bluuebunny/crossref_metadata_2025 huggingface dataset:
Surface characterization using chemical force microscopy and the flow performance of modified polydimethylsiloxane for microfluidic device applications
Authors: Wang Bin , Abdulali‐Kanji Zamin , Dodwell Emily , Horton J. Hugh , Oleschuk Richard D.
Published: April 2003

The widespread interest in micro total analysis systems has resulted in efforts to develop devices in cheaper polymer materials such as polydimethylsiloxane (PDMS) as an alternative to expensive glass and silicon devices. We describe the oxidation of the PDMS surface to form ionizable groups using a discharge from a Tesla coil and subsequent chemical modification to augment electroosmotic flow (EOF) within the microfluidic devices. The flow performance of oxidized, amine‐modified and unmodified PDMS materials has been determined and directly compared to conventional glass devices. Exact PDMS replicas of glass substrates were prepared using a novel two step micromolding protocol. Chemical force microscopy has been utilized to monitor and measure the efficacy of surface modification yielding information about the acid/base properties of the modified and unmodified surfaces. Results with different substrate materials correlates well with expected flow modifications as a result of surface modification. Oxidized PDMS devices were found to support faster EOF (twice that of native PDMS) similar to glass while those derivatized with 3‐aminopropyl triethoxysilane (APTES) showed slower flow rates compared to native PDMS substrates as a result of masking surface charge. Results demonstrate that the surface of PDMS microdevices can be manipulated to control EOF characteristics using a facile surface derivatization methodology allowing surfaces to be tailored for specific microfluidic applications and characterized with chemical force microscopy.
Reversed‐phase high‐performance liquid chromatography prefractionation prior to two‐dimensional difference gel electrophoresis and mass spectrometry identifies new differentially expressed proteins between striate cortex of kitten and adult cat
Authors: Van den Bergh Gert , Clerens Stefan , Vandesande Frans , Arckens Lutgarde
Published: April 2003

Two‐dimensional difference gel electrophoresis (2‐D DIGE), in combination with mass spectrometry, is a highly effective method for the rapid and reproducible detection of differentially expressed proteins. This approach, however, has the unfortunate drawback that it preferentially displays rather abundantly expressed proteins. Nevertheless, comparison of the protein expression levels of the striate cortex of adult cats and 30‐day‐old kittens, resulted in the identification of several proteins related to postnatal brain development and possibly age‐dependent plasticity as well (Van den Bergh et al., J. Neurochem. 2003, in press). The goal of the present study was the selective enrichment and identification of less abundant proteins within the same paradigm. Hereto, we performed a reversed‐phase chromatography prefractionation of our tissue lysate to separate the proteins in four fractions based on their hydrophobicity prior to 2‐D DIGE analysis. This approach not only confirmed the differential expression levels of a number of proteins from the previous study, but also identified three additional proteins preferentially expressed in kitten visual cortex and five additional proteins with higher expression levels in adult cat visual cortex. These spots were not visible on the total tissue lysate protein maps, indicating that the high‐performance liquid chromatography (HPLC) prefractionation enabled us to visualize additional, less abundant proteins.
Torsional response of symmetric buildings to incoherent and phase‐delayed earthquake ground motion
Authors: Heredia‐Zavoni Ernesto , Leyva Adrián
Published: April 2003

This paper studies the effect of coherency loss and wave passage on the seismic torsional response of three‐dimensional, multi‐storey, multi‐span, symmetric, linear elastic buildings. A model calibrated against statistical analyses of ground motion records in Mexico City is used for the coherency function. The structural response is assessed in terms of shear forces in structural elements. Incoherence and wave passage effects are found to be significant only for columns in the ground level of stiff systems. The increase of column shears in the ground level is much higher for soft than for firm soil conditions. For the torsionally stiff systems considered, it is found that incoherent and phase‐delayed ground motions do not induce a significant rotational response of the structure. The use of a code eccentricity to account for torsion due to ground motion spatial variation is assessed. On firm soil, the use of a base shear along with an accidental eccentricity results in highly overestimated shear forces; however, for soft soil conditions, code formulations may result in underestimated shear forces. Copyright © 2003 John Wiley & Sons, Ltd.
14‐3‐3γ Is upregulated by in vitro ischemia and binds to protein kinase Raf in primary cultures of astrocytes
Authors: Chen Xiao Qian , Chen Jian Guo , Zhang Yun , Hsiao Wendy Wen Luan , Yu Albert Cheung Hoi
Published: April 2003

