Chemistry of Succinimido Esters. III.

Abstract

The chemical modification (N-acylation) of bovine serum albumin (BSA) by N-acyloxysuccinimides (1) (CN=28) was studied kinetically at 25°C (7.0≤pH ≤9.0). N-Acylation was competitive with the decomposition of (1) and the rate of which is expressed as V= (k1, d+k2 [BSA]) [(1), ] where K1, d is the first order rate constant for the decomposition of (1) and k2 is the second order rate constant for the N-acylation of BSA by (1).The reactivity of (1) with BSA was in the order of CN=2>CN=3>CN=4 C5H11COONa>C3H7COONa. This order corresponded tentatively to the fluorescence difference spectra of BSA by the addition of sodium carboxylate. These findings indicate hydrophobic interaction between BSA and alkyl group in (1) to possibly accelerate the N-acylation of BSA. This was supported by the chemical modification of BSA in a preparative scale. The rate ratio, k2/k1, d, maximized at about pH 8.0 and increased with increasing CN in (1) for CN≥4 and 10-3k2/k1, d larger than unity.From the above observations, (1) is concluded to be applicable as an N-acyl reagent, to the chemical modification of Lys residues in proteins.