bluuebunny/crossref_metadata_2025 huggingface dataset:
High‐performance liquid chromatographic separation of natural and synthetic desulphoglucosinolates and their chemical validation by UV, NMR and chemical ionisation‐MS methods
Authors: Kiddle Guy , Bennett Richard N. , Botting Nigel P. , Davidson Nicola E. , Robertson Avril A. B. , Wallsgrove Roger M.
Published: August 2002

Methods are described for the optimised extraction, desulphation and HPLC separation of desulphoglucosinolates. These methods provide rapid separation, identification and quantitative measurements of glucosinolates extracted from Brassica napus L and related crops, of unusual glucosinolates found in crucifer weed species, and also of synthetic alkylglucosinolates. The desulphoglucosinolates used in these studies were either chemically synthesised (at least one example from each major structural class), or purified from various plant sources. Validation of the identities of the desulphoglucosinolates was by comparison of retention times with standards, and by UV, 1H‐ and 13C‐NMR and chemical ionisation MS analysis. A list of useful species, and the specific tissues, from which high concentrations of standards can be extracted is included. Copyright © 2001 John Wiley & Sons, Ltd.
A rapid capillary gel electrophoresis method for the quantitative determination of RuBisCo in spinach
Authors: Nicholas Kumudini U. K. G. , Forney Charles F. , Paulson Allan T.
Published: August 2002

A capillary gel electrophoretic (CGE) method for the quantitative analysis of RuBisCo in spinach leaves was developed. RuBisCo was resolved into large and small subunits in the presence of sodium dodecyl sulphate (SDS) by the CGE procedure which enabled the determination of the molecular weight of each unit accurately; the values so determined were in close agreement with those reported using other methods. Advantages of CGE over SDS–polyacrylamide gel electrophoresis and high‐pressure gel filtration include decreased sample preparation and analysis time, superior resolution and greater sensitivity permitting reduced sample size and trace analysis. In addition, CGE provided precise quantification of RuBisCo and was demonstrated to be a viable alternative to other available methods of protein analysis. Copyright © 2001 John Wiley & Sons, Ltd.
Variation in uptake of serum screening: the role of service delivery
Authors: Dormandy Elizabeth , Michie Susan , Weinman John , Marteau Theresa M.
Published: August 2002

The present study aimed to determine the extent to which variation in the uptake of serum screening for Down syndrome reflects variation in the way the test is offered. A higher uptake of serum screening was seen at hospitals that offered the blood test as part of a routine visit than at those where screening required a separate visit. The type of screening test offered and whether a reminder was sent were not associated with uptake. Given the consensus that undergoing screening should be the result of an informed choice, further research is needed to determine which methods of offering serum screening facilitate and which impede informed choice. Copyright © 2002 John Wiley & Sons, Ltd.
Intrauterine growth restriction (IUGR): biometric and Doppler assessment
Authors: Galan Henry L. , Ferrazzi Enrico , Hobbins John C.
Published: August 2002

Intrauterine growth restriction (IUGR) is a common complication in pregnancy and influences morbidity and mortality at all stages of life. Historically, the management of IUGR has been dependent on antenatal biophysical testing and umbilical artery Doppler studies. With recent Doppler studies of the fetal central circulation, including intracardiac flows and the ductus venosus, better timing of delivery to minimize morbidity may be possible. This review will provide the reader with tools to diagnose IUGR, more accurately date the IUGR pregnancy with poor dating criteria, and better assess the condition of the IUGR fetus. A brief review of animal models of IUGR is presented to demonstrate research directions for answering human clinical questions and potentially carrying therapeutic intervention from the bench to the bedside. Copyright © 2002 John Wiley & Sons, Ltd.
Alpha‐thalassaemia prenatal diagnosis by two PCR‐based methods
Authors: Kleanthous M. , Kyriacou K. , Kyrri A. , Kalogerou E. , Vassiliades PH. , Drousiotou A. , Kallikas I. , Ioannou P. , Angastiniotis M.
Published: August 2002

In Cyprus all couples carrying α0‐thalassaemia mutations are detected in the course of the thalassaemia carrier screening program and prenatal diagnosis is offered to all of them. Prenatal diagnosis for α‐thalassaemia is routinely done by two independent molecular methods. With the first method, the mutations of the parents are directly determined by gap‐PCR and then the chorionic villus sample (CVS) is examined for the presence of these mutations. With the other method, a (CA)n repeat polymorphic site located between the ψα1‐ and α2‐globin genes is used for determining the presence or absence of the normal and mutant alleles. In the period from 1995 to 1999, molecular analysis of 46 couples in which haematological data were consistent with deletion of two α‐globin genes in both partners indicated that only 13 of them were actually at risk for haemoglobin (Hb) Bart's hydrops fetalis and prenatal diagnosis was provided in 16 pregnancies. The molecular diagnosis was possible in all cases with the use of both gap‐PCR and (CA)n repeat polymorphisms analysis. No misdiagnosed cases for α‐thalassaemia have been reported to date. Copyright © 2001 John Wiley & Sons, Ltd.
Antenatal gene tests in low‐risk pregnancies: molecular screening for aspartylglucosaminuria (AGU) and infantile neuronal ceroid lipofuscinosis (INCL) in Finland
Authors: Kallinen Juuso , Heinonen Seppo , Palotie Aarno , Mannermaa Arto , Ryynanen Markku
Published: August 2002

Approximately one in five subjects in Finland carries some gene defect associated with 30 diseases belonging to the Finnish disease heritage, and about one in 500 children born is affected. Almost all carriers, women and men, are unaware of their condition. Recent advances in molecular medicine have offered the possibility of population‐based carrier screening for recessive disorders. We studied acceptance and attitudes to antenatal screening for aspartylglucosaminuria (AGU) and infantile neuronal ceroid lipofuscinosis (INCL).

