Matrix-assisted Laser Desorption/Ionizaiton-Mass Spectrometry Imaging of Oligosaccharides in Soybean and Leaf Using Ionic Liquid as Matrix / 分析化学

ABSTRACT

The ionic liquid butylamine 2,5-dihydroxybenzoate (DHB-BuN) was chosen as the matrix for improving repeatability of oligosaccharides quantitation, and imaging oligosaccharides in soybean and leaf by matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS).Using the ionic liquid matrix methanol solution (20%, V/V) to cover sample slice, and setting MS acquisition parameters including polarity as positive and laser power as 70%, the MS imaging experiment was performed to analyze oligosaccharides and their distribution in soyben and soybean leaf.As a result, the MALDI-MS analysis of 3 kinds of oligosaccharides including sucrose, raffinose and stachyose was performed using the ionic liquid matrix and the reproducibility RSDs were less than 3% for in-spot and less than 4% for spot-to-spot.The standard curves linear correlation coefficients (R2) were all no less than 0.996 between MS peak intensity and oligosaccharides concentraions in the concentration rage of 0.062-1.00 mg/mL, which showed quantitative power in MALDI-MS analysis.The matrix was used for MALDI-MS imaging analysis of soybean chips and soybean leaf surface disaccharide, trisaccharide and tetrasaccharide to obtain the soybean mass spectrum and spatial resolution of 150 μm of the three oligosaccharides imaging.Three kinds of oligosaccharides in the soybean roughly balanced distribution, and the oligosaccharides distribution in the leave was mostly at its tip part.The contents of the 3 kinds of oligosaccharides could be estimated by their MS peak intensity and above standard curve.The result suggested that the ionic liquid DHB-BuN matrix could be well applied in MALDI-MS imaging analysis of oligosaccharides in different sample.