The 14‐3‐3 protein family comprises critical regulatory molecules involved in signaling during cell division, proliferation, and apoptosis. Despite extensive study, the functions of the 14‐3‐3 proteins in brain remain unclear. 14‐3‐3γ, a subtype of the 14‐3‐3 family of proteins, was thought to be brain‐ and neuron‐specific. Using RNA arbitrarily primed PCR, we identified an upregulated cDNA fragment of the 14‐3‐3γ gene in primary cultures of astrocytes. Using Northern blot analysis, we confirmed this fragment was brain‐specific. In cultures of astrocytes, 14‐3‐3γ genes and proteins were differentially expressed at different ages and the proteins were distributed only in the cytoplasm. These results indicated that 14‐3‐3γ was not neuron‐specific but also expressed in astrocytes. The function of this protein in brain is unclear. Northern and Western blot analyses demonstrated that 14‐3‐3γ mRNA and protein were upregulated in cultured astrocytes in an anaerobic chamber‐induced ischemia model. The induction of 14‐3‐3γ proteins was neither suppressed by an MAP kinase inhibitor (U0126) nor a PI‐3 kinase inhibitor (LY294002). These data indicated that induction of 14‐3‐3γ might not involve PI‐3 and MAP kinase‐dependent pathways. Using coimmunoprecipitation, we demonstrated that endogenous 14‐3‐3γ bound to c‐Raf‐1 and p‐Raf 259. As Raf is one of the critical serine/threonine kinases controlling cell growth, differentiation, and death, the binding of 14‐3‐3γ to Raf indicates the critical role of this protein in ischemia‐induced apoptosis and the changes in signal transduction in astrocytes in culture. GLIA 42:315–324, 2003. © 2003 Wiley‐Liss, Inc.
Malignant peripheral nerve sheath tumor cell invasion is facilitated by Src and aberrant CD44 expression
Authors: Su Weiping , Sin Mihaela , Darrow Andrea , Sherman Larry S.
Published: April 2003

Malignant peripheral nerve sheath tumors (MPNSTs) are aggressive malignancies that arise within peripheral nerves. These tumors occur with increased incidence in patients with neurofibromatosis type 1 (NF1), exhibiting increased Ras activity due to loss of the NF1 gene product, neurofibromin, and abnormal expression of the epidermal growth factor receptor (EGFR). We previously found that MPNSTs express increased levels of the CD44 family of transmembrane glycoproteins that have been implicated in tumor cell invasion and metastasis. In two MPNST cell lines, we have found that elevated CD44 expression and cell invasion are dependent on Src kinase activity but are independent of mitogen‐activated protein kinases (MAPK) kinase (MEK) activity. In contrast, inhibition of Src kinase activity has no influence on MPNST cell proliferation. Reduction of CD44 levels, using antisense oligonucleotides, results in reduced MPNST cell invasion in vitro, suggesting that Src contributes in part to MPNST cell invasion by increasing CD44 levels. At least some of this increased CD44 expression results from elevated EGFR levels through a Src‐dependent mechanism, consistent with the notion that EGFR promotes constitutive Src activation in MPNSTs. These data indicate that Src and CD44 are putative targets for the treatment of MPNST invasion and metastasis. GLIA 42:350–358, 2003. © 2003 Wiley‐Liss, Inc.
Human malignant glioma cells express semaphorins and their receptors, neuropilins and plexins
Authors: Rieger Johannes , Wick Wolfgang , Weller Michael
Published: April 2003

