bluuebunny/crossref_metadata_2025 huggingface dataset:
Functionalized multi‐walled carbon nanotubes with poly(N‐(2‐hydroxypropyl)methacrylamide) by RAFT polymerization
Authors: Hong Chun‐Yan , You Ye‐Zi , Pan Cai‐Yuan
Published: March 2006

In this study, we grafted water‐soluble biocompatible polymer, poly(N‐(2‐hydroxypropyl)methacrylamide) (PHPMA), onto the surface of multi‐walled carbon nanotubes (MWNTs). The reversible addition‐fragmentation chain transfer (RAFT) agents, dithioesters, were successfully immobilized onto the surface of MWNTs first, PHPMA chains were then subsequently grafted onto MWNTs via RAFT polymerization by using dithioesters immobilized on MWNTs as RAFT agent. FTIR, XPS, 1H NMR, Raman and TGA were used to characterize the resulting products and to determine the content of water‐soluble PHPMA chains in the product. The MWNTs grafted with PHPMA chains have good solubility in distilled water, PBS buffer, and methanol. TEM images of the samples provide direct evidence for the formation of a nanostructure that MWNTs coated with polymer layer. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2419–2427, 2006
New reaction for the preparation of liquid rubber
Authors: Dubkov K. A. , Semikolenov S. V. , Babushkin D. E. , Echevskaya L. G. , Matsko M. A. , Ivanov D. P. , Zakharov V. A. , Parmon V. N. , Panov G. I.
Published: March 2006

The article reports on the noncatalytic transformation of a polybutadiene (number‐average molecular weight = 128,000) into a functionalized liquid rubber via the carboxidation of the polymer CC bonds by nitrous oxide. The reaction was conducted in a benzene solution at 160–230 °C and a pressure of 3–6 MPa. The carboxidation mechanism was determined. The main route (95%) of the reaction proceeded without cleavage of CC bonds and led to the formation of ketone groups in the polymer backbone. A minor route (5%) of the reaction proceeded with the cleavage of CC bonds, yielding two smaller fragments containing aldehyde and vinyl end groups. The availability of the cleavage route could lead to a dramatic decrease in the molecular weight, which, depending on the carboxidation degree, could be 1–2 orders of magnitude less than that of the initial material. Thus, the carboxidation of more than 15% of the polybutadiene CC bonds transformed it into a CO‐functionalized liquid rubber with a narrow molecular weight distribution. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2510–2520, 2006
Synthesis and characterization of novel red‐emitting alternating copolymers based on fluorene and diketopyrrolopyrrole derivatives
Authors: Cao Derong , Liu Qilin , Zeng Wenjing , Han Shaohu , Peng Junbiao , Liu Shouping
Published: March 2006

Two novel alternating copolymers, poly{9,9‐dihexylfluorene‐2,7‐diyl‐alt‐2,5‐dioctyl‐3,6‐bis(4‐phenyl)pyrrolo[3,4‐c] pyrrole‐1,4‐dione} (P1) and poly{9,9‐dihexylfluorene‐2,7‐diyl‐alt‐2,5‐dioctyl‐3,6‐bis(3‐phenyl)pyrrolo[3,4‐c] pyrrole‐1,4‐dione} (P2), derived from 9,9‐dihexylfluorene and diketopyrrolopyrrole (DPP), have been successfully synthesized through palladium‐catalyzed Suzuki polycondensation in good yields. P1 and P2 possess moderate molecular weights and polydispersities, well‐defined structures, and excellent thermal properties with an onset decomposition temperature around 400 °C. Both P1 and P2 in thin films exhibit red photoluminescence from DPP species exclusively, with peaks at 609 and 616 nm, respectively. Cyclic voltammetry studies show that P1 and P2 have low‐lying lowest unoccupied molecular orbital energy levels at −3.65 eV and reversible reduction processes, so these polymers may constitute another kind of red‐emitting polymer with high electron affinity. Preliminary electroluminescent results of devices with an indium tin oxide/poly(3,4‐ethylenedioxythiophene)/polymer/Ba/Al configuration reveal that P1 may be a promising candidate for red emitters with a maximum brightness of 153 cd/m2 and a maximum external quantum efficiency of 0.13%, whereas the performance of P2 is relatively poor. These differences might originate from different conjugation lengths in their main chain. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2395–2405, 2006
Short‐time stretch relaxation of entangled polymer solutions investigated using full Rouse model predictions
Authors: Wen Yu H. , Hua Chi C.
Published: March 2006

We conduct a systematical investigation into the short‐time stretch relaxation behavior (i.e., shorter than the Rouse time but sufficiently longer than the glassy time) of entangled polymer liquid in single‐step strain flows, on the basis of theory/data comparisons for a broad series of type‐A entangled polymer solutions. First, within existing normal‐mode formulations, the Rouse model predictions on a full‐chain stretch relaxation in single‐step strain flows are derived for a popular 1‐D model proposed within the Doi–Edwards tube model, as well as for the original 3‐D model for nonentangled systems. In addition, an existing formula for the aforementioned 1‐D model that, however, rested upon a consistent‐averaging or the so‐called uniform‐chain‐stretch approximation is simultaneously examined. Subsequently, the previously derived formulas on chain stretch relaxation are directly incorporated into a reliable mean‐field tube model that utilizes the linear relaxation spectrum and the Rouse time constant consistently determined from linear viscoelastic data. It is found that the predictions of the 1‐D model differ substantially from that of the original 3‐D model at short times. Theory/data comparisons further indicate that the 1‐D model without approximations seems able to describe fairly well the nonlinear relaxation data under investigation. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1199–1211, 2006
GC–MS characterization of oligomers in polyadipates used as plasticizers for PVC in food contact
Authors: Biedermann Maurus , Grob Koni
Published: March 2006