From January 1995 until December 1996 carrier tests were offered at Kuopio City Health Center, free of charge to all pregnant women attending maternity care units. Women found to be carriers of AGU (n=47) or INCL (n=14) underwent detailed genetic counseling, and their male partners were also offered the test. If both partners appeared to be carriers we offered prenatal testing (n=1). No affected fetuses were detected. Attitudes towards the gene test were elicited by means of a questionnaire.

Altogether 87% of pregnant women elected to undertake the gene tests. Antenatal screening for gene defects was feasible and well accepted, and it provided an effective way to find carriers of genetic diseases and to incorporate prenatal testing into this process. Copyright © 2001 John Wiley & Sons, Ltd.
The effect of hexamethylene diisocyanate modified ALCELL lignin as a coupling agent on the flexural properties of oil palm empty fruit bunch – polypropylene composites
Authors: Rozman H D , Tan K W , Kumar R N , Abubakar A
Published: August 2002

ALCELL lignin has been employed as a coupling agent in oil palm empty fruit bunch (EFB)–polypropylene (PP) composites. The lignin has been chemically modified with hexamethylene diisocyanate (HMDI). Evidence for the reaction between HMDI and lignin has been observed by using Fourier transform infrared (FTIR) analysis. The effect of lignin as a coupling agent on the flexural properties has been studied. The results show that the HMDI‐modified lignin is able to impart greater compatibility between EFB and PP. This is reflected in the greater flexural strength shown by the composites with HMDI‐modified lignin than those with the unmodified lignin. Scanning electron microscopy studies show that HMDI‐modification of lignin results in a better blending and compatibility between lignin and PP matrix. The glass transition temperature of lignin increases as the level of HMDI modification is increased.

© 2001 Society of Chemical Industry
Addition‐cure phenolic resins based on propargyl ether functional novolacs: synthesis, curing and properties
Authors: Bindu R L , Reghunadhan Nair C P , Ninan K N
Published: August 2002

Thermosetting phenolic resins, bearing varying extents of propargyl ether groups (PN resins), have been synthesized by the Williamson reaction of a novolac with propargyl bromide and the products characterized. The resin precursors were cured through Claisen rearrangement of the propargyl ether groups and thermal polymerization. The activation energy for thermal cure is substantially lower than that of model bispropargyl ether compounds but is quite independent of the degree of functionalization. The isothermal cure profile, extrapolated from non‐isothermal DSC kinetics studies is consistent with the results from DMA studies. The mechanical properties of glass composites of the resins, of varying propargyl contents, reveal good consolidation of the interphases, evident from the initial gain in both interlaminar shear strength (ILSS) and flexural strength. The benefits of better resin–reinforcement interactions are not retained on crosslinking the resin further, wherein the composite fails by a combination of fibre debonding and brittle fracture of the matrix. Although the resins show better thermal stability than cured resoles, a higher extent of propargylation is detrimental for the thermal stability. Resins with moderate propargylation show good mechanical and thermal properties.

© 2001 Society of Chemical Industry
Modification of polysiloxane polymers for biomedical applications: a review
Authors: Abbasi Farhang , Mirzadeh Hamid , Katbab Ali‐Asgar
Published: August 2002

This paper reviews methods of modifying polydimethylsiloxane (PDMS) polymers to improve their properties for biomedical applications. The modification methods are discussed under three different categories: bulk, surface and other modification techniques. Surface modification techniques include physical and chemical techniques to modify polymer surfaces. Bulk modification techniques include blending, copolymerization, interpenetrating polymer networks (IPNs) and functionalization. The third category includes less common modification techniques.

© 2001 Society of Chemical Industry
End‐group determination in poly(ethylene terephthalate) by infrared spectroscopy
Authors: Al‐AbdulRazzak Sami , Lofgren Elizabeth A , Jabarin Saleh A
Published: August 2002

A complete infrared (IR) spectroscopy experimental procedure was used to determine end‐group concentrations of poly(ethylene terephthalate) (PET). The correlations of the hydroxyl and carboxyl units were derived independently for accurate calibration results. The intermediate monomer of PET, bis(hydroxyethyl terephthalate), was used to prepare hydroxyl end‐group standards and titration measurements were used to determine the carboxyl content for the carboxyl end‐group standards. A double‐Gaussian form equation was defined to account for the interference between the hydroxyl and the carboxyl absorbance peaks in the PET IR spectrum. Some deviation was found from the assumption traditionally used for end‐group determination, stating that carboxyl and hydroxyl are the only end‐group units available in PET.

