bluuebunny/crossref_metadata_2025_split huggingface dataset:
Physical properties of aliphatic polycarbonates made from CO2 and epoxides
Authors: Thorat Sudhir D. , Phillips Paul J. , Semenov Viktor , Gakh Andre 
Published: May 2003

AbstractA homologous series of aliphatic polycarbonates with different side‐chain lengths was synthesized by ring‐opening polymerization of terminal epoxides with CO2 using zinc adipionate as catalyst [patented process of Empower Materials (formerly PAC Polymers Inc.)]. Additionally, a polycarbonate was made having a cyclohexane unit in its backbone, together with a terpolymer having both cyclohexane and propylene units. After characterization of thermal properties the aliphatic polycarbonates were found to be completely amorphous. Polycarbonates derived from long‐chain epoxides showed a glass‐transition temperature (Tg) below room temperature, whereas polycarbonates derived from cyclohexene oxide showed a Tg of 105°C, the highest yet reported for this class of polymers. The initial decomposition temperature of the polymers in air and nitrogen atmospheres was found to be less than 300°C. The mechanical properties and the dynamic mechanical relaxation behavior of the polymers were also reported. The effect of the chemical structure on the physical properties of aliphatic polycarbonates was discussed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1163–1176, 2003
Curing process of powdered phenol–formaldehyde resol resins and the role of water in the curing systems
Authors: He Guangbo , Riedl Bernard , Aït‐Kadi Abdellatif 
Published: May 2003

AbstractThe curing behavior of two kinds of commercial powdered resol phenolic resins was studied by differential scanning calorimetry. Liquid‐state 13C‐NMR spectroscopy was used to aid in understanding the curing behavior by detecting the structure of powdered resins. The reaction mechanism was interpreted with the dependency of activation energy on the degree of conversion. The results indicate that there are differences in the curing mechanism between core and face phenolic resins. The curing process of core resin was faster than that of face resin at the same reaction temperature. The water added in the curing system played an important role of plasticizer or diluent according to different curing stages and water content. In the initial curing stage, water mainly diluted the system and retarded the curing reactions. However, at the higher degrees of conversion, water played the role of plasticizer to decrease the effect of diffusion on the curing reactions to make the curing reactions more complete. The excess water added in the curing system played the role of diluent at almost all stages during the curing process. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1371–1378, 2003
Structure and gas separation properties of composite films based on polyaniline
Authors: Orlov A. V. , Kiseleva S. G. , Karpacheva G. P. , Teplyakov V. V. , Syrtsova D. A. , Starannikova L. E. , Lebedeva T. L. 
Published: May 2003

AbstractComposite films based on the polyvinyltrimethylsilane (PVTMS) with polyaniline (PANI) coating were obtained by borderline polymerization of aniline. The obtained coating was shown to differ from the polymer forming in the reaction mixture bulk both in chemical structure and morphology. Ratio and concentration of the reagents, mixing rate, reaction time, and condition of support surface were among the investigated factors affecting the growth and quality of PANI coating. The gas separation characteristics of composite membranes, as affected by the process conditions and the type of PANI, were investigated. It is shown that the proposed method provides a means for obtaining composite membranes that combine high selectivity, especially in O2/N2, He/CH4, and CO2/CH4 separation, with permeability higher than that of known composite materials. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1379–1384, 2003
Properties of impregnation resin added to multifunctional epoxy at cryogenic temperature
Authors: Chen Qiang , Gao Bingjun , Chen Jinglin 
Published: May 2003

AbstractA multifunctional epoxy tetraglycidyl dibenzmethyldiamine and triglycidyl benzylamine were blended, respectively, into impregnation resin, which mainly consists of diglycidyl ether of bisphenol A (DGEBA) and acid anhydride hardener. This resin is expected to impregnate HT‐7U superconducting Tokamak toroidal field coils and improve the fracture toughness of DGEBA–acid anhydride resin at cryogenic temperature. However, the experimental results reveal that resin lap shear strengths decrease remarkably both at ambient and liquid nitrogen temperatures. After blending multifunctional epoxy for several hours, its viscosity increased quickly at room temperature. The usable potting life is too short to impregnate large coils such as those used in fusion reaction. By FTIR the possible reason was investigated. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1385–1389, 2003
Imprinting evolution and the price of silence
Authors: Murphy Susan K. , Jirtle Randy L. 
Published: May 2003

