bluuebunny/crossref_metadata_2025 huggingface dataset:
Failure properties of thermoplastic elastomers from polyethylene/nitrile rubber blends: Effect of blend ratio, dynamic vulcanization, and filler incorporation
Authors: George Josephine , Neelakantan N. R. , Varughese K. T. , Thomas Sabu
Published: February 2006

Thermoplastic elastomers from blends of high‐density polyethylene and acrylonitrile butadiene rubber were prepared by a melt‐blending technique. The blends were dynamically vulcanized using sulfur, peroxide, and mixed curing systems. The peroxide concentration was varied to obtain samples of varying degrees of crosslinking. The peroxide system showed better mechanical properties. The crosslink density determination by the equilibrium swelling method revealed that the enhancement in properties can be correlated to the extent of crosslinking. It is observed that the effect of dynamic vulcanization on the property improvement is much more pronounced in rubber‐rich blends. To study the effect of filler incorporation on mechanical properties, fillers such as carbon black, silica, silane‐treated silica, and cork‐filled samples were prepared. All filled systems, except cork filled, exhibited superior mechanical properties. Scanning electron micrographs of selected fractured surfaces were analyzed to study the failure mechanism of the different compositions. Various theoretical models were applied to correlate the observed mechanical behavior with that of theoretically predicted values. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2912–2929, 2006
Polymer/carbon nanotube composite emulsion prepared through ultrasonically assisted in situ emulsion polymerization
Authors: Xia Hesheng , Qiu Guihua , Wang Qi
Published: February 2006

In this study, ultrasonic irradiation and in situ emulsion polymerization were combined to prepare stable poly(methyl methacrylate‐co‐n‐butyl acrylate) (P(MMA‐BA))/carbon nanotubes (CNTs) composite emulsion, which solves the dispersion problem of CNTs in the latex. Two stages were adopted. In Stage I, ultrasonically initiated in situ emulsion polymerization was conducted to disperse CNTs and prepare the seed emulsion containing polymer coated CNTs. In Stage II, conventional in situ emulsion polymerization was conducted to further enhance the monomer conversion and solid content. The dispersion behavior of MWCNTs in aqueous solution under ultrasonic irradiation was investigated by spectrophotometry. The effects of CNTs content on the emulsion stability and mechanical properties of composite film were studied. The results suggest that in the composite emulsion the long CNTs with a diameter of 20–40 nm are separated and dispersed by the formed polymer latex nanoparticles with a size of 20–40 nm. The spherical polymer latex nanoparticles adhere to the wall of CNTs to form a structure like “grapes on the twig.” The smooth, uniform, and flexible polymer/CNTs composite films were prepared from the composite emulsion. The CNTs can be individually dispersed in P(MMA‐BA)/CNTs composite film. Tensile tests suggest that with the increase in the CNTs content, the Young's modulus and the yield strength of the film increase. Only at 1 wt % CNTs, the Young's modulus increases from 124 to 289 MPa, and the yield strength is improved about ∼14%. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3123–3130, 2006
Linear and networked blends and copolymers of polyimide
Authors: Xia Jiqiang , Wang Jinwei , Srinivasan M. P.
Published: February 2006

Preparation and characterization of blends and copolymers of a fluorinated polyimide with network constituents is reported. 4,4′‐Hexafluoroisopropylidene diphthalic anhydride and 4,4′‐diaminodiphenyl ether (6FDA–DDE) polyimide were used as the linear hosts and mellitic acid hexamethyl ester ‐ 4,4′‐diaminodiphenyl ether (MAHE–DDE) was employed as the network constituent for the blend and copolymer. Cast films of the polyimides were characterized by FTIR, XPS, DMA, and TGA. The multifunctional nature of MAHE facilitated crosslinking among the constituents. Both blends and copolymers showed significant improvement in the storage modulus and glass transition temperature relative to that observed for the 6FDA homopolymer. The occurrence of a single glass transition temperature for the blends suggests that they were at least partially miscible. Presence of low molecular weight species in the copolyimides, combined with steric hindrance to crosslinking, may have resulted in the existence of an optimum in the amount of the network components for improving the mechanical properties. Inclusion of network components is presented as a facile method for improving the desirable properties of polyimide. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3000–3008, 2006
A modified model and algorithm for flow‐enhanced crystallization—Application to fiber spinning
Authors: Shrikhande Prashant , Kohler William H. , McHugh Anthony J.
Published: February 2006

A modified version of the two‐phase flow‐induced crystallization model of Doufas et al. (J Non‐Newtonian Fluid Mech 2000, 92, 27) for melt spinning of polymeric fibers is presented to address three issues: (1) discontinuities generated due to the imposition of continuation conditions at the crystallization onset at Tmo; (2) excessive strength of the flow enhancement component coupling the total extra stress tensor invariant to the crystallization kinetics; and (3) Avrami isotherms used. The modified model provides seamless, two‐phase predictions for all‐state variables in the fiber‐spinning process and significantly reduces discontinuities. Moreover, a new component for the flow‐induced crystallization rate and Avrami crystallization rate isotherms increase the predictive capability of the model. Quantitative prediction of the velocity, stress, temperature, density (or crystallinity), and birefringence profiles are demonstrated for Nylon 66 and PET melts for a variety of process conditions, including predictions of quenched‐sample density profiles and the take‐up speed dependence of as‐spun fiber density. The new algorithm, assisted by the coupling model, provides a more efficient and robust convergence of steady‐state calculations and has been tested to predict spinning phenomena up to spin speeds of 9000 m/min. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3240–3254, 2006
Thermal and wide angle X‐ray analysis of chemically and radiation‐crosslinked low and high density polyethylenes
Authors: Khonakdar H. A. , Jafari S. H. , Taheri M. , Wagenknecht U. , Jehnichen D. , Häussler L.
Published: February 2006

