1. PDB (Protein Data Bank) is the single worldwide repository for the
processing and distribution of 3D biological macromolecular structure data. Structure data from PDB can
be searched at PDB site and viewed using RasMol, Chime, and their derivatives.
2. MMDB is a 3D structure database
at NCBI. It contains a subset of PDB excluding theoretical models. Structure data can
be searched at NCBI site and viewed
For more information on how to visualize 3D structures, check the sections
Visulization of 3D structures and
Visulization of 3D structures on Mac.