bluuebunny/crossref_metadata_2025_split huggingface dataset:
Immobilization of oriented protein molecules on poly(ethylene glycol)‐coated Si(111)
Authors: Cha Taewoon , Guo Athena , Jun Yongseok , Pei Duanquing , Zhu Xiao‐Yang 
Published: June 2004

AbstractA high‐density poly(ethylene glycol) (PEG)‐coated Si(111) surface is used for the immobilization of polyhistidine‐tagged protein molecules. This process features a number of properties that are highly desirable for protein microarray technology: (i) minimal nonspecific protein adsorption; (ii) highly uniform surface functionality; (iii) controlled protein orientation; and (iv) highly specific immobilization reaction without the need of protein purification. The high‐density PEG‐coated silicon surface is obtained from the reaction of a multi‐arm PEG (mPEG) molecule with a chlorine terminated Si(111) surface to give a mPEG film with thickness of 5.2 nm. Four out of the eight arms on each immobilized mPEG molecule are accessible for linking to the chelating iminodiacetic acid (IDA) groups for the binding of Cu2+ions. The resulting Cu2+‐IDA‐mPEG‐Si(111) surface is shown to specifically bind 6x histidine‐tagged protein molecules, including green fluorescent protein (GFP) and sulfotransferase (ST), but otherwise retains its inertness towards nonspecific protein adsorption. We demonstrate a particular advantage of this strategy: the possibility of protein immobilization without the need of prepurification. Surface concentrations of relevant chemical species are quantitatively characterized at each reaction step by X‐ray photoelectron spectroscopy (XPS). This kind of quantitative analysis is essential in tuning surface concentration and chemical environment for optimal sensitivity in probe‐target interaction.
Protein extraction from mature rice leaves for two‐dimensional gel electrophoresis and its application in proteome analysis
Authors: Islam Nazrul , Lonsdale M. , Upadhyaya N. M. , Higgins T. J. , Hirano H. , Akhurst R. 
Published: June 2004

AbstractSample preparation is crucial for extraction and higher resolution of proteins by two‐dimensional gel electrophoresis (2‐DE). In this study, we present an efficient protocol to extract proteins from mature rice leaves by minimizing the presence of nonprotein contaminants and by maximizing contact between the sample and extraction buffer. A combination of chemical and physical processes remarkably improved protein extraction for 2‐DE. The efficiency of this protocol was demonstrated by comparison of the rice proteome at two developmental stages.
CP‐MLR/PLS Directed Structure‐Activity Modeling of the HIV‐1 RT Inhibitory Activity of 2,3‐Diaryl‐1,3‐thiazolidin‐4‐ones
Authors: Prabhakar Yenamandra S. , Solomon V. Raja , Rawal Ravindra K. , Gupta Manish K. , Katti S. B. 
Published: June 2004

AbstractA detailed structure‐activity relationship study of the HIV‐1 Reverse Transcriptase (RT) inhibitory activity of two series of compounds, 2‐(2,6‐dihalo phenyl)‐3‐(substituted pyridin‐2‐yl)‐thiazolidin‐4‐ones and 2‐(2,6‐Dihalophenyl)‐3‐(substituted phenyl)‐thiazolidin‐4‐ones, belonging to 2,3‐diaryl‐thiazolidin‐4‐ones in terms of physicochemical and structural descriptors have been carried out using combinatorial protocol interfaced multiple linear regression (CP‐MLR) and partial least squares (PLS) analysis. The models developed in the study indicate a preference for hydrophobic compounds for better inhibitory activity. Also, a positive regression coefficient of I2,3, an indicator descriptor meant for the joint disposition of substituents of 2,3‐diaryl moieties of thiazolidinones to address their ability in taking a butterfly like conformation, is in agreement with all earlier observations that compounds having the ability to take butterfly like conformation will be showing better inhibitory activity. The identified models suggest that the meta‐positions of 3‐aryl moiety has the ability to accommodate hydrophobic/ steric groups. The replacement of C2″ of 3‐phenyl by nitrogen resulted in 3‐pyridyl variants of these analogues. Even though from geometry point of view, the phenyls and pyridyls span almost the same structural space and steric features, presence of nitrogen in pyridyls gave them a blend of polarity, electronic features and a different hydrophobicity profile when compared to corresponding phenyl analogue. Furthermore the PLS models, developed from those descriptors took part in CP‐MLR models, indicate that most of the descriptors have almost equal influence in accounting for the variation in the activity of these compounds. This suggests that the factors responsible for the variation in the activity have been uniformly distributed across the varying centers of the molecule. The study suggests that thiazolidinones with 3‐(pyridin‐2‐yl) moiety provide scope for further substituent variation to modulate the HIV‐1 RT inhibitory activity.
Status of HTS Data Mining Approaches
Authors: Böcker Alexander , Schneider Gisbert , Teckentrup Andreas 
Published: June 2004

