CH. CH. 2. 3. SF Intensity (arb). d (nm). Dominant Periodicity = 246 nm Minor Periodicities = 276 nm, 2.252 m m.
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SF Intensity (arb)
Dominant Periodicity = 246 nm
Minor Periodicities = 276 nm, 2.252 mm
Model Cellular Membrane for the Study of Non-Classical Protein Transport Sarah M. Sterling1,2, Lei Li3, Joerg Fick1, Michael D. Mason1,2,4, Igor Prudovsky2,4,5, David J. Neivandt1,2,41Department of Chemical and Biological Engineering, University of Maine, Orono, ME 044692Graduate School of Biomedical Sciences, University of Maine, Orono, ME 04469 3Department of Physics and Astronomy, University of Maine, Orono, ME 044694Institute for Molecular Biophysics, Orono, ME 044695Maine Medical Center Research Institute, Scarborough, ME 04074
Due to the correlation between membrane structure and function, a great deal of work is focused on determining the distribution, kinetics, and structure of lipid and protein membrane constituents, often as a result of their interactions. One such interaction is the non-classical export of signal peptide-less proteins (SPLs). This small subset of proteins does not utilize the Endoplasmic Reticulum (ER)-Golgi pathway of release, yet the proteins still play roles in cell survival, cell growth, and angiogenesis. Combining spectroscopic and microscopic techniques allows for a better understanding of this unknown mechanism. Development of a planar model membrane system replicating in a controlled manner, the cross-section of a biological membrane has been necessary in order to enable application of many of these techniques.
Sum Frequency Generation (SFS)
A sum frequency signal is produced by overlapping two pulsed laser beams temporally and spatially at an interface. One beam is at a fixed visible frequency while the other is a tunable frequency infrared (IR) beam. Photons are emitted at the sum of the two frequencies. Detecting these photons as a function of the IR wavelength produces a vibrational spectrum of interfacial molecules from which the following information may be obtained:
Polar Orientationspectralpeaks or dips
Molecular Conformationresonances in the spectrum
Interference Effect in SFS Spectra
Due to the hydrogel spacing layer between the lipid bilayer and the gold surface, an optical interference effect occurs which requires calibration:
Schematic representation of the model membrane system comprising a lipid bilayer supported on a hydrogel spacing layer attached to a gold coated substrate.
Schematic representation of LB/LS deposition.
Currently, fluorescence correlation spectroscopy is being used to determine lipid membrane diffusion coefficients, verifying the phase transition temperature. Shown here are preliminary results.
Acknowledgements: The Institute for Molecular Biophysics, the Pulp and Paper Foundation of the University of Maine, the University of Maine Graduate School of Biomedical Sciences, and the National Science Foundation – Major Research Instrumentation CHE-0722759 grant for Financial Assistance