Living Materials Constructed with Dynamic Covalent Interface between Synthetic Polymers and B. subtilis

With advances in the field of synthetic biology increasingly allowing us to engineer living cells to perform intricate tasks, incorporating these engineered cells into the design of synthetic polymeric materials will enable programming materials with a wide range of biological functionalities. However, employable strategies for the design of synthetic polymers that form a well-defined interface with living cells and seamlessly integrate their functionalities in materials are still largely limited. Herein, we report the first example of living materials constructed with a dynamic covalent interface between synthetic polymers and living B. subtilis cells. We showedthat 3-acetamidophenylboronic acid (APBA) and polymers of APBA (pAPBA) form dynamic covalent bonds with available diols on the B. subtilis cell surface. Importantly, pAPBA binding to B. subtilis shows a multivalent effect with complete reversibility upon addition of competitive diol species, such as fructose and sorbitol. On the basis of these findings, we constructed telechelic block copolymers with pAPBA chain ends that crosslink B. subtilis cells and produced self- standing living materials. We further demonstrated that the encapsulated cells could be retrieved upon immersing these materials in solutions containing competitive diols and further subjected to biological analyses. This work establishes the groundwork for building a myriad of synthetic polymeric materials integrating engineered living cells and provides a platform for understanding the biology of cells confined within materials.

Real-Space Interpretation of Interatomic Charge Transfer and Electron Exchange Effects by Combining Static and Kinetic Potentials and Associated Vector Fields

Intricate behavior of one-electron potentials from the Euler equation for electron density and corresponding gradient force fields in crystals was studied. Bosonic and fermionic quantum potentials were utilized in bonding analysis as descriptors of the localization of electrons and electron pairs. Channels of locally enhanced kinetic potential and the corresponding saddle Lagrange points were found between chemically bonded atoms linked by the bond paths. Superposition of electrostatic φ_es (r) and kinetic φ_k (r) potentials and electron density ρ(r) allowed partitioning any molecules and crystals into atomic ρ- and potential-based φ-basins; the φ_k-basins explicitly account for electron exchange effect, which is missed for φ_es-ones. Phenomena of interatomic charge transfer and related electron exchange were explained in terms of space gaps between ρ- and φ-zero-flux surfaces. The gap between φ_es- and ρ-basins represents the charge transfer, while the gap between φ_k- and ρ-basins is proposed to be a real-space manifestation of sharing the transferred electrons. The position of φ_k-boundary between φ_es- and ρ-ones within an electron occupier atom determines the extent of electron sharing. The stronger an H‧‧‧O hydrogen bond is, the deeper hydrogen atom’s φ_k-basin penetrates oxygen atom’s ρ-basin. For covalent bonds, a φ_k-boundary closely approaches a φ_es-one indicating almost complete sharing the transferred electrons, while for ionic bonds, the same region corresponds to electron pairing within the ρ-basin of an electron occupier atom.

On the Nature of the Bonding in Coinage Metal Halides

This article analyzes the nature of the chemical bond in coinage metal halides using high-level ab initio Valence Bond (VB) theory. It is shown that these bonds display a large Charge-Shift Bonding character, which is traced back to the large Pauli pressure arising from the interaction between the bond pair with the filled semicore d shell of the metal. The gold-halide bonds turn out to be pure Charge-Shift Bonds (CSBs), while the copper halides are polar-covalent bonds and silver halides borderline cases. Among the different halogens, the largest CSB character is found for fluorine, which experiences the largest Pauli pressure from its σ lone pair. Additionally, all these bonds display a secondary but non-negligible π bonding character, which is also quantified in the VB calculations.

One-pot synthesis of high-capacity silicon anodes via on-copper growth of a semi-conducting, porous polymer

Silicon-based anodes with lithium ions as charge carriers have the highest predicted theoretical specific capacity of 3579 mA h g (for LiSi). Contemporary electrodes do not achieve this theoretical value largely because conventional production paradigms rely on the mixing of weakly coordinated components. In this paper, a semi-conductive triazine-based graphdiyne polymer network is grown around silicon nanoparticles directly on the current collector, a copper sheet. The porous, semi-conducting organic framework (i) adheres to the current collector on which it grows via cooperative van der Waals interactions, (ii) acts effectively as conductor for electrical charges and binder of silicon nanoparticles via conjugated, covalent bonds, and (iii) enables selective transport of electrolyte and Li-ions through pores of defined size. The resulting anode shows extraordinarily high capacity at the theoretical limit of fully lithiated silicon. Finally, we combine our anodes in proof-of-concept battery assemblies using a conventional layered Ni-rich oxide cathode.

