (III). .

     

Difference schemes for the dirichlet problem for an elliptical equation with discontinuous coefficients in an arbitrary region on a regular grid

Exact difference scheme operators are used to construct a difference scheme for a second-order elliptical equation with discontinuous coefficients. The solution of the scheme converges to the solution of the original problem at a rate O(h^1/2) in the grid norm W₂ ¹().Translated from Vychislitel'naya i Prikladnaya Matematika, No. 56, pp. 3–7, 1985