How to make big molecules fly out of liquid water: applications, features and physics of laser assisted liquid phase dispersion mass spectrometry
How to make big molecules fly out of liquid water: applications, features and physics of laser assisted liquid phase dispersion mass spectrometry
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DOI：
10.1039/b615114k
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发表时间：
2007-07-14
影响因子：
3.3
通讯作者：
Abel, Bernd
中科院分区：
文献类型：
--
作者：
Charvat, Ales;Abel, Bernd
激光辅助液相分散质谱的应用，特点和机制的细节突出和讨论。它在过去已被用于直接从液相中分离带电的分子聚集体，并采用灵敏的飞行时间质谱法测定其分子量。该MALDI（基质辅助激光解吸和电离）型方法中的液体基质由真空中直径为10 μ m的自由液丝（或自由液滴）组成，该自由液丝用聚焦红外激光脉冲激发，该聚焦红外激光脉冲被调谐以匹配接近2.8 μ m的本体水的OH-伸缩振动的吸收频率。由于这些特征，我们将该方法称为离子或离子聚集体的自由液体基质辅助激光分散（IR-FL-MALDI），尽管LILBID（“激光诱导液体束（珠）解吸和电离”）也已被提出作为该技术的描述性首字母缩写，并且可以替代地使用。低电荷状态的大分子加合物在气相中从溶液中分离，通过一个尚未充分表征的机制，该机制敏感地依赖于激光强度和波长，并在温和的液体到真空转移后，通过飞行时间（TOF）质谱（MS）分析聚集体。在本贡献中讨论了直接从液体溶液中分离和充电的生物分子的可能机制。最新的技术进展，如最大限度地减少样品消耗，高通量质谱分析的策略，以及液束MS与HPLC的耦合也将被强调。IR-FL-MALDI的一个有趣的特征是我们称之为线性响应，即，对于大量的生物分子系统以及离子，气相质量信号在许多数量级上对溶液浓度具有令人惊讶的线性。由于这些特征，该方法可以被视为真正的解决方案探测光谱，这使得优雅的生物动力学研究。给出了时间分辨IR-FL-MALDI-MS最近成功应用的几个实验。一个特别的亮点是定量检测溶液中的氧化态的可能性，这清楚地区分了本方法从其他既定的MS源概念。由于良好的基质耐受性，也可以定量监测复杂混合物中的蛋白质。
Applications, features, and mechanistic details of laser assisted liquid phase dispersion mass spectrometry are highlighted and discussed. It has been used in the past to directly isolate charged molecular aggregates from the liquid phase and to determine their molecular weight employing sensitive time-of-flight mass spectrometry. The liquid matrix in this MALDI (matrix assisted laser desorption and ionization) type approach consists of a 10 mu m diameter free liquid filament in vacuum (or a free droplet) which is excited with a focused infrared laser pulse tuned to match the absorption frequency of the OH-stretch vibration of bulk water near 2.8 mu m. Due to these features we will refer to the approach as free liquid matrix assisted laser dispersion of ions or ionic aggregates (IR-FL-MALDI), although also LILBID ("laser induced liquid beam (bead) desorption and ionization") has been proposed early as a descriptive acronym for the technique and may be used alternatively. Low-charge-state macromolecular adducts are isolated in the gas phase from solution via a yet poorly characterized mechanism which sensitively depends upon the laser intensity and wavelength, and after the gentle liquid-to-vacuum transfer the aggregates are analyzed via time-of-flight (TOF) mass spectrometry (MS). Possible mechanisms for the isolation and charging of biomolecules directly from liquid solution are discussed in the present contribution. Recent technical advances such as minimizing the sample consumption, strategies for high throughput mass spectrometry, and coupling of liquid beam MS with HPLC will be highlighted as well. An interesting feature of IR-FL-MALDI is what we call the linear response, i.e., a surprising linearity of the gas phase mass signal on the solution concentration over many orders of magnitude for a large number of biomolecular systems as well as ions. Due to these features the approach may be regarded as a true solution probing spectroscopy, which enables elegant biokinetic studies. Several experiments in which time resolved IR-FL-MALDI-MS has recently been employed successfully are given. A particular highlight is the possibility to quantitatively detect oxidation states in solution, which clearly distinguishes the present approach from other established MS source concepts. Due to the good matrix tolerance also proteins in complex mixtures can be monitored quantitatively.