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Chirality

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https://www.readbyqxmd.com/read/29676476/kinetic-resolution-of-n-acetyl-dl-alanine-methyl-ester-using-immobilized-escherichia-coli-cells-bearing-recombinant-esterase-from-bacillus-cereus
#1
Jianyong Zheng, Xing Lan, Lijuan Huang, Yinjun Zhang, Zhao Wang
D-alanine is widely used in medicine, food, additives, cosmetics, and other consumer items. Esterase derived from Bacillus cereus WZZ001 exhibits high hydrolytic activity and stereoselectivity. In this study, we expressed the esterase gene in Escherichia coli BL21 (DE3). We analyzed the biocatalytic resolution of N-acetyl-DL-alanine methyl ester by immobilized whole E. coli BL21 (DE3) cells, which were prepared through embedding and cross-linking. We analyzed biocatalytic resolution under the optimal conditions of pH of 7...
April 20, 2018: Chirality
https://www.readbyqxmd.com/read/29660182/toward-a-general-mixed-quantum-classical-method-for-the-calculation-of-the-vibronic-ecd-of-a-flexible-dye-molecule-with-different-stable-conformers-revisiting-the-case-of-2-2-2-trifluoro-anthrylethanol
#2
Javier Cerezo, Daniel Aranda, Francisco J Avila Ferrer, Giacomo Prampolini, Giuseppe Mazzeo, Giovanna Longhi, Sergio Abbate, Fabrizio Santoro
We extend a recently proposed mixed quantum/classical method for computing the vibronic electronic circular dichroism (ECD) spectrum of molecules with different conformers, to cases where more than one hindered rotation is present. The method generalizes the standard procedure, based on the simple Boltzmann average of the vibronic spectra of the stable conformers, and includes the contribution of structures that sample all the accessible conformational space. It is applied to the simulation of the ECD spectrum of (S)-2,2,2-trifluoroanthrylethanol, a molecule with easily interconvertible conformers, whose spectrum exhibits a pattern of alternating positive and negative vibronic peaks...
April 16, 2018: Chirality
https://www.readbyqxmd.com/read/29659053/chiral-syntheses-of-methyl-r-2-sulfanylcarboxylic-esters-and-acids-with-optical-purity-determination-using-hplc
#3
Ryosuke Sasaki, Yoo Tanabe
Accessible chiral syntheses of 3 types of (R)-2-sulfanylcarboxylic esters and acids were performed: (R)-2-sulfanylpropanoic (thiolactic) ester (53%, 98%ee) and acid (39%, 96%ee), (R)-2-sulfanylsucciinic diester (59%, 96%ee), and (R)-2-mandelic ester (78%, 90%ee) and acid (59%, 96%ee). The present practical and robust method involves (i) clean SN 2 displacement of methanesulfonates of (S)-2-hydroxyesters by using commercially available AcSK with tris(2-[2-methoxyethoxy])ethylamine and (ii) sufficiently mild deacetylation...
April 16, 2018: Chirality
https://www.readbyqxmd.com/read/29645307/circular-dichroism-studies-of-low-molecular-weight-hydrogelators-the-use-of-srcd-and-addressing-practical-issues
#4
Efstratios D Sitsanidis, Carmen C Piras, Bruce D Alexander, Giuliano Siligardi, Tamás Jávorfi, Andrew J Hall, Alison A Edwards
Circular dichroism (CD) spectroscopy has been used extensively for the investigation of the conformation and configuration of chiral molecules, but its use for evaluating the mode of self-assembly in soft materials has been limited. Herein, we report a protocol for the study of such materials by electronic CD spectroscopy using commercial/benchtop instruments and synchrotron radiation (SR) using the B23 beamline available at Diamond Light Source. The use of the B23 beamtime for SRCD was advantageous because of the unique enhanced spatial resolution achieved because of its highly collimated and small beamlight cross section (ca...
