PubChemOpen cheminformatics database on properties and biological activities of small molecules, primarily of interest to pharmaceutical and chemical genomics researchers, plus 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, etc. Records are contributed by many sources, including government agencies, publishers, vendors, and individual researchers. (NIH/NLM)