Fourteen commercial polyadipates and a polysebacate were analysed for their components of a molecular mass below 1000 Da, primarily with the aim of generating the background data for measuring the migration of this type of polymeric additives from plasticized PVC (e.g. cling films and gaskets of lids) into foods or food simulants. Since the composition of the material <1000 Da varies between the polyadipates, the main components must be identified to enable a correct quantification. Polyadipates differ in the diol used as linker, their termination (acid or alcohol) and in the end‐capping (free alcohols, acetylation, acylation with fatty acids, esterification with octanol/decanol). Gas chromatography (GC) provides good separation, but the material remaining in the column up to high temperatures decomposes and forms a hump in the rear part of the chromatogram. Examples of mass spectra are shown, the most indicative fragments pointed out and spectra of 159 components listed. The polyadipates and the sebacate are characterized by their structure, the main components <1000 Da and the fraction of material <1000 Da. Copyright © 2006 John Wiley & Sons, Ltd.
Die Stahlverbundkonstruktion der Bügelbauten des Berliner Hauptbahnhofs
Authors: Naujoks Bernd , Nicolay Thorsten , Gugeler Jochen
Published: March 2006

Pünktlich zur Fußballweltmeisterschaft wird der neue Berliner Hauptbahnhof eröffnet. Ein markantes Zeichen setzen die zwei bügelförmigen Hochhäuser, die mit dem dazwischen hängenden Glasdach die Lücke in der Mitte des Ost‐West‐Glasdaches schließen. Berichtet wird über das Tragwerk und die Montage der Stahlverbundkonstruktion dieser Bügelbauten.
Numerisches Verfahren zur Optimierung von ebenen Stahlfachwerkträgern
Authors: Steiner Wolfgang , Eilbracht Gert
Published: March 2006

Der vorliegende Aufsatz stellt ein numerisches Verfahren zur Gewichtsoptimierung von ebenen Stahlfachwerkträgern vor. Die Querschnittsabmessungen sowie die Fachwerkhöhe werden iterativ als freie Parameter bis zum Erreichen der gewichtsminimalen Fachwerkstruktur angepaßt. Die erzielten Informationen über Geometrie (Höhe) und Materialverbrauch, dargestellt in einem Höhen‐Gewichts‐Diagramm, sollen den Tragwerksplaner im Entwurfsprozeß bei der Auslegung von Fachwerkkonstruktionen unterstützen. Besonders im Hinblick auf ein ökologisches und ökonomisches Handeln gewinnt das gewichtsoptimierte Tragwerk im Entwurfsprozeß immer mehr an Bedeutung.
Auswirkungen von Temperatur, Schwinden und Kriechen auf Integralbrücken
Authors: Romeijn Arie
Published: March 2006

Einer der wichtigsten Entwurfsparameter für Integralbrücken ist die waagerechte Verschiebung am Anschluß zwischen der Fahrbahnplatte und dem Widerlager. Integralbrücken gleichen Bewegungen des Oberbaus ohne konventionelle Dehnfugen oder Lager aus. Bei waagerechten Verschiebungen in Form von Dehnung oder Schrumpfung der Fahrbahnplatte handelt es sich also um einen der wesentlichen Unterschiede zwischen “klassischen” und integralen Brückenentwürfen.

In diesem Aufsatz werden die Ergebnisse zu Untersuchungen bezüglich durch Temperatureinflüsse und Materialverhalten (zum Beispiel bei Vorspannung) verursachter waagerechter Verschiebungen einer Fahrbahnplatte aus Beton bei einer Gesamtbrückenlänge zwischen 20 m und 180 m vorgestellt. Dabei wurde auch der Einfluß unterschiedlicher Betonfestigkeitsklassen und Konstruktionsverfahren untersucht.
Transvaginal sonography in the morphological and functional assessment of segmental dilation of the distal ureter
Authors: Yang J.‐M. , Yang S.‐H. , Hsu H.‐C. , Huang W.‐C.
Published: March 2006

Primary megaureter presents a spectrum of findings ranging from mild, clinically unimportant, stable ureterectasis to severe, progressive obstructive hydroureteronephrosis. We report a patient with a double uterus and ipsilateral renal dystrophy. A previous imaging study had revealed a double uterus and obstructed left hemivagina, into which a single vaginal ectopic ureter inserted. On follow‐up intravenous urography 8 years later, the left kidney was non‐functioning, and there was segmental dilation of the distal right ureter. Transvaginal sonography with real‐time scanning and Doppler were useful in exploring the morphological and functional status of this dilated distal ureter. Copyright © 2006 ISUOG. Published by John Wiley & Sons, Ltd.
Do early pregnancy ultrasound measurements correlate with fetal nuchal translucency at 11–14 weeks?
Authors: Prefumo F. , Condous G. , Papageorghiou A. , Thilaganathan B. , Bourne T.
Published: March 2006

Objective

To assess whether extremes in nuchal translucency (NT) thickness measurements at 11–14 weeks of gestation are preceded by departures from normal in early ultrasound biometry or embryonic heart rate in euploid fetuses.

Methods

This was a retrospective analysis of data from women with singleton pregnancies examined in early pregnancy between June 2002 and January 2003, who subsequently had a nuchal translucency (NT) scan. The early pregnancy scan was performed transvaginally, and the crown–rump length (CRL), mean gestational sac diameter (GS), mean yolk sac diameter (YS) and embryonic heart rate (HR) were measured where possible. At the second scan CRL and NT were measured.

