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Soluble C (soluble + c)

Distribution by Scientific Domains

Chemistry	50%

Selected Abstracts

Increases in pH and soluble salts influence the effect that additions of organic residues have on concentrations of exchangeable and soil solution aluminium

EUROPEAN JOURNAL OF SOIL SCIENCE, Issue 3 2002
M. S. Mokolobate
Summary It has been suggested that additions of organic residues to acid soils can ameliorate Al toxicity. For this reason the effects of additions of four organic residues to an acid soil on pH and exchangeable and soil solution Al were investigated. The residues were grass, household compost, filter cake (a waste product from sugar mills) and poultry manure, and they were added at rates equivalent to 10 and 20 t ha,1. Additions of residues increased soil pH measured in KCl (pH(KCl)) and decreased exchangeable Al3+ in the order poultry manure > filter cake > household compost > grass. The mechanism responsible for the increase in pH differed for the different residues. Poultry manure treatment resulted in lower soil pH measured in water (pH(water)) and larger concentrations of total (AlT) and monomeric (Almono) Al in soil solution than did filter cake. This was attributed to a soluble salt effect, originating from the large cation content of poultry manure, displacing exchangeable Al3+ and H+ back into soil solution. The considerably larger concentrations of soluble C in soil solution originating from the poultry manure may also have maintained greater concentrations of Al in soluble complexed form. There was a significant negative correlation (r = ,0.94) between pH(KCl) and exchangeable Al. Concentrations of AlT and Almono in soil solution were not closely related with pH or exchangeable Al. The results suggest that although additions of organic residues can increase soil pH and decrease Al solubility, increases in soluble salt and soluble C concentrations in soil solution can substantially modify these effects. [source]

Phosphorus nutrition-mediated effects of arbuscular mycorrhiza on leaf morphology and carbon allocation in perennial ryegrass

NEW PHYTOLOGIST, Issue 2 2005
Agustín A. Grimoldi
Summary ,,The aim of this work was to disentangle phosphorus status-dependent and -independent effects of arbuscular mycorrhizal fungus (AMF) on leaf morphology and carbon allocation in perennial ryegrass (Lolium perenne). ,,To this end, we assessed the P-response function of morphological components in mycorrhizal and nonmycorrhizal plants of similar size. ,,AMF (Glomus hoi) stimulated relative P-uptake rate, decreased leaf mass per area (LMA), and increased shoot mass ratio at low P supply. Lower LMA was caused by both decreased tissue density and thickness. Variation in tissue density was almost entirely caused by variations in soluble C, while that in thickness involved structural changes. ,,All effects of AMF were indistinguishable from those mediated by increases in relative P-uptake rate through higher P-supply rates. Thus the relationships between relative P-uptake rate, leaf morphology and C allocation were identical in mycorrhizal and nonmycorrhizal plants. No evidence was found for AMF effects not mediated by changes in plant P status. [source]

Functional characterization of the evolutionarily divergent fern plastocyanin

FEBS JOURNAL, Issue 16 2004
José A. Navarro
Plastocyanin (Pc) is a soluble copper protein that transfers electrons from cytochrome b6f to photosystem I (PSI), two protein complexes that are localized in the thylakoid membranes in chloroplasts. The surface electrostatic potential distribution of Pc plays a key role in complex formation with the membrane-bound partners. It is practically identical for Pcs from plants and green algae, but is quite different for Pc from ferns. Here we report on a laser flash kinetic analysis of PSI reduction by Pc from various eukaryotic and prokaryotic organisms. The reaction of fern Pc with fern PSI fits a two-step kinetic model, consisting of complex formation and electron transfer, whereas other plant systems exhibit a mechanism that requires an additional intracomplex rearrangement step. The fern Pc interacts inefficiently with spinach PSI, showing no detectable complex formation. This can be explained by assuming that the unusual surface charge distribution of fern Pc impairs the interaction. Fern PSI behaves in a similar way as spinach PSI in reaction with other Pcs. The reactivity of fern Pc towards several soluble c -type cytochromes, including cytochrome f, has been analysed by flavin-photosensitized laser flash photolysis, demonstrating that the specific surface motifs for the interaction with cytochrome f are conserved in fern Pc. [source]

Structure at 1.5,Å resolution of cytochrome c552 with its flexible linker segment, a membrane-anchored protein from Paracoccus denitrificans

ACTA CRYSTALLOGRAPHICA SECTION D, Issue 7 2010
Chitra Rajendran
Electron transfer (ET) between the large membrane-integral redox complexes in the terminal part of the respiratory chain is mediated either by a soluble c -type cytochrome, as in mitochondria, or by a membrane-anchored cytochrome c, as described for the ET chain of the bacterium Paracoccus denitrificans. Here, the structure of cytochrome c552 from P. denitrificans with the linker segment that attaches the globular domain to the membrane anchor is presented. Cytochrome c552 including the linker segment was crystallized and its structure was determined by molecular replacement. The structural features provide functionally important information. The prediction of the flexibility of the linker region [Berry & Trumpower (1985), J. Biol. Chem.260, 2458,2467] was confirmed by our crystal structure. The N-terminal region from residues 13 to 31 is characterized by poor electron density, which is compatible with high mobility of this region. This result indicates that this region is highly flexible, which is functionally important for this protein to shuttle electrons between complexes III and IV in the respiratory chain. Zinc present in the crystallization buffer played a key role in the successful crystallization of this protein. It provided rigidity to the long negatively charged flexible loop by coordinating negatively charged residues from two different molecules and by enhancing the crystal contacts. [source]