Interplay of Depletion Forces and Biomolecular Recognition in the Hierarchical Assembly of Supramolecular Tubes.

Crowding effects have a profound impact on the hierarchical organization of cellular architectures. In the fields of systems chemistry and soft matter, this effect has not received much attention so far. Here, it is explored how poly(ethylene glycol) (PEG) as a crowding agent invokes depletion forces that act on synthetic supramolecular tubes. Hence, supramolecular tubes are pushed from their random orientation into hierarchically assembled bundles due to the PEG-induced crowded environment. The resulting morphology of formed bundled architectures can be tuned by the concentrations of both the supramolecular tubes and the PEG. The introduction of biotin groups at the surface of the tubes allows the engineering of biotin-streptavidin crosslinks between them. The order of introducing PEG and streptavidin in the system further affects the formed hierarchical assemblies, as well as their resistance toward dilution. The strategy described here provides a new route to establish hierarchically organized supramolecular architectures, combining crowding and specific biomolecular interactions, which shows the potential for controlling the structure of supramolecular materials and other soft matter systems.

Multivalent Noncovalent Interfacing and Cross-Linking of Supramolecular Tubes.

Natural supramolecular filaments have the ability to cross-link with each other and to interface with the cellular membrane via biomolecular noncovalent interactions. This behavior allows them to form complex networks within as well as outside the cell, i.e., the cytoskeleton and the extracellular matrix, respectively. The potential of artificial supramolecular polymers to interact through specific noncovalent interactions has so far only seen limited exploration due to the dynamic nature of supramolecular interactions. Here, a system of synthetic supramolecular tubes that cross-link forming supramolecular networks, and at the same time bind to biomimetic surfaces by the aid of noncovalent streptavidin-biotin linkages, is demonstrated. The architecture of the networks can be engineered by controlling the density of the biotin moiety at the exterior of the tubes as well as by the concentration of the streptavidin. The presented strategy provides a pathway for designing adjustable artificial supramolecular superstructures, which can potentially yield more complex biomimetic adaptive materials.

The tesseract in two dimensional materials, a DFT approach.

A series of novel two-dimensional materials inspired from a 4D polytope, tesseract, have been proposed by density functional theory (DFT) based computations. Both C24X12 and C16X16 (X = O, S and Se) are found to have great thermodynamic and dynamic stabilities, and C24X12 exhibited excellent thermal stability up to 1000 K. All these 2D crystals are semiconductors with 2.17 eV to 3.35 eV band gaps at the HSE06 theoretical level, except for C24S12 (4.14 eV energy gap). Moreover, the intrinsic pore sizes of C24Se12 are suitable to sieve He from the He/CH4 mixture, with over 80% separation ratio and nearly 100% selectivity. Our findings not only enlarged the boundary of the 2D family, but also offered another potential method to recover helium from natural gas at ambient conditions.