Comet parameter: peptide_mass_tolerance
         
         - This parameter controls the mass tolerance value.
         
- The mass tolerance is set at +/- the specified number i.e. an entered value of "1.0" applies a -1.0 to +1.0 tolerance.
         
- The units of the mass tolerance is controlled by the parameter "peptide_mass_units".
         
- The default value is "3.0" if this parameter is missing.
         
Example:
         
peptide_mass_tolerance = 3.0
         
peptide_mass_tolerance = 10.0