小中大
choose the desired types of modified residues to be searched:
a.specify modifications desired for cysteine residues to generate theoretical masses to match those cysteine-containing peptides that have been reduced and then alkylated with iodoacetic acid(carboxymethylation),iodoacetamide(carbamidomethylation),or 4-vinylpyridene(pyridylethylation)
b.specify additional chemical modifications of proteins that can be generated during PAGE,such as oxidation of methionine residues and acrylamide modification of cysteine residues.
c.specify peptide mass changes due to known posttranslational modifications,such as conversion of N-terminal glutamine to pyroglutamic acid,and phosphorylation of serine,threonine,and tyrosine.
d.For any database entry with a methionine at the N-terminus,specify whether the N-terminal peptide is to be considered in its original form or in a form where the methionine is removed and the penultimate amino acid is acetylated.
如果不是你自己做的质谱，最好咨询一下给你作质谱的老师。
