2,648 research outputs found

    Trimethylsilyl tag for probing protein-ligand interactions by NMR

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    Protein-ligand titrations can readily be monitored with a trimethylsilyl (TMS) tag. Owing to the intensity, narrow line shape and unique chemical shift of a TMS group, dissociation constants can be determined from straightforward 1D 1H-NMR spectra not only in the fast but also in the slow exchange limit. The tag is easily attached to cysteine residues and a sensitive reporter of ligand binding also at sites where it does not interfere with ligand binding or catalytic efficiency of the target protein. Its utility is demonstrated for the Zika virus NS2B-NS3 protease and the human prolyl isomerase FK506 binding protein.C.N. and G.O. thank the Alexander von Humboldt Foundation for a Feodor Lynen Fellowship and the Australian Research Council for a Laureate Fellowship, respectively. Financial project support by the Australian Research Council, the Austrian Science Fund (FWF) (DK Molecular Enzymology W901 to K.Z.) and by NAWI Graz is gratefully acknowledged

    Electrically Conductive Photoluminescent Porphyrin Phosphonate Metal-Organic Frameworks

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    Herein, the design and synthesis of a highly photoluminescent and electrically conductive metal–organic framework [Zn{Cu-p-H6TPPA}]⋅2 [(CH3)2NH] (designated as GTUB3), which is constructed using the 5,10,15,20-tetrakis [p-phenylphosphonic acid] porphyrin (p-H8TPPA) organic linker, is reported. The bandgap of GTUB3 is measured to be 1.45 and 1.48 eV using diffuse reflectance spectroscopy and photoluminescence (PL) spectroscopy, respectively. The PL decay measurement yields a charge carrier lifetime of 40.6 ns. Impedance and DC measurements yield average electrical conductivities of 0.03 and 4 S m−1, respectively, making GTUB3 a rare example of an electrically conductive 3D metal–organic framework. Thermogravimetric analysis reveals that the organic components of GTUB3 are stable up to 400 °C. Finally, its specific surface area and pore volume are calculated to be 622 m2 g−1 and 0.43 cm3 g−1, respectively, using grand canonical Monte Carlo. Owing to its porosity and high electrical conductivity, GTUB3 may be used as a low-cost electrode material in next generation of supercapacitors, while its low bandgap and high photoluminescence make it a promising material for optoelectronic applications

    Incoherent electronic band states in Mn substituted BaFe2_{2}As2_{2}

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    Chemical substitution is commonly used to explore new ground states in materials, yet the role of disorder is often overlooked. In Mn-substituted BaFe2_{2}As2_{2} (MnBFA), superconductivity (SC) is absent, despite being observed for nominal hole-doped phases. Instead, a glassy magnetic phase emerges, associated with the S=5/2S=5/2 Mn local spins. In this work, we present a comprehensive investigation of the electronic structure of MnBFA using angle-resolved photoemission spectroscopy (ARPES). We find that Mn causes electron pockets to shrink, disrupting the nesting condition in MnBFA. Notably, we propose that electronic disorder, along with magnetic scattering, primarily contributes to suppressing the itinerant magnetic order in MnBFA. This finding connects the MnBFA electronic band structure properties to the glassy magnetic behavior observed in these materials and suggests that SC is absent because of the collective magnetic impurity behavior that scatters the Fe-derived excitations. Moreover, we suggest that Mn tunes MnBFA to a phase in between the correlated metal in BaFe2_{2}As2_{2} and the Hund insulator phase in BaMn2_{2}As2_{2}.Comment: main 7 pages, 3 figures + supp 5 pages, 5 figure

    AN ULTRA-FAINT GALAXY CANDIDATE DISCOVERED in EARLY DATA from the MAGELLANIC SATELLITES SURVEY

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    We report a new ultra-faint stellar system found in Dark Energy Camera data from the first observing run of the Magellanic Satellites Survey (MagLiteS). MagLiteS J0644-5953 (Pictor II or Pic II) is a low surface brightness (μ = 28.5+1 -1 mag arcsec-2 within its half-light radius) resolved overdensity of old and metal-poor stars located at a heliocentric distance of 45+5 -4 kpc. The physical size (r1/2 = 46+15 -11) and low luminosity (Mv = -3.2+0.4 -0.5 mag) of this satellite are consistent with the locus of spectroscopically confirmed ultra-faint galaxies. MagLiteS J0644-5953 (Pic II) is located 11.3+3.1 -0.9 kpc from the Large Magellanic Cloud (LMC), and comparisons with simulation results in the literature suggest that this satellite was likely accreted with the LMC. The close proximity of MagLiteS J0644-5953 (Pic II) to the LMC also makes it the most likely ultra-faint galaxy candidate to still be gravitationally bound to the LMC.Peer reviewe
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