Comet parameter: variable_N_terminus_distance

Example:
variable_N_terminus_distance = -1   Applied to all peptides
variable_N_terminus_distance = 0     Applied only to peptides containing protein's n-terminus
variable_N_terminus_distance = 1     Applied on any peptide who's n-terminus is one of first 2 residues (n-term & next 1)
variable_N_terminus_distance = 12   Applied on any peptide who's n-terminus is one of first 13 residues (n-term & next 12)