Intrinsisch ungeordnete Osteopontin-Fragmente ordnen sich während der interfazialen Calciumoxalat-Mineralisierung

Calcium oxalate (CaC(2)O(4)) is the major component of kidney stone. The acidic osteopontin (OPN) protein in human urine can effectively inhibit the growth of CaC(2)O(4) crystals, thereby acting as a potent stone preventer. Previous studies in bulk solution all attest to the importance of binding and recognition of OPN at the CaC(2)O(4) mineral surface, yet molecular level insights into the active interface during CaC(2)O(4) mineralization are still lacking. Here, we probe the structure of the central OPN fragment and its interaction with Ca(2+) and CaC(2)O(4) at the water–air interface using surface‐specific non‐linear vibrational spectroscopy. While OPN peptides remain largely disordered in solution, our results reveal that the bidentate binding of Ca(2+) ions refold the interfacial peptides into well‐ordered and assembled β‐turn motifs. One critical intermediate directs mineralization by releasing structural freedom of backbone and binding side chains. These insights into the mineral interface are crucial for understanding the pathological development of kidney stones and possibly relevant for calcium oxalate biomineralization in general

RNA-inspired intramolecular transesterification accelerates the hydrolysis of polyethylene-like polyphosphoesters

To synthesize new (bio)degradable alternatives to commodity polymers, adapting natural motives can be a promising approach. We present the synthesis and characterization of degradable polyethylene (PE)-like polyphosphoesters, which exhibit increased degradation rates due to an intra-molecular transesterification similar to RNA. An α,ω-diene monomer was synthesized in three steps starting from readily available compounds. By acyclic diene metathesis (ADMET) polymerization, PE-like polymers with molecular weights up to 38 400 g mol(−1) were obtained. Post-polymerization functionalization gave fully saturated and semicrystalline polymers with a precise spacing of 20 CH(2) groups between each phosphate group carrying an ethoxy hydroxyl side chain. This side chain was capable of intramolecular transesterification with the main-chain similar to RNA-hydrolysis, mimicking the 2′-OH group of ribose. Thermal properties were characterized by differential scanning calorimetry (DSC (T(m)ca. 85 °C)) and the crystal structure was investigated by wide-angle X-ray scattering (WAXS). Polymer films immersed in aqueous solutions at different pH values proved an accelerated degradation compared to structurally similar polyphosphoesters without pendant ethoxy hydroxyl groups. Polymer degradation proceeded also in artificial seawater (pH = 8), while the polymer was stable at physiological pH of 7.4. The degradation mechanism followed the intra-molecular “RNA-inspired” transesterification which was detected by NMR spectroscopy as well as by monitoring the hydrolysis of a polymer blend of a polyphosphoester without pendant OH-group and the RNA-inspired polymer, proving selective hydrolysis of the latter. This mechanism has been further supported by the DFT calculations. The “RNA-inspired” degradation of polymers could play an important part in accelerating the hydrolysis of polymers and plastics in natural environments, e.g. seawater

Polymer defect engineering-conductive 2D organic platelets from precise thiophene-doped polyethylene

We developed a simple way to create 2D conductive nanostructures with dielectric cores and conductive surfaces based on polyethylene with in-chain thiophene groups. Generally, thiophene-based polymers show great conductive properties, but exhibit a poor processability. Here, we use the crystallization of a polyethylene chain with precisely distributed thiophene groups as the platform for a self-organization of a lamellar structure. During crystallization, thiophene groups are expelled to the crystal surface. Subsequent copolymerization with 3,4-ethylenedioxythiophene (EDOT) molecules finally yields 2D platelets with a conductive surface. The electric properties of the surface are demonstrated by conductivity measurements. Given the molecular structure of the polymer, it can be assumed that the conductive layer consists of only one monoatomic layer of polymerized thiophene. We thus show a new way to create an ultra-thin, conductive surface on a polymer surface in just a few steps. Hence, the method presented here opens up a wide range of possibilities to produce complex, nanoscale electronic structures for microelectronic applications