bluuebunny/crossref_metadata_2025_split huggingface dataset:
Impedance DNA Biosensor Using Electropolymerized Polypyrrole/Multiwalled Carbon Nanotubes Modified Electrode
Authors: Xu Ying , Ye Xiaoyan , Yang Lin , He Pingang , Fang Yuzhi 
Published: June 2006

AbstractIn this paper, we present an electrochemical impedance‐based DNA biosensor by using a composite material of polypyrrole (PPy) and multiwalled carbon nanotubes (MWNTs) to modify glassy carbon electrode (GCE). The polymer film was electropolymerized onto GCE by cyclic voltammetry (CV) in the presence of carboxylic groups ended MWNTs (MWNTs‐COOH). Such electrode modification method is new for DNA hybridization sensor. Amino group ended single‐stranded DNA (NH2‐ssDNA) probe was linked onto the PPy/MWNTs‐COOH/GCE by using EDAC, a widely used water‐soluble carbodiimide for crosslinking amine and carboxylic acid group. The hybridization reaction of this ssDNA/PPy/MWNTs‐COOH/GCE resulted in a decreased impedance, which was attributed to the lower electronic transfer resistance of double‐stranded DNA than single‐stranded DNA. As the result of the PPy/MWNTs modification, the electrode obtained a good electronic transfer property and a large specific surface area. Consequently, the sensitivity and selectivity of this sensor for biosensing DNA hybridization were improved. Complementary DNA sequence as low as 5.0×10−12 mol L−1 can be detected without using hybridization marker or intercalator. Additionally, it was found that the electropolymerization scan rate was an important factor for DNA biosensor fabrication. It has been optimized at 20 mV s−1.
Effect of staining reagent on peptide mass fingerprinting from in‐gel trypsin digestions: A comparison of SyproRuby™ and DeepPurple™
Authors: Tannu Nilesh S. , Sanchez‐Brambila Gabriela , Kirby Pam , Andacht Tracy M. 
Published: June 2006

AbstractAs the new fluorescent stains such as SyproRuby™ and DeepPurple™ are getting widespread recognition for proteome analyses by the traditional 2‐D gel method, it becomes important to test the feasibility of these stains with respect to staining reproducibility, protein quantitation, and compatibility of the stain with downstream MS. The binding of epicocconone, active ingredient of DeepPurple™, to one of the primary cleavage sites of trypsin (lysine residue) raises the possibility of incomplete cleavage and interference with PMF. However, the current study tests and concludes that the DeepPurple™ stain can result in increased peptide recovery compared to SyproRuby™ stain and can improve MS‐based identification of lower intensity proteins spots.
On‐capillary derivatization and analysis of amino acids in human plasma by capillary electrophoresis with laser‐induced fluorescence detection: Application to diagnosis of aminoacidopathies
Authors: Veledo Maria Teresa , de Frutos Mercedes , Diez‐Masa Jose Carlos 
Published: June 2006

AbstractA capillary electrophoresis with laser‐induced fluorescence detection method for the analysis of free amino acids (AA) in human plasma was developed. A mixture of 16 AA was on‐capillary derivatized with 3‐(2‐furoyl)quinoline‐2‐carboxaldehyde (FQ) and separated inside the capillary in less than 30 min using 70 mM borax‐3.5 mM SDS pH 9.3 as running buffer. Four plasma samples from a healthy donor and patients suffering from phenylketonuria, propionic acidemia, and tyrosinemia type II were studied. Repeatabilities calculated as intra‐day RSD (n = 3) values for the AA involved in these aminoacidopathies (glycine, phenylalanine, and tyrosine) were in the range of 0.3 to 1.2% for migration time and 3.7 to 8.2% for peak height. Reproducibilities calculated as inter‐day RSD (n = 4) values for the same AA were between 0.7 and 1.4% for migration time and 4.7 and 9.1% for peak height. A fast qualitative analysis allowed the identification of the corresponding disease by comparing the electrophoretic profiles from the patient and the healthy donor and noting the increased level of the specific AA accompanying each individual disease. The results of the quantitative analysis for glycine, phenylalanine, and tyrosine in the plasma samples studied using the developed method showed a good agreement with those provided by the Center of Diagnosis of Molecular Diseases using a standard method for AA analysis.
The unified equation for the evaluation of degenerated first‐order reactions in dynamic electrophoresis
Authors: Trapp Oliver 
Published: June 2006

