From SPCTools
# spectrast.usermods
# This file should contain specifications of amino acid modifications of peptides.
# Specifications are of the form <amino acid>[<tag>]|<mass change>|<mod type>. For example,
M[foo]|+12.34567|MyMod
# Note that tag and mod type must not start with a number, and should not contain space or special characters
# Leave blank the [<tag>] unless you have a strong reason to do so. SpectraST will construct one that conforms to TPP convention.
# (Note that some components of TPP may fail if you specify your own tag.) For example,
C|+57.021464|Carbamidomethyl
# Leave blank the mod type if you don’t know a good name for it, or don’t know if the mod is already encoded in SpectraST. For example,
M|+16|
# SpectraST should recognize this is oxidation and use the accurate mass (+15.99491) accordingly.
