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https://www.readbyqxmd.com/read/28078735/manganese-catalyzed-multicomponent-synthesis-of-pyrimidines-from-alcohols-and-amidines
#1
Nicklas Deibl, Rhett Kempe
The development of catalytic reactions for synthesizing different compounds from alcohols to save fossil carbon feedstock and reduce CO2 emissions is of high importance. Replacing rare noble metals with abundantly available 3d metals is equally important. We report a manganese-complex-catalyzed multicomponent synthesis of pyrimidines from amidines and up to three alcohols. Our reaction proceeds through condensation and dehydrogenation steps, permitting selective C-C and C-N bond formations. β-Alkylation reactions are used to multiply alkylate secondary alcohols with two different primary alcohols to synthesize fully substituted pyrimidines in a one-pot process...
January 12, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28078593/detection-of-s-acylated-cd95-by-acyl-biotin-exchange
#2
Aurelie Rossin, Anne-Odile Hueber
S-acylation is the covalent addition of a fatty acid, most generally palmitate onto cysteine residues of proteins through a labile thioester linkage. The death receptor CD95 is S-palmitoylated and this post-translational modification plays a crucial role on CD95 organization in cellular membranes and thus on CD95-mediated signaling. Here, we describe the nonradioactive detection of CD95 S-acylation by acyl-biotin exchange chemistry in which a biotin is substituted for the CD95-linked fatty acid. This sensitive technique, which depends on the ability of hydroxylamine to specifically cleave the thioester linkage between fatty acids and proteins, relies on three chemical steps: (1) blockage of free thiols of non-modified cysteine residues, (2) hydroxylamine-mediated cleavage of thioester-linked fatty acids to restore free thiols and (3) biotinylation of free thiols with a thiol reactive biotinylation agent...
2017: Methods in Molecular Biology
https://www.readbyqxmd.com/read/28077404/high-throughput-sequencing-of-the-t-cell-receptor-repertoire-pitfalls-and-opportunities
#3
James M Heather, Mazlina Ismail, Theres Oakes, Benny Chain
T-cell specificity is determined by the T-cell receptor, a heterodimeric protein coded for by an extremely diverse set of genes produced by imprecise somatic gene recombination. Massively parallel high-throughput sequencing allows millions of different T-cell receptor genes to be characterized from a single sample of blood or tissue. However, the extraordinary heterogeneity of the immune repertoire poses significant challenges for subsequent analysis of the data. We outline the major steps in processing of repertoire data, considering low-level processing of raw sequence files and high-level algorithms, which seek to extract biological or pathological information...
January 10, 2017: Briefings in Bioinformatics
https://www.readbyqxmd.com/read/28075577/reversible-unfolding-and-folding-of-the-metalloprotein-ferredoxin-revealed-by-single-molecule-atomic-force-microscopy
#4
Hai Lei, Yabin Guo, Xiaodong Hu, Chunguang Hu, Xiaotang Hu, Hongbin Li
Plant type [2Fe-2S] ferredoxins function primarily as electron transfer proteins in photosynthesis. Studying the unfolding-folding of ferredoxins in vitro is challenging, since the unfolding of ferredoxin is often irreversible due to the loss or disintegration of the iron-sulfur cluster. Additionally, the in vivo folding of holo-ferredoxin requires ferredoxin biogenesis proteins. Here we employed atomic force microscopy-based single molecule force microscopy and protein engineering techniques to directly study the mechanical unfolding and refolding of a plant type [2Fe-2S] ferredoxin from cyanobacteria Anabaena...
January 11, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28074206/synthesis-reactivity-and-characterization-of-pt-ii-complexes-with-n-n-chelating-ligands-structure-and-dimethylsulfoxide-reactivity-relationship
#5
Konstantinos Ypsilantis, Theodoros Tsolis, Andreas Kourtellaris, Manolis J Manos, John C Plakatouras, Achilleas Garoufis
Platinum(ii) complexes of the formula PtLCl2 [L = 2-(2'-pyridyl)quinoxaline, (pqx) (1), 2,(2'-pyridyl)benzo[g]quinoxaline, (pbqx) (3) and 2,(2'-pyridyl)quinoline, (pqn) (5)] were synthesized and characterized by spectroscopic and X-ray diffraction methods. Also, monodentate coordination of the ligands pqx and pbqx formed the complexes trans-Pt(DMSO)pqxCl2 (2) and trans-Pt(DMSO)pbqxCl2 (4) as it is indicated from X-ray crystal structure and NMR studies. The reaction of the complexes (1), (3) and (5) with DMSO-d6 revealed a ligand-release solvolysis, which was studied by means of NMR techniques...