Low and high density polyethylenes (PE) were crosslinked by two methods, namely, chemically by use of different amounts of tert‐butyl cumyl peroxide (BCUP) and by irradiation with different doses of electron beam. A comparison between the effects of these two types of crosslinking on crystalline structure, crystallinity, crystallization, and melting behaviors of PE was made by wide angle X‐ray diffraction and DSC techniques. Analysis of the DSC first heating cycle revealed that the chemically induced crosslinking, which took place at melt state, hindered the crystallization process and decreased the degree of crystallinity, as well as the size of crystals. Although the radiation‐induced crosslinking, which took place at solid state, had no significant influence on crystalline region, rather, it only increased the melting temperature to some extent. However, during DSC cooling cycle, the crystallization temperature showed a prominent decrease with increasing irradiation dose. The wide angle X‐ray scattering analysis supported these findings. The crystallinity and crystallite size of chemically crosslinked PE decreased with increasing peroxide content, whereas the irradiation‐crosslinked PE did not show any change in these parameters. As compared with HDPE, LDPE was more prone to crosslinking (more gel content) owing to the presence of tertiary carbon atoms and branching as well as owing to its being more amorphous in nature. HDPE, with its higher crystalline content, showed relatively less tendency toward crosslinking especially by way of irradiation at solid state. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3264–3271, 2006
Calorimetric analysis of the multiple melting behavior of poly(L‐lactic acid)
Authors: Di Lorenzo Maria Laura
Published: February 2006

This article contains a detailed calorimetric analysis of the multiple melting behavior of poly(L‐lactic acid) (PLLA) in dependence of crystallization conditions. PLLA crystals formed upon primary crystallization have a greater tendency to reorganize into more stable structures during the heating scan that leads to fusion. Depending on crystallization temperature, one or multiple melting endotherms and/or reorganization exotherms can be evidenced. This complex melting behavior arises from the fusion of a certain amount of the original crystals (already partially perfected during the heating scan), followed by recrystallization and final melting of more perfect crystals, partly grown during primary crystallization, and partly formed through the reorganization processes occurring during the heating scan. A detailed map of the melting behavior of PLLA is described in this contribution. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3145–3151, 2006
Determination of the α, β, and γ crystalline phases of poly(vinylidene fluoride) films prepared at different conditions
Authors: Gregorio Rinaldo
Published: February 2006

Samples containing the three crystalline phases of poly(vinylidene fluoride), α, β, and γ, have been obtained under distinct crystallization conditions. Samples containing exclusively unoriented β phase have been obtained by crystallization from dimethylformamide (DMF) solution at 60°C. Oriented β phase has been obtained by uniaxial drawing, at 80°C, of an originally α phase sample. Samples containing exclusively α phase have been obtained by melting and posterior cooling at room temperature. Samples containing both α and γ phases have been obtained by melt crystallization at 164 °C for 16 and 36 h. Presence of the crystalline phases in each sample were confirmed by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), wide‐angle X‐ray scattering (WAXD), polarized light optical microscopy (PLOM), and scanning electron microscopy (SEM). Infrared absorption bands identifying unequivocally the presence of β and γ phases in a sample are presented. It is shown that solution crystallization at T < 70°C always results in the β phase, regardless of the solvent used. Melt temperatures of the respective phases have also been determined. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3272–3279, 2006
Conductive polymer composites: Electrical, thermal, and rheological study of injected isotactic poly(propylene)/long stainless‐steel fibers for electromagnetic interferences shielding
Authors: Feller J. F. , Roth S. , Bourmaud A.
Published: February 2006

The influence of long stainless‐steel fibers (LSSF) on electrical, rheological, and calorimetric properties of conductive composites with poly(propylene) matrix was investigated as a function of filler content from ϕ = 0.15 to 3.6% v/v (1.3 to 23.5% w/w). The results show interesting features of the crystallization process: fibers act as nucleating agents and generate transcrystalline phases in quiescent conditions. LSSF also influences the flow properties and the dynamic rheological behavior, which is evidenced by evolution of G′ and G″ curves with filler content. Finally, SEM pictures of injected samples were used to determine the distribution and orientation of the fibers in the part thickness at different distances from the injection point. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3280–3287, 2006
Effect of fillers on the relaxation behavior of chlorobutyl vulcanizates
Authors: Sridhar V. , Chaudhary R. N. P. , Tripathy D. K.
Published: February 2006

