bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hydrolysis of polyethyleneterephthalate by p‐nitrobenzylesterase from Bacillus subtilis
Authors: Ribitsch Doris , Heumann Sonja , Trotscha Eva , Herrero Acero Enrique , Greimel Katrin , Leber Regina , Birner‐Gruenberger Ruth , Deller Sigrid , Eiteljoerg Inge , Remler Peter , Weber Thomas , Siegert Petra , Maurer Karl‐Heinz , Donelli Ilaria , Freddi Giuliano , Schwab Helmut , Guebitz Georg M. 
Published: March 2011

AbstractFrom a screening on agar plates with bis(benzoyloxyethyl) terephthalate (3PET), a Bacillus subtilis p‐nitrobenzylesterase (BsEstB) was isolated and demonstrated to hydrolyze polyethyleneterephthalate (PET). PET‐hydrolase active strains produced clearing zones and led to the release of the 3PET hydrolysis products terephthalic acid (TA), benzoic acid (BA), 2‐hydroxyethyl benzoate (HEB), and mono‐(2‐hydroxyethyl) terephthalate (MHET) in 3PET supplemented liquid cultures. The 3PET‐hydrolase was isolated from non‐denaturating polyacrylamide gels using fluorescein diacetate (FDA) and identified as BsEstB by LC‐MS/MS analysis. BsEstB was expressed in Escherichia coli with C‐terminally fused StrepTag II for purification. The tagged enzyme had a molecular mass of 55.2 kDa and a specific activity of 77 U/mg on p‐nitrophenyl acetate and 108 U/mg on p‐nitrophenyl butyrate. BsEstB was most active at 40°C and pH 7.0 and stable for several days at pH 7.0 and 37°C while the half‐life times decreased to 3 days at 40°C and only 6 h at 45°C. From 3PET, BsEstB released TA, MHET, and BA, but neither bis(2‐hydroxyethyl) terephthalate (BHET) nor hydroxyethylbenzoate (HEB). The kcat values decreased with increasing complexity of the substrate from 6 and 8 (s−1) for p‐nitrophenyl‐acetate (4NPA) and p‐nitrophenyl‐butyrate (4NPB), respectively, to 0.14 (s−1) for bis(2‐hydroxyethyl) terephthalate (BHET). The enzyme hydrolyzed PET films releasing TA and MHET with a concomitant decrease of the water‐contact angle (WCA) from 68.2° ± 1.7° to 62.6° ± 1.1° due to formation of novel hydroxyl and carboxyl groups. These data correlated with a fluorescence emission intensity increase seen for the enzyme treated sample after derivatization with 2‐(bromomethyl)naphthalene. © 2011 American Institute of Chemical Engineers Biotechnol. Prog., 2011
Protein extraction by Winsor‐III microemulsion systems
Authors: Gomez del Rio Javier A. , Hayes Douglas G. 
Published: March 2011

AbstractProteins (bovine serum albumin (BSA), α‐chymotrypsin, cytochrome c, and lysozyme) were extracted from 0.5 to 2.0 g L−1 aqueous solution by adding an equal volume of isooctane solution that contained a surfactant mixture (Aerosol‐OT, or AOT, and a 1,3‐dioxolane (or cyclic ketal) alkyl ethoxylate, CK‐2,13‐E5.6), producing a three‐phase (Winsor‐III) microemulsion with a middle, bicontinuous microemulsion, phase highly concentrated in protein (5–13 g L−1) and small in volume (12–20% of entire volume). Greater than 90% forward extraction was achieved within a few minutes. Robust W‐III microemulsion systems were formulated at 40°C, or at 25°C by including a surfactant with shorter ethoxylate length, CK‐2,13‐E3, or 1.5% NaCl (aq). Successful forward extraction correlated with high partitioning of AOT in the middle phase (>95%). The driving force for forward extraction was mainly electrostatic attractions imposed by the anionic surfactant AOT, with the exception of BSA at high ionic strength, which interacted via hydrophobic interactions. Through use of aqueous stripping solutions of high ionic strength (5.0 wt %) and/or pH 12.0 (to negate the electrostatic attractive driving force), cytochrome c and α‐chymotrypsin were back extracted from the middle phase at >75% by mass, with the specific activity of recovered α‐chymotrypsin being >90% of its original value. © 2011 American Institute of Chemical Engineers Biotechnol. Prog., 2011
Enhancing hypericin production of Hypericum perforatum cell suspension culture by ozone exposure
Authors: Xu Maojun , Yang Bin , Dong Jufang , Lu Dan , Jin Haihong , Sun Lina , Zhu Yun , Xu Xiangbin 
Published: March 2011

