Electron capture dissociation for structural characterization of multiply charged protein cations
Electron capture dissociation for structural characterization of multiply charged protein cations
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DOI：
10.1021/ac990811p
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发表时间：
2000-02-01
影响因子：
7.4
通讯作者：
McLafferty, FW
中科院分区：
文献类型：
--
作者：
Zubarev, RA;Horn, DM;McLafferty, FW
对于< 20 kDa的蛋白质，这种新的自由基位点解离方法-比直接向偶电子离子添加能量的常规MS/MS方法（例如，碰撞活化解离，CAD）切割不同的和更多的骨架键。电子和离子之间的最小动能差使捕获最大化; 1 eV的差异使捕获减少10（3）。因此，在具有添加的电子捕获电极的FTMS离子单元中，捕获似乎在捕获电子和离子的势威尔斯之间的边界处实现得最好，现在提供80 +/-15%的前体离子转换效率。捕获截面取决于离子电荷的平方（z（2）），从而使较低电荷碎片离子的二次解离最小化。电子捕获被假定最初发生在质子化的网站，以释放一个充满活力的（类似于6 eV）H-。被捕获在高亲和性位点（如-S-S-或骨架酰胺）以引起非遍历（在能量随机化之前）解离的原子。蜂毒肽（2.8 kDa）和泛素（8.6 kDa）中每对氨基酸之间的切割在其ECD和CAD光谱中表示，为它们的从头测序提供完整的数据。因为翻译后修饰，如羧化，糖基化，硫酸化，在ECD中比在CAD中更不容易丢失，其序列位置的ECD分配更具体。
For proteins of < 20 kDa, this new radical site dissociation method-cleaves different and many more backbone bonds than the conventional MS/MS methods (e.g, collisionally activated dissociation, CAD) that add energy directly to the even-electron ions. A minimum kinetic energy difference between the electron and ion maximizes capture; a 1 eV difference reduces capture by 10(3). Thus, in an FTMS ion cell with added electron trapping electrodes, capture appears to be achieved best at the boundary between the potential wells that trap the electrons and ions, now providing 80 +/- 15% precursor ion conversion efficiency. Capture cross section is dependent on the ionic charge squared (z(2)), minimizing the secondary dissociation of lower charge fragment ions. Electron capture is postulated to occur initially at a protonated site to release an energetic (similar to 6 eV) H-. atom that is captured ata high-affinity site such as -S-S- or backbone amide to cause nonergodic (before energy randomization) dissociation. Cleavages between every pair of amino acids in mellitin (2.8 kDa) and ubiquitin (8.6 kDa) are represented in their ECD and CAD spectra, providing complete data for their de novo sequencing. Because posttranslational modifications-such as carboxylation, glycosylation, and sulfation are less easily lost in ECD than in CAD, ECD assignments of their sequence positions are far more specific.