The effect of addition of fillers (carbon black (CB), carbon silica dual phase filler (CSDPF), and nanoclays) on the relaxation behavior of chlorobutyl vulcanizates has been studied. The primary relaxation (α‐transition, the glass transition) was studied by dynamic mechanical analysis as a function of temperature (−60 to +100°C) and positron annihilation life time spectroscopy (−70 to +110°C). Irrespective of the filler and its loading, all the composites showed the glass transition temperature in the range of –29 to –33°C, which was explained on the basis of relaxation chain dynamics of polyisobutylene in the vicinity of fillers. The secondary relaxation (α* or β relaxation) was studied using dielectric relaxation spectra in the frequency range of 100–106 Hz. Nanoclays had a profound influence on the secondary relaxation, whereas CSDPF and CB had a marginal effect. The nonlinear strain dependent dynamical parameters were also evaluated at double strain amplitudes of 0.07–5%. The nonlinearity in tan δ and storage modulus has been explained on the concept of filler–polymer interactions and the interaggregate attraction (filler networking). The “percolation limit” of the fillers in the composites has been studied by DC conductivity measurements. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3161–3173, 2006
Synthesis, characterization, and dilute solution properties of pH‐responsive polyacyloylethylpiperazinium polymers
Authors: Mylswamy S. , Ramamurthi V. , Balasubramanian S.
Published: February 2006

Four different pH‐ and electrolyte‐responsive polymers were synthesized from ethyl piperazine with four different counter ions viz., chloride, bromide, sulfate, and nitrate. IR and NMR spectroscopic techniques confirmed the structure of monomers and polymers. Thermal properties of these polymers were investigated by TGA and DSC analysis. The dilute solution properties in pure water, in inorganic simple salt solutions, and pH‐responsive behavior of these polymers were studied by the measurement of viscosity by Ubbelohde viscometer. Flocculation behavior of these polymers was investigated by turbidity studies with bentonite suspension. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3174–3186, 2006
Biodegradation potential of some barrier‐coated boards in different soil environments
Authors: Nazhad M. M. , Sridach W. , Retulainen E. , Kuusipalo J. , Parkpian P.
Published: February 2006

Three pilot barrier‐coated boards that were recently produced at the Tampere University of Technology were tested for biodegradation potential using the soil‐burial test method. The tests were conducted in the field as well as in the laboratory. We found that the baseboards degraded regardless of differences in coating; however, the degradation rate was different. The laboratory conditions as well as the addition of inoculum accelerated the degradation process. The coated layer of the boards was isolated by laminating with black polyethylene; then their biodegradation rate was compared to the biodegradation rate of the control, boards coated with low‐density polyethylene. It was observed that paperboards coated with polyester‐based polymers were biodegradable but at different rates. The differences in the biodegradation rates of the boards were attributed to their coating formulations. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3193–3202, 2006
Oxidation of hydroquinone to p‐benzoquinone catalyzed by Cu(II) supported on chitosan flakes
Authors: Guibal Eric , Vincent Thierry , Touraud Evelyne , Colombo Simon , Ferguson Andrew
Published: February 2006

Copper (sorbed on chitosan flakes) was used as a catalyst for the oxidation of hydroquinone, with dioxygen (from air) and hydrogen peroxide as oxidizing agents. The supported catalyst was very efficient at oxidizing hydroquinone into p‐benzoquinone. With hydrogen peroxide at pH 5.8, drastic oxidizing conditions led to the formation of subproducts. With a short contact time, together with the use of a low hydrogen peroxide concentration and a small amount of the catalyst, the formation of subproducts could be minimized. The influence of the catalyst/substrate and hydrogen peroxide/substrate ratios was investigated to determine optimum experimental conditions for a high initial oxidation rate and a high production of p‐benzoquinone. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3034–3043, 2006
Polyaniline hollow microspheres constructed with their own self‐assembled nanofibers
Authors: Huang Kun , Meng Xiao‐Hong , Wan Meixiang
Published: February 2006

Polyaniline (PANI) hollow microspheres constructed with their own nanofibers were prepared by inversed microemulsion polymerization associated with a template‐free method in the presence of β‐naphthalene sulfonic acid (β‐NSA) as the dopant. The hollow microspheres were 4.0–6.0 μm in outer diameter and 150–250 nm in shell thickness; they consisted of the nanofibers (20–30 nm in diameter and 150–250 nm in length). We propose that the coordination effect of the reversed emulsion and the dopant or dopant/aniline micelle might have been a driving force in the formation of the special microstructures/nanostructures, where the reversed microemulsion acted as a soft template in the formation of the microspheres and where NSA or the aniline/NSA micelle was regarded as a soft template in the formation of the nanofibers. The molar ratio of water to the aniline/NSA salt and ultrasonic irradiation were critical in the control of the formation yield and the diameter of the uniform microspheres. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3050–3054, 2006
Ester acceleration mechanisms in phenol–formaldehyde resin adhesives
Authors: Lei Hong , Pizzi A. , Despres A. , Pasch H. , Du Guanben
Published: February 2006

