CYANA Variable: expand

Initial value: 1

This variable controls the automatic, internal expansion of distance restraints that involve pseudoatoms into ambiguous distance restraints with the corresponding hydrogen atoms. If the variable has the value 1, the expansions will take place, if it has the value 0, no expansions will be made and distance restraints involving pseudo atoms will be used as they are.

For instance, if expand = 1, an input restraint between HA and QB of Ala will effectively be interpreted as an ambiguous distance restraint with the three assignments HA-HB1, HA-HB2, and HA-HB3, and it is the r^-6 sum of these three distances that will be checked against the upper distance bound. Alternatively, if expand = 0, it is the single distance HA-QB that will be checked against the upper distance bound.