Molecular Dynamics Simulations Reveal a Dielectric-Responsive Coronal Structure in Protein–Polymer Surfactant Hybrid Nanoconstructs

Solvent-free liquid proteins are a new class of thermally stable hybrid bionanomaterials that are produced by extensive lyophilization of aqueous solutions of protein–polymer surfactant nanoconjugates followed by thermal annealing. The hybrid constructs, which consist of a globular protein core surrounded by a monolayer of electrostatically coupled polymer surfactant molecules, exhibit nativelike structure, function, and backbone dynamics over a large temperature range. Despite the key importance of the polymer surfactant shell, very little is known about the atomistic structure of the corona and how it influences the phase behavior and properties of these novel nanoscale objects. Here we present molecular dynamics simulations of protein–polymer surfactant nanoconjugates consisting of globular cores of myoglobin or lysozyme and demonstrate that the derived structural parameters are highly consistent with experimental values. We show that the coronal layer structure is responsive to the dielectric constant of the medium and that the mobility of the polymer surfactant molecules is significantly hindered in the solvent-free state, providing a basis for the origins of retained protein dynamics in these novel biofluids. Taken together, our results suggest that the extension of molecular dynamics simulations to hybrid nanoscale objects could be of generic value in diverse areas of soft matter chemistry, bioinspired engineering, and biomolecular nanotechnology

Isolation of a Highly Reactive β‑Sheet-Rich Intermediate of Lysozyme in a Solvent-Free Liquid Phase

The thermal denaturation of solvent-free liquid lysozyme at temperatures in excess of 200 °C was studied by synchrotron radiation circular dichroism spectroscopy. Temperature-dependent changes in the secondary structure were used to map the equilibrium denaturation pathway and characterize a reactive β-sheet-rich unfolding intermediate that was stable in the solvent-free liquid phase under anhydrous conditions but which underwent irreversible aggregation in the presence of water. The unfolding intermediate had a transition temperature of 78 °C and was extremely stable to temperature, eventually reaching the fully denatured state at 178 °C. We propose that the three-stage denaturation pathway arises from the decreased stability of the native state due to the absence of any appreciable hydrophobic effect, along with an entropically derived stabilization of the reactive intermediate associated with molecular crowding in the solvent-free liquid

Self-Organization of Glucose Oxidase–Polymer Surfactant Nanoconstructs in Solvent-Free Soft Solids and Liquids

An anisotropic glucose oxidase–polymer surfactant nanoconjugate is synthesized and shown to exhibit complex temperature-dependent phase behavior in the solvent-free state. At close to room temperature, the nanoconjugate crystallizes as a mesolamellar soft solid with an expanded interlayer spacing of ca. 12 nm and interchain correlation lengths consistent with alkyl tail–tail and PEO–PEO ordering. The soft solid displays a birefringent spherulitic texture and melts at 40 °C to produce a solvent-free liquid protein without loss of enzyme secondary structure. The nanoconjugate melt exhibits a birefringent dendritic texture below the conformation transition temperature (<i>T</i>_c) of glucose oxidase (58 °C) and retains interchain PEO–PEO ordering. Our results indicate that the shape anisotropy of the protein–polymer surfactant globular building block plays a key role in directing mesolamellar formation in the solvent-free solid and suggests that the microstructure observed in the solvent-free liquid protein below <i>T</i>_c is associated with restrictions in the intramolecular motions of the protein core of the nanoconjugate

Gene-Mediated Chemical Communication in Synthetic Protocell Communities

A gene-directed chemical communication pathway between synthetic protocell signaling transmitters (lipid vesicles) and receivers (proteinosomes) was designed, built and tested using a bottom-up modular approach comprising small molecule transcriptional control, cell-free gene expression, porin-directed efflux, substrate signaling, and enzyme cascade-mediated processing

A Polymer Surfactant Corona Dynamically Replaces Water in Solvent-Free Protein Liquids and Ensures Macromolecular Flexibility and Activity

The observation of biological activity in solvent-free protein–polymer surfactant hybrids challenges the view of aqueous and nonaqueous solvents being unique promoters of protein dynamics linked to function. Here, we combine elastic incoherent neutron scattering and specific deuterium labeling to separately study protein and polymer motions in solvent-free hybrids. Myoglobin motions within the hybrid are found to closely resemble those of a hydrated protein, and motions of the polymer surfactant coating are similar to those of the hydration water, leading to the conclusion that the polymer surfactant coating plasticizes protein structures in a way similar to hydration water