AbstractAccumulation of secondary metabolites is one of the common reactions of plants to ozone exposure in nature. To investigate the effect of ozone on the production of desired compounds of plant cell cultures, we assayed hypericin production of Hypericum perforatum suspension cell cultures treated with different doses of ozone at different culture phases. The results show that hypericin contents of the cells treated with 60 to 180 nL L−1 ozone are significantly higher than those of the control, showing that ozone exposure may stimulate hypericin synthesis. Hypericin production of the cells treated with ozone at exponential phase is higher than that of lag and stationary phase, which suggests that exponential phase cell cultures are more responsive to ozone exposure than lag and stationary phase cells. The highest hypericin production is obtained by the cells exposed to 90 nL L−1 ozone at late exponential phase for 3 h, being about fourfold of the control. © 2011 American Institute of Chemical Engineers Biotechnol. Prog., 2011
Noninvasive investigation of asymmetrically conjoined tripus twins with features of rachipagus, parapagus dicephalus, and cephalopagus
Authors: Lee A.W. , Farnquist B. , Islam O. , Mackenzie J. , Taylor S.A.M. , Pang S.C. , Reifel C.W. 
Published: March 2011

AbstractA hypothetical mechanism for conjoined twinning postulated by Spencer ([2003] Developmental Malformations and Clinical Implications, Baltimore: Johns Hopkins University Press, p 1–476) suggests that, after separation, monovular twins fuse in one of eight predictable homologous sites. The tripus fetal specimen under study embodies characteristics of three types therefore preventing it from classification into a simple variant of any one of the eight twin types described by Spencer. The aim of this study was to reveal internal structural anomalies of the fetal specimen by using magnetic resonance imaging and computerized tomography. Dorsally appended to the primary twin is a secondary head mass (brain tissue and ocular globe) and two spinal columns converging at T4/T5, suggesting rachipagus twinning. The ventral orientation of the secondary twin's (right lateral) lower limb suggests parapagus twinning. The caudal divergence of the spinal columns and the presence of a secondary hemipelvis, separate from the primary pelvis, suggest cephalopagus twinning. Measurements of the long bones indicate a gestational age of ∼20–23 weeks. Secondary malformations of the primary fetal body include anencephaly, cleft palate, renal agenesis, decreased left ventricular outflow, and a prematurely terminating descending aorta. This study demonstrates the possibility of using current imaging techniques to study very old, formalin‐preserved human material for documentation and scientific discussion without destroying the specimen, thus keeping it intact for posterity. Clin. Anat. 25:1023–1029, 2012. © 2012 Wiley Periodicals, Inc.
Why there are two rows of deep inferior epigastric artery perforators despite variability in the number of deep inferior epigastric artery trunks: An anatomical and embryological argument
Authors: Rozen Warren M. , Kapila Shivam , Donahoe Simon 
Published: March 2011

AbstractThe deep inferior epigastric artery (DIEA) distributes musculocutaneous perforators in a uniform pattern that comprises “medial row” versus “lateral row” perforators, with these two rows having anatomical and functional differences. This pattern of two perforator rows is distributed from the DIEA regardless of the number of major DIEA trunks, with there variably being one to four major trunks. As such, a single DIEA trunk will still distribute two perforator rows, as will four major DIEA trunks. What remains to be answered is how such an anatomical fact may come to be? The answer probably lies in the anatomy and embryology of the rectus abdominis muscle itself. With two muscle heads to each hemiabdominal rectus abdominis muscle present from early in its development, it is highly likely that each head of rectus abdominis muscle draws its own blood supply from its source DIEA pedicle, one “perforator row” for each head, regardless of DIEA branching pattern from which these rows are drawn, thus providing an embryological and anatomical basis for the observation of two uniform perforator rows. Clin. Anat. 24:786–788, 2011. © 2011 Wiley‐Liss, Inc.
Reactions of exo‐Substituted RSn93− Clusters with Pd: Endohedral Cluster Formation and Oxidative Insertion
Authors: Kocak F. Sanem , Zavalij Peter , Eichhorn Bryan 
Published: March 2011

