To calculate the isoelectric point (pI):
\[ pI = \frac{pKa1 + pKa2}{2} \]
The isoelectric point, often abbreviated as pI, is the pH at which a particular molecule or surface carries no net electrical charge. This concept is often applied to proteins, which can have both positive and negative charges on their amino acids. At the isoelectric point, the total number of positive and negative charges on the protein are equal, making the overall charge zero. This point is important in various applications, such as protein separation and purification.
Let's assume the following values:
Step 1: Add the dissociation constants:
\[ pKa1 + pKa2 = 2.0 + 9.0 = 11.0 \]
Step 2: Divide by 2 to find the isoelectric point:
\[ pI = \frac{11.0}{2} = 5.5 \]