Semaphorins comprise a family of molecules implicated in the guiding of growing axons and neuronal progenitor cells. Further, semaphorins have been suggested to play a role in cancer metastasis. Neuropilins 1 and 2 are cell surface receptors for soluble class 3 semaphorins. Plexins are direct receptors for membrane‐bound semaphorins and, by binding to neuropilins, coreceptors necessary for class 3 semaphorin signaling. We here report that human malignant glioma cell lines express neuropilins 1 and 2 mRNA and protein, as well as either plexin A1, A2, or B1. Further, all glioma cell lines express SEMA3A and SEMA3C and exhibit SEMA3A binding sites. Exogenous SEMA3A expressed in 293 or U87MG cells has no collapsing or chemorepulsive activities on glioma cells as determined by F‐actin staining and collagen coculture assays. In summary, human glioma cells express class 3 semaphorins and receptors for soluble and membrane‐bound semaphorins, suggesting a possible role of the semaphorin/neuropilin system in the interactions of human malignant glioma with the host's central nervous and immune systems. GLIA 42:379–389, 2003. © 2003 Wiley‐Liss, Inc.
Sequential loss of myelin proteins during Wallerian degeneration in the rat spinal cord
Authors: Buss Armin , Schwab Martin E.
Published: April 2003

Axotomy of nerve fibers leads to the subsequent degeneration of their distal part, a process termed Wallerian degeneration (WD). While WD in the peripheral nervous system is usually followed by regeneration of the lesioned axons, central nervous system (CNS) neurons are generally unable to regrow. In this study, we investigated the process of WD in the dorsal columns of the rat spinal cord rostral to a mid‐thoracic lesion. We confirm earlier studies describing a very delayed microglial and an early and sustained astroglial reaction finally leading to scar formation. Interestingly, we found a differential time course in the loss of myelin proteins depending on their location. Proteins situated on the periaxonal myelin membrane such as myelin associated glycoprotein disappeared early, within a few days after lesion, concomitantly with cytoskeletal axonal proteins, whereas compact myelin and outer myelin membrane proteins such as MBP and Nogo‐A remained for long intervals in the degenerating tracts. Two distinct mechanisms are probably responsible for this difference: processes of protein destruction emanating from and initially probably located in the axon act on a time scale of 1–3 days. In contrast, the bulk of myelin destruction is due to phagocytosis known to be slow, prolonged, and inefficient in the CNS. These results may also have implications for future intervention strategies aiming at enhancing CNS regeneration. GLIA 42:424–432, 2003. © 2003 Wiley‐Liss, Inc.
Differential effects of apotransferrin on two populations of oligodendroglial cells
Authors: García C.I. , Paez P. , Soto E.F. , Pasquini J.M.
Published: April 2003

In the central nervous system (CNS), apotransferrin (aTf) is produced by oligodendroglial cells (OLGcs), and aTf is essential for cell survival. We previously demonstrated that a single intracranial injection of aTf in 3‐day‐old rats accelerates differentiation of OLGc and that aTf acts at early stages of development on certain populations of OLGcs, promoting accelerated maturation, with no effect on late markers of cell differentiation. The objective of the present study was to analyze OLGc maturation at two different stages of rat development, 4 and 10 days of age, in OLGcs isolated from the brain after intracranial injection of aTf at 3 days of age, and to explore the in vitro effect of aTf added to cultures of OLGc isolated from aTf‐injected and control brains. The maturational cell stages were identified by immunocytochemistry with different OLGc markers and by analysis of their morphological complexity. The OLGcs isolated from 4‐ and 10‐day‐old animals intracranially injected with aTf were more differentiated than control cells. Treatment with aTf of the cultures of OLGcs that were isolated from 4‐day‐old saline‐injected control animals induced their differentiation, while a similar treatment of the cultures of OLGcs that were isolated from 10‐day‐old animals did not induce further maturation of the cells. The results presented in the present report demonstrate that the in vivo effects of aTf on OLGc maturation can be reproduced in cultures and that the effects of aTf occur early in development during a narrow, transient “temporal window” within which OLGcs are sensitive to its action. GLIA 42:406–416, 2003. © 2003 Wiley‐Liss, Inc.
Generation and High‐Resolution Photoelectron Spectroscopy of Small Organic Radicals in Cold Supersonic Expansions
Authors: Willitsch Stefan , Dyke John M. , Merkt Frédéric
Published: April 2003

