Kinetics of hydrolysis of poly(alkylene amidophosphate)s with amino acids or dipeptides as the side groups was studied by P-31 NMR at pH 1.5, 6.5, and 8.5. The direction of hydrolysis and the relative rate coefficients of breaking P-O bonds in the main chain and P-N bonds in the side groups depend strongly on the pH of the medium of hydrolysis. The P-N (amide) bond hydrolyzes much faster than the P-O (ester) bond in acidic and close to neutral conditions (negligible P-O hydrolysis), whereas above pH greater than or equal to 8.5 these differences are much smaller. For instance, for 4-Ala the rate coefficients of hydrolysis are equal (in H2O at 37 degreesC and pH 8.5) to 1.9 x 10(-8) s(-1) and 1.0 x 10(-9) s(-1) for the P-N and P-O bonds, respectively, quite different from the values found for the low molecular model 2 (0 and 1.4 x 10(-7) s(-1), respectively).