Enhanced Ionization of Phosphatidylcholines during MALDI Mass Spectrometry Using DCTB as Matrix



Phosphatidylcholines (PCs) are the most abundant phospholipids constituents of the cellular membrane, which exhibit a variety of biological functions. The distinct critical roles in cellular function make their analysis quite demanding. Although MALDI-MS is one of the most powerful tools for biomolecules identification, it is still limited to phospholipids studies. The ionization of phosphatidylcholines is insufficient, and signals of PCs are frequently confused and suppressed by matrix clusters occurring in the same mass range. As an alternative matrix, T-2-(3-(4-t-butyl-phenyl)-2-methyl-2-propenylidene) malononitrile (DCTB) was introduced to overcome these problems in our study. Specifically, the signal intensity of phosphatidylcholines from soybean was enhanced more than several ten-folds using DCTB during positive ion MALDI-TOFMS. Peak overlaps caused by the wide distributions of series fatty acid residues from phospholipids were separated by introducing cesium cation. The occurred mass shift of 131.90 Da between [M+Cs]+ and [M+H]+ ("M" represents the molecular weight of the corresponding neutral hosphatidylcholine) was approved to be helpful in the assignments of ambiguous peaks of PCs from soybean. For real sample analysis, employing cesium chloride as an auxiliary reagent successfully facilitated the profiling and characterizing of PCs extracted from mouse lung and egg yolk followed by analysis with MALDI-TOFMS using DCTB as matrix.