When determining the pI of an amino acid containing a titratable team in the R side chain, it is useful to start by composing the structure of this amino acid at physiological pH (pH 7). Lysine, eg, could possibly be displayed by the after diagram.
At physical pH, lysine keeps an internet good charge. Hence, we have to increase the pH of answer to eliminate good fee so that you can achieve the isoelectric point. The pI for lysine is simply the typical of this pKa‘s of the two -NH3 + teams.