title: Quantitative analysis of total reflection X-ray fluorescence from finely layered structures using XeRay.
abstract: Total reflection x-ray fluorescence (TXRF) is a widely applicable experimental technique for studying chemical element distributions across finely layered structures at extremely high sensitivity. To promote and facilitate scientific discovery using TXRF, we developed a MATLAB-based software package with a graphical user interface, named XeRay, for quick, accurate, and intuitive data analysis. XeRay lets the user model any layered system, each layer with its independent chemical composition and thickness, and enables fine-tuned data fitting. The accuracy of XeRay has been tested in the analysis of TXRF data from both air/liquid interface and liquid/liquid interfacial studies and has been compared to literature results. In an air/liquid interface study, Ca2+sequestration was measured at a Langmuir monolayer of 1-stearoyl-2-oleoyl-sn-glycero-3-phosphatidic acid (SOPA) on a buffer solution of 1 mM CaCl2at pH 7.5. Data analysis with XeRay reveals that each 1 nm2of interfacial area contains 2.38 ± 0.06 Ca2+ions, which corresponds to a 1:1 ratio between SOPA headgroups and Ca2+ions, consistent with several earlier reports. For the liquid/liquid interface study of Sr2+enrichment at the dodecane/surfactant/water interface, analysis using XeRay gives a surface enrichment of Sr2+at 68-5+6Å2per ion, consistent with the result published for the same dataset.
authors.affiliation: James Franck Institute, The University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: Zhiliang
authors.initials: Z
authors.lastname: Gong
authors.affiliation: Program in the Biophysical Sciences, Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: Kerr
authors.affiliation: James Franck Institute, The University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: Hyeondo Luke
authors.initials: HL
authors.lastname: Hwang
authors.affiliation: James Franck Institute, The University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: J Michael
authors.initials: JM
authors.lastname: Henderson
authors.affiliation: The College, The University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: Tiffany
authors.initials: T
authors.lastname: Suwatthee
authors.affiliation: James Franck Institute, The University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: Benjamin R
authors.identifier: 0000000328137984
authors.initials: BR
authors.lastname: Slaw
authors.affiliation: James Franck Institute, The University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: Kathleen D
authors.initials: KD
authors.lastname: Cao
authors.affiliation: James Franck Institute, The University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: Binhua
authors.initials: B
authors.lastname: Lin
authors.affiliation: Center for Advanced Radiation Sources, The University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: Wei
authors.identifier: 0000000299963733
authors.initials: W
authors.lastname: Bu
authors.affiliation: James Franck Institute, The University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: Ka Yee C
authors.initials: KY
authors.lastname: Lee