bluuebunny/crossref_metadata_2025_split huggingface dataset:
Verfahren zur Enantiomerentrennung
Authors: Lorenz Heike , Seidel‐Morgenstern Andreas 
Published: January 2014

AbstractDie Verfügbarkeit reiner Enantiomere ist von steigender Bedeutung für die pharmazeutische Industrie sowie auch für die Agrochemie und Biotechnologie. Generell gibt es zwei konkurrierende Ansätze zur Gewinnung von reinen Enantiomeren. Der “chirale” Ansatz basiert auf der Entwicklung einer asymmetrischen Synthese, die selektiv eines der Enantiomere liefert. Der “racemische” Ansatz basiert auf der Trennung eines Gemischs der beiden Enantiomere, wobei hier in den letzten Jahren bemerkenswerte Fortschritte erzielt werden konnten. Dieser Aufsatz fokussiert insbesondere auf enantioselektive Kristallisationsprozesse und präparative Chromatographie, einschließlich hybrider Trennprozesse und der zusätzlichen Integration von Racemisierungsschritten. Zur Illustration dienen mehrere in unserem Arbeitskreis untersuchte Trennungen.
Processes To Separate Enantiomers
Authors: Lorenz Heike , Seidel‐Morgenstern Andreas 
Published: January 2014

AbstractThe provision of pure enantiomers is of increasing importance not only for the pharmaceutical industry but also for agrochemistry and biotechnology. In general, there are two rival approaches to provide pure enantiomers. The “chiral” approach is based on developing an asymmetric synthesis of just one of the enantiomers, while the “racemic” approach is based on separating mixtures of the two enantiomers. In the last few years remarkable progress has been achieved in the latter area. This Review focuses in particular on enantioselective crystallization processes and preparative chromatography, including hybrid processes and the incorporation of racemization steps. Several examples from our research are used for illustration purposes.
Dynamic properties of star‐shaped, solution‐polymerized styrene–butadiene rubber and its cocoagulated rubber‐filled with silica/carbon black
Authors: Liu Xiao , Zhao Suhe , Yang Yong , Zhang Xingying , Wu Youping 
Published: January 2014

ABSTRACTThe dynamic properties, including the dynamic mechanical properties, flex fatigue properties, dynamic compression properties, and rolling loss properties, of star‐shaped solution‐polymerized styrene–butadiene rubber (SSBR) and organically modified nanosilica powder/star‐shaped styrene–butadiene rubber cocoagulated rubber (N‐SSBR), both filled with silica/carbon black (CB), were studied. N‐SSBR was characterized by 1H‐NMR, gel permeation chromatography, energy dispersive spectrometry, and transmission electron microscopy. The results show that the silica particles were homogeneously dispersed in the N‐SSBR matrix. In addition, the N‐SSBR/SiO2/CB–rubber compounds' high bound rubber contents implied good filler–polymer interactions. Compared with SSBR filled with silica/CB, the N‐SSBR filled with these fillers exhibited better flex fatigue resistance and a lower Payne effect, internal friction loss, compression permanent set, compression heat buildup, and power loss. The nanocomposites with excellent flex fatigue resistance showed several characteristics of branched, thick, rough, homogeneously distributed cross‐sectional cracks, tortuous flex crack paths, few stress concentration points, and obscure interfaces with the matrix. Accordingly, N‐SSBR would be an ideal matrix for applications in the tread of green tires. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40348.
Tailoring the crystalline morphologies and mechanical properties of high‐density polyethylene parts by a change in the fluid flow pattern under gas‐assisted injection molding
Authors: Zhang Quanping , Wang Long , Xia Xiaochao , Feng Jianmin , Fu Xiaorong , Yang Mingbo 
Published: January 2014

ABSTRACTIn this study, an increase in the cooling rate of high‐density polyethylene parts was carried out via a change in the fluid flow pattern to introduce gas cooling under a gas‐assisted injection‐molding process; this was conducive to the retention of orientation chains shaped during the injection stage and further developed into much more oriented crystals. Morphological observation showed that the parts without gas cooling (WOGC) were composed of oriented crystals except the gas channel zone, whereas the parts with gas cooling (WGC) were full of oriented crystals, especially much more interlocking shish‐kebab structures in the subskin zone. The WGC parts had a higher degree of orientation than the corresponding zone of the WOGC parts. Although the lower crystallinity, the wider orientation regions, and much more interlocking shish‐kebab structures led to considerable increases from 32 and 990 MPa in the WOGC parts to 36 and 1150 MPa in the WGC parts for the yield strength and elastic modulus, respectively. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40349.
Antitumor efficacy of doxorubicin encapsulated within PEGylated poly(amidoamine) dendrimers
Authors: Liao Huihui , Liu Hui , Li Yulin , Zhang Mengen , Tomás Helena , Shen Mingwu , Shi Xiangyang 
Published: January 2014

