એસ્પાર્ટિક એસિડનું $pI$ (સમવિભવ બિંદુ) જણાવો.
$pH\,=\,\frac{p{{K}_{1}}\,+\,p{{K}_{2}}}{2}\,=\,\frac{1.88\,+\,3.65}{2}$
$=\frac{5.53}{2}\,=\,2.675\,\approx \,2.77$
At isoelectric point of aspartic acid both carboxylic as well as amino form co-exist.
$\begin{align}
& \begin{matrix}
O\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, \\
||\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, \\
H-O-C-C{{H}_{2}}-C{{H}_{2}}-CH-C{{O}_{2}}H \\
\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,| \\
\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\underset{\oplus }{\mathop{N}}\,{{H}_{3}} \\
\end{matrix}\,\,\,\,\,(p{{K}_{a}}=2) \\
& (p{{K}_{a}}=4)\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,(p{{K}_{a}}=9) \\
\end{align}$