Ion mobility spectrometry focusing on speciation analysis of metals/metalloids bound to carbonic anhydrase

In the present work, traveling wave ion mobility spectrometry-mass spectrometry (TWIMS-MS) was applied to speciation analysis of metalloproteins. The influence of pH on complexation conditions between some metals and bovine carbonic anhydrase was evaluated from pH 6 to 9, as well as the time involved in their complexation (0-24 h). Employing TWIMS-MS, two conformational states of bovine carbonic anhydrase were observed with charge states of +12 and +11; these configurations being evaluated in terms of the folded state of the apo form and this protein (at charge state +11) being linked to barium, lead, copper, and zinc in their divalent forms. Metalloprotein speciation analysis was carried out for copper (Cu+ and Cu2+), lead (Pb2+ and Pb4+), and selenium (Se4+ and Se6+) species complexed with bovine carbonic anhydrase. Mobilities of all complexed species were compared, also considering the apo form of this protein.