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  • 1
    Electronic Resource
    Electronic Resource
    Control of chloroplast ATP synthase (CF0CF1) activity by Δ pH (1998)
    Springer
    Photosynthesis research 57 (1998), S. 287-295 
    Details
    ISSN: 1573-5079
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A biphasic decay of the thiol modulated ATPase activity is observed at fast deenergization of the thylakoids achieved by turning off the light and simultaneous injection of the uncoupler nigericin. Most likely the rapid phase (τ1/2 = 5 s) represents an unstable, active Ef-form of the enzyme which decays to a less active, but more stable Es-form. The two forms have different substrate affinities. Deactivation and reactivation kinetics indicate that the transition from the Ef- to the Es-form is reversible, requires a low proton gradient (1 to 2 ΔpH units) and most probably involves the release and binding, respectively, of two protons from the thylakoid lumen phase to sites which have an apparent pK of 6.6. The Es-form decays to the inactive Ei-form with a half time of 90 s. Reactivation of the completely deactivated enzyme is a two-stage process comprising protonation of sites with a pK of 6.8 followed by protonation of sites of pK 4.9. The intermediate Es'-form has a decay time which is similar to that of the Es-form, but a different Km for ATP. Therefore we conclude that activation is not the exact reversal of deactivation. The results are discussed in terms of a model of ΔμH+-linked activation/deactivation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006006907945
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Coordination Modes of 2,5-Di(tert-butyl)pyrrolide - Crystal Structures of HPyr*, Pyr*H·thf, (thf)2LiPyr*, and [(Me3Si)3C-Zn]2(μ-Cl)(μ-Pyr*) (Pyr* = 2,5-tBu2NC4H2) (1998)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 1175-1182 
    Details
    ISSN: 1434-1948
    Keywords: Hydrogen bonds ; Indium ; Lithium ; Nitrogen heterocycles ; Zinc ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The lithiation of 2,5-di(tert-butyl)pyrrole (1) yields bis(tetrahydrofuran)lithium 2,5-di(tert-butyl)pyrrolide (2), which is monomeric in solution as well as in the solid state. Due to the coordination number of three for the lithium atom, short Li-O and Li-N bond lengths of 193 pm are observed. The metathesis reaction of 2 with tris(trimethylsilyl)-methylzinc chloride (3) gives colorless bis[tris(trimethyl-silyl)methylzinc] chloride 2,5-di(tert-butyl)pyrrolide (4). The pyrrolide ligand and the chlorine atom bridge the zinc atoms. One of the zinc atoms is bonded to the nitrogen atom of the pyrrolide substituent, while the other bonds to the opposite C-C bond. At 215 pm, the Zn-N bond is very long compared to those in alkylzinc amides, whereas the Zn-C distances lie in the range of Zn-C bond lengths found between zinc and η5-bonded cyclopentadienide ligands. The molecular structures of 1 and of the low-melting THF adduct 1·thf show a similar 2,5-di(tert-butyl)pyrrole molecule, but in the latter case a weak N-H···O bond is observed (N-H 97 pm, O···H 199 pm).
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
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