Synthesis of Metastable Calcium Carbonate Using Long-Chain Bisphosphonate Molecules.

Cementation in construction materials primarily relies on the aqueous precipitation of minerals such as carbonates and silicates. The kinetics of nucleation and growth play a critical role in the development of strength and durability, yet our understanding of the kinetic controls governing phase formation and porosity reduction in cements remains limited. In this study, we synthesized bisphosphonate molecules with varying alkyl chain lengths and functional groups to investigate their impact on calcium carbonate precipitation. Through conductivity measurements, infrared spectroscopy, and thermogravimetric analysis, we uncovered the selective formation of polymorphs and the specific incorporation of these molecules within the carbonate matrix. Further, in situ atomic force microscopy revealed that these molecules influenced the morphology of the precipitates, indicating a possible effect on the ionic organization through sorption mechanisms. Interestingly, amorphous calcium carbonate (ACC), when formed in the presence of bisphosphonates, showed metastability for at least seven months without inhibiting further calcium carbonate precipitation. Our research sheds light on the diverse mechanisms by which organic additives can modify mineral nucleation and growth, offering valuable insights for the control and enhancement of carbonate-based cementation processes.

Modular Design of Supramolecular Ionic Peptides with Cell-Selective Membrane Activity.

The rational design of materials with cell-selective membrane activity is an effective strategy for the development of targeted molecular imaging and therapy. Here we report a new class of cationic multidomain peptides (MDPs) that can undergo enzyme-mediated molecular transformation followed by supramolecular assembly to form nanofibers in which cationic clusters are presented on a rigid ß-sheet backbone. This structural transformation, which is induced by cells overexpressing the specific enzymes, led to a shift in the membrane perturbation potential of the MDPs, and consequently enhanced cell uptake and drug delivery efficacy. We envision the directed self-assembly based on modularly designed MDPs as a highly promising approach to generate dynamic supramolecular nanomaterials with emerging membrane activity for a range of disease targeted molecular imaging and therapy applications.

Flavin Nitroalkane Oxidase Mimics Compatibility with NOx/TEMPO Catalysis: Aerobic Oxidization of Alcohols, Diols, and Ethers.

Biomimetic flavin organocatalysts oxidize nitromethane to formaldehyde and NOx-providing a relatively nontoxic, noncaustic, and inexpensive source for catalytic NO2 for aerobic TEMPO oxidations of alcohols, diols, and ethers. Alcohols were oxidized to aldehydes or ketones, cyclic ethers to esters, and terminal diols to lactones. In situ trapping of NOx and formaldehyde suggest an oxidative Nef process reminiscent of flavoprotein nitroalkane oxidase reactivity, which is achieved by relatively stable 1,10-bridged flavins. The metal-free flavin/NOx/TEMPO catalytic cycles are uniquely compatible, especially compared to other Nef and NOx-generating processes, and reveal selectivity over flavin-catalyzed sulfoxide formation. Aliphatic ethers were oxidized by this method, as demonstrated by the conversion of (-)-ambroxide to (+)-sclareolide.