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

Experimental procedure for the characterization of radiation damage in macromolecular crystals

A novel automatic procedure to determine the sensitivity of macromolecular crystals to radiation damage is presented. The information extracted from this procedure can be directly used for optimal planning of data collection or/and beamline calibration

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

The endoproteinase furin contains two essential Ca2+ions stabilizing its N-terminus and the unique S1 specificity pocket

The mammalian prohormone/proprotein convertase (PC) furin is responsible for the maturation of a great variety of homeostatic but also many pathogenic proteins within the secretory pathway and the endosomal pathway and at the cell surface. Similar to other members of the PC family, furin requires calcium for catalytic activity. In a previous paper, the structural association of the catalytic and the P-domain of furin was shown and data were presented indicating two or three calcium-binding sites. The exact number and the three-dimensional localization of the essential calcium sites within furin have now been determined by collecting X-ray diffraction data on either side of the Ca K absorption edge and by calculating a novel type of double difference map from these anomalous scattering data. Two calcium ions were unambiguously identified: the purely structural Ca-1 also conserved in the bacterial digestive subtilisins and the Ca-2 site specific to PCs and essential for the formation of the P1 specificity-determining S1-binding pocket. In addition, these anomalous diffraction data show that no tightly bound K+ sites exist in furin

The endoproteinase furin contains two essential Ca2+ions stabilizing its N-terminus and the unique S1 specificity pocket

The mammalian prohormone/proprotein convertase (PC) furin is responsible for the maturation of a great variety of homeostatic but also many pathogenic proteins within the secretory pathway and the endosomal pathway and at the cell surface. Similar to other members of the PC family, furin requires calcium for catalytic activity. In a previous paper, the structural association of the catalytic and the P-domain of furin was shown and data were presented indicating two or three calcium-binding sites. The exact number and the three-dimensional localization of the essential calcium sites within furin have now been determined by collecting X-ray diffraction data on either side of the Ca K absorption edge and by calculating a novel type of double difference map from these anomalous scattering data. Two calcium ions were unambiguously identified: the purely structural Ca-1 also conserved in the bacterial digestive subtilisins and the Ca-2 site specific to PCs and essential for the formation of the P1 specificity-determining S1-binding pocket. In addition, these anomalous diffraction data show that no tightly bound K+ sites exist in furin

Structural basis for the interaction of Escherichia coli NusA with protein N of phage λ

The C terminus of transcription factor NusA from Escherichia coli comprises two repeat units, which bind during antitermination to protein N from phage λ. To delineate the structural basis of the NusA–λN interaction, we attempted to crystallize the NusA C-terminal repeats in complex with a λN peptide (residues 34–47). The two NusA domains became proteolytically separated during crystallization, and crystals contained two copies of the first repeat unit in contact with a single λN fragment. The NusA modules employ identical regions to contact the peptide but approach the ligand from opposite sides. In contrast to the α-helical conformation of the λN N terminus in complex with boxB RNA, residues 34–40 of λN remain extended upon interaction with NusA. Mutational analyses indicated that only one of the observed NusA–λN interaction modes is biologically significant, supporting an equimolar ratio of NusA and λN in antitermination complexes. Solution studies indicated that additional interactions are fostered by the second NusA repeat unit, consistent with known compensatory mutations in NusA and λN. Contrary to the RNA polymerase α subunit, λN binding does not stimulate RNA interaction of NusA. The results demonstrate that λN serves as a scaffold to closely oppose NusA and the mRNA in antitermination complexes