How should the ends of the peptide be handled? Keep it free or block it?

Peptides are used to simulate proteins. In order to mimic the performance of proteins, we need to synthesize polypeptides with similar structures and charges to proteins. When a peptide is "cut out" from a protein, the number of charges at both ends will be different from that of the gene body protein. We need to change the compositing strategy to make them consistent. In general: If the sequence is from the C-terminus of the protein, shield the N-terminus by acetylation; if it is a sequence from the N-terminus of the protein, shield the C-terminus by amidation; if it is from the middle part of the protein, use acetylation and amidation to shield the Both ends are shielded.