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Chiral separation

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https://www.readbyqxmd.com/read/28453914/the-shape-of-things-to-come-the-formation-of-modulated-nematic-mesophases-at-various-length-scales
#1
Richard J Mandle
The twist-bend nematic phase is a recently discovered liquid-crystalline phase that exhibits macroscopic chirality even when formed from achiral materials, and as such presents a unique testbed for studies concerning the spontaneous breaking of mirror symmetry in soft matter. It is primarily exhibited by materials whose molecular structure is composed of two rigid aromatic units (such as biphenyl connected by a flexible spacer). The local structure of the NTB phase is nematic-like - with molecules having an average orientational order but no positional order - with a nanoscale helix where the pitch is of the order of several nanometres...
April 28, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28442412/hsccc-separation-and-enantiomeric-distribution-of-key-volatile-constituents-of-piper-claussenianum-miq-c-dc-piperaceae
#2
André M Marques, Catharina E Fingolo, Maria Auxiliadora C Kaplan
High Speed Countercurrent Chromatography (HSCCC) technique was used for the preparative isolation of the major leishmanicidal compounds from the essential oils of Piper claussenianum species in Brazil. The essential oils from inflorescences of P. claussenianum were analyzed by GC-FID and GC-MS. The enantiomeric ratio of the major constituents of the P. claussenianum essential oils were determined using a Rt-DEXsm chiral capillary column by GC-FID analysis. It was found an enantiomeric excess of (+)-(E)-nerolidol in the leaves, and (+)-linalool and (+)-(E)-nerolidol in the inflorescences essential oil...
April 22, 2017: Food and Chemical Toxicology
https://www.readbyqxmd.com/read/28440070/chiral-analysis-of-amphetamines-in-hair-by-liquid-chromatography-tandem-mass-spectrometry-compliance-monitoring-of-attention-deficit-hyperactivity-disorder-adhd-patients-under-elvanse%C3%A2-therapy-and-identification-after-controlled-low-dose-application
#3
Tina M Binz, Elena Williner, Petra Strajhar, Patrick C Dolder, Matthias E Liechti, Markus R Baumgartner, Thomas Kraemer, Andrea E Steuer
Amphetamine (AMP) is used as illicit drug but also for the treatment of attention deficit hyperactivity disorder (ADHD). Respective drugs most often contain the enantiomer (S)-AMP as active compound or (S)-AMP is formed from the prodrug lisdexamfetamine (Elvanse®) whereas the illicit drug is usually traded as racemate ((R/S)-AMP). A differentiation between the use of the medically prescribed drug and the abuse of illicit street amphetamine is of great importance e.g. in retrospective consumption monitoring by hair analysis...
April 24, 2017: Drug Testing and Analysis
https://www.readbyqxmd.com/read/28437577/high-gene-flow-despite-opposite-chirality-in-hybrid-zones-between-enantiomorphic-door-snails
#4
Eva L Koch, Marco T Neiber, Frank Walther, Bernhard Hausdorf
We studied differentiation and gene flow patterns between enantiomorphic door-snail species in two hybrid zones in the Bucegi Mountains (Romania) to investigate the effects of intrinsic barriers (complications in copulation) and extrinsic selection by environmental factors. A mitochondrial gene tree confirmed the historical separation of the examined populations into the dextral Alopia livida and the sinistral Alopia straminicollis in accordance with the morphological classification, but also indicated gene flow between the species...
April 24, 2017: Molecular Ecology
https://www.readbyqxmd.com/read/28437017/determination-of-the-enantiomeric-purity-of-the-selective-dopamine-transporter-inhibitor-r-r-4-2-benzhydryloxyethyl-1-4-fluorobenzyl-piperidin-3-ol
#5
Patrick Neiens, Georg Höfner, Klaus T Wanner
(+)-R,R-D-84 ((+)-R,R-4-(2-benzhydryloxyethyl)-1-(4-fluorobenzyl)piperidin-3-ol) is a promising pharmacological tool for the dopamine transporter (DAT), due to its high affinity and selectivity for this target. In this study, an analytical method to ascertain the enantiomeric purity of this compound was established. For this purpose, a high-performance liquid chromatographic (HPLC) method, based on a cellulose derived chiral stationary phase (CSP) was developed. The method was characterized concerning its specificity, linearity, and range...
April 24, 2017: Chirality
https://www.readbyqxmd.com/read/28436118/enantioselective-potential-of-polysaccharide-based-chiral-stationary-phases-in-supercritical-fluid-chromatography
#6
Gabriela Kucerova, Kveta Kalikova, Eva Tesarova
The enantioselective potential of two polysaccharide-based chiral stationary phases for analysis of chiral structurally diverse biologically active compounds was evaluated in supercritical fluid chromatography using a set of 52 analytes. The chiral selectors immobilized on 2.5 μm silica particles were tris-(3,5-dimethylphenylcarmabate) derivatives of cellulose or amylose. The influence of the polysaccharide backbone, different organic modifiers, and different mobile phase additives on retention and enantioseparation was monitored...
