Thrust 3 - Nanostructured Soft Materials and Nanoscale Analysis
The goal of Thrust 3 is active or passive control and characterization at the nanometer-scale.
Characterization methods in testing and development. In IRG2, we have a number of characterization methods in testing and development. With nano-scale secondary ion mass spectrometry (NanoSIMS), Boxer and Longo are capable of direct detection of composition with resolution at the nanometer-scale. Fluorescence interference microscopy used by Groves and Boxer is a real-time technique giving nanometer scale vertical resolution. For example, Groves can observe a snapshot of nanometer-scale fluctuations in a kind of supported lipid bilayer. By fluorescence correlation spectroscopy (FCS), Groves detects populations of molecules with different diffusion coefficients. Longo is providing supported lipid bilayers whereby lipids in one leaflet are in an ordered phase with relatively low diffusion coefficient and lipids in the opposing leaflet are in a disordered phase. FCS has the capability to distinguish these two populations despite their being less than a nanometer from each other.
Quantitative compositional analysis with secondary ion mass spectrometry. In order to fully implement supported bilayers in device formats, it is highly desirable to have the ability to track membrane components and bound proteins without the use of bulky fluorescent probes. To this end, Boxer has successfully utilized high lateral resolution NanoSIMS to image isotopically labeled components in bilayers that have been freeze dried. Longo has developed a phase- separated supported lipid bilayer composition that Boxer has used successfully as a test system for composition analysis on the 50 nm length scale as shown in Figure 2. A short-term goal is to use this system to track cholesterol in a ternary bilayer system. In addition, we will determine if uncharged components such as cholesterol and/or sphingomyelin reorganize in concert with charged components they are believed to interact with.
