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Tethering complex

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https://www.readbyqxmd.com/read/28224145/axially-chiral-racemic-half-sandwich-nickel-ii-complexes-by-ring-closing-metathesis
#1
Włodzimierz Buchowicz, Łukasz Banach, Radosław Kamiński, Piotr Buchalski
A remarkable nickelacycle has been synthesised via olefin metathesis of the α,ω-diene complex [Ni(η(5)-C5H4R)(Br)(NHC)] (R = C(CH3)2CH2CH[double bond, length as m-dash]CH2, NHC = 1-(6-hexenyl)-3-(2,4,6-trimethylphenyl)-imidazol-2-ylidene). Single-crystal X-ray analysis reveals a helical shape of the molecule and stretching of some interatomic distances in the Ni(ii) coordination sphere. The Cp-NHC tethered complex shows catalytic activity resembling that of the parent complexes.
February 22, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28223520/membrane-integration-of-an-essential-%C3%AE-barrel-protein-prerequires-burial-of-an-extracellular-loop
#2
Joseph S Wzorek, James Lee, David Tomasek, Christine L Hagan, Daniel E Kahne
The Bam complex assembles β-barrel proteins into the outer membrane (OM) of Gram-negative bacteria. These proteins comprise cylindrical β-sheets with long extracellular loops and create pores to allow passage of nutrients and waste products across the membrane. Despite their functional importance, several questions remain about how these proteins are assembled into the OM after their synthesis in the cytoplasm and secretion across the inner membrane. To understand this process better, we studied the assembly of an essential β-barrel substrate for the Bam complex, BamA...
February 21, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28218747/mhc-i-peptides-get-out-of-the-groove-and-enable-a-novel-mechanism-of-hiv-1-escape
#3
Phillip Pymm, Patricia T Illing, Sri H Ramarathinam, Geraldine M O'Connor, Victoria A Hughes, Corinne Hitchen, David A Price, Bosco K Ho, Daniel W McVicar, Andrew G Brooks, Anthony W Purcell, Jamie Rossjohn, Julian P Vivian
Major histocompatibility complex class I (MHC-I) molecules play a crucial role in immunity by capturing peptides for presentation to T cells and natural killer (NK) cells. The peptide termini are tethered within the MHC-I antigen-binding groove, but it is unknown whether other presentation modes occur. Here we show that 20% of the HLA-B*57:01 peptide repertoire comprises N-terminally extended sets characterized by a common motif at position 1 (P1) to P2. Structures of HLA-B*57:01 presenting N-terminally extended peptides, including the immunodominant HIV-1 Gag epitope TW10 (TSTLQEQIGW), showed that the N terminus protrudes from the peptide-binding groove...
February 20, 2017: Nature Structural & Molecular Biology
https://www.readbyqxmd.com/read/28218430/stepwise-assembly-of-functional-c-terminal-rest-nrsf-transcriptional-repressor-complexes-as-a-drug-target
#4
Ken Inui, Zongpei Zhao, Juan Yuan, Sakthidasan Jayaprakash, Le T M Le, Srdja Drakulic, Bjoern Sander, Monika M Golas
In human cells, thousands of predominantly neuronal genes are regulated by the repressor element 1 (RE1)-silencing transcription factor/neuron-restrictive silencer factor (REST/NRSF). REST/NRSF represses transcription of these genes in stem cells and non-neuronal cells by tethering corepressor complexes. Aberrant REST/NRSF expression and intracellular localization are associated with cancer and neurodegeneration in humans. To date, detailed molecular analyses of REST/NRSF and its C-terminal repressor complex have been hampered largely by the lack of sufficient amounts of purified REST/NRSF and its complexes...
February 20, 2017: Protein Science: a Publication of the Protein Society
https://www.readbyqxmd.com/read/28211208/one-pot-assembly-of-amino-acid-bridged-hybrid-macromulticyclic-cages-through-multiple-multicomponent-macrocyclizations
#5
Ludger A Wessjohann, Oliver Kreye, Daniel G Rivera
An important development in the field of macrocyclization strategies towards molecular cages is described. The approach comprises the utilization of a double Ugi four-component macrocyclization for the assembly of macromulticycles with up to four different tethers, that is, hybrid cages. The innovation of this method rests on setting up the macromulticycle connectivities not through the tethers but through the bridgeheads, which in this case involve N-substituted amino acids. Both dilution and metal-template-driven macrocyclization conditions were implemented with success, enabling the one-pot formation of cryptands and cages including steroidal, polyether, heterocyclic, peptidic, and aryl tethers...
