Is the incorporation of analytes into matrix crystals a prerequisite for matrix-assisted laser desorption/ionization mass spectrometry?: A study of five positional isomers of dihydroxybenzoic acid
Is the incorporation of analytes into matrix crystals a prerequisite for matrix-assisted laser desorption/ionization mass spectrometry?: A study of five positional isomers of dihydroxybenzoic acid
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DOI：
10.1016/s1387-3806(98)14218-5
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发表时间：
1999-04-29
影响因子：
1.8
通讯作者：
Strupat, K
中科院分区：
文献类型：
--
作者：
Horneffer, V;Dreisewerd, K;Strupat, K
研究了二羟基苯甲酸(DHB)的2，4-，2，5-，2，6-，3，4-和3，5-位置异构体作为基质辅助激光解吸电离(MALDI)基质的作用。样品漫反射记录的固体基质样品的光学吸收光谱显示出峰展宽和峰相对于溶液光谱的红移。从溶液中生长了所有同分异构体的单晶，并用X射线结晶学对其进行了分析。用UV-(266,308,337,355 nm)和IR-(2.94µm)MALDI飞行时间质谱仪(MALDI-TOF-MS)分析了单晶以及添加了细胞色素c的标准干滴和薄层制剂，用分光光度法测量了重溶单晶在400 nm附近的血红素吸收，结果表明蛋白质定量地掺入了2，5-DHB的晶体中，部分蛋白质掺入了2，4-DHB的单晶中，并有较大的统计波动。对于其他异构体，没有发现蛋白质掺入超过10(-5)摩尔分析物与基质比率的检测下限。2，5-DHB的干液滴制剂在337和355 nm处以及2，4-DHB的266和308 nm处获得了标准制剂的最佳MALDI光谱，这两种基质在红外光谱中也表现良好。2，6-DHB在337 nm和2.94微米处产生了类似质量的光谱，但只有在丙酮溶液中制备的薄层中才能得到。结果表明，蛋白质掺入到固体MALDI基质的晶体中是有帮助的，但不是MALDI的先决条件。如果没有可测量的掺入，微晶薄层制剂的典型大表面积与体积比支持蛋白质解吸。在波长为308和266 nm处，所有DHB异构体都与蛋白质离子形成了不希望的基质加合物。(INT J质谱仪185/186/187(1999)859-870)(C)1999爱思唯尔科学公司
The 2,4-, 2,5-, 2,6-, 3,4-, and 3,5-positional isomers of dihydroxybenzoic (DHB) acid were investigated with respect to their function as matrix-assisted laser desorption/ionization (MALDI) matrices. Optical absorption spectra of solid matrix samples, recorded in diffuse reflection from samples revealed peak broadening and a red shift of the peaks relative to the solution spectra. Single crystals of all isomers were grown from solution and analyzed by x-ray crystallography. Single crystals, as well as standard dried droplet and thin layer preparations with added cytochrome c, were analyzed by UV- (266, 308, 337, 355 nm) and IR- (2.94 mu m) MALDI time-of-flight mass spectrometry (MALDI-TOF-MS), A spectrophotometric measurement of the heme absorption around 400 nm of redissolved single crystals showed a quantitative incorporation of the protein into crystals of 2,5-DHB and a partial protein incorporation with large statistical fluctuations into single crystals of 2,4-DHB. No protein incorporation above the detection limit of 10(-5) molar analyte-to-matrix ratio was found for the other isomers. Best MALDI spectra from standard preparations were recorded for dried droplet preparations of 2,5-DHB at 337 and 355 nm and for 2,4-DHB at 266 and 308 nm, Both matrices performed well in the IR, too. 2,6-DHB yielded spectra of comparable quality at 337 nm and 2.94 mu m, but only when prepared in a thin layer from an acetone solution. The results suggest that protein incorporation into the crystals of solid MALDI matrices is helpful, but not a prerequisite for MALDI. A large surface-to-volume ratio, typical for microcrystalline thin layer preparations supports protein desorption if no measurable incorporation occurs. Undesirable matrix adduct formation to the protein ions was seen for all DHB isomers at the wavelengths of 308 and 266 nm. (Int J Mass Spectrom 185/186/187 (1999) 859-870) (C) 1999 Elsevier Science B.V.