Dear MODELLER users

I want to mutate a single residue in a model. I run the TOP file given in the tutorial (with 1fas.pdb) successfully. There are two options given: in one case the specified residue is mutated whenever it appears in the structure. This runs fine. But in case of the second option, (where a segment is specified) all the residues are mutated instead of one.

Following is the part of the TOP file.( to change residue 14 to Cys) # The second example is commented out; it selects residues '1' and '10'. SET SELECTION_SEARCH = 'SEGMENT', SELECTION_FROM = 'ALL' PICK_ATOMS SELECTION_SEGMENT = '14' '14', SELECTION_STATUS = 'INITIALIZE'

# Mutate the selected residues into HSD residues (neutral HIS): MUTATE_MODEL RESIDUE_TYPE = 'CYS'

This works perfectly fine with 1fas.pdb but not with my model. Can you point out where I am going wrong.

regards