bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stabilized Laccases as Heterogeneous Bioelectrocatalysts
Authors: Betancor Lorena , Johnson Glenn R. , Luckarift Heather R. 
Published: December 2012

AbstractTypically, the use of heterogeneous enzyme catalysis is aimed at sustainability, reusability, or enhanced functionality of the biocatalyst and is achieved by immobilizing enzymes onto a support matrix or at a defined interface. Controlled enzyme immobilization is particularly important in bioelectrocatalysis because the catalyst must be effectively connected to a transducer to exploit its activity. This Review discusses what must be addressed for coupling biocatalysts to an electrode and the toolbox of methods that are available for achieving this outcome. As an illustration, we focus on the immobilization and stabilization of laccases at electronic interfaces. Historically, laccases have been used for the decolorization of dyes and for the synthesis of bio‐organic compounds; however, more recently, they have been applied to the fields of sensing and energy harvesting.1–3 There is an ever‐increasing focus on the development of new energy technologies, in which laccases find application (e.g., as cathodic catalysts in enzymatic fuel cells). Herein, we discuss the heterogeneous laccase biocatalysts that have been reported over the past 10–15 years and discuss why laccases continue to be biotechnologically relevant enzymes. Various methods for the immobilization of laccases are described, including the use of nanoscale supports and a range of encapsulation and cross‐linking chemistries. We consider the application of immobilized laccases to the food industry, in the synthesis of pharmaceuticals, and in environmental applications, specifically in cases in which stabilization through heterogenization of the enzyme is critical to the application. We also include a consideration of electrochemical biosensors and the specific incorporation of laccases on the surfaces of transducers.
Organometallic Ruthenium Nanoparticles: A Comparative Study of the Influence of the Stabilizer on their Characteristics and Reactivity
Authors: Lara Patricia , Philippot Karine , Chaudret Bruno 
Published: December 2012

AbstractThe use of metal nanoparticles as catalysts is a topic of growing interest at the frontier between homogeneous and heterogeneous catalysis. Metal nanoparticles are highly interesting systems owing to their high number of surface atoms, which give rise to numerous active sites. Furthermore, the surface properties of metal nanoparticles can be tuned by the addition of a stabilizer, for example, a polymer, a surfactant, or a ligand, or by combining a metal with a support to take profit of their synergy to orientate a catalytic reaction. Significant efforts are being made towards the synthesis of metal nanoparticles in general and, more precisely, towards the preparation of ligand‐stabilized nanoparticles in which the size, shape, and surface state are controlled. Since ligands can modulate both the electronic and steric environment at the surface of the particles, numerous studies are presently devoted to analyze the influence of ligands on the stabilization of nanoparticles and on their surface properties. Such studies are of key importance to develop more active and selective nanocatalysts. In that context, ruthenium nanoparticles are candidates of choice as they can be characterized inter alia by nuclear magnetic resonance, as ruthenium displays little or no Knight shift and since they are active catalysts for hydrogenation reactions of, for example, arenes, olefins, and alkynes. In this Review, we present an overview of our group’s efforts in the synthesis of ligand‐stabilized ruthenium nanoparticles of controlled size and surface state using different types of ligands. We report the influence of nitrogen‐, sulfur‐, silicon‐, phosphorus‐ and carbon‐ containing ligands as coordinating atoms to the metal surface, on their stabilization, as well as on their surface reactivity, in comparison with sterically‐stabilized Ru nanoparticles prepared following the same organometallic approach, but using polymers or “nanoreactors” made of alcohols or ionic liquids that allow for control of the growth of the particles by a confinement effect. Nanoparticles of other metals are also described when appropriate.
Micronization of the Pharmaceutically Active Agent Genipin by an Antisolvent Precipitation Process
Authors: Zhao X. , Song K. , Wang S. , Zu Y. , Li N. , Yu X. 
Published: December 2012

AbstractDue to its low water solubility and slow dissolution rate, genipin was micronized by an antisolvent precipitation process using ethanol as solvent and n‐hexane as antisolvent. The effects of various experimental parameters on the mean particle size (MPS) of micronized genipin were investigated. By analysis of variance, only the concentration of the genipin solution has a significant effect on the MPS in genipin micronization. Under the optimum conditions, micronized genipin with an MPS of 1.8 μm was obtained. The micronized genipin was characterized by various methods, e.g., scanning electron microscopy and thermogravimetry. The analysis results indicated that the chemical structure of micronized genipin was not changed, but the crystallinity was reduced. The dissolution rate and solubility of the micronized genipin were 2.08 and 1.64 times that of the raw drug. In addition, the residual amounts of n‐hexane and ethanol were less than the International Conference on Harmonization limit for solvents.
Estimation of Mixing Ratio for Saturated Air over Water
Authors: Bahadori A. , Zendehboudi S. , Zahedi G. 
Published: December 2012

