基于离子液体基质的大豆中寡糖成分基质辅助激光解吸电离-质谱成像分析

将离子液体2,5-二羟基苯甲酸丁胺用于改进基质辅助激光解吸电离质谱分析寡糖的定量重复性,并进一步用于大豆和豆叶中寡糖的质谱成像研究.实验中设定正电荷检测模式、激光能量为70%,采用将离子液体2,5-二羟基苯甲酸丁胺甲醇溶液(20%,V/V)直接覆盖样品的简单加基质方法,分析寡糖样品及大豆和豆叶寡糖分布的质谱成像.结果表明,离子液体2,5-二羟基苯甲酸丁胺作为基质,用基质辅助激光解吸电离化质谱分析蔗糖、棉子糖、水苏糖3种寡糖样品,点内重复性RSD<3%,点间重复性RSD<4%,在0.062~1.00 mg/mL 范围内测定的线性相关系数R2≥ 0.996,显示出较好的定量分析潜力.将此基质用于基质辅助激光解吸电离质谱成像分析大豆切片和豆叶表面的二糖、三糖和四糖,得到空间分辨率为150 μm的3种寡糖质谱成像图.3种寡糖在大豆中大致均衡分布,在豆叶的分布均以叶尖为多,并且根据标准曲线和图中的信号强度可以估计其含量.

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

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.