V. M. Fedoseev

Synthesis and study of NOS-inhibiting activity of 2-N-acylamino-5,6-dihydro-4H-1,3-thiazine

The synthesis and results of in vitro and in vivo testing of 2-N-acetylamino-, 2-N-benzoylamino-,2-N-cyclohexanecarbonylamino-, and 2-N-(1-adamantanecarbonyl)amino-5,6-dihydro-4H-1,3-thiazines for NOS-inhibiting activity have been described.

Structure and activity of NO synthase inhibitors specific to the L-arginine binding site

Synthesis of compounds containing a fragment similar to the guanidine group of L-arginine, which is a substrate of nitric oxide synthase (NOS), is the main direction in creating NOS inhibitors. The inhibitory effect of such compounds is caused not only by their competition with the substrate for the L-arginine-binding site and/or oxidizing center of the enzyme (heme) but also by interaction with peptide motifs of the enzyme that influence its dimerization, affinity for cofactors, and interaction with associated proteins. Structures, activities, and relative in vitro and in vivo specificities of various NOS inhibitors (amino acid and non-amino acid) with linear or cyclic structure and containing guanidine, amidine, or isothiuronium group are considered. These properties are mainly analyzed by comparison with effects of the inhibitors on the inducible NOS.

The reaction of direct phenylation by nucleogenic cations as a method of synthesis of unknown or complicated tritium labeled compounds

As a result of ion-molecular reactions of nucleogenic phenyl cations, generated by tritium β-decay in polytritiated benzene, with nucleophilic centers of investigated substrates the direct phenylation has been realized at first time and unknown tritium labeled aromatic derivatives of polyvalent fluorine together with the different N-phenyl substituted pyridinium compounds which are important syntones for biological and medical investigations have been synthesized.

Liquid scintillation spectrometry of tritium in the investigation of compound adsorption at a water/nonpolar liquid interface

We examine the application of the scintillation phase method as a radiochemical assay for studying the behavior of surfactants in liquid/liquid systems. The theoretical background of the technique is described. Results of our investigation of cationic and nonionic surfactants in a water/organic liquid system (arenes, alkanes, alcohols) are summarized.

Nitric oxide inhibitor activity of 2-amino-2-thiazoline derivatives

A series of 2-amino-2-thiazoline derivatives have been synthesized and characterized with respect to NOS-inhibitor activity in vivo. It was established that the dimensions of the substituents in 2-N-mono-and 2-N,N-disubstituted 2-amino-2-thiazolines are not significant for the biological activity of the products.

Kinetic Features of Labeled Product Formation under the Action of Atomic Tritium on Frozen Solutions and Lyophilically Dried Mixtures of Amino Acids

Formation of labeled amino acids in reactions of their lyophilically dried mixtures and frozen solutions with atomic tritium generated by thermal activation was studied in relation to the reaction time and pressure of molecular tritium. The molar radioactivity of the amino acids is a complex function of the reaction time. At short reaction times, the radioactivity of the amino acid depends primarily on its concentration in the near-surface layer. At long labeling times, in the case of surfactants, the yield of labeled products can decrease owing to side reactions. The influence of water on the rate of formation of labeled products and its role in thermalization of “hot” tritium atoms in the target is discussed. An increase in the tritium pressure in the system increases the initial radioactivity of the target but affects the yield of the labeled amino acids insignificantly. Recommendations are formulated on optimizing the conditions for labeling of biological macromolecules in their structural studies by tritium planigraphy.

Determination of Low Activity of Tritium-Labeled Amino Acids Using Simultaneously Flow Scintillation and Amino Acid Analyzers

The possibility of measuring a low activity of tritium-labeled amino acids in the eluate from Amino Acid Analyzer 835 (Hitachi, Japan) using a Radiomatic 150TR Flow Scintillation Analyzer (Packard Instrument Co., USA) was studied. Due to stepped variations of pH, ionic strength, and salt concentration in eluting solutions during amino acid separation and utilization of ninhydrin reagent in spectrophotometric measurements of amino acids, special selection of scintillation liquids was necessary. Six scintillation cocktails were tested: ZhS-8 (Reakhim, Ukraine), OptiPhase “HiSafe” 3 (Wallac Oy, EGGgr; Co., Finland), Hionic-Fluor, Ultima-Flo AP, Ultima-Flo M, and Ultima Gold (Packard Instrument Co., USA). It was found that Hionic-Fluor and Ultima-Flo AP cocktails are the most appropriate for flow measurements of tritium activity. Under optimal conditions the detection limit with Hionic-Fluor and Ultima-Flo AP was 150 and 100 decays min-1 in the peak of amino acid, respectively. Such a high sensitivity allows utilization of the above analytical system for measurements of amino acid radioactivity to study the structure of proteins and protein complexes by tritium planigraphy.

Permeability of Lipid Membranes for Atomic Tritium or Atom “Slipping” Effect and Its Role in Tritium Planigraphy

The depth of penetration of tritium atoms capable of isotope substitution, generated by thermal dissociation on a tungsten wire (thermal activation of tritium), into a solid target is considered. On the basis of calculations used in the theory of recoil atom stopping, with a lipid bilayer as example, the possibility of penetration of reactive atoms to a depth of up to 5 nm was demonstrated. This result is nicely consistent with the available experimental data. The possibility of “slipping” of atomic tritium, without loss of its reactivity, into cavities with a decreased electron density was suggested. This phenomenon should be taken into account when interpreting the results of studying biological macromolecules and their complexes by tritium planigraphy.

Cyclization of N-allylthiourea derivatives by the action ofα-chloronitrosoalkanes

A convenient method is proposed for obtaining difficultly available derivatives of 2-amino-5-chloromethyl-2-thiazoline by the cyclization of N-allythioureas under the action ofα-chloronitrosoalkanes. It is assumed that the reaction proceeds as a halogenophilic process leading to the intermediate formamidinesulfenyl chloride which is rapidly and selectively cyclized with the formation of 2-amino-2-thiazoline derivatives.

Solid-phase synthesis of deuterium- and tritium-labeled dopamine using carbon nanomaterials

Various procedures for preparing dopamine labeled with deuterium (2H) and tritium (3H) were considered. The labeled dopamine into which the hydrogen isotopes were introduced by solid-phase halogenation contained, on the average, 2.8 2H (3H) atoms. The labeled dopamine prepared by solid-phase isotope exchange using nanodiamonds as support contained, on the average, 4.8 2H (3H) atoms. The process was accompanied by the substrate deamination; as a result, the yield of the labeled analog was low (7–10%). Mass spectrometric analysis shows that the phenolic fragments formed by the dopamine deamination undergo dimerization.