This is a request for $140,753 towards the purchase of an electrospray ionization ion trap mass spectrometer (total cost: $201,076). This instrument will play a pivotal role in the research projects of many investigators at the Salk Institute and researchers at other academic institutions (see letters of support). These projects currently include (A) characterizing the primary structure of conotoxins;(B) identifying the role of phosphorylation in cell activation and cell growth and (C) characterizing the site protein ligand interactions.