Trypsin Digest Cartridge problem

[Alice]

We purchased a trypsin digest cartridge from Applied Biosystem recently and wanted to test our 69k protein. However, only trypsin peptide was shown after digest. We tried lots of ways like slower elution speed but still can't get our peptides.

Anyone has experience about this? Thanks a lot in advance!

[Kostas Petritis]

The trypsin digest cartridge is not very stable but it should work at least in the beginning... so maybe the 69k protein is inhibiting trypsin or maybe it cleaves trypsin?

What are the trypsin fragments you observe? Are they tryptic? Another possibility could be that your protein is extremely difficult to digest so you do not see any peptide from that protein, just the usual trypsin autolysis...