Dry HCl in parallel synthesis of fused pyrimidin-4-ones

The parallel solution-phase synthesis of substituted thieno[2,3- d]pyrimidin-6-carboxylic acids has been accomplished. This strategy relies on a cyclization of 2-aminothiophen-3,5-dicarboxylates with a set of nitriles, followed by hydrolysis to construct the library of corresponding acids. The convenient procedure for use and dosage of dry HCl for the reaction was elaborated and adapted for semiautomated solution-phase parallel synthesis. With the use of another (hetero)aromatic ortho-aminocarboxylate, mini-libraries of diverse fused pyrimidin-4-ones were synthesized. The scope and limitations of the approach are discussed.     

Synthesis of nanocrystalline titanium dioxide films in a cylindrical magnetron-type gas discharge and their optical characterization

The plasma-dynamic and spectral characteristics of a cylindrical magnetron-type gas discharge are studied experimentally. The radiation spectrum of the plasma is recorded in real time in the range 350–820 nm. Appropriate conditions for synthesis of TiO₂ binary compound are found. They are provided by maintaining the intensities of the spectral lines of reactants and a plasma-forming gas at a desired level. The feasibility of monitoring the TiO₂ film synthesis conditions from the spectral characteristics of the discharge plasma and from the variation of the discharge voltage is considered. Ellipsometric and spectral data for nanocrystalline titanium dioxide films indicate that the refractive index of the film depends on its thickness.     

Neutral and Negatively Charged Phosphate Modifications Altering Thermal Stability,Kinetics of Formation and Monovalent Ion Dependence of DNA G‐Quadruplexes

The effect of phosphate group modifications on formation and properties of G‐quadruplexes (G4s) has not been investigated in detail. Here, we evaluated the structural, thermodynamic and kinetic properties of the parallel G‐quadruplexes formed by oligodeoxynucleotides d(G₄T), d(TG₄T) and d(TG₅T), in which all phosphates were replaced with N‐methanesulfonyl (mesyl) phosphoramidate or phosphoryl guanidine groups resulting in either negatively charged or neutral DNA sequences, respectively. We established that all modified sequences were able to form G‐quadruplexes of parallel topology; however, the presence of modifications led to a decrease in thermal stability relative to unmodified G4s. In contrast to negatively charged G4s, assembly of neutral G4 DNA species was faster in the presence of sodium ions than potassium ions, and was independent of the salt concentration used. Formation of mixed G4s composed of both native and neutral G‐rich strands has been detected using native gel electrophoresis, size‐exclusion chromatography and ESI‐MS. In summary, our results indicate that the phosphate modifications studied are compatible with G‐quadruplex formation, which could be used for the design of biologically active compounds.     

Use of a one-parameter family of Gordon–Schowalter objective derivatives to describe finite strains of viscoelastic bodies

A constitutive relation is considered for viscoelastic materials at finite strains. This relation is obtained using a one-parameter family of Gordon–Schowalter objective derivatives and generalizes the elementary Maxwell model. It is shown that, in the problem of simple shear of an incompressible viscoelastic material, this constitutive relation allows one to obtain the Poynting effect for any parameters of the model.     

Electronic states of dysprosium submonolayer films adsorbed on the W(100) surface

The unfilled electronic states of dysprosium submonolayer films absorbed on the W(100) surface are investigated using angle-resolved inverse photoelectron spectroscopy. It is shown that the energy position of the peak at 1.7 eV is independent of the angle of incidence of electrons onto the crystal surface. This specific feature is associated with electron transitions to the Dy 4f state located above the Fermi level. A correlation between the change in the energy position of this peak and the change in the work function with an increase in the absorbed dysprosium coverage suggests that the dipole moment of adatoms is affected by the dipole-dipole interaction.     

Study of fossil tracks due to VH and VVH groups of cosmic ray nuclei in olivine crystals from Luna-16 and Luna-24

The olivine crystals from lunar regolith samples taken by the Soviet unmanned spacecrafts Luna-16 and Luna-24 were investigated. Eleven 0.5 –1.0 mm size olivine crystals were mounted in epoxy, polished and then etched in modified WO₄ solution. The Fe-group track densities up to 10⁸ tracks.cm⁻² (Fe-group) were measured under optical microscope. The tracks of length greater than 30 microns due to Z ≥ 36 cosmic ray nuclei are counted for VVH tracks density for all the crystals. The VVH / VH track densities ratio for these lunar olivine crystals varies from 1.25×10⁻⁴ to 2×10⁻³. It corresponds to the averaged depth of these crystals in lunar soil of 2–8 cm during galactic cosmic ray exposure. Lunar crystals are well suited for VVH track studies due to a very high track density. Two crystals were annealed at 430°C for 32 hrs. This procedure eliminates iron group tracks completely and leaves etchable tracks of nuclei with Z 50 even in the olivine crystals with Fe-group tracks up to 1–2×10⁸ tracks cm⁻². We were able to measure two tracks with the length 195 and 210μm which were produced by Th---U group of Galactic cosmic ray nuclei.     

Oligonucleotides with 2'-O-carboxymethyl group: synthesis and 2'-conjugation via amide bond formation on solid phase

An efficient method for synthesis of oligonucleotide 2'-conjugates via amide bond formation on solid phase is described. Protected oligonucleotides containing a 2'-O-carboxymethyl group were obtained by use of a novel uridine 3'phosphoramidite, where the carboxylic acid moiety was introduced as its allyl ester. This protecting group is stable to the conditions used in solid-phase oligonucleotide assembly, but easily removed by Pd(0) and morpholine treatment. 2'-O-Carboxymethylated oligonucleotides were then efficiently conjugated on a solid support under normal peptide coupling conditions to various amines or to the N-termini of small peptides to give products of high purity in good yield. The method is well suited in principle for the preparation of peptide-oligonucleotide conjugates containing an amide linkage between the 2'-position of an oligonucleotide and the N-terminus of a peptide.     

The investigation of magnetic state variations in α-Fe and its alloys by means of continuous temperature scanning of the Mössbauer effect

A new method for continuous temperature scanning of the Mössbauer effect was developed permitting the measurement in a broad temperature range with satisfactory precision. The temperature dependence of Mössbauer radiation transmission for -Fe, amorphous Fe-P and for alloys was measured from 20–800°C. A region of anomalous transmission was observed for crystalline -Fe and its alloys and a new method of Debye-temperature determination was proposed.