Synthesis of 5-Hydroxymethyl-8-methyl-3-(3-aryl-[1,2,4]oxadiazol-5-yl)-2H-pyrano[2,3-c]pyridin-2-ones and Their Esters

New 5-hydroxymethyl-8-methyl-3-(3-aryl-[1,2,4]oxadiazol-5-yl)-2H-pyrano-[2,3-c]pyridin-2-ones and their esters were synthesized. The structure of obtained compounds was determined through a complete ¹H NMR analysis.     

Photohemolysis sensitized by the furocoumarin imperatorin and its oxyfunctionalized derivatives

The dark and photosensitized (366 nm) hemolytic effects of imperatorin and its photooxidation products, the hydroperoxides I and II as well as the corresponding alcohol of the hydroperoxide I (imperatorin alcohol), were studied on human erythrocytes. Imperatorin was shown to photosensitize hemolysis, its fluence (D) dependence of the rate of photohemolysis (V) followed the equation V = V0 + aD2 + bD1/2, in which V0 is the dark hemolysis rate and a and b are constants. At fluences below 200 kJ/m2, the main hemolytic contribution derives from the bD1/2 component, which is due to the in situ formation of the imperatorin hydroperoxides, while at fluences higher than 200 kJ/m2, the main contribution corresponds to the aD2 component due to the two-photon damage of cell membranes. Hydroperoxides I and II induce oxyhemoglobin cross-linking, as well as its conversion to methemoglobin and hemichrome. These reactions involve hydroxyl and alkoxy radicals, as the hemolysis and oxyhemoglobin conversion could be inhibited by t-butanol and butylated hydrotoluene. For comparison, the dark hemolytic effect of the imperatorin alcohol was approximately 10-fold less than of the hydroperoxides.     

Dendronized protein polymers: synthesis and self-assembly of monodisperse cylindrical macromolecules

Monodisperse dendronized protein polymers (DPPs), cylindrical dendrimers containing protein core, can be efficiently produced through a combined modular biosynthetic strategy. These DPP materials possess predictable size, shape, and solubility. In organic solutions, the DPPs self-assemble to form highly ordered liquid crystalline structures with nanoscale order controlled by their exact molecular dimensions.     

Suppression of Delayed-type Hypersensitivity and Hemolysis Induced by Previously Photooxidized Psoralen: Effect of Fluence Rate and Psoralen Concentration

Abstract— The kinetics of the formation of biologically active psoralen photooxidation (POP) products were analyzed by the biological effects produced. Effects of the UV light fluence rate and psoralen concentration during the preir-radiation were investigated to assess the yield of POP products, which were active in vivo (inducing suppression of delayed-type hypersensitivity [DTH] reaction to sheep red blood cells) and in vitro (altering the human erythrocyte membrane permeability). It was shown that the reciprocity law of the irradiation fluence rate and time was not valid in the case of POP-induced hemolysis and DTH suppression. Immunosuppressive POP products were more efficiently formed at low fluence rate (20.8 W/m²), whereas POP hemolysins were more efficiently produced at a high fluence rate (180 W/m²) of UV light. The yield of immunosuppressive POP products was enhanced in dilute psoralen solutions, while the POP hemolysins yield increased with increasing psoralen concentration. A kinetic scheme for psoralen photoproduct formation was proposed. Kinetic analysis showed that a labile intermediate was produced as the result of excitation of psoralen. This intermediate was either converted to a stable immunosuppressive POP product, or two intermediates combined to form a POP hemolysin. It is proposed that PUVA therapy conditions are more favorable for the formation of immunosuppressive rather than membrane-damaging psoralen photooxidation products.     

Spectrum evolution at the transition to turbulance in a couette flow

It is shown that the laminar-turbulent transition in a circular Couette flow combines characteristics of both Landau and stochastic attractor models. As the Reynolds number increases new modes are excited and the peaks of the spectrum are broadened smoothly.     

Recyclization of 2-iminocoumarins using nucleophilic reagents. 6. Reaction of 2-iminocoumarin-3-carboxamides with 2-aminobenzophenones

It has been shown that the reaction of 2-iminocoumarin-3-carboxamides with substituted 2-aminobenzophenones occurs in accordance with recyclization mechanism to form substituted 3-(4-phenylquinazolin-2-yl)coumarins. The structure of the compounds obtained was confirmed by spectroscopic data and by X-ray analysis.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1533–1542, October, 2004.