Performance of the target alternative k-permuted decoy databases used with the OMSSA database search program using spectra from 80 unmodified neuropeptides.

aTarget: database of 236 neuropeptide sequences; K103: k-permuted decoy database size of 236,000 peptides; K104: k-permuted decoy database size = 2,360,000 peptides; K105: k-permuted decoy database size = 23,600,000 peptides; K106: k-permuted decoy database size = 236,000,000 peptides.
b# ions: permutation p-values computed for the number of matched b- and y-ions. Lambda: permutation p-values computed from the Poisson mean of matches. p-value: permutation p-values computed from the p-value reported by the OMSSA for the matches. E-value: permutation p-values computed using OMSSA E-values.
cSignificance threshold (t) for matched to be considered significant at p-value<1×10−t.
dIncorrect: the program provided an incorrect match.
eCumulative number of peptides with p-value<1×10−2.
fCumulative number of peptides with p-value<1×10−4.
Performance of the target alternative k-permuted decoy databases used with the OMSSA database search program using spectra from 80 unmodified neuropeptides.