Unique Input Statements
CLUSTER <Name> N([RESIDUES <Residue range>]) -
{CHAINS N(<Chain>) |
NCS N(<Chain> <Operator>)}
The CLUSTER statement is used to define the chains which are related by noncrystallographic symmetry, and the portions of those chains for which the correspondence is valid. At least one CLUSTER statement must be given each time NCS is ran. If a residue range is given the sequence file must be INCLUDEd.
The CHAINS options will continue reading chain names until the end of line is reached. Therefore all RESIDUES options must come before it.
The NCS option is used to define the name of the operator which moves that chain onto the prototype. The actual operators are supplied on TRANSFORMATION statements. The NCS option will continue to read pairs of chain names and operator names until the end of line is reached. Therefore CHAINS and NCS must be entered on separate CLUSTER statements.
WEIGHT NCS <Value>
This statement is used to specify the weight of the noncrystallographic symmetry in relation to the other types of restraints currently being used. The weight should be chosen so that the resulting agreement between related molecules matches your expectations. Large molecules with good noncrystallographic symmetry should agree with an r.m.s. comparable to the error in the coordinates. The actual r.m.s. may be higher if there are real differences between the mates.
There is a great deal of flexibility in the arrangement of the weight definitions. The weights can be defined in any order, and can be placed on several different WEIGHT statements. NCS will ignore weights from other modules.