Exploring the limit of detection in biomolecular interaction analysis mass spectrometry (BIA/MS): Detection of attomole amounts of native proteins present in complex biological mixtures

Biomolecular interaction analysis mass spectrometry (BIA/MS) offers a unique combination of two highly complementary analytical techniques: biological sensing via surface plasmon resonance and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), with application to both functional and structural studies of native proteins. Important to the propagation of BIA/MS is the ability to detect and work with low levels of proteins present in complex biological mixtures. In this work, the limit of detection in BIA/MS is explored utilizing beta-2-microglobulin (β₂m), an important peripheral biological marker for renal dysfunction. Standard β₂m solutions and diluted urine samples were analyzed in the surface plasmon resonance (SPR) biosensor and the binding responses measured as a function of sample concentration/dilution and flow rate through the biosensor. Following the SPR analysis of the β₂m solutions that gave the lowest reliable and reproducible SPR response, the sensor surfaces were subjected to MALDI-TOF MS, yielding spectra showing selective retrieval of β₂m, with little nonspecific binding. The results indicate that attomole amounts of β₂m can be captured from urine and detected reliably with SPR and MALDI-TOF MS analysis. (C) 2000 Elsevier Science B.V.