bluuebunny/crossref_metadata_2025_split huggingface dataset:
Simultaneous recovery of Ni and Co from scrap mobile phone battery by acid leaching process
Authors: Sakultung S. , Pruksathorn K. , Hunsom M. 
Published: July 2008

AbstractThis research was carried out to recover some valuable metals from the electrodes of the scrap mobile phone batteries by using the leaching process in the laboratory. Two types of scrap mobile phone batteries were used in this study: nickel‐metal hydride (Ni–MH) and lithium‐ion batteries (Li–ion). Both batteries were first crushed and their principal components were analyzed. Subsequently leaching was carried out. For simultaneous recovery of both metals, the preliminary results indicated that H2SO4 provided better leaching than HNO3 under the same conditions. The optimum leaching was at an acid concentration of 2.5 M, leaching temperature of 70 °C, solid–liquid ratio of 15 g/l, and leaching time of 60 min. Under these conditions, approximately 95% of nickel (Ni) and 59% of cobalt (Co) were leached. The presence of a reducing agent such as H2O2 had very little effect on the leaching efficiency of both metals. The leaching process of both the metals was a second‐order reaction of the metal concentration in the solution. Copyright © 2008 Curtin University of Technology and John Wiley & Sons, Ltd.
Optimizing separator pressures in the multistage crude oil production unit
Authors: Bahadori Alireza , Vuthaluru Hari B. , Mokhatab Saeid 
Published: July 2008

AbstractTo achieve good separation between gas and liquid mixture coming out of a crude oil production system and to maximize hydrocarbon liquid recovery, it is necessary to use several separation stages at decreasing pressures and then adapting the pressure set‐points to improve product separation and recovery at minimum cost. The aim of this study is to present an accurate methodology for optimizing separator pressures in the crude oil production unit. The new proposed methodology determines the optimum pressures of separators in different stages of separation and consequently optimizes the operating conditions. Using this new method, the optimum separator pressures for a 5724‐m3/day oil production unit were determined. As a result, the oil recovery was increased by 6 and 5 m3/day during summer and winter seasons, respectively. In this work, the C7 + fraction was also treated as one cut and then breakdown of heavy fraction cuts (C7 + splitting) with respect to the most widely used distribution function (gamma probability function). The results obtained showed that the calculations with C7 + fraction breakdown is more accurate than definition of feed stream a with single C7 + fraction. Copyright © 2008 Curtin University of Technology and John Wiley & Sons, Ltd.
Mutational analysis of SHH and GLI3 in anorectal malformations
Authors: Garcia‐Barceló Maria‐Mercè , Chi‐Hang Lui Vincent , Miao Xiaoping , So Man‐ting , Yuk‐yu Leon Thomas , Yuan Zhen‐wei , Li Long , Liu Lei , Wang Bin , Sun Xiao‐bing , Huang Liu‐ming , Tou Jin‐fa , Sau‐wai Ngan Elly , Cherny Stacey S. , Chan Kin‐wai , Lee Kim‐hung , Wang Weiling , Kak‐yuen Wong Kenneth , Kwong‐hang Tam Paul 
Published: July 2008

AbstractBACKGROUND:Anorectal malformations (congenital absence of the anal opening) are among the most common pediatric surgical problems and carry a significant chronic morbidity.METHODS:Direct sequencing was used to screen 88 anorectal malformations patients for mutations and polymorphisms in SHH and GLI3. These genes were chosen according to the phenotype presented by mutant mice and their expression patterns.RESULTS:We report on 10 GLI3 variants (IVS3+141C>G, T183A, IVS4+124T>C, IVS7+17G>A, IVS8+1 G>C, N503N, P941P, P998L, A1005A, A1039A) and four SHH mutation/variants (IVS1‐49C>T, IVS2+111A>C, L214L, G290D).CONCLUSIONS:These variants are not over‐represented in the healthy population and most are predicted to be benign. This study conveys the problematic assessment of the pathogenic role in disease of rare point mutations and variants. Birth Defects Research (Part A) 82:644–648, 2008. © 2008 Wiley‐Liss, Inc.
Optimization and validation of a reporter gene assay for screening of phosphodiesterase inhibitors in a high throughput system
Authors: Nanda Kamna , Chatterjee Mou , Arya Ranjana , Mukherjee Shohini , Saini Kulvinder Singh , Dastidar Sunanda , Ray Abhijit 
Published: July 2008

