refine, potential N-terminus modifications

Syntax

The value of this parameter is an ASCII string, of the format M₁@[,M₂@[,..., M_n@[

where M_i is a floating point number (potential modification mass in Daltons).

Notes

1. No error is produced if [ is not used.
2. If a residue type is listed more than once, the last instance of the residue is used to set the modification.
3. Both positive and negative potential modification masses may be used.

Description

The format of this parameter is the same as the residue, potential modification mass parameter. When a valid string is present for this parameter, a search with cleavage at every residue is performed, and the listed potential N-terminal modifications are tested. This test is done on only the first 50 residues for each protein in the refinement list. If a more general N-terminal modification is desirable, then add a modification string with "[" as the residue to modify into the potential modification list.