AbstractAn analytical solution for the unified equation for degenerated (pseudo‐) first‐order reactions, e.g., enantiomerization processes, in dynamic CE is presented, and validated with a dataset of 31 250 elution profiles covering typical experimental parameters. The unified equation was applied to determine the enantiomerization barrier of the hypnotic glutarimide derivative thalidomide (Contergan®) by dynamic capillary electrokinetic chromatography (DEKC). The enantiomer separation of thalidomide was performed in an aqueous 50 mM sodium borate buffer at pH 9.3 in the presence of the chiral mobile phase additive carboxymethyl‐β‐CD. Interconversion profiles featuring pronounced plateau formation were observed. Activation parameters ΔH≠ and ΔS≠ were obtained from temperature‐dependent measurements between 20.0 and 37.5°C in 2.5K steps. From the activation parameters the enantiomerization barrier of thalidomide at 37°C under basic conditions were calculated to be ΔG≠ = 93.2 kJ/mol. Comparison of the kinetic data with results obtained at pH 8.0 reveals the catalytic influence of the base on the enantiomerization barrier.
QM/MM calculations with DFT for taking into account protein effects on the EPR and optical spectra of metalloproteins. Plastocyanin as a case study
Authors: Sinnecker Sebastian , Neese Frank 
Published: June 2006

AbstractA detailed study of the influence of the surrounding protein on magnetic and optical spectra of metalloproteins is presented using the quantum‐mechanical/molecular mechanical (QM/MM) approach. The well‐studied type I copper site in plastocyanin in the cupric oxidation state is taken as a test case because its spectroscopic properties have been extensively studied and are well understood. The calculations have been performed using nonrelativistic and scalar relativistic (at the level of the zeroth order regular approximation, ZORA) calculations (B3LYP functional). Linear response theory has been used to calculate first‐ and second‐order properties, namely the EPR g‐tensor, the central metal hyperfine couplings (HFCs), the HFCs of the directly coordinating ligands, as well as superhyperfine couplings (1H, 14N) from remote nuclei, transition energies, and oscillator strengths. Two different model systems have been defined that do not and do include important amino acids from the second coordination sphere, respectively. For comparison, calculations have been carried out in the gas phase and in a dielectric continuum (conductor like screening model, COSMO) with a dielectric constant of four. The best results were obtained at the scalar relativistic ZORA level for the largest model in conjunction with explicit modeling of the protein environment through the QM/MM procedure, which is also considered to be the highest level of theory used in this work. The protein effects beyond the second coordination sphere were found to be quite substantial (up to 30% changes on some properties), and were found to require an explicit treatment of the protein beyond the second coordination sphere. In addition, the embedding water cage was found to have a nonnegligible influence on the calculated spectroscopic data, which is of the same order as the influence of the protein backbone charges. However, while qualitatively satisfactory, the errors in the calculated spectroscopic parameters are still substantial, and can all be traced back to the fact that the linear‐response of the presently available functionals is “too stiff” with respect to the external perturbations at least for the model systems studied here. Ligand field‐based approaches are used to correct for systematic errors in the DFT procedures. As a consequence, we propose a new breakdown of the copper hyperfine interaction into Fermi‐contact, spin‐dipolar and spin‐orbit contributions. © 2006 Wiley Periodicals, Inc. J Comput Chem 27: 1463–1475, 2006
Performance of DFT in modeling electronic and structural properties of cobalamins
Authors: Kuta Jadwiga , Patchkovskii Seguei , Zgierski Marek Z. , Kozlowski Pawel M. 
Published: June 2006

AbstractComputational modeling of the enzymatic activity of B12‐dependent enzymes requires a detailed understanding of the factors that influence the strength of the CoC bond and the limits associated with a particular level of theory. To address this issue, a systematic analysis of the electronic and structural properties of coenzyme B12 models has been performed to establish the performance of three different functionals including B3LYP, BP86, and revPBE. In particular the cobalt–carbon bond dissociation energies, axial bond lengths, and selected stretching frequencies have been analyzed in detail. Current analysis shows that widely used B3LYP functional significantly underestimates the strength of the CoC bond while the nonhybrid BP86 functional produces very consistent results in comparison to experimental data. To explain such different performance of these functionals molecular orbital analysis associated with axial bonds has been performed to show differences in axial bonding provided by hybrid and nonhybrid functionals. © 2006 Wiley Periodicals, Inc. J Comput Chem 27: 1429–1437, 2006
A DFT study of the mechanism of Ni superoxide dismutase (NiSOD): Role of the active site cysteine‐6 residue in the oxidative half‐reaction
Authors: Prabhakar Rajeev , Morokuma Keiji , Musaev Djamaladdin G. 
Published: June 2006

