Mechanical adaptation of brachiopod shells via hydration-induced structural changes.

The function-optimized properties of biominerals arise from the hierarchical organization of primary building blocks. Alteration of properties in response to environmental stresses generally involves time-intensive processes of resorption and reprecipitation of mineral in the underlying organic scaffold. Here, we report that the load-bearing shells of the brachiopod Discinisca tenuis are an exception to this process. These shells can dynamically modulate their mechanical properties in response to a change in environment, switching from hard and stiff when dry to malleable when hydrated within minutes. Using ptychographic X-ray tomography, electron microscopy and spectroscopy, we describe their hierarchical structure and composition as a function of hydration to understand the structural motifs that generate this adaptability. Key is a complementary set of structural modifications, starting with the swelling of an organic matrix on the micron level via nanocrystal reorganization and ending in an intercalation process on the molecular level in response to hydration

A Naturally Associated Rhizobacterium of Arabidopsis thaliana Induces a Starvation-Like Transcriptional Response while Promoting Growth

Plant growth promotion by rhizobacteria is a known phenomenon but the underlying mechanisms are poorly understood. We searched for plant growth-promoting rhizobacteria that are naturally associated with Arabidopsis thaliana to investigate the molecular mechanisms that are involved in plant growth-promotion. We isolated a Pseudomonas bacterium (Pseudomonas sp. G62) from roots of field-grown Arabidopsis plants that has not been described previously and analyzed its effect on plant growth, gene expression and the level of sugars and amino acids in the host plant. Inoculation with Pseudomonas sp. G62 promoted plant growth under various growth conditions. Microarray analysis revealed rapid changes in transcript levels of genes annotated to energy-, sugar- and cell wall metabolism in plants 6 h after root inoculation with P. sp. G62. The expression of several of these genes remained stable over weeks, but appeared differentially regulated in roots and shoots. The global gene expression profile observed after inoculation with P. sp. G62 showed a striking resemblance with previously described carbohydrate starvation experiments, although plants were not depleted from soluble sugars, and even showed a slight increase of the sucrose level in roots 5 weeks after inoculation. We suggest that the starvation-like transcriptional phenotype - while steady state sucrose levels are not reduced - is induced by a yet unknown signal from the bacterium that simulates sugar starvation. We discuss the potential effects of the sugar starvation signal on plant growth promotion

Strain-Induced Self-Rolling of Electrochemically Deposited Co(OH)₂ Films into Organic–Inorganic Microscrolls

Strain-induced self-folding is a ubiquitous phenomenon in biology, but is rarely seen in brittle geological or synthetic inorganic materials. We here apply this concept for the preparation of three-dimensional free-standing microscrolls of cobalt hydroxide. Electrodeposition in the presence of structure-directing water-soluble polyelectrolytes interfering with solid precipitation is used to generate thin polymer/inorganic hybrid films, which undergo self-rolling upon drying. Mechanistically, we propose that heterogeneities with respect to the nanostructural motifs along the surface normal direction lead to substantial internal strain. A non-uniform response to the release of water then results in a bending motion of the two-dimensional Co(OH)2 layer accompanied by dewetting from the substrate. Pseudomorphic conversion into Co3O4 affords the possibility to generate hierarchically structured solids with inherent catalytic activity. Hence, we present an electrochemically controllable precipitation system, in which the biological concepts of organic matrix-directed mineralization and strain-induced self-rolling are combined and translated into a functional material

Strain-Induced Self-Rolling of Electrochemically Deposited Co(OH)2 Films into Organic–Inorganic Microscrolls

Strain-induced self-folding is a ubiquitous phenomenon in biology, but is rarely seen in brittle geological or synthetic inorganic materials. We here apply this concept for the preparation of three-dimensional free-standing microscrolls of cobalt hydroxide. Electrodeposition in the presence of structure-directing water-soluble polyelectrolytes interfering with solid precipitation is used to generate thin polymer/inorganic hybrid films, which undergo self-rolling upon drying. Mechanistically, we propose that heterogeneities with respect to the nanostructural motifs along the surface normal direction lead to substantial internal strain. A non-uniform response to the release of water then results in a bending motion of the two-dimensional Co(OH)2 layer accompanied by dewetting from the substrate. Pseudomorphic conversion into Co3O4 affords the possibility to generate hierarchically structured solids with inherent catalytic activity. Hence, we present an electrochemically controllable precipitation system, in which the biological concepts of organic matrix-directed mineralization and strain-induced self-rolling are combined and translated into a functional material

Interface-mediated formation of basic cobalt carbonate/polyethyleneimine composite microscrolls by strain-induced self-rolling

Polyethyleneimine aids the gas diffusion precipitation of nano-structured basic cobalt carbonate sheets at the air/solution interface. Upon drying, these mineral films undergo self-rolling into 3D coiled structures. Exploring this principle for the design of self-supported functional materials, porous Co$_3$O$_4$ spirals composed of interconnected nanoparticles are obtained by thermal conversion

Virtually Wall-Less Tubular Sponges as Compartmentalized Reaction Containers

Sponges are open cellular materials with numerous interesting features. However, the potential of compartmentalized sponges has not been explored although many new properties and applications could be envisioned. We found that compartmentalized fibrous ultraporous polymer sponges with superhydrophobic surfaces could be designed as virtually wall-less reaction containers. With this, for example, the efficient removal of CO2 from water and the controlled mineralization of calcium carbonate are possible. The high porosity (>99%) and superhydrophobicity make these sponges ideal candidates to hold alkanolamine solution for absorbing CO2 and exchange gas through the walls of the sponges. The tubular sponge exhibits a much higher evaporation rate than a glass tube with the same diameter due to the much larger contact area between water and air. Therefore, the spongy reaction container also possesses a much faster adsorption rate, smaller equilibration time and higher efficiency for CO2 adsorption than the glass tube container. In addition, these tubular sponges are also utilized to precipitate calcium carbonate by ammonium carbonate decomposition, which can control the deposition rates and products by tailoring the porosity and surface chemistry in the future. These new sponges provide an ideal basis for numerous new applications, for example, as breathable pipe lines for gas-liquid exchange, slag slurry carbonization, humidifier, and blood enricher

Mechanical Adaptation of Brachiopod Shells Via Hydration-Induced Structural Changes

This dataset accompanies the paper "Mechanical Adaptation of Brachiopod Shells Via Hydration-Induced Structural Changes", where using ptychographic X-ray tomography, electron microscopy and spectroscopy, we describe the hierarchical structure and composition of the shell of the brachiopod Discinisca tenuis as a function of hydration. We show that absorption of water by these shells results in structural changes at the micron- nano- and molecular scales, resulting in the material switching from hard and stiff when dry to malleable when hydrated within minutes. The deposited dataset includes the reconstructed X-ray ptychography tomograms of shells that were dry, exposed to 70 % relative humidity and 100 % relative humidity and the original electron microscopy images (SEM, STEM) that are presented in the paper.Nudelman, Fabio; Ihli, Johannes; Wakonig, Klaus; Holler, Mirko; Glen, Thomas; Schenk, Anna S.; Rosenfeldt, Sabine; Falini, Giuseppe; Pasquini, Luca; Delacou, Eugenia; Buckman, Jim; Kress, Thomas; Tsai, Esther H. R.; Reid, David G.; Duer, Melinda J.; Cusack, Maggie (2021). Mechanical Adaptation of Brachiopod Shells Via Hydration-Induced Structural Changes, 2014-2019 [dataset]. University of Edinburgh. School of Chemistry. https://doi.org/10.7488/ds/3056