A general method of generating radicals in cold supersonic expansions in the gas phase is presented. The method relies on excimer laser photolysis of suitable precursor molecules in a thin quartz capillary mounted at the orifice of a pulsed gas nozzle and can easily be combined with vacuum‐UV photoionization mass spectrometry and high‐resolution photoelectron spectroscopy to study the reactivity and the rovibronic energy level structure of neutral radicals and their ions, as well as to determine highly accurate adiabatic ionization energies. The characteristics of the radical source are described in detail, and its performance is illustrated by mass spectrometric and high‐resolution photoelectron spectroscopic investigations of NH2, CH2, CH3, C2H, C2H3, and C2H5. The radical source is not only suitable to produce cold samples (rotational temperature of ca. 30 K) of radicals of moderate reactivity, such as NH2, CH3, or C2H5, but it is also useful to prepare highly reactive radicals (e.g., C2H) for spectroscopic investigations.
Chiral and Achiral Crystal Structures
Authors: Flack Howard D.
Published: April 2003

An extensive study and analysis of the concepts, classification, presentation, and nomenclature of chirality and lack of chirality in crystal structures and their constituents is presented. Oriented crystal structures are classified. The chirality rules for existence of molecular crystal structures are examined and the relation to segmentation and latent symmetry highlighted. The nomenclature of chirality and related terms, and the relationship of chirality to optical activity is covered. The uses and limitations of the Euclidean normalizer are treated. An improved glossary of terms is included.
Magnetic Circular Dichroism of the Long‐Wavelength π‐π* Transitions in Nitrogen‐Containing Heteroconjugated Aromatic Compounds and in Selected Ruthenium Complexes
Authors: Kleindienst Peter , Belser Peter , Wagnière Georges H.
Published: April 2003

The long‐wavelength magnetic circular dichroism (MCD) spectra of some nitrogen‐containing heteroconjugated aromatic compounds have been recorded and interpreted on the basis of quantum‐chemical model calculations. In particular, the dependence of the MCD bands on the positions of the N‐atoms inside the aromatic rings and on substituents has been investigated.

Some of the compounds considered form Ru2+ complexes. The influence of complexation on the long‐wavelength π‐π* bands of the ligands has also been recorded and discussed.
Differentiating Type A behaviour and hyperactivity using observed motivation during a reaction time task
Authors: Nyberg Lilianne , Bohlin Gunilla , Berlin Lisa , Janols Lars‐Olof
Published: April 2003

In light of the previously found overlap between Type A behaviour as measured by the Matthews Youth Test for Health (MYTH) and hyperactivity scales, the overall aim of this study was to clarify the standing of MYTH‐defined Type A behaviour relative to hyperactivity and Attention‐Deficit/Hyperactivity Disorder (ADHD), using observed task motivation and performance on a choice reaction‐time task, the Complex Reaction Time (CRT) measure. This study included 21 boys exhibiting Type A behaviour, 22 ADHD boys, 20 non‐clinically hyperactive boys, and 20 non‐hyperactive boys, between the ages of 6 and 13 years. It was proposed that a differentiation of constructs would be possible using observed task motivation if the MYTH were a discriminantly valid measure of Type A behaviour. Results showed that the MYTH‐defined Type A group differed from the clinically diagnosed ADHD group, although it was markedly similar to the non‐clinical hyperactive group, displaying comparable CRT performance and low level of task motivation. Type A behaviour correlated to CRT performance and task motivation in a way which was conceptually more indicative of hyperactivity than of Type A behaviour, which questions the validity of the MYTH as a measure of the Type A construct. The MYTH Impatience subscale was found to be particularly impure with regard to hyperactivity. Copyright © 2003 John Wiley & Sons, Ltd.
Effect of Self‐Assembly of Sodium Acrylate on the Crystallization of Calcium Carbonate
Authors: Guo Yuming , Yang Lin , Yang Xiaoli , Zhang Xiuying , Zhu Shufa , Jiang Kai
Published: April 2003

Based on the primary principles of biomineralization, CaCO3 similar to that in biominerals was synthesized through biomimetic synthesis under the self‐assembly of sodium acrylate. In our experiment, the formation of the calcium carbonate and the polymerization of sodium acrylate took place simultaneously through the appropriate method. The result shows that the self‐assembly process of the sodium acrylate has an important effect on the crystallization and growth of the calcium carbonate. The result is significant for the mimetics of the biomineralization conditions and the research of biomimetic materials synthesis.

