Label-Free Detection of Protein-Protein Interactions on Biochips

摘要

The recent introduction of protein microarrays is now providing tools for the global profiling of biochemical activities.[1] Snyder and co-workers, for example, used yeast protein chips to identify kinase substrates and lipid-binding proteins.[2] Labaer and co-workers reported self-assembling protein microarrays to map pairwise interactions among 29 human DNA replication proteins.[3] Any application of a protein chip must involve a suitable labeling strategy that will permit the observation of activities. Common strategies include the use of radioisotopes to follow phosphorylation reactions[4] and fluorescent tags to identify protein-protein interactions.[5] The use of labels has limitations, including the need for additional steps in an assay, the difficulty in detecting certain biochemical activities, and the inability to identify unanticipated activities. These limitations have motivated the development of label-free formats for identifying the full range of biochemical activities on protein chips. Herein, we demonstrate that MALDI-TOF MS can be used to identify protein-ligand and protein-protein interactions on biochips that are prepared from self-assembled monolayers (SAMs) on gold. This work is significant because it extends the capacity of the SAMDI (self-assembled monolayers for MALDI) method from observation of low-molecular-weight species to proteins that are 50 kDa in size.