AbstractPhosphodiesterases (PDEs) hydrolyze cyclic nucleotides, cyclic adenosine monophosphate (cAMP) and guanosine monophosphate (cGMP) into inactive 5' monophosphates, and exist as 11 families. Inhibitors of PDEs allow the elevation of cAMP and cGMP, which leads to a variety of cellular effects including airway smooth muscle relaxation and inhibition of cellular inflammation or of immune responses. PDE4 inhibitors specifically prevent the hydrolysis of cAMP. We have validated the manually developed reporter gene assay in a high‐throughput screening format that allows for fast and cost‐effective identification of potential inhibitors of PDE4 isozymes. The assay is sensitive and robust, with a Z' value of >0.5. The assay is also amenable to 384‐well format.
RNA‐driven cyclin‐dependent kinase regulation: When CDK9/cyclin T subunits of P‐TEFb meet their ribonucleoprotein partners
Authors: Michels Annemieke A. , Bensaude Olivier 
Published: July 2008

AbstractThe positive transcription elongation factor (P‐TEFb) consists of CDK9, a cyclin‐dependent kinase and its cyclin T partner. It is required for transcription of most class II genes. Its activity is regulated by non‐coding RNAs. The 7SK cellular RNA turns the HEXIM cellular protein into a P‐TEFb inhibitor that binds its cyclin T subunit. Thus, P‐TEFb activity responds to variations in global cellular transcriptional activity and to physiological conditions linked to cell differentiation, proliferation or cardiac hypertrophy. In contrast, the Tat activation region RNA plays an activating role. This feature at the 5' end of the human immunodeficiency (HIV) viral transcript associates with the viral protein Tat that in turn binds cyclin T1 and recruits active P‐TEFb to the HIV promoter. This results in enhanced P‐TEFb activity, which is critical for an efficient production of viral transcripts. Although discovered recently, the regulation of P‐TEFb becomes a paradigm for non‐coding RNAs that regulate transcription factors. It is also a unique example of RNA‐driven regulation of a cyclindependent kinase.
Structure‐activity relationship and metabolic stability studies of backbone cyclization and N‐methylation of melanocortin peptides
Authors: Linde Yaniv , Ovadia Oded , Safrai Eli , Xiang Zhimin , Portillo Federico P. , Shalev Deborah E. , Haskell‐Luevano Carrie , Hoffman Amnon , Gilon Chaim 
Published: July 2008

AbstractBackbone cyclization (BC) and N‐methylation have been shown to enhance the activity and/or selectivity of biologically active peptides and improve metabolic stability and intestinal permeability. In this study, we describe the synthesis, structure‐activity relationship (SAR) and intestinal metabolic stability of a backbone cyclic peptide library, BL3020, based on the linear α‐Melanocyte stimulating hormone analog Phe‐D‐Phe‐Arg‐Trp‐Gly. The drug lead, BL3020‐1, selected from the BL3020 library (compound 1) has been shown to inhibit weight gain in mice following oral administration. Another member of the BL3020 library, BL3020‐17, showed improved biological activity towards the mMC4R, in comparison to BL3020‐1, although neither were selective for MC4R or MC5R. N‐methylation, which restrains conformational freedom while increasing metabolic stability beyond that which is imparted by BC, was used to find analogs with increased selectivity. N‐methylated backbone cyclic libraries were synthesized based on the BL3020 library. SAR studies showed that all the N‐methylated backbone cyclic peptides demonstrated reduced biological activity and selectivity for all the analyzed receptors. N‐methylation of active backbone cyclic peptides destabilized the active conformation or stabilized an inactive conformation, rendering the peptides biologically inactive. N‐methylation of backbone cyclic peptides maintained stability to degradation by intestinal enzymes. © 2008 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 90: 671–682, 2008.This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Development of a simultaneous liquid–liquid extraction and chiral derivatization method for stereospecific GC‐MS analysis of amphetamine‐type stimulants in human urine using fractional factorial design
Authors: Aasim W. R. Wan , Gan S. H. , Tan S. C. 
Published: July 2008

