(b) the dipeptide aspartyl-lysine consists of an aspartate residue (side chain contains a carboxylic acid group) attached to a lysine residue (side chain contains an amino group). calculate the net charge on aspartyl-lysine at ph 2 and ph 12. calculate the charge to the nearest 0.5 of a unit and show all workings. assume the following pka values a-carboxyl group 2; side chain carboxyl group amino group 11. a calculator is not required to answer this question 4; a-amino group 9; side-chain