RATIONALE The molecular complexity of tissue features several signal-suppression effects which reduce the ionization of analytes significantly and thereby weakens the quality of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) imaging (MALDI imaging). We report a novel approach in MALDI imaging by reducing signal-suppression effects for the analysis of beta-amyloid (Aβ) plaques, one pathological hallmark of Alzheimer's disease (AD). METHODS We analyzed Aβ proteoforms from postmortem AD brains and brains from transgenic mice (APPPS1-21) overexpressing familial AD mutations by combining two techniques: (1) laser capture microdissection (LCM) to accumulate Aβ plaques and (2) phosphoric acid (PA) as additive to the super-2,5-dihydroxybenzoic acid matrix. RESULTS LCM and MALDI-MS enabled tandem mass spectrometric fragmentation of stained Aβ plaques. PA improved the signal-to-noise (S/N) ratio, especially of the Aβ1-42 peptide, by three-fold compared with the standard matrix additive trifluoroacetic acid. The beneficial effect of the PA matrix additive in MALDI imaging was particularly important for AD brain tissue. We identified several significant differences in Aβ plaque composition from AD compared with APPPS1-21, underlining the value of reducing signal-suppressing effects in MALDI imaging. CONCLUSIONS We present a novel strategy for overcoming signal-suppression effects in MALDI imaging of Aβ proteoforms.

中文翻译：

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在基质辅助激光解吸/电离质谱成像中减少信号抑制效果的双重策略。

理由组织的分子复杂性具有多种信号抑制作用，这些信号抑制作用可显着降低分析物的电离，从而削弱基质辅助激光解吸/电离（MALDI）质谱（MS）成像（MALDI成像）的质量。我们报告了一种通过减少信号抑制作用来分析β-淀粉样蛋白（Aβ）斑块（一种阿尔茨海默氏病（AD）的病理学特征）的MALDI成像中的新方法。方法我们结合两种技术分析了死后AD大脑和过表达家族性AD突变的转基因小鼠（APPPS1-21）的Aβ蛋白形式：（1）激光捕获显微切割（LCM）积累Aβ斑块和（2）磷酸（PA）作为超2,5-二羟基苯甲酸基质的添加剂。结果LCM和MALDI-MS使得串联的Aβ斑块质谱碎裂成为可能。与标准基质添加剂三氟乙酸相比，PA将信噪比（特别是Aβ1-42肽）的信噪比提高了三倍。PA基质添加剂在MALDI成像中的有益作用对于AD脑组织尤其重要。我们发现AD的Aβ斑块成分与APPPS1-21相比有几个显着差异，强调了在MALDI成像中降低信号抑制效应的价值。结论我们提出了一种克服Aβ蛋白形式MALDI成像中信号抑制作用的新策略。PA基质添加剂在MALDI成像中的有益作用对于AD脑组织尤其重要。我们发现AD的Aβ斑块成分与APPPS1-21相比有几个显着差异，强调了在MALDI成像中降低信号抑制作用的价值。结论我们提出了一种克服Aβ蛋白形式MALDI成像中信号抑制作用的新策略。PA基质添加剂在MALDI成像中的有益作用对于AD脑组织尤其重要。我们发现AD的Aβ斑块成分与APPPS1-21相比有几个显着差异，强调了在MALDI成像中降低信号抑制作用的价值。结论我们提出了一种克服Aβ蛋白形式MALDI成像中信号抑制作用的新策略。