Suppression of Matrix Clusters and Enhancement of Peptide Signals in MALDI-TOF Mass Spectrometry Using Nitrilotriacetic Acid

Matrix clusters and their alkali metal ion adducts suppress peptide signals in the 500-1400 Da range and compromise MALDI-TOF mass spectrometric peptide mass fingerprinting and protein identification. Addition of 7 mM nitrilotriacetic acid to the matrix solution significantly reduced matrix clusters and increased signal-to-noise ratio of peptide signals ~5 to 20-fold. As a result, reliability in the identification of femtomole amounts of proteins based on peptide mass fingerprinting and database search was significantly enhanced, leading to a higher score and sequence coverage.