An analysis of phenol–formaldehyde (PF) resins obtained by the addition of 0.5–5% glycerol triacetate (triacetin) as an accelerator during resin preparation showed the presence of intermediates involved in the acceleration mechanism. 13C‐NMR spectroscopy, matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) mass spectroscopy (MS), and gel permeation chromatography allowed us to identify some of the intermediates left over in the PF resin itself. The permanence in the resin of these labile intermediates, not easily observed otherwise, appeared to be due to the reaching of the diffusion‐controlled phase of the reaction. The mechanism involved appeared considerably more complex and different from any of the mechanisms presented previously. As a consequence of the evident complexity of the mechanism, it was not really possible to advance a complete mechanism of the reaction nor determine the real cause of the increase in the strength of the final network. The mechanism involved the phenate ion of the resin to apparently give a carbonyl or carboxyl group attached to the aromatic ring. Either directly or by subsequent rapid rearrangement after the initial attack, these CO groups were found on sites different from the ortho position. The appearance gathered from NMR shift calculation indicated preferential positioning or repositioning to the para site and, surprisingly, to the meta sites of the phenolic ring. The shifts of these CO groups correspond to those of an anhydride and to no other intermediate structures previously thought of. Anhydride‐like bridges were clearly shown by MALDI‐TOF MS to contribute to oligomer structures in which linkages between phenol rings were mixed methylene bridges and anhydride bridges. These structures appeared to be temporary, possibly due to the instability of the anhydride bridges; hence, they were in small proportions at any given moment of the reaction. MALDI‐TOF analysis clearly indicated that these structures were at some moment an integral part of the structure of the liquid resin and that they existed parallel to the methylene bridges pertaining to a normal PF resin structure. Previous spectra showed that similar but not identical intermediates were present also in organic and inorganic catalyzed PF resins. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100:3075–3093, 2006
Stability of acrylonitrile/methyl vinyl ketone copolymer solutions
Authors: Hou Chen , Ying Liang
Published: February 2006

Methyl vinyl ketone was successfully copolymerized with acrylonitrile for the first time. This was achieved with azobisisobutyronitrile as the initiator. The viscosity behavior of solutions of the acrylonitrile/methyl vinyl ketone copolymers was determined. The solution agreed with the character of Newtonian flow at the lower shearing rate. The addition of mechanical mixing obviously prevented an increase in the viscosity of the copolymer solutions. When dimethylformamide was used as an additive, the solution viscosity decreased monotonically. When H2O was used as an additive, the viscosity of the copolymer solutions decreased continuously with concentrations of H2O up to 4 wt % and then increased. The viscosity of the copolymer solutions decreased continuously with concentrations of KCl and NaCl up to 0.03 mol/L and then increased. Within the first 10 h, there was a great drop in the viscosity of the copolymer solutions containing sodium ethoxide and sodium hydroxide, and then the viscosity appeared to increase. The composition with 12 wt % acetic acid in dimethyl sulfoxide could be considered to be a Θ solvent for the acrylonitrile/methyl vinyl ketone copolymers. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3377–3381, 2006
Reconciling information‐seeking behavior with search user interfaces for the Web
Authors: Rose Daniel E.
Published: February 2006

User interfaces of Web search engines reflect attributes of the underlying tools used to create them, rather than what we know about how people look for information. In this article, the author examines several characteristics of user search behavior: the variety of information‐seeking goals, the cultural and situational context of search, and the iterative nature of the search task. An analysis of these characteristics suggests ways that interfaces can be redesigned to make searching more effective for users.
An unusual class of PITX2 mutations in Axenfeld‐Rieger syndrome
Authors: Saadi Irfan , Toro Rafael , Kuburas Adisa , Semina Elena , Murray Jeffrey C. , Russo Andrew F.
Published: February 2006

BACKGROUND

Mutations in the PITX2 homeobox gene are known to contribute to Axenfeld‐Rieger syndrome (ARS), an autosomal‐dominant developmental disorder. Although most mutations are in the homeodomain and result in a loss of function, there is a growing subset in the C‐terminal domain that has not yet been characterized. These mutations are of particular interest because the C‐terminus has both inhibitory and stimulatory activities.

METHODS

In this study we used a combination of in vitro DNA binding and transfection reporter assays to investigate the fundamental issue of whether C‐terminal mutations result in gain or loss of function at a cellular level.

RESULTS

We report a new frameshift mutation in the PITX2 allele that predicts a truncated protein lacking most of the C‐terminal domain (D122FS). This newly reported mutant and another ARS C‐terminal mutant (W133Stop) both have greater binding than wild‐type to the bicoid element. Of interest, the mutants yielded ∼5‐fold greater activation of the prolactin promoter in CHO cells, even though the truncated proteins were expressed at lower levels than the wild‐type protein. The truncated proteins also had greater than wild‐type activity in 2 other cell lines, including the LS8 oral epithelial line that expresses the endogenous Pitx2 gene.

CONCLUSIONS

The results indicate that the PITX2 C‐terminal domain has inhibitory activity and support the notion that ARS may also be caused by gain‐of‐function mutations. Birth Defects Research (Part A), 2006. © 2006 Wiley‐Liss, Inc.
HLXB9 homeobox gene and caudal regression syndrome
Authors: Merello Elisa , De Marco Patrizia , Mascelli Samantha , Raso Alessandro , Calevo Maria Grazia , Torre Michele , Cama Armando , Lerone Margherita , Martucciello Giuseppe , Capra Valeria
Published: February 2006

BACKGROUND

Caudal regression syndrome (CRS) is a congenital heterogeneous constellation of caudal anomalies that include varying degrees of agenesis of the spinal column, anorectal malformations (ARMs), genitourinary anomalies, and pulmonary hypoplasia. The combination of a particular form of hemisacrum, ARM, and presacral mass (teratoma, anterior meningocele, rectal duplication, or a combination thereof) constitutes Currarino syndrome (CS). Previous reports have shown HLXB9 to be a major causative gene for CS. The aim of our study was to reevaluate the involvement of the HLXB9 gene in a larger group of CRS cases.