AbstractIn contrast to the biallelic expression of most genes, expression of genes subject to genomic imprinting is monoallelic and based on the sex of the transmitting parent. Possession of only a single active allele can lead to deleterious health consequences in humans. Aberrant expression of imprinted genes, through either genetic or epigenetic alterations, can result in developmental failures, neurodevelopmental and neurobehavioral disorders and cancer. The evolutionary emergence of imprinting occurred in a common ancestor to viviparous mammals after divergence from the egg‐laying monotremes. Current evidence indicates that imprinting regulation in metatherian mammals differs from that in eutherian mammals. This suggests that imprinting mechanisms are evolving from those that were established 150 million years ago. Therefore, comparing genomic sequence of imprinted domains from marsupials and eutherians with those of orthologous regions in monotremes offers a potentially powerful bioinformatics approach for identifying novel imprinted genes and their regulatory elements. Such comparative studies will also further our understanding of the molecular evolution and phylogenetic distribution of imprinted genes. BioEssays 25:577–588, 2003. © 2003 Wiley Periodicals, Inc.
The architecture of polarized cell growth: The unique status of elongating plant cells
Authors: Baluška František , Wojtaszek Przemysław , Volkmann Dieter , Barlow Peter 
Published: May 2003

AbstractPolarity is an inherent feature of almost all prokaryotic and eukaryotic cells. In most eukaryotic cells, growth polarity is due to the assembly of actin‐based growing domains at particular locations on the cell periphery. A contrasting scenario is that growth polarity results from the establishment of non‐growing domains, which are actively maintained at opposite end‐poles of the cell. This latter mode of growth is common in rod‐shaped bacteria and, surprisingly, also in the majority of plant cells, which elongate along the apical–basal axes of plant organs. The available data indicate that the non‐growing end‐pole domains of plant cells are sites of intense endocytosis and recycling. These actin‐enriched end‐poles serve also as signaling platforms, allowing bidirectional exchange of diverse signals along the supracellular domains of longitudinal cell files. It is proposed that these actively remodeled end‐poles of elongating plant cells remotely resemble neuronal synapses. BioEssays 25:569–576, 2003. © 2003 Wiley Periodicals, Inc.
Fanconi anaemia proteins: Major roles in cell protection against oxidative damage
Authors: Pagano Giovanni , Youssoufian Hagop 
Published: May 2003

AbstractFanconi anaemia (FA) is a cancer‐prone genetic disorder that is characterised by cytogenetic instability and redox abnormalities. Although rare subtypes of FA (B, D1 and D2) have been implicated in DNA repair through links with BRCA1 and BRCA2, such a role has yet to be demonstrated for gene products of the common subtypes. Instead, these products have been strongly implicated in xenobiotic metabolism and redox homeostasis through interactions of FANCC with cytochrome P‐450 reductase and with glutathione S‐transferase, and of FANCG with cytochrome P‐450 2E1, as well as redox‐dependent signalling through an interaction between FANCA and Akt kinase. We hypothesise that FA proteins act directly (via FANCC and FANCG) and indirectly (via FANCA, BRCA2 and FANCD2) with the machinery of cellular defence to modulate oxidative stress. The latter interactions may co‐ordinate the link between the response to DNA damage and oxidative stress parameters (3, 6–12). BioEssays 25:589–595, 2003. © 2003 Wiley Periodicals, Inc.
Species as family resemblance concepts: The (dis‐)solution of the species problem?
Authors: Pigliucci Massimo 
Published: May 2003

AbstractThe so‐called “species problem” has plagued evolutionary biology since before Darwin's publication of the aptly titledOrigin of Species. Many biologists think the problem is just a matter of semantics; others complain that it will not be solved until we have more empirical data. Yet, we don't seem to be able to escape discussing it and teaching seminars about it. In this paper, I briefly examine the main themes of the biological and philosophical literatures on the species problem, focusing on identifying common threads as well as relevant differences. I then argue two fundamental points. First, the species problem is not primarily an empirical one, but it is rather fraught with philosophical questions that require—but cannot be settled by—empirical evidence. Second, the (dis‐)solution lies in explicitly adopting Wittgenstein's idea of “family resemblance” or cluster concepts, and to consider species as an example of such concepts. This solution has several attractive features, including bringing together apparently diverging themes of discussion among biologists and philosophers. The current proposal is conceptually independent (though not incompatible) with the pluralist approach to the species problem advocated by Mishler, Donoghue, Kitcher and Dupré, which implies that distinct aspects of the species question need to be emphasized depending on the goals of the researcher. From the biological literature, the concept of species that most closely matches the philosophical discussion presented here is Templeton's cohesion idea. BioEssays 25:596–602, 2003. © 2003 Wiley Periodicals, Inc.
Biological activities of the shrub Salsola tuberculatiformis Botsch.: Contraceptive or stress alleviator?
Authors: Swart Pieter , Swart Amanda C. , Louw Ann , van der Merwe Kirsten J. 
Published: May 2003

