Search for: All records

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. However, vesicles typically suffer from highly limited transport across the membranes and an inability to mimic the dense membrane networks typically found in organelles such as the endoplasmic reticulum. Here, we describe programmable synthetic organelles based on highly stable nonlamellar sponge phase droplets that spontaneously assemble from a single-chain galactolipid and nonionic detergents. Due to their nanoporous structure, lipid sponge droplets readily exchange materials with the surrounding environment. In addition, the sponge phase contains a dense network of lipid bilayers and nanometric aqueous channels, which allows different classes of molecules to partition based on their size, polarity, and specific binding motifs. The sequestration of biologically relevant macromolecules can be programmed by the addition of suitably functionalized amphiphiles to the droplets. We demonstrate that droplets can harbor functional soluble and transmembrane proteins, allowing for the colocalization and concentration of enzymes and substrates to enhance reaction rates. Droplets protect bound proteins from proteases, and these interactions can be engineered to be reversible and optically controlled. Our results show that lipid sponge droplets permit the facile integration of membrane-rich environments and self-assembling spatial organization with biochemical reaction systems. 

Abstract Magnetic skyrmions exhibit unique, technologically relevant pseudo‐particle behaviors which arise from their topological protection, including well‐defined, 3D dynamic modes that occur at microwave frequencies. During dynamic excitation, spin waves are ejected into the interstitial regions between skyrmions, creating the magnetic equivalent of a turbulent sea. However, since the spin waves in these systems have a well‐defined length scale, and the skyrmions are on an ordered lattice, ordered structures from spin‐wave interference can precipitate from the chaos. This work uses small‐angle neutron scattering (SANS) to capture the dynamics in hybrid skyrmions and investigate the spin‐wave structure. Performing simultaneous ferromagnetic resonance and SANS, the diffraction pattern shows a large increase in low‐angle scattering intensity, which is present only in the resonance condition. This scattering pattern is best fit using a mass fractal model, which suggests the spin waves form a long‐range fractal network. The fractal structure is constructed of fundamental units with a size that encodes the spin‐wave emissions and are constrained by the skyrmion lattice. These results offer critical insights into the nanoscale dynamics of skyrmions, identify a new dynamic spin‐wave fractal structure, and demonstrate SANS as a unique tool to probe high‐speed dynamics. 

Abstract Cell membranes define the boundaries of life and primarily consist of phospholipids. Living organisms assemble phospholipids by enzymatically coupling two hydrophobic tails to a soluble polar head group. Previous studies have taken advantage of micellar assembly to couple single‐chain precursors, forming non‐canonical phospholipids. However, biomimetic nonenzymatic coupling of two alkyl tails to a polar head‐group remains challenging, likely due to the sluggish reaction kinetics of the initial coupling step. Here we demonstrate rapid de novo formation of biomimetic liposomes in water using dual oxime bond formation between two alkyl chains and a phosphocholine head group. Membranes can be generated from non‐amphiphilic, water‐soluble precursors at physiological conditions using micromolar concentrations of precursors. We demonstrate that functional membrane proteins can be reconstituted into synthetic oxime liposomes from bacterial extracts in the absence of detergent‐like molecules.