AbstractPyridine/ethylenediamine solutions of [Sn9SnCy3]3− (1) react with [Pd(PPh3)4] to give new clusters [Pd@Sn9SnCy3]3− (2) and [Pd@Sn9PdSnCy3]3− (3), depending on stoichiometry. These compounds are formed sequentially and are the first transition metal derivates of exo‐substituted Zintl clusters. Oxidative insertion of a Pd atom into the Pd@Sn9SnCy3 bond of 2 to form 3 represents a new reaction type for Zintl cluster compounds. The conversion Sn94−→1→2→3 is a rare case in which charge and mass are conserved in a series of Zintl clusters. Complexes 1, 2, and 3 are all highly fluxional in solution. In all three clusters, the nine Sn vertices are in rapid exchange on the NMR timescale. In 1 and 2, the exo‐SnCy3 substituent also scrambles intramolecularly around the outside of the clusters. In 3, the SnCy3 group remains attached to the vertex Pd atom. The disparate reactions with the other RSn93− ions are discussed.
The Role of Surface and Subsurface Point Defects for Chemical Model Studies on TiO2: A First‐Principles Theoretical Study of Formaldehyde Bonding on Rutile TiO2(110)
Authors: Haubrich Jan , Kaxiras Efthimios , Friend Cynthia M. 
Published: March 2011

AbstractWe report a systematic investigation of the effects of different surface and subsurface point defects on the adsorption of formaldehyde on rutile TiO2(110) surfaces using density functional theory (DFT). All point defects investigated—including surface bridging oxygen vacancies, titanium interstitials, and subsurface oxygen vacancies—stabilize the adsorption significantly by up to 56 kJ mol−1 at a coverage of 0.1 monolayer (ML). The stabilization is due to a decrease of the coordination (covalent saturation) of the surface Ti adsorption sites adjacent to the defects, which leads to a stronger molecule–surface interaction. This change in the Ti is caused by the removal of a neighboring atom (oxygen vacancies) or substantial lattice relaxations induced by the subsurface defects. On the stoichiometric reference surface, the most stable adsorption geometry of formaldehyde is a tilted η2‐dioxymethylene (with an adsorption energy Eads=−125 kJ mol−1), in which a bond forms to a nearby bridging O atom and the carbonyl‐O atom in the formaldehyde binds to a Ti atom in the adjacent fivefold coordinated lattice site. The η1‐top configuration on five‐coordinate Ti4+ is much less favorable (Eads=−69 kJ mol−1). The largest stabilization is exerted by subsurface Ti interstitials between the first and second layers. These defects stabilize the η2‐dioxymethylene structure by nearly 40 kJ mol−1 to an adsorption energy of −164 kJ mol−1. Contrary to popular belief, adsorption in a bridging oxygen vacancy (Eads=−86 kJ mol−1) is much less favorable for formaldehyde compared to the η2‐ dioxymethylene structures. From these results we conclude that formaldehyde will bind in the η2‐dioxymethylene structure on the stoichiometric surface as well as in the presence of Ti interstitials and bridging oxygen vacancies. In the light of these substantial effects, we conclude that it is essential to include all the types of point defects present in typical, reduced rutile samples used for model studies, at realistic concentrations to obtain correct adsorption sites, structures, energetic, and chemi‐physical properties.
Protonation of Water Clusters Induced by Hydroperoxyl Radical Surface Adsorption
Authors: Torrent‐Sucarrat Miquel , Ruiz‐Lopez Manuel F. , Martins‐Costa Marilia , Francisco Joseph S. , Anglada Josep M. 
Published: March 2011

AbstractWe have investigated the HO2 adsorption and acid dissociation process on the surface of (H2O)20 and (H2O)21 clusters by using quantum‐chemistry calculations. Our results show that the radical forms a stable hydrogen‐bond complex on the cluster. The HO2 acid dissociation is more favorable in the case of the (H2O)21 cluster, for which the inner water molecule plays a crucial role. In fact, acid dissociation of HO2 is found to occur in two steps. The first step involves H2O autoionization in the cluster, and the second one involves the proton transfer from the HO2 radical to the hydroxide anion. The presence of the HO2 radicals on the surface of the cluster facilitates water autoionization in the cluster.
Air‐Stable n‐Type Organic Field‐Effect Transistors Based on Solution‐Processable, Electronegative Oligomers Containing Dicyanomethylene‐Substituted Cyclopenta[b]thiophene
Authors: Ie Yutaka , Nishida Kazufumi , Karakawa Makoto , Tada Hirokazu , Asano Atsushi , Saeki Akinori , Seki Shu , Aso Yoshio 
Published: March 2011

