The effect of sodium dodecyl sulfate and anion-exchange silica gel on matrix-assisted laser desorption/ionization mass spectrometric analysis of proteins

Sodium dodecyl sulfate (SDS), an anionic surfactant, is widely used in peptide and protein sample preparation. When the sample is analyzed by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), this surfactant can often cause signal suppression. We have previously reported an on-probe sample preparation method using a suspension of anion-exchange silica gel and sinapinic acid (i.e., gel-SA suspension) as a matrix, thereby greatly improving the MALDI signal detection of the protein solutions containing SDS. In this study, we found that a certain amount of SDS enhanced the MALDI signal intensity for protein samples. This effect was also observed when using sodium decyl sulfate and sodium tetradecyl sulfate instead of SDS. Furthermore, this on-probe sample preparation method using both SDS and the gel-SA suspension improved the detection limit of protein samples in the MALDI-MS analysis by about ten-fold as compared to that of protein samples without SDS and the gel-SA suspension. This method can be applied not only to the MALDI-MS analysis of samples containing SDS, but also to the examination of proteins at femtomole levels or insoluble proteins such as membrane proteins. Copyright (C) 2009 John Wiley & Sons, Ltd.