title: Ganglioside influence on phospholipid films investigated with single molecule fluorescence measurements.
abstract: Single molecule fluorescence measurements are used to probe the effects of GM1 in DPPC monolayers. Langmuir-Blodgett films of GM1 and DPPC were doped with ~10(-8) mol % of the fluorescent lipid probe, BODIPY-PC, and transferred onto glass substrates at 23 mN/m. As shown previously, the individual orientation of each BODIPY-PC probe in the membrane can be measured using defocused polarized total internal reflection fluorescence microscopy, revealing changes in film properties at the molecular level. Here, BODIPY-PC tilt angle histograms are used to characterize the effects of GM1 in DPPC films from 0.05 to 100 mol % GM1. At high GM1 levels (>5 mol % GM1), trends in the single molecule measurements agree with previous bulk measurements showing the turnover from condensing to expanding influence of GM1 at 15-20 mol %, thus validating the single molecule approach. At biologically relevant, low concentrations of GM1 (<5 mol % GM1), where bulk fluorescence measurements are less informative, the single molecule measurements reveal a marked influence of GM1 on film properties. The addition of trace amounts of GM1 to DPPC films leads to an expansion of the film which continues to 0.10 mol % GM1, above which the trend reverses and the condensing effect previously noted is observed.
authors.affiliation: Ralph N. Adams Institute for Bioanalytical Chemistry, University of Kansas, 2030 Becker Drive, Lawrence, Kansas 66047, USA.
authors.forename: Kevin P
authors.initials: KP
authors.lastname: Armendariz
authors.forename: Robert C
authors.initials: RC
authors.lastname: Dunn
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000378:metabolism*; D001896:Boron Compounds / Q000032:analysis*; D005453:Fluorescence; D005456:Fluorescent Dyes / Q000032:analysis*; D005677:G(M1) Ganglioside / Q000378:metabolism*; D006575:Heterocyclic Compounds, 3-Ring / Q000032:analysis*
chemical_list: C560998:BODIPY-PC; D001896:Boron Compounds; D005456:Fluorescent Dyes; D006575:Heterocyclic Compounds, 3-Ring; D015060:1,2-Dipalmitoylphosphatidylcholine; D005677:G(M1) Ganglioside