AbstractHigh‐throughput screening of large compound collections results in large sets of data. This review gives an overview of the most frequently employed computational techniques for the analysis of such data and the establishment of first QSAR models. Various methods for descriptor selection, classification and data mining are discussed. Recent trends include the application of kernel‐based machine learning methods for the design of focused libraries and compilation of target‐family biased compound collections.
A Re‐evaluation of the Use of Rink, BAL, and PAL Resins and Linkers
Authors: Yraola Francesc , Ventura Rubén , Vendrell Marc , Colombo Aina , Fernàndez Joan‐Carles , de la Figuera Natalia , Fernández‐Forner Dolors , Royo Miriam , Forns Pilar , Albericio Fernando 
Published: June 2004

AbstractSee original QSAR Comb. Sci. 2004, 23, 145–152
Quantitative analysis of D‐24851, a novel anticancer agent, in human plasma and urine by liquid chromatography coupled with tandem mass spectrometry
Authors: Stokvis Ellen , Nan‐Offeringa Lianda G. A. H. , Ouwehand Mariët , Tibben Matthijs M. , Rosing Hilde , Schnaars Yvonne , Grigat Martina , Romeis Peter , Schellens Jan H. M. , Beijnen Jos H. 
Published: June 2004

AbstractThe development of a liquid chromatography/tandem mass spectrometric assay for the quantitative analysis of the novel tubulin inhibitor D‐24851 in human plasma and urine is described. D‐24851 and the deuterated internal standard were extracted from 250 μL of plasma or urine using hexane/ether (1:1, v/v). Subsequently, 10‐μL aliquots of reconstituted extracts were injected onto an Inertsil ODS analytical column (50 × 2.0 mm i.d., 5 μm particle size). An eluent consisting of methanol/5 mM ammonium acetate, 0.004% formic acid in water (80:20, v/v) was pumped at a flow rate of 0.2 mL/min. An API 365 triple quadrupole mass spectrometer was used in the multiple reaction monitoring mode for sensitive detection. For human plasma a dynamic range of 1–1000 ng/mL was validated, and for human urine a range of 0.25–50 ng/mL. Validation was performed according to the most recent FDA guidelines and all results were within requirements. The assay has been successfully applied to support a phase I clinical trial with orally administered D‐24851. Copyright © 2004 John Wiley & Sons, Ltd.
Atmospheric molded poly(methylmethacrylate) microchip emitters for sheathless electrospray
Authors: Muck Alexander , Svatoš Aleš 
Published: June 2004