April 12, 2018: Chirality
https://www.readbyqxmd.com/read/29637614/development-of-stability-indicating-hplc-method-for-the-separation-and-validation-of-enantiomers-of-miconazole
#5
Nadia Bounoua, Khaled Sekkoum, Mehmet Gumustas, Nasser Belboukhari, Sibel A Ozkan
A selective and sensitive stability indicting HPLC method was developed for the analysis of enantiomers of miconazole. For this purpose, six different polysaccharide-based chiral columns were evaluated. Optimization was performed using several polar organic and alcohol-hydrocarbon mobile phases. As a result of optimization studies, the analysis was carried out using Lux Cellulose-3, methanol as a mobile phase at a flow rate of 1 mL·min-1 , and the detection wavelength was arranged to 230 nm. Developed method has been fully validated according to International Council on Harmonization guidelines...
April 10, 2018: Chirality
https://www.readbyqxmd.com/read/29624730/structure-retention-relationship-for-enantioseparation-of-selected-fluoroquinolones
#6
Rasha M Hassan, Ali M Yehia, Ola A Saleh, Aida A El-Azzouny, Hassan Y Aboul-Enein
Fluoroquinolones are popular class of antibiotics with distinct chemical functionality. Most of them are ampholytes with one chiral center. Stereogeneic center is located either in the side ring of Gatifloxacin (GFLX) or in the quinolone core of Ofloxacin (OFLX). These two amphoteric fluoroquinolones have terminal amino groups in common. The unusual Nadifloxacin (NFLX) is an acidic fluoroquinolone with a core chiral center. Owing to chirality and functionality differences among GFLX, OFLX, and NFLX, we mapped these enantiomers onto structure-retention relationship...
April 6, 2018: Chirality
https://www.readbyqxmd.com/read/29608222/theoretical-study-on-the-reaction-mechanisms-of-michael-chirality-addition-between-propionaldehyde-and-nitroalkene-catalyzed-by-an-enantioselective-catalyst
#7
Xinming Zhou, Ling Li, Xuejun Sun, Yajun Wang, Dongmei Du, Hui Fu
The asymmetric Michael addition between propionaldehyde and nitroalkene catalyzed by 8-(ethoxycarbonyl)-1,2,3,3a,8,8a-hexahydropyrrolo[2,3-b]indole-2-carboxylic acid has obtained relatively high yields and excellent enantioselectivities at room temperature. In this study, the molecular structures and optical activity of the most stable conformation I are optimized at B3LYP/6-311++ G(d,p) level. We find that levorotatory conformation I catalyzing the same Michael addition can produce laevo-product A and dextrorotatory conformation I' can obtain the dextral-product A'...
April 2, 2018: Chirality
https://www.readbyqxmd.com/read/29578615/enantioselective-complexation-of-1-phenylethanol-with-chiral-compounds-bearing-urea-moiety
#8
Petra Cuřínová, Martin Dračínský, Martin Jakubec, Martin Tlustý, Kristýna Janků, Pavel Izák, Roman Holakovský
A detailed study of diastereomeric complexes of chiral ureido-1,1'-binaphthalene derivatives with chiral 1-phenylethanol showed that a derivative bearing only one urea unit makes five times more stable complex with (S)-enantiomer than with (R)-enantiomer of the alcohol. This phenomenon could be used in chiral discrimination processes. The influence of individual parts of the structure on the complexation properties is shown. The probable structure of diastereomeric complexes based on experimental results and computational methods is proposed...
March 26, 2018: Chirality
https://www.readbyqxmd.com/read/29578614/self-assembly-and-chiroptical-properties-in-supramolecular-complexes-of-adenosine-phosphates-and-guanidinium-bispyrene
#9
Marie Trévisan, Mathieu Fossépré, Delphine Paolantoni, Jenifer Rubio-Magnieto, Pascal Dumy, Sébastien Ulrich, Mathieu Surin
Supramolecular systems that respond to the hydrolysis of adenosine phosphates (APs) are attractive for biosensing and to fabricate bioinspired self-assembled materials. Here, we report on the formation of supramolecular complexes between an achiral guanidinium derivative bearing two pyrene moieties, with each of the three adenosine phosphates: AMP, ADP, and ATP. By combining results from circular dichroism spectroscopy and molecular modeling simulations, we explore the induced chirality, the dynamics of the complexes, and the interactions at play, which altogether provide insights into the supramolecular self-assembly between APs and the guanidinium-bispyrene...
