The patch statement refers to a patch
residue (PRESidue), which consists of additions of atoms by the add
statement, modifications by the modify statement, or deletions by the
delete statement. The order of modified and added atoms within a
residue is constrained by group statements in the original RESIdue
statement, in addition to those in the patch residue.
A patch can establish chain linkages, such as peptide
bonds, chain termini, disulfide bridges, and covalent links to ligands.
Subsections