N-terminal

In a polypeptide chain, the N-terminal denotes the end of the chain with the NH₂ group and the C-terminal is the other end of the chain which has the group COOH. This amino group can join with carboxyl groups to form a peptide bond and extend the chain.

When writing out a protein seqeunce the N-terminal is written on the left and the C-terminal on the left.