AbstractThe role that water vapor plays in atmospheric phenomena is extremely important. Saturation of moist air at a given temperature and pressure occurs if its mixing ratio is such that the moist air can coexist in a stable condition with an associated condensed phase at the same temperature and pressure. The saturation mixing ratio is useful to calculate the relative humidity which is a ratio, expressed in percent, of the amount of water vapor in the air (actual mixing ratio) compared to the amount of water vapor the air can hold (saturation mixing ratio). In this work, an attempt has been made to develop a simple‐to‐use Arrhenius‐type function to estimate the mixing ratio for saturated air over water as a function of pressure and temperature. Estimations have been found to be in excellent agreement with the data reported in the literature, with the average absolute deviation being around 0.4 %.
Macrocyclic Mechanism‐Based Inhibitor for Neuraminidases
Authors: Kai Hirokazu , Hinou Hiroshi , Naruchi Kentaro , Matsushita Takahiko , Nishimura Shin‐Ichiro 
Published: December 2012

AbstractA macrocyclic mechanism‐based inhibitor for neuraminidases (NAs) bearing a 2‐difluoromethylphenyl aglycone and a linker between the aglycone and C‐9 positions of sialic acid was synthesized and evaluated. The macrocyclic structure was designed to keep the aglycone moiety in the active site of the neuraminidase after cleavage of the glycoside bond. When Vibrio chorelae neuraminidase (VCNA) was treated with a similar acyclic derivative in the presence of detergent, the irreversible inhibition property was disabled. In contrast, this macrocyclic compound acted as an irreversible inhibitor for VCNA in the presence of detergent. Inhibition assay for various NAs using this macrocyclic compound revealed that the irreversible inhibition property depends on the kcat of the neuraminidase treated. NAs having small kcat values, such as Influenza viruses, Clostridium, Trypanosoma cruzi, and Human, were also inhibited irreversibly. However, Salmonella typhimurium NA, which has an extremely high kcat, was not affected irreversibly by the inhibitor. Interestingly, in contrast to common kcat inhibitors, the irreversibility of inhibition by this macrocyclic compound is inversely proportional to the kcat of the target neuraminidase.
Selective Anchoring of GdIII Chelates on the External Surface of Organo‐Modified Mesoporous Silica Nanoparticles: A New Chemical Strategy To Enhance Relaxivity
Authors: Carniato Fabio , Tei Lorenzo , Arrais Aldo , Marchese Leonardo , Botta Mauro 
Published: December 2012

AbstractThe optimization of the physico‐chemical properties of both GdIII chelates and nanocarriers is of great importance for the development of effective nanosystems for magnetic resonance imaging (MRI) applications. With this aim, macrocyclic GdIII chelates were selectively attached to the pendant amino groups exposed to the external surface of spheroidal mesoporous silica nanoparticles (MSNs). This was achieved by treating the metal complexes with MSNs that contained the templating surfactant molecules confined within the silica channels (hexadecyltrimethylammonium (CTA)/MSN), followed by extraction of the surfactant. The nanoparticles showed greatly improved 1H relaxometric efficiency relative to corresponding systems that also feature GdIII chelates conjugated inside the pores. A further significant relaxivity enhancement was observed after chemical transformation of the free amino groups into amides. The ionic relaxivity of the final nanoparticles (r1p=79.1 mM−1 s−1; 0.5 T, 310 K) is one of the highest reported so far.
Synthesis, One‐ and Two‐Photon Photophysical and Excited‐State Properties, and Sensing Application of a New Phosphorescent Dinuclear Cationic Iridium(III) Complex
Authors: Xu Wen‐Juan , Liu Shu‐Juan , Zhao Xin , Zhao Ning , Liu Zhi‐Qiang , Xu Hang , Liang Hua , Zhao Qiang , Yu Xiao‐Qiang , Huang Wei 
Published: December 2012