© 2002 Society of Chemical Industry
Cadmium telluride PV module manufacturing at BP Solar
Authors: Cunningham D. , Rubcich M. , Skinner D.
Published: August 2002

BP Solar has built a 10 MW capacity CdTe thin‐film (Apollo®) manufacturing plant in Fairfield, California. The plant is on the verge of commercialization and is expected to produce several megawatts of 61 × 155 cm (24 × 61‐inch) thin‐film modules (nominally 80 W) in 2001. This paper describes the basic Apollo® process steps, the recent advances made in the Apollo® CdTe technology, the state of the art CdTe reactor with its sophisticated design and control features and various techniques used to characterize the semiconductor materials. Module performance and reliability results are also summarized. An NREL‐confirmed module efficiency of 10.6% is reported for a 0.94 m2 module with a maximum power of 91.5 W. Indoor stress testing and outdoor performance test beds are described, and the data presented show good indoor stability under various stress conditions. Copyright © 2002 John Wiley & Sons, Ltd.
Evaluation of the peacemakers program: School‐based violence prevention for students in grades four through eight
Authors: Shapiro Jeremy P. , Burgoon Joella D. , Welker Carolyn J. , Clough Joseph B.
Published: August 2002

This study evaluated the violence prevention effects of The Peacemakers Program, a school‐based intervention for students in grades four through eight. The program includes a primary prevention component delivered by teachers and a remedial component implemented by school psychologists and counselors with referred students. The teacher‐delivered component consists of a psychoeducational curriculum and procedures for infusing program content into the school environment. The study included almost 2,000 students in an urban public school system, with pre‐ and post‐program assessment and comparison to a control group. There were significant, positive program effects on six of the seven variables assessed, including knowledge of psychosocial skills, self‐reported aggression, and teacher‐reported aggression, with a 41% decrease in aggression‐related disciplinary incidents and a 67% reduction in suspensions for violent behavior. On some outcome variables, intervention effects were stronger for boys than girls and for middle school compared to upper elementary school students. © 2002 John Wiley & Sons, Inc.
Sequential poly(ester amide)s based on glycine, diols, and dicarboxylic acids: Thermal polyesterification versus interfacial polyamidation. Characterization of polymers containing stiff units
Authors: Asín L. , Armelin E. , Montané J. , Rodríguez‐Galán A. , Puiggalí J.
Published: August 2002

Sequential poly(ester amide)s derived from glycine were synthesized by a two‐step method, involving a final thermal polyesterification. Molecular weights were in general higher than those obtained with the previously reported synthesis on the basis of interfacial polyamidation. Polymers with stiff units like oxaloyl or terephthaloyl residues were thermally characterized and their degradability studied by using different types of enzymes. Polymers containing short diols are degradable in papain solutions, the degradation rate being higher for oxalic derivatives. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 4283–4293, 2001
Synthesis of statistical glycidyl methacrylate‐n‐vinyl pyrrolidone copolymers and their reaction with naproxen
Authors: Sánchez‐Chaves Manuel , Martínez Gerardo , López Madruga Enrique , Fernández‐Monreal Carmen
Published: August 2002

Free‐radical copolymerization of glycidyl methacrylate (GMA) with N‐vinylpyrrolidone (VPD) was carried out at 50 °C using 3.0 mol · L−1 of N,N′‐dimethylformamide solution and 9.0 · 10−3 mol · L−1 of 2,2′‐azobisisobutyronitrile as an initiator. The modification reaction of GMA‐VPD copolymers with a model bioactive carboxylic acid, 6‐methoxy‐α‐methyl‐2‐naphthaleneacetic acid (naproxen), was studied in the homogeneous phase using basic catalysts. The influence of the type of catalyst and the GMA content was evaluated. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1192–1199, 2002
Evaluation of compatibility and properties of biodegradable polyester blends
Authors: John Jacob , Mani Ramaswamy , Bhattacharya Mrinal
Published: August 2002

Three different biodegradable polyesters, namely, polycaprolactone (PCL), polybutylene succinate (BIONOLLE), and a copolyester of adipic acid, terephthalic acid, and 1,4‐butanediol (EASTAR) were melt‐blended using a twin‐screw extruder. The percentage composition of each of the aforementioned polymers was varied to obtain different blends, and the mechanical properties were evaluated. Selected blends showed significant improvement in tensile strength as compared with the individual polymers used to prepare the blend. The compatibility between the polymer phases was examined via Fourier transform infrared (FTIR) and nuclear magnetic resonace (NMR) spectroscopy as well as dynamic mechanical analysis. FTIR and NMR data confirmed the occurrence of hydrogen‐bonding and ester‐interchange reactions. Thermal properties and changes in crystallinity of the blends were examined with differential scanning calorimetry and X‐ray diffraction. A considerable increase in crystallinity was shown by the blend system containing BIONOLLE/PCL. The morphology of the blends was observed and correlated to the improved mechanical properties of the blend system. Results revealed an intermediate multiphase system in which a significant degree of mixing was achieved through the chemical interaction of the functional groups present, while using the twin‐screw extruder. Significant improvement in mechanical properties of some blends was observed, and information about the miscibility of these polyesters is provided. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2003–2014, 2002
Copper(I)‐mediated radical polymerization of methacrylates in aqueous solution
Authors: Perrier Sébastien , Armes Steven P. , Wang X. S. , Malet F. , Haddleton David M.
Published: August 2002

