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2009 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.

Green Chemistry of Poly(l-lactides)

As part of a series of studies on the green chemistry of poly(l-lactides), we have performed a theoretical study of the mechanism of ring-opening polymerization. We have investigated two alternative mechanisms for the ring-opening polymerization of l-lactide using a guanidine-based catalyst, the first involving acetyl transfer to the catalyst, and the second involving only hydrogen bonding to the catalyst. Using computational chemistry methods, we show that the hydrogen bonding pathway shown above is preferred over the acetyl transfer pathway and that this is consistent with experimental information.

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.

Flow-Enhanced Vesicle Deformation in the Four-roll Mill

Susan Muller, Dept. Chemical Engineering, UC Berkeley
This project leverages ongoing research on the dynamics of DNA and vescicles within CPIMA.  We have developed a novel microfluidic four-roll mill that allows all flow types (from extension to shear to rotation) to be accessed and have previously used it to examine DNA tumbling in mixed flows and, […]