METHODS

SSCP analysis was performed on a series of 48 CRS cases without CS. A case‐control approach was used to test whether an alteration of the length of the GCC triplets in exon 1 of the HLXB9 gene could contribute to CRS risk.

RESULTS

No pathological variants of the HLXB9 gene were identified by mutational analysis. We also found no evidence that the length of the GCC triplets had any effect on the CRS risk, even when the allelic frequencies were stratified according to the presence or absence of ARMs and the type of sacral agenesis.

CONCLUSIONS

We confirmed that the HLXB9 gene is not involved in the pathogenesis of CRS, and to date is known as a causative gene only for CS. Birth Defects Research (Part A), 2006. © 2006 Wiley‐Liss, Inc.
Distal 4p microdeletion in a case of Wolf‐Hirschhorn syndrome with congenital diaphragmatic hernia
Authors: Casaccia Germana , Mobili Luisa , Braguglia Annabella , Santoro Francesco , Bagolan Pietro
Published: February 2006

BACKGROUND

Wolf‐Hirschhorn syndrome (WHS) is a well‐known genetic condition characterized by typical facial anomalies, midline defects, skeletal anomalies, prenatal and postnatal growth retardation, hypotonia, mental retardation, and seizures. Affected patients with a microdeletion on distal 4p present a milder phenotype that lacks congenital malformations. WHS is rarely associated with congenital diaphragmatic hernia (CDH), and only 8 cases are reported in the literature. In almost all cases of CDH and WHS a large deletion of the short arm of chromosome 4 is present.

CASE

A microdeletion of 2.6 Mb on distal 4p associated with CDH and multiple congenital malformations (i.e., cleft palate) is reported for the first time.

CONCLUSIONS

Such a microdeletion should prompt a molecular study for WHS when in a fetus/newborn with CDH the association with cleft lip/palate and typical facial appearance (flat facial profile, hypertelorism) is found. Birth Defects Research (Part A), 2006. © 2006 Wiley‐Liss, Inc.
Rational design and synthesis of a double‐stranded DNA–binder library
Authors: S̆ebestík Jaroslav , Hlavác̆ek Jan , Stibor Ivan
Published: February 2006

Described is a computer‐assisted rational design of a DNA–bis‐intercalator peptide library. The peptide library of 250 members was prepared and the most powerful binder identified. A value of the binding constant is almost two orders of magnitude higher than that of starting building block‐9‐aminoacridine. The binder affinity found toward calf thymus DNA is 30‐fold of that of human prion peptide 106–126. © 2006 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 84: 400–407, 2006

This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Ethanol is a better inducer of DNA guanine tetraplexes than potassium cations
Authors: Vorlíčková Michaela , Bednářová Klára , Kypr Jaroslav
Published: February 2006

Guanine tetraplexes are a biologically relevant alternative of the Watson and Crick duplex of DNA. It is thought that potassium or other cations present in the cavity between consecutive guanine tetrads are an integral part of the tetraplexes. Here we show using CD spectroscopy that ethanol induces the guanine tetraplexes like or even better than potassium cations. We present examples of ethanol stabilizing guanine tetraplexes even in cases when potassium cations fail to do so. Hence, besides the A‐form or Z‐form, ethanol stabilizes another conformation of DNA, i.e., the guanine tetraplexes. We discuss the mechanism of the stabilization. Use of ethanol will permit studies of guanine tetraplexes that cannot be induced by potassium cations or other tetraplex‐promoting agents. This work demonstrates that a still broader spectrum of nucleotide sequences can fold into guanine tetraplexes than has previously been thought. Aqueous ethanol may better simulate conditions existing in vivo than the aqueous solutions. © 2006 Wiley Periodicals, Inc. Biopolymers 82: 253–260, 2006

This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
UV‐resonance Raman spectroscopic study of human plasma of healthy donors and patients with thrombotic microangiopathy
Authors: Harz M. , Claus R. A. , Bockmeyer C. L. , Baum M. , Rösch P. , Kentouche K. , Deigner H.‐P. , Popp J.
Published: February 2006

Various diseases shift the composition of human plasma; hence, the relative quantification of plasma constituents offers the opportunity to use the dynamic and complex composition of plasma to gain information on novel diagnostic and prognostic factors. Since plasma contains, besides water, mostly proteins, UV‐resonance Raman spectroscopy (UVRR) seems to be a suitable method for investigating plasma. With this method the signals of aromatic amino acids and proteins are selectively enhanced. In this study an UV‐resonance Raman approach was used for the investigation of human plasma of healthy volunteers and patients with thrombotic microangiopathy. For comparison, selected plasma components were analyzed for a more detailed characterization of cryoprecipitates from human plasma. © 2006 Wiley Periodicals, Inc. Biopolymers 82:317–324, 2006

