MALDI-TOF MS Analysis of Lipid A

Lipid A extracted from whole cells using the microextraction method was subjected to MALDI-TOF MS analysis (25 (link)). In brief, 2,5-dihydroxybenzoic acid (DHB) matrix solution (10 mg/mL in 80% acetonitrile with 0.1% trifluoroacetic acid) was used for MS. Lipid A extract (2 μL) was mixed with matrix solution (2 μL) deposited on a plate for the vacuum-dried droplet method. The structural spectrum of lipid A was analyzed using the autoflex maX mass spectrometer (Bruker Daltonics, USA) in the negative-ion reflectron mode. The laser repetition rate was 2,000 Hz, and the resulting spectrum was accumulated with an average of 500 shots. The total analysis range of MALDI-TOF MS was m/z 400 to m/z 3,200, and lipid A mass analysis was performed at m/z 1,300 to m/z 2,300.