Chapter 25.2, Problem 9CC

Interpretation Introduction

Interpretation:

Amino acid having same pI values need to be identified.

Concept introduction:

Amino acids at a particular pH do not migrate in an electric field.  This pH is known as the isoelectric point.  The isoelectric point is also known as isoionic point.  At this isoelectric point the amino acid is neutral.  This means that the zwitterion form predominates more over the other forms.  pI is the isoelectric point and this can be given by average of the pK_a.

$\text{pI=}\frac{{\text{pK}}_{{\text{a}}_{\text{1}}}{\text{+pK}}_{{\text{a}}_{\text{2}}}}{\text{2}}$

If two compounds need to have same pI value means, both the compounds must have a similar structure and same pK_a values.  Possibly arrangement might be different.

To identify: the two amino acids which are expected to have same pI value.