AbstractPlants belonging to the genus Salsola (Family: Chenopodiaceae) are common in the arid and semiarid regions of our planet with no less than 69 different Salsola species found in Namibia and the Republic of South Africa. This genus is used as a traditional medicine and aqueous extracts of Salsola have been used by Bushmen women as an oral contraceptive. Ingestion of the Namibian shrub Salsola tuberculatiformis Botsch. by pregnant Karakul sheep leads to prolonged gestation and fetal post‐maturity and, as a result, the pelts of the new‐born karakul lambs are worthless. This initiated an investigation into the active agents in the plant, using the terminal enzyme in adrenal corticosteroidogenesis, cytochrome P450‐dependent 11β‐hydroxylase (P450c11), as a bioassay. Although the active fraction, S2, was extremely labile, partial structure determination suggested the presence of synephrine and a highly reactive aziridine. Therefore a more stable analogue, 2‐(4‐acetoxyphenyl)2‐chloro‐N‐methylethylammonium‐chloride (compound A), was synthesised, which, like the active plant extracts, inhibited adrenal steroidogenesis and acted as a contraceptive. In addition, compound A was stabilised by interaction with steroid‐binding globulins in plasma thus enhancing biological activity in vivo. These findings provided explanations for the complex biological effects of the shrub as well as a new insight into the mode of action of chemically labile plant products in vivo. BioEssays 25:612–619, 2003. © 2003 Wiley Periodicals, Inc.
Dlg, Scribble and Lgl in cell polarity, cell proliferation and cancer
Authors: Humbert Patrick , Russell Sarah , Richardson Helena 
Published: May 2003

AbstractDlg (Discs large), Scrib (Scribble) and Lgl (Lethal giant larvae) are evolutionarily conserved components of a common genetic pathway that link the seemingly disparate functions of cell polarity and cell proliferation in epithelial cells. dlg, scrib and lgl have been identified as tumour suppressor genes in Drosophila, mutations of which cause similar phenotypes, involving disruption of cell polarity and neoplastic overgrowth of tissues. The molecular mechanisms by which Dlg, Scrib and Lgl proteins regulate cell proliferation are not clear, but there is some evidence that epithelial polarisation is required for this regulation. Dlg, Scrib and Lgl are highly conserved between human and Drosophila, and we discuss evidence that these proteins also play a role in cancer progression in humans. BioEssays 25:542–553, 2003. © 2003 Wiley Periodicals, Inc.
The thioredoxin‐like fold: Hidden domains in protein disulfide isomerases and other chaperone proteins
Authors: Clissold Patricia M. , Bicknell Roy 
Published: May 2003

AbstractAlthough protein disulphide isomerase (PDI) has been known for nearly 40 years, several new PDIs have recently been described that reveal a remarkable diversity in both structure and function. This article reviews our current knowledge of the PDI family members and identifies four novel PDIs in the human genome. These include human transmembrane proteins that have C. elegans or Drosophila orthologues for which a developmental role has been proven. Their role in development, together with other functional roles for PDIs such as conferring resistance to apoptosis under hypoxia and a potential role in the oxygen‐sensing apparatus are discussed. Supplementary material for this article can be found on the BioEssays website (http://www.interscience.wiley.com/jpages/0265‐9247/suppmat/2003/25/v25.603.html). BioEssays 25:603–611, 2003. © 2003 Wiley Periodicals, Inc.
About face: Signals and genes controlling jaw patterning and identity in vertebrates
Authors: Richman Joy M. , Lee Sang‐Hwy 
Published: May 2003