AbstractDisposable poly(methylmethacrylate) (PMMA) sheathless electrospray microchip emitters were prepared for the first time using the atmospheric molding fabrication protocol. A sheathless electrospray from uncoated channel outlets, machined to cone‐shaped three‐dimensional tips, is demonstrated utilizing a simple cross design with an on‐chip liquid junction to obviate the need for external unions to voltage electrodes, thus reducing the dead volume effects as well as the complexity of fabrication. The fast replication of microchip emitters was performed by molding prepolymeric methylmethacrylate solutions into silicon‐master/aluminum‐spacer/glass‐plate molds followed by UV‐initiated free radical polymerization. The performance of the new microchip emitters was demonstrated for mass spectral measurements of methionine enkephalin, adrenocorticotropic hormone and insulin peptide/protein mixtures. The samples were infused through capillary connections using hydrodynamic pumping. The polymeric emitters prepared by this flexible fabrication route offer an easy way of operation and high stability, without a need for attachment of external voltage unions or metallizing the emitter tips. The new approach should provide a useful low‐cost tool for widespread coupling of mass spectrometry to chip systems. Copyright © 2004 John Wiley & Sons, Ltd.
Quantification of cyclophosphamide and its metabolites in urine using liquid chromatography/tandem mass spectrometry
Authors: Kasel Dirk , Jetter Alexander , Harlfinger Steffi , Gebhardt Wilhelm , Fuhr Uwe 
Published: June 2004

AbstractA reliable and easy to use liquid chromatography/tandem mass spectrometry (LC/MS/MS) method was developed for the simultaneous quantification of urinary concentrations of cyclophosphamide (CP) and its main metabolites excreted in urine, i.e. N‐dechloroethylcyclophosphamide (DCL‐CP), 4‐ketocyclophosphamide (4KetoCP), and carboxyphosphamide (CarboxyCP). Sample preparation consisted of dilution of urine with an aqueous solution of the internal standard D4‐CP and methanol, and centrifugation. LC/MS/MS detection was performed using a triple‐quadrupole mass spectrometer working in selected reaction monitoring mode. All analytes were quantified in a single run within 11.5 min. The limits of detection were 5 ng/mL for CP and 4KetoCP, 1 ng/mL for DCL‐CP, and 30 ng/mL for CarboxyCP. Quantification ranges were adjusted to the expected concentrations in 24‐h urine collections of patients treated with a polychemotherapy regimen (3–175 μg/mL for CP, 0.5–27 μg/mL for 4KetoCP and 0.17–9 μg/mL for CarboxyCP and DCL‐CP, respectively). The method was validated according to international guidelines of the ICH and the FDA. Copyright © 2004 John Wiley & Sons, Ltd.
Comparison of desorption/ionization on silicon (DIOS) time‐of‐flight and liquid chromatography/tandem mass spectrometry for assaying enzyme‐inhibition reactions
Authors: Wall Daniel B. , Finch Jeffrey W. , Cohen Steven A. 
Published: June 2004

AbstractDesorption/ionization on silicon with time‐of‐flight mass spectrometry (DIOS‐TOFMS) was employed for rapid quantification of small molecules and the measurement of critical constants used in enzyme kinetics studies. The approach was used to determine the Michaelis constant (Km) for acetylcholine esterase and the 50% inhibition constant (IC50) for tacrine. The Km was determined from a Lineweaver‐Burk plot to be 98 μM. The IC50 was determined by assaying acetylcholine esterase activity with a range of tacrine concentrations, and measuring the amount of choline produced at a fixed time point by either DIOS‐TOFMS or by liquid chromatography tandem mass spectrometry (LC/MS/MS). DIOS‐TOFMS indicated an IC50 of 32.0 nM while LC/MS/MS gave a value of 31.8 nM. The excellent correlation with the reported IC50 values, ranging from 30.0 to 50.0 nM, and equivalence with the LC/MS/MS results, confirms that the DIOS‐TOFMS method can be used for rapid and specific quantification of enzyme‐inhibition assays. Copyright © 2004 John Wiley & Sons, Ltd.
Generation of C6H by laser vaporization of magnesium with o‐C6H4F2 in argon carrier gas
Authors: Liu Haichuan , Yang Shihe , Balteanu Iulia , Balaj O. Petru , Fox‐Beyer Brigitte S. , Beyer Martin K. , Bondybey Vladimir E. 
Published: June 2004