AbstractIn the present DFT study, the catalytic mechanism of H2O2 formation in the oxidative half‐reaction of NiSOD, E‐Ni(II) + O + 2H+ → E‐Ni(III) + H2O2, has been investigated. The main objective of this study is to investigate the source of two protons required in this half‐reaction. The proposed mechanism consists of two steps: superoxide coordination and H2O2 formation. The effect of protonation of Cys6 and the proton donating roles of side chains (S) and backbones (B) of His1, Asp3, Cys6, and Tyr9 residues in these two steps have been studied in detail. For protonated Cys6, superoxide binding generates a Ni(III)–O2H species in a process that is exothermic by 17.4 kcal/mol (in protein environment using the continuum model). From the Ni(III)–O2H species, H2O2 formation occurs through a proton donation by His1 via Tyr9, which relative to the resting position of the enzyme is exothermic by 4.9 kcal/mol. In this pathway, a proton donating role of His1 residue is proposed. However, for unprotonated Cys6, a Ni(II)–O species is generated in a process that is exothermic by 11.3 kcal/mol. From the Ni(II)–O species, the only feasible pathway for H2O2 formation is through donation of protons by the Tyr9(S)–Asp3(S) pair. The results discussed in this study elucidate the role of the active site residues in the catalytic cycle and provide intricate details of the complex functioning of this enzyme. © 2006 Wiley Periodicals, Inc. J Comput Chem 27: 1438–1445, 2006
Correlation between computed gas‐phase and experimentally determined solution‐phase infrared spectra: Models of the iron–iron hydrogenase enzyme active site
Authors: Tye Jesse W. , Darensbourg Marcetta Y. , Hall Michael B. 
Published: June 2006

AbstractGas‐phase density functional theory calculations (B3LYP, double zeta plus polarization basis sets) are used to predict the solution‐phase infrared spectra for a series of CO‐ and CN‐containing iron complexes. It is shown that simple linear scaling of the computed CO and CN stretching frequencies yields accurate predictions of the the experimentally determined ν(CO) and ν(CN) values for a variety of complexes of different charges and in solvents of varying polarity. As examples of the technique, the resulting correlation is used to assign structures to spectroscopically observed but structurally ambiguous species in two different systems. For the (μ‐SCH2CH2CH2S)[Fe(CO)3]2 complex in tetrahydrofuran solution, our calculations show that the initial electrochemical reduction process leads to a simple one‐electron reduced product with a structure very similar to the (μ‐SCH2CH2CH2S)[Fe(CO)3]2 parent complex. For the iron–iron hydrogenase enzyme active site, our computations show that the absence or presence of a water molecule near the distal iron center (the iron center further from the [4Fe4S] cluster and protein backbone) has very little effect on the predicted infrared spectra. © 2006 Wiley Periodicals, Inc. J Comput Chem 27: 1454–1462, 2006
Treatment of paper and pulp wastewater and removal of odorous compounds by a Fenton‐like process at the pilot scale
Authors: Tambosi José L , Di Domenico Michele , Schirmer Waldir N , José Humberto J , Moreira Regina de FPM 
Published: June 2006

AbstractA Fenton‐like process, involving oxidation and coagulation, was evaluated for the removal of odorous compounds and treatment of a pulp and paper wastewater. The main parameters that govern the complex reactive system [pH and Fe(III) and hydrogen peroxide concentrations] were studied. Concentrations of Fe(III) between 100 and 1000 mg L−1 and of H2O2 between 0 and 2000 mg L−1 were chosen. The main mechanism for color removal was coagulation. The maximum COD, color and aromatic compound removals were 75, 98 and 95%, respectively, under optimal operating conditions ([Fe(III)] = 400 mg L−1; [H2O2] = 500–1000 mg L−1; pH = 2.5; followed by coagulation at pH 5.0). The biodegradability of the wastewater treated increased from 0.4 to 0.7 under optimal conditions and no residual hydrogen peroxide was found after treatment. However, partially or non‐oxidized compounds present in the treated wastewater presented higher acute toxicity to Artemia salina than the untreated wastewater. Based on the optimum conditions, pilot‐scale experiments were conducted and revealed a high efficiency in relation to the mineralization of organic compounds. Terpenes [(1S)‐α‐pinene, β‐pinene, (1R)‐α‐pinene and limonene] were identified in the wastewater and were completely eliminated by the Fenton‐like treatment. Copyright © 2006 Society of Chemical Industry
Humoral immune responses against minute virus of mice vectors
Authors: Lang Susanne I. , Giese Nathalia A. , Rommelaere Jean , Dinsart Christiane , Cornelis Jan J. 
Published: June 2006