AbstractThe embryonic vertebrate face is composed of similarly sized buds of neural crest‐derived mesenchyme encased in epithelium. These buds or facial prominences grow and fuse together to give the postnatal morphology characteristic of each species. Here we review the role of neural crest cells and foregut endoderm in differentiating facial features. We relate the developing facial prominences to the skeletal structure of the face and review the signals and genes that have been shown to play an important role in facial morphogenesis. We also examine two experiments one at the genetic level and one at the signal level in which transformation of facial prominences and subsequent change of jaw identity was induced. We propose that signals such as retinoids and BMPs and downstream transcription factors such as Distal‐less related genes specify jaw identity. BioEssays 25:554–568, 2003. © 2003 Wiley Periodicals, Inc.
Mitochondrial biogenesis: Which part of “NO” do we understand?
Authors: Leary Scot C. , Shoubridge Eric. A. 
Published: May 2003

AbstractA recent paper by Nisoli et al.1 provides the first evidence that elevated levels of nitric oxide (NO) stimulate mitochondrial biogenesis in a number of cell lines via a soluble guanylate‐cyclase‐dependent signaling pathway that activates PGC1α (peroxisome proliferator‐activated receptor γ coactivator‐1α), a master regulator of mitochondrial content. These results raise intriguing possibilities for a role of NO in modulating mitochondrial content in response to physiological stimuli such as exercise or cold exposure. However, whether this signaling cascade represents a widespread mechanism by which mammalian tissues regulate mitochondrial content, and how it might integrate with other pathways that control PGC1α expression, remain unclear. BioEssays 25:538–541, 2003. © 2003 Wiley Periodicals, Inc.
The Ciona intestinalis genome: When the constraints are off
Authors: Holland Linda Z. , Gibson‐Brown Jeremy J. 
Published: May 2003

AbstractThe recent genome sequencing of a non‐vertebrate deuterostome, the ascidian tunicate Ciona intestinalis, makes a substantial contribution to the fields of evolutionary and developmental biology.1 Tunicates have some of the smallest bilaterian genomes, embryos with relatively few cells, fixed lineages and early determination of cell fates. Initial analyses of the C. intestinalis genome indicate that it has been evolving rapidly. Comparisons with other bilaterians show that C. intestinalis has lost a number of genes, and that many genes linked together in most other bilaterians have become uncoupled. In addition, a number of independent, lineage‐specific gene duplications have been detected. These new results, although interesting in themselves, will take on a deeper significance once the genomes of additional invertebrate deuterostomes (e.g. echinoderms, hemichordates and amphioxus) have been sequenced. With such a broadened database, comparative genomics can begin to ask pointed questions about the relationship between the evolution of genomes and the evolution of body plans. BioEssays 25:529–532, 2003. © 2003 Wiley Periodicals, Inc.
An improved model for analyzing the small angle x‐ray scattering of starch granules
Authors: Daniels D. R. , Donald A. M. 
Published: May 2003

AbstractThe structure of starch was studied using small‐angle x‐ray scattering (SAXS). The scattering data was modeled by considering a finite stack of alternating lamellae that are allowed to fluctuate both along the layer repeat direction and along the transverse layer direction. Analysis in this way of the SAXS data from starch allowed fresh insights into the native structure of several starch species, particularly potato starch. The novel model presented in this work was able to capture the experimentally observed SAXS patterns much better than previous models, which did not incorporate transverse layer fluctuations. © 2003 Wiley Periodicals, Inc. Biopolymers 69: 165–175, 2003
Structural characterization and artificial fiber formation of Bombyx mori silk fibroin in hexafluoro‐iso‐propanol solvent system
Authors: Zhao Chenhua , Yao Juming , Masuda Hiromi , Kishore Raghuvansh , Asakura Tetsuo 
Published: May 2003

AbstractHigh‐resolution solution 13C‐NMR and CD studies of Bombyx mori silk fibroin revealed the presence of an ordered secondary structure 310‐helix, in hexafluoro‐iso‐propanol (HFIP). The solid‐state structure of the silk fibroin film prepared by drying it gently from the HFIP solution still keep the structure, 310‐helix, which was studied with high‐resolution solid state 13C‐NMR. The structural transition from the 310‐helix to silk II structure, heterogeneous structure including antiparallel β‐sheet, occurred during the artificial spinning from the HFIP solution. The wide‐angle x‐ray diffraction and differential scanning calorimetry thermograms of the artificial spinning fiber after postspinning treatments were observed together with the stress–strain curves. The results emphasize that the molecular structures, controlled morphology, and mechanical properties of the protein‐based synthetic polymers can be modulated for enhancing biocompatibility. © 2003 Wiley Periodicals, Inc. Biopolymers 69: 253–259, 2003
Acid‐induced denaturation of Escherichia coli ribonuclease HI analyzed by CD and NMR spectroscopies
Authors: Yamasaki Kazuhiko , Yamasaki Tomoko , Kanaya Shigenori , Oobatake Motohisa 
Published: May 2003