AbstractSolution‐processable, electronegative, π‐conjugated systems containing dicyanomethylene‐substituted cyclopenta[b]thiophene were synthesized as potential active materials for air‐stable n‐type organic field‐effect transistors (OFETs). Electrochemical measurements revealed that these compounds exhibited electrochemical stability and that the lowest unoccupied molecular orbital (LUMO) had an energy level less than −4.0 eV. Flash‐photolysis time‐resolved microwave conductivity (FP‐TRMC) measurements were performed, and the value of intradomain electron mobility was determined to be as high as 0.1 cm2 V−1 s−1. The OFETs were fabricated by spin‐coating thin films of the compounds as an active layer. The electron mobility of the OFETs was 3.5×10−3 cm2 V−1 s−1 in vacuum. Furthermore, electron mobility of the same order of magnitude and stable characteristics were obtained under air‐exposed conditions. X‐ray diffraction measurements of the spin‐coated thin films revealed the difference of molecular arrangements depending on the inner conjugated units. Atomic force microscopy measurements of crystalline‐structured films exhibited the formation of grains. The accomplishment of air‐stability was attributed to the combined effect of the low‐lying LUMO energy level and the molecular arrangements in the solid state, avoiding both the quenching of electron carriers and the intrusion of oxygen and/or moisture.
Olefin Metathesis Featuring Ruthenium Indenylidene Complexes with a Sterically Demanding NHC Ligand
Authors: Urbina‐Blanco César A. , Leitgeb Anita , Slugovc Christian , Bantreil Xavier , Clavier Hervé , Slawin Alexandra M. Z. , Nolan Steven P. 
Published: March 2011

AbstractThe synthesis and characterization of two new ruthenium indenylidene complexes [RuCl2(SIPr)(Py)(Ind)] 6 and [RuCl2(SIPr)(3‐BrPy)(Ind)] 7 featuring the sterically demanding N‐heterocyclic carbene 1,3‐bis(2,6‐di isopropylphenyl)‐4,5‐dihydroimidazol‐2‐ylidene (SIPr) are reported. Remarkable activity was observed with these complexes in ring closing, enyne, and cross metathesis of olefins at low catalyst loadings. The performance of SIPr‐bearing complexes 6 and 7 as well as [RuCl2(SIPr)(PCy3)(Ind)] 5 in ring opening metathesis polymerization is also disclosed. This work highlights the enormous influence of the neutral “spectator” ligands on catalyst activity and stability.
The Influence of SO2 and NO2 Impurities on CO2 Gas Hydrate Formation and Stability
Authors: Beeskow‐Strauch Bettina , Schicks Judith M. , Spangenberg Erik , Erzinger Jörg 
Published: March 2011

AbstractThe sequestration of industrially emitted CO2 in gas hydrate reservoirs has been recently discussed as an option to reduce atmospheric greenhouse gas. This CO2 contains, despite much effort to clean it, traces of impurities such as SO2 and NO2. Here, we present results of a pilot study on CO2 hydrates contaminated with 1 % SO2 or 1 % NO2 and show the impact on hydrate formation and stability. Microscopic observations show similar hydrate formation rates, but an increase in hydrate stability in the presence of SO2. Laser Raman spectroscopy indicates a strong enrichment of SO2 in the liquid and hydrate phase and its incorporation in both large and small cages of the hydrate lattice. NO2 is not verifiable by laser Raman spectroscopy, only the presence of nitrate ions could be confirmed. Differential scanning calorimetry analyses show that hydrate stability and dissociation enthalpy of mixed CO2–SO2 hydrates increase, but that only negligible changes arise in the presence of NO2 impurities. X‐ray diffraction data reveal the formation of sI hydrate in all experiments. The conversion rates of ice+gas to hydrate increase in the presence of SO2, but decrease in the presence of NO2. After hydrate dissociation, SO2 and NO2 dissolved in water and form strong acids.
Versatile Phase Transfer of Gold Nanoparticles from Aqueous Media to Different Organic Media
Authors: Karg Matthias , Schelero Natascha , Oppel Claudia , Gradzielski Michael , Hellweg Thomas , von Klitzing Regine 
Published: March 2011

AbstractA novel, simple, and very efficient method to prepare hydrophobically modified gold particles is presented. Gold nanoparticles of different sizes and polydispersities were prepared. The diameter of the gold particles ranges from 5 to 37 nm. All systems were prepared in aqueous solution stabilized by citrate and afterwards transferred into an organic phase by using amphiphilic alkylamine ligands with different alkyl chain lengths. The chain length was varied between 8 and 18 alkyl groups. Depending on the particle size and the alkylamine, different transfer efficiencies were obtained. In some cases, the phase transfer has a yield of about 100 %. After drying, the particles can be redispersed in different organic solvents. Characterization of the particles before and after transfer was performed by using UV/Vis spectroscopy, transmission electron microscopy (TEM), and small‐angle X‐ray scattering (SAXS) techniques. The effect of organic solvents with various refractive indices on the plasmon band position was investigated.
Highly Efficient Visible‐Light Driven Photochromism: Developments towards a Solid‐State Molecular Switch Operating through a Triplet‐Sensitised Pathway
Authors: Brayshaw Simon K. , Schiffers Stephanie , Stevenson Anna J. , Teat Simon J. , Warren Mark R. , Bennett Robert D. , Sazanovich Igor V. , Buckley Alastair R. , Weinstein Julia A. , Raithby Paul R. 
Published: March 2011

