Ion Yields in UV-MALDI Mass Spectrometry As a Function of Excitation Laser Wavelength and Optical and Physico-Chemical Properties of Classical and Halogen-Substituted MALDI Matrixes
Ion Yields in UV-MALDI Mass Spectrometry As a Function of Excitation Laser Wavelength and Optical and Physico-Chemical Properties of Classical and Halogen-Substituted MALDI Matrixes
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DOI：
10.1021/ac3008434
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发表时间：
2012-08-07
影响因子：
7.4
通讯作者：
Dreisewerd, Klaus
中科院分区：
文献类型：
--
作者：
Soltwisch, Jens;Jaskolla, Thorsten W.;Dreisewerd, Klaus
激光波长是紫外基质辅助激光解吸电离质谱法（UV-MALDI-MS）的关键参数。最佳的分析结果只有在激光波长对应于一个高的光学吸收的矩阵。在本工作中，研究了波长依赖性和基质质子亲和对MALDI过程的贡献。可调谐染料激光器用于检测280 ~ 355nm的波长范围。作为这些辐照参数的函数记录的肽和基质离子信号以热图的形式显示，这是一种提供多维数据解释的数据表示。研究了质子亲和范围为809 ~ 866 kJ/mol的基体。其中包括标准基质2、s -二羟基苯甲酸（DHB）和α -氰基-4-羟基肉桂酸（HCCA），以及五种卤素取代的肉桂酸衍生物，包括最近推出的4-氯- α -氰基-2,4-二氟肉桂酸（DiFCCA）基质。除DHB外，在固态光吸收峰的红色一侧获得了最高的分析离子信号。从基质中产生的分子分析物离子信号在吸收峰的低波长侧一致观察到较强的下降。这种效应主要是由于分析物和基质离子破碎程度的增加。多重卤化矩阵的最佳使用需要将激发波长调整到低于标准MALDI激光器在355 （Nd:YAG）或337 nm （N-2激光器）发射的值。综合数据为UV-MALDI解吸/电离过程提供了新的见解，并指出了提高分析灵敏度的方法。
The laser wavelength constitutes a key parameter in ultraviolet-matrix-assisted laser desorption ionization-mass spectrometry (UV-MALDI-MS). Optimal analytical results are only achieved at laser wavelengths that correspond to a high optical absorption of the matrix. In the presented work, the wavelength dependence and the contribution of matrix proton affinity to the MALDI process were investigated. A tunable dye laser was used to examine the wavelength range between 280 and 355 nm. The peptide and matrix ion signals recorded as a function of these irradiation parameters are displayed in the form of heat maps, a data representation that furnishes multidimensional data interpretation. Matrixes with a range of proton affinities from 809 to 866 kJ/mol were investigated. Among those selected are the standard matrixes 2,S-dihydroxybenzoic acid (DHB) and alpha-cyano-4-hydroxycinnamic acid (HCCA) as well as five halogen-substituted cinnamic acid derivatives, including the recently introduced 4-chloro-alpha-cyanocinnamic acid (CICCA) and alpha-cyano-2,4-difluorocinnamic acid (DiFCCA) matrixes. With the exception of DHB, the highest analyte ion signals were obtained toward the red side of the peak optical absorption in the solid state. A stronger decline of the molecular analyte ion signals generated from the matrixes was consistently observed at the low wavelength side of the peak absorption. This effect is mainly the result of increased fragmentation of both analyte and matrix ions. Optimal use of multiply halogenated matrixes requires adjustment of the excitation wavelength to values below that of the standard MALDI lasers emitting at 355 (Nd:YAG)or 337 nm (N-2 laser). The combined data provide new insights into the UV-MALDI desorption/ionization processes and indicate ways to improve the analytical sensitivity.