Determination of the collision cross sections of cardiolipins and phospholipids from Pseudomonas aeruginosa by traveling wave ion mobility spectrometry-mass spectrometry using a novel correction strategy

Collision cross section (CCS) values are descriptors of the 3D structure of ions which can be determined by ion mobility spectrometry (IMS). Currently, most lipidomic studies involving CCS value determination concern eukaryote samples (e.g. human, bovine) and to a lower extent prokaryote samples (e.g. bacteria). Here, we report CCS values obtained from traveling wave ion mobility spectrometry (TWCCSN2) measurements from the bacterial membrane of Pseudomonas aeruginosa—a bacterium ranked as priority 1 for the R&D of new antibiotics by the World Health Organization. In order to cover the lack of reference compounds which could cover the m/z and CCS ranges of the membrane lipids of P. aeruginosa, three calibrants (polyalanine, dextran and phospholipids) were used for the TWCCSN2 calibration. A shift from the published lipid CCS values was systematically observed (ΔCCS% up to 9%); thus, we proposed a CCS correction strategy. This correction strategy allowed a reduction in the shift (ΔCCS%) between our measurements and published values to less than 2%. This correction was then applied to determine the CCS values of Pseudomonas aeruginosa lipids which have not been published yet. As a result, 32 TWCCSN2 values for [M+H]+ ions and 24 TWCCSN2 values for [M−H]− ions were obtained for four classes of phospholipids (phosphatidylethanolamines (PE), phosphatidylcholines (PC), phosphatidylglycerols (PG) and diphosphatidylglycerols—known as cardiolipins (CL)).