Results

A total of 534 singleton pregnancies were included in the analysis. The mean maternal age was 30 (range, 14–45) years, and 59.4% of the patients were nulliparous. The mean CRL was 11.5 (range, 1.4–30.0) mm at the first scan and 62.8 (range, 42.0–88.0) mm at the second scan. GS, YS and HR measurements were obtained in 87.6%, 72.5% and 72.5% of cases, respectively. No statistically significant correlation was observed between NT and Z‐scores of early pregnancy: GS (r = 0.013, P = 0.77), YS (r = 0.039, P = 0.44) or HR (r = 0.016, P = 0.76). GS, YS and HR were not significantly different in fetuses with NT measurements below the 10th percentile or above the 90th percentile (P = 0.24, 0.84 and 0.60, respectively).

Conclusion

Ultrasound biometry and heart rate measured in early pregnancy are not related to nuchal translucency measurements at 11–14 weeks of gestation in chromosomally normal fetuses. Copyright © 2006 ISUOG. Published by John Wiley & Sons, Ltd.
Blind adaptive modulation systems for wireless channels with binary feedback
Authors: Al‐Harthi Yahya , Tewfik Ahmed H. , Alouini Mohamed‐Slim
Published: March 2006

In this paper, we investigate the performance of a blind adaptive modulation scheme that does not require any channel knowledge and just uses binary feedback, thereby decreasing feedback load. Retransmission of erroneous packet is not considered. In particular, we present an analytical framework for the performance evaluation of a simple wireless system in terms of receiver and transmitter structure. The system requires no knowledge of the channel and relies on a binary feedback. Slow and fast Rayleigh fading channel conditions are considered. The paper includes the derivation of the closed‐form expressions of the spectral efficiency. In some cases, closed‐form expression for packet error rate (PER) are derived. Our results show relatively high PER but some applications can still operate in a satisfactory fashion in these conditions, such as voice communication. Using coded modulation with high coding gain and increasing the number of blocks per time slot decrease the PER even more. An advantage of this system is that it uses a low complexity receiver, which sends binary feedback. Copyright © 2006 John Wiley & Sons, Ltd.
Mobile location estimation for DS‐CDMA systems using self‐organizing maps
Authors: Xu Jun , Shen Xuemin (Sherman) , Mark Jon W. , Cai Jun
Published: March 2006

In this paper, a self‐organizing map (SOM) scheme for mobile location estimation in a direct‐sequence code division multiple access (DS‐CDMA) system is proposed. As a feedforward neural network with unsupervised or supervised and competitive learning algorithm, the proposed scheme generates a number of virtual neurons over the area covered by the corresponding base stations (BSs) and performs non‐linear mapping between the measured pilot signal strengths from nearby BSs and the user's location. After the training is finished, the location estimation procedure searches for the virtual sensor which has the minimum distance in the signal space with the estimated mobile user. Analytical results on accuracy and measurement reliability show that the proposed scheme has the advantages of robustness and scalability, and is easy for training and implementation. In addition, the scheme exhibits superior performance in the non‐line‐of‐sight (NLOS) situation. Numerical results under various terrestrial environments are presented to demonstrate the feasibility of the proposed SOM scheme. Copyright © 2006 John Wiley & Sons, Ltd.
A study on the PAPRs in multicarrier modulation systems with different orthogonal bases
Authors: Zhang Haixia , Yuan Dongfeng , Wang Cheng‐Xiang
Published: March 2006

This paper studies the peak‐to‐average power ratios (PAPRs) in multicarrier modulation (MCM) systems with seven different orthogonal bases, one Fourier base and six wavelet bases. It is shown by simulation results that the PAPRs of the Fourier‐based MCM system are lower than those of all wavelet‐based MCM (WMCM) systems. A novel threshold‐based PAPR reduction method is then proposed to reduce the PAPRs in WMCM systems. Both numerical and simulation results indicate that the proposed PAPR reduction method works very effectively in WMCM systems. Copyright © 2006 John Wiley & Sons, Ltd.
Investigation of multicast‐based mobility support in all‐IP cellular networks
Authors: Festag Andreas , Karl Holger , Wolisz Adam
Published: March 2006

To solve the IP mobility problem, the use of multicast has been proposed in a number of different approaches, applying multicast in different characteristic ways. We provide a systematic discussion of fundamental options for multicast‐based mobility support and the definition and experimental performance evaluation of selected schemes. The discussion is based on an analysis of the architectural, performance‐related, and functional requirements. By using these requirements and selecting options regarding network architecture and multicast protocols, we identify promising combinations and derive four case studies for multicast‐based mobility in IP‐based cellular networks. These case studies include both the standard any‐source IP multicast model as well as non‐standard multicast models, which optimally utilize the underlying multicast. We describe network architecture and protocols as well as a flexible software environment that allows to easily implement these and other classes of mobility‐supporting multicast protocols.

Multicast schemes enable a high degree of flexibility for mobility mechanisms in order to meet the service quality required by the applications with minimal protocol overhead. We evaluate this overhead using our software environment by implementing prototypes and quantifying handoff‐specific metrics, namely, handoff and paging latency, packet loss and duplication rates, as well as TCP goodput. The measurement results show that these multicast‐based schemes improve handoff performance for high mobility in comparison to the reference cases: basic and hierarchical Mobile IP. Comparing the multicast‐schemes among each other the performance for the evaluated metrics is very similar.

