Азотсодержащие вещества в снеге районов падения ступеней ракеты-носителя «Протон» в 2009–2019 гг.

The article presents analysis of the snow pollution caused by flights of the Proton launch vehicles launched from the Baikonur cosmodrome in 2009–2019. Data on 1477 snow samples collected in areas in Central Kazakhstan, south­east of Western Siberia, and north­east of the Altai are summarized to assess the pollution. In the uninhabited areas in Central Kazakhstan, where rocket fuel is spilled, pollution of snow was detected at 18 fall sites at a distance of up to 10 m from the fragments of the stages. The background value of pH is estimated as 6.6±0.9. The following nitrogen-­containing compounds (mg/l) were found in snow taken in the unpolluted territories of Central Kazakhstan: NO3­ (2.3±3.4), NH4+ (0.75±0.98) and to a lesser extent NO2– (0.015±0.019); asymmetric dimethylhydrazine and nitrosodimethylamine were not detected. The chemical composition of snow in the fall areas of the second stage of the Proton launch vehicle is in a good agreement with the background level of nitrogen­-containing substances of natural origin. There were no traces of the rocket fuel. Thus, in the snow on the Ketsko­Tym plain (south­east of Western Siberia) and north­east of Altai, the background content of nitrogen-­containing substances is equal, respectively (mg/l): NO3– (0.36±0.28 and 0.47±0.59); NH4+ (< 0.05 and 0.20±0.27); NO2– (0.048±0.016 and 0.027±0.073), which is determined by regional features and distance from sources of nitrogen­-containing substances. The data obtained allow us to conclude that the areas of the rocket falls on the above territories are not an environmental hazard to the environment by the concentration of nitrogen-­containing substances in the snow.Обобщены данные по 1477 пробам снега из районов падения ступеней ракеты-носителя «Протон» в Центральном Казахстане, на юго-востоке Западной Сибири и северо-востоке Алтая. В безлюдных территориях Центрального Казахстана, куда попадает ракетное топливо, достоверное загрязнение снега установлено на расстоянии не более 10 м от фрагментов падения первой ступени. Химический состав снега районов падения второй ступени (юго-восток Западной Сибири и северо-восток Алтая) отражает фоновые уровни азотсодержащих соединений природного происхождения и показывает отсутствие компонентов ракетного топлива. Очевидно, что районы падения и первой, и второй ступеней ракет-носителей «Протон», запускаемых с космодрома Байконур, не представляют собой зоны экологического бедствия

Two Crystal Structures Demonstrate Large Conformational Changes in the Eukaryotic Ribosomal Translocase

Two crystal structures of yeast translation elongation factor 2 (eEF2) were determined: the apo form at 2.9 Å resolution and eEF2 in the presence of the translocation inhibitor sordarin at 2.1 Å resolution. The overall conformation of apo eEF2 is similar to that of its prokaryotic homolog elongation factor G (EF-G) in complex with GDP. Upon sordarin binding, the three tRNA-mimicking C-terminal domains undergo substantial conformational changes, while the three N-terminal domains containing the nucleotide-binding site form an almost rigid unit. The conformation of eEF2 in complex with sordarin is entirely different from known conformations observed in crystal structures of EF-G or from cryo-EM studies of EF-G–70S complexes. The domain rearrangements induced by sordarin binding and the highly ordered drug-binding site observed in the eEF2–sordarin structure provide a high-resolution structural basis for the mechanism of sordarin inhibition. The two structures also emphasize the dynamic nature of the ribosomal translocase