SEM of crystal product A.

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SEM of crystal product A.
Influence of Complexing Polyanions on the Thermostability of Basic Proteins
Authors: Ivinova Olga N. , Izumrudov Vladimir A. , Muronetz Vladimir I. , Galaev Igor Yu. , Mattiasson Bo
Published: April 2003

Lysozyme (Lyz), chymotrypsinogen (Cht), and glyceraldehyde‐3‐phosphate dehydrogenase (GAPDH) were used as model proteins capable of forming water‐soluble polyelectrolyte complexes with linear synthetic polyanions. The complex formation with sodium poly(methacrylate) (PMA), sodium poly(acrylate) (PAA), sodium poly(anetholsulfonate) (PAS), and potassium poly(vinylsulfate) (PVS) markedly reduced the temperature of protein denaturation, Tmax, as determined by differential scanning calorimetry (DSC). The effect of sodium poly(styrenesulfonate) (PSS) on Lyz was so drastic that the protein melting peak was not observed at all during DSC measurements. The temperature shift, most pronounced for Lyz, increased upon substitution of the polyanions according to the following series: PMA < PVS < PAA < PAS < PSS. Decomposition of the complexes by addition of either sodium chloride or poly(N‐ethyl‐4‐vinylpyridinium) cation completely restored the initial Tmax of the protein (except for PSS and PAS). The complex formation slightly affected the enzyme activity up to temperatures close to Tmax of the polyanion–protein complex. On further heating, the activity of the complex decreased steeply, whereas the free enzyme maintained a high activity. The data obtained strongly suggest that the protein–polyelectrolyte interactions in solution, while leaving the thermostability and activity of the proteins practically unaffected over a rather wide temperature range, result in the effective denaturation of proteins once a certain critical temperature is achieved. This finding appears to be crucial for further development of immobilized enzymes in biotechnology and essential for understanding mechanisms and principles of the functioning of proteins immobilized on charged matrices in vivo.

Temperature dependence of partial heat capacity ΔCp of free Lyz and Lyz in the mixtures with PMA.

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Temperature dependence of partial heat capacity ΔCp of free Lyz and Lyz in the mixtures with PMA.
Asymmetric induction radical copolymerization of (−)‐3‐menthyl hydrogen maleate with styrene
Authors: Kurokawa Masahiro , Minoura Yuji
Published: April 2003

Radical copolymerizations of (−)‐3‐menthyl maleate (1) were carried out with styrene, with indene, and with isobutyl vinyl ether. The copolymers were hydrolyzed with potassium hydroxide. After hydrolysis the copolymers were still optically active, due to an introduction of asymmetry into the main chain of the copolymer. The mechanism of asymmetric induction and the position of the new asymmetric center are discussed based on measurements of UV spectra, optical rotation, optical rotatory dispersion, and circular dichroism.
Enzymes immobilisées, 12. Emploi de polyacrylamides, contenant des groupes hydroxy méthyles pour l'immobilisation de l'invertase, de la glucose oxydase, de l'α‐chymotrypsine, de l'uréase et de la β‐galactosidase
Authors: Brown Eric , Touet Joël
Published: April 2003

Invertase, glucose oxidase, α‐chymotrypsin, urease, and β‐galactosidase were immobilized on polymers 2a or 2b (in bead or gel form), using p‐benzoquinone or cyanogen bromide as activating reagents. The resulting insoluble derivatives were found to have high total enzymatic activities (76–83% in the case of invertase) retaining 62 to 84% of their initial activity after storing for 3 to 8 weeks. On the other hand, a column of β‐galactosidase immobilized on Trisacryl‐H was used for 120 h continuous production of glucose.
Functional Polystyrene Combs and Dendrigrafts, 1
Authors: Schappacher Michel , Bernard Julien , Deffieux Alain
Published: April 2003

Peripherally functionalized arborescent polystyrenes (PS) of various architectures and chain parameters (backbone DPn, number and DPn of branches, number of termini and functions) were prepared by covalently assembling different elementary building blocks of controlled DPn, synthesized using anionic and cationic polymerization techniques. These multifunctional dendritic macromolecules have narrow polydispersities (< 1,2), and exhibit molar masses ranging from 1 × 105 to 5 × 106 g/mol for combs, and from 3 × 106 to 13 × 106 g/mol for dendrigrafts. In this latter series the number of terminal bis(hydroxymethyl) functions per macromolecule can be as high as 2 000. The calculated loading capacity (number of functional groups/g of polymer) was found to depend mainly on the molar mass of the last PS building block. It can approach 10−3 eq/g for low PS DPn grafts (DPn ≈ 10).