AbstractAcid‐induced denaturation of the ribonuclease HI protein from Escherichia coli was analyzed by CD and NMR spectroscopies. The CD measurement revealed that the acid denaturation at 10°C proceeds from the native state (N‐state) to a molten globule‐like state (A‐state), through an apparently more unfolded state (UA‐state). In 1H–15N heteronuclear single‐quantum coherence (HSQC) spectra, cross peaks from the N‐state and those from the other two states are distinctively observed, while the UA‐state and A‐state are not distinguished from each other. Cross peaks from the UA/A‐states showed a small pH dependence, which suggests a similarity in the backbone structure between the two states. The direct hydrogen–deuterium (H–D) exchange measurement at pH with the largest population of UA‐state revealed that at least α‐helix I is highly protected in the structure of the UA‐state. A pH‐jump H–D exchange analysis showed that the protection of α‐helix I is highest also in the A‐state. The profile of hydrogen‐bond protection indicated that the structure of the A‐state is closely related to that of the kinetic folding intermediate. © 2003 Wiley Periodicals, Inc. Biopolymers 69: 176–188, 2003
NMR identification of left‐handed polyproline type II helices
Authors: Lam Sik Lok , Hsu Victor L. 
Published: May 2003

AbstractNMR characteristics of a model left‐handed 31‐helical peptide are reported in this study. With temperature and sequence corrections on the predicted random coil 15N chemical shifts, a significant 15N chemical shift deviation is observed for the model 31 peptide. The 15N chemical shift differences also correlate well with the molar ellipticities (at 220 nm) of the CD spectra at different temperatures, indicating that the 15N chemical shift is a sensitive probe for 31‐helices. The average 3JHNα and 1JCαHα values of the model peptide are determined to be 6.5 and 142.6 Hz, respectively, which are consistent with the values calculated from the geometry of 31‐helices. With careful measurements of amide 15N chemical shifts and incorporating temperature and sequence effect corrections, the 15N chemical shifts can be used together with 3JHNα and 1JCαHα to differentiate 31‐helices from random coils with high confidence. Based on the observed NMR characteristics, a strategy is developed for probing left‐handed 31‐helical structures from other secondary structures. © 2003 Wiley Periodicals, Inc. Biopolymers 69: 270–281, 2003
Local and long‐range structural effects caused by the removal of the N‐terminal polypeptide fragment from immunoglobulin L chain λ
Authors: Król Marcin , Roterman Irena , Piekarska Barbara , Konieczny Leszek , Rybarska Janina , Stopa Barbara 
Published: May 2003

AbstractThe role of the N‐terminal polypeptide fragment of the immunoglobulin l‐chain in V domain packing stability, and the flexibility of the whole chain was approached by molecular dynamics simulation. The observations were supported by experimental analysis. The N‐terminal polypeptide fragment appeared to be the low‐stability packing element in the V domain. At moderately elevated temperature it may be replaced at its packing locus by Congo red and then removed by proteolysis. After removal of Congo red by adsorption to (diethylamino)ethyl (DEAE) cellulose, the stability of complete L chain and of L chain devoid of the N‐terminal polypeptide fragment were compared. The results indicated that the N‐terminal polypeptide fragment plays an essential role in the stability of the V domain. Its removal makes the domain accessible for ANS and Congo red dye binding without heating. The decreased domain stability was registered in particular as increased root mean square (RMS) fluctuation and higher susceptibility to proteolytic attack. The long‐range effect was most clearly manifested at 340 K as independent V and C domain fluctuation in the l‐chain devoid of the N‐terminal polypeptide fragment. This is likely due to the lack of direct connections between the N‐ and C‐termini of the V domain polypeptide. In a complete V domain the connection involves residues 8–12 and 106–110 in particular. Partial or complete disruption of this connection increases the freedom of V domain rotation, while its increased cohesion strengthens the coupling of the V and C domains, making the whole L chain less flexible. © 2003 Wiley Periodicals, Inc. Biopolymers 69: 189–200, 2003