Lipid sponge droplets as programmable synthetic organelles.

Living cells segregate molecules and reactions in various subcellular compartments known as organelles. Spatial organization is likely essential for expanding the biochemical functions of synthetic reaction systems, including artificial cells. Many studies have attempted to mimic organelle functions using lamellar membrane-bound vesicles.

Single-Chain β-d-Glycopyranosylamides of Unsaturated Fatty Acids: Self-Assembly Properties and Applications to Artificial Cell Development.

Amphiphilic molecules undergo self-assembly in aqueous medium to yield various supramolecular structures depending on their chemical structure and molecular geometry. Among these, lamellar membrane-bound vesicles are of special interest due to their resemblance to cellular membranes. Here we describe the self-assembly of single-chain amide-linked amphiphiles derived from β-d-galactopyranosylamine and various unsaturated fatty acids into vesicles.

One-Dimensional Anomalous Diffusion of Gold Nanoparticles in a Polymer Melt.

We investigated the dynamics of polymer-grafted gold nanoparticles loaded into polymer melts using x-ray photon correlation spectroscopy. For low molecular weight host matrix polymer chains, normal isotropic diffusion of the gold nanoparticles is observed. For larger molecular weights, anomalous diffusion of the nanoparticles is observed that can be described by ballistic motion and generalized Lévy walks, similar to those often used to discuss the dynamics of jammed systems.

Highly Stable Artificial Cells from Galactopyranose-Derived Single-Chain Amphiphiles.

Single-chain amphiphiles (SCAs) that self-assemble into large vesicular structures are attractive components of synthetic cells because of the simplicity of bilayer formation and increased membrane permeability. However, SCAs commonly used for vesicle formation suffer from restricted working pH ranges, instability to divalent cations, and the inhibition of biocatalysts. Construction of more robust biocompatible membranes from SCAs would have significant benefits.

Interplay of electrostatics and lipid packing determines the binding of charged polymer coated nanoparticles to model membranes.

Understanding of nanoparticle-membrane interactions is useful for various applications of nanoparticles like drug delivery and imaging. Here we report on the studies of interaction between hydrophilic charged polymer coated semiconductor quantum dot nanoparticles with model lipid membranes. Atomic force microscopy and X-ray reflectivity measurements suggest that cationic nanoparticles bind and penetrate bilayers of zwitterionic lipids.

Measurements of the electric field of zero-point optical phonons in GaAs quantum wells support the Urbach rule for zero-temperature lifetime broadening.

We study a specific type of lifetime broadening resulting in the well-known exponential "Urbach tail" density of states within the energy gap of an insulator. After establishing the frequency and temperature dependence of the Urbach edge in GaAs quantum wells, we show that the broadening due to the zero-point optical phonons is the fundamental limit to the Urbach slope in high-quality samples. In rough analogy with Welton's heuristic interpretation of the Lamb shift, the zero-temperature contribution to the Urbach slope can be thought of as arising from the electric field of the zero-point longitudinal-optical phonons.