January 11, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28071899/near-ir-absorbing-gold-nanoframes-with-enhanced-physiological-stability-and-improved-biocompatibility-for-in-vivo-biomedical-applications
#6
Liying Wang, Yunching Chen, Hsin Yao Lin, Yung-Te Hou, Ling-Chu Yang, Aileen Y Sun, Jia-Yu Liu, Chien-Wen Chang, Dehui Wan
This paper describes the synthesis of near-infrared (NIR)-absorbing gold nanoframes (GNFs) and a systematic study comparing their physiological stability and biocompatibility with those of hollow Au-Ag nanoshells (GNSs), which have been used widely as photothermal agents in biomedical applications because of their localized surface plasmon resonance (LSPR) in the NIR region. The GNFs were synthesized in three steps: galvanic replacement, Au deposition, and Ag dealloying, using silver nanospheres (SNP) as the starting material...
January 10, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28069233/a-facile-sonochemical-synthesis-of-shell-stabilized-reactive-microbubbles-using-surface-thiolated-bovine-serum-albumin-with-the-traut-s-reagent
#7
Xiaochen Ma, Adrien Bussonniere, Qingxia Liu
The short lifetime of proteinaceous microbubbles produced using conventional sonication method has hindered their applications in drug delivery and metal removal from wastewater. In this study, we aimed to synthesize stable proteinaceous microbubbles and to demonstrate their reactivity. Our model protein, bovine serum albumin (BSA) was treated with 2-iminothiolane hydrochloride (Traut's reagent) to convert primary amines to thiols before the synthesis of microbubbles. Microbubbles produced with the Traut's reagent-treated BSA (BSA-SH MBs) were initially concentrated at median sizes of 0...
May 2017: Ultrasonics Sonochemistry
https://www.readbyqxmd.com/read/28068671/high-spatial-resolution-mapping-of-catalytic-reactions-on-single-particles
#8
Chung-Yeh Wu, William J Wolf, Yehonatan Levartovsky, Hans A Bechtel, Michael C Martin, F Dean Toste, Elad Gross
The critical role in surface reactions and heterogeneous catalysis of metal atoms with low coordination numbers, such as found at atomic steps and surface defects, is firmly established. But despite the growing availability of tools that enable detailed in situ characterization, so far it has not been possible to document this role directly. Surface properties can be mapped with high spatial resolution, and catalytic conversion can be tracked with a clear chemical signature; however, the combination of the two, which would enable high-spatial-resolution detection of reactions on catalytic surfaces, has rarely been achieved...
January 11, 2017: Nature
https://www.readbyqxmd.com/read/28068066/gold-nanospheres-stabilized-indocyanine-green-as-a-synchronous-photodynamic-photothermal-therapy-platform-that-inhibits-tumor-growth-and-metastasis
#9
Wei Li, Hanbo Zhang, Xiaomeng Guo, Zuhua Wang, Fenfen Kong, Lihua Luo, Qingpo Li, Chunqi Zhu, Jie Yang, Yan Lou, Yong-Zhong Du, Jian You
Both photothermal therapy (PTT) and photodynamic therapy (PDT) are phototherapeutic approaches, which have been widely investigated for cancer therapy mediated by external light source. Here, a nanosystem presenting synchronous PTT and PDT effect realized through one-step near infrared (NIR) light irradiation is reported. This system was fabricated by conjugating indocyanine green (ICG) on hollow gold nanospheres (HAuNS) using branched-polyethylenimine (PEI, MW=10 kDa) as optimal linker, which provided a high ICG payload as well as a covering layer with suitable thickness on HAuNS to maintain ICG fluorescence and reactive oxygen species (ROS) productivity...
January 9, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28067933/mechanism-and-kinetics-of-the-electrocatalytic-reaction-responsible-for-the-high-cost-of-hydrogen-fuel-cells
#10
Tao Cheng, William A Goddard, Qi An, Hai Xiao, Boris Merinov, Sergey Morozov
The sluggish oxygen reduction reaction (ORR) is a major impediment to the economic use of hydrogen fuel cells in transportation. In this work, we report the full ORR reaction mechanism for Pt(111) based on Quantum Mechanics (QM) based Reactive metadynamics (RμD) simulations including explicit water to obtain free energy reaction barriers at 298 K. The lowest energy pathway for 4 e(-) water formation is: first, *OOH formation; second, *OOH reduction to H2O and O*; third, O* hydrolysis using surface water to produce two *OH and finally *OH hydration to water...
