Abstract Summary: The Alanine Scanning Energetics database (ASEdb) is a searchable database of single alanine mutations in protein–protein, protein–nucleic acid, and protein–small molecule interactions for which binding affinities have been experimentally determined. In cases where structures are available, it contains surface areas of the mutated side chain and links to the PDB entries. It is useful for studying the contribution of single amino acids to the energetics of protein interactions, and can be updated by researchers as new data are generated. Availability: ASEdb is accessible on the Web at http://www.asedb.org Contact: [email protected] * To whom correspondence should be addressed.