On-line bioaffinity-electrospray mass spectrometry for simultaneous detection, identification, and quantification of protein-ligand interactions

J Am Soc Mass Spectrom. 2010 Oct;21(10):1643-8. doi: 10.1016/j.jasms.2010.06.011. Epub 2010 Jun 25.


We describe here an on-line combination of a surface acoustic wave (SAW) biosensor with electrospray ionization mass spectrometry (SAW-ESI-MS) that enables the direct detection, identification, and quantification of affinity-bound ligands from a protein-ligand complex on a biosensor chip. A trapping column was used between the SAW-biosensor and the electrospray mass spectrometer equipped with a micro-guard column, which provides simultaneous sample concentration and desalting for the mass spectrometric analysis of the dissociated ligand. First applications of the on-line SAW-ESI-MS combination include (1), differentiation of β-amyloid (Aβ) epitope peptides bound to anti-Aβ antibodies; (2), the identification of immobilized Substance P peptide-calmodulin complex; (3), identification and quantification of the interaction of 3-nitrotyrosine-modified peptides with nitrotyrosine-specific antibodies; and (4), identification of immobilized anti-α-synuclein-human α-synuclein complex. Quantitative determinations of protein-ligand complexes by SAW yielded dissociation constants (K(D)) from micro-to low nanomolar sample concentrations. The on-line bioaffinity-ESI-MS combination presented here is expected to enable broad bioanalytical application to the simultaneous, label-free determination and quantification of biopolymer-ligand interactions, as diverse as antigen-antibody and lectin-carbohydrate complexes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Antibodies, Immobilized / chemistry
  • Antibodies, Immobilized / metabolism*
  • Antibodies, Monoclonal / chemistry
  • Antibodies, Monoclonal / metabolism
  • Biosensing Techniques / methods*
  • Humans
  • Lectins
  • Microchip Analytical Procedures
  • Protein Binding
  • Protein Interaction Mapping / methods*
  • Proteins / chemistry
  • Proteins / metabolism*
  • Spectrometry, Mass, Electrospray Ionization / methods*
  • Tyrosine / analogs & derivatives
  • Tyrosine / chemistry
  • Tyrosine / metabolism


  • Antibodies, Immobilized
  • Antibodies, Monoclonal
  • Lectins
  • Proteins
  • 3-nitrotyrosine
  • Tyrosine