What Peptides Are, How They Are Built, and How to Read One on a Label

A peptide is a short chain of amino acids held together by amide bonds — short enough that the word "protein" does not quite fit, long enough that the chemistry matters. That definition turns up everywhere: in a moisturizer's ingredient list, in a research vial's specification sheet, in a certificate of analysis. This site is built to read all three properly. Five guides, each one a hub for a cluster of detailed pages, all with real numbers, real units and cited sources.

Start with the chemistryPeptides in skincareHandling and testing

Five guides, one topic cluster

What you can look up here

Definitions that settle arguments

Peptide, polypeptide, oligopeptide, protein: where the lines actually sit, how the peptide bond forms, and why a codon specifies an amino acid rather than a peptide.

Labels read line by line

INCI order, the one percent rule, typical molecular-weight ranges quoted for collagen hydrolysates, and how a specification sheet states purity and identity.

Arithmetic, not protocols

Mass, volume and concentration worked through properly — mg per mL, percent solutions, unit conversions and rounding error, for readers documenting research materials.

Evidence you can check

What a certificate of analysis should list, what an independent laboratory report adds, and which gaps matter when you are judging a supplier from public documents.

Start here

How this site is put together

Content is written and fact-checked in-house against public references — PubChem, NCBI Bookshelf, UniProt, FDA labelling guidance and peer-reviewed literature — with every figure traced to a cited source. We publish no sponsored placements, sell nothing, accept no payment for placement, and endorse no vendor. Nothing here is medical advice or a protocol for preparing or administering anything. Read the editorial process for how pages are researched and reviewed, or the disclaimer for the limits of the information.