P.d.b. -

: The functional form of a molecule (e.g., a four-unit hemoglobin complex), which may differ from the Asymmetric Unit (the smallest portion used to solve the crystal structure).

: Every entry is assigned a unique four-letter/number code (e.g., 4HHB for hemoglobin). P.D.B.

The archive uses several formats to store 3D coordinates and experimental data: Guide to Understanding PDB Data: Biological Assemblies : The functional form of a molecule (e