Free activation energies and activation volumes for the amide rotation in some peptides studied by high pressure 1H-high resolution NMR.

From the pressure dependence of 1H high resolution NMR spectra of two dipeptides (glycylsarcosine and N-acetyl-L-proline-NH-methylamide in the range 0.1 MPa less than p less than 150 MPa the activation volumes delta V not equal to for the amide rotation are derived, This conformational transition is characterized for glycylsarcosine by delta V not equal to = 4 +/- 1 cm3 . mol(-1) and for the proline derivative by delta V not equal to = 7.5 +/- 1 cm3 . mol(-1). From the given results the maximum contribution of proline cis in equilibrium with trans isomerisation to the pressure dependence of the rate of reactivation of proteins can be estimated to approximately - 30% per MPa and proline present.