39 research outputs found
Method of analysis of the spatial galaxy distribution at gigaparsec scales. I. Initial principles
Initial principles of a method of analysis of the luminous matter spatial
distribution with sizes about thousands Mpc are presented. The method is based
on an analysis of the photometric redshift distribution N(z) in the deep fields
with large redshift bins \Deltaz=0.1{\div}0.3. Number density fluctuations in
the bins are conditioned by the Poisson's noise, the correlated structures and
the systematic errors of the photo-z determination. The method includes
covering of a sufficiently large region on the sky by a net of the deep
multiband surveys with the sell size about 10^{\circ}x10^{\circ} where
individual deep fields have angular size about 10'x10' and may be observed at
telescopes having diameters 3-10 meters. The distributions of photo-z within
each deep field will give information about the radial extension of the super
large structures while a comparison of the individual radial distributions of
the net of the deep fields will give information on the tangential extension of
the super large structures. A necessary element of the method is an analysis of
possible distortion effects related to the methodic of the photo-z
determination.Comment: 12 page
Synthesis of 5-Hydroxyectoine from Ectoine: Crystal Structure of the Non-Heme Iron(II) and 2-Oxoglutarate-Dependent Dioxygenase EctD
As a response to high osmolality, many microorganisms synthesize various types of compatible solutes. These organic osmolytes aid in offsetting the detrimental effects of low water activity on cell physiology. One of these compatible solutes is ectoine. A sub-group of the ectoine producer's enzymatically convert this tetrahydropyrimidine into a hydroxylated derivative, 5-hydroxyectoine. This compound also functions as an effective osmostress protectant and compatible solute but it possesses properties that differ in several aspects from those of ectoine. The enzyme responsible for ectoine hydroxylation (EctD) is a member of the non-heme iron(II)-containing and 2-oxoglutarate-dependent dioxygenases (EC 1.14.11). These enzymes couple the decarboxylation of 2-oxoglutarate with the formation of a high-energy ferryl-oxo intermediate to catalyze the oxidation of the bound organic substrate. We report here the crystal structure of the ectoine hydroxylase EctD from the moderate halophile Virgibacillus salexigens in complex with Fe3+ at a resolution of 1.85 Å. Like other non-heme iron(II) and 2-oxoglutarate dependent dioxygenases, the core of the EctD structure consists of a double-stranded β-helix forming the main portion of the active-site of the enzyme. The positioning of the iron ligand in the active-site of EctD is mediated by an evolutionarily conserved 2-His-1-carboxylate iron-binding motif. The side chains of the three residues forming this iron-binding site protrude into a deep cavity in the EctD structure that also harbours the 2-oxoglutarate co-substrate-binding site. Database searches revealed a widespread occurrence of EctD-type proteins in members of the Bacteria but only in a single representative of the Archaea, the marine crenarchaeon Nitrosopumilus maritimus. The EctD crystal structure reported here can serve as a template to guide further biochemical and structural studies of this biotechnologically interesting enzyme family