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https://www.readbyqxmd.com/read/28437706/three-phases-in-ph-dependent-heme-abstraction-from-myoglobin
#1
Sohini Mukherjee, Manjistha Mukherjee, Sabyasachi Bandyopadhyay, Abhishek Dey
The extent of heme extraction from myoglobin (Mb) by methylethyl ketone is found to be pH dependent and show three distinct phases. Parallel investigations of the protein using resonance Raman (rR) and circular dichroism (CD) across these pH regions indicate that these phases correspond to three different protonation steps in holoMb as the pH of the solution changed. The first transition occurs between pH5-6 and is due to the protonation of one of the heme propionate groups which disrupts its H-bonding with Arg 45 in the loop...
April 9, 2017: Journal of Inorganic Biochemistry
https://www.readbyqxmd.com/read/28437344/comparison-of-the-posterior-vertebral-column-resection-with-the-expandable-cage-versus-the-nonexpandable-cage-in-thoracolumbar-angular-kyphosis
#2
Jung-Hee Lee, Hyun-Seok Oh, Jeong-Gyu Choi
STUDY DESIGN: This was a retrospective study. OBJECTIVE: To compare the radiographic and clinical results of anterior support with nonexpandable cage with those of expandable cage. SUMMARY OF BACKGROUND DATA: The goals of surgical treatment in patients with thoracolumbar angular kyphosis are to improve the neurological deficit through neural decompression, to restore the normal alignment by correction of deformity, and to stabilize the spinal column by arthrodesis...
May 2017: Clinical Spine Surgery
https://www.readbyqxmd.com/read/28436674/general-dialdehyde-click-chemistry-for-amine-bioconjugation
#3
Sina Elahipanah, Paul J O'Brien, Dmitry Rogozhnikov, Muhammad N Yousaf
The development of methods for conjugating a range of molecules to primary amine functional groups has revolutionized the fields of chemistry, biology, and material science. The primary amine is a key functional group and one of the most important nucleophiles and bases used in all of synthetic chemistry. Therefore, tremendous interest in the synthesis of molecules containing primary amines and strategies to devise chemical reactions to react with primary amines has been at the core of chemical research. In particular, primary amines are a ubiquitous functional group found in biological systems as free amino acids, as key side chain lysines in proteins, and in signaling molecules and metabolites and are also present in many natural product classes...
April 24, 2017: Bioconjugate Chemistry
https://www.readbyqxmd.com/read/28436515/exploring-the-reversal-of-enantioselectivity-on-a-zinc-dependent-alcohol-dehydrogenase
#4
Miguel A Maria-Solano, Adrian Romero-Rivera, Sílvia Osuna
Alcohol Dehydrogenase (ADH) enzymes catalyse the reversible reduction of prochiral ketones to the corresponding alcohols. These enzymes present two differently shaped active site pockets, which dictate their substrate scope and selectivity. In this study, we computationally evaluate the effect of two commonly reported active site mutations (I86A, and W110T) on a secondary alcohol dehydrogenase from Thermoanaerobacter brockii (TbSADH) through Molecular Dynamics simulations. Our results indicate that the introduced mutations induce dramatic changes in the shape of the active site, but most importantly they impact the substrate-enzyme interactions...
April 24, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28436199/a-method-for-the-late-stage-formation-of-ketones-acyloins-and-aldols-from-alkenylstannanes-application-to-the-total-synthesis-of-paecilonic-acid%C3%A2-a
#5
Heiko Sommer, James Y Hamilton, Alois Fürstner
Treatment of alkenylstannanes with Cu(OAc)2 /Et3 N affords the corresponding enol esters or ketones under conditions that proved compatible with many common functionalities; these include groups that would neither survive under the standard Tamao-Fleming conditions for the oxidation of Csp2 -SiR3 bonds nor under the conditions commonly used to oxidize C-B bonds. Chiral centers adjacent to the unveiled carbonyls are not racemized and competing protodestannation is marginal, even if the substrate carries unprotected -OH groups as internal proton sources...
