FTMS Laboratory for Human Health Research, Department of Chemistry, North Carolina State University, Raleigh, North Carolina, USA.
Department of Statistics, North Carolina State University, Raleigh, North Carolina, USA.
J Mass Spectrom. 2024 Oct;59(10):e5091. doi: 10.1002/jms.5091.
Infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI) uses an infrared laser to desorb neutral biomolecules with postionization via ESI at atmospheric pressure. The Gaussian profile of the laser with conventional optics results in the heating of adjacent nonablated tissue due to the energy profile being circular. A diffractive optical element (DOE) was incorporated into the optical train to correct for this disadvantage. The DOE produces a top-hat beam profile and square ablation spots, which have uniform energy distributions. Although beneficial to mass spectrometry imaging (MSI), it is unknown how the DOE affects the ability to perform quantitative MSI (qMSI). In this work, we evaluate the performance of the DOE optical train against our conventional optics to define the potential advantages of the top-hat beam profile. Absolute quantification of glutathione (GSH) was achieved by normalizing the analyte of interest to homoglutathione (hGSH), spotting a dilution series of stable isotope labeled glutathione (SIL-GSH), and analyzing by IR-MALDESI MSI with either the conventional optical train or with the DOE incorporated. Statistical comparison indicates that there was no significant difference between the quantification of GSH by the two optical trains as evidenced by similar calibration curves. Results support that both optical trains can be used for qMSI without a change in the ability to carry out absolute quantification but providing the benefits of the top-hat optical train (i.e., flat energy profile and square ablation spots)-for future qMSI studies.
红外矩阵辅助激光解吸电喷雾电离（IR-MALDESI）使用红外激光解吸中性生物分子，然后通过大气压下的 ESI 进行后电离。传统光学的激光高斯轮廓导致相邻非烧蚀组织的加热，因为能量轮廓是圆形的。在光路中加入了一个衍射光学元件（DOE）来纠正这一缺点。DOE 产生了平顶光束轮廓和方形烧蚀斑点，具有均匀的能量分布。虽然这对质谱成像（MSI）有益，但尚不清楚 DOE 如何影响进行定量 MSI（qMSI）的能力。在这项工作中，我们评估了 DOE 光学系统相对于我们的传统光学系统的性能，以确定平顶光束轮廓的潜在优势。通过将感兴趣的分析物归一化为同型谷胱甘肽（hGSH），对稳定同位素标记谷胱甘肽（SIL-GSH）的稀释系列进行点样，并通过 IR-MALDESI MSI 进行分析，使用传统光学系统或结合 DOE 来实现谷胱甘肽（GSH）的绝对定量。统计比较表明，两种光学系统在 GSH 的定量方面没有显著差异，这表明校准曲线相似。结果支持两种光学系统都可用于 qMSI，而不会改变进行绝对定量的能力，但提供了平顶光学系统的优势（即，平坦的能量分布和方形烧蚀斑点），以供未来的 qMSI 研究使用。
