Dear colleagues,

I try to enrich phosphorylated peptides (or proteins) prior to mass spectrometry. I have so far tried an IMAC HPLC column kindly provided by Dionex and the ProteoExtract Phosphopeptide Capture Kit (also IMAC from CALBIOCHEM). Both these approaches seemed to work, @ least with standard substances, however, only when using rather large concentrations (such as 40pmol absolute entering the respective process).

Any experience in this field and thus any “helpful kicksâ€