March 26, 2018: Chirality
https://www.readbyqxmd.com/read/29575058/amino-acids-as-chiral-derivatizing-agents-for-antiproliferative-substituted-n-benzyl-isoindolinones
#10
Tatyana A Grigoreva, Daria S Novikova, Maxim A Gureev, Alexander V Garabadzhiu, Vyacheslav G Tribulovich
The absolute configurations of the diastereomers of novel amino acid ester derivatives of 2,3-substituted isoindolinones, which are known as apoptosis activators due to their ability to inhibit the MDM2-p53 PPI, were assigned using NMR and computational methods. Procedures for diastereomer separation and determining the absolute configuration were developed to perform the study. The high significance of N-benzyl fragment for the determination of the diastereomer absolute configuration by NMR methods was established; it is determined by a number of factors inherent in this fragment and the structural features of the studied substrates...
March 25, 2018: Chirality
https://www.readbyqxmd.com/read/29573474/colorimetric-chiral-fluorescent-sensors-for-eu-3-and-sequential-enantioselective-sensing-of-malate-anion
#11
Xiaoyan Liu, Peng Wang, Jiaxin Fu, Kun Yao, Yongxin Chang, Kuoxi Xu
Novel phenanthroline Schiff base fluorescent sensors L1, L2, and D1 were designed and synthesized. The sensing abilities of the compounds in the presence of metal cations (Li+ , Na+ , K+ , Ag+ , Mg2+ , Ba2+ , Ca2+ , Mn2+ , Pb2+ , Hg2+ , Ni2+ , Zn2+ , Cd2+ , Co2+ , Cu2+ , Cr3+ , Fe3+ , Fe2+ , Al3+ , and Eu3+ ) were studied by UV-vis and fluorescent spectroscopy. The compounds L1, L2, and D1 could act as Eu3+ ion turn-off fluorescent sensors based on ligand-to-metal binding mechanism in DMSO-H2 O solution (v/v = 1:1, 10 mM Tris, pH = 7...
March 24, 2018: Chirality
https://www.readbyqxmd.com/read/29573466/functional-characterization-of-salt-tolerant-microbial-esterase-wdest17-and-its-use-in-the-generation-of-optically-pure-ethyl-r-3-hydroxybutyrate
#12
Yilong Wang, Yongkai Xu, Yun Zhang, Aijun Sun, Yunfeng Hu
No abstract text is available yet for this article.
March 24, 2018: Chirality
https://www.readbyqxmd.com/read/29572966/solvent-polarity-effects-on-supramolecular-chirality-of-a-polyfluorene-thiophene-copolymer
#13
Takashi Hirahara, Masahiro Yoshizawa-Fujita, Yuko Takeoka, Masahiro Rikukawa
This study demonstrates the supramolecular chirality control of a conjugated polymer via solvent polarity. We designed and synthesized a chiral polyfluorene-thiophene copolymer having two different chiral side chains at the 9-position of the fluorene unit. Chiral cyclic and alkyl ethers with different polarities were selected as the chiral side chains. The sign of the circular dichroism spectra in the visible wavelength region was affected by the solvent system, resulting from the change of supramolecular structure...
March 23, 2018: Chirality
https://www.readbyqxmd.com/read/29569746/enantioselective-resolution-of-rac-terbutaline-and-evaluation-of-optically-pure-r-terbutaline-hydrochloride-as-an-efficient-anti-asthmatic-drug
#14
Huimin Beng, Hao Zhang, R Jayachandra, Junxiao Li, Jie Wu, Wen Tan
Terbutaline is a β2 -adrenoceptor agonist for the treatment of asthma and chronic obstructive pulmonary disease (COPD). Among the two isomers of terbutaline (TBT 2), R-isomer was found to be the potent enantiomer in generating therapeutic effect, while S-isomer has been reported to show side effects. In this study, R-terbutaline hydrochloride (R-TBH 6) was synthesized through chiral resolution from the racemic terbutaline sulfate (rac-TBS 1) with 99.9% enantiomeric excess (ee) in good overall yield (53.6%)...