April 24, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28436195/organocatalytic-enantioselective-acyloin-rearrangement-of-%C3%AE-hydroxy-acetals-to-%C3%AE-alkoxy-ketones
#6
Hua Wu, Qian Wang, Jieping Zhu
We report an unprecedented organocatalytic enantioselective acyloin rearrangement of α,α-disubstituted α-hydroxy acetals. In the presence of a catalytic amount of chiral binol-derived N-triflyl phosphoramide, α-hydroxy acetals rearranged to α-alkoxy ketones in good to high yields with high enantioselectivities. Formation of an ion pair between the in situ generated oxocarbenium ion and the chiral phosphoramide anion was proposed to be responsible for the highly efficient transfer of chirality. Conditions for removal of cyclohexyl and cyclopentyl groups from the corresponding α-alkoxy ketones were uncovered underpinning their potential general utility as hydroxy protecting groups...
April 24, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28433617/induced-and-controlled-dietary-ketosis-as-a-regulator-of-obesity-and-metabolic-syndrome-pathologies
#7
Madeline K Gibas, Kelly J Gibas
A worsening epidemic of diabetes and its precursor, metabolic syndrome (MetS) is engulfing America. A healthy individual, with proper glucose regulation has an ability to switch between burning fat and carbohydrates. It has been suggested that signaling errors within this homeostatic system, characterized by impaired switching of substrate oxidation from glucose to fat in response to insulin, can contribute to the etiology of metabolic syndrome and occurs before the development of type II diabetes. Glucose regulation with restored insulin sensitivity facilitated through clinically regulated, benign dietary ketosis (BDK), may significantly reduce, regulate and reverse the adverse pathologies common to MetS and obesity...
March 28, 2017: Diabetes & Metabolic Syndrome
https://www.readbyqxmd.com/read/28432947/pretreatment-of-eucalyptus-in-biphasic-system-for-furfural-production-and-accelerated-enzymatic-hydrolysis
#8
Xiudong Zhang, Yuanyuan Bai, Xuefei Cao, Runcang Sun
Herein, an efficient biphasic pretreatment process was developed to improve the production of furfural (FF) and glucose from Eucalyptus. The influence of formic acid and NaCl on FF production from xylose in water and various biphasic systems was investigated. Results showed that the addition of formic acid and NaCl significantly promoted the FF yield, and the biphasic system of MIBK (methyl isobutyl ketone)/water exhibited the best performance for FF production. Then the Eucalyptus was pretreated in the MIBK/water system, and a maximum FF yield of 82...
April 7, 2017: Bioresource Technology
https://www.readbyqxmd.com/read/28431318/assessing-seasonal-variation-of-synthetic-musks-in-beach-sands-from-oporto-coastal-area-a-case-study
#9
Vera Homem, Inês Magalhães, Arminda Alves, Lúcia Santos
Synthetic musk compounds are widely used in the formulation of several cosmetics, personal care and household products. Due to their massive and widespread use, together with some health concerns, they are considered emerging pollutants and have been detected in different environmental compartments. This study focused on the evaluation of the concentration of synthetic musks (five nitro, five polycyclic and one macrocyclic musks) in beach sands, from Oporto coastal area (Portugal), contributing to the enhancement of the knowledge of levels, trends and behaviour of these compounds in this particular matrix...
April 18, 2017: Environmental Pollution
https://www.readbyqxmd.com/read/28431257/integrated-antimicrobial-and-antifouling-ultrafiltration-membrane-by-surface-grafting-peo-and-n-chloramine-functional-groups
#10
Shuhua Hou, Jialin Xing, Xue Dong, Jifu Zheng, Shenghai Li
Ultrafiltration membranes with integrated antimicrobial and antifouling properties were fabricated using an engineering thermoplastic (carboxylated cardopoly(aryl ether ketone, PEK-COOH). Different molecular weights of PEO (Mw: 120, 350, 550) were grafted to the PEK-COOH membrane surface via EDC/NHS methodology. N-chloramine modified membranes then were prepared by simple exposure to dilute sodium hypochlorite solution. The surface grafting processes were all performed in water (i.e. without organic solvent)...