February 17, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28210885/cohesin-biology-meets-the-loop-extrusion-model
#6
REVIEW
Christopher Barrington, Ronald Finn, Suzana Hadjur
Extensive research has revealed that cohesin acts as a topological device, trapping chromosomal DNA within a large tripartite ring. In so doing, cohesin contributes to the formation of compact and organized genomes. How exactly the cohesin subunits interact, how it opens, closes, and translocates on chromatin, and how it actually tethers DNA strands together are still being elucidated. A comprehensive understanding of these questions will shed light on how cohesin performs its many functions, including its recently proposed role as a chromatid loop extruder...
February 16, 2017: Chromosome Research
https://www.readbyqxmd.com/read/28208340/scaling-features-of-the-tribology-of-polymer-brushes-of-increasing-grafting-density-around-the-mushroom-to-brush-transition
#7
E Mayoral, J Klapp, A Gama Goicochea
Nonequilibrium coarse-grained, dissipative particle dynamics simulations of complex fluids, made up of polymer brushes tethered to planar surfaces immersed in a solvent yield nonmonotonic behavior of the friction coefficient as a function of the polymer grating density on the substrates, Γ, while the viscosity shows a monotonically increasing dependence on Γ. This effect is shown to be independent of the degree of polymerization, N, and the size of the system. It arises from the composition and the structure of the first particle layer adjacent to each surface that results from the confinement of the fluid...
January 2017: Physical Review. E
https://www.readbyqxmd.com/read/28207952/di-nickel-salphen-complexes-as-binders-of-human-telomeric-dimeric-g-quadruplexes
#8
Ramon Vilar, Chun-Qiong Zhou, Ting-Cong Liao, Zi-Qi Li, Jorge Gonzalez-Garcia, Matthew Reynolds, Min Zou
Three new polyether-tethered di-nickel-salphen complexes (2a-c) have been synthesized and fully characterized by NMR spectroscopy, mass spectrometry and elemental analyses. The binding affinity and selectivity of these complexes and of the parent mono-nickel complex (1) towards dimeric quadruplex DNA have been determined by UV-Vis titrations, fluorescence spectroscopy, CD spectroscopy and electrophoresis. These studies have shown that the di-nickel-salphen complex with the longest polyether linker (2c) has higher binding affinity and selectivity towards dimeric quadruplexes (over monomeric quadruplexes) than the di-nickel-salphen complexes with the shorter polyether linkers (2a and 2b)...
February 16, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28194453/a-paper-based-platform-for-detection-of-viral-rna
#9
Daohong Zhang, David Broyles, Eric A Hunt, Emre Dikici, Sylvia Daunert, Sapna K Deo
Viral detection presents a host of challenges for even the most sensitive analytical techniques, and the complexity of common detection platforms typically preclude portability. With these considerations in mind, we designed a paper microzone plate-based virus detection system for the detection of viral genetic material that can be performed with simple instruments. The sensing system can detect viral cDNA reverse-transcribed from total RNA extraction by utilizing a biotinylated capture probe and an Alexa Fluor® 647-labeled reporter probe...
February 14, 2017: Analyst
https://www.readbyqxmd.com/read/28191742/a-tethered-ru-s-complex-with-an-axial-chiral-thiolate-ligand-for-cooperative-si-h-bond-activation-application-to-enantioselective-imine-reduction
#10
Simon Wübbolt, Modhu Sudan Maji, Elisabeth Irran, Martin Oestreich
An axial chiral version of the 2,6-dimesitylphenyl group attached to sulfur is reported. Its multistep preparation starts from (S)-binol, and the thiol group is established by a racemization-free thermal Newman-Kwart rearrangement. The new chiral thiolate ligand decorated with one mesityl group is used in the synthesis of a tethered ruthenium chloride complex. Its spectroscopic characterization revealed solvent-dependent epimerization at the ruthenium center. The major diastereomer is crystallographically characterized...
