Desorption electrospray ionisation mass spectrometry imaging (DESI-MSI) is typically known for the ionisation of small molecules such as lipids and metabolites, in singly charged form. Here we present a method that allows the direct detection of proteins and peptides in multiply charged forms directly from tissue sections by DESI. Utilising a heated mass spectrometer inlet capillary, combined with ion mobility separation (IMS), the conditions with regard to solvent composition, nebulising gas flow, and solvent flow rate have been explored and optimised. Without the use of ion mobility separation prior to mass spectrometry analysis, only the most abundant charge series were observed. In addition to the dominant haemoglobin subunit(s) related trend line in the m/z vs drift time (DT) 2D plot, trend lines were found relating to background solvent peaks, residual lipids and, more importantly, small proteins/large peptides of lower abundance. These small proteins/peptides were observed with charge states from 1+ to 12+, the majority of which could only be resolved from the background when using IMS. By extracting charge series from the 2D m/z vs DT plot, a number of proteins could be tentatively assigned by accurate mass. Tissue images were acquired with a pixel size of 150 μm showing a marked improvement in protein image resolution compared to other liquid-based ambient imaging techniques such as liquid extraction surface analysis (LESA) and continuous-flow liquid microjunction surface sampling probe (LMJ-SSP) imaging.

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解吸电喷雾电离质谱成像（DESI-MSI）通常已知用于单电荷形式的小分子（例如脂质和代谢物）的电离。在这里，我们提出了一种方法，可以直接通过DESI直接从组织切片中检测多电荷形式的蛋白质和多肽。利用加热的质谱仪入口毛细管，结合离子迁移分离（IMS），已探索和优化了有关溶剂组成，雾化气流和溶剂流速的条件。在质谱分析之前不使用离子迁移率分离，仅观察到最丰富的电荷系列。除了主要的血红蛋白亚基相关的趋势线（m / z）相对于漂移时间（DT）2D图，发现了与背景溶剂峰，残留脂质以及更重要的是较低丰度的小蛋白质/大肽有关的趋势线。观察到这些小的蛋白质/肽的电荷状态为1+到12+，其中大多数只能在使用IMS时从背景中分离出来。通过从2D m / z与DT图中提取电荷序列，可以通过精确质量初步分配许多蛋白质。与其他基于液体的环境成像技术（例如液体提取表面分析（LESA）和连续流动液体微结表面采样探针（LMJ-SSP））相比，以150μm的像素大小采集的组织图像显示出蛋白质图像分辨率的显着改善。 ）成像。

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