AbstractA stereospecific gas chromatography–mass spectrometry analysis method for amphetamine‐type stimulants in human urine was recently developed. For maximum efficiency, liquid–liquid extraction and chiral derivatization of the analytes using (R)‐(−)‐α‐methoxy‐α‐(trifluoromethyl)phenylacetyl chloride were performed simultaneously. The effects of (1) use of saturated sodium chloride in 2.0msodium hydroxide, (2) extraction solvent volume, (3) percentage of triethylamine, (4) derivatization reagent volume, (5) sample mixing time, (6) incubation temperature and (7) incubation time on method sensitivity and variability were assessed using a two‐level, eight‐run Plackett–Burman design followed by a fold‐over design. The use of saturated sodium chloride solution and the derivatization reagent volume were significant factors (ANOVA,p< 0.01). The saturated sodium chloride solution decreased sensitivity whereas an increased volume of derivatization reagent increased sensitivity. Calibration curves for all analytes were linear between 5 and 500 µg/L, with correlation coefficients of >0.99. Detection limits were ≤2.3 µg/L and quantitation limits ≤7.7 µg/L. Reproducibility was good, with relative standard deviation values at <20%. Recovery exceeded 100% for most analytes. The experimental design enabled easy and rapid identification of significant factors using a minimal number of samples. This method has good potential for studies requiring rapid and sensitive stereospecific quantification of amphetamine‐type stimulants. Copyright © 2008 John Wiley & Sons, Ltd.
Influence of δ‐Functional Groups on the Enantiorecognition of Secondary Alcohols by Candida antarctica Lipase B
Authors: Nyhlén Jonas , Martín‐Matute Belén , Sandström Anders G. , Bocola Marco , Bäckvall Jan‐E. 
Published: July 2008

AbstractThe selectivity of acetylation of δ‐functionalized secondary alcohols catalyzed by Candida antarctica lipase B has been examined by molecular dynamics. The results from the simulation show that a δ‐alcohol functionality forms a hydrogen bond with the carbonyl group of Thr 40. This interaction stabilizes the tetrahedral intermediate and thus leads to selective acetylation of the R enantiomer. A stabilizing interaction of the δ‐(R)‐acetoxy group with the peptide NH of alanine 282 was also observed. No stabilizing interaction could be found for the δ‐keto functionality, and it is proposed that this is the reason for the experimentally observed decrease in enantioselectivity. From these results, it was hypothesized that the enantioselectivity could be restored by mutating the alanine in position 281 for serine. The mutation was made experimentally, and the results show that the E value increased from 9 to 120.
3‐Methylarginine from Pseudomonas syringae pv. syringae 22d/93 Suppresses the Bacterial Blight Caused by Its Close Relative Pseudomonas syringae pv. glycinea
Authors: Braun Sascha D. , Völksch Beate , Nüske Jörg , Spiteller Dieter 
Published: July 2008

