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Sulphate uptake and metabolism in the chrysomonad, Monochrysis lutheri (1975)

Deane, Elizabeth M. ; O'Brien, R. W.

Springer

Archives of microbiology 105 (1975), S. 295-301

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ISSN: 1432-072X

Keywords: Sulphate ; Transport ; Metabolism ; Chrysophyceae ; Phytoplankton ; Monochrysis lutheri

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract The intracellular concentration of inorganic 35SO4 in Monochrysis lutheri cells exposed to 0.513 mM Na2 35SO4 for up to 6-hr remained constant at about 0.038 mM. The exchange rate of this 35SO4 with the external unlabelled sulphate was negligible compared to the rate of influx across the plasmalemma (0.032 μmoles/g cells/hr). The flux of free 35SO4 to organic 35S was 0.029 μmoles/g cells/hr. Assuming an internal electrical potential in the cells of-70 mV, this intracellular concentration of inorganic 35SO4 was well in excess of that obtainable by passive diffusion as calculated from the Nernst equation. These results indicate that sulphate is accumulated by an active mechanism rather than by facilitated diffusion. Sulphate uptake appears to occur via a carrier-mediated membrane transport system which conforms to Michaelis-Menten type saturation kinetics with a K m of 3.2×10-5 M and a V max of 7.9×10-5 μmoles sulphate/hr/105 cells. Uptake was dependent on a source of energy since the metabolic inhibitor CCCP almost completely inhibited uptake under both light and dark conditions and DCMU caused a 50% decrease in uptake under light conditions. Under dark conditions, uptake remained at about 80% of that observed under light conditions and was little affected by DCMU, indicating that the energy for uptake could be supplied by either photosynthesis or respiration. A charge and size recognition site in the cell is implied by the finding that sulphate uptake was inhibited by chromate and selenate but not by tungstate, molybdate, nitrate or phosphate. Chromate did not inhibit photosynthesis. Cysteine and methionine added to the culture medium were apparently capable of exerting inhibition of sulphate uptake in both unstarved and sulphate-starved cells. Cycloheximide slightly inhibited sulphate uptake over an 8-hr period indicating, either a slow rate of entry of the inhibitor into the cells or a slow turnover of the proteins(s) associated with sulphate transport.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00447149

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Phosphorus-31 NMR studies of polymer-supported highly reactive copper reagents (1992)

O'Brien, R. A. ; Gupta, A. K. ; Rieke, R. D. ; [et al.]

Chichester : Wiley-Blackwell

Organic Magnetic Resonance 30 (1992), S. 398-402

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ISSN: 0749-1581

Keywords: P-31 Phosphorus ; Solid-state NMR T1 ; Relaxation ; Active copper ; Copper phosphine ; Chemistry ; Analytical Chemistry and Spectroscopy

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: The chemistry of highly reactive zerovalent copper species represents an active area of research. Recently, active metal chemistry has been successfully accomplished using polymer-supported triphenylphosphine-copper(I) coordination complexes as precursors. Since the materials are solids, detailed examination of the reagents at vaious stages of chemical reaction can be problematic, since the primary means of examination has historically been proton, 13C and 31P NMR methods. In this study, cross-polarization magic angle spinning (CPMAS) experiments, combined with 31P T1 relaxation measurements (via proton cross-polarization), provided data which allowed the determination of the role of the phosphine species in the overall chemistry of these materials. Although it is known that the type of phosphine affects the chemistry, it was found here that there is no observable interaction between the reduced copper species and the polymer-supported triphenylphosphine.

Additional Material: 4 Ill.