How to calculate the pI of a peptide?? Hello everyone, I am hoping someone can shed some light on this question. I know the general idea behind it but i cant seem to put the nail in the coffin. The sequence is ATLDAK and it asks to : Calculate its approximate pI This is what i have so far: ........nT-A......T.....L..... D.... A.... K-...... cT pK...9.87.......................3.9........10.54...2.16 I know that there are 2 positive charges so this results in requiring to be deprotinated with two equivalents of base. I also know that the pI is given by the two amino acids that give the zwiterionic charge, or simply zero charge. However, how to identify those amino acids....???? Help please