title: Shotgun lipidomic analysis of human meibomian gland secretions with electrospray ionization tandem mass spectrometry.
abstract: OBJECTIVE
  The purpose of this investigation was to determine the major molecular components of the lipids in normal human meibomian gland secretions (meibum).
  
  
  METHODS
  The meibum samples were studied by direct infusion electrospray ionization (ESI), quadrupole time-of-flight mass spectrometry, and tandem mass spectrometry (MS/MS) analysis, in both positive and negative detection modes.
  
  
  RESULTS
  Hundreds of peaks were detected, among which the molecular compositions and subclasses of approximately 160 major peaks were confidently identified. The compositions and subclasses of these peaks were determined from collision-induced dissociation fragmentation patterns, high-resolution and high-mass-accuracy spectra, and references of literature reports. The major peaks detected in positive mode were those of nonpolar lipids, including wax esters, cholesteryl esters, triacylglycerols, and diesters, whereas in negative mode, the major peaks detected were those of polar lipids, including free fatty acids and (O-acyl)-ω-hydroxy fatty acids.
  
  
  CONCLUSIONS
  The analysis of intact lipids in meibum with direct infusion ESI-MS/MS analysis has the advantages of minimal sample preparation (no chromatography or pre-separation needed), mild experimental conditions, high throughput, and high sensitivity.
authors.affiliation: Applied Biotechnology Branch, Air Force Research Laboratory, Dayton, Ohio, USA.
authors.forename: Jianzhong
authors.initials: J
authors.lastname: Chen
authors.forename: Kari B
authors.initials: KB
authors.lastname: Green-Church
authors.forename: Kelly K
authors.initials: KK
authors.lastname: Nichols
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008055:Lipids / Q000032:analysis*; D008297:Male; D008537:Meibomian Glands / Q000737:chemistry* / Q000378:metabolism; D008875:Middle Aged; D012016:Reference Values; D021241:Spectrometry, Mass, Electrospray Ionization; D053719:Tandem Mass Spectrometry; D055815:Young Adult
chemical_list: D008055:Lipids