AbstractA route to efficient generation of C6H, potentially the benzyne radical cation, is presented. Laser vaporization of Mg+. and supersonic expansion in helium doped with o‐, m‐, or p‐C6H4F2 yields, among other ions, o‐, m‐, p‐C6H4F2Mg+. complexes, but no C6H. Collision‐induced dissociation experiments show that the o‐C6H4F2Mg+. complex can be converted into C6H in a mildly energetic collision, with a center‐of‐mass energy around 1–2 eV. These conditions can also be reached in the ion source when argon is used as a carrier gas. In this way, mass spectra containing the desired m/z 76 peak, i.e. C6H, are obtained. Copyright © 2004 John Wiley & Sons, Ltd.
Time‐of‐flight atom‐probe field ion microscope studies of surface‐related phenomena
Authors: Tsong Tien T. 
Published: June 2004

AbstractThe time‐of‐flight atom‐probe field ion microscope is both a single‐atom detection sensitivity mass‐to‐charge ratio analyser and an ion energy analyser, provided that the instrument resolution is good enough. Its major applications are in material analysis. However, it has been used also for studying surface‐related phenomena such as surface segregation of alloys, mechanisms of ion formation in field desorption, novel ion and cluster ion formation in laser‐stimulated field ion emission, field dissociation of compound ions and its novel isotope effects and analysis of the site‐specific binding energy of surface atoms, etc. Some of these studies are briefly reviewed here. Copyright © 2004 John Wiley & Sons, Ltd.
Atom probe field ion microscopy investigations on the intermetallic Ni49.5Al49.5Re1 alloy
Authors: Deges J. , Fischer R. , Frommeyer G. , Schneider A. 
Published: June 2004

AbstractThe hypoeutectic intermetallic alloy Ni49.5Al49.5Re1 exhibits promising mechanical properties for high‐temperature applications up to 1250°C, therefore atom probe field ion microscopy (APFIM) investigations were performed in the as‐cast state and after various heat treatments (at 1000°C for different times up to 1000 h and at 1300°C for 1000 h). The imaging properties and the effect of various heat treatments on the solubility and precipitation of Re within the NiAl matrix have been investigated. The field ion micrographs of Ni49.5Al49.5Re1 alloy reveal characteristic imaging features of the NiAl–Re system. Single Re atoms dissolved in the NiAl solid solution matrix were observed as bright imaging species. This is due to preferential retention of Re atoms, as well as the high ionization rate caused by adsorption of Ne image gas atoms by Re atoms. The adsorption of Ne image gas atoms is proved by the occurrence of ReNe3+ and ReNe2+ ions detected in the atom probe mass spectra. Rhenium precipitates of different shapes and several tens of nanometres in size were imaged, as well as small clusters of a few atoms. Conglomerations of a few Re atoms have been detected and the site occupancy of Re atoms in the NiAl superlattice was determined by means of APFIM measurements. Copyright © 2004 John Wiley & Sons, Ltd.
Conventional and tomographic atom probe investigations of secondary‐hardening carbides
Authors: Leitner H. , Stiller K. , Andren H‐O. , Danoix F. 
Published: June 2004

AbstractSecondary‐hardening carbides in high‐speed steels are very important microstructural constituents responsible for the excellent properties of these steels in cutting applications, therefore detailed knowledge about their precipitation reactions and coarsening behaviour is of great interest.The investigations were carried out on steel grades HS2‐10‐1‐8 and HS6‐5‐2 with nominal chemical compositions (in wt.%) of 1.1C–3.9Cr–1.4W–9.2Mo–1.2V–8Co (HS2‐10‐1‐8) and 0.9C–4.1Cr–6.4W–5Mo–1.8V (HS6‐5‐2). The austenitizing temperatures for HS2‐10‐1‐8 and HS6‐5‐2 were 1190°C and 1210°C, respectively. After quenching, the samples were heated non‐isothermally from room temperature to different final temperatures at 15 K min−1. The resulting precipitates were analysed to determine composition, size and morphology using both a conventional one‐dimensional atom probe and a three‐dimensional tomographic atom probe. The results obtained by both techniques from samples at different heat treatment conditions are compared. Owing to the different evaporation field of the precipitates, an overlap of the ion trajectories from matrix and precipitates can be observed. Methods to correct the analytical results are discussed. Copyright © 2004 John Wiley & Sons, Ltd.
Microstructural characterization of Inconel 706 alloy
Authors: Wanderka N. , Naundorf V. , Banhart J. , Mukherji D. , Genovesse D. Del. , Rösler J. 
Published: June 2004