AbstractThe epiphyte Pseudomonas syringae pv. syringae 22d/93 (Pss22d) produces a toxin that strongly inhibits the growth of its relative, the plant pathogen P. syringae pv. glycinea. The inhibition can be overcome by supplementing the growth medium with the essential amino acid, L‐arginine; this suggests that the toxin acts as an inhibitor of the arginine biosynthesis. The highly polar toxin was purified by bioassay‐guided fractionation using ion‐exchange chromatography and subsequent RP‐HPLC fractionation. The structure of the natural product was identified by HR‐ESI‐MS, HR‐ESI‐MS/MS, and NMR spectroscopy experiments as 3‐methylarginine. This amino acid has previously only been known in nature as a constituent of the peptide lavendomycin from Streptomyces lavendulae. Results of experiments in which labeled methionine was fed to Pss22d indicated that the key step in the biosynthesis of 3‐methylarginine is the introduction of the methyl group by a S‐adenosylmethionine (SAM)‐dependent methyltransferase. Transposon mutagenesis of Pss22d allowed the responsible SAM‐dependent methyltransferase of the 3‐methylarginine biosynthesis to be identified.
Oxidation of Guanine by Carbonate Radicals Derived from Photolysis of Carbonatotetramminecobalt(III) Complexes and the pH Dependence of Intrastrand DNA Cross‐Links Mediated by Guanine Radical Reactions
Authors: Crean Conor , Lee Young Ae , Yun Byeong Hwa , Geacintov Nicholas E. , Shafirovich Vladimir 
Published: July 2008

AbstractThe carbonate radical anion CO3.− is a decomposition product of nitrosoperoxycarbonate derived from the combination of carbon dioxide and peroxynitrite, an important biological byproduct of the inflammatory response. The selective oxidation of guanine in DNA by CO3.− radicals is known to yield spiroiminodihydantoin (Sp) and guanidinohydantoin (Gh) products, and also a novel intrastrand cross‐linked product: 5′‐d(CCATCG*CT*ACC), featuring a linkage between guanine C8 (G*) and thymine N3 (T*) atoms in the oligonucleotide (Crean et al., Nucleic Acids Res. 2008, 36, 742–755). Involvement of the T‐N3 (pKa of N3‐H is 9.67) suggests that the formation of 5′‐d(CCATCG*CT*ACC) might be pH‐dependent. This hypothesis was tested by generating CO3.− radicals through the photodissociation of carbonatotetramminecobalt(III) complexes by steady‐state UV irradiation, which allowed for studies of product yields in the pH 5.0–10.0 range. The yield of 5′‐d(CCATCG*CT*ACC) at pH 10.0 is ∼45 times greater than at pH 5.0; this is consistent with the proposed mechanism, which requires N3(H) thymine proton dissociation followed by nucleophilic addition to the C8 guanine radical.
Use of a Halogenase of Hormaomycin Biosynthesis for Formation of New Clorobiocin Analogues with 5‐Chloropyrrole Moieties
Authors: Heide Lutz , Westrich Lucia , Anderle Christine , Gust Bertolt , Kammerer Bernd , Piel Jörn 
Published: July 2008

AbstractThe depsipeptide antibiotic hormaomycin, which is produced by Streptomyces griseoflavus W‐384, contains a 5‐chloropyrrole moiety. In the producer strain we identified the gene hrmQ that shows sequence similarity to FADH2‐dependent halogenases. This gene was cloned and heterologously expressed in Streptomyces roseochromogenes var. oscitans DS12.976, which is the producer of the aminocoumarin antibiotic clorobiocin, which contains a 5‐methylpyrrole moiety. For the present experiment, we used a mutant of this strain in which the respective pyrrole‐5‐methyltransferase had been inactivated. Expression of the halogenase hrmQ in this mutant strain led to the formation of two new clorobiocin derivatives that carried a 5‐chloropyrrole moiety. These compounds were isolated on a preparative scale, their structures were elucidated by 1H NMR spectroscopy and mass spectrometry, and their antibacterial activity was determined. The substrate of HrmQ is likely to be a pyrrole‐2‐carboxyl‐S‐[acyl carrier protein] thioester. If this assumption is true, this study presents the first experiment in combinatorial biosynthesis that uses a halogenase that acts on an acyl carrier protein‐bound substrate.
Chiral recognition of ethers by NMR spectroscopy
Authors: Duddeck Helmut , Díaz Gómez Edison 
Published: July 2008

