Pittenauer Ernst, Allmaier Günter
Institute of Chemical Technologies and Analytics, Vienna University of Technology, Vienna, Austria.
Comb Chem High Throughput Screen. 2009 Feb;12(2):137-55. doi: 10.2174/138620709787315436.
MALDI in combination with high-energy collision-induced dissociation (CID) performed by tandem time-of-flight mass spectrometry (TOF/RTOF) is a relatively new technology for the structural analysis of various classes of biomolecules as e.g., peptides, carbohydrates, glycoconjugate drugs and lipids. Fragmentation mechanisms for these classes of compounds as well as corresponding fragment ion nomenclatures based mainly on data from tandem magnetic sector mass spectrometers are summarized in this article. The major instrumental differences between the present commercially available TOF/RTOFs are compiled (e.g., ion gate, gas-collision cell, type of reflectron, etc.). Whereas peptides have been investigated by MALDI-TOF/RTOF and their CID spectra are well understood, other classes of compounds (e.g., carbohydrates or lipids) are far less well investigated. By comparing data from two different MALDI-TOF/RTOF-instruments, it becomes evident that as they are operated at rather different collision energies for CID (1 versus 20 keV) strong differences in corresponding CID spectra for the same analyte are observed, causing problems with library searches in databases as e.g., abundant peptide side-chain fragmentations mainly occurring in the 8 to 20 keV collision regime are not considered. In contrast, differences in CID spectra of carbohydrates among different TOF/RTOF instruments are less clear-cut, because the required collision energy is spread across a wide range. Especially, carbohydrate cross-ring cleavages require less collision energy in the keV-range than the corresponding peptide side-chain fragmentations. Some of these carbohydrate cross-ring fragmentations are even observed by very low energy CID (< 1 eV fragmentation amplitude). Similar observations can also be made for glycoconjugates (e.g., the drug tylosin A). The lipid class triacylglycerol needs rather high collision energies for dissociating carbon-carbon bonds based upon classical charge-remote fragmentation mechanisms. Comparison of high-energy CID-data of ESI generated triacylglycerol precursors with CID spectra from MALDI generated precursors shows different mechanisms for charge-remote fragmentations. MALDI-TOF/RTOF-instruments operated in the elevated high-energy CID mode exhibit a strong potential in structural analysis of natural and synthetic biomolecules with information often not obtainable by low energy CID.
基质辅助激光解吸电离（MALDI）与由串联飞行时间质谱仪（TOF/RTOF）进行的高能碰撞诱导解离（CID）相结合，是一种用于各类生物分子结构分析的相对新技术，例如肽、碳水化合物、糖缀合物药物和脂质。本文总结了这些化合物类别的碎裂机制以及主要基于串联磁扇形质谱仪数据的相应碎片离子命名法。汇编了目前市售TOF/RTOF之间的主要仪器差异（例如，离子门、气体碰撞池、反射器类型等）。虽然肽已通过MALDI-TOF/RTOF进行了研究，其CID光谱也已得到很好的理解，但其他化合物类别（例如碳水化合物或脂质）的研究则少得多。通过比较来自两种不同MALDI-TOF/RTOF仪器的数据，可以明显看出，由于它们在CID的相当不同的碰撞能量下运行（1 keV对20 keV），对于相同的分析物，在相应的CID光谱中观察到了很大差异，这给数据库中的库搜索带来了问题，例如，主要发生在8至20 keV碰撞区域的丰富肽侧链碎裂未被考虑。相比之下，不同TOF/RTOF仪器之间碳水化合物的CID光谱差异不太明显，因为所需的碰撞能量分布在很宽的范围内。特别是，碳水化合物的跨环裂解在keV范围内所需的碰撞能量比相应的肽侧链碎裂要少。其中一些碳水化合物跨环碎裂甚至可以通过非常低能量的CID（<1 eV碎裂幅度）观察到。对于糖缀合物（例如药物泰乐菌素A）也可以进行类似的观察。基于经典的电荷远程碎裂机制，脂质类三酰甘油需要相当高的碰撞能量来解离碳-碳键。将电喷雾电离（ESI）产生的三酰甘油前体的高能CID数据与基质辅助激光解吸电离（MALDI）产生的前体的CID光谱进行比较，结果表明电荷远程碎裂的机制不同。在升高的高能CID模式下运行的MALDI-TOF/RTOF仪器在天然和合成生物分子的结构分析中具有强大的潜力，其信息通常无法通过低能量CID获得。
