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IRG 2 Highlights

DNA-tethered Membrane Formation From Giant Unilamellar Vesicles

boxer.jpg We have developed two strategies for preparing tethered lipid bilayer membrane patches on solid surfaces by DNA hybridization. In the first strategy, single-stranded DNA strands are immobilized by click chemistry to a silica surface, whose remaining surface is passivated to prevent direct assembly of a solid supported bilayer. Then giant unilamellar vesicles (GUVs) displaying the anti-sense strand based on a DNA-lipid conjugate are allowed to tether, spread, and rupture to form tethered bilayer patches. In the second strategy, a supported lipid bilayer displaying the DNA-lipid conjugate is first assembled on the surface. Then GUVs displaying the anti-sense strand are allowed to tether, spread and rupture to form tethered bilayer patches.

Polymer Dynamics in Concentrated Solution

Polymer Dynamics in Concentrated Solution The dynamics of entangled polymer solutions far from equilibrium is, at present, a subject of considerable interest because the “natural” modifications to tube or reptation-based theories have not been successful. In such systems, polymer molecules are highly entangled, which results in the motion of any given polymer being highly restricted due to interactions with its neighbors. As expected, the dynamics of such a complex fluid is far different from those of the same.

Chemical Imaging of Lipid Domains by High-Resolution Secondary Ion Mass Spectrometry (HR-SIMS)

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Marjorie Longo, UC Davis; Steve Boxer, Stanford University

Phase separated supported lipid bilayers were chemically imaged by HR-SIMS performed with the NanoSIMS 50 (Cameca Instruments). A focused Cs+ ion beam is rastered across the sample, extensively fragmenting the surface components. Secondary ions of up to 5 different masses are simultaneously detected and a lateral resolution of 50 nm can be achieved. In our experiments, a unique stable isotope was selectively incorporated into each membrane component, and the intensity and location of the isotopically enriched secondary ions were used to create a component-specific image of the phase separated lipid bilayer.

Label-Free Bioanalytical Detection Using Membrane-Coated Silica Nanoparticles

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Membrane-coated silica particles exhibit colloidal phase transitions that are governed by membrane surface interactions.

Collective phase behavior of the beads serves as a cooperative amplifier; a readily detectable response from small numbers of microscopic binding events between ligands and membrane-bound protein(s) of interest alters the structure of the colloidal dispersion in measurable ways.

Further statistical analysis of bead pair distribution functions enables quantitative determination of binding affinities.