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411.
Application of Fragment‐Based Screening to the Design of Inhibitors of Escherichia coli DsbA 下载免费PDF全文
Dr. Luke A. Adams Dr. Pooja Sharma Dr. Biswaranjan Mohanty Olga V. Ilyichova Dr. Mark D. Mulcair Dr. Martin L. Williams Ellen C. Gleeson Dr. Makrina Totsika Dr. Bradley C. Doak Dr. Sofia Caria Dr. Kieran Rimmer Dr. James Horne Dr. Stephen R. Shouldice Mansha Vazirani Dr. Stephen J. Headey Brent R. Plumb Prof. Jennifer L. Martin Dr. Begoña Heras Dr. Jamie S. Simpson Dr. Martin J. Scanlon 《Angewandte Chemie (International ed. in English)》2015,54(7):2179-2184
The thiol‐disulfide oxidoreductase enzyme DsbA catalyzes the formation of disulfide bonds in the periplasm of Gram‐negative bacteria. DsbA substrates include proteins involved in bacterial virulence. In the absence of DsbA, many of these proteins do not fold correctly, which renders the bacteria avirulent. Thus DsbA is a critical mediator of virulence and inhibitors may act as antivirulence agents. Biophysical screening has been employed to identify fragments that bind to DsbA from Escherichia coli. Elaboration of one of these fragments produced compounds that inhibit DsbA activity in vitro. In cell‐based assays, the compounds inhibit bacterial motility, but have no effect on growth in liquid culture, which is consistent with selective inhibition of DsbA. Crystal structures of inhibitors bound to DsbA indicate that they bind adjacent to the active site. Together, the data suggest that DsbA may be amenable to the development of novel antibacterial compounds that act by inhibiting bacterial virulence. 相似文献
412.
Single‐Molecule Magnetism,Enhanced Magnetocaloric Effect,and Toroidal Magnetic Moments in a Family of Ln4 Squares 下载免费PDF全文
Chinmoy Das Shefali Vaidya Tulika Gupta Jamie M. Frost Mattia Righi Prof. Dr. Euan K. Brechin Prof. Dr. Marco Affronte Prof. Dr. Gopalan Rajaraman Prof. Dr. Maheswaran Shanmugam 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(44):15639-15650
Three cationic [Ln4] squares (Ln=lanthanide) were isolated as single crystals and their structures solved as [Dy4(μ4‐OH)(HL)(H2L)3(H2O)4]Cl2?(CH3OH)4?(H2O)8 ( 1 ), [Tb4(μ4‐OH)(HL)(H2L)3(MeOH)4]Cl2?(CH3OH)4?(H2O)4 ( 2 ) and [Gd4(μ4‐OH)(HL)(H2L)3(H2O)2(MeOH)2]Br2?(CH3OH)4?(H2O)3 ( 3 ). The structures are described as hydroxo‐centered squares of lanthanide ions, with each edge of the square bridged by a doubly deprotonated H2L2? ligand. Alternating current magnetic susceptibility measurements show frequency‐dependent out‐of‐phase signals with two different thermally assisted relaxation processes for 1 , whereas no maxima in χM“ appears above 2.0 K for complex 2 . For 1 , the estimated effective energy barrier for these two relaxation processes is 29 and 100 K. Detailed ab initio studies reveal that complex 1 possesses a toroidal magnetic moment. The ab initio calculated anisotropies of the metal ions in complex 1 were employed to simulate the magnetic susceptibility by using the Lines model (POLY_ANISO) and this procedure yields J1=+0.01 and J2=?0.01 cm?1 for 1 as the two distinct exchange interactions between the DyIII ions. Similar parameters are also obtained for complex 1 (and 2 ) from specific heat measurements. A very weak antiferromagnetic super‐exchange interaction (J1=?0.043 cm?1 and g=1.99) is observed between the metal centers in 3 . The magnetocaloric effect (MCE) was estimated by using field‐dependent magnetization and temperature‐dependent heat‐capacity measurements. An excellent agreement is found for the ?ΔSm values extracted from these two measurements for all three complexes. As expected, 3 shows the largest ?ΔSm variation (23 J Kg?1 K?1) among the three complexes. The negligible magnetic anisotropy of Gd indeed ensures near degeneracy in the (2S+1) ground state microstates, and the weak super‐exchange interaction facilitates dense population of low‐lying excited states, all of which are likely to contribute to the MCE, making complex 3 an attractive candidate for cryogenic refrigeration. 相似文献
413.
