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New linkages for covalent organic frameworks (COFs) have been continuously pursued by chemists as they serve as the structure and property foundation for the materials. Developing new reaction types or modifying known linkages have been the only two methods to create new COF linkages. Herein, we report a novel strategy that uses H3PO3 as a bifunctional catalyst to achieve amine-linked COFs from readily available amine and aldehyde linkers. The acidic proton of H3PO3 catalyzes the imine framework formation, which is then in situ reduced to the amine COF by the reductive P-H moiety. The amine-linked COF outperforms its imine analogue in promoting Knoevenagel condensation because of the more basic sites and higher stability.

Membrane proteins and lipids coevolved to yield unique coregulatory mechanisms. Inward-rectifier K(+) (Kir) channels are often activated by anionic lipids endemic to their native membranes and require accessible water along their K(+) conductance pathway. To better understand Kir channel activation, we target multiple mutants of the Kir channel KirBac1.1 via solid-state nuclear magnetic resonance (SSNMR) spectroscopy, potassium efflux assays, and Förster resonance energy transfer (FRET) measurements. In the I131C stability mutant (SM), we observe an open-active channel in the presence of anionic lipids with greater activity upon addition of cardiolipin (CL). The introduction of three R to Q mutations (R49/151/153Q (triple Q mutant, TQ)) renders the protein inactive within the same activating lipid environment. Our SSNMR experiments reveal a stark reduction of lipid–protein interactions in the TQ mutant explaining the dramatic loss of channel activity. Water-edited SSNMR experiments further determined the TQ mutant possesses greater overall solvent exposure in comparison to wild-type but with reduced water accessibility along the ion conduction pathway, consistent with the closed state of the channel. These experiments also suggest water is proximal to the selectivity filter of KirBac1.1 in the open-activated state but that it may not directly enter the selectivity filter. Our findings suggest lipid binding initiates a concerted rotation of the cytoplasmic domain subunits, which is stabilized by multiple intersubunit salt bridges. This action buries ionic side chains away from the bulk water, while allowing water greater access to the K(+) conduction pathway. This work highlights universal membrane protein motifs, including lipid–protein interactions, domain rearrangement, and water-mediated diffusion mechanisms.

Solid-state nuclear magnetic resonance (SSNMR) is an NMR spectroscopy applied to condensed-phase systems, including membrane proteins. Membrane protein fold and function are dependent upon interactions with surrounding bilayer components. Structural and functional analyses are thus challenging, and new approaches are needed to better characterise these systems. SSNMR is uniquely suited to the examination of membrane proteins in native environments, and has the capabilities to elucidate complex protein mechanisms and structures. Notable research implementing SSNMR is aimed at developing new strategies and technology to efficiently target membrane proteins within synthetic and biological membranes. Significant advances have been made: observation of protein function in native environments, emergence of in situ methods to examine integral proteins within natural membranes, sensitivity enhancement techniques and cutting-edge structure determination methods. We present how these advances are applied to...

Methane dehydroaromatization is studied using different loadings (0.2 wt%, 0.6 and 1 wt%) of Co and Ni additives on a 6 wt% Mo/ZSM-5 catalyst to evaluate the promoting effect of Ni and Co on reactivity and stability of the catalysts. A synergy between Mo and the additives is observed when combining a reduction/carburization pretreatment with an optimum additive loading: benzene yield and catalytic stability are both improved. The fresh and spent samples were characterized by X-Ray Diffraction, 27Al Magic-Angle Spinning Solid State Nuclear Magnetic Resonance Spectroscopy, Temperature-Programmed Reduction and Thermogravimetric Analysis. The results suggest that catalytic enhancement in precarburized Mo-Co and Mo-Ni samples is due to a combination of effects: extraction of Al from the ZSM-5 framework to form inactive Al2(MoO4)3 is reduced, interaction of Mo with the additives enhances the retention of Mo species within the zeolite channels, prevents Mo aggregation in reaction and modifies the reducibility of the Mo sites.