AbstractEnantiomers of chiral ethers and acetals are notoriously difficult to differentiate because their reactivity is low and they are poor donors to any Lewis acid or metal ion. As an exception, epoxides are somewhat better donors. This review describes the properties of ethers, explains NMR methods for their chiral recognition and describes successful examples of ether differentiation. The majority of literature reports deals with chiral lanthanide shift reagents and dirhodium tetracarboxylate complexes, which were used as enantiopure auxiliaries to create diastereomeric adducts with dispersed 1H and 13C NMR signals. The various methods are compared as to which is best suited for which purpose. Chirality, 2009. © 2008 Wiley‐Liss, Inc.
Gas‐phase enantioselective reactions in noncovalent ion‐molecule complexes
Authors: Speranza Maurizio , Gasparrini Francesco , Botta Bruno , Villani Claudio , Subissati Deborah , Fraschetti Caterina , Subrizi Fabiana 
Published: July 2008

AbstractNoncovalent diastereomeric ion‐molecule complexes are produced in the gas phase and are ideal for the study of chiral recognition in the absence of complicating solvent and counterion effects. This review article describes the state‐of‐art in this field with special emphasis on the most recent mass spectrometric studies of the structure, dynamics, and reactivity of diastereomeric ion/molecule aggregates. Chirality, 2009. © 2008 Wiley‐Liss, Inc.
A new water soluble Zn‐salophen derivative as a receptor for α‐aminoacids: Unexpected chiral discrimination
Authors: Dalla Cort Antonella , De Bernardin Paolo , Schiaffino Luca 
Published: July 2008

AbstractA new water soluble zinc‐salophen complex with appended D‐glucose moieties was synthesized and characterized. Its binding properties toward six aminoacids were investigated by UV‐vis spectrophotometric titrations. Association constants showed to be unfavorably affected by increasing steric hindrance of the side chain. Quite surprisingly, different association constants were measured for the L and D enantiomers. These data suggest that aminoacids are bound via two interactions, zinc‐carboxylate coordination and two hydrogen bonds between the ammonium group of the aminoacid and two oxygen atoms of one D‐glucose moiety. Such conclusion is supported by the result of semiempirical (PM3) calculations. Notably, the KL/KD value of 9.6 observed for the association of phenylalanine rivals with the highest values found for the chiral recognition of aminoacids in water. Chirality, 2009. © 2008 Wiley‐Liss, Inc.
Assessment of configurational and conformational properties of naringenin by vibrational circular dichroism
Authors: Abbate Sergio , Burgi Luigi Filippo , Castiglioni Ettore , Lebon France , Longhi Giovanna , Toscano Eleonora , Caccamese Salvatore 
Published: July 2008

AbstractThe electronic circular dichroism (ECD) and vibrational circular dichroism (VCD) spectra of both enantiomers of naringenin (4′,5,7‐trihydroxyflavanone) in acetonitrile solution have been measured. The enantiomers were obtained by chiral HPLC separation of the racemic sample. DFT calculations have been performed for relevant conformers and subsequent evaluations of VCD spectra are compared with VCD experiments: safe assignment of the absolute configuration is provided, based in particular on the VCD data. The relevance of the rotational conformers of the hydroxyl groups and of the mobility of phenol moiety is studied: based on this, we provide a first interpretation of the observed intense and broad couplet at 1325/1350 cm−1. Four conformers contribute to this pattern with different sign and amplitude as shown by DFT calculations. Time dependent DFT calculations have been performed and compared with ECD experimental data, under the same assumption of conformational properties and mobilities investigated by VCD. Chirality, 2009. © 2008 Wiley‐Liss, Inc.
Immobilization of (1S,2R)‐(+)‐2‐amino‐1,2‐diphenylethanol derivates on aminated silica gel with different linkages as chiral stationary phases and their enantioseparation evaluation by HPLC
Authors: Yin Chuan‐Qi , He Bao‐Jiang , Li Shi‐Rong , Liu Yong‐Qiong , Bai Zheng‐Wu 
Published: July 2008

