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1991 (1)
1982 (1)
1Author    Christoph GierschRequires cookie*
 Title    Photophosphorylation by Chloroplasts: Effects o f Low Concentrations o f Ammonia and Methylamine  
 Abstract    Intact chloroplasts exposed to hypotonic assay conditions are capable o f photophosphorylating exogenous ADP. The rate o f phosphorylation by these unbroken plastids is increased by 10—50% upon the addition o f low concentrations (< mM) o f N H 3 or C H 3 N H 2. Stimulation o f phosphory­ lation is abolished by washing chloroplasts with MgCl2. Evidence is presented that washing re­ moves a factor responsible for amine-induced increase o f A T P production and that this factor is associated with the thylakoid membrane. Addition o f CH3 N H 2 increased the proton permeability of the thylakoid membrane o f unbroken and washed chloroplasts during the light/dark transition. Hence, differences o f the membrane permeability for protons between the two preparations seem not to be responsible for an increase o f A T P production upon the addition o f amines. Stimulation of photophosphorylation by methylamine is observed even at light itensities which do not saturate the proton motive force, which in turn is reduced upon the addition o f the uncoupler. Apparently, phosphorylation can be stimulated, although the limiting driving force is diminished. It is con­ cluded that phosphorylation by unbroken chloroplasts under low light illumination is limited kinetically, not energetically. Consequences o f these findings for observation made with intact chloroplasts are discussed. 
  Reference    Z. Naturforsch. 37c, 242—250 (1982); received December 23 1981 
  Published    1982 
  Keywords    Photophosphorylation, Uncoupling, Amines, Proton Motive Force, Chloroplasts, Chemiosmotic Theory 
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 TEI-XML for    default:Reihe_C/37/ZNC-1982-37c-0242.pdf 
 Identifier    ZNC-1982-37c-0242 
 Volume    37 
2Author    GabrieleG. Ünther, Henrik LaaschRequires cookie*
 Title    Local Anesthetic Binding to Thylakoid Membranes. Relation to Inhibition of Light-Induced Membrane Energization and Photophosphorylation  
 Abstract    The association o f the lipophilic tertiary amine and local anesthetic dibucaine with osm oti-cally shocked chloroplasts o f Spinacia oleracea L. cv. M onatol was investigated. Dibucaine, known as an effective inhibitor o f thylakoid membrane energization and A TP synthesis, ex­ hibited three distinct binding classes with chloroplasts: partitioning in the lipid phase o f the membranes, electrostatic screening o f negative electrical charges on the thylakoid surface and light-induced association o f an as yet unknown nature. Evidence is presented that the mecha­ nism o f inhibition o f the transthylakoid pH gradient, ApH, by dibucaine is distinct from 'clas­ sical' amine-type uncoupling: The inhibitory effect o f dibucaine on ApH was independent o f the initial strength o f ApH. Light-induced dibucaine binding was independent o f the volum e o f the intrathylakoid space and o f the strength o f ApH as varied by medium pH. Judged from a comparison o f the data on dibucaine binding and on inhibition o f ApH and photophosphory­ lation, dibucaine bound via partitioning in the membrane lipid phase is responsible for the un-coupler-like effects o f the local anesthetic. A mechanism for the inhibition o f thylakoid energi­ zation by local anesthetic amines is discussed. 
  Reference    Z. Naturforsch. 46c, 79—8 (1991); received September 21 1990 
  Published    1991 
  Keywords    Chloroplast, Local Anesthetic, Dibucaine, Uncoupling, Photophosphorylation, Amine Bind­ ing 
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 TEI-XML for    default:Reihe_C/46/ZNC-1991-46c-0079.pdf 
 Identifier    ZNC-1991-46c-0079 
 Volume    46