As a result of the conceptual framework classification and our performance evaluations, we justify specific protocol mechanisms that utilize specific features of the multicast. Based on this justification, we advocate the usage of a source‐specific multicast service model for multicast‐based mobility support that adverts the weaknesses of the classical Internet any‐source multicast service model. Copyright © 2006 John Wiley & Sons, Ltd.
Performance analysis of coded space‐time adaptive detection in DS/CDMA systems over Rayleigh fading channels
Authors: Hamouda Walaa , McLane Peter
Published: March 2006

In this paper, we study the use of channel coding in a direct‐sequence code‐division multiple‐access (DS‐CDMA) system that employs space‐time adaptive minimum‐mean square‐error (MMSE) interference suppression over Rayleigh fading channels. It is shown that the employment of adaptive antenna arrays at the receiver can assist in attenuating multiuser interference and at the same time speeds‐up the convergence rate of the adaptive receiver. In this work, we assess the accuracy of the theoretical results developed for the uncoded and convolutionally coded space‐time multiuser detector when applied to the adaptive case. It is found that the use of antenna arrays brings the receiver performance very close to its multiuser counterpart. Using performance error bounds, we show that a user‐capacity gain of approximately 200% can easily be achieved for the space‐time adaptive detector when used with a rate 1/2 convolutional code (CC) and a practical channel interleaver. This capacity gain is only 10% less than the gain achieved for the more complicated multiuser‐based receiver. Finally, we perform a comparison between convolutional and turbo coding where we find that the latter outperforms the former at all practical bit‐error rates (BER). Copyright © 2006 John Wiley & Sons, Ltd.
Tracking control design for underactuated constrained systems
Authors: Jarzębowska Elżbieta
Published: March 2006

An extension of a model-based tracking control strategy to underactuated systems is presented. Originally, it is designed for actuated systems that can perform tasks specified by equations of algebraic or differential constraints referred to as programmed, which may be nonintegrable. It is demonstrated that for both actuated and underactuated nonholonomically constrained systems one tracking control strategy can be designed. Systems we consider are nonholonomic because of constraints put on their motions as well as unactuated degrees of freedom. We detail an example, which illustrates the theory and demonstrates advantages of application of one tracking control strategy for actuated and underactuated constrained systems.
A conceptual model of water's role as a reservoir in Helicobacter pylori transmission: a review of the evidence
Authors: BELLACK N. R. , KOEHOORN M. W. , MACNAB Y. C. , MORSHED M. G.
Published: March 2006

Helicobacter pylori infection plays a role in the development of chronic gastritis, peptic ulcer and gastric cancer, yet the route of transmission into susceptible hosts remains unknown. Studies employing microbiological techniques have demonstrated that H. pylori has the ability to survive when introduced into water and that H. pylori is present in water and other environmental samples all over the world. Epidemiological studies have shown that water source and exposures related to water supply, including factors related to sewage disposal and exposure to animals, are risk factors for infection. This review describes the microbiological and epidemiological evidence for, and proposes a model of, waterborne H. pylori transmission outlining important features in the transmission cycle. In the model, humans and animals shed the bacteria in their faeces and the mechanisms for entry into water, and for survival, ingestion and infection are dependent upon a range of environmental influences. Verification of the proposed model pathways has important implications for public-health prevention strategies.
Diagnosis of HIV infection in pregnancy: data from a national cohort of pregnant women with HIV in Italy
Authors: FLORIDIA M. , RAVIZZA M. , TAMBURRINI E. , ANZIDEI G. , TIBALDI C. , MACCABRUNI A. , GUARALDI G. , ALBERICO S. , VIMERCATI A. , ANTONI A. DEGLI , FERRAZZI E.
Published: March 2006

We analysed the characteristics of the pregnancies with a previously undetected HIV infection in a national observational study of pregnant women with HIV in Italy. In a total of 443 pregnancies with available date of HIV diagnosis, 118 were characterized by a previously undetected HIV infection (26·6%, 95% CI 22·5–30·8). The following factors were independently associated with this occurrence in a multivariate analysis (adjusted odds ratios; 95% CIs): foreign nationality (5·1, 2·8–9·3); no pre-conception counselling (35·9, 4·8–266·1); first pregnancy (2·1, 1·2–4·0); asymptomatic status (6·8, 1·5–30·6). Women with previously undetected infection started antiretroviral treatment significantly later during pregnancy (P<0·001). Missed diagnosis was responsible for one case of transmission. A high rate of previously undetected HIV infection was observed. This suggests a good HIV detection during pregnancy, but also the need to reinforce HIV testing strategies among women of childbearing age. We identified some determinants which may be considered for intervention measures.
An Alternative to Cohen's κ
Authors: von Eye Alexander
Published: March 2006

At the level of manifest categorical variables, a large number of coefficients and models for the examination of rater agreement has been proposed and used. The most popular of these is Cohen's κ. In this article, a new coefficient, κ s , is proposed as an alternative measure of rater agreement. Both κ and κ s allow researchers to determine whether agreement in groups of two or more raters is significantly beyond chance. Stouffer's z is used to test the null hypothesis that κ s = 0. The coefficient κ s allows one, in addition to evaluating rater agreement in a fashion parallel to κ, to (1) examine subsets of cells in agreement tables, (2) examine cells that indicate disagreement, (3) consider alternative chance models, (4) take covariates into account, and (5) compare independent samples. Results from a simulation study are reported, which suggest that (a) the four measures of rater agreement, Cohen's κ, Brennan and Prediger's κ n , raw agreement, and κ s are sensitive to the same data characteristics when evaluating rater agreement and (b) both the z-statistic for Cohen's κ and Stouffer's z for κ s are unimodally and symmetrically distributed, but slightly heavy-tailed. Examples use data from verbal processing and applicant selection.
Coping with a Chronic Pediatric Health Condition and Health-Related Quality of Life
Authors: Petersen Corinna , Schmidt Silke , Bullinger Monika
Published: March 2006

