Separation of unmodified α-amino acid enantiomers by reverse phase HPLC

Summary A novel chiral phase system is presented for the resolution of unmodified α-amino acid racemates which is composed of a reverse phase packing coated with N-alkyl-L-hydroxyproline (where alkyl is n-C₇H₁₅-, n-C₁₀H₂₁- and n-C₁₆H₃₃-) and a hydro-organic eluent containing copper(II)acetate. The factors controlling retention and enantioselectivity such as concentration of Cu(II)ion and pH of the eluent, addition of NH₄Ac to the eluent, type and content of organic solvent of hydro-organic eluent and column temperature were examined. The extremely high enantioselectivity observed (α up to 16) is assumed to be caused by a three site sorbate-sorbent interaction involving bidentate coordination of two amino acids to a Cu(II)ion and hydrophobic attractions between hydrocarbon side chains of amino acids and the n-octadecyl groups of the support. The efficiency and selectivity of the system permits resolution of up to 7 racemic amino acids into enantiomers within 35 minutes on a conventional HPLC apparatus. 13th publication in the series dealing with the ligand-exchange chromatography. Previous publication: ref. [1].     

Development and Validation of the Quantification of GML-1 Compound (<Emphasis Type="Italic">N</Emphasis>-benzyl-<Emphasis Type="Italic">N</Emphasis>-methyl-1-phenylpyrrolo[1,2-<Emphasis Type="Italic">A</Emphasis>] pyrazine- 3-carbamide) in the Blood Plasma of Rats by HPLC–MS

The technique of quantitative determination of a new compound, possessing anxiolytic activity, GML-1 in the blood plasma of rats is developed and validated. The analysis is performed by HPLC–MS. The method is linear in the range of 50–1000 ng/mL. 83.63% of GML-1 was recovered. The detection limit was 25 ng/mL.     

The effect of 3d-metal intercalation on the electronic structure of metallic and semiconducting nanotubes

The electronic structure of 3d-metal-intercalated metallic (5,5) and semiconducting (10,0) nanotubes has been studied by quantum-chemical methods. The total and partial densities of states of nanotubes as a function of metal concentration and nature and the carbon-shell structure have been calculated by the linear augmented-cylindrical-wave method. Metalized nanowires based on armchair (5,5) and zigzag (10,0) nanotubes with one, two, three, and four metal atoms in the cross-section have been calculated. The introduction of the metal is accompanied by a sharp increase in the density of states at the Fermi level of the nanowire, which determines the concentration of free electrons involved in charge transfer in the nanotube. The 3d electrons of the metal and the carbon shell are nearly equally involved in electron transport in intercalated wires. Both the 3d electrons of a metal and the carbon shell should be nearly equally involved in electron transport in intercalated wires. The introduction of metals not only affects the conductive state of the carbon nanotube but also changes the entire pattern of its valence band, in particular, increases the valence band width of the nanotube by 5–10 eV owing to the low-energy shift of the 2s(C) states.     

Generalized Rayleigh Criterion of Two-Point Resolution

We propose a criterion of resolution of one-type incoherent signals with respect to two scalar parameters and estimate the corresponding resolution limits. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 48, No. 5, pp. 441–445, May 2005.     

Coumarinyl(thienyl)thiazoles: novel photochromes with modulated fluorescence

Novel photochromic 5-(3'-coumarinyl)-4-(3'-thienyl)thiazoles have been synthesized. These compounds display intensive fluorescence emission in the open form A, which is modulated by light. Fluorescence intensity decreases significantly upon irradiation of A with UV-light (lambda<400 nm) due to formation of the cyclic form B. Irradiation of B with visible light (lambda>470 nm) promotes its opening and the recovering of fluorescence. Novel dihetarylethenes undergo photochromic modulation of fluorescence both in solution and in polymeric matrices.     

New reactions, functional compounds, and materials in the series of coumarin and its analogs

Data on the development of new functional compounds and materials based on the study of the reactions of coumarin and its analogs are generalized. Since coumarin derivatives are characterized by enhanced photochemically activity, special attention is given to the synthesis of photosensitive compounds and materials with intense fluorescence, including the structures capable of changing fluorescence under the action of various factors: solvent, pH of the medium, and interaction with bioorganic substrates. Pathways for design of fluorescent polymethine dyes, fluorescent labels for proteins, fluorescent photochromes, and photoacids for optical data storage with fluorescence read-out are reviewed. The role of isomerization transformations of the new compounds in their sensorial effects is established.     

Identification of novel liver X receptor activators by structure-based modeling

Liver X receptors (LXRs) are members of the nuclear receptor family. Activators of LXRs are of high pharmacological interest as LXRs regulate cholesterol, fatty acid, and carbohydrate metabolism as well as inflammatory processes. On the basis of different X-ray crystal structures, we established a virtual screening workflow for the identification of novel LXR modulators. A two-step screening concept to identify active compounds included 3D-pharmacophore filters and rescoring by shape alignment. Eighteen virtual hits were tested in vitro applying a reporter gene assay, where concentration-dependent activity was proven for four novel lead structures. The most active compound 10, a 1,4-naphthochinone, has an estimated EC?? of around 5 μM.     

On some relations in the generalized Boltzmann-Enskog model

The generalized Boltzmann-Enskog equation with long-range potential which was considered to be approximate is proved to possess exact microscopic solutions. Solutions corresponding to a small periodical disturbance of the distribution function are studied. Corrections to the sound velocity are determined.     

Synthesis of certain derivatives of β-ethylthio-D-glucopyranoside

Conclusions We have synthesized the benzylidene derivative, its esters, and 2,3-di-O-benzoate of-ethylthio-D-glucopyranoside.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 179–180, January, 1968.