All different types of post translational modifications can potentially be located/analyzed using mass spectrometric approaches. This includes purposefully modified sites such as sites of cross linking, incorporation of selenomethionine (seen below), deamidation (seen below), 13C enriched protein, etc.
Please contact us if you have specific protein/peptides/oligo modification that you wish to have MS analysis carried out for, as different protocols may be necessary to optimize for the detection of the PTM.
Using the high resolution of our FT-ICR MS instrument at ~150,000 for m/z at 995, we can distinguish (isotopically separate) two peptides which are deamidation pairs with mass difference of 0.9838 Da. Note that the monoisotopic of the OH- specie is baseline resolved from the second isotopic peak of the NH2-specie.