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PubChem

The NIH's public chemical database; a PubChem CID identifies one specific compound record.

PubChem is a public chemical database maintained by the National Center for Biotechnology Information, part of the US National Institutes of Health. It aggregates records from hundreds of contributing sources and is freely accessible without an account.

Each compound record carries a CID — a Compound Identifier — that resolves to structure, molecular formula, molecular weight, synonyms and links to the literature. A CID is therefore a direct route to an independent description of a compound, which makes it a practical cross-check on any identity data a vendor publishes.

It is worth checking rather than trusting. A CID that resolves to a different molecule than the page claims is a real failure mode: this catalog previously linked GHK-Cu to an unrelated nine-residue peptide and Tesamorelin to a sea anemone toxin. Every CID published here is now fetched and confirmed to match the stated formula and compound before release.

Topic: Fundamentals

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Guides that cover this

Semax (MEHFPGP): A Research Guide to Its Identity, Binding Site and Preclinical Record

Semax is a synthetic heptapeptide joining the ACTH(4-7) fragment to a C-terminal Pro-Gly-Pro extension. This guide covers its verified identity data, the nanomolar calcium-dependent binding site measured in rat forebrain membranes, the assay readouts it has been studied with, and the gaps left open.

Melanotan II (MT-2): A Research Guide

Melanotan II is a cyclic lactam analog of alpha-MSH designed in 1989 to lock a flexible hormone fragment into one conformation. It binds four of the five melanocortin receptors, which makes it a powerful reference ligand and a poor subtype probe. What has been measured, in which systems, and where the record stops.

Glutathione (GSH): Structure, Enzymology, and How Its Redox State Is Measured

Glutathione is not a signaling peptide — it is the most abundant low-molecular-weight thiol cells synthesize. A guide to its biosynthesis, the three enzyme families that require it, the Nernst arithmetic behind GSH/GSSG, and what the literature still does not know.

Semaglutide: Receptor Pharmacology, Structure and Analytical Identity

A research guide to semaglutide: the three engineered changes to the GLP-1 backbone, the class B receptor it binds, what cryo-EM and validated antibodies actually show, and why a purity percentage on a certificate does not establish that a vial contains this molecule.

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