bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development and validation of a sensitive and specific LC–MS/MS cocktail assay for CYP450 enzymes: Application to study the effect of catechin on rat hepatic CYP activity
Authors: Nguyen Van , Espiritu Michael , Elbarbry Fawzy 
Published: December 2019

AbstractA sensitive and specific liquid chromatography tandem mass spectrometric (LC–MS/MS) method that enables the simultaneous quantification of probe substrates and metabolites of cytochrome P450 (CYP) enzymes was developed and validated. These substrates (metabolites)—coumarin (7‐hydroxycoumarin), tolbutamide (4‐hydroxytolbutamide), S‐mephenytoin (4‐hydroxymephenytoin), dextromethorphan (dextrorphan), and testosterone (6β‐hydroxytestosterone)—were utilized as markers for the activities of the major human CYP enzymes CYP2A6, CYP2C9, CYP2C19, CYP2D6, and CYP3A4, respectively. Analytes were separated on Kinetex C18 column (2.1 × 50 mm, 5 μm) using a binary gradient mobile phase of 0.1% formic acid in water and 0.1% formic acid in acetonitrile. Metabolites were detected and quantified by MS using multiple reaction monitoring at m/z 163 → 107.2 for 7‐hydroxycoumarin, m/z 235 → 150.1 for 4‐hydroxymephenytoin, m/z 287 → 171 for 4‐hydroxytolbutamide, m/z 258 → 157.1 for dextrorphan, m/z 305 → 269 for 6β‐hydroxytestosterone, and m/z 237 → 194 for the internal standard. The assay exhibited good linearity over a range of 10–500 ng/mL with acceptable accuracy and precision criteria.As a proof of concept, the developed cocktail assay was successfully used to examine the potential impact of catechin on the activity of the major rat liver CYP enzymes.
Stepwise Construction of Disulfides in Peptides
Authors: He Rongjun , Pan Jia , Mayer John P. , Liu Fa 
Published: December 2019

AbstractThe disulfide bond plays an important role in biological systems. It defines global conformation, and ultimately the biological activity and stability of the peptide or protein. It is frequently present, singly or multiply, in biologically important peptide hormones and toxins. Numerous disulfide‐containing peptides have been approved by the regulatory agencies as marketed drugs. Chemical synthesis is one of the prerequisite tools needed to gain deep insights into the structure–function relationships of these biomolecules. Along with the development of solid‐phase peptide synthesis, a number of methods of disulfide construction have been established. This minireview will focus on the regiospecific, stepwise construction of multiple disulfides used in the chemical synthesis of peptides. We intend for this article to serve a reference for peptide chemists conducting complex peptide syntheses and also hope to stimulate the future development of disulfide methodologies.
Tuning Enzyme Activity for Nonaqueous Solvents: Engineering an Enantioselective “Michaelase” for Catalysis in High Concentrations of Ethanol
Authors: Guo Chao , Biewenga Lieuwe , Lubberink Max , van Merkerk Ronald , Poelarends Gerrit J. 
Published: December 2019

AbstractEnzymes have evolved to function under aqueous conditions and may not exhibit features essential for biocatalytic application, such as the ability to function in high concentrations of an organic solvent. Consequently, protein engineering is often required to tune an enzyme for catalysis in non‐aqueous solvents. In this study, we have used a collection of nearly all single mutants of 4‐oxalocrotonate tautomerase, which promiscuously catalyzes synthetically useful Michael‐type additions of acetaldehyde to various nitroolefins, to investigate the effect of each mutation on the ability of this enzyme to retain its “Michaelase” activity in elevated concentrations of ethanol. Examination of this mutability landscape allowed the identification of two hotspot positions, Ser30 and Ala33, at which mutations are beneficial for catalysis in high ethanol concentrations. The “hotspot” position Ala33 was then randomized in a highly enantioselective, but ethanol‐sensitive 4‐OT variant (L8F/M45Y/F50A) to generate an improved enzyme variant (L8F/A33I/M45Y/F50A) that showed great ethanol stability and efficiently catalyzes the enantioselective addition of acetaldehyde to nitrostyrene in 40 % ethanol (permitting high substrate loading) to give the desired γ‐nitroaldehyde product in excellent isolated yield (89 %) and enantiopurity (ee=98 %). The presented work demonstrates the power of mutability‐landscape‐guided enzyme engineering for efficient biocatalysis in non‐aqueous solvents.
Nonprecious metal's graphene‐supported electrocatalysts for hydrogen evolution reaction: Fundamentals to applications
Authors: Ali Asad , Shen Pei Kang 
Published: December 2019

