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.     

Using the achievements in tribology for teaching technical disciplines

Tribology (from the Greek tribo (friction) and logos (word, doctrine)) joins the problems of friction, wear, and lubrication as a scientific discipline, and studies the process of interaction between surfaces during their relative motion. The term appeared in 1966 in England (the author was P. Jost).     

Integrating Statistical and Machine-Learning Approach for Meta-Analysis of Bisphenol A-Exposure Datasets Reveals Effects on Mouse Gene Expression within Pathways of Apoptosis and Cell Survival

Bisphenols are important environmental pollutants that are extensively studied due to different detrimental effects, while the molecular mechanisms behind these effects are less well understood. Like other environmental pollutants, bisphenols are being tested in various experimental models, creating large expression datasets found in open access storage. The meta-analysis of such datasets is, however, very complicated for various reasons. Here, we developed an integrating statistical and machine-learning model approach for the meta-analysis of bisphenol A (BPA) exposure datasets from different mouse tissues. We constructed three joint datasets following three different strategies for dataset integration: in particular, using all common genes from the datasets, uncorrelated, and not co-expressed genes, respectively. By applying machine learning methods to these datasets, we identified genes whose expression was significantly affected in all of the BPA microanalysis data tested; those involved in the regulation of cell survival include: Tnfr2, Hgf-Met, Agtr1a, Bdkrb2; signaling through Mapk8 (Jnk1)); DNA repair (Hgf-Met, Mgmt); apoptosis (Tmbim6, Bcl2, Apaf1); and cellular junctions (F11r, Cldnd1, Ctnd1 and Yes1). Our results highlight the benefit of combining existing datasets for the integrated analysis of a specific topic when individual datasets are limited in size.     

Comparative Study of Reaction of Atomic Tritium with Glucosamine and Amino Acids

Reaction of amino acids (glycine and serine) and amino sugar (glucosamine) with atomic tritium generated by thermal dissociation of molecular tritium on a tungsten filament was studied. A frozen aqueous solutions and a freeze-dried mixture of these compounds was bombarded with tritium atoms is a special vacuum unit. The relative yield of the labeled compounds was determined as influenced by the reaction conditions (residual pressure in the system and bombardment time) and target type (frozen solution and freeze-dried mixture). Formation of labeled products is almost independent of the tritium pressure. The ratio of the formation rates of labeled serine and glycine in the frozen solution and freeze-dried mixture bombarded with atomic tritium for 45–270 s was 1.66±0.15 and 1.44±0.13, respectively. At shorter reaction time (15 s), the ratio increases to 3.5±0.2 and 2.0±0.4, respectively. The formation rate of [³H]glucosamine in the mixture is higher at a shorter bombardment time. The radioactivity ratio of labeled glucosamine and glycine formed in frozen solutions and freeze-dried mixture in 15 s was 26.0±2.3 and 6.8±0.6, respectively. At longer reaction time, the relative yield of [³H]glucosamine sharply decreases owing to stronger radiolysis of labeled glucosamine on exposure to tritium beam.__________Translated from Radiokhimiya, Vol. 47, No. 3, 2005, pp. 281–283.Original Russian Text Copyright © 2005 by Badun, Ksenofontov, Lukashina, Pozdnyakova, Fedoseev.     

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.