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81.
We report excellent reactivity and enantioselectivity of a C(2)-symmetric copper-bound N-heterocyclic carbene (NHC) in the hydrosilylation of a variety of structurally diverse ketones. This catalyst exhibits extraordinary enantioselctivity in the reduction of such challenging substrates as 2-butanone and 3-hexanone. Even at low catalyst loading (2.0 mol %), the reactions occur in under an hour at room temperature and often do not require purification beyond catalyst and solvent removal. The scope of this transformation was investigated in the reduction of 10 aryl-alkyl and alkyl-alkyl ketones. 相似文献
82.
David J. Lunn Sungbaek Seo Sang‐Ho Lee Raghida Bou Zerdan Kaila M. Mattson Nicolas J. Treat Alaina J. McGrath Will R. Gutekunst Jimmy Lawrence Allison Abdilla Athina Anastasaki Abigail S. Knight Bernhard V. K. J. Schmidt Morgan W. Bates Paul G. Clark Jonathan P. DeRocher Antony K. Van Dyk Craig J. Hawker 《Journal of polymer science. Part A, Polymer chemistry》2019,57(6):716-725
The synthesis and systematic comparison of a comprehensive library of well‐defined polymer architectures based on poly(acrylic acid) is reported. Through the development of new synthetic methodologies, linear, single branched, precision‐branched comb, and star polymers were prepared and their performance as dispersants was evaluated. The ability to accurately control chain lengths and branch points allows the subtle interplay between structure and dispersant performance to be defined and affords critical insights into the design of improved polymeric additives for coating formulations. The general industrial relevance of ionic polymers and branched macromolecular architectures supports these design rules for a wide range of other applications and materials, including as additives for personal care products and in water treatment. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 716–725 相似文献
83.
Budi Riza Putra Luthando Tshwenya Mark A. Buckingham Jingyuan Chen Koichi Jeremiah Aoki Klaus Mathwig Omotayo A. Arotiba Abigail K. Thompson Zhongkai Li Frank Marken 《Electroanalysis》2021,33(6):1398-1418
Ionic rectifier membranes or devices generate uni-directional ion transport to convert an alternating current (AC) ion current input into stored energy or direct current (DC) in the form of ion/salt gradients. Electrochemical experiments 80 years ago were conducted on biological membrane rectifier systems, but today a plethora of artificial ionic rectifier types has been developed and electroanalytical tools are employed to explore mechanisms and performance. This overview focuses on microscale ionic rectifiers with a comparison to nano- and macroscale ionic rectifiers. The potential is surveyed for applications in electrochemical analysis, desalination, energy harvesting, electrochemical synthesis, and in selective ion extraction. 相似文献
84.
Dr. Matthew R. Bennett Dr. Mark L. Thompson Dr. Sarah A. Shepherd Dr. Mark S. Dunstan Abigail J. Herbert Dr. Duncan R. M. Smith Victoria A. Cronin Dr. Binuraj R. K. Menon Dr. Colin Levy Prof. Jason Micklefield 《Angewandte Chemie (International ed. in English)》2018,57(33):10600-10604
Benzylisoquinoline alkaloids (BIAs) are a structurally diverse family of plant secondary metabolites, which have been exploited to develop analgesics, antibiotics, antitumor agents, and other therapeutic agents. Biosynthesis of BIAs proceeds via a common pathway from tyrosine to (S)‐reticulene at which point the pathway diverges. Coclaurine N‐methyltransferase (CNMT) is a key enzyme in the pathway to (S)‐reticulene, installing the N‐methyl substituent that is essential for the bioactivity of many BIAs. In this paper, we describe the first crystal structure of CNMT which, along with mutagenesis studies, defines the enzymes active site architecture. The specificity of CNMT was also explored with a range of natural and synthetic substrates as well as co‐factor analogues. Knowledge from this study could be used to generate improved CNMT variants required to produce BIAs or synthetic derivatives. 相似文献
85.
86.
Abigail Rendos Ran Li Stephanie Woodman Prof. Xi Ling Prof. Keith A. Brown 《Chemphyschem》2021,22(5):435-440
Magnetorheological fluids (MRF) are suspensions of magnetic particles that solidify in the presence of a magnetic field. While non-magnetic additives could improve MRF performance, explorations into such additives have not coalesced into an understanding of their influence, and particularly the role of additive morphology. Here, we explore α-Ni(OH)2 2D sheets, with aspect ratios of ∼25,000, as highly anisotropic MRF additives. Experiments studying pressure-driven flow of an MRF with and without these sheets show that their addition can increase the saturation pressure by as much as 46 %. However, shear-mode rheology reveals that they can also weaken the MRF by inhibiting the chaining of the iron particles at low field strengths and have no effect at higher field strengths. In order to reconcile the strikingly different results, we propose that 2D materials introduce a non-Newtonian handle to modify smart fluids in a manner that depends on the curvature of the shearing strain rate profile. Specifically, we identify a modification to the Buckingham-Reiner model of pressure-driven flow for a Bingham plastic in which the sheets widen the solidified plug. This work highlights the subtle interaction between particles in smart fluids and flows while emphasizing the opportunity for using anisotropy to tune this interaction. 相似文献
87.
