Matching the laser wavelength to the absorption properties of matrices increases the ion yield in UV-MALDI mass spectrometry
Matching the laser wavelength to the absorption properties of matrices increases the ion yield in UV-MALDI mass spectrometry
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DOI：
10.1007/s00216-012-6478-5
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发表时间：
2013-09
影响因子：
4.3
通讯作者：
Marcel Wiegelmann;Jens Soltwisch;T. Jaskolla;K. Dreisewerd
中科院分区：
文献类型：
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作者：
Marcel Wiegelmann;Jens Soltwisch;T. Jaskolla;K. Dreisewerd
只有当激光波长对应于基质的高光学吸收时，才能在紫外基质辅助激光解吸电离质谱（MALDI-MS）中实现高分析灵敏度。激光能量密度和化合物的物理化学性质，例如，质子亲合性也显著影响分析灵敏度。结合起来，这些参数决定了每个激光脉冲喷射的材料量和离子产率，即，电离生物分子的部分。在这里，我们记录肽离子信号强度作为这些参数的函数。研究了三种肉桂酸基质：α-氰基-4-羟基肉桂酸、α-氰基-4-氯肉桂酸和α-氰基-2，4-二氟肉桂酸。此外，在比较实验中使用2，5-二羟基苯甲酸。离子信号强度“每次激光发射”和积分离子信号强度是在900个连续激光脉冲上获得的，所述激光脉冲施加在干液滴样品制备物上的不同位置上。对于激光波长，研究了337/355 nm的两个标准MALDI波长。此外，选择305或320 nm以解释卤代衍生物的蓝移吸收曲线。如果激光波长落在化合物的吸收曲线的峰值内，并且能量密度是相应离子检测阈值的两到三倍，则获得最大肽离子强度。结果表明，用于提高MALDI-MS中的分析灵敏度的方法，特别是对于MALDI-MS成像应用，其中每个照射像素可获得有限量的材料。
A high analytical sensitivity in ultraviolet matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) is only achieved if the laser wavelength corresponds to a high optical absorption of the matrix. Laser fluence and the physicochemical properties of the compounds, e.g., the proton affinity, also influence analytical sensitivity significantly. In combination, these parameters determine the amount of material ejected per laser pulse and the ion yield, i.e., the fraction of ionized biomolecules. Here, we recorded peptide ion signal intensities as a function of these parameters. Three cinnamic acid matrices were investigated: α-cyano-4-hydroxycinnamic acid, α-cyano-4-chlorocinnamic acid, and α-cyano-2,4-difluorocinnamic acid. In addition, 2,5-dihydroxybenzoic acid was used in comparison experiments. Ion signal intensities “per laser shot” and integrated ion signal intensities were acquired over 900 consecutive laser pulses applied on distinct positions on the dried-droplet sample preparations. With respect to laser wavelength, the two standard MALDI wavelengths of 337/355 nm were investigated. Also, 305 or 320 nm was selected to account for the blue-shifted absorption profiles of the halogenated derivatives. Maximal peptide ion intensities were obtained if the laser wavelength fell within the peak of the absorption profile of the compound and for fluences two to three times the corresponding ion detection threshold. The results indicate ways for improving the analytical sensitivity in MALDI-MS, and in particular for MALDI-MS imaging applications where a limited amount of material is available per irradiated pixel.