On the phenotype distribution of red cell acid phosphatase in Czechoslovakia

Summary A random group of 300 donors living in the district of eské Budjovice (southern Bohemia) have been investigated for the incidence of the individual phenotypes of red cell acid phosphatase. The calculated frequencies of the genes P^a, P^b and P^c are 0.322, 0.615 and 0.063, respectively.     

Chromosome numbers in some pear cultivars

V sortimentu hru?ni d?le?itěj?ích pro pěstování v ?eskoslovensku nebyl dosud znám po?et chromosom? u 11 sort. Bylo proto provedeno toto zji?tění a shledáno, ?e v?echny tyto sorty jsou diploidní, 2n=34. Jsou to: Ananaska ?eská, Anglická bergamotka, Bezjaderka ?íhova, ?istecká banánová, Fulvie, Jeanne d'Arc, Kolmarská zlatá, Monchallardova, Notá? Lepin, Sterkmansova máslovka a Zefyrinka. Provedeno té? ově?ení star?ích údaj? o diploidním stavu sort Kongresovka a Olivier de Serres, nápadných poměrně nízkou klíěivostí pylu. Jejich diploidní po?et chromosom? byl potyrzen.     

Mesophile und subxerophile Waldgesellschaften Mittelböhmens

In der vorliegenden Arbeit wurden mesophile und subxerophile Waldgesellschaften des Mittelböhmischen Hügellandes und der Elbeebene studiert. Es wurden hier folgende Syntaxa festgestellt und analysiert: dasGalio-Carpinetum Oberd. 1957 mit drei Subassoziationen (typicum, primuletosum veris, luzuletosum albidae), dasGalio rotundifolii-Quercetum ass. nova prov., dasTilio-Quercetum sensuPassarge 1962 mit zwei Ausbildungsformen (typische, Ausb. vonPotentilla alba) und dasPotentillo albae-Quercetum Libbert 1933 mit zwei Ausbildungsformen (typische, Ausb. vonFestuca heterophylla). Diese Gesellschaften wurden vom phytozönotischen und ökologischen Standpunkt aus analysiert; bei jeder Gesellschaft wird auch ihre Verbreitung und wirtschaftliche Wertung behandelt. Die floristische Ähnlichkeit und Homogenität einzelner Syntaxa wurde mathematisch überprüft.     

Effects of hydrogen sulfide on the heme coordination structure and catalytic activity of the globin-coupled oxygen sensor <Emphasis Type="Italic">Af</Emphasis>GcHK

AfGcHK is a globin-coupled histidine kinase that is one component of a two-component signal transduction system. The catalytic activity of this heme-based oxygen sensor is due to its C-terminal kinase domain and is strongly stimulated by the binding of O₂ or CO to the heme Fe(II) complex in the N-terminal oxygen sensing domain. Hydrogen sulfide (H₂S) is an important gaseous signaling molecule and can serve as a heme axial ligand, but its interactions with heme-based oxygen sensors have not been studied as extensively as those of O₂, CO, and NO. To address this knowledge gap, we investigated the effects of H₂S binding on the heme coordination structure and catalytic activity of wild-type AfGcHK and mutants in which residues at the putative O₂-binding site (Tyr45) or the heme distal side (Leu68) were substituted. Adding Na₂S to the initial OH-bound 6-coordinate Fe(III) low-spin complexes transformed them into SH-bound 6-coordinate Fe(III) low-spin complexes. The Leu68 mutants also formed a small proportion of verdoheme under these conditions. Conversely, when the heme-based oxygen sensor EcDOS was treated with Na₂S, the initially formed Fe(III)–SH heme complex was quickly converted into Fe(II) and Fe(II)–O₂ complexes. Interestingly, the autophosphorylation activity of the heme Fe(III)–SH complex was not significantly different from the maximal enzyme activity of AfGcHK (containing the heme Fe(III)–OH complex), whereas in the case of EcDOS the changes in coordination caused by Na₂S treatment led to remarkable increases in catalytic activity.     

