Peptides are commonly categorized based on the number of amino acids they contain. A dipeptide, consisting of two amino acids, is the shortest peptide, while a tripeptide contains three amino acids. Oligopeptides refer to shorter peptides with relatively few amino acids, typically less than ten. On the other hand, polypeptides generally comprise more than ten amino acids. Larger peptides, composed of over 40-50 amino acids, are commonly referred to as proteins.
Although the number of amino acids is a primary factor in distinguishing between peptides and proteins, exceptions can occur. Certain longer peptides, like amyloid beta, have been classified as proteins, and smaller proteins, such as insulin, can be referred to as peptides in specific cases. For a deeper understanding of the similarities and differences between peptides and proteins, please refer to our Peptides Vs. Proteins page.
Amino Acids: Peptides are composed of amino acids, which are molecules containing both amine and carboxyl functional groups. Alpha-amino acids serve as the fundamental building blocks for peptide synthesis.
Cyclic Peptides: Cyclic peptides form a ring structure in their amino acid sequence, deviating from the linear chain configuration. Examples of cyclic peptides include melanotan-2 and PT-141 (Bremelanotide).
Peptide Sequence: The peptide sequence represents the specific order in which amino acid residues are connected through peptide bonds.
Peptide Bond: A peptide bond is a covalent bond formed when the carboxyl group of one amino acid reacts with the amino group of another amino acid, resulting in a condensation reaction with the release of a water molecule.
Peptide Mapping: Peptide mapping is a method used to validate or determine the amino acid sequence of specific peptides or proteins. It involves enzymatically breaking down the peptide or protein and examining the resulting pattern of amino acid or nucleotide base sequences.
Peptide Mimetics: Peptide mimetics are molecules that mimic the biological activity of hormones, cytokines, enzyme substrates, viruses, or other biomolecules. They can be natural peptides, synthetically modified peptides, or any other molecule that performs the desired function.
Peptide Fingerprint: A peptide fingerprint is a chromatographic pattern generated by partially hydrolyzing the peptide, breaking it into fragments, and mapping those fragments in a two-dimensional manner.
Peptide Library: A peptide library consists of numerous peptides that systematically combine different amino acids. Peptide libraries are commonly used in biochemical and pharmaceutical research on proteins. Solid-phase peptide synthesis is the most common technique for preparing peptide libraries.