AbstractSustainable production of hydrogen is a hopeful requirement of a strategic future economy and development. Water splitting driven by electricity is a favorable pathway for renewable hydrogen production. This critical review highlighted recent efforts toward the development of the nanoscale synthesis of nonprecious metal's graphene‐supported electrocatalysts and their electrocatalytic features for remarkable hydrogen evolution reaction (HER). Different essential nonprecious metal's graphene‐supported electrocatalysts, including metal carbides, sulfides, phosphides, selenides, oxides, and nitrides are reviewed. In the exploration, attention is given to the strategies of activity enhancement, the synthetic approach, and the composition/structure electrocatalytic‐performance relationship of these HER electrocatalysts. We are hopeful that this review confers a new momentum to the rational design of remarkable performance nonprecious metal's graphene‐supported electrocatalysts and comprehensive guide for researchers to utilize the subject catalysts in regular water splitting.
Synthesis of β‐Glucosides with 3‐O‐Picoloyl‐Protected Glycosyl Donors in the Presence of Excess Triflic Acid: Defining the Scope
Authors: Mannino Michael P. , Demchenko Alexei V. 
Published: December 2019

AbstractExcellent β‐stereoselectivity for the glycosylation with glucosyl donors equipped with the 3‐O‐picoloyl (Pico) group, without the use of participating group, was achieved in the presence of NIS/excess TfOH promoter system. A complete investigation of the scope of this reaction was performed, revealing all important attributes of successful glycosylation. While altering the halogen source was tolerated, substitution of the triflate anion resulted in complete loss of stereoselectivity. Protonation of the Pico group was determined to be crucial in this reaction. The stability or extent of the protonated pyridine ring was also found to be another important key factor in obtaining high stereoselectivity. The nucleophilicity of the acceptor was found to be proportional to the stereoselectivity obtained, suggesting an SN2‐like mechanism.
Endohedral Metallofullerenes: New Structures and Unseen Phenomena
Authors: Shen Wangqiang , Hu Shuaifeng , Lu Xing 
Published: December 2019

AbstractEndohedral metallofullerenes (EMFs), namely fullerenes with metallic species encapsulated inside, represent an ideal platform to investigate metal–metal or metal–carbon interactions at the sub‐nanometer scale by means of single‐crystal X‐ray diffraction (XRD) crystallography. Herein, recent progress in the identification of new structures and unprecedented properties are discussed according to the categories of monometallofullerenes, dimetallofullerenes, carbide clusterfullerenes, and nitride clusterfullerenes. In particular, the dimerization and the cage‐isomer dependent oxidation state of the inner metal atom are summarized in terms of pristine monometallofullerenes. Metal–metal bonds involving lanthanide–lanthanides or actinide–actinides are discussed based on both experimental and theoretical studies. The cluster–cage matching and/or mutual selections, as well as the rarely seen M=C double bonds, are discovered in M2C2@C2n, U2C@C80, M2TiC@C80, and Ti3C3@C80. Subsequently, the geometries of different M3N clusters in various cages are discussed, revealing size‐matching between the internal M3N cluster and the outer cage induced by the planarity of the cluster. Finally, an outlook regarding the future developments of the molecular structures and applications of EMFs is presented.
An evaluation of MPI and OpenMP paradigms in finite‐difference explicit methods for PDEs on shared‐memory multi‐ and manycore systems
Authors: Cabral Frederico L. , Gonzaga de Oliveira Sanderson L. , Osthoff Carla , Costa Gabriel P. , Brandão Diego N. , Kischinhevsky Mauricio 
Published: December 2019