α‐Methoxypolyethylene oxide methacrylate was polymerized by copper(I)‐mediated living radical polymerization in aqueous solution to give polymers with controlled number‐average molecular masses and narrow polydispersities. When equimolar quantities of initiator with respect to copper(I) bromide were used, the reaction was extremely fast with quantitative conversion achieved in less than 5 min at ambient temperature. However, the molecular weight distribution was broad, and control over the number‐average molecular weight (Mn) growth was extremely poor; this is ascribed to an increase in termination because of the increased rate as a result of the coordination of water at the copper center. The complex formed between copper(I) bromide and N‐(n‐propyl)‐2‐pyridylmethanimine, bis[N‐(n‐propyl)‐2‐pyridylmethanimine]copper(I), was demonstrated to be stable in aqueous solution by 1H NMR over 10 h at 25 °C. However, on increasing the temperature to 50 °C, decomposition occurred rapidly. Thus, polymerization temperatures were maintained at ambient temperature. When longer alkyl chains were utilized in the ligand, that is, pentyl and octyl, the complex acted as a surfactant leading to heterogeneous solutions. When the catalyst concentration was reduced by two orders of magnitude, the rate of polymerization was reduced with 100% conversion achieved after 60 min with the Mn of the final product being higher than that predicted and the polydispersity equal to 1.43. Copper(II) was added as an inhibitor to circumvent these problems. When 10% of Cu(I) was replaced by Cu(II) {[Cu(I)] + [Cu(II)]/[I] = 1/100}, the mass distribution showed a bimodal distribution, and the rate of polymerization decreased significantly. With a catalyst composition [Cu(I)]/[Cu(II)] = 0.5/0.5 {[Cu(I)] + [Cu(II)]}/[I] = 1/100, polymerization proceeded slowly with 80% conversion reached after 22 h. Thus, the concentration of Cu(I) was further reduced with [Cu(I)]/[Cu(II)] = 10/90, {[Cu(I)] + [Cu(II)]}/[I] = 1/100. The system then contained [Initiator]/[Cu(I)] = 1000/1 and [I]/[Cu(II)] = 1000/9. Under these conditions, the reaction reached 50% after 5 h with the polymer having both an Mn close to the theoretical value and a narrow polydispersity of PDi = 1.15. Optimum results were obtained by increasing the amount of catalyst. When a ratio of [Cu(I)]/[Cu(II)] = 10/90 with a ratio of [Cu]/[I] = 1/1, a conversion of 100% was achieved after less than 20 h, leading to a product having Mn = 8500 and PDi = 1.15. Decreasing the amount of Cu(II) relative to Cu(I) to [Cu(I)]/[Cu(II)] = 0.5/0.5 (maintaining the overall amount of copper) led to 100% conversion after 75 min: Mn = 9500, PDi = 1.10. Block copolymers have been demonstrated by sequential monomer addition with excellent control over Mn and PDi. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1696–1707, 2001
Poly(pyridinium salt)s with stilbene or distyrylbenzene chromophores
Authors: Spiliopoulos Ioakim K. , Mikroyannidis John A.
Published: August 2002

A new series of poly(pyridinium salt)s that contained side stilbenyl groups or p‐distirylbenzene segments in the main chain were synthesized from the reactions of bis(pyrylium salts) with diamines. They were characterized by viscometry, Fourier transform infrared spectroscopy, NMR, X‐ray scattering, differential scanning calorimetry, thermomechanical analysis, ultraviolet–visible analysis, and luminescence spectroscopy. The polymers were amorphous and soluble in polar aprotic solvents such as dimethylacetamide, dimethylformamide, and dimethyl sulfoxide. The glass‐transition temperatures were in the range of 59–123 °C. These polymers had initial decomposition temperatures of 240–295 °C and afforded anaerobic char yields of 29–53% at 800 °C. Both the absorption and photoluminescence (PL) spectra of the polymers were studied, and the PL quantum yields in solution were determined. The polymers showed violet‐blue fluorescence in solution with PL maxima at 408–416 nm and violet‐green fluorescence in thin film with PL maxima at 454–523 nm. The structure of the diamine utilized for the preparation of the polymers did not influence their PL maxima. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2454–2462, 2001
Copolymerization of carbon dioxide and propylene oxide with Ln(CCl3COO)3‐based catalyst: The role of rare‐earth compound in the catalytic system
Authors: Liu Binyuan , Zhao Xiaojiang , Wang Xianhong , Wang Fosong
Published: August 2002

A highly alternative copolymer of carbon dioxide and propylene oxide was obtained using a lanthanide trichloroacetates‐based ternary catalyst. The rare‐earth compound in the ternary catalyst was critical to dramatically raise the yield and molecular weight of the copolymer in addition to maintaining a high alternating ratio of the copolymer. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2751–2754, 2001
Optical properties and orientation in polyethylene blown films
Authors: Bafna Ayush , Beaucage Gregory , Mirabella Francis , Skillas George , Sukumaran Satish
Published: August 2002

We report structural factors affecting the optical properties of blown polyethylene films. Two types of blown polyethylene films of similar degrees of crystallinity were made from (1) single‐site‐catalyst high‐density polyethylene (HDPE; STAR α) and (2) Ziegler–Natta‐catalyst HDPE (ZN) resins. The STAR α film exhibited high clarity and gloss, whereas the ZN film was turbid. Small‐angle X‐ray scattering (SAXS), small‐angle light scattering (SALS), and optical microscopy gave quantitative and qualitative information regarding structure and orientation in the films. A new approach is described for determining the three‐dimensional lamellar normal orientation from SAXS. Both the clear STAR α and turbid ZN films had similar lamellar crystalline structures and long periods but displayed different degrees of orientation. It is demonstrated that optical haze is related to surface features that seem to be linked to the bulk morphology. The relationship between haze and structural orientation is described. The lamellar orientation is linked to rodlike structures seen in optical microscopy and SALS through a stacked lamellar or cylindrite morphology on a nanometer scale and through a fiberlike morphology on a micrometer scale. The micrometer‐scale, rodlike structures seem directly related to surface roughness in a comparison of index‐matched immersion and surface micrographs. The higher haze and lower gloss of the ZN film was caused by extensive surface roughness not observed in the STAR α film. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2923–2936, 2001
X‐ray photoelectron spectroscopy study of oxygen‐containing polymer [poly(vinyl methyl ether), poly(vinyl methyl ketone), and poly(methyl methacrylate)] surfaces metalized by vacuum‐deposited nickel
Authors: Bébin Philippe , Prud'Homme Robert E.
Published: August 2002