AbstractA new phosphorescent dinuclear cationic iridium(III) complex (Ir1) with a donor–acceptor–π‐bridge–acceptor–donor (DAπAD)‐conjugated oligomer (L1) as a N^N ligand and a triarylboron compound as a C^N ligand has been synthesized. The photophysical and excited‐state properties of Ir1 and L1 were investigated by UV/Vis absorption spectroscopy, photoluminescence spectroscopy, and molecular‐orbital calculations, and they were compared with those of the mononuclear iridium(III) complex [Ir(Bpq)2(bpy)]+PF6− (Ir0). Compared with Ir0, complex Ir1 shows a more‐intense optical‐absorption capability, especially in the visible‐light region. For example, complex Ir1 shows an intense absorption band that is centered at λ=448 nm with a molar extinction coefficient (ε) of about 104, which is rarely observed for iridium(III) complexes. Complex Ir1 displays highly efficient orange–red phosphorescent emission with an emission wavelength of 606 nm and a quantum efficiency of 0.13 at room temperature. We also investigated the two‐photon‐absorption properties of complexes Ir0, Ir1, and L1. The free ligand (L1) has a relatively small two‐photon absorption cross‐section (δmax=195 GM), but, when complexed with iridium(III) to afford dinuclear complex Ir1, it exhibits a higher two‐photon‐absorption cross‐section than ligand L1 in the near‐infrared region and an intense two‐photon‐excited phosphorescent emission. The maximum two‐photon‐absorption cross‐section of Ir1 is 481 GM, which is also significantly larger than that of Ir0. In addition, because the strong BF interaction between the dimesitylboryl groups and F− ions interrupts the extended π‐conjugation, complex Ir1 can be used as an excellent one‐ and two‐photon‐excited “ON–OFF” phosphorescent probe for F− ions.
The Role of a Dipeptide Outer‐Coordination Sphere on H2‐Production Catalysts: Influence on Catalytic Rates and Electron Transfer
Authors: Reback Matthew L. , Ginovska‐Pangovska Bojana , Ho Ming‐Hsun , Jain Avijita , Squier Thomas C. , Raugei Simone , Roberts John A. S. , Shaw Wendy J. 
Published: December 2012

AbstractThe outer‐coordination sphere of enzymes acts to fine‐tune the active site reactivity and control catalytic rates, suggesting that incorporation of analogous structural elements into molecular catalysts may be necessary to achieve rates comparable to those observed in enzyme systems at low overpotentials. In this work, we evaluate the effect of an amino acid and dipeptide outer‐coordination sphere on [Ni(PPh2NPh‐R2)2]2+ hydrogen production catalysts. A series of 12 new complexes containing non‐natural amino acids or dipeptides was prepared to test the effects of positioning, size, polarity and aromaticity on catalytic activity. The non‐natural amino acid was either 3‐(meta‐ or para‐aminophenyl)propionic acid terminated as an acid, an ester or an amide. Dipeptides consisted of one of the non‐natural amino acids coupled to one of four amino acid esters: alanine, serine, phenylalanine or tyrosine. All of the catalysts are active for hydrogen production, with rates averaging ∼1000 s−1, 40 % faster than the unmodified catalyst. Structure and polarity of the aliphatic or aromatic side chains of the C‐terminal peptide do not strongly influence rates. However, the presence of an amide bond increases rates, suggesting a role for the amide in assisting catalysis. Overpotentials were lower with substituents at the N‐phenyl meta position. This is consistent with slower electron transfer in the less compact, para‐substituted complexes, as shown in digital simulations of catalyst cyclic voltammograms and computational modeling of the complexes. Combining the current results with insights from previous results, we propose a mechanism for the role of the amino acid and dipeptide based outer‐coordination sphere in molecular hydrogen production catalysts.
Elevating the Triplet Energy Levels of Dibenzofuran‐Based Ambipolar Phosphine Oxide Hosts for Ultralow‐Voltage‐Driven Efficient Blue Electrophosphorescence: From DA to DπA Systems
Authors: Han Chunmiao , Zhang Zhensong , Xu Hui , Li Jing , Zhao Yi , Yan Pengfei , Liu Shiyong 
Published: December 2012

