7 | | July 12, 2020: **PDB 2-character chain IDs**. Column 21 in PDB file, normally blank, is now treated as the second character of the chain ID if appropriate. Previously, non-blanks in that column were treated as the fourth character of the residue name (needed in some Amber files). Now that column is treated as part of the chain ID as long as that is consistent across all the residues in the chain, otherwise as part of the residue name. |
| 7 | July 12, 2020: **PDB 2-character chain IDs**. Column 21 in a PDB file, normally blank, is now treated as the second character of the chain ID if appropriate. Previously, non-blanks in that column were treated as the fourth character of the residue name (needed in some Amber files). Now that column is treated as part of the chain ID as long as that is consistent across all the residues in the chain, otherwise as part of the residue name. |