Surfaces of poly(vinyl methyl ether) (PVME), poly(vinyl methyl ketone) (PVMK), and poly(methyl methacrylate) (PMMA) were covered with different thicknesses of nickel with a metal‐vapor‐condensation method, and the metal–polymer interfaces were analyzed by X‐ray photoelectron spectroscopy. In the very first steps of the metalization, it was found that a systematic degradation of the polymer surface occurs through CO or CO2 losses, depending on the polymer functionalities. Then, at the interface with the polymer, the condensed metal reacts by oxidization with the oxygen atoms that are still available after the surface degradation. Nickel oxide is then formed at the interface, whatever the nature of the initial polymer functional group. These new oxide species are not chemically bonded to the polymer structure, and their formation is not affected by the type of bond existing between oxygen and carbon atoms in the original polymer. Finally, the accumulation of metal on the substrate induces an amorphization of the polymer carbon structure because thermal energy is transferred from the metal coating to the polymer. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 82–94, 2002
Polypropylene/talc composites modified by a succinyl‐fluorescein grafted atactic polypropylene: A thermal and mechanical study under dynamic conditions
Authors: García‐Martínez J. Ma. , Laguna O. , Areso S. , Collar E. P.
Published: August 2002

This article reports on the interfacial modifications induced by different amounts of a succinyl‐fluorescein grafted atactic polypropylene (a‐PP‐SF) as a truly interfacial agent in polypropylene/talc composite materials. The a‐PP‐SF used, which contains 4% grafts, was previously obtained in our laboratory by chemical modification of a byproduct from industrial polymerization reactors. Thermal and mechanical analyses of composites, performed under dynamic conditions, led to the correlation of parameters at the microscopic scale with others at the macroscopic scale. Thus, the interfacial effect caused by different amounts of a‐PP‐SF in the composite can be concluded by observations made at either scale. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1371–1382, 2002
Confirmation of the crystal structure of poly(p‐phenylene benzobisoxazole) by the X‐ray structure analysis of model compounds and the energy calculation
Authors: Tashiro Kohji , Hama Hisakatsu , Yoshino Jun‐Ichi , Abe Yukihiro , Kitagawa Tooru , Yabuki Kazuyuki
Published: August 2002

To check the previously proposed crystal structure of poly(p‐phenylene benzobisoxazole) [PBO], we performed an X‐ray structure analysis for single crystals of low molecular weight model compounds with the following chemical formulas:
magnified image
Both of these two model compounds show essentially the same molecular and subcell structures as those of PBO: the molecular chains take an almost perfect planar conformation and are packed together with a relative height between the adjacent chains of about 3 Å along the chain axis, although for the polymer the chains are shifted by the same value but in a disordered mode with respect to the direction of the shift (upward or downward), different from the regular packing in model compounds. These structural features are reproduced well with energy calculations. Structural ordering in PBO fibers caused by heat treatment at high temperatures, as clarified by X‐ray diffraction measurement, are interpreted on the basis of the energy calculations. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1296–1311, 2001
Melt properties and crystal morphology of polydodecamide plasticized by benzenesulfonamides
Authors: De Groote Ph. , Jonas A. M. , Devaux J. , Godard P.
Published: August 2002

The melt of polydodecamide (PA‐12) shows a significant viscosity decrease upon incorporation of benzenesulfonamide plasticizers (BSAs), this effect being maximum for a monofunctional BSA with a 12‐carbon‐atom‐long alkyl chain. Nonexhaustive X‐ray diffraction analysis developed on isothermally crystallized samples validated a two‐phase model for describing PA‐12 plasticized by N‐(n‐butyl)benzenesulfonamide (BBSA). The massive presence of BBSA between the lamellar crystals was established, and lamellar fragmentation was also observed. Further, a steady increase in PA‐12 crystallinity with an increasing BBSA content was evident (and confirmed by DSC) and is consistent with the plasticizer easing the mobility of polymer chains during crystallization. Large melting point depressions resulting from both polymer–plasticizer miscibility and lamellar fragmentation were observed with several mono‐ and bifunctional BSA plasticizers. Phase separation in PA‐12 solid state was only observed at 20 mol % of ϕSO2NH2, alhough miscibility occurred in the melt. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2022–2034, 2001
Crystallization kinetics and crystallization behavior of syndiotactic polystyrene/clay nanocomposites
Authors: Tseng Chen‐Rui , Lee Hsin‐Yi , Chang Feng‐Chih
Published: August 2002

We investigated the effects of montmorillonite (clay) on the crystallization kinetics of syndiotactic polystyrene (sPS) with isothermal differential scanning calorimetry analyses. The clay was dispersed into the sPS matrix via melt blending on a scale of 1–2 nm or up to about 100 nm, depending on the surfactant treatment. For a crystallization temperature of 240 °C, the isothermal crystallization data were fitted well with the Avrami crystallization equation. Crystallization data on the kinetic parameters (i.e., the crystallization rate constant, Avrami exponent, clay content, and clay/surfactant cation‐exchange ratio) were also investigated. Experimental results indicated that the crystallization rate constant of the sPS nanocomposite increased with increasing clay content. The clay played a vital role in facilitating the formation on the thermodynamically more favorable all‐β‐form crystal when the sPS was melt‐crystallized. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2097–2107, 2001
Effect of pacifier use on oral breathing in healthy newborn infants
Authors: Cozzi Francesco , Morini Francesco , Tozzi Claudio , Bonci Enea , Cozzi Denis A.
Published: August 2002