February 13, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28191741/intermediates-stabilized-by-tris-triazolylmethyl-amines-in-cuaac-reaction
#11
Haoqing Chen, Chengzhi Cai, Siheng Li, Yong Ma, Sijin Luozhong, Zhiling Zhu
Tris(triazolylmethyl)amine ligands (TL) are widely used to accelerate the CuI-catalyzed azide-alkyne cycloaddition (CuAAC) reaction, but its mechanistic role remains unclear. Using electro-spray ionization mass spectrometry, for the first time we detected the trinuclear TL-CuI3-acetylide and the dinuclear TL-CuI2-acetylide complexes in aqueous solution. The apparent second-order rate constants of their reaction with an azide were 27 M-1*s-1 and 783 M-1*s-1 when the alkyne was tethered to the TL. In the catalytic system without the tether, the rate constant increased to >146 M-1*s-1 for the TL-CuI3-acetylide, but dropped by ~14 times to ~55 M-1*s-1 for the TL-CuI2-acetylide...
February 13, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28190898/synthesis-and-opioid-receptor-binding-of-indium-iii-and-111-in-labeled-macrocyclic-conjugates-of-diprenorphine-novel-ligands-designed-for-imaging-studies-of-peripheral-opioid-receptors
#12
Shefali Srivastava, Emily A Fergason-Cantrell, Roger I Nahas, John R Lever
Radiolabeled diprenorphine (DPN) and analogs are widely used ligands for non-invasive brain imaging of opioid receptors. To develop complementary radioligands optimized for studies of the peripheral opioid receptors, we prepared a pair of hydrophilic DPN derivatives, conjugated to the macrocyclic chelator DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid), for complexation with trivalent metals. The non-radioactive indium (III) complexes, tethered to the C6-oxygen position of the DPN scaffold by 6- to 9-atom spacers, displayed high affinities for binding to μ, δ and κ opioid receptors in vitro...
October 6, 2016: Tetrahedron
https://www.readbyqxmd.com/read/28185867/an-experimental-evaluation-of-the-role-of-the-stress-axis-in-mediating-predator-prey-interactions-in-wild-marine-fish
#13
Michael J Lawrence, Erika J Eliason, Jacob W Brownscombe, Kathleen M Gilmour, John W Mandelman, Steven J Cooke
The hypothalamic-pituitary-interrenal (HPI) axis, through corticosteroid secretion, is an integral mechanism regulating internal homeostasis when vertebrates are faced with a stressor. However, continued HPI-axis stimulation can produce homeostatic overload, where corticosteroids are detrimental to organismal function. This overload condition may play an important role in mediating predator-prey interactions, because chronically/previously stressed animals may have higher rates of predator-induced mortality...
February 7, 2017: Comparative Biochemistry and Physiology. Part A, Molecular & Integrative Physiology
https://www.readbyqxmd.com/read/28181801/optokinetically-encoded-nanoprobe-based-multiplexing-strategy-for-microrna-profiling
#14
Sungi Kim, Jeong-Eun Park, Woosung Hwang, Jinyoung Seo, Young-Kwang Lee, Jae-Ho Hwang, Jwa-Min Nam
Multiplexed real-time analysis on multiple interacting molecules and particles is needed to obtain information on binding patterns between multiple ligands and receptors, specificity of bond formations and interacting pairs in a complex medi-um, often found in chemical and biological systems, and difference in binding affinity and kinetics for different binding pairs in one solution. In particular, multiplexed profiling of microRNA (miRNA) in a reliable, quantitative manner is of great demand for the use of miRNA in cell biology, biosensing and clinical diagnostic applications, and accurate diagnosis of cancers with miRNA is not possible without detecting multiple miRNA sequences in a highly specific manner...
February 9, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28167697/prc2-is-dispensable-for-hotair-mediated-transcriptional-repression
#15
Manuela Portoso, Roberta Ragazzini, Živa Brenčič, Arianna Moiani, Audrey Michaud, Ivaylo Vassilev, Michel Wassef, Nicolas Servant, Bruno Sargueil, Raphaël Margueron
Long non-coding RNAs (lncRNAs) play diverse roles in physiological and pathological processes. Several lncRNAs have been suggested to modulate gene expression by guiding chromatin-modifying complexes to specific sites in the genome. However, besides the example of Xist, clear-cut evidence demonstrating this novel mode of regulation remains sparse. Here, we focus on HOTAIR, a lncRNA that is overexpressed in several tumor types and previously proposed to play a key role in gene silencing through direct recruitment of Polycomb Repressive Complex 2 (PRC2) to defined genomic loci...