Background: Health-related quality of life (HRQOL) is increasingly considered an important outcome variable in pediatric research. Despite the growing interest little is known about the relationship between HRQOL and other significant constructs such as coping with a chronic health condition. Objective: The current paper examined age, gender, and health condition effects on coping and HRQOL scales and explored the relationship between both constructs. Methods: A study with 295 children and adolescents (8-16 years) with three different chronic health conditions (asthma, diabetes mellitus, and arthritis) was conducted in five European countries. Coping was assessed with the CODI questionnaire and HRQOL with the chronic generic module of the DISABKIDS instrument set, which was developed within the European DISABKIDS study. Results: Significant gender differences were found for the Emotional Reaction and Acceptance scale of the CODI and the Physical and Emotion domain of HRQOL. Age differences were noted for the Wishful Thinking and Avoidance scale as well as the Emotion domain of HRQOL. Interaction effects between age and gender were not detected. Significant differences were also found regarding the type of chronic health condition and the coping scales Wishful Thinking and Distance, as well as Avoidance. Moderate significant correlations were found between the coping scales Emotional Reaction and Acceptance and the HRQOL scales. Conclusion: Gender, age, and health condition differences with regard to the use of different coping strategies need to be taken into consideration. Coping and HRQOL are closely related, especially regarding the Emotional domain where a potential overlap was noted. Here, a more precise separation of constructs is needed.
Molecular immune mechanism of C‐phycocyanin from Spirulina platensis induces apoptosis in HeLa cells in vitro
Authors: Li Bing , Gao Mei‐Hua , Zhang Xue‐Cheng , Chu Xian‐Ming
Published: March 2006

C‐phycocyanin (C‐PC), a water‐soluble protein pigment, isolated from Spirulina platensis, is of great importance because of its various medical and pharmacological properties. In the present study, we first investigated the effect of highly purified C‐PC on growth and proliferation of HeLa cells in vitro. The results indicated that there was a significant decrease in the number of cells that survived for HeLa cells treated with C‐PC compared with control cells untreated with C‐PC. Further electron‐microscopic studies revealed that C‐PC could induce characteristic apoptotic features, including cell shrinkage, membrane blebbing, microvilli loss, chromatin margination and condensation into dense granules or blocks. Agarose electrophoresis of genomic DNA of HeLa cells treated with C‐PC showed fragmentation pattern (DNA ladder of oligomers of 180–200 bp) typical for apoptotic cells. Flow‐cytometric analysis of HeLa cells treated with different concentrations of C‐PC demonstrated an increasing percentage of cells in sub‐G0/G1 phase. In addition, we found that C‐PC could promote the expression of Fas and ICAM‐1 (intercellular cell‐adhesion molecule 1) protein, while it held back the Bcl‐2 (B‐cell lymphocytic‐leukaemia proto‐oncogene 2) protein expression. This suggested that C‐PC could induce the activation of pro‐apoptotic gene and downregulation of anti‐apoptotic gene expression and then facilitate the transduction of tumoural apoptosis signals that resulted in the apoptosis of HeLa cells in vitro. Caspases 2, 3, 4, 6, 8, 9, and 10 were activated in C‐PC‐treated HeLa cells, which suggested that C‐PC‐induced apoptosis was caspase‐dependent. C‐PC treatment of HeLa cells also resulted in release of cytochrome c from the mitochondria into the cytosol that was related to apoptosis of C‐PC‐treated HeLa cells.
Multiple co‐transfection and co‐expression of human β‐1,3‐N‐acetylglucosaminyltransferase with human calreticulin chaperone cDNA in a single step in insect cells
Authors: Deo Vipin Kumar , Park Enoch Y.
Published: March 2006

Human β‐1,3‐N‐acetylglucosaminyltransferase 2 (β3GnT2) is indispensable for the conversion of lacto‐N‐triose II into lacto‐N‐tetraose and lacto‐N‐neotetraose. In this paper, we report multiple co‐transfection in a single step using two different human cDNAs in an insect cell, β3GnT2 and calreticulin chaperone respectively. This minimized the time required to isolate stably expressing cell line from 12 weeks to 4 weeks and simplified the isolation technique to a one‐step process. We tried to insert as much cDNA as possible and used various concentrations of two antibiotics, Blasticidin and Geneticin, at 25–1500 μg/ml respectively during co‐transfection for the selection of an efficiently expressing stable cell line with no adverse effects. A stably expressing cell line was isolated which expressed β3GnT2 and chaperone simultaneously, which gave an activity of 10.1 m‐units/ml compared with 6.7 m‐units/ml by a cell only carrying β3GnT2. In this study we correlated the activity of β3GnT2 with the amount of β3GnT2 and human calreticulin cDNA in a stably expressing insect cell line simultaneously expressing calreticulin chaperone. When the amounts of chaperone and β3GnT2 cDNA were in a rough ratio of 1:1, the β3GnT2 activity was at a high level. In order to achieve better expression levels of β3GnT2 with less cost and time, efficient ways have to be devised.
Agrobacterium‐mediated delivery of marker genes to Phanerochaete chrysosporium mycelial pellets: a model transformation system for white‐rot fungi
Authors: Sharma Krishna Kant , Gupta Shefali , Kuhad Ramesh Chander
Published: March 2006

