Microflex lrf maldi tof ms instrument

Dried lipid A samples were dissolved with 10 μL of chloroform. Then 1 μL of lipid A sample and 1 μL of 50 mg mL⁻¹ super-DHB (in 70% acetonitrile/water) (Sigma-Aldrich, St. Louis, MO, USA) were loaded onto a MSP 96 target polished steel MALDI plate and dried at room temperature. Lipid A samples were analyzed using Bruker Daltonics Microflex LRF MALDI-TOF MS instrument and FlexControl 3.0 software (Bruker, Bremen, Germany). Operating conditions were as follows: negative-ion and reflectron mode, detector gain = 6.9, laser frequency = 60.0 Hz, and laser power = 87%. MS/MS analysis of lipid A was performed using an Axima Resonance MALDI-quadrupole ion trap-TOF instrument (Shimadzu, Manchester, UK). Fragment ions were analyzed by collision-induced dissociation (CID) of parent ions and argon gas was used as a collision gas. Operating conditions were as follows: negative ion and reflectron mode, intro endcap = −5.5 kV, extr endcap = 10.0 kV, flight tube = 10.0 kV, reflectron center = −0.2 kV, reflectron back = −0.2 kV, detector = 2.2 kV, and laser intensity: 60–100 power. Data acquisition and processing were performed using Launchpad 2.9.3 software (Kratos Analytical, Manchester, UK).