What do you mean by "calculate"? What does your data look like? If you have a somewhat recent spectrometer, the result should be given by m/z ratios with the unit u or Da (the Dalton has been redefined to mean the same as u). The TOF should provide enough resolution so you can determine from the signal fingerprint what the charge number z of your species is. So if you have e.g. determined a charge number z=2, you just multiply the peak center by 2 and you have your mass m.

Dear Aruna Rani

Depending on the number of potentially charged amino acid residues on your protein, you will have rather a range of peaks (an envelope), for example, for z=30, z=31, z=32, and so on. In such case, the resolution of peaks for each protein species (with zero 13C, one 13C, two 13C, and so on) is not always good enough for simple visual recognition. However, the mass spectrometer should have software to calculate it, like MaxEnt in MassLynx (Waters).

Regards

Hi,

In theory it should be possible to determine the molecular mass of your protein from MALDI data (or at least get a rough estimate of its mass), depending on the quality of your data.

The advantage of MALDI is that it, overall, generates low charge states (i.e. 1+, 2+, etc.). The difficult thing is that in order to determine an accurate mass, you need sufficient resolution, which can be tricky with MALDI, especially in the case of generally heterogeneous proteins.

MALDI-TOF/TOF suggests that you performed fragmentation on your sample, but I don't see how that would aid in determining the mass of your protein; do you have any spectra to share? Spectra speak louder than words..

Eef Dirksen is right; my comment was valid for ESI-MS. Thanks Eef Dirksen for clarification.