Chemical synthesis of tritium-labeled prostaglandins A, B and F

Formation of prostaglandins A, B and F from prostaglandin E has been studied. Synthesis of tritium-labelled prostaglandins A1, A2, B1, B2, F1 alpha, F2 alpha, F1 beta, F2 beta of high molar radioactivity from highly labelled PGE1 and PGE2 is described.     

The surface activity of vasopressin and its interaction with artificial and biological membranes]

It was determined that vasopressin has surface active properties and in nanomolic concentrations is capable to incorporate in lipoprotein monolayers which are formed from myocytes plasma membranes. By means of pH-metric and fluorescent analysis it was shown that vasopressin interacts with other membrane structures which have no specific receptors--phosphatidylcholinic liposomes and vesicles of sarcoplasmic reticulum of skeletal muscles causing increasing permeability of phospholipid bilayer for Ca2+ ions.     

Comparative analysis of the DXPas34 regulatory region in rodents

Mouse X chromosome inactivation center contains the DXPas34 minisatellite locus which plays an important role in expression regulation of the Tsix and Xist genes, involved into female dosage compensation. Comparative analysis of the DXPas34 locus from mouse, rat, and four common vole species revealed similar organization of this region in the form of tandem repeat blocks. A search for functionally important elements in this locus showed that all the species examined carried the conservative motif monomers, which could be involved in regulation of X inactivation.     

Studies of the aminopeptidase proteolysis of semax analogues with different <Emphasis Type="Italic">N</Emphasis>-terminal amino acid residues

Proteolysis of semax (Met-Glu-His-Phe-Pro-Gly-Pro, Sem) and its analogues with the substitution of Ala, Gly, Thr, or Trp for the N-terminal Met was studied. This substitution was shown to change the degradation rate of these peptides by leucine aminopeptidase (EC 3.4.11.2, Sigma, Type VI, 9.2 activity units/mg). [Ala¹]Sem, [Gly¹]Sem, and [Thr¹]Sem (the semax analogues) proved to be more stable to the proteolysis than semax itself. It was demonstrated that the primary product of the proteolysis was His-Phe-Pro-Gly-Pro (Sem-5). In the case of [Trp¹]Sem, the comparable amount of Glu-His-Phe-Pro-Gly-Pro (Sem-6) was found to be formed along with Sem-5. In was established that all the studied semax analogues could be used as inhibitors of its proteolysis.     

Phytoplankton of the Amur River Estuary (Sea of Okhotsk) during the summer periods of 2005–2007

The qualitative composition of planktonic microalgae in the Amur River Estuary (in the Sea of Okhotsk) was studied in July 2005, June 2006, and June 2007. The biomass and abundance of phytoplankton were studied for the first time. The average cell density of the microalgae ranged from 194700 to 855100 cells/liter, being higher in 2006 than in 2005 and 2007. The average biomass of the community varied from 1.06 g/m³ in 2007 to 3.17 g/m³ in 2006. Analysis of the similarity of the species composition and cell density of the phytoplankton revealed two groups of stations: the first includes stations in the northern and central parts of the Amur Estuary; and the second includes stations in the southern and central parts. The first group was characterized by the predominance of freshwater diatoms and a high abundances of green and blue-green algae and the second group was characterized by the predominance of marine microalgae. The high cell density and biomass of phytoplankton were due to the increased nutrient input via the river runoff of the Amur.     

Synthesis, crystal structure and magnetic properties of a 1D mixed-metal-mixed-ligand Ni(II)/Fe(II) coordination polymer built on the nitroprusside anion

A new complex [Ni(L)Fe(CN)₅NO] · 2H₂O (L = 4,6,6-trimethyl-1,9-diamino-3,7-di-aza-nona-3-ene) has been obtained and characterized by means of X-ray crystallographic analysis and magnetochemistry. The Fe(CN)₅NO²⁻ anion links to the Ni(L)²⁺ cation through two bridging cyanide groups in a bent fashion. The intrachain Ni?Ni and interchain Ni?Ni distances are equal to 9.81(8) and 7.75(1) Å, respectively. The magnetic behaviour of the complex indicates the zero field splitting parameter D higher than 3 cm⁻¹ and the average exchange parameter (intra- and interchain) corresponding to direct Ni-Ni magnetic interaction in the crystal lattice equals ∼−0.2 cm⁻¹.     

The State of Photosystem I Complexes in the Central Regions of Pea Granal Thylakoids

Grana-core and grana-margin fragments were obtained from pea (Pisum sativum L.) thylakoids, and both fractions contained photosystem I (PSI) complexes. The yield of these fractions exhibited variations for the plants grown during various periods of the summer season. Low-temperature fluorescence spectra, excitation spectra of long-wave fluorescence, and P700 kinetic characteristics were recorded for these fractions. PSI complexes in central granal regions were associated with PSII and the light-harvesting complexes of PSII, which followed from the excitation spectra of long-wave fluorescence and the kinetic characteristics of P700 light oxidation and dark reduction. The characteristics of the margin regions were changed depending on the fraction yield. If the yield was low, marginal fragments contained mainly PSI complexes. When the yield increased, PSI associates with PSII appeared. A spatial distribution and state of PSI complexes in granal thylakoids are discussed as related to the size and composition of the light-harvesting antenna.     

Features of Grana Organization in Pea Chloroplasts

Two fractions of membrane fragments—the pellets precipitated at 1300 and 20000 g (fractions G1.3 and G20, respectively)—were isolated from pea (Pisum sativum L.) chloroplasts after solubilization with digitonin. These fragments assigned to grana displayed the following differences: (1) in spectra of low-temperature fluorescence, the ratio of short-wave and long-wave band intensities, as well as integrated intensity of the whole spectrum, were higher for G1.3 than for G20 fraction; (2) in excitation spectra of long-wave fluorescence, the ratio of peaks at 650 and 680 nm and integrated intensity of the spectrum were higher for G1.3 than for G20 fraction; and (3) the shapes of fluorescence excitation spectra differed for G1.3 and G20. These results indicate that the two fractions examined differed in proportion of photosystem I and photosystem II complexes, as well as in organization of these complexes. The size of light-harvesting antenna was larger in PSI complexes of G1.3 fraction, owing, in particular, to a higher content of chlorophyll a/b-protein complexes in this fraction. After repeated digitonin fragmentation of G1.3 and G20 preparations, more than 80% of G1.3 fraction was decomposed into lighter fragments, whereas G20 fraction was resistant to fragmentation (it lost about 10% of its material). Analysis of the data suggests the presence of two structurally different types of thylakoids in grana. The yield of G20 fraction (about 20%) is comparable to the ratio between the number of intergranal thylakoids, connected to granum in pea chloroplasts, and the total number of thylakoids in this granum. Based on these data, we assume that G20 fraction represent the fragments of intergranal thylakoids that extend into the granum.__________Translated from Fiziologiya Rastenii, Vol. 52, No. 4, 2005, pp. 499–506.Original Russian Text Copyright © 2005 by Kochubei, Shevchenko, Bondarenko.