Fragmentation of leucine enkephalin as a function of laser fluence in a MALDI TOF-TOF.
Fragmentation of leucine enkephalin as a function of laser fluence in a MALDI TOF-TOF.
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MALDI TOF-TOF 中亮氨酸脑啡肽的碎片与激光注量的函数关系。
DOI：
10.1016/j.jasms.2006.11.008
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发表时间：
2007
影响因子：
3.2
通讯作者：
Yergey,AlfredL
中科院分区：
文献类型：
--
作者：
Campbell,JenniferM;Vestal,MarvinL;Blank,PaulS;Stein,StephenE;Epstein,JonathanA;Yergey,AlfredL
采用Nd-YAG激光和α-氰基氢化肉桂酸基质串联TOF质谱仪研究了激光辐照对MALDI中离子形成的影响。从离子形成阈值到最大可用激光能量，即约280-930 mJ/mm2，随激光能量的变化，研究了亮氨酸脑啡肽的电离和碎片化。最显著的发现是在影响值接近阈值时，出现了铵离子，其强度迅速增加，然后逐渐减小，出现了典型的骨架碎片离子。数据表明存在两种不同的离子形成环境。一种是与低激光通量下的分子解吸有关，导致大量的铵离子形成。第二种在较高的影响下占主导地位，最初与骨干型碎片有关，但在最高的影响下，发展为铵类碎片。第二种环境暗示了离子从表面烧蚀的大块物质中解吸。用阿伦尼乌斯速率定律来估计与这两个过程开始有关的温度。
The effects of laser fluence on ion formation in MALDI were studied using a tandem TOF mass spectrometer with a Nd-YAG laser andα-cyano hydrocinnamic acid matrix. Leucine enkephalin ionization and fragmentation were followed as a function of laser fluence ranging from the threshold of ion formation to the maximum available, that is, about 280–930 mJ/mm2. The most notable finding was the appearance of immonium ions at fluence values close to threshold, increasing rapidly and then tapering in intensity with the appearance of typical backbone fragment ions. The data suggest the presence of two distinct environments for ion formation. One is associated with molecular desorption at low values of laser fluence that leads to extensive immonium ion formation. The second becomes dominant at higher fluences, is associated initially with backbone type fragments, but, at the highest values of fluence, progresses to immonium fragments. This second environment is suggestive of ion desorption from large pieces of material ablated from the surface. Arrhenius rate law considerations were used to estimate temperatures associated with the onset of these two processes.