AbstractA chiral selector was prepared through the reaction between (1S,2R)‐(+)‐2‐amino‐1,2‐diphenylethanol and phenyl isocyanate. This selector was immobilized on aminated silica gel, respectively, with bifunctional group linkers of 1,4‐phenylene diisocyanate, methylene‐di‐p‐phenyl diisocyanate, and terephthaloyl chloride to produce corresponding three chiral stationary phases. The prepared compounds and chiral stationary phases were characterized by FT‐IR, elemental analysis, 1H NMR, and solid‐state 1H NMR. The enantioseparation ability of these chiral stationary phases was evaluated with structurally various chiral compounds. The chiral stationary phase prepared with 1,4‐phenylene diisocyanate as linker showed excellent enantioseparation ability. The influence of different linkages on the enantioseparation was discussed. Chirality, 2009. © 2008 Wiley‐Liss, Inc.
Chemoenzymatic and microbial dynamic kinetic resolutions
Authors: Kamaruddin Azlina Harun , Uzir Mohamad Hekarl , Aboul‐Enein Hassan Y. , Halim Hairul Nazirah Abdul 
Published: July 2008

AbstractThis review tracks a decade of dynamic kinetic resolution developments with a biocatalytic inclination using enzymatic/microbial means for the resolution part followed by the racemization reactions either by means of enzymatic or chemocatalyst. These fast developments are due to the ability of the biocatalysts to significantly reduce the number of synthetic steps which are common for conventional synthesis. Future developments in novel reactions and products of dynamic kinetic resolutions should consider factors that are needed to be extracted at the early synthetic stage to avoid inhibition at scale‐up stage have been highlighted. Chirality, 2009. © 2008 Wiley‐Liss, Inc.
Asymmetric addition of phenylacetylene to aromatic ketones catalyzed by zinc or titanium complexes with chiral hydroxysulfonamide
Authors: Zhou Yi‐Feng , Han Zhi‐Jian , Qiu Li , Liang Jin‐Yan , Ren Feng‐Bo , Wang Rui 
Published: July 2008

AbstractVarious new chiral hydroxysulfonamide ligands (3a–3n, 4a–4d) were prepared. Compounds 3a, 3g, 3i, 3k–3n, 4a–4d could accelerate the reaction and reduce reaction time, and 3a, 3g, 3i, 3k–3n catalyzed the reaction without titanium. The results obtained were promising in terms of yields and enantiomeric excesses (3k up to 85% ee, 4a up to 83% ee). Chirality, 2009. © 2008 Wiley‐Liss, Inc.
Stereoselective plasma protein binding and target tissue distribution of clausenamide enantiomers in rats
Authors: Zhu Chuan Jiang , Zhang Jun Tian 
Published: July 2008

AbstractStereoselective differences in pharmacokinetics between clausenamide (CLA) enantiomers have been found after intravenous and oral administration of each enantiomer to rats. The differences could be associated with protein binding of CLA enantiomers. By equilibrium dialysis methods, the binding of CLA enantiomers to rat plasma protein was investigated. The results showed that mean percentages of (−) and (+)CLA in the bound form were 28.5% and 38.0%, respectively, indicating that the unbound fraction of (−)CLA was higher than that of (+)CLA, which provided an explanation for stereoselective pharmacokinetics of CLA enantiomers in rats. The results also showed that there were species differences in plasma protein binding of (−)‐isomer between rats (28.5%) and rabbits (47.2%). Furthermore, effects of plasma protein binding on the distribution of CLA enantiomers to their possible target tissues were observed. The amount of (−)CLA in brain was greater than that of (+)CLA 15 min after administration of each enantiomer to rats. But the results were reverse at 4 h postdose. Further studies in distributional kinetics showed that (−)CLA had a more rapid absorption and distribution to hippocampus, cortex, and cerebellum than (+) CLA. (+)CLA had greater values for Tmax, t1/2β, and AUC0→∞, and smaller ones for CL/F and Vd/F than its antipode. The data indicated that the distribution of (−) and (+)CLA in their target tissues was stereoselective. The stereoselective distribution might be involved in the metabolism and transport of two enantiomers in the central nerve system. Chirality, 2009. © 2008 Wiley‐Liss, Inc.