January 9, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28067928/near-infrared-light-mediated-enhancement-of-reactive-oxygen-species-generation-through-electron-transfer-from-graphene-oxide-to-iron-hydroxide-oxide
#11
Yue He, Andrea Del Valle, Yu Qian, Yu-Fen Huang
Clinical applications of current photodynamic therapy (PDT) agents are often restricted to be activated only by UV and visible light, which have very poor tissue penetration depths. In this study, a new near infrared (NIR)-absorbing nanoagent based on graphene oxide decorated with iron hydroxide/oxide (GO-FeOxH) was developed for light-activated nanomaterial-mediated PDT. This nanocomposite, GO-FeOxH was prepared via the one-step electrooxidation of iron nails in an aqueous GO solution. The as-prepared GO-FeOxH showed a much higher reactive oxygen species (ROS) activity under NIR light irradiation than GO...
January 9, 2017: Nanoscale
https://www.readbyqxmd.com/read/28067232/oxidized-nucleotide-insertion-by-pol-%C3%AE-confounds-ligation-during-base-excision-repair
#12
Melike Çağlayan, Julie K Horton, Da-Peng Dai, Donna F Stefanick, Samuel H Wilson
Oxidative stress in cells can lead to accumulation of reactive oxygen species and oxidation of DNA precursors. Oxidized purine nucleotides can be inserted into DNA during replication and repair. The main pathway for correcting oxidized bases in DNA is base excision repair (BER), and in vertebrates DNA polymerase β (pol β) provides gap filling and tailoring functions. Here we report that the DNA ligation step of BER is compromised after pol β insertion of oxidized purine nucleotides into the BER intermediate in vitro...
January 9, 2017: Nature Communications
https://www.readbyqxmd.com/read/28066982/visible-light-promoted-nickel-and-organic-dye-cocatalyzed-formylation-reaction-of-aryl-halides-and-triflates-and-vinyl-bromides-with-diethoxyacetic-acid-as-a-formyl-equivalent
#13
He Huang, Xiangmin Li, Chenguang Yu, Yueteng Zhang, Patrick S Mariano, Wei Wang
A simple formylation reaction of aryl halides, aryl triflates, and vinyl bromides under synergistic nickel- and organic-dye-mediated photoredox catalysis is reported. Distinct from widely used palladium-catalyzed formylation processes, this reaction proceeds by a two-step mechanistic sequence involving initial in situ generation of the diethoxymethyl radical from diethoxyacetic acid by a 4CzIPN-mediated photoredox reaction. The formyl-radical equivalent then undergoes nickel-catalyzed substitution reactions with aryl halides and triflates and vinyl bromides to form the corresponding aldehyde products...
January 9, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28060499/correlating-reactivity-and-selectivity-to-cyclopentadienyl-ligand-properties-in-rh-iii-catalyzed-c-h-activation-reactions-an-experimental-and-computational-study
#14
Tiffany Piou, Fedor Romanov-Michailidis, Maria Romanova-Michaelides, Kelvin E Jackson, Natthawat Semakul, Trevor D Taggart, Brian S Newell, Christopher D Rithner, Robert S Paton, Tomislav Rovis
Cp(X)Rh(III)-catalyzed C-H functionalization reactions are a proven method for the efficient assembly of small molecules. However, rationalization of the effects of cyclopentadienyl (Cp(X)) ligand structure on reaction rate and selectivity has been viewed as a black box, and a truly systematic study is lacking. Consequently, predicting the outcomes of these reactions is challenging because subtle variations in ligand structure can cause notable changes in reaction behavior. A predictive tool is, nonetheless, of considerable value to the community as it would greatly accelerate reaction development...
January 6, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28058283/insight-into-transmetalation-enables-cobalt-catalyzed-suzuki-miyaura-cross-coupling
#15
Jamie M Neely, Máté J Bezdek, Paul J Chirik
Among the fundamental transformations that comprise a catalytic cycle for cross coupling, transmetalation from the nucleophile to the metal catalyst is perhaps the least understood. Optimizing this elementary step has enabled the first example of a cobalt-catalyzed Suzuki-Miyaura cross coupling between aryl triflate electrophiles and heteroaryl boron nucleophiles. Key to this discovery was the preparation and characterization of a new class of tetrahedral, high-spin bis(phosphino)pyridine cobalt(I) alkoxide and aryloxide complexes, ((iPr)PNP)CoOR, and optimizing their reactivity with 2-benzofuranylBPin (Pin = pinacolate)...