This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Theoretical prediction of the basic helix types in α,β‐hybrid peptides
Authors: Baldauf Carsten , Günther Robert , Hofmann Hans‐Jörg
Published: February 2006

This study provides a complete overview on all possible helical‐ folding patterns, their stabilities, and their detailed molecular structure in the novel foldamer class of α,β‐hybrid peptides on the basis of ab initio molecular orbital (MO) theory. The results indicate a considerable intrinsic potential of backbone folding. As found for other peptide foldamers, representatives of mixed or β‐helices are most stable in more apolar media, whereas polar environments favor the helices with the hydrogen bonds pointing in only one direction. The theoretical results confirm the hydrogen‐bonding patterns found in the first experimental studies on these hybrid peptides. Selecting special backbone substitution patterns, the secondary structure potential of the α,β‐hybrid peptides could be of great importance for a rational peptide and protein design. © 2006 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 84: 408–413, 2006

This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Cellular uptake of phosphorothioate oligonucleotide facilitated by cationic porphyrin: A microfluorescence study
Authors: Kočišová E. , Praus P. , Mojzeš P. , Sureau F. , Štěpánek J. , Seksek O. , Turpin P. Y.
Published: February 2006

Cationic 5,10,15,20‐tetrakis (1‐methyl‐4‐pyridyl) porphyrin was tested as a delivery agent for oligonucleotides. By using fluorescence microimaging, it has been shown that complexation of the porphyrin to the phosphorothioate analog of dT15 labeled by rhodamine enabled its nonendocytic penetration into the cell and regular distribution in the cytoplasm and preferentially into the nucleus. Time‐resolved microfluorescence spectroscopy revealed that the oligonucleotide integrity was kept. A small fraction of the porphyrin molecules seems to undergo change of the binding mode after internalization, probably due to duplex formation between the oligonucleotide and its cellular target sequences, or due to dissociation of the porphyrin from the oligonucleotide and subsequent interactions in the cellular environment © 2006 Wiley Periodicals, Inc. Biopolymers 82:325–328, 2006

This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Enantioconvergent production of (R)‐1‐phenyl‐1,2‐ethanediol from styrene oxide by combining the Solanum tuberosum and an evolved Agrobacterium radiobacter AD1 epoxide hydrolases
Authors: Cao Li , Lee Jintae , Chen Wilfred , Wood Thomas K.
Published: February 2006

Soluble epoxide hydrolase (EH) from the potato Solanum tuberosum and an evolved EH of the bacterium Agrobacterium radiobacter AD1, EchA‐I219F, were purified for the enantioconvergent hydrolysis of racemic styrene oxide into the single product (R)‐1‐phenyl‐1,2‐ethanediol, which is an important intermediate for pharmaceuticals. EchA‐I219F has enhanced enantioselectivity (enantiomeric ratio of 91 based on products) for converting (R)‐styrene oxide to (R)‐1‐phenyl‐1,2‐ethanediol (2.0 ± 0.2 µmol/min/mg), and the potato EH converts (S)‐styrene oxide primarily to the same enantiomer, (R)‐1‐phenyl‐1,2‐ethanediol (22 ± 1 µmol/min/mg), with an enantiomeric ratio of 40 ± 17 (based on substrates). By mixing these two purified enzymes, inexpensive racemic styrene oxide (5 mM) was converted at 100% yield to 98% enantiomeric excess (R)‐1‐phenyl‐1,2‐ethanediol at 4.7 ± 0.7 µmol/min/mg. Hence, at least 99% of substrate is converted into a single stereospecific product at a rapid rate. © 2006 Wiley Periodicals, Inc.
Free peritoneal tumour cells are an independent prognostic factor in curatively resected stage IB gastric carcinoma
Authors: Rosenberg R , Nekarda H , Bauer P , Schenck U , Hoefler H , Siewert J R
Published: February 2006

Background

Several studies have shown that the cytological detection of free peritoneal tumour cells (FPTCs) in patients with gastric cancer indicates the presence of metastatic disease. The immunocytochemical detection of FPTCs, especially in early-stage tumours, has not been examined comprehensively.

Method

Peritoneal lavage was performed in 351 patients before curative resection of a gastric carcinoma between 1987 and 2001, and an adequate sample was obtained from 346 patients. FPTCs were detected immunocytochemically using Ber-EP4 antibody. Median follow-up time was 70 months.

Results

FPTCs were detected in the lavage fluid of 74 patients (21·4 per cent) and correlated with increasing pathological tumour depth (pT) and lymph node (pN) status (P < 0·001). The 5-year overall survival of patients with FPTCs was significantly worse than that of patients without FPTCs (35 versus 71·9 per cent; P < 0·001). FPTCs were present in 14 (8·5 per cent) of 164 patients with stage IA or IB tumours. Although the detection of FPTCs had no prognostic significance for stage IA tumours, the presence of FPTCs in those with stage IB tumours was associated with a worse prognosis (P < 0·001). Multivariate analysis identified the presence of FPTCs as an independent prognostic factor in the whole cohort and in the stage IB subgroup.