April 11, 2017: Journal of Colloid and Interface Science
https://www.readbyqxmd.com/read/28430444/molecular-structuring-and-percolation-transition-in-hydrated-sulfonated-poly-ether-ether-ketone-membranes
#11
Madhusmita Tripathy, Sunil Kumar P B, Abhijit P Deshpande
The extent of phase separation and water percolation in sulfonated membranes are the key to their performance in fuel cells. Toward this, the effect of hydration on the morphology and transport characteristics of sulfonated poly(ether ether ketone), sPEEK, membrane is investigated using atomistic molecular dynamics simulation at various hydration levels($\lambda$: number of water molecules per sulfonate group). The evolution of local morphology is investigated using structural correlations and minimum pair distances...
April 21, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28429413/vanadium-v-induced-oxidative-cross-coupling-of-various-boron-and-silyl-enolates
#12
Toru Amaya, Yuma Osafune, Yusuke Maegawa, Toshikazu Hirao
Intermolecular oxidative cross-coupling of two different enolates is one of the most useful reactions to synthesize unsymmetrical 1,4-dicarbonyl compounds. In this study, the oxovanadium(V)-induced intermolecular oxidative cross-coupling of enolates was achieved to give the corresponding unsymmetrical 1,4-dicarbonyl compounds, where combination of various boron and silyl enolates such as ketone-ester, ester-ketone, ester-ester, amide-ketone, and amide-ester enolates was adapted. These results clearly exhibit the versatility of the present oxidative cross-coupling protocol...
April 20, 2017: Chemistry, An Asian Journal
https://www.readbyqxmd.com/read/28429384/enantioselective-silver-and-amine-co-catalyzed-desymmetrizing-cycloisomerization-of-alkyne-linked-cyclohexanones
#13
Rubén Manzano, Swarup Datta, Robert S Paton, Darren J Dixon
A silver(I) and amine co-catalyzed desymmetrization of 4-propargylamino cyclohexanones for the direct enantioselective synthesis of 2-azabicyclo[3.3.1]nonanes is described. Exploiting reactivity arising from dual activation of the pendant terminal alkyne by silver(I) and the ketone moiety through transient enamine formation, this synthetically relevant transformation is easy to perform, efficient and broad in scope. High enantioselectivity (up to 96 % ee) was achieved by exploiting a significant matching effect between the chirality of a cinchona alkaloid-derived aminophosphine ligand for the silver(I) salt and the 2-bis(aryl)methylpyrrolidine catalyst which was rationalized by DFT calculations...
April 21, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28425958/reactions-of-5-indolizyl-lithium-compounds-with-some-bielectrophiles
#14
Sergey A Rzhevskii, Victor B Rybakov, Victor N Khrustalev, Eugene V Babaev
Abstract: Indolizyl-5-lithium anions react with succinic and phtalic anhidrides giving 1,4-keto acids, with oxallyl chloride giving 1,2-diketone, and with ethyl pyruvate giving 1,2-hydroxyacid. However, with α-halocarbonyl compounds, they react in different ways, forming the products of selective bromination at C-5 (with α-bromo ketones and esters of α-bromo acids) and 5-chloroacetyl indolizines.
April 20, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/28425852/discovery-of-novel-2-amino-5-substituted-1-3-4-thiadiazole-derivatives-new-utilities-for-colon-cancer-treatment
#15
Vinit Raj, Amit Rai, Ashok K Singh, Amit K Keshari, Prakruti Harshvardhanbhai Trivedi, Balaram Ghosh, Umesh Kumar, Dinesh Kumar, Sudipta Saha
In this study, we designed and synthesized (VR1 to VR35) a novel series of 1,3,4-thiadiazole derivatives from 2-amino-5-(substituted)-1,3,4-thiadiazole condensed with substituted aldehyde or ketone in the presence of glacial acetic acid via Wolff-Kishner reduction. Further, synthesized compounds were characterized by FTIR, NMR (1H and 13C), MS and elemental analyses. Before the synthesis, docking studies were performed using various molecular targets of colon cancer like IL-2, IL-6, COX-2, caspase-3, and caspase-8...
