$\begin{matrix} \overset{\oplus }{\mathop{N}}{{H}_{3}}-CH-CO\overset{\Theta }{\mathop{O}}+{{H}^{\oplus }}\to \\ |\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, \\ R\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, \\ \end{matrix}\begin{matrix} \overset{\oplus }{\mathop{N}}{{H}_{3}}-CH-COOH \\ |\,\,\,\,\,\,\,\,\,\,\,\,\, \\ R\,\,\,\,\,\,\,\,\,\,\,\,\, \\ \end{matrix}$
$\begin{matrix} \underset{X}{\mathop{H}}{{O}_{2}}C-C{{H}_{2}}-CH-C{{O}_{2}}\underset{Z}{\mathop{H}}\, \\ \,\,\,\,\,\,\,\,\,\,\,| \\ \,\,\,\,\,\,\,\,\,\,\,\,\,+N{{H}_{3}} \\ \end{matrix}$
The isoelectric point for the amino acid is