First generation dendrigrafts.

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First generation dendrigrafts.
Polymer Nanoparticles with Activated Ester Surface by Using Functional Surfmers
Authors: Herold Marc , Brunner Herwig , Tovar Günter E. M.
Published: April 2003

Two new polymerizable surfactants (surfmers), p‐[11‐(acrylamido)‐undecanoyloxy]phenyldimethylsulfonium methylsulfate (AUPDS) and p‐[11‐(methacrylamido)undecanoyloxy]phenyldimethylsulfonium methylsulfate (MUPDS), were synthesized and used for the preparation of functional polymer nanoparticles. The surfmers were characterized (cmcAUPDS = 6.0 ± 0.2 mmol · L−1; cmcMUPDS = 3.2 ± 0.2 mmol · L−1) and employed in emulsion polymerization with methyl methacrylate as a comonomer. Depending on the surfmer‐to‐comonomer ratio, the resulting particles had a dynamic light scattering diameter between 109 nm and 167 nm. Scanning electron microscopy confirmed a very narrow size distribution. The particles showed a ζ‐potential of 20 to 24 mV as measured by micro‐electrophoresis, corresponding to the electrostatic stabilization by the positively charged sulfonium group of the surfmer. The reactivity of the particle bound active ester was determined by titration of the latex with a fluorescent probe and subsequent fluorescence analysis. 6‐Aminofluoresceine was immobilized from 0.8 μmol to 9.6 μmol per 1 g particles depending on the AUPDS starting concentration in emulsion polymerization.

Scanning electron microscopy images of poly(MMA‐co‐AUPDS) particles (sample PA 6, 0.25 mol‐% AUPDS) showing the narrow size distribution over a larger sample area.

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Scanning electron microscopy images of poly(MMA‐co‐AUPDS) particles (sample PA 6, 0.25 mol‐% AUPDS) showing the narrow size distribution over a larger sample area.
Photoinduced Changes of the Refractive Index in Substituted Fluorenyl‐p‐phenylene Copolymers
Authors: Schöfberger Wolfgang , Zaami Noreddine , Mahler Kai Arnulf , Langer Gregor , Jakopic Georg , Pogantsch Alexander , Kern Wolfgang , Stelzer Franz
Published: April 2003

A series of substituted 9,9′‐dihexylfluorenylene‐p‐phenylene copolymers (DFPP) were synthesised via a Suzuki coupling reaction. The copolymers were chemically modified to introduce photoreactive functionalities. Thiocyanate groups (SCN) were attached onto a side chain of the DFPP copolymers. After exposure to UV light the SCN groups underwent photoisomerisation to the corresponding isothiocyanate groups (NCS). A significant change of the refractive index was observed after UV illumination. After this process the polymer was further modified by a gas phase reaction with propylamine to transform the photo‐generated NCS groups to derivatives of thiourea. An additional variation of the refractive index, as well as an increase of the film thickness h(Δh + 15%), was observed after this reaction. All polymerisation products were characterised by means of gel permeation chromatography, thermoanalysis as well as NMR and IR spectroscopy. The polymers are thermally stable with decomposition temperatures of around 260 °C and glass transition temperatures in the range of 150–155 °C. The polymers display blue photoluminescence, which remains unchanged after UV modification and reaction with propylamine. A convenient way to produce index and relief patterns in films of conjugated polymers is demonstrated.

Photoreactive DFPP copolymer and modified products.

