Проблемы технической оснащённости России для работы в условиях Арктики

Cytochrome c oxidase is a respiratory enzyme catalysing the energy-conserving reduction of molecular oxygen to water. The crystal structure of the ba(3)-cytochrome c oxidase from Thermus thermophilus has been determined to 2.4 Å resolution using multiple anomalous dispersion (MAD) phasing and led to the discovery of a novel subunit IIa. A structure-based sequence alignment of this phylogenetically very distant oxidase with the other structurally known cytochrome oxidases leads to the identification of sequence motifs and residues that seem to be indispensable for the function of the haem copper oxidases, e.g. a new electron transfer pathway leading directly from Cu(A) to Cu(B). Specific features of the ba(3)-oxidase include an extended oxygen input channel, which leads directly to the active site, the presence of only one oxygen atom (O(2–), OH(–) or H(2)O) as bridging ligand at the active site and the mainly hydrophobic character of the interactions that stabilize the electron transfer complex between this oxidase and its substrate cytochrome c. New aspects of the proton pumping mechanism could be identified

Предельные метрологические характеристики генераторов сигналов на основе прямого цифрового синтеза

Выпускная квалификационная работа 75 страниц, 24 рисунка, 26 таблиц, 16 источников, 4 приложения. Ключевые слова: генератор сигналов, метрологические характеристики, амплитуда, период, коэффициент гармоник. Объектами исследования являются характеристики гармонических колебаний: амплитуда, период и коэффициент гармоник. Цель работы – исследование метрологических характеристик генераторов сигналов на основе прямого цифрового синтеза. В ходе работы проводилось определение нестабильности амплитуды, нестабильности периода и коэффициента гармоник путем моделирования с помощью программного обеспечения для инженерных вычислений – Mathcad. В результате работы были получены зависимости, позволяющие оценить необходимый период дискретизации по заданной нестабильности амплитуды, нестабильности периодаFinal qualifying work is 75 pages, 24 figures, 26 tables, 16 sources, 4 of the annex. Keywords: signal generator, the metrological characteristics, amplitude, period, total harmonic distortion. The objects of study are the characteristics of harmonic vibrations: amplitude, period, and total harmonic distortion. The purpose is research of metrological characteristics signal generator based on direct digital synthesis. The work was carried out determining the amplitude of instability, instability period and harmonic distortion by simulation software for engineering calculations - Mathcad. As a result of the work were obtained according to assess the required sampling period for a given amplitude instability, instability period and harmonic distortion

Extraction of single bunches of synchrotron radiation from storage rings with an X-ray chopper based on a rotating mirror

An ultrafast shutter has been developed for alteration of the time structure of synchrotron radiation from storage rings in the hard X-ray regime. In test applications on the wiggler beamline BW6 at DORIS, single bunches were extracted from the incident pulsed synchrotron radiation with minimum bunch-to-bunch distances of 482 ns. Even substantially shorter time windows may be defined in the case of tight collimation in the incident beam, e.g. on low-emittance sources. The shutter system is based on a new chopper concept involving a rotating X-ray mirror which totally reflects the incident radiation onto the sample through a remote slit. Rather low rotational velocities are sufficient to reach extremely short full open times. An additional shutter consisting of a slowly rotating disk prevents frame overlap and controls the repetition rate. A coincidence timing circuit checks the synchronization with the synchrotron bunch clock and provides trigger signals, e.g. for external excitation of a sample. The chopper system may be used, for example, in nanosecond time-resolved Laue diffraction experiments

Beamline diagnostics for protein crystallography using synchrotron radiation

Beam diagnostics devices are described for the monitoring of all basic parameters relevant to protein data collection using synchrotron radiation. The parameters include the total power in the white beam, the positions and directions of the incident white and monochromatic beams, and the intensity, wavelength, and polarization in the incident monochromatic beam. Such devices have been installed on a doubly focusing wiggler beamline, BW6, at DORIS. They assure high quality in protein data collection despite fluctuations in the beam, facilitate rapid alignment of the entire beamline, and provide a basis for automatic realignment of the diffraction setup and the x‐ray optics

Flexibility, conformational diversity and two dimerization modes in complexes of ribosomal protein L12

Protein L12, the only multicopy component of the ribosome, is presumed to be involved in the binding of translation factors, stimulating factor-dependent GTP hydrolysis. Crystal structures of L12 from Thermotoga maritima have been solved in two space groups by the multiple anomalous dispersion method and refined at 2.4 and 2.0 Å resolution. In both crystal forms, an asymmetric unit comprises two full-length L12 molecules and two N–terminal L12 fragments that are associated in a specific, hetero-tetrameric complex with one non-crystallographic 2–fold axis. The two full-length proteins form a tight, symmetric, parallel dimer, mainly through their N–terminal domains. Each monomer of this central dimer additionally associates in a different way with an N–terminal L12 fragment. Both dimerization modes are unlike models proposed previously and suggest that similar complexes may occur in vivo and in situ. The structures also display different L12 monomer conformations, in accord with the suggested dynamic role of the protein in the ribosomal translocation process. The structures have been submitted to the Protein Databank (http://www.rcsb.org/pdb) under accession numbers 1DD3 and 1DD4