While both peptides and proteins are composed of amino acids linked by peptide bonds, they differ in size, structure, and function. Peptides are generally defined as chains of fewer than 50 amino acids, while proteins contain 50 or more residues and typically fold into complex three-dimensional structures.
Proteins rely on their tertiary and quaternary structures for biological activity, whereas most peptides are flexible molecules that adopt their active conformation only upon binding to their target receptor. This structural simplicity makes peptides easier to synthesize, modify, and study.
In research applications, peptides offer several advantages: they can be produced chemically with high purity, they are generally more stable than proteins in certain formulations, and they can be designed to target specific receptors with high selectivity.
However, peptides tend to have shorter half-lives in biological systems due to rapid enzymatic degradation. Researchers address this through various modification strategies, including amino acid substitutions, cyclization, PEGylation, and incorporation of D-amino acids or other non-natural residues.