The lack of an efficient transformation system in filamentous fungi is one of the major problems in carrying out cloning and expression of genes to produce a value‐added product at the commercial level. Therefore an attempt has been made to develop an efficient, convenient and expeditious genetic transformation system for successful transfer of transferred DNA, carrying the genes coding for GUS (β‐glucuronidase) (uidA), green fluorescent protein (gfp) and hygromycin phosphotransferase (hpt) to the nuclear genome of Phanerochaete chrysosporium, a widely studied lignin‐degrading white‐rot fungus. The transformation of the marker gene was confirmed through GUS, PCR and Southern‐blot hybridization. Transformation with acetosyringone, in the presence of light with partial bleaching for 1 h, were found to be a better combination for fungal transformation with 48% efficiency. The agro‐transformation method to transform the modified mycelial pellets offers a practical means for exploiting transgenic approaches in genetic manipulation and improvement of P. chrysosporium, a model white‐rot fungus. Moreover, it has the potential to overcome the technical hurdles in genetic manipulation to bio‐technologically exploit many other filamentous fungi of industrial importance.
Application of random amplified polymorphic DNA (RAPD) to detect the genotoxic effect of heavy metals
Authors: Enan Mohamed R.
Published: March 2006

This paper presents the results of a study on the influence of lead, copper, manganese and cadmium on DNA integrity in plant cells. Plants, as biological indicators, can measure the potential effects of pollutants when they are used to measure effects of heavy metals. The genotoxicity of heavy metals in kidney‐bean (Phaseolus vulgaris) seedlings was subjected to RAPD (random amplified polymorphic DNA) analysis. An RAPD ‘fingerprinting’ technique was used to detect DNA damage in the kidney‐bean seedlings treated with two selected heavy metals at concentrations of 150 and 350 mg·l−1. Polymorphisms became evident as the presence and/or absence of DNA fragments in treated samples compared with the untreated one. At 350 mg·l−1, a high number of both missing bands and new amplified fragment were observed. Results suggested that a qualitative measure reflecting changes in RAPD profiles were significantly affected at higher concentrations (350 mg·l−1) of the tested heavy metals. A total of 467 RAPD fragments in RAPD profiles were detected by using six random primers (decamers) and 224 of these fragments showed polymorphism. There was a distinct distance between the band patterns of treated plants and the control samples when the cluster method was applied. In addition, the result derived from numerical analysis revealed a considerable distance between the band pattern of the plant samples treated with 350 mg·l−1 heavy metals and the control sample. Finally, a comparison between untreated and treated genomes shows that RAPD analysis can be used to evaluate how the environmental pollutants modify the structure of DNA in living organisms.
One‐step on‐column purification and refolding of a single‐chain variable fragment (scFv) antibody against tumour necrosis factor α
Authors: Liu Mengyuan , Wang Xiangbin , Yin Changcheng , Zhang Zhong , Lin Qing , Zhen Yongsu , Huang Hualiang
Published: March 2006

Single‐chain variable fragment (scFv) is a low‐molecular‐mass recombinant antibody and is usually expressed as inclusion bodies in Escherichia coli. Highly efficient purification and refolding methods are required to provide enough active proteins for therapeutic or diagnostic use. In the present study, an anti‐TNFα (tumour necrosis factor α) scFv (TNF‐scFv) was constructed and expressed in E. coli BL21(DE3) star as inclusion bodies, and a convenient procedure of one‐step on‐column purification and refolding was provided for it. Briefly, denatured TNF‐scFv was firstly captured by immobilized metal (Ni) affinity chromatography, and then non‐denaturing detergent (Triton X‐100)‐containing and β‐cyclodextrin‐containing solutions were loaded in turn on to the column to perform ‘artificial chaperone‐assisted refolding’ after removing impurities. More than 77% of denatured TNF‐scFv protein was refolded successfully with a purity of more than 95%. Activity assays showed that refolded TNF‐scFv could bind to rhTNFα (recombinant human TNFα) specifically with high affinity. It could inhibit rhTNFα from binding to TNF receptors and neutralize the cytolytic activity of rhTNFα against L929 cells effectively. A conclusion was obtained that this refolding method is time‐saving and suitable for industrial production. It may also be applicable to other scFvs or other recombinant proteins.
Dimerization is required for SH3PX1 tyrosine phosphorylation in response to epidermal growth factor signalling and interaction with ACK2
Authors: Childress Chandra , Lin Qiong , Yang Wannian
Published: March 2006

SH3PX1 [SNX9 (sorting nexin 9)] is a member of SNX super-family that is recognized by sharing a PX (phox homology) domain. We have previously shown that SH3PX1, phosphorylated by ACK2 (activated Cdc42-associated tyrosine kinase 2), regulates the degradation of EGF (epidermal growth factor) receptor. In mapping the tyrosine phosphorylation region, we found that the C-terminus of SH3PX1 is required for its tyrosine phosphorylation. Further analysis indicates that this region, known as the coiled-coil domain or the BAR (Bin–amphiphysin–Rvs homology) domain, is the dimerization domain of SH3PX1. Truncation of as little as 13 amino acid residues at the very C-terminus in the coiled-coil/BAR domain of SH3PX1 resulted in no dimerization, no ACK2-catalysed and EGF-stimulated tyrosine phosphorylation and no interaction with ACK2. The intracellular localization of SH3PX1 became dysfunctional upon truncation in the BAR domain. Taken together, our results indicate that the dimerization, which is mediated by the BAR domain, is essential for the intracellular function of SH3PX1.
Analysis of the hypoxia-sensing pathway in Drosophila melanogaster
Authors: Arquier Nathalie , Vigne Paul , Duplan Eric , Hsu Tien , Therond Pascal P. , Frelin Christian , D'Angelo Gisela
Published: March 2006

