PDB(Protein Data Bank)..

PDB is a repository for 3-D biological macromolecular structure.
It includes:
-protein
-nucleic acids
-viruses

Obtained by:
-X-Ray crystallography(80%)
-NMR spectroscopy(16%)

Commonly used software
-pdb_extract
-ADIT
-PDB Validatuon Suite

Images of Trypsin..