Efficient conjugation and preferential DNA binding of oligonucleotides containing 2′-O-(2-oxoethyl)arabinouridine

Oligodeoxyribonucleotides were synthesized that contain a novel nucleoside, 2′-O-(2-oxoethyl)arabinouridine. Whereas such oligonucleotides showed only a slight reduction in the T_M values of their complexes with complementary DNA, a significant destabilization was observed in the case of duplexes formed with RNA. This may be explained by the C_2′-endo conformation of 2′-O-(2,3-dihydroxypropyl)arabinouridine as demonstrated by NMR experiments in D₂O. The modified oligonucleotides were used to synthesize a number of conjugates with dyes, biotin and a N-modified laminin peptide, by hydrazone and oxime formation. We suggest that the 2′-arabinoaldehyde-containing DNA duplexes may be valuable tools for affinity modification of DNA-binding proteins.     

Plasma Synthesis and XPS Attestation of Thin-Film Carbon Coatings with Predetermined sp-Hybridization

Physics of Atomic Nuclei - The diversity of carbon materials has allowed them to be used for fundamental and applied research to date. The newest modifications of carbon, such as nanodiamonds,...     

Configurations and local vibrations of differently charged oxygen vacancies in quartz crystal

We have studied local configurations and vibration states of oxygen vacancies in different charge states in α-quartz. The local atomic structure and the lattice dynamics have been simulated using first-principles potentials of the Buckingham type. The effect of defects on the vibration spectrum of α-quartz has been studied by calculating the local densities of vibrational states.     

Formation and electron-beam annealing of implantation defects in a thin-film Si-SiO2 heterostructure

Technical Physics - The radiation-induced defects in a 20-nm-thick SiO2 film on a silicon wafer are studied by optically stimulated electron emission. Accelerated (12-keV) silicon ions is found to...     

Nonradiative relaxation of photoexcited O<Stack><Subscript>1</Subscript><Superscript>0</Superscript></Stack> centers in glassy SiO<Subscript>2</Subscript>

The processes involved in the excited-state relaxation of hole O ₁ ⁰ centers at nonbridging oxygen atoms in glassy SiO₂ were studied using luminescence, optical absorption, and photoelectron emission spectroscopy. An additional nonradiative relaxation channel, in addition to the intracenter quenching of the 1.9-eV luminescence band, was established to become operative at temperatures above 370 K. This effect manifests itself in experiments as a negative deviation of the temperature-dependent luminescence intensity from the well-known Mott law and is identified as thermally activated external quenching with an energy barrier of 0.46 eV. Nonradiative transitions initiate, within the external quenching temperature interval, the migration of excitation energy, followed by the creation of free electrons. In the final stages, this relaxation process becomes manifest in the form of spectral sensitization of electron photoemission, which is excited in the hole O ₁ ⁰ -center absorption band.     

Electronic excitations and defects in nanostructural Al<Subscript>2</Subscript>O<Subscript>3</Subscript>

A time-resolved cathodo-and photoluminescence study of nanostructural modifications of Al₂O₃ (powders and ceramics) excited by heavy-current electron beams, as well as by pulsed synchrotron radiation, is reported. It was found that Al₂O₃ nanopowders probed before and after Fe⁺ ion irradiation have the same phase composition (the γ-phase/δ-phase ratio is equal to 1), an average grain size equal to ～17 nm, and practically the same set of broad cathodoluminescence (CL) bands peaking at 2.4, 3.2, and 3.8 eV. It was established that Al₂O₃ nanopowders exhibit fast photoluminescence (PL) (a band at 3.2 eV), whose decay kinetics is described by two exponential stages (τ₁ = 0.5 ns, τ₂ = 5.5 ns). Three bands, at 5.24, 6.13, and 7.44 eV, were isolated in the excitation spectrum of the fast PL. Two alternate models of PL centers were considered, according to which the 3.2-eV luminescence either originates from radiative relaxation of the P^? centers (anion-cation vacancy pairs) or is due to the formation of surface analogs of the F⁺ center (F _S ⁺ -type centers). In addition to the fast luminescence, nano-Al₂O₃ was found to produce slow luminescence in the form of a broad band peaking at 3.5 eV. The excitation spectrum of the 3.5-eV luminescence obtained at T = 13 K exhibits two doublet bands with maxima at 7.8 and 8.3 eV. An analysis of the luminescent properties of nanostructural and single-crystal Al₂O₃ suggests that the slow luminescence of nanopowders at 3.5 eV is due to radiative annihilation of excitons localized near structural defects.