SummaryThis paper focuses on parallel implementations of three two‐dimensional explicit numerical methods on Intel® Xeon® Scalable Processor and the coprocessor Knights Landing. In this study, the performance of a hybrid parallel programming with message passing interface (MPI) and Open Multi‐Processing (OpenMP) and a pure MPI implementation used with two thread binding policies is compared with an improved OpenMP‐based implementation in three explicit finite‐difference methods for solving partial differential equations on shared‐memory multicore and manycore systems. Specifically, the improved OpenMP‐based version is a strategy that synchronizes adjacent threads and eliminates the implicit barriers of a naïve OpenMP‐based implementation. The experiments show that the most suitable approach depends on several characteristics related to the nonuniform memory access (NUMA) effect and load balancing, such as the size of the MPI domain and the number of synchronization points used in the parallel implementation. In algorithms that use four and five synchronization points, hybrid MPI/OpenMP approaches yielded better speedups than the other versions did in runs performed on both systems. The pure MPI‐based strategy, however, achieved better results than the other proposed approaches did in the method that employs only one synchronization point.
Efficient Synthesis of Arylenedioxy‐Bridged Porphyrin Dimers through Catalyst‐Free Nucleophilic Aromatic Substitution
Authors: Yamashita Ken‐ichi , Kuramochi Narumi , Pham Qui Van Hang , Furutani Kazuhiro , Ogawa Takuji , Sugiura Ken‐ichi 
Published: December 2019

AbstractA series of porphyrin dimers bridged by one or two rigid arylenedioxy linkers was successfully synthesized by catalyst‐free meso‐aryloxylation involving nucleophilic aromatic substitution. The orientational freedom and conformation of the two porphyrin macrocycles in the mono‐bridged dimers depended on the steric hindrance between the macrocycles and substituents on the arylenedioxy linkers. On the other hand, the bis‐bridged dimers exhibited a highly rigid cofacial conformation with a distinct interplanar distance. The fluorescence quantum yields of the bis‐bridged dimers (Φfl=0.094 and 0.096) were quite similar to those of the monomers (Φfl=0.13). Owing to their high rigidities, the nonradiative deactivation of the photoexcited states associated with dimerization, which are observed for reported dimers, are mostly suppressed, thus suggesting that those dimers have highest rigidities among the cofacial porphyrin dimers exploring emission properties. Cyclic voltammetry revealed the electronic communication between the porphyrin macrocycles in the closely stacked bis‐bridged dimer.
The impact of internal control, external assurance, and integrated reports on market value
Authors: Gal Graham , Akisik Orhan 
Published: December 2019

AbstractIt is generally assumed that the credibility of a firm's disclosure is enhanced when there is an independent review. This is the basis for the requirement that an independent audit firm attest to the veracity of financial statements. With the passage of Sarbanes‐Oxley, publicly‐traded North American firms must include a statement about the quality of their internal control system in their financial statements. While the audit of the statements of financial position may be considered to pertain only to that information, the internal control system has a pervasive effect. Therefore, its audit may also impact systems not directly related to financial reporting. Integrated reports combine financial and non‐financial information to provide an overall view of firm's performance. Using data from Compustat North America and GRI, this study shows a positive impact of internal control systems and integrated reports on market value.
Electrocatalytic Hydrogenation of Guaiacol in Diverse Electrolytes Using a Stirred Slurry Reactor
Authors: Wijaya Yanuar Philip , Grossmann‐Neuhaeusler Tobias , Dhewangga Putra Robertus Dhimas , Smith Kevin J. , Kim Chang Soo , Gyenge Előd L. 
Published: December 2019

AbstractElectrocatalytic hydrogenation (ECH) of guaiacol was performed in a stirred slurry electrochemical reactor (SSER) using 5 wt % Pt/C catalyst in the cathode compartment. Different pairs of acid (H2SO4), neutral (NaCl), and alkaline (NaOH) catholyte–anolyte combinations separated by a Nafion® 117 cation exchange membrane, were investigated by galvanostatic and potentiostatic electrolysis to probe the electrolyte and proton concentration effect on guaiacol conversion, product distribution, and Faradaic efficiency. The acid–acid and neutral–acid pairs were found to be the most effective. In the case of the neutral–acid pair, proton diffusion and migration through the membrane from the anolyte to the catholyte supplies the protons required for ECH. Typically, the two major hydrogenation products were cyclohexanol and 2‐methoxycyclohexanol. However, ECH at constant cathode superficial current density (−182 mA cm−2) and higher temperature (i.e., 60 °C) favored a pathway leading mainly to cyclohexanone. The guaiacol conversion routes were affected by temperature‐ and cathode potential‐dependent surface coverage of adsorbed hydrogen radicals generated through electroreduction of protons.
Photocatalysts for H2 Generation from Starburst Triphenylamine/Carbazole Donor‐Based Metal‐Free Dyes and Porous Anatase TiO2 Cube
Authors: Huang Jian‐Feng , Lei Yang , Xiao Li‐Min , Chen Xin‐Lun , Zhong Yu‐Hui , Qin Su , Liu Jun‐Min 
Published: December 2019

