Quantitative analysis of PE and PS was carried out using a Waters
Premier XE triple quadrupole mass spectrometer interfaced with an Acquity
ultra-high performance liquid chromatography (UPLC) system (Waters, Milford,
MA). Mass spectrometer was operated in electrospray ionization mode with
negative ion acquisition. Phospholipids were extracted from cells by the
Folch procedure with initial addition of internal standards,
D31-160/181 PE and D31-160/181 PS. Quantification was
based on calibration curves constructed using PE and PS standards with
multiple reactions monitoring function. PE calibration curves include 160
LPE, 181 LPE, 160/181 PE, 160,182 PE, 180,182 PE, 180/204 ES. PE and PS
species without reference compounds were quantified with the standard
sharing the closest structure. PS calibration curves include 160 LPS, 181
LPS, 180 LPS, 160/181 PS, 160,182 PS, 180,182 PS, 180/204 PS. Final
concentration of PE and PS were normalized to DNA contents in the cell and
expressed as ng/mg DNA.
Premier XE triple quadrupole mass spectrometer interfaced with an Acquity
ultra-high performance liquid chromatography (UPLC) system (Waters, Milford,
MA). Mass spectrometer was operated in electrospray ionization mode with
negative ion acquisition. Phospholipids were extracted from cells by the
Folch procedure with initial addition of internal standards,
D31-160/181 PE and D31-160/181 PS. Quantification was
based on calibration curves constructed using PE and PS standards with
multiple reactions monitoring function. PE calibration curves include 160
LPE, 181 LPE, 160/181 PE, 160,182 PE, 180,182 PE, 180/204 ES. PE and PS
species without reference compounds were quantified with the standard
sharing the closest structure. PS calibration curves include 160 LPS, 181
LPS, 180 LPS, 160/181 PS, 160,182 PS, 180,182 PS, 180/204 PS. Final
concentration of PE and PS were normalized to DNA contents in the cell and
expressed as ng/mg DNA.