Reaction of Methyl (2-Methylidene)-3-oxolup-20(29)-en-28-oate with Dimethyl Trimethylsilyl Phosphite

Russian Journal of General Chemistry - A method of phosphorylation of pentacyclic triterpenoids derivatives containing an α,β-unsaturated carbonyl fragment in the ring A was described by...     

Interaction of cathode plasma with the cathode surface in an electron source with explosive electron emission

The interaction of the plasma formed at emission centers of an electron source using explosive electron emission with the cathode surface is studied. It is found that the plasma flux does not flow around obstacles located in its path and is effectively deionized upon incidence on the wall.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 26–29, November, 1981.     

Antisite defects and valence state of vanadium in Na<Subscript>3</Subscript>V<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript>

Electron paramagnetic resonance (EPR) studies have been performed with the aim of determining the valence state and local crystal structure of the nearest environment of vanadium ions in the initial, charged, and discharged samples of the cathode material Na_xV₂(PO₄)₃ (1 ≤ x ≤ 3). It has been found that the charged sample (x = 1) is characterized by an intense signal corresponding to V⁴⁺ ions located in a highly distorted octahedral crystal field. An EPR signal with the g-factor close to the g-factor of the V⁴⁺ ion has also been observed in the initial sample (x = 3), where the intensity of the resonance signal is one order of magnitude lower than that in the charged sample. It has been revealed that the resonance signal under consideration is associated with the formation of antisite defects when a part of vanadium ions are located in sites of sodium ions. It has also been found that the intensity of this signal increases after a complete charge–discharge cycle (x = 3).     

Reaction of apple pectin modified by pharmacophores,with copper(II) cations

The reaction of apple pectin modified by organic pharmacophores (nicotinic, salicylic, 5-aminosalicylic, and anthranilic acids) with Cu(II) cations was studied by spectral methods. The compositions of the complexes were determined and their stability constants, as well as the thermodynamic parameters (ΔH ⁰, ΔG ⁰, ΔS ⁰) of the complex formation were calculated. The structure of the drug in the polymeric ligand was found to affect certain physicochemical properties of the metal complexes.     

New functionalized pyrrolidines

New functionalized pyrrolidines have been synthesized from accessible amino acids by the [C+NC+CC]-coupling reaction.     

Synthesis and proliferative activity of a new derivative of the lupan pentacyclic triterpenoids, <Emphasis Type="Italic">viz.</Emphasis>, the sulfobetaine based on betulin with a 4-(dimethylammonio)butane-1-sulfonate moiety

A new zwitterionic derivative of the lupan pentacyclic triterpenoid series, viz., the sulfobetaine with a 4-(dimethylammonio)butane-1-sulfonate moiety, was synthesized by quaternization of betulin 28-(2-dimethylaminoacetate) with 1,4-butane sultone. The sulfobetaine was found to possess a dose-dependent proliferative effect toward human embrionic kidney cells HEK293 and human T-lymphocytes. Betulin chosen as a comparison compound demonstrated an effect against cells of both the tumor (HepG2, Jurkat) and the normal origin (human HEK293 and T-lymphocytes) which differ from that of the sulfobetaine, inhibiting their proliferation. The new sulfobetaine can prove to be a promising basis for the development of reparative and immunostimulating agents.     

Geometric model-based fitting algorithm for orientation-selective PELDOR data

Pulsed electron–electron double resonance (PELDOR or DEER) spectroscopy is frequently used to determine distances between spin centres in biomacromolecular systems. Experiments where mutual orientations of the spin pair are selectively excited provide the so-called orientation-selective PELDOR data. This data is characterised by the orientation dependence of the modulation depth parameter and of the dipolar frequencies. This dependence has to be taken into account in the data analysis in order to extract distance distributions accurately from the experimental time traces. In this work, a fitting algorithm for such data analysis is discussed. The approach is tested on PELDOR data-sets from the literature and is compared with the previous results.     

Approximate calculation of current in a diode with an explosive emission cathode

The approximation of electron motion along electric field force lines is used to calculate current in diodes with knife-edge and point emitters. The diode current is limited by space charge, with each current tube considered as a diode element with electrodes in the form of coaxial cylinders or concentric spheres. The effect of the cathode cavity in which the emitter is installed upon current magnitude is considered by limiting beam dimensions at the anode.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 3–6, February, 1992.