Conclusion

Detection of FPTCs is associated with poor prognosis even in patients with early-stage gastric cancer and should be used for risk-group stratification.
Fibrinolytic risk factor clustering and insulin resistance in healthy male relatives of men with intermittent claudication
Authors: Parry D J , Grant P J , Scott D J A
Published: February 2006

Background

Raised fibrinolytic factors predict cardiovascular risk in healthy subjects. The aim of this study was to measure fibrinolytic factors and insulin resistance in healthy male first-degree relatives of men with intermittent claudication younger than 65 years.

Methods

The study compared 165 healthy first-degree relatives with 165 age-, sex- and race-matched control subjects free from a personal or family history of premature cardiovascular disease. Primary outcome measures were plasminogen activator inhibitor 1 (PAI-1), tissue plasminogen activator (tPA) and D-dimer levels. Insulin resistance was estimated by Homeostasis Model Assessment. Clinical and biochemical risk factors were measured and subjects genotyped for the PAI-1 4G/5G polymorphism.

Results

First-degree relatives had significantly higher mean PAI-1 (10·23 versus 7·85 ng/ml; P = 0·024), tPA (9·98 versus 8·29 ng/ml; P < 0·001) and D-dimer levels (56·6 versus 46·1 ng/ml; P = 0·004). They also had significantly higher insulin resistance (1·85 versus 1·53; P < 0·001) and clustered multiple atherogenic risk factors. On multivariate analysis the association between both tPA and D-dimer levels and relative status was independent of other variables.

Conclusion

Raised levels of PAI-1, tPA, D-dimer and estimated insulin resistance were present in the healthy male first-degree relatives of men with intermittent claudication. These data support the hypothesis of fibrinolytic risk factor clustering in this high-risk population.
The management of insulinoma
Authors: Tucker O N , Crotty P L , Conlon K C
Published: February 2006

Background

Insulinomas are rare tumours. Their clinical presentation, localization techniques and operative management were reviewed.

Methods

An electronic search of the Medline, Embase and Cochrane databases was undertaken for articles published between January 1966 and June 2005 on the history, presentation, clinical evaluation, use of imaging techniques for tumour localization and operative management of insulinoma.

Results and conclusion

Most insulinomas are intrapancreatic, benign and solitary. Biochemical diagnosis is obtained during a supervised 72-h fast. Non-invasive preoperative imaging techniques to localize lesions continue to evolve. Intraoperative ultrasonography can be combined with other preoperative imaging modalities to improve tumour detection. Surgical resection is the treatment of choice. In the absence of preoperative localization and intraoperative detection of an insulinoma, blind pancreatic resection is not recommended.
An interactive three‐dimensional virtual body structures system for anatomical training over the internet
Authors: Temkin Bharti , Acosta Eric , Malvankar Ameya , Vaidyanath Sreeram
Published: February 2006

The Visible Human digital datasets make it possible to develop computer‐based anatomical training systems that use virtual anatomical models (virtual body structures—VBS). Medical schools are combining these virtual training systems and classical anatomy teaching methods that use labeled images and cadaver dissection. In this paper we present a customizable web‐based three‐dimensional anatomy training system, W3D‐VBS. W3D‐VBS uses National Library of Medicine's (NLM) Visible Human Male datasets to interactively locate, explore, select, extract, highlight, label, and visualize, realistic 2D (using axial, coronal, and sagittal views) and 3D virtual structures. A real‐time self‐guided virtual tour of the entire body is designed to provide detailed anatomical information about structures, substructures, and proximal structures. The system thus facilitates learning of visuospatial relationships at a level of detail that may not be possible by any other means. The use of volumetric structures allows for repeated real‐time virtual dissections, from any angle, at the convenience of the user. Volumetric (3D) virtual dissections are performed by adding, removing, highlighting, and labeling individual structures (and/or entire anatomical systems). The resultant virtual explorations (consisting of anatomical 2D/3D illustrations and animations), with user selected highlighting colors and label positions, can be saved and used for generating lesson plans and evaluation systems. Tracking users' progress using the evaluation system helps customize the curriculum, making W3D‐VBS a powerful learning tool. Our plan is to incorporate other Visible Human segmented datasets, especially datasets with higher resolutions, that make it possible to include finer anatomical structures such as nerves and small vessels. Clin. Anat. 267–274, 2006. © 2006 Wiley‐Liss, Inc.
Chinese visible human project
Authors: Zhang Shao‐Xiang , Heng Pheng‐Ann , Liu Zheng‐Jin
Published: February 2006

Research on the digital visible human is of great significance and has considerable application value. The US visible human project created the first digital image dataset of a complete human (one male and one female) in 1995. To promote worldwide application‐oriented visible human research, additional visible human datasets, representative of different populations of the world, are needed. The Chinese visible human (CVH) male (created in October 2002) and female (created in February 2003) Project achieved greater integrity of images, better blood vessel identification, and were free of organic disease. The most noteworthy technical advance of the Chinese visible human project (CVHP) was the construction of a low temperature laboratory, which prevented loss of small structures (including teeth, nasal conchae, and articular cartilage) from the milling surface. Thus, better integrity of images was achieved. To date, we have acquired five CVH datasets and volume rendered them for visualization on a PC. 3D reconstruction of some organs and structures has been completed and work to segment a complete dataset is under way. Although there is still a long way to go to make the visible human meet the application‐oriented needs in various fields, progress is being made toward acquiring new datasets, performing segmentation, and setting up a platform of computer‐assisted medicine. Here, we review the history and highlights of the CVHP and foresee its future development as well. Clin. Anat. 19:204–215, 2006. © 2006 Wiley‐Liss, Inc.
The psoas quartus muscle
Authors: Tubbs R. Shane , Oakes W. Jerry , Salter E. George
Published: February 2006