ABSTRACTWe report here a general approach to using poly(amidoamine) (PAMAM) dendrimers modified with polyethylene glycol (PEG) as a platform to encapsulate an anticancer drug doxorubicin (DOX) for in vitro cancer therapy applications. In this approach, PEGylated PAMAM dendrimers were synthesized by conjugating monomethoxypolyethylene glycol with carboxylic acid end group (mPEG‐COOH) onto the surface of generation 5 amine‐terminated PAMAM dendrimer (G5.NH2), followed by acetylation of the remaining dendrimer terminal amines. By varying the molar ratios of mPEG‐COOH/G5.NH2, G5.NHAc‐mPEGn (n = 5, 10, 20, and 40, respectively) with different PEGylation degrees were obtained. We show that the PEGylated dendrimers are able to encapsulate DOX with approximately similar loading capacity regardless of the PEGylation degree. The formed dendrimer/DOX complexes are water soluble and stable. In vitro release studies show that DOX complexed with the PEGylated dendrimers can be released in a sustained manner. Further cell viability assay in conjunction with cell morphology observation demonstrates that the G5.NHAc‐mPEGn/DOX complexes display effective antitumor activity, and the DOX molecules encapsulated within complexes can be internalized into the cell nucleus, similar to the free DOX drug. Findings from this study suggest that PEGylated dendrimers may be used as a general drug carrier to encapsulate various hydrophobic drugs for different therapeutic applications. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40358.
Rheological and thermal properties of saponified cassava starch‐g‐poly(acrylamide) superabsorbent polymers varying in grafting parameters and absorbency
Authors: Parvathy Prabha C. , Jyothi Alummoottil. N. 
Published: January 2014

ABSTRACTCassava starch‐graft‐poly(acrylamide) superabsorbent polymers (SAPs) with varying absorbencies were synthesized. Weight average molecular weight (Mw) of the hydrolyzed starch‐graft‐copolymers ranged from 1.6 × 106to 2.8 × 106g/mol, the largest being shown by the sample with highest percentage grafting. The storage (G′) and loss modulus (G″) of hydrogels were determined as a function of frequency.G″ was larger thanG′ for the hydrogels with higher absorbencies and exhibited a liquid‐like behavior. However, hydrogels with lower absorbencies showed a reverse viscoelastic behavior. The viscosity of hydrogels determined using a Brookfield viscometer at different shear rates was found to be larger for the hydrogels with higher absorbencies. The melting temperature (Tm) and enthalpy change of fusion (ΔHf) of the SAPs ranged from 149.7 to 177.7°C and 65 to 494.9 J/g, respectively and showed a positive correlation with grafting parameters andMw. Heavy metal ion removal capacity of hydrogel followed the order Cu2+ > Pb2+ > Zn2+. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2014,131, 40368.
Transition‐Metal‐Catalyzed CS Bond Coupling Reaction
Authors: Lee Chin‐Fa , Liu Yi‐Chen , Badsara Satpal Singh 
Published: January 2014

AbstractSulfur‐containing molecules such as thioethers are commonly found in chemical biology, organic synthesis, and materials chemistry. While many reliable methods have been developed for preparing these compounds, harsh reaction conditions are usually required in the traditional methods. The transition metals have been applied in this field, and the palladium‐catalyzed coupling of thiols with aryl halides and pseudo halides is one of the most important methods in the synthesis of thioethers. Other metals have also been used for the same purpose. Here, we summarize recent efforts in metal‐catalyzed CS bond cross‐coupling reactions, focusing especially on the coupling of thiols with aryl‐ and vinyl halides based on different metals.
Fluorescence enhancement of europium (III) perchlorate by 1,10‐phenanthroline on the 1‐(naphthalen‐2‐yl)‐2‐(phenylsulthio)ethanone complex and luminescence mechanism
Authors: Li Wen‐Xian , Xin Xiao‐Dong , Feng Shu‐Yan , Liu Yu , Zhang Jing , Ao Bo‐Yang , Li Ying‐Jie 
Published: January 2014