March 23, 2018: Chirality
https://www.readbyqxmd.com/read/29528520/isothermal-titration-calorimetry-for-chiral-chemistry
#15
REVIEW
Liora Werber, Yitzhak Mastai
One of the most powerful techniques that are currently available to measure thermodynamic parameters such as enthalpy (ΔH), Gibbs free energy (ΔG), entropy changes (ΔS), and binding affinity in chemical reactions is isothermal titration calorimetry (ITC). Recent advances in instrumentation have facilitated the development of ITC as a very essential analytical tool in biology and chemistry. In this article, we will focus on a review of the literature on the application of ITC for the study of chiral systems and chiral interactions...
March 12, 2018: Chirality
https://www.readbyqxmd.com/read/29528517/enantioselective-behaviour-of-tetraconazole-during-strawberry-wine-making-process
#16
Na Liu, Xinglu Pan, Shuang Zhang, Mingshan Ji, Zhihong Zhang
The fate of tetraconazole enantiomers in strawberries during wine-making process was studied. The residues were determined by ultra-performance convergence chromatography tandem triple quadrupole mass spectrometry after each process steps. Results indicated that there was significant enantioselective dissipation of tetraconazole enantiomers during the fermentation process. And (-)-tetraconazole degraded faster than (+)-tetraconazole. The half-lives of (-)-tetraconazole and (+)-tetraconazole were 3.12, 3.76 days with washing procedure and 3...
March 12, 2018: Chirality
https://www.readbyqxmd.com/read/29528512/computational-studies-on-the-water-catalyzed-stereoinversion-mechanism-of-glutamic-acid-residues-in-peptides-and-proteins
#17
Tomoki Nakayoshi, Koichi Kato, Shuichi Fukuyoshi, Ohgi Takahashi, Eiji Kurimoto, Akifumi Oda
No abstract text is available yet for this article.
March 12, 2018: Chirality
https://www.readbyqxmd.com/read/29528511/structural-analysis-of-lysine-4-methylated-histone-h3-proteins-using-synchrotron-radiation-circular-dichroism-spectroscopy
#18
Yudai Izumi, Koichi Matsuo, Hirofumi Namatame
We report structural alterations of histone H3 proteins induced by lysine-4 (K4) monomethylation, dimethylation, and trimethylation identified by using synchrotron radiation circular dichroism spectroscopy. Compared with unmethylated H3, monomethylation and dimethylation induced increases in α-helix structures and decreases in β-strand structures. In contrast, trimethylation decreased α-helix content but increased β-strand content. The structural differences among K4-unmethylated/methylated H3 may allow epigenetic enzymes to discriminate the substrates both chemically and sterically...
March 12, 2018: Chirality
https://www.readbyqxmd.com/read/29520869/circularly-polarized-luminescence-of-helically-assembled-pyrene-%C3%AF-stacks-on-rna-and-dna-duplexes
#19
Mitsunobu Nakamura, Fuyuki Ota, Tadao Takada, Kazuo Akagi, Kazushige Yamana
In this report, we describe the circularly polarized luminescence (CPL) of the RNA duplexes having one to four 2'-O-pyrene modified uridines (Upy) and the DNA duplexes having two, four, and six pyrene modified non-nucleosidic linkers (Py). Both the pyrene π-stack arrays formed on the RNA and DNA double helical structures exhibited pyrene excimer fluorescence. In the pyrene-modified RNA systems, the RNA duplex having four Upys gives CPL emission with glum value of <0.01 at 480 nm. The structure of pyrene stacks on the RNA duplex may be rigidly regulated with increase in the Upy domains, which resulted in the CPL emission...
March 9, 2018: Chirality
https://www.readbyqxmd.com/read/29498440/molecular-enantiorecognition-of-l-glucose-and-d-glucose-in-whole-blood-samples
#20
Raluca-Ioana Stefan-van Staden, Grigorina Mitrofan
In the past years, enantioanalysis became very important for clinical analysis; biomarkers/substances of biomedical importance with chiral structure should be analyzed and their presence correlated with the specific disorder. Therefore, we developed a method for the assay of l- and d-glucose, based on molecular recognition of l- and d-glucose. While for d-glucose there are many methods to assess its quantity, the l-enantiomer is not routinely detected by standard methods. Two stochastic microsensors based on the immobilization of Copper(II)phthalocyanine and Ni(II)phthalocyanine, in natural diamond powder, were proposed for the enantioanalysis of glucose...
March 2, 2018: Chirality
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