April 24, 2017: Chirality
https://www.readbyqxmd.com/read/28432770/chiral-separation-of-aryloxyphenoxy-propionate-herbicides-in-a-permethyl-%C3%AE-cyclodextrin-based-column-influence-of-temperature-and-mobile-phase-composition-on-enantioselectivity
#7
Ester Lubomirsky, Héctor Di Loreto, Juan M Padró, Cecilia B Castells
We used a permethyl-β-cyclodextrin chiral stationary phase under reversed-phase conditions for the chiral separation of four aryloxyphenoxy-propionate herbicides (fenoxaprop-p-ethyl, quizalofop-p-ethyl and tefuryl and haloxyfop-p-methyl) with mixtures of methanol, ethanol, 2-propanol, n-propanol, tert-butanol, or acetonitrile and water as mobile phases and investigated the influence of mobile phase composition and column temperature (from 0 to 50 °C) on the separation. The retention factors (k) and selectivity factors (α) of all the herbicides investigated decreased with increasing temperature...
April 22, 2017: Electrophoresis
https://www.readbyqxmd.com/read/28432685/chiral-analysis-of-%C3%AE-diimine-ru-ii-and-fe-ii-complexes-by-capillary-electrophoresis-using-sulfated-cyclodextrins-as-stereoselectors
#8
Petra Sázelová, Dušan Koval, Lukáš Severa, Filip Teplý, Václav Kašička
Capillary electrophoresis (CE) using randomly highly sulfated α-, β-, and γ-cyclodextrins (S-α-CD, S-β-CD, S-γ-CD), sulfobutylether-β-CD (SBE-β-CD), single isomer (6-O-sulfo) α-, β-, and γ-CDs and their derivatives as stereoselectors was applied to chiral analysis of polypyridyl complexes of [Ru(bpy)3 ](2+) , [Ru(phen)3 ](2+) , and [Fe(phen)3 ](2+) (bpy = 2,2'-bipyridine; phen = 1,10 phenanthroline). The best separations of Δ- and Λ-enantiomers of the these complexes with high resolution (up to R1,2  = 7...
April 22, 2017: Electrophoresis
https://www.readbyqxmd.com/read/28431453/carboxymethyl-%C3%AE-cyclodextrin-as-chiral-selector-in-capillary-electrophoresis-enantioseparation-of-16-basic-chiral-drugs-and-its-chiral-recognition-mechanism-associated-with-drugs-structural-features
#9
Linlin Fang, Yueying Du, Xiaoyu Hu, Linda Luo, Xin Guo, Xingjie Guo, Jia Yu
Herein we present the enantioseparation of 10 cardiovascular agents and 6 bronchiectasis drugs including propranolol, carteolol, metoprolol, atenolol, pindolol, esmolol, bisoprolol, bevantolol, arotinolol, sotalol, clenbuterol, procaterol, bambuterol, tranterol, salbutamol and terbutaline sulfate using carboxymethyl-β-cyclodextrin (CM-β-CD) as chiral selector. To our knowledge, there is no literature about using CM-β-CD for separating carteolol, esmolol, bisoprolol, bevantolol, arotinolol, procaterol, bambuterol and tranterol...
April 21, 2017: Biomedical Chromatography: BMC
https://www.readbyqxmd.com/read/28430424/elucidation-of-the-stereospecificity-of-c-methyltransferases-from-trans-at-polyketide-synthases
#10
Xinqiang Xie, Chaitan Khosla, David E Cane
S-Adenosyl methionine (SAM)-dependent C-methyltransferases are responsible for the C2-methylation of 3-ketoacyl-acyl carrier protein (ACP) intermediates to give the corresponding 2-methy-3-ketoacyl-ACP products during bacterial polyketide biosynthesis mediated by trans-AT polyketide synthases that lack integrated acyl transferase (AT) domains. A coupled ketoreductase (KR) assay was used to assign the stereochemistry of the C-methyltransferase-catalyzed reaction. Samples of chemoenzymatically-generated 3-ketopentanoyl-ACP (9) were incubated with SAM and BonMT2 from module 2 of the bongkrekic acid polyke-tide synthase...