ABSTRACTA novel ligand, 1‐(naphthalen‐2‐yl)‐2‐(phenylsulthio)ethanone was synthesized using a new method and its two europium (Eu) (III) complexes were synthesized. The compounds were characterized by elemental analysis, coordination titration analysis, molar conductivity, infrared, thermo gravimetric analyzer‐differential scanning calorimetry (TGA‐DSC), 1H NMR and UV spectra. The composition was suggested as EuL5 · (ClO4)3 · 2H2O and EuL4 · phen(ClO4)3 · 2H2O (L = C10H7COCH2SOC6H5). The fluorescence spectra showed that the Eu(III) displayed strong characteristic metal‐centered fluorescence in the solid state. The ternary rare earth complex showed stronger fluorescence intensity than the binary rare earth complex in such material. The strongest characteristic fluorescence emission intensity of the ternary system was 1.49 times as strong as that of the binary system. The phosphorescence spectra were also discussed. Copyright © 2014 John Wiley & Sons, Ltd.
Unique Crystal Structure of a Novel Surfactant Protein from the Foam Nest of the Frog Leptodactylus vastus
Authors: Cavalcante Hissa Denise , Arruda Bezerra Gustavo , Birner‐Gruenberger Ruth , Paulino Silva Luciano , Usón Isabel , Gruber Karl , Maciel Melo Vânia Maria 
Published: January 2014

AbstractBreeding by releasing eggs into stable biofoams (“foam nests”) is a peculiar reproduction mode within anurans, fish, and tunicates; not much is known regarding the biochemistry or molecular mechanisms involved. Lv‐ranaspumin (Lv‐RSN‐1) is the predominant protein from the foam nest of the frog Leptodactylus vastus. This protein shows natural surfactant activity, which is assumed to be crucial for stabilizing foam nests. We elucidated the amino acid sequence of Lv‐RSN‐1 by de novo sequencing with mass‐spectrometry and determined the high‐resolution X‐ray structure of the protein. It has a unique fold mainly composed of a bundle of 11 α‐helices and two small antiparallel β‐strands. Lv‐RSN‐1 has a surface rich in hydrophilic residues and a lipophilic cavity in the region of the antiparallel β‐sheet. It possesses intrinsic surface‐active properties, reducing the surface tension of water from 73 to 61 mN m−1 (15 μg mL−1). Lv‐RSN‐1 belongs to a new class of surfactants proteins for which little has been reported regarding structure or function.
Tuning the Selectivity in the Aerobic Oxidation of Cumene Catalyzed by Nitrogen‐Doped Carbon Nanotubes
Authors: Liao Shixia , Chi Yumei , Yu Hao , Wang Hongjuan , Peng Feng 
Published: January 2014

AbstractIn this study it is demonstrated that carbon nanotubes (CNTs) with doped nitrogen atoms in graphitic domains (NCNTs) can act as a new class of metal‐free catalysts exhibiting excellent activity in the aerobic oxidation of cumene. We proved that NCNTs can promote the decomposition of hydroperoxide cumene with exceptionally high activity, resulting in strongly increased cumene conversion and extraordinarily high selectivity to acetophenone and 2‐benzyl‐2‐propanol. The incorporation of nitrogen altered the surface electron structure of the CNTs and tuned the reactivity and selectivity. DFT calculations revealed that the remarkable improvement of catalytic performance of NCNTs is caused by the strong interaction between hydroperoxide cumene and the NCNTs. NCNTs also exhibited desirable recyclability after four cycling tests. This study not only provides a novel method for the cumene oxidation to high‐value‐added products at moderate reaction temperatures and oxygen atmospheric pressure, but also gives new insights into the effect of surface nitrogen doping on carbon‐catalyzed liquid‐phase oxidation of aromatic hydrocarbons.
Whole‐Cell Carboxylate Reduction for the Synthesis of 3‐Hydroxytyrosol
Authors: Napora‐Wijata Kamila , Robins Karen , Osorio‐Lozada Antonio , Winkler Margit 
Published: January 2014

Abstract3‐Hydroxytyrosol (3‐HT) is a phenolic antioxidant that has a number of beneficial effects on human health and is a valuable building block in the synthesis of various pharmaceuticals. Herein, we report a new method for the production of 3‐HT through reduction of 3,4‐dihydroxyphenylacetic acid. The reduction was performed in whole Escherichia coli BL21 (DE3) cells overexpressing carboxylic acid reductase from Nocardia and phosphopantetheinyl transferase from E. coli. An endogenous E. coli aldehyde reducing activity turned out to be highly efficient for further reduction of the aldehyde intermediate to the desired alcohol. The influence of different buffer components, cofactors, and cofactor recycling systems was investigated. A very economic combination of glucose, citrate, and air proved sufficient for recycling of the essential cofactors ATP and NAD(P)H. Selected crucial parameters were then further optimized within a “design of experiments” approach. Finally, first preparative‐scale bioreductions resulted in pure 3‐HT.
A Pyrimidopyrimidine Janus‐AT Nucleoside with Improved Base‐Pairing Properties to both A and T within a DNA Duplex: The Stabilizing Effect of a Second Endocyclic Ring Nitrogen
Authors: Largy Eric , Liu Wenbo , Hasan Abid , Perrin David M. 
Published: January 2014