We tested the hypothesis that the use of a pacifier may affect the ability of some term infants to maintain effective oral breathing during prolonged nasal occlusion. Three nasal occlusion tests without a pacifier and 3 with a pacifier were alternately carried out in 20 healthy term infants (age 2–5 days). Once the infant commenced oral breathing, nasal occlusion was continued for up to 90 sec (prolonged nasal occlusion), provided the infant did not start crying and that arterial oxygen saturation (SaO2) did not drop to ≤ 80%. The response to nasal occlusion was considered maladaptive if oral breathing was accomplished with signs of upper airway obstruction.

After nasal occlusion, the infants succeeded in starting oral breathing in all instances after a delay which was strongly correlated to the drop in SaO2 (P < 0.001). Once the infants commenced oral breathing, 17/20 infants presented a maladaptive response to 62% of all tests without pacifier, whereas 10/20 infants presented a maladaptive response to 30% of all tests with a pacifier in place (P < 0.001). Following prolonged nasal occlusion, 18 of 19 infants presented a maladaptive response to 84% of all tests without pacifier, whereas 12 of 19 infants presented a maladaptive response to 41% of all tests with a pacifier in place (P < 0.001). Thus, after prolonged nasal occlusion with or without pacifier, the drop in mean SaO2 from baseline values changed in accordance with an appropriate and maladaptive response (−4 ± 1 vs. −7 ± 1; P < 0.001).

We conclude that normal term infants often present with a maladaptive response to prolonged nasal occlusion. The use of a pacifier enhances the infant's ability to maintain a more adequate oral air flow. Pediatr Pulmonol. 2002; 33:368–373. © 2002 Wiley‐Liss, Inc.
Caspase‐8 activation is necessary but not sufficient for tumor necrosis factor‐related apoptosis‐inducing ligand (TRAIL)‐mediated apoptosis in the prostatic carcinoma cell line LNCaP
Authors: Rokhlin Oskar W. , Guseva Natalya V. , Tagiyev Agshin F. , Glover Rebecca A. , Cohen Michael B.
Published: August 2002

BACKGROUND

The differential sensitivity of tumor cells to TRAIL‐induced apoptosis may be mediated by different intracellular inhibitors of apoptosis, and only a few reports have described the pathway(s) that are activated in response to TRAIL in prostate cells.

METHODS

LNCaP was transfected with a dominant‐negative form of FADD (FADD‐DN) and cells were selected in the presence of hygromycin. Cell viability was estimated by calcein assay. Apoptosis was estimated by caspase activation using both fluorogenic substrastes and Western blot analysis of activated caspases. To detect cytochrome c release, mitochondria‐free cytosol was prepared and Western blot analysis was performed.

RESULTS

LNCaP is resistant to TRAIL but TRAIL transiently induces DEVDase activity and activation of caspase‐8; caspase‐2, ‐3, ‐7, and ‐9 were not activated. Wortmannin, an inhibitor of the PI3K/Akt pathway, converted the phenotype of LNCaP from TRAIL‐resistant to ‐sensitive. In the presence of wortmannin TRAIL induced activation of caspase‐2, ‐3, ‐7, ‐8, and ‐9, as well as dissipation of mitochondrial transmembrane potential and release of cyto‐chrome c from mitochondria into the cytosol. In addition, combined TRAIL and wortmannin treatment resulted in cleavage of several proteins: PARP, Akt, p21/WAF1, and MDM2 as well as dephosphorylation of Akt. The proteolysis of p21/WAFI and Akt, which are known survival factors, presumably amplify the apoptotic cascade in LNCaP. Transfection of FADD‐DN in LNCaP resulted in inhibition of caspase activation as well as in resistance to combined treatment with TRAIL and wortmannin.

CONCLUSIONS

These results suggest that caspase‐8 activation is necessary but not sufficient for TRAIL‐mediated apoptosis and is presumably blocked downstream of caspase‐8 by the PI3K/Akt pathway. Prostate 52: 1–11, 2002. © 2002 Wiley‐Liss, Inc.
Folding of a small helical protein using hydrogen bonds and hydrophobicity forces
Authors: Favrin Giorgio , Irbäck Anders , Wallin Stefan
Published: August 2002

A reduced protein model with five to six atoms per amino acid and five amino acid types is developed and tested on a three‐helix‐bundle protein, a 46‐amino acid fragment from staphylococcal protein A. The model does not rely on the widely used Gō approximation, which ignores non‐native interactions. We find that the collapse transition is considerably more abrupt for the protein A sequence than for random sequences with the same composition. The chain collapse is found to be at least as fast as helix formation. Energy minimization restricted to the thermodynamically favored topology gives a structure that has a root‐mean‐square deviation of 1.8 Å from the native structure. The sequence‐dependent part of our potential is pairwise additive. Our calculations suggest that fine‐tuning this potential by parameter optimization is of limited use. Proteins 2002;47:99–105. © 2002 Wiley‐Liss, Inc.
Simulations of ion current in realistic models of ion channels: The KcsA potassium channel
Authors: Burykin A. , Schutz C. N. , Villá J. , Warshel A.
Published: August 2002

