The Application Of Ionic Liquid And Graphene Matrix For MALDI-MS Imaging Analysis Of Small Molecular Components In Mulberry Leaves And Soybeans

In recent years,matrix-assisted laser desorption ionization-mass spectrometry?MALDI-MS?,has gained wide attention and has gained great development momentum.This technique facilitates direct multicomponent analysis of biopsies at the molecular level,The distribution of target components in different tissues can be obtained by image reconstruction software to provide the localization,qualitative and quantitative information of component distributed in tissue samples.Substrate selection and coverage method are very important for the successful application of this technique.This research adopts FT-ICR-MS to find a solution for the problems of uneven matrix distribution and poor quantitative repeatability in MALDI-MS Imaging using proper substrate selection and coverage method.?1?This experiment combined ionic liquid matrix and DHB/DMA with ultrasonic spray matrix coverage method,and used MALDI-MS to analyze the spatial distribution of small molecular components such as Protocatechuic acid,Chlorogenic acid,monosaccharide and disaccharide,Astragalin,rutin,Isoquercetin,Cyanidin-3-O-glucoside,Quercetin-3-O-6”-O-acety-l-?-D-glucopyranoside,Kaempferol-3-O-rutinoside in the surface and veins of mulberry leave.By comparing three different matrix coverage methods,namely,dry drop method,airbrush method and ultrasonic spray method,it shows that ultrasonic spray coverage method has better reproducibility and sensitivity,and is not inclined to cause the diffusion of the components to be tested.On the basis of investigating the effect of experimental conditions on signal-to-noise ratio,KBr,the additive with a concentration of 15mmol/L,laser energy 70%and ultrasonic spray repeated spraying for 12 times were selected as MALDI-MS Imaging parameters to analyze the distribution of different small molecular components on mulberry leaf surface and vein slices.Images showed that monosaccharides and disaccharides are mainly distributed in the vein of mulberry leaves,and the content of Protocatechuic acid is higher in the vein and also distributed on the surface of mulberry leaves.OthercomponentssuchasChlorogenicacid,Cyanidin-3-O-glucoside,Quercetin-3-O-6”-O-acetyl-?-D-glucopyranoside are distributed on mulberry leaf surface and vein slices.Astragalin,Isoquercetin,rutin and Kaempferol-3-O-rutinoside are more likely to be distributed on the surface of mulberry leaves near the veins,however,no rutin is found in the longitudinal section imaging of the inner veins.Experiments show that the method based on ionic liquid matrix and ultrasonic spray matrix coverage can be well applied to MALDI-MS Imaging analysis of small and medium molecular components in traditional Chinese medicine and plants.?2?Use few-layer-graphene?FLG?as matrix of MALDI-MS Imaging to analyze small molecular components in soybean.Images have visualized the spatial distribution of bioactive compounds detected in soybean.FLG matrix was deposited on the sample section by airbrush method,and the effects of laser energy,spray times of airbrush spraying and the effects that additives KBr and KNO₃ have on the signal-to-noise ratio of the component mass spectra peak were studied,under the selected experimental conditions,the FLG matrix showed good reproducibility and sensitivity.Use MALDI-MS Imaging to analyze the distribution of disaccharides,trisaccharides,tetrasaccharides,triglycerides and a small amount of phospholipid in the slices of mature soybean and immature soybean.The imaging results show that the phospholipids are evenly distributed in the slices of mature soybean and immature soybean,and there is no significant difference in its distribution between the slices of mature soybean and immature soybean,oligosaccharides and triglycerides are distributed evenly in mature soybean slices,but differences are shown in its distribution in immature soybean radicle and cotyledon,the components of oligosaccharides are mainly distributed in the radicle of immature soybean slices,LnLLn is mainly distributed in cotyledon edges and radicle parts of the immature soybean slices,SSO and BLO are mainly distributed in the middle of immature soybean slices.The results of this experiment show that the FLG matrix is suitable for MALDI-MS Imaging analysis of lipid and saccharide components in plants.