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https://www.readbyqxmd.com/read/29780568/anisotropic-functionalization-of-upconversion-nanoparticles
#1
Wei Ren, Shihui Wen, Sherif Abdulkader Tawfik, Qian P Su, Gungun Lin, Lining A Ju, Michael J Ford, Harshad Ghodke, Antoine M van Oijen, Dayong Jin
Despite significant advances toward accurate tuning of the size and shape of colloidal nanoparticles, the precise control of the surface chemistry thereof remains a grand challenge. It is desirable to conjugate functional bio-molecules onto the selected facets of nanoparticles owing to the versatile capabilities rendered by the molecules. We report here facet-selective conjugation of DNA molecules onto upconversion nanoparticles via ligand competition reaction. Different binding strengths of phosphodiester bonds and phosphate groups on DNA and the surfactant molecules allow one to create heterogeneous bio-chemistry surface for upconversion nanoparticles...
May 14, 2018: Chemical Science
https://www.readbyqxmd.com/read/29780567/enantioselective-direct-mannich-type-reactions-of-2-benzylpyridine-n-oxides-catalyzed-by-chiral-bis-guanidino-iminophosphorane-organosuperbase
#2
Qiupeng Hu, Azusa Kondoh, Masahiro Terada
2-Benzylpyridine N-oxides possessing less acidic α-protons were utilized as pronucleophiles for the first time in enantioselective addition reactions under Brønsted base catalysis. A chiral bis(guanidino)iminophosphorane was able to overcome the inherent issue of low acidity of the pronucleophiles, establishing the diastereo- and enantioselective direct Mannich-type reaction with N -Boc imines. The control experiments indicated that the N-oxide moiety of the substrates played a critical role in achieving the high stereoselectivity...
May 14, 2018: Chemical Science
https://www.readbyqxmd.com/read/29780566/nontrigonal-constraint-enhances-1-2-addition-reactivity-of-phosphazenes
#3
Yi-Chun Lin, James C Gilhula, Alexander T Radosevich
The syntheses and 1,2-addition reactivities of nontrigonal phosphazenes supported by trianionic tricoordinating chelates of the type L3 P 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 Ndipp ( 3 : L3 = N[CHC( t Bu)O]2 3- ; 4 : L3 = N( o -NMeC6 H4 )2 3- ; dipp = 2,6-diisopropylphenyl) are reported...
May 14, 2018: Chemical Science
https://www.readbyqxmd.com/read/29780565/taming-a-monomeric-cu-%C3%AE-6-c-6-h-6-complex-with-silylene
#4
Nasrina Parvin, Shiv Pal, Jorge Echeverría, Santiago Alvarez, Shabana Khan
Previous theoretical and experimental endeavors suggested that [Cu(C6 H6 )]+ prefers the η1 /η2 mode over the η6 mode due to the augmented repulsion between the benzene ring and metal d-electrons. Nevertheless, the use of silylene as a neutral ligand has led to the isolation of the first monomeric copper cation, [{PhC(N t Bu)2 SiN(SiMe3 )2 }Cu(η6 -C6 H6 )]+ [SbF6 ]- ( 3 ), where a copper atom is bound to the benzene ring in an unsupported η6 fashion. However, the use of IPr (1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) in place of silylene results in the formation of [IPr·Cu(η2 -C6 H6 )]+ [SbF6 ]- ( 6 ), where the copper atom is bound to the benzene ring in the η2 mode...
May 14, 2018: Chemical Science
https://www.readbyqxmd.com/read/29780564/an-iridium-iii-iv-v-redox-series-featuring-a-terminal-imido-complex-with-triplet-ground-state
#5
Markus Kinauer, Martin Diefenbach, Heiko Bamberger, Serhiy Demeshko, Edward J Reijerse, Christian Volkmann, Christian Würtele, Joris van Slageren, Bas de Bruin, Max C Holthausen, Sven Schneider
The iridium(iii/iv/v) imido redox series [Ir(N t Bu){N(CHCHP t Bu2 )2 }]0/+/2+ was synthesized and examined spectroscopically, magnetically, crystallographically and computationally. The monocationic iridium(iv) imide exhibits an electronic doublet ground state with considerable 'imidyl' character as a result of covalent Ir-N t Bu bonding. Reduction gives the neutral imide [Ir(N t Bu){N(CHCHP t Bu2 )2 }] as the first example of an iridium complex with a triplet ground state. Its reactivity with respect to nitrene transfer to selected electrophiles (CO2 ) and nucleophiles (PMe3 ), respectively, is reported...
