Infrared ion spectroscopy (IRIS) is a tandem mass spectrometry (MS) technique that generates structurally diagnostic vibrational spectra for mass-selected ions trapped in a mass spectrometer. Until now, IRIS applications for biological samples have primarily focused on solution-based analyses, such as body fluids (e.g., plasma and urine) and tissue homogenates, using electrospray ionization (ESI) coupled with liquid chromatography-mass spectrometry (LC-MS). In this study, we have combined matrix-assisted laser desorption/ionization (MALDI) with IRIS for the direct analysis of small molecules from biological tissues on a Fourier-transform ion cyclotron resonance mass spectrometer. We applied this technique alongside MALDI mass spectrometry imaging to analyse brain tissue from two knockout mouse models of l-lysine catabolism disorders: pyridoxine-dependent epilepsy (ALDH7A1) and glutaric aciduria type 1 (GCDH). The MALDI-IRIS platform, now available for users at HFML-FELIX, represents a significant advance in the direct structural characterization of metabolites in complex biological tissues and opens new possibilities for structure elucidation in the field of MALDI mass spectrometry imaging.

红外离子光谱（IRIS）是一种串联质谱技术，它为质量选择的被困在质谱仪中的离子生成具有结构诊断意义的振动光谱。迄今为止，IRIS对生物样本的应用主要集中在基于溶液的分析上，例如使用电喷雾电离（ESI）与液相色谱-质谱（LC-MS）结合的人体液体（如血浆和尿液）和组织匀浆。在这项研究中，我们结合了基质辅助激光解吸/电离（MALDI）与IRIS技术，在傅里叶变换离子回旋共振质谱仪上直接分析生物组织中的小分子。我们将该技术与MALDI质谱成像相结合，用于分析两种缺乏L-赖氨酸分解代谢的基因敲除小鼠模型的大脑组织：吡哆醇依赖性癫痫（ALDH7A1）和戊二酸尿症I型（GCDH）。现在可供HFML-FELIX用户使用的MALDI-IRIS平台在复杂生物组织中直接表征代谢物结构方面取得了重要进展，并为MALDI质谱成像领域的结构解析开辟了新的可能性。