AbstractJanus bases are heterocyclic nucleic acid base analogs that present two different faces able to simultaneously hydrogen bond to nucleosides that form Watson–Crick base pairs. The synthesis of a Janus‐AT nucleotide analogue, NJAT, that has an additional endocyclic ring nitrogen and is thus more capable of efficiently discriminating T/A over G/C bases when base‐pairing in a standard duplex‐DNA context is described. Conversion to a phosphoramidite ultimately afforded incorporation into an oligonucleotide. In contrast to the first generation of carbocyclic Janus heterocycles, it remains in its unprotonated state at physiological pH and, therefore, forms very stable Watson–Crick base pairs with either A or T bases. Biophysical and computational methods indicate that NJAT is an improved candidate for sequence‐specific genome targeting.
Enzyme Design from the Bottom Up: An Active Nickel Electrocatalyst with a Structured Peptide Outer Coordination Sphere
Authors: Reback Matthew L. , Buchko Garry W. , Kier Brandon L. , Ginovska‐Pangovska Bojana , Xiong Yijia , Lense Sheri , Hou Jianbo , Roberts John A. S. , Sorensen Christina M. , Raugei Simone , Squier Thomas C. , Shaw Wendy J. 
Published: January 2014

AbstractCatalytic, peptide‐containing metal complexes with a well‐defined peptide structure have the potential to enhance molecular catalysts through an enzyme‐like outer coordination sphere. Here, we report the synthesis and characterization of an active, peptide‐based metal complex built upon the well‐characterized hydrogen production catalyst [Ni(PPh2NPh)2]2+ (PPh2NPh=1,3,6‐triphenyl‐1‐aza‐3,6‐diphosphacycloheptane). The incorporated peptide maintains its β‐hairpin structure when appended to the metal core, and the electrocatalytic activity of the peptide‐based metal complex (≈100,000 s−1) is enhanced compared to the parent complex ([Ni(PPh2NAPPA)2]2+; ≈50,500 s‐1). The combination of an active molecular catalyst with a structured peptide provides a scaffold that permits the incorporation of features of an enzyme‐like outer‐coordination sphere necessary to create molecular electrocatalysts with enhanced functionality.
HPLC‐PDA‐ORD Bioassay of S‐(+) and R‐(−) Clopidogrel on Rat Dried Blood Spots
Authors: Nageswara Rao Ramisetti , Prasad Katuri Guru , Bindu Priya Pullakandam , Bijarji Shriharsh 
Published: January 2014

ABSTRACTA simple and rapid chiral high‐performance liquid chromatography (HPLC) method was developed and validated for bioanalysis of clopidogrel enantiomers on rat dried blood spots (DBS). Clopidogrel enantiomers were extracted from DBS using ethanol: methanol (80:20, v/v) and separated on a Chiralcel OJ‐H column containing cellulose tris (4‐methly benzoate) as a polysaccharide stationary phase using n‐hexane–ethanol‐diethylamine (70:30, 0.1 v/v) as a mobile phase at a flow rate of 1.0 mL/min. The detection was carried out at 220 nm using a photodiode array (PDA) detector while the elution order of the enantiomers was determined by a polarimeter connected to PDA in series. The effect of hematocrit on extraction of clopidogrel enantiomers from DBS was evaluated and no interference from endogenous substances was noticed. The overall accuracy of (R) and (S) enantiomers of clopidogrel from DBS were 91.6 and 89.2%, respectively. The calibration curves were linear over the concentration range of 1–500 µg/mL for both enantiomers. The results show that the method is specific, precise, and reproducible (intra‐ and interday precision relative standard deviations (RSDs) <10.0%). The stability of racemic clopidogrel was performed under all storage conditions and the results were found to be well within the acceptance limits. Chirality 26:102–107, 2014.© 2014 Wiley Periodicals, Inc.
Adsorption of Racemic Pharmaceuticals on Nano‐Scale Substrates
Authors: Bolten Dennis , Staudt Reiner , Türk Michael 
Published: January 2014

