Because the number of post-translational modifications requiring standardized 
annotation in the PIR-International Protein Sequence Database was large and 
steadily increasing, a database of protein structure modifications was 
constructed in 1993 to assist in producing appropriate feature annotations for 
covalent binding sites, modified sites and cross-links. In 1995 RESID was 
publicly released as a PIR-International text database distributed on CD-ROM and 
accessible through the ATLAS program. In 1998 it was made available on the PIR 
Web site at http://www-nbrf.georgetown.edu/pir/searchdb++ +.html . The RESID 
Database includes such information as: systematic and frequently observed 
alternate names; Chemical s Service registry numbers; atomic formulas and 
weights; enzyme activities; indicators forN-terminal, C-terminal or peptide 
chain cross-link modifications; keywords; and literature citations with database 
cross-references. The RESID Database can be used to predict atomic masses for 
peptides, and is being enhanced to provide molecular structures for graphical 
presentation on the PIR Web site using widely available molecular viewing 
programs.