We report an unusual finding in an adult male cadaver. During the routine dissection of the posterior abdominal wall as part of an anatomy course at our institution, an anomalous muscle was noted. This muscle originated from the transverse process of the left L3 vertebrae and the medial aspect of the quadratus lumborum. We believe this muscle to represent a variety of the psoas quartus that, to our knowledge, has only been described once before in the extant medical literature. The presence of a psoas quartus muscle may contribute to femoral nerve compression. The clinician may wish to consider this rare muscular anomaly in patients with symptoms of femoral nerve compression in which no other clear etiology is found. Furthermore, clinicians who image the posterior abdominal wall should be aware of this potential anomaly when interpreting the anatomy of this region. Clin. Anat. 19:678–680, 2006. © 2006 Wiley‐Liss, Inc.
Photorealistic virtual anatomy based on Chinese Visible Human data
Authors: Heng P.A. , Zhang S.X. , Xie Y.M. , Wong T.T. , Chui Y.P. , Cheng C.Y.
Published: February 2006

Virtual reality based learning of human anatomy is feasible when a database of 3D organ models is available for the learner to explore, visualize, and dissect in virtual space interactively. In this article, we present our latest work on photorealistic virtual anatomy applications based on the Chinese Visible Human (CVH) data. We have focused on the development of state‐of‐the‐art virtual environments that feature interactive photo‐realistic visualization and dissection of virtual anatomical models constructed from ultra‐high resolution CVH datasets. We also outline our latest progress in applying these highly accurate virtual and functional organ models to generate realistic look and feel to advanced surgical simulators. Clin Anat. 19:232–239, 2006. © 2006 Wiley‐Liss, Inc.
Nonribosomal Peptide Synthesis in Schizosaccharomyces pombe and the Architectures of Ferrichrome‐Type Siderophore Synthetases in Fungi
Authors: Schwecke Torsten , Göttling Kirsten , Durek Pawel , Dueñas Ines , Käufer Norbert F. , Zock‐Emmenthal Susanne , Staub Eike , Neuhof Torsten , Dieckmann Ralf , von Döhren Hans
Published: February 2006

A nonribosomal peptide synthetase (NRPS) in Schizosaccharomyces pombe, which possesses an unusual structure incorporating three adenylation domains, six thiolation domains and six condensation domains, has been shown to produce the cyclohexapeptide siderophore ferrichrome. One of the adenylation domains is truncated and contains a distorted key motif. Substrate‐binding specificities of the remaining two domains were assigned by molecular modelling to glycine and to N‐acetyl‐N‐hydroxy‐L‐ornithine. Hexapeptide siderophore synthetase genes of Magnaporthe grisea and Fusarium graminearum were both identified and analyzed with respect to substrate‐binding sites, and the predicted product ferricrocin was identified in each. A comparative analysis of these synthetase systems, including those of the basidiomycete Ustilago maydis, the homobasidiomycete Omphalotus olearius and the ascomycetes Aspergillus nidulans, Aspergillus fumigatus, Fusarium graminearum, Cochliobolus heterostrophus, Neurospora crassa and Aureobasidium pullulans, revealed divergent domain compositions with respect to their number and positioning, although all produce similar products by iterative processes. A phylogenetic analysis of both NRPSs and associated L‐N5‐ornithine monooxygenases revealed that ferrichrome‐type siderophore biosynthesis has coevolved in fungi with varying in trans interactions of NRPS domains.
On‐Bead Chemical Synthesis and Display of Phosphopeptides for Affinity Pull‐Down Proteomics
Authors: Brandt Malene , Madsen Jens C. , Bunkenborg Jakob , Jensen Ole N. , Gammeltoft Steen , Jensen Knud J.
Published: February 2006

We describe a new method for phosphopeptide proteomics based on the solid‐phase synthesis of phosphopeptides on beads suitable for affinity pull‐down experiments. Peptide sequences containing the Bad Ser112 and Ser136 phosphorylation motifs were used as bait in affinity pull‐down experiments to determine their ability to bind 14‐3‐3 proteins. Support‐bound peptides were assembled directly on the solid support (PEGA) by standard solid‐phase synthesis through a BAL‐type handle. The peptides were varied in length and sequence. This synthetic strategy also allowed introduction of a soft electrophile (aldehyde) at the C terminus for potential activity‐based proteomics. The synthetic support‐bound Bad phosphopeptides were able to pull down 14‐3‐3ζ. Furthermore, Bad phosphopeptides bound endogenous 14‐3‐3 proteins, and all seven members of the 14‐3‐3 family were identified by mass spectrometry. In control experiments, none of the unphosphorylated Bad peptides bound transfected 14‐3‐3ζ or endogenous 14‐3‐3. We conclude that the combined synthesis and display of phosphopeptides on‐bead is a fast and efficient method for affinity pull‐down proteomics.