May 14, 2018: Chemical Science
https://www.readbyqxmd.com/read/29780563/chemical-structure-and-bonding-in-a-thorium-iii-aluminum-heterobimetallic-complex
#6
Alison B Altman, Alexandra C Brown, Guodong Rao, Trevor D Lohrey, R David Britt, Laurent Maron, Stefan G Minasian, David K Shuh, John Arnold
Thorium sits at a unique position on the periodic table. On one hand, there is little evidence that its 5f orbitals engage in bonding as they do in other early actinides; on the other hand, its chemistry is distinct from Lewis acidic transition metals. To gain insight into the underlying electronic structure of Th and develop trends across the actinide series, it is useful to study Th(iii) and Th(ii) systems with valence electrons that may engage in non-electrostatic metal-ligand interactions, although only a handful of such systems are known...
May 14, 2018: Chemical Science
https://www.readbyqxmd.com/read/29780562/kinetic-studies-on-strand-displacement-in-de-novo-designed-parallel-heterodimeric-coiled-coils
#7
Mike C Groth, W Mathis Rink, Nils F Meyer, Franziska Thomas
Among the protein folding motifs, which are accessible by de novo design, the parallel heterodimeric coiled coil is most frequently used in bioinspired applications and chemical biology in general. This is due to the straightforward sequence-to-structure relationships, which it has in common with all coiled-coil motifs, and the heterospecificity, which allows control of association. Whereas much focus was laid on designing orthogonal coiled coils, systematic studies on controlling association, for instance by strand displacement, are rare...
May 14, 2018: Chemical Science
https://www.readbyqxmd.com/read/29780561/triple-action-pt-iv-derivatives-of-cisplatin-a-new-class-of-potent-anticancer-agents-that-overcome-resistance
#8
Emanuele Petruzzella, Roman Sirota, Irene Solazzo, Valentina Gandin, Dan Gibson
A series of triple action Pt(iv) prodrugs was designed to test the hypothesis that multi-action compounds, where each bioactive moiety intervenes in several cellular processes, might be more effective than a single agent at killing cancer cells. In particular, "triple action" Pt(iv) derivatives of cisplatin, where the axial ligands are inhibitors of cyclooxygenase (COXi), histone deacetylase (HDACi) or pyruvate dehydrogenase kinase (PDKi) were developed. All compounds, ctc-[Pt(NH3 )2 (COXi)(PDKi)Cl2 ], ctc-[Pt(NH3 )2 (COXi)(HDACi)Cl2 ] and ctc-[Pt(NH3 )2 (HDACi)(PDKi)Cl2 ], where COXi = aspirin or ibuprofen, PDKi = dichloroacetate and HDACi = valproate or phenylbutyrate, were significantly more cytotoxic than cisplatin against all cell lines of an in-house panel of human cancer cells...
May 14, 2018: Chemical Science
https://www.readbyqxmd.com/read/29780560/counting-charges-on-membrane-bound-peptides
#9
Alicia C McGeachy, Emily R Caudill, Dongyue Liang, Qiang Cui, Joel A Pedersen, Franz M Geiger
Quantifying the number of charges on peptides bound to interfaces requires reliable estimates of (i) surface coverage and (ii) surface charge, both of which are notoriously difficult parameters to obtain, especially at solid/water interfaces. Here, we report the thermodynamics and electrostatics governing the interactions of l-lysine and l-arginine octamers (Lys8 and Arg8 ) with supported lipid bilayers prepared from a 9 : 1 mixture of 1,2-dimyristoyl- sn-glycero -3-phosphocholine (DMPC) and 1,2-dimyristoyl- sn -glycero-3-phospho-(1'-rac-glycerol) (sodium salt) (DMPG) from second harmonic generation (SHG) spectroscopy, quartz crystal microbalance with dissipation monitoring (QCM-D) and nanoplasmonic sensing (NPS) mass measurements, and atomistic simulations...
May 14, 2018: Chemical Science
https://www.readbyqxmd.com/read/29780559/spatially-resolved-acyl-transfer-on-surface-by-organo-catalytic-scanning-probe-nanolithography-o-cspl
#10
Julien Botton, Katharina Gratzer, Cyril François, Vincent Mesquita, Lionel Patrone, Teodor S Balaban, Sylvain Clair, Jean-Luc Parrain, Olivier Chuzel
Groundbreaking research done in the area of nanolithography makes it a versatile tool to produce nanopatterns for a broad range of chemical surface functionalization or physical modifications. We report for the first time an organocatalytic scanning probe nanolithography (o-cSPL) approach. Covalent binding of an organocatalyst on the apex of an atomic force microscope (AFM) tip gives way to a system that allows the formation of locally defined acylated-alcohol patterns on self-assembled monolayers (SAMs). With resolutions comparable to those of other cSPL methods, this first example of o-cSPL holds promise for future applications of bottom-up nanolithography set-ups employing this novel technique...
