Foundation
A ten-chapter pathway from amino acid chemistry through receptor biology to laboratory research practice. No prior background required.
01
Chapter
A peptide is a short chain of amino acids linked by peptide bonds — typically between 2 and 50 residues long. Anything longer is generally called a protein. Despite their small size, peptides act as biology's precision messengers: they bind receptors with high selectivity, regulate hormones, modulate immunity and coordinate tissue repair.
02
Chapter
There is no hard line between a peptide and a protein. By convention, anything under ~50 residues is a peptide; longer chains fold into proteins with stable tertiary structure. Peptides are usually flexible, more easily synthesised chemically, and act primarily as signalling molecules rather than structural or catalytic ones.
03
Chapter
Twenty standard amino acids encode every human peptide and protein. Each carries a unique side chain (R-group) that defines its chemistry — hydrophobic, polar, acidic, basic, aromatic or sulfur-containing. The order of amino acids (the primary sequence) determines folding and biological function.
04
Chapter
When two amino acids join, the carboxyl group of one reacts with the amino group of the other, releasing a molecule of water. This amide linkage — the peptide bond — has partial double-bond character that locks adjacent residues into planar geometry, giving peptides their characteristic backbone rigidity.
05
Chapter
Modern peptides are typically made by solid-phase peptide synthesis (SPPS), pioneered by Bruce Merrifield in 1963. Amino acids are added one at a time to a growing chain anchored to insoluble resin, with protecting groups ensuring only the intended bond forms. The finished peptide is cleaved, purified by HPLC, and freeze-dried.
06
Chapter
Most peptide hormones act at the cell membrane through receptors — they don't enter the cell. Binding triggers conformational changes that activate intracellular cascades (cAMP, calcium, MAP kinase) ultimately altering gene expression and cellular behaviour.
07
Chapter
Receptors are proteins that recognise specific ligands. The dominant family in peptide pharmacology is the G-protein-coupled receptor (GPCR) — seven-transmembrane proteins that transduce signals via heterotrimeric G-proteins. Roughly a third of all approved drugs target GPCRs, including GLP-1 agonists, melanocortin agonists and growth-hormone secretagogues.
08
Chapter
Hormones are chemical messengers released into circulation to act on distant tissues. Peptide hormones — insulin, GH, GLP-1, oxytocin — are produced by endocrine cells and modulate metabolism, growth, reproduction and behaviour.
09
Chapter
Research peptides are tools for studying molecular biology in vitro and in pre-clinical models. Every step — synthesis, purification, characterisation, storage — must meet defined quality standards so experimental data are reproducible.
10
Chapter
Peptide science has a vocabulary of its own — agonists, antagonists, GPCRs, half-life, lyophilisation, COA, HPLC. The SPT glossary translates these into plain English with cross-links to deeper articles.
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