AbstractInconel 706 is a wrought Ni–Fe‐based superalloy used for high‐temperature services, e.g. for gas turbine discs. It is age‐hardened by precipitation of coherent γ′ and/or γ″ in the austenitic matrix γ, where γ″ is the main hardening phase. However, the microstructure of Inconel 706 is strongly dependent on the age‐hardening treatment. Direct ageing produces individual γ′ and γ″ precipitates and γ′–γ″ coprecipitates, whereas a three‐step heat treatment with stabilization at 820°C, produces η precipitates mainly at the grain boundaries. Characterization of the composition of precipitate and matrix phases was carried out by three‐dimensional atom probe tomography. The microstructure was investigated by high‐resolution transmission electron microscopy.After direct ageing the precipitates are generally smaller than after the stabilizing heat treatment. Their average size is ∼10 nm. After the stabilizing heat treatment the γ′–γ″ coprecipitates have sizes between 15 and 20 nm. In addition, much bigger individual γ″ precipitates of size >50 nm were also observed. They are semi‐coherent with the matrix and are oriented parallel to the <001> lattice direction of the γ matrix. Although the γ′ phase is enriched in Ni, Al, Ti and Nb, the γ″ phase contains little Al (<1 at.%) and is enriched in Ti (∼12 at.%) and Nb (∼15 at.%). The results are discussed with respect to the influence that the particular heat treatment has on the morphology and composition of the precipitates and the γ matrix. Copyright © 2004 John Wiley & Sons, Ltd.
Improvement of multilayer analyses with a three‐dimensional atom probe
Authors: Vurpillot Francois , Larson David , Cerezo Alfred 
Published: June 2004

AbstractOwing to their giant magnetoresistance properties, multilayer thin‐film materials are widely used in information storage technology. However, because this magnetic behaviour is highly sensitive to interface roughness and diffusivity on a subnanometre scale, the structural characterization of these materials with high spatial resolution is of fundamental importance. The three‐dimensional atom probe is one of the instruments that theoretically can provide chemical analyses in three dimensions with the highest spatial resolution. However, because three‐dimensional reconstructions can be subject to strong artefacts due to trajectory aberrations, it is important to combine experimental analyses with theoretical investigations of the evaporation and reconstruction process in order to obtain the most accurate data on interface structure.In this paper, a simulation model is used in order to compute the ion trajectories close to a field emitter. The model is modified to take into account the unique morphology of the multilayer thin‐film structure. This model gives a sound interpretation of the three‐dimensional atom probe images of multilayer thin films. The three‐dimensional atom probe reconstructions of NiFe/FeCo/Cu multilayer structures are found to be degraded by strong artefacts owing to the difference in evaporation field between the FeCo layer and the Cu layer. By using simulation, these aberration effects are interpreted as errors in the calculation of thez‐dimension within three‐dimensional images. A correction procedure has been developed to improve the reconstruction of multilayer thin films in the three‐dimensional atom probe. Copyright © 2004 John Wiley & Sons, Ltd.
Electronic properties of low‐field‐emitting ultrananocrystalline diamond films
Authors: Frolov V. D. , Pimenov S. M. , Konov V. I. , Polyakov V. I. , Rukovishnikov A. I. , Rossukanyi N. M. , Carlisle J. A. , Gruen D. M. 
Published: June 2004

