Scheme 2
Isoelectric point of aminoacids anchored to copolymers. The carboxyl groups have a negative charge (− 1). But one-half of the amino groups and one-half of the R-Groups (–NH3+) have a positive charge, so the sum of their charge is + 1. At pH lower than IP, amine and carboxyl groups are protonated and at values higher than IP, ionizable groups donate protons