Ligand exchange chromatography for analysis and preparative separation of tritium-labelled amino acids

Racemic tritium-labelled amino acids were separated into optical isomers by chromatography on a chiral polyacrylamide sorbent filled with copper ions. The polyacrylamide sorbent is synthesized by Mannich's reaction through the action of formaldehyde and L-phenylalanine upon polyacrylamide Biogel P-4 in an alkali phosphate buffer. Tritiumlabelled amino acids are eluted by a weak alkali solution of ammonium carbonate. Data are presented on the ligand exchange chromatography of amino acids depending on the degree to which the sorbent is filled with copper ions and on the eluent concentration. Conditions are suggested for the quantitative separation of amino acid racemates. Amino acids are isolated from the eluent on short columns filled with sulfonated cation exchanger in the H⁺ form. HPLC on modified silica gel sorbents is also used for the analysis of tritium-labelled optically active amino acids. Amino acids are eluted by a weakly acidic water-methanol solution containing ammonium acetate. UV and scintillation flow type detectors are used.     

Enzyme self-inactivation is a main limitation of the preparation of eicosanoids

Synthesis of prostanoids is accompanied by various processes reducing the product yield. These processes are also known to affect syntheses of thromboxane (TX) and 12(S)-hydroxy-5(Z),8(Z),10(E),14(Z)-eicosatetraenoic acid (12-HETE). Partially purified preparations of TX synthase and prostaglandin (PG) synthase were used to optimize TX synthesis with respect to concentrations of the enzymes and eicosapolyenoic acid (EPA). Conditions for the maximum product yield and the minimum consumption of enzymes were determined. Consumption of the TX synthase was large owing to its inactivation during the reaction and the nonenzymatic destruction of the intermediate product PG-endoperoxide. Separate addition of PG and TX synthases increased the product yield by preventing EPA sorption on ballast proteins. Microsomal 12-lipoxygenase (12-LO) was also shown to be inactivated during the reaction, and this process was the major limitation of 12-HETE synthesis. Lipoxygenase reaction in the presence of some reducing agents led to a considerable increase of the 12-HETE yield, supposedly by preventing further oxidation of the 12-LO reaction product 12-hydroperoxy derivative of eicosatetraenoic acid. The possibility of using human blood platelet microsomes for preparation of some derivatives of EPAs is discussed.     

A NEW FINITE ELEMENT APPROXIMATION OF A STATE-CONSTRAINED OPTIMAL CONTROL PROBLEM

In this paper, we study numerical methods for an optimal control problem with pointwise state constraints. The traditional approaches often need to deal with the deltasingularity in the dual equation, which causes many difficulties in its theoretical analysis and numerical approximation. In our new approach we reformulate the state-constrained optimal control as a constrained minimization problems only involving the state, whose optimality condition is characterized by a fourth order elliptic variational inequality. Then direct numerical algorithms （nonconforming finite element approximation） are proposed for the inequality, and error estimates of the finite element approximation are derived. Numerical experiments illustrate the effectiveness of the new approach.     

Multiple tritium labelling of thymine and its derivatives

The paper deals with the synthesis of thymine and its derivatives carrying the label at C(6) in the pyrimidine in the methyl group and in deoxy-d-ribose. The molar activity of the preparations ranges from 0.85 to 4.94 PBq/mol. A procedure is proposed for obtaining tritium-labelled thymine compounds: nucleoside, nucleoside mono-, di- and triphosphates.     

Local observations of phase singularities in optical fields in waveguide structures

A linear copolymer made of two reciprocally attracting N-monomer blocks collapses to a compact phase through a novel transition, whose exponents are determined with extensive Monte Carlo simulations in two and three dimensions. In the former case, an identification with the statistical geometry of suitable percolation paths allows one to predict that the number of contacts between the blocks grows like N9/16. In the compact phase the blocks are mixed and, in two dimensions, also zipped, in such a way to form a spiral, double chain structure.     

Influencing the angular emission of a single molecule

We present the first experimental proof for the influence of a nearby nanosized metal object on the angular photon emission by a single molecule. Using a novel angular sensitive detection scheme, we directly quantify the redirection of angular emission for different molecular dipole orientations as an object is scanned laterally over the molecule at different heights. An excellent agreement between experiments and 2D-numerical simulations is found for molecules oriented perpendicular to the sample, whereas, for parallel orientations, the observed behavior contradicts the calculated behavior.     

ACTH(6–9)PGP Peptide Protects SH-SY5Y Cells from H2O2, tert-Butyl Hydroperoxide,and Cyanide Cytotoxicity via Stimulation of Proliferation and Induction of Prosurvival-Related Genes

Stabilized melanocortin analog peptide ACTH(6–9)PGP (HFRWPGP) possesses a wide range of neuroprotective activities. However, its mechanism of action remains poorly understood. In this paper, we present a study of the proproliferative and cytoprotective activity of the adrenocorticotropic hormone fragment 6–9 (HFRW) linked with the peptide prolyine–glycyl–proline on the SH-SY5Y cells in the model of oxidative stress-related toxicity. The peptide dose-dependently protected cells from H₂O₂, tert-butyl hydroperoxide, and KCN and demonstrated proproliferative activity. The mechanism of its action was the modulation of proliferation-related NF-κB genes and stimulation of prosurvival NRF2-gene-related pathway, as well as a decrease in apoptosis.     

Enzymic synthesis of nucleic acid components carrying label in the nitrogen base and in the ribose part of the molecule

The paper describes an enzymic method for obtaining labelled components of nucleic acids—nucleosides and nucleotides—in reactions catalyzed by a polyenzymic preparation from E. coli B. The method enables highly labelled nucleotides to be obtained through the use of precursors carrying the label at positions unaffected in biosynthesis.