Description:

Protein Samples are usually diluted in 50:50 Water/Methanol + 0.1% Formic acid to give a protein concentration between 5 and 20 pmol/µL. A 1 µL aliquot is then pipetted into the end of a borosilcate metal coated glass capillary (for image click here) and sprayed into the Q-ToF 2 mass spectrometer.

Spectra are acquired as Intensity vs. m/z (that is mass divided by charge). It is normal to see several charge states for proteins. To see an example spectrum for myoglobin click here. It is an easy task for software to take this data, and generate a 'pseudo- mass spectrum' where each charge-state is corrected (multiplied by the number of charges) to give protein molecular weights.

Write-up:

Samples were made up in 50/50 water/methanol + 0.1% formic acid, loaded into coated borosilicate glass capillaries (Micromass, Manchester, UK) and sprayed into the nano-electrospray ion-source of a Q-ToF 2 mass spectrometer (Micromass, Manchester, UK) in positive ion mode. Charge-states from the resulting spectra were deconvoluted using the MaxEnt algorithm (Micromass, Manchester, UK) to enable determination of exact molecular weights.