February 6, 2017: EMBO Journal
https://www.readbyqxmd.com/read/28161574/covalent-growth-factor-tethering-to-direct-neural-stem-cell-differentiation-and-self-organization
#16
Trevor R Ham, Mahmoud Farrag, Nic D Leipzig
: Tethered growth factors offer exciting new possibilities for guiding stem cell behavior. However, many of the current methods present substantial drawbacks which can limit their application and confound results. In this work, we developed a new method for the site-specific covalent immobilization of azide-tagged growth factors and investigated its utility in a model system for guiding neural stem cell (NSC) behavior. An engineered interferon-γ (IFN-γ) fusion protein was tagged with an N-terminal azide group, and immobilized to two different dibenzocyclooctyne-functionalized biomimetic polysaccharides (chitosan and hyaluronan)...
February 2, 2017: Acta Biomaterialia
https://www.readbyqxmd.com/read/28160489/sec16-in-conventional-and-unconventional-exocytosis-working-at-the-interface-of-membrane-traffic-and-secretory-autophagy
#17
REVIEW
Bor Luen Tang
Sec16 is classically perceived to be a scaffolding protein localized to the transitional endoplasmic reticulum (tER) or the ER exit sites (ERES), and has a conserved function in facilitating coat protein II (COPII) complex-mediated ER exit. Recent findings have however pointed towards a role for Sec16 in unconventional exocytosis of certain membrane proteins, such as the Cystic fibrosis transmembrane conductance regulator (CFTR) in mammalian cells, and possibly also α-integrin in certain contexts of Drosophila development...
February 4, 2017: Journal of Cellular Physiology
https://www.readbyqxmd.com/read/28159613/the-vaccinia-virus-dna-polymerase-and-its-processivity-factor
#18
REVIEW
Maciej W Czarnecki, Paula Traktman
Vaccinia virus is the prototypic poxvirus. The 192 kilobase double-stranded DNA viral genome encodes most if not all of the viral replication machinery. The vaccinia virus DNA polymerase is encoded by the E9L gene. Sequence analysis indicates that E9 is a member of the B family of replicative polymerases. The enzyme has both polymerase and 3'-5' exonuclease activities, both of which are essential to support viral replication. Genetic analysis of E9 has identified residues and motifs whose alteration can confer temperature-sensitivity, drug resistance (phosphonoacetic acid, aphidicolin, cytosine arabinsode, cidofovir) or altered fidelity...
February 1, 2017: Virus Research
https://www.readbyqxmd.com/read/28155083/the-long-zinc-finger-domain-of-prdm9-forms-a-highly-stable-and-long-lived-complex-with-its-dna-recognition-sequence
#19
Yasmin Striedner, Theresa Schwarz, Thomas Welte, Andreas Futschik, Ulrich Rant, Irene Tiemann-Boege
PR domain containing protein 9 (PRDM9) is a meiosis-specific, multi-domain protein that regulates the location of recombination hotspots by targeting its DNA recognition sequence for double-strand breaks (DSBs). PRDM9 specifically recognizes DNA via its tandem array of zinc fingers (ZnFs), epigenetically marks the local chromatin by its histone methyltransferase activity, and is an important tether that brings the DNA into contact with the recombination initiation machinery. A strong correlation between PRDM9-ZnF variants and specific DNA motifs at recombination hotspots has been reported; however, the binding specificity and kinetics of the ZnF domain are still obscure...
February 2, 2017: Chromosome Research
https://www.readbyqxmd.com/read/28154194/autophosphorylation-based-calcium-ca2-sensitivity-priming-and-ca2-calmodulin-inhibition-of-arabidopsis-thaliana-ca2-dependent-protein-kinase-28-cpk28
#20
Kyle W Bender, R Kevin Blackburn, Jacqueline Monaghan, Paul Derbyshire, Frank Lh Menke, Cyril Zipfel, Michael B Goshe, Raymond E Zielinski, Steven C Huber
Plant calcium (Ca(2+)) dependent protein kinases (CPKs) represent the primary Ca(2+)- dependent protein kinase activities in plant systems. CPKs are composed of a dual specificity (Ser/Thr and Tyr) kinase domain tethered to a Calmodulin-like domain (CLD) via an autoinhibitory junction (J). While regulation of CPKs by Ca(2+) has been extensively studied, the contribution of autophosphorylation in controlling CPK activity is less well understood. Furthermore, whether Calmodulin (CaM) contributes to CPK regulation, as is the case for Ca(2+)/CaM-dependent protein kinases (CaMKs) outside the plant lineage, remains an open question...
January 30, 2017: Journal of Biological Chemistry
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