Fig. 2.

Apparent first-order rate constant of peptide bond formation, calculated from integrated ¹H NMR intensities of the reactant and product, plotted as a function of unprotonated amine, with a fixed concentration (0.25 M) of total amine at varying pH values at 40°C. Similar results were obtained at fixed pH by varying the concentration of total amine (data not shown). The linear dependence of the rate shows that only one molecule of Tris participates in the ester aminolysis reaction.