AbstractA series of novel triphenylamine/carbazole‐based D–D–π–π–A dyes DH1–4 and a mesoporous anatase cubic “microcage” TiO2 material (denoted as MC‐TiO2) were synthesized and combined to obtain dye‐sensitized photocatalysts (denoted as DHn/Pt/MC‐TiO2, n=1–4). These catalysts showed better performances in visible‐light‐driven H2 evolution from water than DHn/Pt/P25‐TiO2 catalysts based on commercial P25‐TiO2 bulk semiconductor under similar conditions. Compared with P25‐TiO2 particles, the porous MC‐TiO2 had a large Brunauer–Emmett–Teller surface area, porosity, and exposed {0 0 1} crystal plane, which greatly contributed to the photocatalytic activity. The optimized DH2/Pt/MC‐TiO2 photocatalyst exhibited an attractive H2 production rate (16.28 mmol g−1 h−1 based on catalyst mass), and the optimized DH4/Pt/MC‐TiO2 photocatalyst showed good stability [turnover number (TON) of 16 699 in 105 h based on dye number], which represents one of the best performances among all reported visible‐light‐driven heterogeneous catalytic systems. Compared with the other dyes in this series, the high H2 production rate of DH2 on Pt/MC‐TiO2 can be attributed to its size‐matching effect and thus high dye loading amount, whereas the high TON and durability of DH4/Pt/MC‐TiO2 are probably related to the rapid regeneration kinetics of DH4.
Chemicals from Lignin: A Review of Catalytic Conversion Involving Hydrogen
Authors: Jing Yaxuan , Dong Lin , Guo Yong , Liu Xiaohui , Wang Yanqin 
Published: December 2019

AbstractLignin is the most abundant biopolymer with aromatic building blocks and its valorization to sustainable chemicals and fuels has extremely great potential to reduce the excessive dependence on fossil resources, although such conversions remain challenging. The purpose of this Review is to present an insight into the catalytic conversion of lignin involving hydrogen, including reductive depolymerization and the hydrodeoxygenation of lignin‐derived monomers to arenes, cycloalkanes and phenols, with a main focus on the catalyst systems and reaction mechanisms. The roles of hydrogenation sites (Ru, Pt, Pd, Rh) and acid sites (Nb, Ti, Mo), as well as their interaction in selective hydrodeoxygenation reactions are emphasized. Furthermore, some inspirational strategies for the production of other value‐added chemicals are mentioned. Finally, some personal perspectives are provided to highlight the opportunities within this attractive field.
Prenatal immobilization stress and postnatal maternal separation cause differential neuroendocrine responses to fasting stress in adult male rats
Authors: Roque Angélica , Ruiz‐González Roberto , Pineda-López Edel , Torner Luz , Lajud Naima 
Published: December 2019

AbstractPrenatal immobilization stress (PNS) and postnatal maternal separation (MS180) are two widely used rodent models of early‐life stress (ELS) that affect the hypothalamus–pituitary–adrenal (HPA) axis, cause behavioral alterations, and affect glucose tolerance in adults. We compared anxiety‐like behavior, coping strategies, and HPA axis activity in PNS and MS180 adult (4‐month‐old) male rats and assessed their glucose tolerance and HPA axis response after mild fasting stress. Both PNS and MS180 induced a passive coping strategy in the forced swimming test, without affecting anxiety‐like behavior in the elevated plus‐maze. Moreover, both PNS and MS180 increased the hypothalamic corticotropin‐releasing hormone expression; however, only MS180 increased the circulating corticosterone levels. Both early life stressors increased fasting glucose levels and this effect was significantly higher in PNS rats. MS180 rats showed impaired glucose tolerance 120 min after intravenous glucose administration, whereas PNS rats displayed an efficient homeostatic response. Moreover, MS180 rats showed higher circulating corticosteroid levels in response to fasting stress (overnight fasting, 12 hr), which were restored after glucose administration. In conclusion, early exposure to postnatal MS180, unlike PNS, increases the HPA axis response to moderate fasting stress, indicating a differential perception of fasting as a stressor in these two ELS models.
Learning to fear pain after observing another's pain: An experimental study in schoolchildren
Authors: Van Lierde Elke , Goubert Liesbet , Vervoort Tine , Hughes Gethin , Van den Bussche Eva 
Published: December 2019

