Electrospray Ionisation

[Genepro]

Hi,

I am trying to check the size of my histidine-tagged recombinant protein by mass spectrometry. My protein is 22.92kDa and I heard that eletrospray ionisation method is the right way to analyze it rather than MALDI-TOF (used for peptides mostly). Can anyone explain the reason behind this?

Thanks in advance..

Genepro

[SMC]

Hi,

I am not an expert in the field, but I would think that ESI is the better choice, since you get a cluster of different charge states of the same protein. Deconvolution permits determination of relatively accurate masses. The reason for the many charge states is that ESI is quite a gentle ionisation method.
MALDI on the other hand mostly leads to singly charged species. That is that you have to detect at round about 20kDa. However, the detection sensitivity decreases with increasing mass (unless you have got a high mass detector); this is since large ions don’t fly as well and thus do not hit the detector hard enough.