Wavelength dependence of soft infrared laser desorption and ionization
Wavelength dependence of soft infrared laser desorption and ionization
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DOI：
10.1021/jp063154v
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发表时间：
2007-01-25
影响因子：
3.7
通讯作者：
Murray, Kermit K.
中科院分区：
文献类型：
--
作者：
Little, Mark W.;Laboy, Jorge;Murray, Kermit K.
质子化的胰岛素分子通过在硅表面上的蛋白质薄膜的软IR激光解吸电离形成。飞行时间质谱记录在2.8和3.6 μ m之间的波长和电离的效率进行了比较的蛋白质薄膜的IR吸收。通过记录产生可检测离子信号所需的每单位面积的最小激光能量（阈值通量）来量化电离效率。电离效率跟踪胰岛素在2.6和3.8 μ m之间的OH、NH和CH伸缩吸收区的红外吸收光谱。最低的阈值能量密度和因此最有效的电离几乎与胰岛素在3.0 μ m附近的OH伸缩吸收一致。在电离效率的一个额外的局部最大值观察到在3.4 μ m，符合CH伸缩振动吸收。电离效率与IR吸收的比较表明蛋白质而不是残留溶剂吸收激光能量。扫描电子显微镜图像的牛胰岛素薄膜的硅激光照射后显示熔化和爆炸沸腾的迹象。电离通过牺牲吸收激光能量并充当内在基质的一些蛋白质分子而发生。
Protonated insulin molecules were formed by soft IR laser desorption ionization of a thin film of the protein on a silicon surface. Time-of-flight mass spectra were recorded at wavelengths between 2.8 and 3.6 mu m and the efficiency of ionization was compared to the IR absorption of the protein thin film. Ionization efficiency was quantified by recording the minimum laser energy per unit area required to produce a detectable ion signal (threshold fluence). The ionization efficiency tracks the IR absorption spectrum of insulin between 2.6 and 3.8,um in the region of OH, NH, and CH stretch absorption. The lowest threshold fluence and therefore the most efficient ionization was nearly coincident with the OH stretch absorption of insulin near 3.0 mu m. An additional local maximum in ionization efficiency was observed at 3.4 mu m, coincident with the CH stretch vibrational absorption. Comparison of the ionization efficiency with the IR absorption indicates that the protein and not the residual solvent is absorbing the laser energy. Scanning electron microscopy images of the bovine insulin thin films on silicon after laser irradiation show melting and indications of explosive boiling. Ionization occurs through the sacrifice of some of the protein molecules that absorb the laser energy and act as an intrinsic matrix.