Analysis of peptide and protein samples containing surfactants by MALDI-MS

Protein samples containing ionic surfactants such as sodium dodecyl sulfate (SDS) can be analyzed by matrix-assisted laser desorption/ionization mass spectrometry, contrary to what is currently accepted, SDS at varying concentrations was added to four polypeptide samples, As expected, a decrease in the signal was observed for increasing concentrations of SDS up to 0.1% (w/v), at which no signal was observed for three of the analytes. However, a recovery of the signals of all the analytes was observed at concentrations of SDS above 0.3%, with useful spectra at concentrations as high as 10%. The SDS concentration at which signal recovery starts is always the same, regardless of the type and the concentration of the analyte. Another two surfactants 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS) and octylphenolpoly(ethylene glycol ether) 10 (Triton X-100) were also tested, The trend for signal variation with CHAPS addition is similar to that for SDS addition, but for Triton X-100, the signal always diminishes with increasing surfactant concentration, For protein samples containing surfactants with anionic groups, addition of more surfactant allows the acquisition of useful mass spectrometric data.