April 21, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28430135/a-homochiral-multifunctional-metal-organic-framework-with-rod-shaped-secondary-building-units
#11
Kun Cai, Nian Zhao, Ning Zhang, Fu-Xing Sun, Qing Zhao, Guang-Shan Zhu
A new homochiral multifunctional metal-organic framework, [Zn₂(CTBA)₂·H₂O] (JUC-112), was synthesized under solvothermal conditions, through the design of chiral ligand 4-(3-carboxy-2,2,3-trimethylcyclopentanecarboxamido) benzoic acid (H₂CTBA) based on camphoric acid as building block. The crystal structure of the new material is a 2-dimensional (2D) chiral layer packed with infinite rod-shaped secondary building units (SBUs). The homochiral framework was identified by circular dichroism (CD) spectrum...
April 21, 2017: Nanomaterials
https://www.readbyqxmd.com/read/28426196/chiral-inorganic-nanostructures
#12
Wei Ma, Liguang Xu, André F de Moura, Xiaoling Wu, Hua Kuang, Chuanlai Xu, Nicholas A Kotov
The field of chiral inorganic nanostructures is rapidly expanding. It started from the observation of strong circular dichroism during the synthesis of simple nanoparticles (NPs) and their assemblies mediated by biomolecules and expanded to sophisticated synthetic protocols involving nanostructures from metals, semiconductors, ceramics, and nanocarbons. Besides the well-established chirality transfer from bioorganic molecules, other methods to impart handedness to nanoscale matter specific to inorganic materials were discovered, including three-dimentional lithography, multiphoton chirality transfer, polarization effects in nanoscale assemblies, and others...
April 20, 2017: Chemical Reviews
https://www.readbyqxmd.com/read/28422383/liquid-and-subcritical-fluid-chromatographic-enantioseparation-of-n-%C3%AE-fmoc-proteinogenic-amino-acids-on-quinidine-based-zwitterionic-and-anion-exchanger-type-chiral-stationary-phases-a-comparative-study
#13
Gyula Lajkó, Nóra Grecsó, Gábor Tóth, Ferenc Fülöp, Wolfgang Lindner, István Ilisz, Antal Péter
Stereoselective high-performance liquid chromatographic and subcritical fluid chromatographic separations of 19 N(α) -Fmoc proteinogenic amino acid enantiomers were carried out by using Quinidine-based zwitterionic and anion-exchanger-type chiral stationary phases Chiralpak ZWIX(-) and QD-AX. For optimization of retention and enantioselectivity, the ratio of bulk solvent components (MeOH/MeCN, H2 O/MeOH, or CO2 /MeOH) and the nature and concentration of the acid and base additives (counter- and co-ions) were systematically varied...
April 19, 2017: Chirality
https://www.readbyqxmd.com/read/28422324/optical-resolution-and-mechanism-using-enantioselective-cellulose-sodium-alginate-and-hydroxypropyl-%C3%AE-cyclodextrin-membranes
#14
Li-Ming Yuan, Wei Ma, Mei Xu, Hui-Lin Zhao, Yuan-Yuan Li, Rui-Lin Wang, Ai-Hong Duan, Ping Ai, Xue-Xian Chen
Chiral solid membranes of cellulose, sodium alginate, and hydroxypropyl-β-cyclodextrin were prepared for chiral dialysis separations. After optimizing the membrane material concentrations, the membrane preparation conditions and the feed concentrations, enantiomeric excesses of 89.1%, 42.6%, and 59.1% were obtained for mandelic acid on the cellulose membrane, p-hydroxy phenylglycine on the sodium alginate membrane, and p-hydroxy phenylglycine on the hydroxypropyl-β-cyclodextrin membrane, respectively. To study the optical resolution mechanism, chiral discrimination by membrane adsorption, solid phase extraction, membrane chromatography, high-pressure liquid chromatography ultrafiltration were performed...
April 19, 2017: Chirality
https://www.readbyqxmd.com/read/28421635/a-homochiral-co%C3%AE-%C3%AE-16co%C3%AE-%C3%AE-%C3%AE-4-supertetrahedral-t4-cluster-from-a-racemic-ligand-with-ferromagnetic-behavior-and-high-photocatalytic-activity
#15
Yue-Ling Bai, Wei Du, Xiuping Yin, Jianhui Fang, Shourong Zhu, Jun Tao
A homochiral mixed-valence cobalt cluster [CoΙΙ16CoΙΙΙ4(μ6-O)4(μ3-OH)12(S-bme)12(OAc)6]Cl6·5CH3OH·18H2O (1, Hbme = 1H-(benzimidazol-2-yl)ethanol) was synthesized from a racemic ligand and three cobalt salts of CoCl2·6H2O, Co(Ac)2·4H2O and Co(NO3)2·6H2O in a DMF/MeOH mixed solvent. The enantioselective coordination occurs when a large excess of cobalt ions added in the solution and only the S-configuration of the racemic ligand involved in crystallization. The CD spectra of three crystal samples show identical Cotton signals, indicating the repeatability and the enantiomeric purity of the single crystals...