Realistic studies of ion current in biologic channels present a major challenge for computer simulation approaches. All‐atom molecular dynamics simulations involve serious time limitations that prevent their use in direct evaluation of ion current in channels with significant barriers. The alternative use of Brownian dynamics (BD) simulations can provide the current for simplified macroscopic models. However, the time needed for accurate calculations of electrostatic energies can make BD simulations of ion current expensive. The present work develops an approach that overcomes some of the above challenges and allows one to simulate ion currents in models of biologic channels. Our method provides a fast and reliable estimate of the energetics of the system by combining semimacroscopic calculations of the self‐energy of each ion and an implicit treatment of the interactions between the ions, as well as the interactions between the ions and the protein‐ionizable groups. This treatment involves the use of the semimacroscopic version of the protein dipole Langevin dipole (PDLD/S) model in its linear response approximation (LRA) implementation, which reduces the uncertainties about the value of the protein “dielectric constant.” The resulting free energy surface is used to generate the forces for on‐the‐fly BD simulations of the corresponding ion currents. Our model is examined in a preliminary simulation of the ion current in the KcsA potassium channel. The complete free energy profile for a single ion transport reflects reasonable energetics and captures the effect of the protein‐ionized groups. This calculated profile indicates that we are dealing with the channel in its closed state. Reducing the barrier at the gate region allows us to simulate the ion current in a reasonable computational time. Several limiting cases are examined, including those that reproduce the observed current, and the nature of the productive trajectories is considered. The ability to simulate the current in realistic models of ion channels should provide a powerful tool for studies of the biologic function of such systems, including the analysis of the effect of mutations, pH, and electric potentials. Proteins 2002;47:265–280. © 2002 Wiley‐Liss, Inc.
Expression in Pichia pastoris and characterization by circular dichroism and NMR of rhodostomin
Authors: Guo Rey‐Ting , Chou Li‐Jer , Chen Yen‐Chin , Chen Chiu‐Yueh , Pari Koteppa , Jen Chauying J. , Lo Szecheng J. , Huang Shou‐Ling , Lee Chun‐Yann , Chang Tsai‐Wang , Chaung Woei‐Jer
Published: August 2002

Rhodostomin (Rho) is a snake venom protein isolated from Calloselasma rhodostoma. Rho is a disintegrin that inhibits platelet aggregation by blocking the binding of fibrinogen to the integrin αIIbβ3 of platelets. Rho produced in Escherichia coli inhibited platelet aggregation with a KI value of 263 nM. Although functional, Rho produced in E. coli is misfolded based on our 2D and 3D NMR studies. In order to correct the folding problem, Rho was expressed in Pichia pastoris. The recombinant Rho expressed in P. pastoris inhibited platelet aggregation with a resulting KI value of 70 nM. This is the same potency as that of native Rho. CD analysis showed that the secondary structures of Rho are pH‐independent and contain 3.5–7.9% α‐helix, 48.2–50.5% β‐structures, and 42.3–47% coil. The sequential assignment and structure analysis of Rho were obtained using 2D and 3D 15N‐edited NMR spectra. These results provide the first direct evidence that highly disulfide‐bonded disintegrin can be expressed in P. pastoris with the correct fold. This evidence may serve as the basis for exploring the structure and function relationships as well as the dynamics of disintegrin and its variants. Proteins 2001;43:499–508. © 2001 Wiley‐Liss, Inc.
Crystal structure of an aldehyde reductase Y50F mutant‐NADP complex and its implications for substrate binding
Authors: Ye Qilu , Hyndman David , Green Nancy , Li Xuhong , Korithoski Bryan , Jia Zongchao , Flynn T. Geoffrey
Published: August 2002

Pig aldehyde reductase containing the active site mutation tyrosine(50) to phenylalanine has been crystallized in the presence of the cofactor NADP(H) to a resolution of 2.2 Å. This structure clearly shows loss of the tyrosine hydroxyl group and no other significant perturbations compared with previously determined structures. The mutant binds cofactor (both oxidized and reduced) more tightly than the wild‐type enzyme but shows a complete lack of binding of the aldehyde reductase inhibitor barbitone, as determined by fluorescence titrations. Numerous attempts at preparing a ternary complex with a range of small aldehyde substrates were unsuccessful. This result, in addition to the inability of the mutant protein to bind the inhibitor, provides strong evidence for the proposal that the tyrosine hydroxyl group is essential for substrate binding in addition to catalysis. Proteins 2001;44:12–19. © 2001 Wiley‐Liss, Inc.
Solution structure and dynamics of ribonuclease Sa
Authors: Laurents Douglas , Pérez‐Cañadillas José Manuel , Santoro Jorge , Rico Manuel , Schell David , Pace C. Nick , Bruix Marta
Published: August 2002

We have used NMR methods to characterize the structure and dynamics of ribonuclease Sa in solution. The solution structure of RNase Sa was obtained using the distance constraints provided by 2,276 NOEs and the C6C96 disulfide bond. The 40 resulting structures are well determined; their mean pairwise RMSD is 0.76 Å (backbone) and 1.26 Å (heavy atoms). The solution structures are similar to previously determined crystal structures, especially in the secondary structure, but exhibit new features: the loop composed of Pro 45 to Ser 48 adopts distinct conformations and the rings of tyrosines 51, 52, and 55 have reduced flipping rates. Amide protons with greatly reduced exchange rates are found predominantly in interior β‐strands and the α‐helix, but also in the external 3/10 helix and edge β‐strand linked by the disulfide bond. Analysis of 15N relaxation experiments (R1, R2, and NOE) at 600 MHz revealed five segments, consisting of residues 1–5, 28–31, 46–50, 60–65, 74–77, retaining flexibility in solution. The change in conformation entropy for RNase SA folding is smaller than previously believed, since the native protein is more flexible in solution than in a crystal. Proteins 2001;44:200–211. © 2001 Wiley‐Liss, Inc.
Focusing of the electrostatic potential at EF‐hands of calbindin D9k: Titration of acidic residues
Authors: Kesvatera Tõnu , Jönsson Bo , Thulin Eva , Linse Sara
Published: August 2002