Surface hydrolysis of polyacrylonitrile with nitrile hydrolysing enzymes from Micrococcus luteus BST20

A new Micrococcus luteus strain BST20 was isolated with ability to metabolize PAN polymers as sole carbon source. Out of seven synthetized PAN copolymers containing different moieties of acrylic acid and/or vinyl acetate the polymer with lowest crystallinity (PAN with 5% vinyl acetate) was most easily metabolized. (13)C labelled PAN was completely converted to the acrylic acid by this strain. M. luteus BST20 produced membrane-bound nitrile hydrolysing enzymes able to convert nitrile groups on PAN powder surface to the corresponding acids. Similarly, nitrile groups on PAN fabrics were transformed to the corresponding acid as indicated by an K/S increased after dying with Methylene blue and the released ammonia. On small soluble substrates the enzyme system showed a preference for aliphatic and aromatic substituted aliphatic nitriles.     

Weak self-association in a carbohydrate system

The physiological importance of weak interactions between biological macromolecules (molar dissociation constants >10 microM) is now well recognized, particularly with regard to cell adhesion and immunological phenomena, and many weak interactions have been measured for proteins. The concomitant importance of carbohydrate-carbohydrate interactions has also been identified, although no weak interaction between pure carbohydrate systems has ever been measured. We now demonstrate for the first time to our knowledge using a powerful probe for weak interactions--sedimentation velocity in the analytical ultracentrifuge--that at least some carbohydrates (from the class of polysaccharides known as heteroxylans and demonstrated here to be biologically active) can show well-defined weak self-interactions of the "monomer-dimer" type frequently found in protein systems. The weak interaction between the heteroxylans is shown from a temperature dependence study to be likely to be hydrophobic in nature.     

Diversity of forest vegetation across a strong gradient of climatic continentality: Western Sayan Mountains, southern Siberia

Southern Siberian mountain ranges encompass strong climatic contrasts from the relatively oceanic northern foothills to strongly continental intermountain basins in the south. Landscape-scale climatic differences create vegetation patterns, which are analogous to the broad-scale vegetation zonation over large areas of northern Eurasia. In their southern, continental areas, these mountains harbour forest types which potentially resemble the full-glacial forests recently reconstructed for Central Europe. To identify forest vegetation–environment relationships in the southern Siberian mountain ranges, forest vegetation of the Western Sayan Mountains was sampled on a 280 km transect running from the northern foothills with oceanic climatic features to the continental Central Tuvinian Basin in the south. Based on the species composition, vegetation was classified into hemiboreal forests, occurring at drier and summer-warm sites with high-pH soil, and taiga, occurring at wetter, summer-cool sites with acidic soil. Hemiboreal forests included Betula pendula-Pinus sylvestris mesic forest, Larix sibirica dry forest and Pinus sylvestris dry forest. Taiga included Abies sibirica-Betula pendula wet forest, Abies sibirica-Pinus sibirica mesic forest and Pinus sibirica-Picea obovata continental forest. Hemiboreal forests were richer in vascular plant species, while taiga was richer in ground-dwelling cryptogams. Vegetation–environment relationships were analysed by indirect and direct ordination. Winter and summer temperatures and precipitation exerted a dominant influence on species composition. Soil pH was also an important correlate of species composition, but this factor itself was probably controlled by precipitation. At a more local scale, the main source of variation in species composition was topography, producing landscape patterns of contrasting plant communities on slopes of different aspects and valley bottoms. The response of tree species to major environmental factors was expressed with Huisman–Olff–Fresco models. Larix sibirica appeared to be most resistant to drought and winter frosts, Pinus sibirica was adapted to low temperatures both in winter and summer, and Picea obovata had an intermediate response to climate. Betula pendula, Pinus sylvestris and Populus tremula were associated with the warmest sites with intermediate precipitation, while Abies sibirica was the most moisture-demanding species, sensitive to deep winter frosts.