Asanuma Miwako, Fukuzawa Seketsu, Matsuda Takayoshi, Hirota Hiroshi
RIKEN Genomic Sciences Center, Suehiro-cho, Tsurumi-ku, Yokohama 230-0045, Japan.
Rapid Commun Mass Spectrom. 2009 Jun;23(11):1647-53. doi: 10.1002/rcm.4051.
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.
十二烷基硫酸钠（SDS）是一种阴离子表面活性剂，广泛应用于肽和蛋白质样品制备。当通过基质辅助激光解吸/电离质谱（MALDI-MS）分析样品时，这种表面活性剂常常会导致信号抑制。我们之前报道了一种探针上样品制备方法，使用阴离子交换硅胶和芥子酸的悬浮液（即凝胶-SA悬浮液）作为基质，从而极大地提高了含有SDS的蛋白质溶液的MALDI信号检测。在本研究中，我们发现一定量的SDS增强了蛋白质样品的MALDI信号强度。当使用癸基硫酸钠和十四烷基硫酸钠代替SDS时也观察到了这种效果。此外，这种同时使用SDS和凝胶-SA悬浮液的探针上样品制备方法，与不使用SDS和凝胶-SA悬浮液的蛋白质样品相比，在MALDI-MS分析中蛋白质样品的检测限提高了约十倍。该方法不仅可应用于含有SDS的样品的MALDI-MS分析，还可应用于飞摩尔水平蛋白质或不溶性蛋白质（如膜蛋白）的检测。