AbstractA series of donor (D)–π–acceptor (A)‐type phosphine‐oxide hosts (DBFxPOPhCzn), which were composed of phenylcarbazole, dibenzofuran (DBF), and diphenylphosphine‐oxide (DPPO) moieties, were designed and synthesized. Phenyl π‐spacer groups were inserted between the carbazolyl and DBF groups, which effectively weakened the charge transfer and triplet‐excited‐state extension. As the result, the first triplet energy levels (T1) of DBFxPOPhCzn are elevated to about 3.0 eV, 0.1 eV higher than their DA‐type analogues. Nevertheless, the electrochemical analysis and DFT calculations demonstrated the ambipolar characteristics of DBFxPOPhCzn. The phenyl π spacers hardly influenced the frontier molecular orbital (FMO) energy levels and the carrier‐transporting ability of the materials. Therefore, these DπA systems are endowed with higher T1 states, as well as comparable electrical properties to DA systems. Phosphorescent blue‐light‐emitting diodes (PHOLEDs) that were based on DBFxPOPhCzn not only inherited the ultralow driving voltages (2.4 V for onset, about 2.8 V at 200 cd m−2, and <3.4 V at 1000 cd m−2) but also had much‐improved efficiencies, including about 26 cd A−1 for current efficiency, 30 Lm W−1 for power efficiency, and 13 % for external quantum efficiency, which were more than twice the values of devices that are based on conventional unipolar host materials. This performance makes DBFDPOPhCzn among the best hosts for ultralow‐voltage‐driven blue PHOLEDs reported so far.
Synthesis toward the Lindenane‐type Sesquiterpenoid Monomer of Chlorahololide A
Authors: Zhang Haizhen , Nan Fajun 
Published: December 2012

AbstractAn investigation toward the synthesis of the lindenane‐type sesquiterpenoid monomer of Chlorahololide A using a Yamamoto rearrangement, intramolecular cyclopropanation reaction, 1,3‐dipolar cyclization, and an intramolecular Heck reaction gave the pivotal intermediate 20. This gives a practical synthetic route that could generate further natural products of the Chloranthaceae family.
Electrochemical Determination of Phenylethanolamine A Based on Nafion/MWCNTs/AuNPs Modified Carbon Electrode
Authors: Lai Yanjun , Bai Jing , Zhu Wei , Xian Yuezhong , Jin Litong 
Published: December 2012

AbstractPhenylethanolamine A (PEA), a β‐agonist, was found to be illegally used as a growth promoter in pigs last year, causing Chinese government's great attention. Here, a sensitive electrochemical method was developed for detecting PEA by immobilization of gold nanoparticles (AuNPs), multiwalled carbon nanotubes (MWCNTs) and Nafion on the surface of a glassy carbon electrode (GCE). The Nafion/MWCNTs/AuNPs film was characterized by scanning electronic micrographs (SEM) and electrochemical impedance spectroscopy (EIS). The electrochemical behaviors of PEA at the modified GCE were investigated in detail. The synergetic effects of AuNPs, MWCNTs and Nafion amplify the electrochemical reduction signal of PEA, and result in high sensitivity for PEA determination. Under the optimal conditions, the electrochemical sensor shows a wide linear range of 0.01 to 10 (mol/L with a detection limit of 0.005 µmol/L. Moreover, the fabricated sensor presents high selectivity and long‐term stability, which paves a new way for simple, rapid, sensitive detection of PEA.
Oligo(p‐phenyleneethynylene)‐functionalized Perylenebisimidetriad: Synthesis, Photophysical Properties, and Self‐assembly
Authors: Tong Weiqi , Wei Wei , Chen Haibo , Wang Hongyu 
Published: December 2012

AbstractThe rod‐like oligo(p‐phenylene ethynylene)‐functionalized perylene bisimide triad was synthesized and characterized. Aggregation behavior in solvents of different polarity was investigated by absorption and fluorescent spectroscopy. The results showed that stronger aggregations took place in low‐polarity slovent. The experiments also indicated that the energy and electron transfer might takeplace between the two chromophores during the photoinduced excitation. Highly ordered two‐dimensional assemblies could be observed at solid/liquid interfaces.
Towards Stereochemical Control: Two Approaches for the Highly anti‐Diastereoselective Construction of the Spirolactone Moieties of Some Stemona Alkaloids
Authors: Tuo Shichuan , Liu Xuekui , Huang Peiqiang 
Published: December 2012

AbstractSome Stemona alkaloids belonging to the tuberostemospironine group possess a spirolactone moiety with anti‐configuration (C‐9/C‐9a). In this paper, we describe two approaches to this structural unity. By using bromine atom as a traceless directing group, the SmI2‐mediated reductive coupling of ketone 6 and β‐bromomethacrylate proceeded with complete anti‐diastereoselectivity. In the absence of an α‐directing (chelation) group, the one‐pot reaction of the ketone derived from alcohol 15 with the organozinc reagent generated from bromomethacrylate afforded spiro‐α‐methylene‐γ‐lactone derivative 16 as a single diastereomer. These two highly diastereoselective methods would find application in the synthesis of stemona alkaloids containing anti‐configured spiro‐lactone/pyrrolidine moieties. In addition, on the basis of our previous work, the total synthesis of (−)‐9‐epi‐11‐demethylsessilifoliamide J (11), and an improved synthesis of (−)‐9,11‐di‐epi‐sessilifoliamide J (9) were accomplished.
A Clear‐Cut Synthesis of Arteannuin O
Authors: Chen Huijun , Hao Hongdong , Wu Yikang 
Published: December 2012