AbstractWe introduce a new highly efficient photochromic organometallic dithienylethene (DTE) complex, the first instance of a DTE core symmetrically modified by two PtII chromophores [Pt(PEt3)2(CC)(DTE)(CC)Pt(PEt3)2Ph] (1), which undergoes ring‐closure when activated by visible light in solvents of different polarity, in thin films and even in the solid state. Complex 1 has been synthesised and fully photophysically characterised by (resonance) Raman and transient absorption spectroscopy complemented by calculations. The ring‐closing photoconversion in a single crystal of 1 has been followed by X‐ray crystallography. This process occurs with the extremely high yield of 80 %—considerably outperforming the other DTE derivatives. Remarkably, the photocyclisation of 1 occurs even under visible light (>400 nm), which is not absorbed by the non‐metallated DTE core HCC(DTE)CCH (2) itself. This unusual behaviour and the high photocyclisation yields in solution are attributed to the presence of a heavy atom in 1 that enables a triplet‐sensitised photocyclisation pathway, elucidated by transient absorption spectroscopy and DFT calculations. The results of resonance Raman investigation confirm the involvement of the alkynyl unit in the frontier orbitals of both closed and open forms of 1 in the photocyclisation process. The changes in the Raman spectra upon cyclisation have permitted the identification of Raman marker bands, which include the acetylide stretching vibration. Importantly, these bands occur in the spectral region unobstructed by other vibrations and can be used for non‐destructive monitoring of photocyclisation/photoreversion processes and for optical readout in this type of efficiently photochromic thermally stable systems. This study indicates a strategy for generating efficient solid‐state photoswitches in which modification of the PtII units has the potential to tune absorption properties and hence operational wavelength across the visible range.
Chirality Recognition in the Glycidol⋅⋅⋅Propylene Oxide Complex: A Rotational Spectroscopic Study
Authors: Thomas Javix , Sunahori Fumie X. , Borho Nicole , Xu Yunjie 
Published: March 2011

AbstractChirality recognition in the hydrogen‐bonded glycidol⋅⋅⋅propylene oxide complex has been studied by using rotational spectroscopy and ab initio calculations. An extensive conformational search has been performed for this binary adduct at the MP2/6‐311++G(d,p) level of theory and a total of 28 homo‐ and heterochiral conformers were identified. The eight binary conformers, built of the two dominant glycidol monomeric conformers, g‐G+ and g+G−, were predicted to be the most stable ones. Jet‐cooled rotational spectra of six out of the eight conformers were observed and unambiguously assigned for the first time. The experimental stability ordering has been obtained and compared with the ab initio predictions. The relative stability of the two dominant glycidol monomeric conformers is reversed in some cases when binding to propylene oxide. The contributions of monomeric energy, deformation energy, and binary intermolecular interaction energy to the relative stability of the binary conformers are discussed.
Electron Detachment Dissociation for Top‐Down Mass Spectrometry of Acidic Proteins
Authors: Ganisl Barbara , Valovka Taras , Hartl Markus , Taucher Monika , Bister Klaus , Breuker Kathrin 
Published: March 2011

AbstractElectron detachment dissociation (EDD) is an emerging mass spectrometry (MS) technique for the primary structure analysis of peptides, carbohydrates, and oligonucleotides. Herein, we explore the potential of EDD for sequencing of proteins of up to 147 amino acid residues by using top‐down MS. Sequence coverage ranged from 72 % for Melittin, which lacks carboxylic acid functionalities, to 19 % for an acidic 147‐residue protein, to 12 % for Ferredoxin, which showed unusual backbone fragmentation next to cysteine residues. A limiting factor for protein sequencing by EDD is the facile loss of small molecules from amino acid side chains, in particular CO2. Based on the types of fragments observed and fragmentation patterns found, we propose detailed mechanisms for protein backbone cleavage and side chain dissociation in EDD. The insights from this study should further the development of EDD for top‐down MS of acidic proteins.