May 14, 2018: Chemical Science
https://www.readbyqxmd.com/read/29780558/long-lived-protein-expression-in-hydrogel-particles-towards-artificial-cells
#11
Xiaoyu Zhou, Han Wu, Miao Cui, Sze Nga Lai, Bo Zheng
Herein we report a new type of cell-mimic particle capable of long-lived protein expression. We constructed the cell-mimic particles by immobilizing the proteinaceous factors of the cell-free transcription and translation system on the polymer backbone of hydrogel particles and encapsulating the plasmid template and ribosome inside the hydrogel. With the continuous supply of nutrients and energy, the protein expression in the cell-mimic particles remained stable for at least 11 days. We achieved the regulation of protein expression in the cell-mimic particles by the usage of lac operon...
May 14, 2018: Chemical Science
https://www.readbyqxmd.com/read/29780557/pd-nanosheets-with-their-surface-coordinated-by-radioactive-iodide-as-a-high-performance-theranostic-nanoagent-for-orthotopic-hepatocellular-carcinoma-imaging-and-cancer-therapy
#12
Mei Chen, Zhide Guo, Qinghua Chen, Jingping Wei, Jingchao Li, Changrong Shi, Duo Xu, Dawang Zhou, Xianzhong Zhang, Nanfeng Zheng
Radiolabeled nanoparticles (NPs), taking advantage of nanotechnology and nuclear medicine, have shown attractive potential for cancer diagnosis and therapy. However, the high background signal in the liver and long-term toxic effects of radioisotopes caused by the nonselective accumulation of radiolabeled nanoparticles in organs have become the major challenges. Here, we report a pH-sensitive multifunctional theranostic platform with radiolabeled Pd nanosheets through a simple mixture of ultra-small Pd nanosheets and radioisotopes utilizing the strong adsorption of 131 I and 125 I on their surfaces (denoted as 131 I-Pd-PEG or 125 I-Pd-PEG)...
May 14, 2018: Chemical Science
https://www.readbyqxmd.com/read/29780556/integration-of-isothermal-amplification-with-quantum-dot-based-fluorescence-resonance-energy-transfer-for-simultaneous-detection-of-multiple-micrornas
#13
Juan Hu, Ming-Hao Liu, Chun-Yang Zhang
MicroRNAs (miRNAs) are small non-coding RNAs that regulate important physiological processes, and their dysregulation is associated with various human diseases. Simultaneous sensitive detection of multiple miRNAs may facilitate early clinical diagnosis. In this research, we demonstrate for the first time the integration of hyperbranched rolling circle amplification (HRCA) with quantum dot (QD)-based fluorescence resonance energy transfer (FRET) for the simultaneous detection of multiple microRNAs with a single-color QD as the donor and two fluorescent dyes as the acceptors...
May 14, 2018: Chemical Science
https://www.readbyqxmd.com/read/29780555/reversible-disassembly-of-metallasupramolecular-structures-mediated-by-a-metastable-state-photoacid
#14
Suzanne M Jansze, Giacomo Cecot, Kay Severin
The addition of a metastable-state photoacid to solutions containing metal-ligand assemblies renders the systems light responsive. Upon irradiation, proton transfer from the photoacid to the ligand is observed, resulting in disassembly of the metallasupramolecular structure. In the dark, the process is fully reversed. Light-induced switching was demonstrated for six different metal-ligand assemblies containing PdII , PtII or RuII complexes and bridging polypyridyl ligands. The methodology allows liberating guest molecules with light...
May 14, 2018: Chemical Science
https://www.readbyqxmd.com/read/29780554/mechanistic-perspective-and-functional-activity-of-insulin-in-amylin-aggregation
#15
Michal Baram, Sharon Gilead, Ehud Gazit, Yifat Miller
Insulin is a key regulatory polypeptide that is secreted from pancreatic β-cells and has several important effects on the synthesis of lipids, regulation of enzymatic activities, blood glucose levels and the prevention of hyperglycemia. Insulin was demonstrated to self-assemble into ordered amyloid fibrils upon repeated injections, although the possible biological significance of the supramolecular structures is enigmatic. Amylin is also an amyloidogenic polypeptide that is secreted from pancreatic β-cells and plays an important role in glycemic regulation preventing post-prandial spikes in blood glucose levels...
