Direct matrix-assisted laser desorption/ionization time-of-flight mass spectrometric identification of proteins on membrane detected by Western blotting and lectin blotting.

We have developed new procedures to identify proteins after they are detected by Western blotting or other interactions such as lectin blotting on membranes. Our method is based on the combination of on-membrane MALDI-TOF mass spectrometry with piezoelectric chemical inkjet technology. Using this method the GroEL, FtsZ, DnaK, and GroES proteins were successfully identified from Escherichia coli after separation on two-dimensional gels, immunostaining, and on-membrane digestion. A glycoprotein detected by lectin blotting with concanavalin A was also identified using this technique.