The mechanism by which hypoxia induces gene transcription involves the inhibition of HIF-1α (hypoxia-inducible factor-1 α subunit) PHD (prolyl hydroxylase) activity, which prevents the VHL (von Hippel-Lindau)-dependent targeting of HIF-1α to the ubiquitin/proteasome pathway. HIF-1α thus accumulates and promotes gene transcription. In the present study, first we provide direct biochemical evidence for the presence of a conserved hypoxic signalling pathway in Drosophila melanogaster. An assay for 2-oxoglutarate-dependent dioxygenases was developed using Drosophila embryonic and larval homogenates as a source of enzyme. Drosophila PHD has a low substrate specificity and hydroxylates key proline residues in the ODD (oxygen-dependent degradation) domains of human HIF-1α and Similar, the Drosophila homologue of HIF-1α. The enzyme promotes human and Drosophila [35S]VHL binding to GST (glutathione S-transferase)–ODD-domain fusion protein. Hydroxylation is enhanced by proteasomal inhibitors and was ascertained using an anti-hydroxyproline antibody. Secondly, by using transgenic flies expressing a fusion protein that combined an ODD domain and the green fluorescent protein (ODD–GFP), we analysed the hypoxic cascade in different embryonic and larval tissues. Hypoxic accumulation of the reporter protein was observed in the whole tracheal tree, but not in the ectoderm. Hypoxic stabilization of ODD–GFP in the ectoderm was restored by inducing VHL expression in these cells. These results show that Drosophila tissues exhibit different sensitivities to hypoxia.
Thermostability enhancement and change in starch hydrolysis profile of the maltohexaose-forming amylase of Bacillus stearothermophilus US100 strain
Authors: Ben Ali Mamdouh , Khemakhem Bassem , Robert Xavier , Haser Richard , Bejar Samir
Published: March 2006

The implications of Asn315 and Val450 in the atypical starch hydrolysis profile of Bacillus stearothermophilus Amy (α-amylase) US100 have been suggested previously [Ben Ali, Mhiri, Mezghani and Bejar (2001) Enzyme Microb. Tech. 28, 537–542]. In order to confirm this hypothesis, three mutants were generated. Of these two have a single mutation, N315D or V450G, whereas the third contains both mutations. Analysis of the starch breakdown-profile of these three mutants, as well as of the wild-type, allowed us to conclude that each single mutation induces a small variation in the hydrolysis product. However, the major end product produced by the double mutant shifts from maltopentaose/maltohexaose to maltose/maltotriose, confirming the involvement of these two residues in starch hydrolysis. The superimposition of AmyUS100 model with that of Bacillus licheniformis shows in AmyUS100 an additional loop containing residues Ile214 and Gly215. Remarkably, the deletion of these two residues increases the half-life at 100 °C from 15 min to approx. 70 min. Moreover, this engineered amylase requires less calcium, 25 p.p.m. instead of 100 p.p.m., to reach maximal thermostability.
Plasma-membrane-associated sialidase (NEU3) differentially regulates integrin-mediated cell proliferation through laminin- and fibronectin-derived signalling
Authors: Kato Kengo , Shiga Kiyoto , Yamaguchi Kazunori , Hata Keiko , Kobayashi Toshimitsu , Miyazaki Kaoru , Saijo Shigeru , Miyagi Taeko
Published: March 2006

We have found previously that human plasma-membrane-associated sialidase (NEU3), a key glycosidase for ganglioside degradation, was markedly up-regulated in human colon cancers, with an involvement in suppression of apoptosis. To elucidate the molecular mechanisms underlying increased NEU3 expression, in the present study we investigated its role in cell adhesion of human colon cancer cells. DLD-1 cells transfected with NEU3 exhibited increased adhesion to laminins and consequent cell proliferation, but decreased cell adhesion to fibronectin and collagens I and IV, compared with control cells. When triggered by laminins, NEU3 clearly stimulated phosphorylation of FAK (focal adhesion kinase) and ERK (extracellular-signal-regulated kinase), whereas there was no activation on fibronectin. NEU3 markedly enhanced tyrosine phosphorylation of integrin β4 with recruitment of Shc and Grb-2 only on laminin-5, and NEU3 was co-immunoprecipitated by an anti-(integrin β4) antibody, suggesting that association of NEU3 with integrin β4 might facilitate promotion of the integrin-derived signalling on laminin-5. In addition, the promotion of phosphorylation of integrin β1 and ILK (integrin-linked kinase) was also observed on laminins. GM3 depletion as the result of NEU3 overexpression, assessed by TLC, appeared to be one of the causes of the increased adhesion on laminins and, in contrast, of the decreased adhesion on fibronectin – NEU3 probably having bimodal effects. These results indicate that NEU3 differentially regulates cell proliferation through integrin-mediated signalling depending on the extracellular matrix and, on laminins, NEU3 did indeed activate molecules often up-regulated in carcinogenesis, which may cause an acceleration of the malignant phenotype in cancer cells.
Effects of hypoxia, glucose deprivation and acidosis on phosphatidylcholine synthesis in HL-1 cardiomyocytes. CTP:phosphocholine cytidylyltransferase activity correlates with sarcolemmal disruption
Authors: Sarri Elisabet , Garcia-Dorado David , Abellan Arancha , Soler-Soler Jordi
Published: March 2006

