Parameter: modification


Specifies a dynamic mass adjustment to be applied to all indicated amino acids during spectral analysis. Peptides containing the indicated amino acids are tested with and without the dynamic modification mass. Amino acids are identified by their single letter designation. N-terminal and C-terminal dynamic peptide modifications are designated by n and c, respectively. The relative mass difference, positive or negative, is listed after the amino acid, separated by a space. If multiple dynamic modification masses are desired, including to the same amino acid, use multiple modification declarations.

NOTE: When the mass value of modification is zero, the parameter is ignored. Some configuration files may have the value set to zero, simply to have a modification placeholder in the file.


[Amino Acid] [Mass]


1.0 - present


To indicate possible oxidation of methionine:

modification = M 15.9949