GOx-assisted synthesis of pillar[5]arene based supramolecular polymeric nanoparticles for targeted/synergistic chemo-chemodynamic cancer therapy

Background Cancer is the most serious world's health problems on the global level and various strategies have been developed for cancer therapy. Pillar[5]arene-based supramolecular therapeutic nano-platform (SP/GOx NPs) was constructed successfully via orthogonal dynamic covalent bonds and intermolecular H-bonds with the assistance of glucose oxidase (GOx) and exhibited efficient targeted/synergistic chemo-chemodynamic cancer therapy. Methods The morphology of SP/GOx NPs was characterized by DLS, TEM, SEM and EDS mapping. The cancer therapy efficinecy was investigated both in vivo and in vitro. Results SP/GOx NPs can load drug molecules (Dox) and modify target molecule (FA-Py) on its surface conveniently. When the resultant FA-Py/SP/GOx/Dox NPs enters blood circulation, FA-Py will target it to cancer cells efficiently, where GOx can catalyst the overexpressed glucose to generate H2O2. Subsequently, the generated H2O2 in cancer cells catalyzed by ferrocene unit to form •OH, which can kill cancer cells. Furthermore, the loaded Dox molecules released under acid microenvironment, which can further achieve chemo-therapy. Conclusion All the experiments showed that the excellent antitumor performance of FA-Py/SP/GOx/Dox NPs, which provided an new method for pillar[5]arene-based supramolecular polymer for biomedical applications. Graphical Abstract

Exploring the folding energy landscapes of heme proteins using a hybrid AWSEM-heme model

Heme is an active center in many proteins. Here we explore computationally the role of heme in protein folding and protein structure. We model heme proteins using a hybrid model employing the AWSEM Hamiltonian, a coarse-grained forcefield for the protein chain along with AMBER, an all-atom forcefield for the heme. We carefully designed transferable force fields that model the interactions between the protein and the heme. The types of protein–ligand interactions in the hybrid model include thioester covalent bonds, coordinated covalent bonds, hydrogen bonds, and electrostatics. We explore the influence of different types of hemes (heme b and heme c) on folding and structure prediction. Including both types of heme improves the quality of protein structure predictions. The free energy landscape shows that both types of heme can act as nucleation sites for protein folding and stabilize the protein folded state. In binding the heme, coordinated covalent bonds and thioester covalent bonds for heme c drive the heme toward the native pocket. The electrostatics also facilitates the search for the binding site.

Layer-by-Layer Deposition: A Promising Environmentally Benign Flame-Retardant Treatment for Cotton, Polyester, Polyamide and Blended Textiles

A detailed review of recent developments of layer-by-layer (LbL) deposition as a promising approach to reduce flammability of the most widely used fibers (cotton, polyester, polyamide and their blends) is presented. LbL deposition is an emerging green technology, showing numerous advantages over current commercially available finishing processes due to the use of water as a solvent for a variety of active substances. For flame-retardant (FR) purposes, different ingredients are able to build oppositely charged layers at very low concentrations in water (e.g., small organic molecules and macromolecules from renewable sources, inorganic compounds, metallic or oxide colloids, etc.). Since the layers on a textile substrate are bonded with pH and ion-sensitive electrostatic forces, the greatest technological drawback of LbL deposition for FR finishing is its non-resistance to washing cycles. Several possibilities of laundering durability improvements by different pre-treatments, as well as post-treatments to form covalent bonds between the layers, are presented in this review.

Towards a Density-Based Description of Chemical Bonds and Noncovalent Interactions with Pauli Energy

Chemical bonds and noncovalent interactions are extraordinarily important concepts in chemistry and beyond. Using density-based quantities to describe them has a long history in the literature, yet none can satisfactorily describe the entire spectrum of interactions from strong chemical bonds to weak van der Waals forces. In this work, employing Pauli energy as the theoretical foundation, we fill in that knowledge gap. Our results show that the newly established density-based index can describe single and multiple covalent bonds, ionic bonds, metallic bonds, and different kinds of noncovalent interactions, all with unique and readily identifiable signature shapes. Two new descriptors, NBI (nonbonding and bonding identification) index and USI (ultra-strong interaction) index, have been introduced in this work. Together with NCI (noncovalent interaction) and SCI (strong covalent interaction) indexes already available in the literature, a density-based description of both chemical bonds and noncovalent interactions is accomplished.