A decrease in [3H]Cho (choline) incorporation in to PtdCho (phos-phatidylcholine) preceded the onset of LDH (lactate dehydrogenase) release in HL-1 cardiomyocytes submitted to simulated ischaemia. This observation led us to examine the role of PtdCho synthesis in sarcolemmal disruption in HL-1 cardiomyocytes. To address this objective we analysed the individual effects of hypoxia, glucose deprivation and acidosis, three prominent components of ischaemia, on the different steps of the Kennedy pathway for the synthesis of PtdCho. Pulse and pulse-chase experiments with [3H]Cho, performed in whole HL-1 cells submitted to hypoxia or normoxia, in the presence or absence of glucose at different pHs indicated first, that CK (choline kinase) was inhibited by hypoxia and acidosis, whereas glucose deprivation exacerbated the inhibition caused by hypoxia. Second, the rate-limiting reaction in PtdCho synthesis, catalysed by CCT (CTP:phosphocholine cytidylyltransferase), was inhibited by hypoxia and glucose deprivation, but unexpectedly activated by acidosis. In cellfree system assays, acidosis inhibited both CK and CCT. In experiments performed in whole cells, the effect of acidosis was likely to be direct on CK, but indirect or intact-cell-dependent on CCT. Since hypoxia and glucose deprivation favoured membrane disruption, but acidosis prevented it, we hypothesized that the modulation of CCT could be an important determinant of cell survival. Supporting this hypothesis, we show that CCT activity in whole-cell experiments clearly correlated with LDH release, but not with ATP concentration. Altogether our results suggest a significant role for CCT activity in sarcolemmal disruption during ischaemia.
Proteomic analysis of mouse kidney peroxisomes: identification of RP2p as a peroxisomal nudix hydrolase with acyl-CoA diphosphatase activity
Authors: Ofman Rob , Speijer Dave , Leen René , Wanders Ronald J. A.
Published: March 2006

Proteomic analysis of mouse kidney peroxisomes resulted in the identification of a novel nudix hydrolase designated RP2p, which is encoded by the D7RP2e gene. RP2p consists of 357 amino acids and contains two conserved domains: a nudix hydrolase domain and a CoA-binding domain. In addition, a PTS (peroxisomal targeting signal) type 1 (Ala-His-Leu) was found at the C-terminus. Analysis of the enzyme characteristics revealed that RP2p is a CoA diphosphatase with activity towards CoA, oxidized CoA and a wide range of CoA esters, including choloyl-CoA and branched-chain fatty-acyl-CoA esters. The enzymatic properties of RP2p indicate that at low substrate concentrations medium and long-chain fatty-acyl-CoA esters are the primary substrates. Enzyme activity was optimal at pH 9 or above, and required the presence of Mg2+ or Mn2+ ions. Subcellular fractionation studies revealed that all CoA diphosphatase activity in mouse kidney is restricted to peroxisomes.
Comparing calpain- and caspase-3-mediated degradation patterns in traumatic brain injury by differential proteome analysis
Authors: Liu Ming Cheng , Akle Veronica , Zheng Wenrong , Dave Jitendra R. , Tortella Frank C. , Hayes Ronald L. , Wang Kevin K. W.
Published: March 2006

A major theme of TBI (traumatic brain injury) pathology is the over-activation of multiple proteases. We have previously shown that calpain-1 and -2, and caspase-3 simultaneously produced αII-spectrin BDPs (breakdown products) following TBI. In the present study, we attempted to identify a comprehensive set of protease substrates (degradome) for calpains and caspase-3. We further hypothesized that the TBI differential proteome is likely to overlap significantly with the calpain- and caspase-3-degradomes. Using a novel HTPI (high throughput immunoblotting) approach and 1000 monoclonal antibodies (PowerBlot™), we compared rat hippocampal lysates from 4 treatment groups: (i) naïve, (ii) TBI (48 h after controlled cortical impact), (iii) in vitro calpain-2 digestion and (iv) in vitro caspase-3 digestion. In total, we identified 54 and 38 proteins that were vulnerable to calpain-2 and caspase-3 proteolysis respectively. In addition, the expression of 48 proteins was down-regulated following TBI, whereas that of only 9 was up-regulated. Among the proteins down-regulated in TBI, 42 of them overlapped with the calpain-2 and/or caspase-3 degradomes, suggesting that they might be proteolytic targets after TBI. We further confirmed several novel TBI-linked proteolytic substrates, including βII-spectrin, striatin, synaptotagmin-1, synaptojanin-1 and NSF (N-ethylmaleimide-sensitive fusion protein) by traditional immunoblotting. In summary, we demonstrated that HTPI is a novel and powerful method for studying proteolytic pathways in vivo and in vitro.
An intersubunit lock-and-key ‘Clasp’ motif in the dimer interface of Delta class glutathione transferase
Authors: Wongsantichon Jantana , Ketterman Albert J.
Published: March 2006

Structural investigations of a GST (glutathione transferase), adGSTD4-4, from the malaria vector Anopheles dirus show a novel lock-and-key ‘Clasp’ motif in the dimer interface of the Delta class enzyme. This motif also appears to be highly conserved across several insect GST classes, but differs from a previously reported mammalian lock-and-key motif. The aromatic ‘key’ residue not only inserts into a hydrophobic pocket, the ‘lock’, of the neighbouring subunit, but also acts as part of the ‘lock’ for the other subunit ‘key’. The ‘key’ residues from both subunits show aromatic ring stacking with each other in a pi–pi interaction, generating a ‘Clasp’ in the middle of the subunit interface. Enzyme catalytic and structural characterizations revealed that single amino acid replacements in this ‘Clasp’ motif impacted on catalytic efficiencies, substrate selectivity and stability. Substitutions to the ‘key’ residue create strong positive co-operativity for glutathione binding, with a Hill coefficient approaching 2. The lock-and-key motif in general and especially the ‘Clasp’ motif with the pi–pi interaction appear to play a pivotal role in subunit communication between active sites, as well as in stabilizing the quaternary structure. Evidence of allosteric effects suggests an important role for this particular intersubunit architecture in regulating catalytic activity through conformational transitions of subunits. The observation of co-operativity in the mutants also implies that glutathione ligand binding and dimerization are linked. Quaternary structural changes of all mutants suggest that subunit assembly or dimerization basically manipulates subunit communication.