No abstract

Ultralong organic phosphorescence (UOP) based on metal-free porous materials is rarely reported owing to rapid nonradiative transition under ambient conditions. In this study, hydrogen-bonded organic aromatic frameworks (HOAFs) with different pore sizes were constructed through strong intralayer π-π interactions to enable ultralong phosphorescence in metal-free porous materials under ambient conditions for the first time. Impressively, yellow UOP with a lifetime of 79.8 ms observed for PhTCz-1 lasted for several seconds upon ceasing the excitation. For PhTCz-2 and PhTCz-3, on account of oxygen-dependent phosphorescence quenching, UOP could only be visualized in N , thus demonstrating the potential of phosphorescent porous materials for oxygen sensing. This result not only outlines a principle for the design of new HOFs with high thermal stability, but also expands the scope of metal-free luminescent materials with the property of UOP.

Background: Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels control electrical activity through tetramerization of an intracellular linker. Results: NMR shows that the apo-cAMP-binding domain (CBD) of HCN4 destabilizes the tetramer through steric clashes. Conclusion:The apo-HCN4 CBD structure is compatible with monomeric and dimeric but not with tetrameric HCN4. Significance: The proposed mechanism explains HCN auto-inhibition and its relaxation by cAMP.

A new (4,8)-connected Zr-MOF porous zirconium metal-organic framework (Zr-MOF) with flu topology, Zr6(μ3-O)4(μ3-OH)4(TCPS)2(H2O)4(OH)4 (, TCPS = tetrakis(4-carboxyphenyl) silane) with a BET specific area of 1402 m(2) g(-1) has been constructed and fully characterized. is stable in air and acid media but unstable in water and basic media, and thermally stable up to 200 °C. The new MOF is a wide band gap semiconductor with Eg = 3.95 eV. The excitation of at 260 nm gives a ligand-based emission peak at 435 nm. After solvent exchange processes and activation at 200 °C, this MOF exhibits high storage capacities for H2, CH4 and CO2. We summarized the hydrothermal stability data of Zr-MOFs, calculated the NBO (natural bond orbital) charges of the coordinating oxygen atoms of the corresponding carboxylate ligands and analyzed the influencing factors. Besides the known reasons of hydrothermal stabilities of Zr-MOFs, we demonstrated that NBO charges of coordinating atoms of the ligands can be used to explain the hydrothermal stabilities of Zr-MOFs.

Ultralong organic phosphorescence (UOP) based on metal‐free porous materials is rarely reported owing to rapid nonradiative transition under ambient conditions. In this study, hydrogen‐bonded organic aromatic frameworks (HOAFs) with different pore sizes were constructed through strong intralayer π–π interactions to enable ultralong phosphorescence in metal‐free porous materials under ambient conditions for the first time. Impressively, yellow UOP with a lifetime of 79.8 ms observed for PhTCz‐1 lasted for several seconds upon ceasing the excitation. For PhTCz‐2 and PhTCz‐3, on account of oxygen‐dependent phosphorescence quenching, UOP could only be visualized in N2, thus demonstrating the potential of phosphorescent porous materials for oxygen sensing. This result not only outlines a principle for the design of new HOFs with high thermal stability, but also expands the scope of metal‐free luminescent materials with the property of UOP.

Two-in-one bending properties were achieved by a crystal engineering strategy of introducing a spring-like backbone in the structure.

Transformation of a dense metal–organic framework (MOF) to a highly porous form can radically improve its applications in drug loading. In this study, an environmentally friendly synthesis of potassium acetate γ-cyclodextrin metal–organic framework (γ-CD-MOF) in water was identified as a dense crystal form. Importantly, the molecular arrangement of the dense γ-CD-MOF was confirmed by single crystal X-ray diffraction and other characterizations. If the dense γ-CD-MOF was directly dried after separation from the mother solution, it is incapable of loading a model drug. However, the fresh dense crystal could be transformed into a highly porous form by introducing ethanol. The crystal transformation was demonstrated by enhanced drug loading capability and characterizations of powder X-ray diffraction (PXRD), small-angle X-ray scattering (SAXS), and the N2 adsorption isotherm. In all, the crystal transformation from dense to highly porous form could significantly facilitate the applications of γ-CD-MOFs in drug loading and other potential fields.

We report advances in the calculation of protein structures from chemical shift nuclear magnetic resonance data alone. Our previously developed method, CS-Rosetta, assembles structures from a library of short protein fragments picked from a large library of protein structures using chemical shifts and sequence information. Here we demonstrate that combination of a new and improved fragment picker and the iterative sampling algorithm RASREC yield significant improvements in convergence and accuracy. Moreover, we introduce improved criteria for assessing the accuracy of the models produced by the method. The method was tested on 39 proteins in the 50-100 residue size range and yields reliable structures in 70 % of the cases. All structures that passed the reliability filter were accurate (<2 Å RMSD from the reference).