AbstractBackgroundChildren of individuals with chronic pain have an increased vulnerability to experience pain problems, possibly through observation of pain in their parents. As pain‐related fear (PRF) is a critical factor in the development and maintenance of chronic pain, the current experimental study examined the acquisition of PRF through observational learning and subsequent extinction after first‐hand experience of the feared stimulus.MethodsHealthy children (8–16 years) observed either their mother or a stranger performing two cold pressor tasks (CPT) filled with coloured water. In a differential conditioning procedure, one colour (CS+) was combined with genuine painful facial expressions and the other colour (CS−) with neutral facial expressions. Following this observation phase, children performed both CPTs (10°C) themselves.ResultsChildren expected the CS+ to be more painful than the CS− and they reported being more afraid and hesitant to immerse in the CS+ compared to the CS−. Moreover, this fear was reflected in children's level of arousal in anticipation of CPT performance. This learned association extinguished after performing both CPTs. Effects were not moderated by whether the child observed their mother or a stranger, by the child's pain catastrophizing, trait PRF or trait anxiety. Remarkably, learning effects increased when the child perceived a larger difference between the model's painful and neutral facial expressions.ConclusionsThis study provides evidence for observational learning of PRF and subsequent extinction in schoolchildren. This acquisition of PRF by observing parental pain may contribute to vulnerabilities in children of parents with chronic pain.SignificanceChildren may acquire pain‐related fear by observing pain in others and this learned fear can diminish after first‐hand experience. Remarkably, observational learning did not depend on the children's relationship with the model, but it did depend on the intensity of pain that is perceived. A better understanding of the impact of observing (parental) pain may help clarify the intergenerational transmission of risk for pain and inform the development of preventive programs.
Evaluation of polymorphisms in repair and detoxification genes in alcohol drinkers and non‐drinkers using capillary electrophoresis
Authors: Oliveira de Araújo Melo Caroline , Cidália Vieira Thaís , Duarte Gigonzac Marc Alexandre , Soares Fortes Jakeline , Moreira Duarte Sabrina Sara , da Cruz Aparecido Divino , Silva Daniela de Melo e 
Published: December 2019

AbstractAlcohol use disorder (AUD) causes about 3.3 million deaths around the world each year. It is the primary risk factor for the global burden of diseases in American countries. Long‐term abuse of alcohol induces numerous molecular and biochemical changes in tissues exposed to alcohol. The toxic effects of alcohol are mediated by DNA damage through various mechanisms, such as induction of oxidative damage, DNA adducts, crosslinks, and DNA strand breaks. The main aim of the current study was to compare the frequency of SNP polymorphisms in XRCC1 (rs7997782) and GSTP1 (rs1695) genes involved in DNA repair of single strand breaks (SSB) and xenobiotic detoxification between alcohol addicts and a control group comprised of non‐drinkers. Genetic polymorphisms were identified following allelic specific PCR designed to generate the amplicons containing the variants. Then amplicons were sequenced, and sequences were aligned against the human genome reference deposited in GenBank using the CLC Sequence Viewer software (version 7.6.1). The GG homozygotes in rs1695 (GSTP1) were significantly (p = 0.023) 3.8x more frequent among those with AUD when compared to the control group. No SNP variation was observed in rs7997782 (XRCC1). rs1695 variant has been associated with susceptibility to various diseases, including those related to alcohol consumption.
Power sources sizing for a fuel cell hybrid vehicle
Authors: Sadek Hani , Chedid Riad , Fares Dima 
Published: December 2019

AbstractFuel cell hybrid vehicles (FCHV) are attractive alternatives to fossil fuel based ones in terms of lowering levels of polluting emissions. This paper presents a methodology for modeling, sizing, and power management of FCHV. The aim of the study is to achieve the lowest cost of driving over different driving cycles taking into consideration the vehicle specifications and minimum drivability constraints. The tunnel dynamic programming (TDP) is used to find the optimal power split between the battery and the fuel cell to meet the power demand for driving. On the other hand, since cost is a major barrier hindering the commercialization of FCHV, Pareto front is used to determine the best combination of sizes to achieve the lowest operational cost. The analysis covers different driving cycles including a combination of the highway and urban driving cycles mimicking a realistic one. The focus on lithium titanate battery and the combination of TDP‐Pareto front are the significant contributions of this paper. Comparative results against a commercial hybrid vehicle showed that the proposed model found a more efficient design in terms of hydrogen consumption and more capable in meeting aggressive drivability constraints as the electric motor size selected is greater.