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