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Mccullough Peterson posted an update 6 months, 1 week ago
The synthesis of metal-organic frameworks (MOFs) has, to date, largely been in the form of crystalline powders. However, interest in different physical morphologies of this class of materials is growing. In this perspective, we provide an overview of the structure, properties and applications of MOF monoliths. In particular, we explore the complex synthetic landscapes associated with MOF crystallization and discuss the synthetic factors leading to the formation of MOF gels, i.e. the precursor to sol-gel MOF monoliths. Finally, we provide our thoughts on the future development of this field, and attempt to highlight the importance of the MOF gel state in the discovery of new functional materials. This journal is © The Royal Society of Chemistry 2020.Amino acids and peptides with bulky side chains are of significant importance in organic synthesis and modern medicinal chemistry. The efficient synthesis of these molecules with full enantiocontrol and high diversity remains challenging. Herein we report a Pd-catalyzed ligand-enabled γ-C(sp3)-H arylation of tert-leucine and its derived peptides without using an external directing group (DG) via a less favored six-membered palladacycle. Structurally diverse bulky side chain amino acids and peptides were accessed in a step-economic fashion and the reaction could be conducted on a gram scale with retention of chirality. The resulting amino acids can be used as chiral ligands in Co(iii)-catalyzed enantioselective C(sp3)-H amidation. It is worth noting that the weakly coordinating carboxylate DG outcompetes the strongly coordinating bidentate DG of the peptide backbone, providing the products of γ-C(sp3)-H arylation of Tle residue exclusively. This protocol represents the first example of late stage C(sp3)-H functionalization of peptides using a weakly coordinating directing group. This journal is © The Royal Society of Chemistry 2020.The surface of the influenza virus is decorated with the receptor-binding protein hemagglutinin (HA) and the receptor-cleaving enzyme neuraminidase (NA). HA is responsible for host cell recognition, while NA prevents aggregation and entrapment, but the intricate mechanism of how the functions of these glycoproteins cooperate and how they are regulated by mutational responses to environmental pressures remains unclear. Recently, several groups have described the motion of influenza over surfaces and reported that this motion is inhibited by NA inhibitors. We argue that the motion of influenza resembles the motility of artificial receptor-cleaving particles called “molecular spiders”. The cleaving of receptors by this type of molecular walkers leads to self-avoiding motion across a surface. When the binding and cleaving rates of molecular spiders are balanced, they move both rapidly and efficiently. The studies of molecular spiders offer new insights into the functional balance of HA and NA, but they do not address the asymmetric distribution of HA and NA on the surface of influenza. We propose that receptor-cleaving molecular walkers could play an important role in the further investigation of the motility of influenza viruses. This journal is © The Royal Society of Chemistry 2020.As a major class of mammalian lipids, phosphatidylcholines (PCs) often contain mixtures of structural isomers, resulting from different lipogenesis pathways. Profiling PCs at the isomer level, however, remains challenging in lipidomic settings, especially for characterizing the positions of fatty acyls on the glycerol backbone (sn-positions) and the locations of carbon-carbon double bonds (CCs) in unsaturated acyl chains. In this work, we have developed a workflow for profiling PCs down to sn- and CC locations at high coverage and sensitivity. This capability is enabled by radical-directed fragmentation, forming sn-1 specific fragment ions upon collision-induced dissociation (CID) of bicarbonate anion adducts of PCs (-) inside a mass spectrometer. This new tandem mass spectrometry (MS/MS) method can be simply incorporated into liquid chromatography by employing ammonium bicarbonate in the mobile phase without any instrument modification needed. It is also compatible with the online Paternò-Büchì reaction and subsequent MS/MS for the assignment of CC locations in sn-1 fatty acyl chains of unsaturated PCs. The analytical performance of the workflow is manifested by identification of 82 distinct PC molecular species from the polar extract of bovine liver, including quantification of 19 pairs of sn-isomers. see more Finally, we demonstrate that five pairs of PC sn-isomers show significant compositional changes in tissue samples of human breast cancer relative to controls, suggesting a potential for monitoring PC sn-isomers for biomedical applications. This journal is © The Royal Society of Chemistry 2019.Linear acenes are a well-studied class of polycyclic aromatic hydrocarbons and their established physical properties have led to their widespread application across the field of organic electronics. However, their quinoidal forms – dihydroacenes – are much less explored and exhibit vastly different photophysical and electronic properties due to their non-planar, cross-conjugated nature. In this work, we present a series of difluorenylidene dihydroacenes which exhibit a butterfly-like structure with a quinoidal skeleton, resulting in comparatively higher optical gaps and lower redox activities than those of their planar analogs. We found that these compounds exhibit aggregation induced emission (AIE), activated through restriction of the “flapping” vibrational mode of the molecules in the solid state. Furthermore, anthracene-containing dihydroacenes exhibit thermally activated ground-state spin switching as evidenced by planarization of the acene core and diradical activity recorded by EPR. These two characteristics in this relatively unexplored class of materials provide new insights for the design of multifunctional materials. This journal is © The Royal Society of Chemistry 2019.We have developed a glass nanopore based single molecule tool to investigate the dynamic oligomerization and aggregation process of Aβ1-42 peptides. The intrinsic differences in the molecular size and surface charge of amyloid aggregated states could be distinguished through single molecule induced characteristic current fluctuation. More importantly, our results reveal that the neurotoxic Aβ1-42 oligomer tends to adsorb onto the solid surface of nanopores, which may explain its instability and highly neurotoxic features. This journal is © The Royal Society of Chemistry 2019.
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