AbstractBackgroundOwing to their oncolytic properties, autonomous rodent parvoviruses and derived vectors constitute potential anti‐tumor agents.MethodsHumoral immune responses to minute virus of mice (MVMp) were characterized. In particular, the generation of neutralizing antibodies on subsequent therapeutic virus applications was evaluated in a mouse melanoma model. Mice bearing subcutaneous melanomas were injected intratumorally with virus and re‐injected 10 days later in a second tumor on the other flank. Four days after the first or second injection, the tumors and lymph nodes were analyzed by RT‐PCR for gene expression.ResultsInjection of MVMp in tumor‐bearing B6 mice resulted in viral gene expression in tumors and draining lymph nodes. A repeated virus administration did not lead to detectable viral transcription if it was preceded by a virus infection 10 days earlier. This protection correlated with the induction of virus‐neutralizing antibodies following the first virus application. The restrictions on viral gene expression after a consecutive MVMp injection could be alleviated in subsequent applications by the use of viruses consisting of MVMp genomes packaged into capsids of a related parvovirus. Neutralizing antibody induction was irrespective of the route of administration and of the presence of a tumor and persisted at significant levels at least up to 26 weeks after the viral infection. MVMp infection of B6 mice stimulated the generation of IgM and IgG anti‐viral antibodies, the latter mainly of the T‐helper (Th) 1‐dependent IgG2, and the T‐cell‐independent IgG3 subclasses.ConclusionsNeutralizing antibodies impede the effectiveness of a subsequent virus administration, but can be overcome by pseudotyping. Copyright © 2006 John Wiley & Sons, Ltd.
Recent progress in the assays of xylanolytic enzymes
Authors: Biely Peter , Puchart Vladimír 
Published: June 2006

AbstractIncreasing industrial importance of xylanolytic enzymes together with recent evidence for cereal endoxylanase inhibitors having a negative impact on the application of enzymes in fodder and food industries, brings challenges to facilitate and simplify the procedures to follow these enzymes. This article gives a critical evaluation of current methods and outlines new methodological alternatives to follow the major depolymerising enzyme, endo‐β‐1,4‐xylanase using chromogenic substrates. Attention is paid also to assays of three accessory xylanolytic enzymes α‐glucuronidase, acetylxylan esterase and feruloyl esterase, for which new enzyme‐coupled assays were elaborated. Copyright © 2006 Society of Chemical Industry
New Fluorene‐Acceptor Random Copolymers: Towards Pure White Light Emission from a Single Polymer
Authors: Wu Wen‐Chung , Lee Wen‐Ya , Chen Wen‐Chang 
Published: June 2006

AbstractSummary: Two kinds of fluorene‐acceptor copolymers containing three emitting segments have been synthesized and explored as the emissive layer in white‐light‐emitting devices (WLEDs). The light‐emitting copolymers PFQTP and PFBTTP either contain blue‐emitting (9,9‐dihexyl‐fluorene, F), green‐emitting (quinoxaline, Q) (or yellow‐emitting (2,1,3‐benzothiadiazole, BT)), and red‐emitting (thieno[3,4‐b]‐pyrazine, TP) units in the backbone. The energy‐transfer processes between the emitting units are investigated by their absorption, photoluminescence, time‐resolved photoluminescence, and electroluminescence. The experimental results suggest that only a relatively small faction of the acceptor moiety incorporated into the fluorene can achieve white light emission through energy transfer. The energy transfer from BT to TP is more efficient that that of Q to TP because of the degree of spectroscopic overlap between absorption and luminescence. The electroluminescent device with PFBTTP1 (0.1% of BT and 0.25% of TP) as an emissive layer exhibits the Commission Internationale de L'Eclairage (CIE) 1931 coordinates of (0.33, 0.34), a luminance of 1 870 cd · m−2 under the condition of maximum luminance yield of 1.92 cd · A−1, and without significant variation with driving voltages. The present study suggests that the single polymers based on three fluorene‐acceptor segments could be potentially used for pure‐white‐light‐emitting diodes.The fluorene‐acceptor copolymers, PFQTP and PFBTTP, and the normalized EL spectra of their devices (left) and their CIE 1931 coordinates (x, y).imageThe fluorene‐acceptor copolymers, PFQTP and PFBTTP, and the normalized EL spectra of their devices (left) and their CIE 1931 coordinates (x, y).
Brand personality: Exploring the potential to move from factor analytical to circumplex models
Authors: Sweeney Jillian C. , Brandon Carol 
Published: June 2006

