Here Label is the chain letter and residue number for one or more atoms. For example: OPT("B 4"=4.0) or OPT("A 1157"=4.0). Spaces are not important, but using spaces makes it easier to read the atom label If the chain letter is not important, it can be replaced with an asterisk, e.g., OPT("* 1157"=4.0)
All atoms within n.nn Ångstroms of any atom that has, as part of its PDB atom-label, the chain-letter and residue-number in text "label" will be flagged for optimization. All other atoms will be frozen, i.e., flagged to not be optimized. If NOOPT is present, then the atoms defined by "label" will be flagged to not be optimized; only the atoms within n.nn Ångstroms of any atom defined by "label" will be flagged to be optimized.
Use of this keyword has two advantages. First, the precision of the calculated energy increases, and second, the computational effort is reduced.
This option should not be used with OPT-X or other similar keywords.
All atoms in residues Label1, Label2, etc. will be marked for optimization. All other atoms will be frozen.
See also RAPID.