Peptides are chains of amino acids joined by peptide bonds. Where a chain stops being called a peptide and starts being called a protein is a matter of convention rather than chemistry, which is one reason the literature can seem inconsistent about the same molecule.

What is not a matter of convention is sequence. The order of residues fixes the molecular formula, the molecular weight, and how the chain folds — so questions about what a compound is reduce to questions about sequence, and that is what identity testing sets out to answer.

What this topic covers

Fundamentals holds the material every other topic assumes you already have: what a peptide is structurally, how sequence and molecular weight define identity, the difference between in-vitro and preclinical model systems, and the registry identifiers a compound is looked up by.

It stops short of three things, each of which has a topic of its own. Structure and identity data for an individual compound belong to Compound Guides. Receptor biology and the single, dual and triple agonist classes belong to Metabolic Research. Anything you actually do at the bench — reconstitution, storage, reading a certificate — belongs to Lab Practice.

How to read it

Start with the pillar guide below, Understanding Research Peptides in the Laboratory, and read it in the order it is written: what a research peptide is, why reference compound is the operative phrase, how in-vitro systems differ from preclinical models, handling, and what documentation is for. Each of the other topics picks up where one of those sections leaves off.

After that, the next step depends on the question. If you are about to open a vial, go to Lab Practice. If you want identity data for one compound, the product page carries it directly — CAS number, molecular formula, molecular weight and PubChem CID, for every compound whose identity could be verified against a public chemical database. Where a value could not be verified it is left off rather than filled, so some pages carry no identity block at all.

Vocabulary that belongs here

These glossary entries are fundamentals terms rather than handling terms:

The guide count at the top of this page is the whole of the topic today; it grows as new material is written and checked against the editorial policy. Where a guide has been through scientific review, a reviewer line appears at the top of it — and where there is no reviewer line, that check has not happened.