Pettersonvilladsen7479

e-metallosurfactant system for the design of therapeutic cisplatin compositions.Linker exchange is a widely applied, robust technique for elaboration of metal-organic frameworks (MOFs) post-synthesis. The observation of core-shell microstructures under certain conditions was hypothesized to arise from diffusion rates into the MOF that are slower than linker exchange. Here the relative contributions of these processes are manipulated through solvent choice in order to modulate shell thickness and exchange extent. The findings allow tailoring MOF microstructure to application.Selective oxidative deamination has long been considered to be an important but challenging transformation, although it is a common critical process in the metabolism of bioactive amino compounds. Most of the synthetic methods developed so far rely on the use of stoichiometric amounts of strong and toxic oxidants. Here we present a green and efficient method for oxidative deamination, using water as the oxidant, catalyzed by a ruthenium pincer complex. This unprecedented reaction protocol liberates hydrogen gas and avoids the use of sacrificial oxidants. A wide variety of primary amines are selectively transformed to carboxylates or ketones in good to high yields. It is noteworthy that mechanistic experiments and DFT calculations indicate that in addition to serving as the oxidant, water also plays an important role in assisting the hydrogen liberation steps involved in amine dehydrogenation.Oligomers of the β-amyloid peptide, Aβ, play a central role in the pathogenesis and progression of Alzheimer's disease. Trimers and higher-order oligomers composed of trimers are thought to be the most neurotoxic Aβ oligomers. To gain insights into the structure and assembly of Aβ oligomers, our laboratory has previously designed and synthesized macrocyclic peptides derived from Aβ17-23 and Aβ30-36 that fold to form β-hairpins and assemble to form trimers. In this study, we found that mutating Phe20 to cyclohexylalanine (Cha) in macrocyclic Aβ-derived peptides promotes crystallization of an Aβ-derived peptide containing the Aβ24-29 loop (peptide 3 F20Cha ) and permits elucidation of its structure and assembly by X-ray crystallography. X-ray crystallography shows that peptide 3 F20Cha forms a hexamer. X-ray crystallography and SDS-PAGE further show that trimer 4 F20Cha , a covalently stabilized trimer derived from peptide 3 F20Cha , forms a dodecamer. Size exclusion chromatography shows that trimer 4 F20Cha forms higher-order assemblies in solution. Trimer 4 F20Cha exhibits cytotoxicity against the neuroblastoma cell line SH-SY5Y. These studies demonstrate the use of the F20Cha mutation to further stabilize oligomers of Aβ-derived peptides that contain more of the native sequence and thus better mimic the oligomers formed by full-length Aβ.Several anaerobic bacteria can couple the reduction of aromatic halides to energy conservation. This organohalide respiration is catalyzed by enzymes containing cob(I)alamin, an activated supernucleophilic form of the coenzyme vitamin B12. However, the mechanism underlying the electron transfer (inner-sphere vs outer-sphere ET) still remains elusive. To clarify this issue, we selected 36 fluoro-, chloro-, and bromobenzenes as representative substrates and calculated their free-energy barriers at the quantum chemical density functional theory level, considering a wide range of theoretically possible outer-sphere ET mechanisms. Across all 336 reaction routes addressed, 334 routes involve free-energy barriers larger than 20 kcal/mol. For two reaction routes with highly brominated benzenes, free-energy barriers below 20 kcal/mol imply abiotic reduction as observed in experiments. Thus, microbial B12-dependent aromatic reductive dehalogenation does not proceed through an outer-sphere ET mechanism. Instead, the present study strongly suggests that microbe-catalyzed reductive dehalogenation of aromatic halides is governed by inner-sphere ET.Nitrous oxide (N2O) is a potentially important oxidant for green chemistry applications but thus far has shown limited examples as a ligand for transition metal complexes. Given the lack of reported N2O complexes, density functional theory was utilized to study the potential binding effects in multiple group 8 metal complexes. N2O is found to be a very weakly π-accepting ligand (approximately 1/3 as effective as CO). With the weak π-accepting character, the N2O is predicted to be bound through the nitrogen atom in a linear geometry. In all calculated ruthenium and osmium complexes, the nitrogen bound mode of binding is preferred. Only by introduction of a very weak π-donor metal (such as iron) can the N2O be found to slightly prefer binding through the oxygen atom in a purely σ-donor fashion.It is evident that the exhaustive use of fossil fuels for decades has significantly contributed to global warming and environmental pollution. To mitigate the harm on the environment, lithium-oxygen batteries (LOBs) with a high theoretical energy density (3458 Wh kg-1Li2O2) compared to that of Li-ion batteries (LIBs) have been considered as an attractive alternative to fossil fuels. For this purpose, porous carbon materials have been utilized as promising air cathodes owing to their low cost, lightness, easy fabrication process, and high performance. However, the challenge thus far lies in the uncontrollable formation of Li2CO3 at the interface between carbon and Li2O2, which is detrimental to the stable electrochemical performance of carbon-based cathodes in LOBs. In this work, we successfully protected the surface of the free-standing carbon nanofibers (CNFs) by coating it with a layer of iridium metal through direct sputtering (CNFs@Ir), which significantly improved the lifespan of LOBs. Moreover, the Ir would play a secondary role as an electrochemical catalyst. selleck chemicals llc This all-in-one cathode was evaluated for the formation and decomposition of Li2O2 during (dis)charging processes. Compared with bare CNFs, the CNFs@Ir cathode showed two times longer lifespan with 0.2 VLi lower overpotentials for the oxygen evolution reaction. We quantitatively calculated the contents of CO32- in Li2CO3 formed on the different surfaces of the bare CNFs (63% reduced) and the protected CNFs@Ir (78% reduced) cathodes after charging. The protective effects and the reaction mechanism were elucidated by ex situ analyses, including scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy.