Comet parameter: peptide_mass_units
         
         - This parameter controls the units applied to the peptide_mass_tolerance parameter.
         
- Valid values are 0, 1, and 2.
         
- Set this parameter to 0 for amu.
         
- Set this parameter to 1 for mmu.
         
- Set this parameter to 2 for ppm.
         
- The default value is "0" if this parameter is missing.
         
Example:
         
peptide_mass_units = 0
         
peptide_mass_units = 1
         
peptide_mass_units = 2