Maldi mass spectrometry for the structural investigation of intact lipopolysaccharides

Lipopoligosaccharides (LPS) are powerful Gram-negative glycolipids that evade the immune system and invade host animal and vegetal cells. The structural elucidation of LPS is pivotal to understanding the mechanisms of infection at the molecular level. The structural nature of LOS has been the main obstacle for structural analysis by matrix-assisted laser desorption/ ionization (MALDI) mass spectrometry (MS). Recently1,2, we have published strategies able to obtain MALDI mass spectra of Lipooligosaccharides (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. Here, we'll show our preliminary results on MALDI MS of intact LPS. From these spectra (figure 1) it is possible to obtain the mw of the lipid a moiety, of the core oligosaccharides and of the o-chain repeating unit. (Figure 2) 1) L.Sturiale, A.Palmigiano, A.Silipo, Y.A.Knirel, A.Anisimov, R.Lanzetta, M.Parrilli, A.Molinaro, D.Garozzo Reflectron MALDI TOF and MALDI TOF/TOF mass spectrometry reveal novel structural details of native lipooligosaccharides Journal of Mass Spectrometry  46,  1135-1142 (2011 2) L.Sturiale, D.Garozzo, A.Silipo, R.Lanzetta, M.Parrilli, A.Molinaro New conditions for matrix-assisted laser desorption/ionization mass spectrometry of native bacterial R-type lipopolysaccharides Rapid Communications in Mass Spectrometry  19(13),  1829 (2005