PubChem This link opens in a new windowPubChem is an open chemistry database at the National Institutes of Health (NIH). PubChem records are contributed by hundreds of data sources. PubChem mostly contains small molecules, but also larger molecules such as nucleotides, carbohydrates, lipids, peptides, and chemically-modified macromolecules. They collect information on chemical structures, identifiers, chemical and physical properties, biological activities, patents, health, safety, toxicity data, and many others.