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 (beta(2)m), an important peripheral biological marker for renal dysfunction. Standard Ppm 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 ppm 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 beta(2)m, with little nonspecific binding. The results indicate that attomole amounts of beta(2)m can be captured from urine and detected reliably with SPR and MALDI-TOF MS analysis. (C) 2000 Elsevier Science B.V. All rights reserved.