Structures of proteins, nucleic acids, and complex assemblies. Use the RCSB PDB to find sequence, structure and function, and to visualize, download, and analyze molecules.
PubChem provides information on the biological activities of small molecules. Organized as three linked databases within the NCBI's Entrez: PubChem Substance, PubChem Compound, and PubChem BioAssay. PubChem also provides a fast chemical similarity search tool.