Reactivity of Bioinspired Magnesium-Organic Networks under CO2 and O2 Exposure.

Photosynthesis is the model system for energy conversion. It uses CO2 as a starting reactant to convert solar energy into chemical energy, i.e., organic molecules or biomass. The first and rate-determining step of this cycle is the immobilization and activation of CO2, catalyzed by RuBisCO enzyme, the most abundant protein on earth. Here, we propose a strategy to develop novel biomimetic two-dimensional (2D) nanostructures for CO2 adsorption at room temperature by reductionist mimicking of the Mg-carboxylate RuBisCO active site. We present a method to synthesize a 2D surface-supported system based on Mg2+ centers stabilized by a carboxylate environment and track their structural dynamics and reactivity under either CO2 or O2 exposure at room temperature. The CO2 molecules adsorb temporarily on the Mg2+ centers, producing a charge imbalance that catalyzes a phase transition into a different configuration, whereas O2 adsorbs on the Mg2+ center, giving rise to a distortion in the metal-organic bonds that eventually leads to the collapse of the structure. The combination of bioinspired synthesis and surface reactivity studies demonstrated here for Mg-based 2D ionic networks holds promise for the development of new catalysts that can work at room temperature.

Catalyst Proximity-Induced Functionalization of h-BN with Quat Derivatives.

Inert single-layer boron nitride (h-BN) grown on a catalytic metal may be functionalized with quaternary ammonium compounds (quats) that are widely used as nonreactive electrolytes. We observe that the quat treatment, which facilitates the electrochemical transfer of two-dimensional materials, involves a decomposition of quat ions and leads to covalently bound quat derivatives on top of the 2D layer. Applying tetraoctylammonium and h-BN on rhodium, the reaction product is top-alkylized h-BN as identified with high-resolution X-ray photoelectron spectroscopy. The alkyl chains are homogeneously distributed across the surface, and the properties thereof are well-tunable by the choice of different quats. The functionalization further weakens the 2D material-substrate interaction and promotes easy transfer. Therefore, the functionalization scheme that is presented enables the design of 2D materials with tailored properties and with the freedom to position and orient them as required. The mechanism of this functionalization route is investigated with density functional theory calculations, and we identify the proximity of the catalytic metal substrate to alter the chemical reactivity of otherwise inert h-BN layers.

Contrasting Chemistry of Block Copolymer Films Controls the Dynamics of Protein Self-Assembly at the Nanoscale.

Biological systems are able to control the assembly and positioning of proteins with nanoscale precision, as exemplified by the intricate molecular structures within cell membranes, virus capsids, and collagen matrices. Controlling the assembly of biomolecules is critical for the use of biomaterials in artificial systems such as antibacterial coatings, engineered tissue samples, and implanted medical devices. Furthermore, understanding the dynamics of protein assembly on heterogeneous templates will ultimately enable the control of protein crystallization in general. Here, we show a biomimetic, hierarchical bottom-up approach to direct the self-assembly of crystalline S-layers through nonspecific interactions with nanostructured block copolymer (BCP) thin-film templates. A comparison between physically and chemically patterned BCP substrates shows that chemical heterogeneity is required to confine the adhesion and self-assembly of S-layers to specific BCP domains. Furthermore, we show that this mechanism can be extended to direct the formation of collagen fibers along the principal direction of the underlying BCP substrate. The dynamics of protein self-assembly at the solid-liquid interface are followed using in situ high-resolution atomic force microscopy under continuous flow conditions, allowing the determination of the rate constants of the self-assembly. A pattern of alternating, chemically distinct nanoscale domains drastically increases the rate of self-assembly compared to non-patterned chemically homogeneous substrates.

Dynamically resolved self-assembly of S-layer proteins on solid surfaces.

By using high-speed and high-resolution Atomic Force Microscopy (AFM), it was possible to resolve within a single experiment the kinetic pathway in S-layer self-assembly at the solid-liquid interface, obtaining a model that accounts for the nucleation, growth and structural rearrangements in 2D protein self assembly across time (second to hours) and spatial scales (nm to microns).