Example

minimize rigid
  nstep=60   drop=10.  
  group=( residue 1:6 )    group=( residue 7:19 ) 
  group=( residue 20:22 )  group=( residue 23:30 )
  group=( residue 31:35 )  group=( residue 36:41 )
  group=( residue 42:46 )  
end