Mercaptobenzothiazoles: A new class of matrices for laser desorption ionization mass spectrometry

We report 2-mercaptobenzothiazole (MBT) and its analogs as a class of new matrices for matrix-assisted laser desorption mass spectrometry (MALDI-MS) at 337 nm. MBT has been used successfully for the desorption of proteins up to 100,000 u. A comparison with sinapinic acid and α-cyano-4-hydroxycinnamic acid indicates that MBT provides the same level of sensitivity and resolution, but offers the advantage of higher tolerance to sample contaminants such as ionic detergents. 5-Chloro-2-mercaptobenzothiazole (CMBT), an analog of MBT, has been found not only effective for the analysis of peptides, low-mass proteins, and glycolipids, but also superior to conventional matrices for the analysis of muropeptides and at least some oligosaccharides. CMBT also exhibits excellent experimental reproducibility of MALDI-MS results owing to the homogeneous crystallization of the analyte/matrix mixture over the entire sample surface area. Finally, all five mercaptobenzothiazoles studied in this work are shown to be well suited for synthetic polymer analysis.