Cadmium poisoning poses a serious health concern due to cadmium''s increasing industrial use, yet there is currently no recommended treatment. The selective coordination of cadmium in a biological environment—i.e. in the presence of serum ions, small molecules, and proteins—is a difficult task. To address this challenge, a combinatorial library of peptoid-based ligands has been evaluated to identify structures that selectively bind to cadmium in human serum with minimal chelation of essential metal ions. Eighteen unique ligands were identified in this screening procedure, and the binding affinity of each was measured using metal titrations monitored by UV-vis spectroscopy. To evaluate the significance of each chelating moiety, sequence rearrangements and substitutions were examined. Analysis of a metal–ligand complex by NMR spectroscopy highlighted the importance of particular residues. Depletion experiments were performed in serum mimetics and human serum with exogenously added cadmium. These depletion experiments were used to compare and demonstrate the ability of these peptoids to remove cadmium from blood-like mixtures. In one of these depletion experiments, the peptoid sequence was able to deplete the cadmium to a level comparable to the reported acute toxicity limit. Evaluation of the metal selectivity in buffered solution and in human serum was performed to verify minimal off-target binding. These studies highlight a screening platform for the identification of metal–ligands that are capable of binding in a complex environment. They additionally demonstrate the potential utility of biologically-compatible ligands for the treatment of heavy metal poisoning. 相似文献
88.
Abigail Pulsipher Matthew E. Griffin Shannon E. Stone Prof. Linda C. Hsieh‐Wilson 《Angewandte Chemie (International ed. in English)》2015,54(5):1466-1470
Glycans mediate many critical, long‐term biological processes, such as stem cell differentiation. However, few methods are available for the sustained remodeling of cells with specific glycan structures. A new strategy that enables the long‐lived presentation of defined glycosaminoglycans on cell surfaces using HaloTag proteins (HTPs) as anchors is reported. By controlling the sulfation patterns of heparan sulfate (HS) on pluripotent embryonic stem cell (ESC) membranes, it is demonstrated that specific glycans cause ESCs to undergo accelerated exit from self‐renewal and differentiation into neuronal cell types. Thus, the stable display of glycans on HTP scaffolds provides a powerful, versatile means to direct key signaling events and biological outcomes such as stem cell fate. 相似文献
89.
Abigail J. Herbert Sarah A. Shepherd Victoria A. Cronin Matthew R. Bennett Rehana Sung Jason Micklefield 《Angewandte Chemie (International ed. in English)》2020,59(35):14950-14956
S‐adenosyl‐l ‐methionine (SAM)‐dependent methyltransferases (MTs) catalyse the methylation of a vast array of small metabolites and biomacromolecules. Recently, rare carboxymethylation pathways have been discovered, including carboxymethyltransferase enzymes that utilise a carboxy‐SAM (cxSAM) cofactor generated from SAM by a cxSAM synthase (CmoA). We show how MT enzymes can utilise cxSAM to catalyse carboxymethylation of tetrahydroisoquinoline (THIQ) and catechol substrates. Site‐directed mutagenesis was used to create orthogonal MTs possessing improved catalytic activity and selectivity for cxSAM, with subsequent coupling to CmoA resulting in more efficient and selective carboxymethylation. An enzymatic approach was also developed to generate a previously undescribed co‐factor, carboxy‐S‐adenosyl‐l ‐ethionine (cxSAE), thereby enabling the stereoselective transfer of a chiral 1‐carboxyethyl group to the substrate. 相似文献
90.
Víctor Martínez-Rosas Beatriz Hernndez-Ochoa Gabriel Navarrete-Vzquez Carlos Martínez-Conde Fernando Gmez-Chvez Laura Morales-Luna Abigail Gonzlez-Valdez Roberto Arreguin-Espinosa Sergio Enríquez-Flores Vernica Prez de la Cruz Rodrigo Aguayo-Ortiz Carlos Wong-Baeza Isabel Baeza-Ramírez Saúl Gmez-Manzo 《Molecules (Basel, Switzerland)》2022,27(4)
Trichomoniasis is a sexually transmitted disease with a high incidence worldwide, affecting 270 million people. Despite the existence of a catalog of available drugs to combat this infection, their extensive use promotes the appearance of resistant Trichomonas vaginalis (T. vaginalis), and some side effects in treated people, which are reasons why it is necessary to find new alternatives to combat this infection. In this study, we investigated the impact of an in-house library comprising 55 compounds on the activity of the fused T. vaginalis G6PD::6PGL (TvG6PD::6PGL) protein, a protein mediating the first reaction step of the pentose phosphate pathway (PPP), a crucial pathway involved in the parasite’s energy production. We found four compounds: JMM-3, CNZ-3, CNZ-17, and MCC-7, which inhibited the TvG6PD::6PGL protein by more than 50%. Furthermore, we determined the IC50, the inactivation constants, and the type of inhibition. Our results showed that these inhibitors induced catalytic function loss of the TvG6PD::6PGL enzyme by altering its secondary and tertiary structures. Finally, molecular docking was performed for the best inhibitors, JMM-3 and MCC-7. All our findings demonstrate the potential role of these selected hit compounds as TvG6PD::6PGL enzyme selective inhibitors. 相似文献