✍ Scribed by P. R. Andrews
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The molecrilar orbital method PC'IIN is applied 10 eight N-n~ot~osi~bstituted amides.
Experimentally known geometric properties are reasoilably predicted by minimization of total energy with respect to molecular geometry. The bame procedure shows that molecular deformations during rotation around the peptide bond significantly lower calculated barriers. Experimental heats of activation and the free-energy changes associated with cis-trans isomerism are in good agreement with those calculated, which include qualitative estimates of configurational entropy Contributions to the isomerism energies. Both the calculations and revised infrared data indicate that M-phenylurethane, which has been used as a model for the cis peptide bond, should be predominantly lruns. However the variations in rotational barriers and czs-trans isomerism energies among the AY-moilosubstituted amides provide no reason to suppose that the cis peptide bond should be excluded from stable protein conformations.
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The stability and kinetics of unfolding and refolding of the P167T mutant of the TEM-1 p-lactamase have been investigated as a function of guanidine hydrochloride concentration. The activity of the mutant enzyme was not significantly modified, which strongly suggests that the Glu166Thr167 peptide bo
We wished to test the hypothesis that the non proline cis to trans isomerization of the peptide bond at position 167 in the S. aureus -lactamase PC1 exerts a significant controlling effect on the folding pathway of this enzyme. The previous data presented in support of this hypothesis could not rul