Scientific Glossary

Amino acids share a common structure: a central carbon (alpha-carbon) bonded to an amino group (-NH2), a carboxyl group (-COOH), a hydrogen, and a variable side chain (R group). The R group determines each amino acid's properties — charged, polar, nonpolar, aromatic. Peptide bonds form between the carboxyl of one amino acid and the amino group of the next, with water released. The sequence and composition of amino acids determines a peptide's three-dimensional shape, receptor affinity, and function.

Dipeptides (2 AA) and tripeptides (3 AA) are the smallest functional peptide units. Despite their small size, they can exert potent biological effects. KPV (Lys-Pro-Val) is a tripeptide with studied anti-inflammatory properties. GHK (Gly-His-Lys) is a tripeptide with broad tissue-remodeling research. Pinealon (Glu-Asp-Arg) and Vilon (Lys-Glu) are dipeptide/tripeptide combinations from Russian longevity research. Small size generally improves oral bioavailability compared to larger peptides.

Peptide bonds are amide bonds (-CO-NH-) that link amino acids into chains. The bond has partial double-bond character due to electron delocalization, making it planar and relatively rigid. This rigidity constrains peptide backbone conformation. Peptide bonds are cleaved by proteases (hydrolysis), which is why orally administered peptides are typically degraded in the gut. Chemical modifications that protect peptide bonds (N-methylation, D-amino acid substitution, cyclization) are research strategies to improve oral or metabolic stability.