Nicoleta Doriana Banu Ionut Banu Banu Marios S. Katsiotis Anjana Tharalekshmy Samuel Stephen Jamie Whelan Gisha Elizabeth Luckachan Radu Vladea Saeed M. Alhassan 《Chemical Papers》2016,70(11):1503-1511
Open cell 3D titanium carbide/silicon carbide (TiC/SiC) composite was oxidised to titanium oxide/silicon carbide (TiO2/SiC) following different temperature profiles in a thermal gravimetric analysis (TGA) instrument in continuous air-flow and static air (oven) environments. The TiC oxidation to anatase, starting at temperatures over 450°C, was confirmed by Raman spectroscopy and X-Ray diffraction (XRD). By increasing the temperature, the mass fraction of anatase diminished, while the mass fraction of rutile increased. SiC oxidation started at 650°C when a mixture of TiO2/SiO2/SiC could be observed by Raman, XRD and HRTEM. 相似文献
414.
The Importance of Vibronic Coupling for Efficient Reverse Intersystem Crossing in Thermally Activated Delayed Fluorescence Molecules 下载免费PDF全文
Factors influencing the rate of reverse intersystem crossing (krISC) in thermally activated delayed fluorescence (TADF) emitters are critical for improving the efficiency and performance of third‐generation heavy‐metal‐free organic light‐emitting diodes (OLEDs). However, present understanding of the TADF mechanism does not extend far beyond a thermal equilibrium between the lowest singlet and triplet states and consequently research has focused almost exclusively on the energy gap between these two states. Herein, we use a model spin‐vibronic Hamiltonian to reveal the crucial role of non‐Born‐Oppenheimer effects in determining krISC. We demonstrate that vibronic (nonadiabatic) coupling between the lowest local excitation triplet (3LE) and lowest charge transfer triplet (3CT) opens the possibility for significant second‐order coupling effects and increases krISC by about four orders of magnitude. Crucially, these simulations reveal the dynamical mechanism for highly efficient TADF and opens design routes that go beyond the Born‐Oppenheimer approximation for the future development of high‐performing systems. 相似文献
415.
Targeted Ultrasound‐Assisted Cancer‐Selective Chemical Labeling and Subsequent Cancer Imaging using Click Chemistry 下载免费PDF全文
Hua Wang Marianne Gauthier Jamie R. Kelly Rita J. Miller Ming Xu Prof. Dr. William D. O'Brien Jr. Prof. Dr. Jianjun Cheng 《Angewandte Chemie (International ed. in English)》2016,55(18):5452-5456
Metabolic sugar labeling followed by the use of reagent‐free click chemistry is an established technique for in vitro cell targeting. However, selective metabolic labeling of the target tissues in vivo remains a challenge to overcome, which has prohibited the use of this technique for targeted in vivo applications. Herein, we report the use of targeted ultrasound pulses to induce the release of tetraacetyl N‐azidoacetylmannosamine (Ac4ManAz) from microbubbles (MBs) and its metabolic expression in the cancer area. Ac4ManAz‐loaded MBs showed great stability under physiological conditions, but rapidly collapsed in the presence of tumor‐localized ultrasound pulses. The released Ac4ManAz from MBs was able to label 4T1 tumor cells with azido groups and significantly improved the tumor accumulation of dibenzocyclooctyne (DBCO)‐Cy5 by subsequent click chemistry. We demonstrated for the first time that Ac4ManAz‐loaded MBs coupled with the use of targeted ultrasound could be a simple but powerful tool for in vivo cancer‐selective labeling and targeted cancer therapies. 相似文献
416.