April 19, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28416216/3-phenyl-4-oxy-5-phenyl-4-5-dihydro-1h-pyrazole-a-fascinating-molecular-framework-to-study-the-enantioseparation-ability-of-the-amylose-3-5-dimethylphenylcarbamate-chiral-stationary-phase-part-ii-solvophobic-effects-in-enantiorecognition-process
#16
Marco Pierini, Simone Carradori, Sergio Menta, Daniela Secci, Roberto Cirilli
The enantiomers of five chiral compounds incorporating the 3-(phenyl-4-oxy)-5-phenyl-4,5-dihydro-(1H)-pyrazole scaffold and differing only in the linear alkyl chain (varying in length from 1 to 5 carbon atoms) linked to the oxygen atom were directly separated on the amylose (3,5-dimethylphenylcarbamate) based Chiralpak AD-3 chiral stationary phase. The effects of the mobile phase composition, the structure of the analytes and temperature on the retention and enantioselectivity were investigated. It was found that the enantiomeric separations were in all cases enthalpy-driven and disfavored by entropic term...
April 4, 2017: Journal of Chromatography. A
https://www.readbyqxmd.com/read/28411631/escherichia-coli-adhesive-coating-as-a-chiral-stationary-phase-for-open-tubular-capillary-electrochromatography-enantioseparation
#17
Qifeng Fu, Kailian Zhang, Die Gao, Lujun Wang, Fengqing Yang, Yao Liu, Zhining Xia
Bacteria, the microorganism with intrinsic chirality, have numerous fascinating chiral phenomena such as various chirality-triggered biological processes and behaviors. Herein, bacteria were firstly explored as novel chiral stationary phases in open-tubular capillary electrochromatography (OT-CEC) for enantioseparation of fluoroquinolone enantiomers and simultaneous separation of six fluoroquinolone antibiotics. The model strain, i.e. non-pathogenic Escherichia coli (E. coli) DH5α, was adhered onto the inner surface of positively charged polyethyleneimine (PEI) modified capillaries based on the bacterial adhesion characteristics and strong electrostatic interaction...
May 29, 2017: Analytica Chimica Acta
https://www.readbyqxmd.com/read/28411214/achiral-symmetry-breaking-and-positive-gaussian-modulus-lead-to-scalloped-colloidal-membranes
#18
Thomas Gibaud, C Nadir Kaplan, Prerna Sharma, Mark J Zakhary, Andrew Ward, Rudolf Oldenbourg, Robert B Meyer, Randall D Kamien, Thomas R Powers, Zvonimir Dogic
In the presence of a nonadsorbing polymer, monodisperse rod-like particles assemble into colloidal membranes, which are one-rod-length-thick liquid-like monolayers of aligned rods. Unlike 3D edgeless bilayer vesicles, colloidal monolayer membranes form open structures with an exposed edge, thus presenting an opportunity to study elasticity of fluid sheets. Membranes assembled from single-component chiral rods form flat disks with uniform edge twist. In comparison, membranes composed of a mixture of rods with opposite chiralities can have the edge twist of either handedness...
April 14, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28409966/parafermionic-wires-at-the-interface-of-chiral-topological-states
#19
Luiz H Santos, Taylor L Hughes
We explore a scenario where local interactions form one-dimensional gapped interfaces between a pair of distinct chiral two-dimensional topological states-referred to as phases 1 and 2-such that each gapped region terminates at a domain wall separating the chiral gapless edge states of these phases. We show that this type of T junction supports pointlike fractionalized excitations obeying parafermion statistics, thus implying that the one-dimensional gapped interface forms an effective topological parafermionic wire possessing a nontrivial ground state degeneracy...
March 31, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28403568/preparative-chiral-separation-and-absolute-configuration-of-the-synthetic-pterocarpanquinone-lqb-118
#20
Gabriel S Scatena, Neila M Cassiano, Chaquip D Netto, Paulo R R Costa, Quezia B Cass, João M Batista
The racemic pterocarpanquinone LQB-118 is active, in mice and hamsters, against tegumentary and visceral leishmaniasis. This compound also presents antiinflammatory and antineoplastic activity in mice. The low level of toxicity observed in these studies makes LQB-118 a promising drug candidate. In order to conduct further biological testing to investigate enantioselectivity in the above-mentioned activities, a multimilligram amount of each enantiomer of LQB-118 was produced. Furthermore, vibrational circular dichroism (VCD) and Density Functional Theory (DFT) calculations were used to determine unambiguously their absolute configurations...
May 2017: Chirality
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