Raman spectroscopy of topotecan, an inhibitor of DNA topoisomerase I

Topotecan (TPT), a water-soluble derivative of camptothecin (inhibitor of human DNA topoiomerase I), has found wide application in cancer chemotherapy. The central problem in using topotecan is the presence of lactone rings in its molecules, which undergo hydrolysis at a physiological pH yielding an inactive and even toxic form of the drug. The analysis of Raman spectra of TPT in H₂O and D₂O solutions made it possible to assign the spectral bands to the vibrations of particular molecular groups. Spectral features indicative of the opening of the lactone rings of the TPT molecules, deprotonation of the hydroxyl groups in their quinoline fragments, and of possible participation of the hydroxyl and carbonyl groups in H bonding are found. The data obtained are necessary to study the molecular mechanisms of TPT-DNA interaction and the formation of ternary complexes between TPT, DNA, and DNA topoisomerase I.     

Charge states of inert gas ions in lunar ilmenites

Fractionation of particles of solar corpuscular radiation significantly changes from flare to flare; therefore the average regularities derived from the contents of inert gases in lunar samples of different cosmicray exposure age are of particular importance. Simulation of the charge states of inert gas ions (Ne, Ar, Kr, and Xe) in lunar ilmenites suggests possibility of higher solar flare activity and higher hardness of the solar proton spectrum ～1 billion years ago.     

Polyketide exometabolites of the causative agent of rice blast and their role in pathogenesis

A polyketide exometabolite — 3,4,8-trihydroxy-3,4-dihydronaphthalen-1(2H)-one (3,4,8-TDH) — has been isolated from the culture liquids of four isolates of the phytopathogenic fungusPiricularia oryzae Cavara. It has been shown that all the natural isolates investigated, and also nonpathogenic rose mutants and a series of dwarf mutants synthesize 3,4,8-TDH. This substance was not detected in filtrates of cultures of albino mutants. One of the natural isolates produces, together with 3,4,8-TDH, another polyketide — piriculol. The role in pathogenesis of the exometabolites isolated is discussed.All-Union Scientific-Research Institute of Phytopathology of Gosagroprom SSR. Golitsyno. V. I. Lenin Tashkent State University. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 572–577, July–August, 1988.     

Synthesis and piezoelectric properties of <Emphasis Type="Italic">N</Emphasis>-phthaloylglutamic acid derivatives

The (S,S)- and (R,R)-enantiomers of dimethyl 2,4-diphthalimidoglutarate were synthesized by nucleophilic substitution of bromine in dimethyl (2S,4RS)-4-bromo-N-phthaloyl-glutamate upon treatment with potassium phthalimide, followed by separation. The crystal structure of the obtained compounds was studied by X-ray diffraction. Crystals of enantiomerically pure dimethyl 4-hydroxy- and 4-phthalimido-N-phthaloylglutamates were found to possess a noticeable piezoelectric activity.     

Synthesis of meta-Carboranyl-(S)-homocysteine Sulfoxide

Russian Journal of Organic Chemistry - New (S)-homocysteine derivatives containing a meta-carborane fragment were synthesized. m-Carboranyl-(S)-homocysteine sulfoxide was obtained as a mixture of...     

Patterns of cosmogenic radionuclide production rates in the heliosphere and problems of solar modulation on a long time scale

The results of long-term studies of cosmogenic radionuclide production rates along the orbits of 39 chondrites that fell to the Earth between 1959 and 2013 are presented. They constitute a long series of homogeneous data, a statistical smoothing of which demonstrate some general patterns of the distribution and variations of Galactic cosmic rays (GCRs) with energy >100 MeV in the inner (<5 AU) heliosphere. A correlation analysis of the production rates of radionuclides with different half-lives suggests that the solar GCR modulation mechanism is constant over at least ~1 million years. The role of stochastic factors in the polarity reversal of the general solar magnetic field for the phases of maximum solar activity has been revealed. The subtle sensitivity of the ⁵⁴Mn production rate in the Chelyabinsk chondrite to the short-term closure of the heliosphere for positively charged particles over 14 months between June 2012 and July 2013 is used as an example to show the high resolution of the method of using cosmogenic radionuclides in meteorites as natural GCR detectors.     

Pressure dependences of electroresistance,magnetoresistance, and the thermoelectromotive force in CuInSe2 and CuInS2

The effects of high pressures on the electrical properties of the polycrystalline CuInSe₂ and CuInS₂ are studied. The resistance, magnetoresistance, thermoelectromotive force, impedance, admittance and loss tangent in high-pressure phases are estimated. The baric ranges of substantial changes in the behavior of all the investigated characteristics are determined.     

Viscosimetric flow of an incompressible elastoviscoplastic material under the presence of a lubricant on the boundary surfaces

Generalizing the model of large deformations by accounting for the viscous properties of materials, we obtain the analytical solutions of some quasistatic boundary value problems concerning the viscosimetric flows of an elastoviscoplastic material in the gap between the rigid coaxial cylindrical surfaces when, in the neighborhood of one of the rigid cylinders (either internal or external), there is a layer of an elastic non-Newtonian lubricant, and the rigid adhesion conditions are satisfied on boundary surfaces. The conditions are studied of origination of a flow in the lubricant layer and in the basic material. The values of the maximum velocity are specified under which the flow does not tresspass the lubricant layer.