Method for enhancing peptide signal in time-of-flight secondary ion mass spectrometry

This paper presents a new method for enhancing peptide signals in time-of-flight secondary ion mass spectrometry (TOF-SIMS). The modification of peptide with 2-nitro-5-thiocyanobenzoic acid (NTCB) achieves high sensitivity for TOF-SIMS detection. Peptides containing only one cysteine at the N-terminus were used as model samples in order to evaluate the ionization efficiency of the NTCB-modified peptides, because peptides with internal cysteine residues give multiple digestion fragments. For the quantitative evaluation of ionization efficiency, an inkjet printing technique was also used to obtain reproducible samples. The TOF-SIMS signal intensity of the parent ion was increased by 20-fold through NTCB modification of a peptide with the amino acid sequence CKVASLRETYGDMAD. These results demonstrate the NTCB method has great potential for detecting the peptides by TOF-SIMS. (C) 2012 Elsevier B.V. All rights reserved.