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1988 (1)
1982 (1)
1Author    H. Hauer, H.-D Lüdemann, R. JaenickeRequires cookie*
 Title    Free Activation Energies and Activation Volumes for the Amide Rotation in Some Peptides Studied by High Pressure 'H-High Resolution NMR  
 Abstract    From the pressure dependence o f !H high resolution N M R spectra o f two dipeptides (glycylsarcosine and N-acetyl-L-proline-NH-methylamide in the range 0.1 MPa <.p< . 150 MPa the activation volumes A V* for the am ide rotation are derived. This conform ational transition is characterized for glycylsarcosine by A V* = 4 ± 1 cm3 • m ol-1 and for. the proline derivative by AV* = 1 .5 ± 1 cm3 • m ol-1. From the given results the m axim um contribution o f proline cis ^ trans isomerisation to the pressure dependence o f the rate o f reactivation of proteins can be estimated to ~ — 30% per M Pa and proline present. 
  Reference    Z. Naturforsch. 37c, 51—56 (1982); received Septem ber 221981 
  Published    1982 
  Keywords    Activation Volume, High Pressure, NM R, Peptides, Proline-Isom erization 
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 TEI-XML for    default:Reihe_C/37/ZNC-1982-37c-0051.pdf 
 Identifier    ZNC-1982-37c-0051 
 Volume    37 
2Author    Wilhelm HasselbachRequires cookie*
 Title    Pressure Effects on the Interactions of the Sarcoplasmic Reticulum Calcium Transport Enzyme with Calcium and Dinitrophenyl Phosphate  
 Abstract    The effect of hydrostatic pressure on the calcium-dependent hydrolysis of dinitrophenyl phos-phate by the sarcoplasmic calcium transport enzyme has been studied. The magnesium dinitro-phenyl phosphate complex is the true substrate of the enzyme (K — 7000 M" 1) by which it is hydrolyzed at 20 °C with a turnover rate of 4 s -1 . Activation by calcium ions occurs between 0.1 and 1 piM as observed for ATP hydrolysis. The activation volume of the enzyme saturated with both ligands exhibits pronounced pressure-dependence, rising from 25 ml/mol at atmospheric pressure to 80 ml/mol at 100 MPa. The apparent binding volumes for magnesium dinitrophenyl phosphate and calcium are likewise pressure-dependent. The volume changes connected with the binding of magnesium dinitrophenyl phosphate is quite small approaching zero at 100 MPa. The apparent binding volume for calcium greatly increases with pressure from 35 ml/mol at atmos-pheric pressure to 150 ml/mol at 70 MPa. A nearly constant binding volume of approximately 40 ml/mol results if the effect of pressure on the respective rate constants that contribute to the apparent binding constant, is taken into account. The pressure-dependence of enzyme activity at subsaturating calcium concentrations yields an activation volume of 250 ml/mol related to the rate of calcium binding indicating the occurrence of a transient large volume expansion of the enzyme complex. The volume changes observed for the calcium-dependent interaction of the enzyme with magnesium dinitrophenyl phosphate well agree with that found for magnesium p-nitrophenyl phosphate (W. Hasselbach and L. Stephan, Z. Naturforsch. 42c, 641-652 (1987)) indicating that the found volume changes are intrinsic properties of the transport enzyme, independent of the respective energy donor. 
  Reference    Z. Naturforsch. 43c, 929—937 (1988); received September 29 1988 
  Published    1988 
  Keywords    Sarcoplasmic Reticulum, Calcium-Dependent Dinitrophenyl Phosphate Hydrolysis, Activation Volume, Binding Volume 
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 TEI-XML for    default:Reihe_C/43/ZNC-1988-43c-0929.pdf 
 Identifier    ZNC-1988-43c-0929 
 Volume    43