Dr. Joseph A. Wright Dr. Jamie N. T. Peck Dr. Stephen P. Cottrell Dr. Aušra Jablonskytė Dr. Vasily S. Oganesyan Prof. Christopher J. Pickett Dr. Upali A. Jayasooriya 《Angewandte Chemie (International ed. in English)》2016,55(47):14580-14583
The chemistry of metal hydrides is implicated in a range of catalytic processes at metal centers. Gaining insight into the formation of such sites by protonation and/or electronation is therefore of significant value in fully exploiting the potential of such systems. Here, we show that the muonium radical (Mu.), used as a low isotopic mass analogue of hydrogen, can be exploited to probe the early stages of hydride formation at metal centers. Mu. undergoes the same chemical reactions as H. and can be directly observed due to its short lifetime (in the microseconds) and unique breakdown signature. By implanting Mu. into three models of the [FeFe]‐hydrogenase active site we have been able to detect key muoniated intermediates of direct relevance to the hydride chemistry of these systems. 相似文献
417.
Jesse H. Hsu Cheyenne R. Peltier Megan Treichel Jamie C. Gaitor Qihao Li Renee Girbau Alexandra J. Macbeth Prof. Dr. Héctor D. Abruña Prof. Dr. Kevin J. T. Noonan Prof. Dr. Geoffrey W. Coates Prof. Dr. Brett P. Fors 《Angewandte Chemie (International ed. in English)》2023,62(30):e202304778
The limited number of methods to directly polymerize ionic monomers currently hinders rapid diversification and production of ionic polymeric materials, namely anion exchange membranes (AEMs) which are essential components in emerging alkaline fuel cell and electrolyzer technologies. Herein, we report a direct coordination-insertion polymerization of cationic monomers, providing the first direct synthesis of aliphatic polymers with high ion incorporations and allowing facile access to a broad range of materials. We demonstrate the utility of this method by rapidly generating a library of solution processable ionic polymers for use as AEMs. We investigate these materials to study the influence of cation identity on hydroxide conductivity and stability. We found that AEMs with piperidinium cations exhibited the highest performance, with high alkaline stability, hydroxide conductivity of 87 mS cm−1 at 80 °C, and a peak power density of 730 mW cm−2 when integrated into a fuel cell device. 相似文献
418.
Fast inactivation of the HERG potassium channel plays a critical role in normal cardiac function. Malfunction of these channels due to either genetic mutations or blockade by drugs leads to cardiac arrhythmias. An unusually long S5-P linker in the outer mouth of HERG is implicated in the fast inactivation mechanism. To examine the role of the S5-P linker in this inactivation mechanism, we study the permeation properties of the open and inactive states of a recent homology model of HERG. This model was constructed using the KcsA potassium channel as a template and contains specific conformations of the S5-P linker in the open and inactive states. We perform molecular dynamics simulations on the HERG model, followed by free energy, structural, and continuum electrostatics calculations. Our free energy calculations lead to selectivity results of the model channel (K+ over Na+) that are different in some respects from those of other potassium channels but consistent with experimental observations. Our structural results show that, in the inactive state, the S5-P linkers move closer to the channel axis, possibly causing a steric hindrance to permeating K+ ions. Our electrostatics calculations reveal, in the inactive state, an electrostatic potential energy barrier of approximately 14 kT at the extracellular pore entrance, again sufficient to stop K+ ion permeation through the pore. These results suggest that a steric and/or electrostatic plug mechanism contributes to inactivation in the HERG homology model. 相似文献
419.
Li G Dimitrijevic NM Chen L Nichols JM Rajh T Gray KA 《Journal of the American Chemical Society》2008,130(16):5402-5403
Highly photoactive, tetrahedral Ti4+ sites can be created, other than in zeolite cavities and on silica substrate, in mixed-phase TiO2 nanocomposites. The tetrahedral Ti4+ species was shown to be an intermediate formed during the thermally driven phase transformation from anatase to rutile. 相似文献
420.
This paper reports a two-component system in which molecular recognition rapidly leads to the formation of a homogeneous fibrillar gel that, over a period of hours, aggregates via fibre-fibre interactions to yield microcrystals--providing insight into the relationship between nanoscale gels and microscale crystals. 相似文献