Biological functions for a large class of calmodulin‐related proteins, such as target protein activation and Ca2+ buffering, are based on fine‐tuned binding and release of Ca2+ ions by pairs of coupled EF‐hand metal binding sites. These are abundantly filled with acidic residues of so far unknown ionization characteristics, but assumed to be essential for protein function in their ionized forms. Here we describe the measurement and modeling of pKa values for all aspartic and glutamic acid residues in apo calbindin D9k, a representative of calmodulin‐related proteins. We point out that while all the acidic residues are ionized predominantly at neutral pH, the onset of proton uptake by Ca2+ ligands with high pKa under these conditions may have functional implications. We also show that the negative electrostatic potential is focused at the bidental Ca2+ ligand of each site, and that the potential is significantly more negative at the N‐terminal binding site. Proteins 2001;45:129–135. © 2001 Wiley‐Liss, Inc.
Classical molecular interaction potentials: Improved setup procedure in molecular dynamics simulations of proteins
Authors: Gelpí Josep Lluis , Kalko Susana G. , Barril Xavier , Cirera Jordi , de la Cruz Xavier , Luque F. Javier , Orozco Modesto
Published: August 2002

The latest version of the classical molecular interaction potential (CMIP) has the ability to predict the position of crystallographic waters in several proteins with great accuracy. This article analyzes the ability of the CMIP functional to improve the setup procedure of the molecular system in molecular dynamics (MD) simulations of proteins. To this end, the CMIP strategy is used to include both water molecules and counterions in different protein systems. The structural details of the configurations sampled from trajectories obtained using the CMIP setup procedure are compared with those obtained from trajectories derived from a standard equilibration process. The results show that standard MD simulations can lead to artifactual results, which are avoided using the CMIP setup procedure. Because the CMIP is easy to implement at a low computational cost, it can be very useful in obtaining reliable MD trajectories. Proteins 2001;45:428–437. © 2001 Wiley‐Liss, Inc.
Structure of Met‐enkephalin in explicit aqueous solution using replica exchange molecular dynamics
Authors: Sanbonmatsu K.Y. , García A.E.
Published: August 2002

Replica exchange molecular dynamics (MD) simulations of Met‐enkephalin in explicit solvent reveal helical and nonhelical structures. Four predominant structures of Met‐enkephalin are sampled with comparable probabilities (two helical and two nonhelical). The energy barriers between these configurations are low, suggesting that Met‐enkephalin switches easily between configurations. This is consistent with the requirement that Met‐enkephalin be sufficiently flexible to bind to several different receptors. Replica exchange simulations of 32 ns are shown to sample approximately five times more configurational space than constant temperature MD simulations of the same duration. The energy landscape for the replica exchange simulation is presented. A detailed study of replica trajectories demonstrates that the significant increases in temperature provided by the replica exchange technique enable transitions from nonhelical to helical structures that would otherwise be prevented by kinetic trapping. Met‐enkephalin (Type Entrez Proteins; Value A61445; Service Entrez Proteins) Proteins 2002;46:225–234. Published 2001 Wiley‐Liss, Inc.
Mode of action of new diethylamines in lycopene cyclase inhibition and in photosystem II turnover
Authors: Fedtke Carl , Depka Brigitte , Schallner Otto , Tietjen Klaus , Trebst Achim , Wollweber Detlef , Wroblowsky Heinz‐Jürgen
Published: August 2002

The new bleaching herbicidal compound N,N‐diethyl‐N‐(2‐undecynyl)amine (NDUA) is identified here as an inhibitor of lycopene cyclase and is compared with the known cyclase inhibitors N,N‐diethyl‐N‐[2‐(4‐chlorophenylthio)ethyl]amine (CPTA) and N,N‐diethyl‐N‐[2‐(4‐methylphenoxy)ethyl]amine (MTPA). HPLC separation of chloroplast pigments shows lycopene accumulation in NDUA treated tissue. Variation in chain length of the undecynylamine moeity of NDUA from 7 to 21 C atoms reveals an optimum of 11 to 14 C atoms for herbicidal activity. A series of seven further analogues of NDUA and CPTA reveals the structural elements necessary for inhibition of lycopene cyclase. The effect of NDUA derivatives on photosynthesis has been studied in Chlamydomonas reinhardtii. Photosynthesis is highly sensitive, particularly towards the C14 and longer chain length analogues at nanomolar concentrations. It is shown that the breakdown of photosynthesis by NDUA is due to interference with the turnover of the D1 protein of the photosystem II reaction centre that requires the continous biosynthesis of the two reaction‐centre β‐carotene moieties in the reassembly phase. The D1 protein disappearance is most marked under strong light conditions. The depletion of photosystem II occurs before total pigment bleaching. This newly recognized mechanism in herbicidal activity is also the basis for the mode of action of other lycopene cyclase inhibitors as well as phytoene desaturase inhibitors.

© 2001 Society of Chemical Industry