AbstractWith the proliferation of products and brands in the marketplace, brand personality has emerged as an important means of brand differentiation and thus of increasing consumer preference. However, little research has investigated this important construct, with the significant exceptions of Aaker's (1997) work, which is based on a factoranalytical approach. In response to the limitations of the factor approach to brand personality, this study explores the potential for advancing understanding of brand personality through a circumplex model derived from the fields of social and personality psychology and interpersonal psychiatry. The model is based on relationships between interpersonal personality traits or emotions and can assist academics and practitioners in understanding the brand personality concept. © 2006 Wiley Periodicals, Inc.
Measuring consumer vanity: A cross‐cultural validation
Authors: Wang Paul Z. , Waller David S. 
Published: June 2006

AbstractGiven the unmistakable trend toward a more integrated global economy and the tremendous impact of consumer vanity on demand for countless goods and services, there exists a need for more cross‐cultural research on the important psychological construct known as consumer vanity (Netemeyer, Burton, & Lichtenstein, 1995). This article examines four components of the vanity construct: appearance concern, appearance perception, achievement concern, and achievement perception. To test the vanity construct cross‐culturally, a survey was undertaken in the United States and China. This article illustrates the use of the comprehensive analytical framework proposed by Steenkamp and Baumgartner (1998) to assess measurement invariance in cross‐cultural consumer research. The results provided a rigorous cross‐cultural validation test of the vanity scale that has implications for both academics and practitioners in cross‐cultural consumer research and marketing. © 2006 Wiley Periodicals, Inc.
New Stimuli Responsive Poly(1‐vinylpyrrolidin‐2‐one) Bearing Pendant Activated Disulfide Groups
Authors: Bencini Marco , Ranucci Elisabetta , Ferruti Paolo , Manfredi Amedea 
Published: June 2006

AbstractSummary: A novel functionalised poly(1‐vinylpyrrolidin‐2‐one) (PVP) derivative, carrying a pre‐determined amount of 2‐(2‐pyridinyldithio)ethylamine moieties as side substituents, P(VP‐co‐VP‐SS‐Py), has been prepared from carboxylated VP copolymers, in turn obtained by copolymerising 1‐vinylpyrrolidin‐2‐one with 3,3‐di‐(ethoxycarbonyl)‐1‐vinylpyrrolidin‐2‐one in the presence of radical initiators. Using reaction solvents acting in the mean time as chain transfer agents could control its molecular weight. P(VP‐co‐VP‐SS‐Py) proved to be extremely reactive towards exchange reactions with molecules containing mercapto functions, including bioactive peptides. The exchange derivative with reduced glutathione, chosen as a model compound, was easily prepared.
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A Fluorescence Ratiometric Protein Assay Using Light‐Harvesting Conjugated Polymers
Authors: An Lingling , Tang Yanli , Wang Shu , Li Yuliang , Zhu Daoben 
Published: June 2006

AbstractSummary: A highly selective protein assay was created which combines the fluorescent ratiometric technique based on FRET with the light‐harvesting properties of conjugated polymers. The cationic poly[(9,9‐bis(6′‐N,N,N‐trimethylammonium)‐hexyl)‐fluorene phenylene] bromide (PFP‐NMe) and the negatively charged biotinylated fluorescein probe (Fl‐B) were used to detect the target protein streptavidin optically. The strong electrostatic interactions between PFP‐NMe and fluorescein result in efficient FRET from PFP‐NMe to fluorescein. In the presence of streptavidin, however, the biotin moiety of Fl‐B specifically associates with streptavidin and the fluorescein molecule is buried deeply in the adjacent vacant binding sites. This separates the fluorescein spatially from the PFP‐NMe moiety, resulting in inefficient FRET from PFP‐NMe to fluorescein. Although a nonspecific protein, such as BSA, shows nonspecific interactions with PFP‐NMe, it does not affect the fluorescent ratio value of PFP‐NMe to fluorescein. Hence, the charged neutral complex of two oppositely charged conjugated polymers can eliminate the nonspecific interactions, and thus optimize their application in protein assays.A schematic representation of the protein assay operation.magnified imageA schematic representation of the protein assay operation.