Question

Using the provided $p{K}_a$ values for fully protonated proline, determine an isoelectric point at which the amino acid exist mostly in its zwitter ionic form.

Answer 1

A certain pH at which the concentration of the dipolar ion is at its maximum and the concentrations of the anions and cations are equal is called isolelctric point.
The given amino acid is a neutral amino acid.
Given:
$p{K}_1=2.0$
$p{K}_2=10.6$
For neutral amino acid,
$pI=\frac{p{K}_1+p{K}_2}{2}$

$pI=\frac{2.0+10.6}{2}$
$pI=\frac{12.6}{2}$
$pI=6.3$