MALDI-TOF MS with a Matrix of 3, 4-diaminobenzophenone for the Analysis of Phospholipids

Lipids and phospholipids are very important biomolecules except proteins, carbohydrates and nucleic acids[1]. Phospholipids have also been proved to be specific cancer biomarkers[2]. Therefore, there are increasing interests in lipid and phospholipids analysis. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has been shown previously to be an effective tool for the analysis of lipids, especially for the lipid composition of extracts of tissues and cells[3]. The new matrix 3, 4-diaminobenzophenone (DABP) is applied in the analysis of phospholipids by MALDI-TOF MS. The optimal composition of DABP matrix solution with methanol/water/hydrochloric acid (80:20:3,v/v/v) is used in the analysis of phospholipids. The most significant advantage of DABP matrix is that it suppresses the ion adducts of alkali metal, and thus showing single signal peak of phospholipids. This is very important for the analysis of the complex biological samples. In the analysis of practical samples, we do not need any matrix additives. With DABP as a matrix, intact phospholipid ion peaks can be readily produced with clean spectrum background, low laser energy, strong peak strength and high resolution. In addition, the sample preparation method is simple and time-saving. It should be concluded that different classes of phospholipids should be analyzed with different ion detection modes. Phosphatidylcholine (PC), lysophosphatidylcholine (LPC), and sphigomyelin (SM) should be analyzed under positive ion mode; and the acidic phospholipids such as phosphatidic acid (PA) and phosphatidylserine (PS) under negative ion mode.Though the signal suppression of different phospholipids species still exist, which need sample pretreatment methods such as HPLC, TLC to separate the class of lipids initially, the DABP as a matrix in lipid analysis has great potential