Peptide-Controlled Assembly of Macroscopic Calcium Oxalate Nanosheets.

The fabrication of two-dimensional (2D) biomineral nanosheets is of high interest owing to their promise for applications in electronics, filtration, catalysis, and chemical sensing. Using a facile approach inspired by biomineralization in nature, we fabricate laterally macroscopic calcium oxalate nanosheets using β-folded peptides. The template peptides are composed of repetitive glutamic acid and leucine amino acids, self-organized at the air-water interface.

A hydrated crystalline calcium carbonate phase: Calcium carbonate hemihydrate.

As one of the most abundant materials in the world, calcium carbonate, CaCO, is the main constituent of the skeletons and shells of various marine organisms. It is used in the cement industry and plays a crucial role in the global carbon cycle and formation of sedimentary rocks. For more than a century, only three polymorphs of pure CaCO-calcite, aragonite, and vaterite-were known to exist at ambient conditions, as well as two hydrated crystal phases, monohydrocalcite (CaCO·1HO) and ikaite (CaCO·6HO).

Calcium-Induced Molecular Rearrangement of Peptide Folds Enables Biomineralization of Vaterite Calcium Carbonate.

Proteins can control mineralization of CaCO by selectively triggering the growth of calcite, aragonite or vaterite phases. The templating of CaCO by proteins must occur predominantly at the protein/CaCO interface, yet molecular-level insights into the interface during active mineralization have been lacking. Here, we investigate the role of peptide folding and structural flexibility on the mineralization of CaCO.

Lattice distortions in coccolith calcite crystals originate from occlusion of biomacromolecules.

During biomineralization, organisms control the formation and morphology of a mineral using biomacromolecules. The biomacromolecules that most strongly interact with the growing crystals frequently get occluded within. Such an observation has been recently obtained for the calcium carbonate producing coccolithophore species Pleurochrysis carterae.

A vacuole-like compartment concentrates a disordered calcium phase in a key coccolithophorid alga.

Coccoliths are calcitic particles produced inside the cells of unicellular marine algae known as coccolithophores. They are abundant components of sea-floor carbonates, and the stoichiometry of calcium to other elements in fossil coccoliths is widely used to infer past environmental conditions. Here we study cryo-preserved cells of the dominant coccolithophore Emiliania huxleyi using state-of-the-art nanoscale imaging and spectroscopy.

Biomimetic vaterite formation at surfaces structurally templated by oligo(glutamic acid) peptides.

Previous studies have reported that the metastable vaterite phase of calcium carbonate can be stabilized in solution by acidic additives. Here we demonstrate that vaterite can also be stabilized directly at surfaces by engineered peptides. Our data show that the mineralisation occurs in a 'self-templating' process where calcium ions restructure the peptide backbone, which in turn allows for effective vaterite precipitation.

Synthetic Strategies in the Preparation of Polymer/Inorganic Hybrid Nanoparticles.

This article reviews the recent advances and challenges in the preparation of polymer/inorganic hybrid nanoparticles. We mainly focus on synthetic strategies, basing our classification on whether the inorganic and the polymer components have been formed or , of the hybrid material. Accordingly, four types of strategies are identified and described, referring to recent examples: (i) formation of the components and subsequent attachment or integration, either by covalent or noncovalent bonding; (ii) polymerization in the presence of formed inorganic nanoparticles; (iii) precipitation of the inorganic components or polymer structures; and (iv) strategies in which both polymer and inorganic component are simultaneously formed .

On the causes of potential inversion in 1,2,4,5-tetrakis(amino)benzenes.

Three 3,6-difluoro-1,2,4,5-tetrakis(amino)benzene compounds, bearing dimethylamino (1), piperidin-1-yl (3), or morpholin-1-yl (5) substituents, have been synthesized and subsequently defluorinated to give the corresponding 1,2,4,5-tetrakis(amino)benzene compounds 2, 4, and 6; the crystal structures of compounds 1, 4, and 6 have been obtained. Cyclic voltammetry shows that all six compounds will lose two electrons to form dications, and the use of suitable oxidizing agents has allowed isolation and crystallographic characterization of the dications 2(2+) and 6(2+) (as [PF(6)](2) salts) and 4(2+) (as a [I(5)][I(3)] salt). The separation DeltaE between the loss of the first electron and the second varies between compounds, from 0.