AbstractEine neue Prozessidee zur Auftrennung racemischer Wirkstoffe unter Verwendung nanoskaliger AlO(OH)‐Hohlkugeln als Adsorbens und überkritischen Kohlenstoffdioxides (sc‐CO2) als Lösungsmittel wird vorgestellt. Zur Auslegung des Prozesses werden Untersuchungen zur Abscheidung der racemischen Wirkstoffe (RS)‐Flurbiprofen, (RS)‐Ibuprofen, (RS)‐Ketoprofen und den reinen Enantiomeren (R)‐Flurbiprofen, (S)‐Ibuprofen und (S)‐Ketoprofen an AlO(OH)‐Hohlkugeln präsentiert und bewertet. Zudem werden Adsorptionsdaten von gasförmigem CO2 an den Hohlkugeln und kommerziellen AlO(OH)‐Partikeln, die mit einer Magnetschwebewaage ermittelt wurden, verglichen. Abschließend werden erste Ergebnisse von orientierenden Versuchen zur Adsorption von racemischem Flurbiprofen aus sc‐CO2 an den Hohlkugeln vorgestellt.
Removal of Hg(II) and CH3Hg(I) Using Rasped Pith Sago Residue Biosorbent
Authors: Saman Norasikin , Johari Khairiraihanna , Tien Song Shiow , Mat Hanapi 
Published: January 2014

AbstractRasped pith sago residue (RPSR) was used as a biosorbent for inorganic (Hg(II)) and organic (CH3Hg(I)) mercury removal from aqueous solutions. In biosorbent preparation, the RPSR having particle size range of 0.06–0.10 was washed with deionized water repeatedly to eliminate impurities, dried in an oven at 50°C for two days, followed with drying in a vacuum oven for 3 h. The performance of RPSR as a novel biosorbent for removing mercury was evaluated in batch adsorption. The adsorption of mercury ions was found to highly dependent on the pH of the solutions. The Hg(II) adsorption was high at pH > 4, while the CH3Hg(I) adsorption was found higher at pH < 5. The higher adsorption capacity for Hg(II) and CH3Hg(I) was 0.288 and 0.213 mmol/g, respectively. Both mercury adsorptions equilibrium and kinetics were fitted to the Langmuir isotherm model and pseudo‐second‐order kinetic model, respectively. These results indicate the RPSR has a potential to be a low‐cost biosorbent for mercury removal process from aqueous solutions.
A Chemical Tool for In Vitro and In Vivo Precipitation of Lysine Methyltransferase G9a
Authors: Konze Kyle D. , Pattenden Samantha G. , Liu Feng , Barsyte‐Lovejoy Dalia , Li Fengling , Simon Jeremy M. , Davis Ian J. , Vedadi Masoud , Jin Jian 
Published: January 2014

AbstractHere we report the design, synthesis, and biochemical characterization of a new chemical tool, UNC0965. UNC0965 is a biotinylated version of our previously reported G9a chemical probe, UNC0638. Importantly, UNC0965 maintains high in vitro potency and is cell penetrant. The biotinylated tag of UNC0965 enables “chemiprecipitation” of G9a from whole cell lysates. Further, the cell penetrance of UNC0965 allowed us to explore the localization of G9a on chromatin both in vitro and in vivo through chemical inhibitor‐based chromatin immunoprecipitation (chem‐ChIP).
On the Structures, Lifetimes, and Infrared Spectra of Alkylmercury Hydrides
Authors: Benidar Abdessamad , Montero‐Campillo M. Merced , Lamsabhi Al Mokhtar , Yáñez Manuel , Bouilloud Michaelle , Guillemin Jean‐Claude , Mó Otilia 
Published: January 2014

AbstractA series of six small alkylmercury hydrides of the general formula RHgH with R=methyl, ethyl,n‐propyl, isopropyl,n‐butyl, and 3‐butenyl were obtained by reduction in vacuo of the corresponding mercury halide with tributyltin hydride in the presence of a radical inhibitor. These very reactive compounds, which have to be removed from the reaction mixture as they are formed, were characterized by1H NMR and13C NMR spectroscopy. The IR spectra ofn‐propyl‐, isopropyl‐,n‐butyl‐, and 3‐butenylmercury hydride were recorded for the first time. All compounds were then studied by density functional theory calculations on the basis of a recent theoretical assessment for alkylmercury compounds performed by our group. Comparison of the experimental and theoretical results allowed the assignment of the vibrational modes in an unambiguous way, in spite of the low intrinsic stability of some of the derivatives investigated. The experimental procedure implemented for registering the IR spectra of these unstable species in the gas phase allowed us to obtain reasonable estimates of their lifetimes.