Surface Plasmon Resonance Mass Spectrometry as a Tool for Ligand Fishing: Proving the Efficiency of SPR-MS Applications

Abstract

The combination of surface plasmon resonance (SPR) and mass spectrometry (MS) has created a unique approach to protein investigations. SPR is used to quantify interactions between proteins and surface-immobilized ligands, and MS is used to determine the structural features of the bound proteins. 1,2 Proteins are affinity-captured and quantified from solution via ligands covalently attached to the SPR-sensor chip surface. Because SPR detection is non-destructive and non-labeling, proteins recovered from the SPR sensor chip surface can be further analyzed by MS. However, in SPR-MS experiments the selection of recovered solutions is very delicate, because the recovered solutions have to be both effective to elution and compatible to MS. In this study, we tried to find the best effective elution buffer among the several MS'compatible buffers. Moreover, we tried to figured out how many times a target protein has to be recovered to be detectable by MS, For our study, BFN and anti-IFN antibody were used. We immobilized anti-IFN antibody on SPR sensor chip surface (CM5, BIACORE AB, Sweden) by NHS/EDC for 7 min, flow rate was 5 /jdjnm. EFN was injected into the anti-IFN immobilized surface. We used 0.5% TFA, 10 mM NH4OH, 5% formic acid, 50 mM NaOH to recover the immobilized IFN. When recovering IFN, air bubbles were used ('sandwich' elution) to prevent the recovered IFN from being mixed with the running buffer (HBS-EP, pH 7.2) . 2 Adding up the amount of recovered IFN, we found out the lower limit of detectable concentration by MALDI-TOF. We expect that the identification of the MS-compatible and effective elution buffer help to reduce processing time. Furthermore, the SPR-MS tandem system is expected to become an powerful tool for high-throughput protein interaction discovery.