May 14, 2018: Chemical Science
https://www.readbyqxmd.com/read/29780553/reactivity-enhancement-of-a-diphosphene-by-reversible-n-heterocyclic-carbene-coordination
#16
Debabrata Dhara, Pankaj Kalita, Subhadip Mondal, Ramakirushnan Suriya Narayanan, Kaustubh R Mote, Volker Huch, Michael Zimmer, Cem B Yildiz, David Scheschkewitz, Vadapalli Chandrasekhar, Anukul Jana
Diphosphene TerMes P = PTerMes ( 1 ; TerMes = 2,6-Mes2 C6 H3 ; Mes = 2,4,6-Me3 C6 H2 ) and NHCMe4 2 (NHCMe4 = 1,3,4,5-tetramethylimidazol-2-ylidene) exist in an equilibrium mixture with the NHCMe4 -coordinated diphosphene 3 . While uncoordinated 1 is inert to hydrolysis, the NHC adduct 3 readily undergoes hydrolysis to afford a phosphino-substituted phosphine oxide with the liberation of NHCMe4 . On this basis, conditions suitable for the catalytic use of NHCMe4 were identified. Similarly, while the hydrogenation of free diphosphene 1 with H3 N·BH3 is very slow, 3 reacts instantaneously with H3 N·BH3 at room temperature to afford a dihydrodiphosphane...
May 14, 2018: Chemical Science
https://www.readbyqxmd.com/read/29780552/experiments-indicating-a-second-hydrogen-ordered-phase-of-ice-vi
#17
Tobias M Gasser, Alexander V Thoeny, Lucie J Plaga, Karsten W Köster, Martin Etter, Roland Böhmer, Thomas Loerting
In the last twelve years five new ice phases were experimentally prepared. Two of them are empty clathrate hydrates and three of them represent hydrogen ordered counterparts of previously known disordered ice phases. Here, we report on hydrogen ordering in ice VI samples produced by cooling at pressures up to 2.00 GPa. Based on results from calorimetry, dielectric relaxation spectroscopy, Raman spectroscopy, and powder X-ray diffraction the existence of a second hydrogen ordered polymorph related to ice VI is suggested...
May 14, 2018: Chemical Science
https://www.readbyqxmd.com/read/29780551/protein-surface-functionalisation-as-a-general-strategy-for-facilitating-biomimetic-mineralisation-of-zif-8
#18
Natasha K Maddigan, Andrew Tarzia, David M Huang, Christopher J Sumby, Stephen G Bell, Paolo Falcaro, Christian J Doonan
The durability of enzymes in harsh conditions can be enhanced by encapsulation within metal-organic frameworks (MOFs) via a process called biomimetic mineralisation. Herein we show that the surface charge and chemistry of a protein determines its ability to seed MOF growth. We demonstrate that chemical modification of amino acids on the protein surface is an effective method for systematically controlling biomimetic mineralisation by zeolitic imidazolate framework-8 (ZIF-8). Reaction of surface lysine residues with succinic (or acetic) anhydride facilitates biomimetic mineralisation by increasing the surface negative charge, whereas reaction of surface carboxylate moieties with ethylenediamine affords a more positively charged protein and hinders the process...
May 14, 2018: Chemical Science
https://www.readbyqxmd.com/read/29780550/c4-h-indole-functionalisation-precedent-and-prospects
#19
REVIEW
Jagadeesh Kalepu, Parthasarathy Gandeepan, Lutz Ackermann, Lukasz T Pilarski
C4-decorated indoles feature in a plethora of bioactive and functional compounds of importance to natural product synthesis, material sciences, as well as crop protection and pharmaceutical industries. Traditionally, their syntheses largely involved harsh stoichiometric metalations and radical reactions. However, transition metal catalysed C-H activation has recently evolved into a powerful strategy for the late-stage diversification of indoles at the C4-H position. Modern photoredox, enzymatic and precious transition metal catalysis represent the key stimuli for developing challenging C-C and C-Het bond forming transformations under mild reaction conditions...
May 14, 2018: Chemical Science
https://www.readbyqxmd.com/read/29780549/a-thioether-directed-palladium-cleavable-linker-for-targeted-bioorthogonal-drug-decaging
#20
Benjamin J Stenton, Bruno L Oliveira, Maria J Matos, Laura Sinatra, Gonçalo J L Bernardes
We describe the development of a bifunctional linker that simultaneously allows site-specific protein modification and palladium-mediated bioorthogonal decaging. This was enabled by a thioether binding motif in the propargyl carbamate linker and a readily available palladium complex. We demonstrate the efficiency of this reaction by controlled drug release from a PEGylated doxorubicin prodrug in cancer cells. The linker can be easily installed into cysteine bearing proteins which we demonstrated for the construction of an anti-HER2 nanobody-drug conjugate...
May 7, 2018: Chemical Science
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