Specifies a dynamic mass adjustment to be applied to protein N-terminal amino acids during spectral analysis. Peptides containing the protein N-termnius are tested with and without the dynamic modification mass. The N-terminus includes both the leading and 2nd amino acid, in case of removal of the leading amino acid. The relative mass difference can be any non-zero value. If multiple dynamic protein N-terminal modification masses are desired, use multiple modification_protN declarations.
NOTE: When the mass value of modification_protN is zero, the parameter is ignored. Some configuration files may have the value set to zero, simply to have a modification_protN placeholder in the file.
1.5.4 - present
To indicate possible protein N-terminal acetylation: modification_protN = 42.01055