AbstractThe title compound was synthesized from dihydroqinghao acid via a sequential facial selective oxidative lactonization and epoxidation, a molybdenum‐catalyzed perhydrolysis of the epoxy ring and dimethyl sulfide reduction of the hydroperhydroxyl functionality. Some explorations on the lactonization and ring‐opening of the epoxide along with data discrepancy found with the epoxy intermediate are also presented.
Novel Calix[4]arene‐based Amberlite XAD‐4 Modified Resin for As(III) Removal from Water
Authors: Qureshi Imdadullah , Memon Shahabuddin , Yilmaz Mustafa 
Published: December 2012

AbstractThe present article describes As(III) sorption behavior of novel calix[4]arene appended TS‐4 resin. The sorption ability of TS‐4 resin has been evaluated at wide range of pH, i.e., pH 2–14. The maximum As(III) sorption efficiency (95%) was achieved at pH 2, which shows that the TS‐4 resin possesses greater affinity for As(III) at this pH. Column sorption mechanism was evaluated through various operating parameters, i.e., change in concentration, flow rate, bed heights, and pH. The experimental data were also tested against bed depth service time model and from the results; it has been observed that the data is in close agreement with the theoretically calculated values. Thus, from the data it has been revealed that TS‐4 resin has maximum column efficiency of 0.13 mmol g−1. Application of TS‐4 to real samples indicates a slight decrease (2–3%) in extraction efficiency of TS‐4 because of high concentration of total dissolved salts. Thermal behavior was tested by differential scanning calorimetry and it has been observed that TS‐4 resin is stable up to 160°C. TS‐4 resin was found to be regenerable and best regeneration was achieved by using 4% solution of NaOH. It can be deduced from the study that the resin will find its applicability in small as well as industrial scale water purification plants.
Metal Impregnated Silica‐Carbon Materials from Rice Husk: A Versatile Sorbent for Toxic Organics and Inorganics in Water and Air
Authors: Majumdar Sanhita , Mandal Pijush Kanti , Das Sudip Kumar , Majumdar Rabindranath 
Published: December 2012

AbstractCarbon bearing materials derived from rice husk (RH) have long been recognized as sorbents for diverse chemicals – both organic and inorganic. This work presents an overview of studies demonstrating a single step process of carbonization of chemically pretreated RH to produce metal impregnated silica‐carbon char designated as silicarbon materials that can be utilized in sorbing out water‐borne organic and inorganic hazardous substances (such as phenol, hexavalent chromium, fluoride, and arsenic) and air‐borne volatile organic chemicals (such as acetone, chloroform, benzene, and pyridine). The metal‐impregnated silicarbon solids derived from RH appear to constitute renewable, low‐cost, user‐friendly, and efficient materials for control systems for indoor air contamination and for industrial as well as non‐industrial hazardous aqueous pollution.
Comparison of an Electrochemical and Luminescence‐Based Oxygen Measuring System for Use in the Biodegradability Testing According to Closed Bottle Test (OECD 301D)
Authors: Friedrich Judith , Längin Andreas , Kümmerer Klaus 
Published: December 2012

AbstractThe effects of persistent organic pollutants on the aquatic environment still can hardly be assessed. Therefore, ready biodegradability is a desired key characteristic of chemicals. Accordingly, biodegradation testing is of utmost importance and is a vital part within the risk assessment for organic chemicals. In the closed bottle test (CBT; OECD 301D) the degree of biological degradation of a chemical is assessed by monitoring the oxygen consumption so far with a Clark electrode as standard method. However, this method is time‐consuming, laborious and led to frequent fluctuations of the test results, which limited their validity. Due to these shortcomings, an optical system that enables contact‐free measuring of the oxygen concentration in a closed bottle, based on dynamic luminescence quenching, was examined. The test results were compared to those obtained with the “classical” electrochemical technique (Clark electrode). At first, a basic standard for the handling of the new instrument in the laboratory was developed. Then possible influencing factors, reliability, comparability, and reproducibility of the test results were investigated by running the CBTs in parallel with the electrode and optode method. The findings proved the new optode method to be unambiguously superior to the electrode technique. The frequency of fluctuations of the test results and time and effort necessary for the test run could considerably be reduced. The degradation kinetics of the test substances could be followed easily in the CBT by increasing the measuring points without much additional effort.