AbstractThis work reports on electronic properties of nitrogen‐doped, n‐type ultrananocrystalline diamond (UNCD) films grown on p‐type Si substrates from CH4–Ar–N2 gas mixtures using a microwave plasma chemical vapor deposition technique. Films ∼1 µm thick were grown with 5%N2 and 10%N2 in the plasmas. Charge‐based deep‐level transient spectroscopy showed a shallow level of point defects with an activation energy of ∼0.05 eV. The density of these shallow defects was increased with increasing nitrogen content in the plasma. Complex scanning probe microscopy methods were applied to study the film microstructure. Generally it was found that the nitrogen‐doped UNCD films showed a periodic ‘cell‐like’ structure in which the cell with a lateral size of several nanometers was less conducting than the boundary between the cells. The boundary width was found to be 0.5–1 nm. The observed details of the periodic structure can be associated with diamond nanocrystallites (grains) and grain boundaries, respectively. In addition, 2–5 nm high‐conducting inclusions clustered on the film surface were observed. It was noted that the emission field was inversely proportional to the film electroconductivity, and the lowest emission field of F ∼ 10 V µm−1 was detected near the high‐conducting inclusions. Moreover, the surface electron potential at the emission sites was lowered. The reasons why the shallow donor center is predominantly introduced by nitrogen incorporated into the grain boundaries and the possible mechanisms of low‐field electron emission from the nitrogen‐doped UNCD films have been discussed. Copyright © 2004 John Wiley & Sons, Ltd.
Some features of aligned CVD carbon nanotubes for electron field emission
Authors: Bartsch K. , Graff A. , Schöps‐Dörfel V. , Leonhardt A. , Knapp W. 
Published: June 2004

AbstractBundles of vertically grown multi‐walled carbon nanotubes were deposited on thin cobalt catalyst layers and heterogeneous WC–Co hard metal surfaces. Two different structures were detected for these layers (tubular and bamboo‐like structures), which are related to the size of the catalyst particles formed and the temperature during the process. Furthermore, free‐standing carbon nanotubes were obtained on WC–Co hard metal surfaces with a reduced Co content. Field emission measurements yielded better results for the bundle‐like carbon nanotube layers. After repeated tests, degradation of the layers was observed. Possible reasons for these effects are discussed. Copyright © 2004 John Wiley & Sons, Ltd.
Field emission study of titanium silicide array
Authors: Choi Seong S. , Jung M. Y. , Joo M. S. , Kim D. W. , Park M. J. , Kim S. B. , Jeon H. T. 
Published: June 2004

AbstractA silicon field emitter array (FEA) was fabricated on n‐type, low‐resistance (5Ω·cm) Si(100) wafer by anisotropic etching (dipping in 40 wt.% KOH solutions). To increase the thermochemical durability of the tip, the long‐term stability and the current density, Ti (30 nm) film was deposited with evaporation and the silicide was formed by annealing at 650°C. The C54–TiSi2 phase of the sample was observed by x‐ray diffraction analysis. The emission characteristics of the titanium silicide FEA were compared with those of an Si FEA under high vacuum conditions of ∼10−7 Torr. The turn‐on voltage of the titanium silicide FEA is ∼1500 V whereas that of the Si FEA is found to be 1950 V. In addition, the emission stability of the titanium silicide FEA proved to be much better than that of the Si FEA. Copyright © 2004 John Wiley & Sons, Ltd.
Phase separation in Cu47Ti33Zr11Ni8Si1
Authors: Miller M. K. , Glade S. C. , Johnson W. L. 
Published: June 2004

AbstractAn atom probe tomography characterization of the microstructure of as‐cast Cu47Ti33Zr11Ni8Si1 that was either injection cast into a copper mold (cooling rate 4 × 103 K s−1) or splat quenched (cooling rate 2 × 106 K s−1) has been performed. In both materials, the bulk metallic glass had phase‐separated into two interconnected amorphous phases. The copper‐enriched regions were depleted in titanium and the copper‐depleted regions were enriched in titanium. There was no difference in the degree of phase separation associated with the cooling rate. Published in 2004 by John Wiley & Sons, Ltd.