April 19, 2017: Anti-cancer Agents in Medicinal Chemistry
https://www.readbyqxmd.com/read/28425592/mesoporous-titanium-oxide-with-high-specific-surface-area-as-a-coating-for-in-tube-solid-phase-microextraction-combined-with-hplc-for-the-analysis-of-polycyclic-aromatic-hydrocarbons
#16
Xiuqin Wang, Juanjuan Feng, Yanan Bu, Yu Tian, Chuannan Luo, Min Sun
Stainless-steel wires coated with mesoporous titanium oxide were placed into a polyether ether ketone tube for in-tube solid-phase microextraction, and the coating sorbent was characterized by X-ray diffraction and scanning electron microscopy. It was combined with high performance liquid chromatography to build an online system. Using eight polycyclic aromatic hydrocarbons as the analytes, some conditions including sample flow rate, sample volume, organic solvent content and desorption time were investigated...
April 20, 2017: Journal of Separation Science
https://www.readbyqxmd.com/read/28425169/a-highly-active-manganese-catalyst-for-enantioselective-ketone-and-ester-hydrogenation
#17
Magnus B Widegren, Gavin J Harkness, Alexandra M Z Slawin, David B Cordes, Matthew L Clarke
A new hydrogenation catalyst based on a manganese complex of a chiral P,N,N ligand has been found to be especially active for the hydrogenation of esters down to 0.1 mol % catalyst loading, and gives up to 97 % ee in the hydrogenation of pro-chiral deactivated ketones at 30-50 °C.
April 20, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28423201/highly-enantioselective-allylation-of-ketones-an-efficient-approach-to-all-stereoisomers-of-tertiary-homoallylic-alcohols
#18
Marcus Brauns, Marvin Mantel, Julie Schmauck, Marian Guder, Martin Breugst, Joerg Pietruszka
Optimized protecting group for allylboronates allows the use of ketones to synthesize all isomers of quaternary homoallylic alcohols with high enantioselectivities. All symmetric isomers of the allylboronate can be prepared in high yields and diastereoselectivities using SN2' reactions. The improved reactivity of the novel protecting group is verified via 1H-NMR kinetics. Mechanistic studies using DFT calculations are conducted to investigate the new findings. Thus, the stereochemical outcome and enhanced reactivity can be rationalized...
April 19, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28422492/a-concise-efficient-and-scalable-total-synthesis-of-thapsigargin-and-nortrilobolide-from-r-carvone
#19
Dezhi Chen, P Andrew Evans
A concise, efficient and scalable synthesis of thapsigargin and nortrilobolide from commercially available (R)-(-)-carvone was developed. Our synthetic strategy is inspired by nature's carbon-carbon bond formation sequence, which facilitates the construction of a highly functionalized sesquiterpene lactone skeleton in five steps via an enantioselective ketone alkylation and a diastereoselective pinacol cyclization. We envision that this strategy will permit the construction of other members of the family, structural analogs and provide a practical synthetic route to these important bioactive agents...
April 19, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28422317/a-molecular-mechanics-and-ab-initio-prediction-of-the-1-h-chemical-shifts-of-pinanes
#20
Raymond J Abraham, M Ashley Cooper
Molecular mechanics calculations plus the application of a refined Karplus equation gave the conformations of 19 pinanes. These range from a Y-shaped geometry in the apopinene and α-pinene series to a pseudo chair conformation in β-pinene, nopinone and verbanone, a flattened chair in pinocarvone and the pinocarveols and a distorted Y shape for iso-verbanone. These structures were then used as input to predict the (1) H chemical shifts of these compounds by semi-empirical (HSPEC) and ab initio GIAO calculations, the latter at the B3LYP hybrid DFT level using 6-31++G** basis set...
April 19, 2017: Magnetic Resonance in Chemistry: MRC
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