Translations:Amino acid/32/en

For amino acids with charged side chains, the pK_a of the side chain is involved. Thus for aspartate or glutamate with negative side chains, the terminal amino group is essentially entirely in the charged form −NH+
3, but this positive charge needs to be balanced by the state with just one C-terminal carboxylate group is negatively charged. This occurs halfway between the two carboxylate pK_a values: pI = 1/2(pK_a1 + pK_a(R)), where pK_a(R) is the side chain pK_a.