To find the isoelectric point (pI) of lysine, you need to identify the two pKa values that are closest to each other and calculate their average.
Based on the reference, lysine has three pKa values due to its three ionizable groups: the amino group, carboxyl group and the amino group on the side chain. The pKa values that are closest are pK2 and pK3.
Here's the process:
- Identify the relevant pKa values: For lysine, these are the two pKa values associated with the two amino groups. According to the reference, these are pK2 and pK3.
- Calculate the average: Add the two pKa values and divide by two. In the case of lysine, the average of pK2 and pK3 is the pI.
- Reference states: "To determine the pI of lysine, we must find the two pKa values closest to each other and take the average of both of them. Based on the given values, p K 2 a n d p K 3 have the closest pKa values, so we should take their average to find the pI of lysine. The pI of lysine is 10."
Therefore, using the method described in the reference, the pI of lysine is 10.
