Coupling atomic force microscopy and mass spectrometry for protein analysis
Andrade, A.C.1; Silva, L.P.2; Azevedo, R.B. 2; Cunha, R.B.1,3; Sousa, M.V.1
1Laboratory of Biochemistry and Protein Chemistry, Department of Cell Biology, Institute of Biology, University of Brasilia, Brazil; 2Laboratory of Morphology and Morphogenesis, Department of Genetics and Morphology, Institute of Biology, University of Brasilia 70910-900, Brazil; 3Department of Analytical Chemistry, Institute of Chemistry, University of Brasilia, Brazil
Atomic force microscopy (AFM) and mass spectrometry (MS) are two important tools to investigate structures and interactions of biological macromolecules. Both techniques are widely used in a variety of applications in proteomics and other fields. In this work we describe a new procedure for off-line coupling of atomic force microscopy and mass spectrometry. Using this procedure, it was possible to ionize and analyze AFM imaged proteins molecules by MALDI-MS on the same mica support used for the previous protein imaging analysis. Generally, the same oligomeric structures observed by AFM were observed as well by MALDI-MS. Nevertheless, in some cases, AFM analysis showed oligomeric structures not observed by MS analysis. We postulate that the oligomers were probably dissociated in the presence of acid and organic solvents in matrix solution. The laser energy transferred to the protein complex might have contributed for such dissociation. The correlation between the molecular mass predicted by topographical volume of imaged proteins and the former measured by MALDI-MS is precisely linear. Thus, we demonstrate here the feasibility of coupling two fundamental tools in current proteomics (AFM and MS), since our procedure was capable of detecting a protein by MALDI-MS just after it was imaged by AFM. The combination of these two techniques in tandem may constitute a powerful approach for investigation of biomolecular structures and assemblies.
(Support: CAPES)
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