title: Relative ion yields in mammalian cell components using C60SIMS.
abstract: Time of flight secondary ion mass spectrometry has been used to better understand the influence of molecular environment on the relative ion yields of membrane lipid molecules found in high abundance in a model mammalian cell line, RAW264.7. Control lipid mixtures were prepared to simulate lipid-lipid interactions in the inner and outer leaflet of cell membranes. Compared with its pure film, the molecular ion yields of 1,2-dioleoyl-sn-glycero-3-phosphocholine and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine are suppressed when mixed with 2-dipalmitoyl-sn-glycero-3-phosphocholine. In the mixture, proton competition between 1,2-dioleoyl-sn-glycero-3-phosphocholine, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine, and 2-dipalmitoyl-sn-glycero-3-phosphocholine led to lower ionization efficiency. The possible mechanism for ion suppression was also investigated with1H and13C nuclear magnetic resonance spectroscopy. The formation of a hydroxyl bond in lipid mixtures confirms the mechanism involving proton exchange with the surrounding environment. Similar effects were observed for lipid mixtures mimicking the composition of the inner leaflet of cell membranes. The secondary molecular ion yield of 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-L-serine was observed to be enhanced in the presence of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine.
authors.affiliation: Department of Chemistry, Pennsylvania State University, University Park, 16802, PA, USA.
authors.forename: Selda
authors.initials: S
authors.lastname: Keskin
authors.affiliation: Department of Chemistry, Pennsylvania State University, University Park, 16802, PA, USA.
authors.forename: Alan
authors.initials: A
authors.lastname: Piwowar
authors.affiliation: Department of Chemistry, Pennsylvania State University, University Park, 16802, PA, USA.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Hue
authors.affiliation: Department of Chemistry, Pennsylvania State University, University Park, 16802, PA, USA.
authors.forename: Kan
authors.initials: K
authors.lastname: Shen
authors.affiliation: Department of Chemistry, Pennsylvania State University, University Park, 16802, PA, USA.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Winograd
keywords: RAW264.7 cells; TOF-SIMS; lipids; matrix effects