<p>You have to go through the sequence one by one and look at the pKas of all the side chains, as well as the amino and carboxylic pKas for the ends. Use the given pH and pKas along with the henderson-hasselbalch equation to determine which form is favored at that particular pH, which will give you the net charge after summation. </p>
<p>Does anyone know why you need twice the amount of equivalents you’d think you need when doing a transesterification with an amine? For example on page 55 it says 4 equivalents of the amine when you’d only need two, and on 94 ad 197(b) it shows two equivalents when you only need one.</p>