CNR Istituto per la Chimica e la Tecnologia dei Polimeri, Via P. Gaifami 18, 95126 Catania, Italy.
J Mass Spectrom. 2011 Nov;46(11):1135-42. doi: 10.1002/jms.2000.
Lipooligosaccharides (LOS) are powerful Gram-negative glycolipids that evade the immune system and invade host animal and vegetal cells. The structural elucidation of LOS is pivotal to understanding the mechanisms of infection at the molecular level. The amphiphilic nature of LOS has been the main obstacle for structural analysis by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS). Our approach has resolved this important issue and has permitted us to obtain reflectron MALDI mass spectra of LOS to reveal the fine chemical structure with minimal structural variations. The high-quality MALDI mass spectra show LOS species characteristic of molecular ions and defined fragments due to decay in the ion source. The in-source decay yields B-type ions, which correspond to core oligosaccharide(s), and Y-type ions, which are related to lipid A unit(s). MALDI tandem time-of-flight (TOF/TOF) MS of lipid A allowed for the elucidation of its structure directly from purified intact LOS without the need for any chemical manipulations. These findings constitute a significant advancement in the analysis of such an important biomolecule by MALDI MS.
脂寡糖（LOS）是一种强大的革兰氏阴性糖脂，能够逃避免疫系统并入侵宿主动物和植物细胞。LOS 的结构阐明对于在分子水平上理解感染机制至关重要。LOS 的两亲性一直是基质辅助激光解吸/电离（MALDI）质谱（MS）结构分析的主要障碍。我们的方法解决了这个重要问题，并使我们能够获得 LOS 的反射 MALDI 质谱，以揭示最小结构变化的精细化学结构。高质量的 MALDI 质谱显示 LOS 物种具有特征性的分子离子和由于在离子源中衰变而产生的定义片段。源内衰变产生 B 型离子，对应于核心寡糖（s），和 Y 型离子，与脂酰 A 单元（s）有关。脂质 A 的 MALDI 串联飞行时间（TOF/TOF）MS 允许直接从纯化的完整 LOS 中阐明其结构，而无需任何化学处理。这些发现构成了 MALDI MS 分析这种重要生物分子的重大进展。