December 28, 2016: ACS Central Science
https://www.readbyqxmd.com/read/28057904/a-serine-threonine-phosphatase-1-of-streptococcus-suis-type-2-is-an-important-virulence-factor
#16
Lihua Fang, Pengcheng Fan, Yunkai Yang, Jingjing Zhou, Hongxia Shen, Weihuan Fang
Streptococcus suis is regarded as one of the major pathogens of pigs while S. suis type 2 (SS2) is considered to be a zoonotic bacterium for its ability to cause meningitis and streptococcal toxic shock-like syndrome in humans. Many bacterial species contain genes encoding serine/threonine protein phosphatases (STP) responsible for dephosphorylation of their substrates in a single reaction step. This study was aimed to investigate the role of stp1 in pathogenesis of SS2. An isogenic stp1 mutant (Δstp1) was constructed from the SS2 strain ZJ081101...
January 4, 2017: Journal of Veterinary Science
https://www.readbyqxmd.com/read/28057346/pyrite-oxidation-in-the-presence-of-hematite-and-alumina-ii-effects-on-the-cathodic-and-anodic-half-cell-reactions
#17
Carlito Baltazar Tabelin, Suchol Veerawattananun, Mayumi Ito, Naoki Hiroyoshi, Toshifumi Igarashi
The oxidative dissolution of pyrite is an important process in the redox recycling of iron (Fe) and is well-known for its role in the formation of acid mine drainage (AMD), which is considered as the most serious and widespread problem after the closure of mines and mineral processing operations. Because this process requires the movement of electrons, common metal oxides in nature that have either semiconducting (e.g., hematite) or insulating (e.g., alumina) properties may have strong effects on it. In this study, changes in the electrochemical behavior of pyrite in the presence of hematite and alumina were investigated...
January 3, 2017: Science of the Total Environment
https://www.readbyqxmd.com/read/28055957/analysis-of-molecular-mechanisms-of-5-fluorouracil-induced-steatosis-and-inflammation-in-vitro-and-in-mice
#18
Judith Sommer, Abdo Mahli, Kim Freese, Tobias S Schiergens, Fulya Suzan Kuecuekoktay, Andreas Teufel, Wolfgang E Thasler, Martina Müller, Anja K Bosserhoff, Claus Hellerbrand
Chemotherapy-associated steatohepatitis is attracting increasing attention because it heralds an increased risk of morbidity and mortality in patients undergoing surgery because of liver metastases. The aim of this study was to develop in vitro and in vivo models to analyze the pathogenesis of 5-fluorouracil (5-FU)-induced steatohepatitis.Therefore, primary human hepatocytes and HepG2 hepatoma cells were incubated with 5-FU at non-toxic concentrations up to 24 h. Furthermore, hepatic tissue of C57BL/6N mice was analyzed 24 h after application of a single 5-FU dose (200 mg/kg body weight)...
December 30, 2016: Oncotarget
https://www.readbyqxmd.com/read/28054773/reactivity-of-elemental-tin-and-zinc-toward-organophosphonic-acid-dialkyl-esters-a-new-one-pot-recipe-for-the-synthesis-of-coordination-assemblies-derived-from-o-alkylorganophosphonate-ligands
#19
Ravi Shankar, Swati Mendiratta, Nisha Singla, Gabriele Kociok-Köhn, Michael Lutter, Klaus Jurkschat
A new recipe for the synthesis of diorganotin bis(O-alkylorganophosphonate)s, R(1)2Sn{O(P)(O)(OR(1))R}2 [R = R(1) = methyl (1); R(1) = ethyl and R = methyl (2), allyl (3), 2-thienyl (4), benzyl (5)], has been developed from the direct reaction of elemental tin (powder) with organophosphonic acid dialkyl esters, RP(O)(OR(1))2, in the presence of a catalytic amount of potassium iodide under ambient conditions (130 °C, 18-20 h). The key steps in the proposed catalytic cycle involve the monodealkylation of phosphonate diester and in situ generation of a R(1)SnI or R(1)2SnI2 intermediate via the oxidative addition of alkyl iodide on tin...
January 5, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28053664/the-coptotermes-gestroi-aldo-keto-reductase-a-multipurpose-enzyme-for-biorefinery-applications
#20
Robson Tramontina, João Paulo L Franco Cairo, Marcelo V Liberato, Fernanda Mandelli, Amanda Sousa, Samantha Santos, Sarita Cândida Rabelo, Bruna Campos, Jaciane Ienczak, Roberto Ruller, André R L Damásio, Fabio Marcio Squina
BACKGROUND: In nature, termites can be considered as a model biological system for biofuel research based on their remarkable efficiency for lignocellulosic biomass conversion. Redox enzymes are of interest in second-generation ethanol production because they promote synergic enzymatic activity with classical hydrolases for lignocellulose saccharification and inactivate fermentation inhibitory compounds produced after lignocellulose pretreatment steps. RESULTS: In the present study, the biochemical and structural characteristics of the Coptotermes gestroi aldo-keto reductase (CgAKR-1) were comprehensively investigated...
2017: Biotechnology for Biofuels
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