A new amino acid with an acidic side chain has been identified with the following pka values:pKa (-COOH)  =  2.09pKa (-NH3+)    =  9.82pKa (acidic side chain) = 3.85What is the pI?

The isoelectric point (pI) is the pH at which a particular molecule or surface carries no net electrical charge. To calculate the pI of the amino acid in question, we need to consider the pKa values of the groups that can be protonated or deprotonated.

This amino acid has three groups that can lose or gain a proton: the carboxyl group (-COOH), the amino group (-NH3+), and the acidic side chain.

The pKa values are as follows:

• pKa (-COOH) = 2.09
• pKa (-NH3+) = 9.82
• pKa (acidic side chain) = 3.85

Since the side chain is acidic, it will lose a proton at a lower pH compared to the amino group. Therefore, the relevant pKa values for calculating the pI are the pKa of the carboxyl group and the pKa of the side chain.

The pI is calculated as the average of these two pKa values:

pI = (pKa1 + pKa2) / 2 pI = (2.09 + 3.85) / 2 pI = 5.94 / 2 pI = 2.97

So, the pI of this new amino acid is 2.97.