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Photoreactive DFPP copolymer and modified products.
Solution properties of polybutadiene and trans‐polyisoprene fractions
Authors: Cooper W. , Eaves D. E. , Vaughan G.
Published: April 2003

Linear polybutadienes, prepared with butyllithium as catalyst, and polybutadienes branched by exposure to γ‐radiation have been fractionated and the fractions examined by osmometry and light scattering. Turbidimetric second virial coefficients (A2τ) of mixed polymer fractions are virtually the same as those of the higher molecular weight components of the mixtures for most compositions. This is true both for mixtures of linear with linear and linear with branched polymer. The higher the molecular weight of the fraction, the greater the effect; the addition of 1% microgel to a linear polymer reduced A2τ by a factor of three. The presence of microgel or high molecular weight branched polymer has been shown to be responsible for the very high molecular weights previously reported for polybutadienes from light scattering measurements. It is conveniently removed by shaking the solutions with calcium sulfate. Second virial coefficients obtained either by light scattering or osmometry are, within the limits of experimental error, uninfluenced by branching in the polymer. In general those factors which lead to increased branching also result in increased polydispersity, and it is the latter which results in the decrease in A2τ. The fall of the osmotic second virial coefficient (A2τ) with molecular weight is much smaller than would be calculated theoretically, and the fall in A2τ is greater than would be expected, notwithstanding the fact that for some of the fractions M̄u/M̄n < 1.1. This indicates that A2π is sensitive to the low molecular weight species presented in the fractions, whereas the reverse must apply to A2τ. Natural of synthetic trans‐polyisoprene showed analogous behavior to polybutadiene, although, owing to experimental difficulties, sharp branched fractions could not be obtained. The following viscosity–molecular weight relationships were obtained in benzene solution: [η] = 1.45 × 10−4M0.76 for butyllithium‐catalyzed polybutadienes, and [η] = 4.37 × 10−4M0.65 for natural and synthetic trans‐polyisoprenes.
Proton magnetic resonance absorption in dry nylons 66 and 610
Authors: Jones D. W.
Published: April 2003

A comparison of the temperature dependence of the nuclear resonance line‐width and second moment for dried chip and rod samples of nylon 66 and 610, as measured by several authors, reveals discrepancies within the range 80 to 400°K. Room temperature measurements with a Pound‐Watkins spectrometer suggest that neither linewidth nor second moment varies greatly with radiofrequency field, although saturation may occur at low temperatures. It is concluded that the nuclear resonance differences reflect sample differences, at least for the higher temperatures. Evidence is considered for the decomposition of the continuous nuclear resonance changes in polyamides into more discrete “transitions;” in nylon 66, there are nuclear resonance effects near 120, 200, 330, and 370°K.
Molecular conformation of linear polyphosphonitrile chloride
Authors: Giglio E. , Pompa F. , Ripamonti A.
Published: April 2003

The interpretation of the x‐ray fiber photograph of stretched linear polyphosphonitrile chloride was carried out by means of Fourier transform methods with the aim of establishing the chain conformation without considering the mode of packing in the crystal lattice. The results of such an analysis lead to the conclusion that the radial distribution of the intensities on the layer lines is consistent with a twofold helical conformation characterized by values of 156° and 14° for the angles of rotation around the PN and NP bonds, the cis‐planar conformation corresponding to angles of rotation of π and 0°.
A general treatment of equilibrium copolymerization
Authors: Tobolsky A. V. , Owen G. D. T.
Published: April 2003

A general theory of equilibrium copolymerization is developed. The theory is compared with published experimental results on sulfur‐selenium copolymers. The equilibrium constants developed previously for sulfur and for selenium homopolymerization are utilized in this new copolymerization theory, and no other mathematical assumptions are made. The theory gives a quite remarkable agreement with the experimental results.
Investigation of polyethylene with the analytical ultracentrifuge
Authors: Moore Louis D. , Greear George R. , Sharp John O.
Published: April 2003

A technique has been developed for studying polyethylene with the Spinco Model E analytical ultracentrifuge. 1‐Chloronaphthalene at 120°C. is used as the solvent. A variety of whole polymers from several sources was studied and found to differ considerably in the distribution of their sedimentation rates. Most of the low‐density polyethylenes exhibited a high molecular weight tail (that is, a fast‐moving fraction), whereas a high‐density sample showed a low molecular weight tail. In general, the ultracentrifuge Schlieren patterns showed a direct correlation with light‐scattering results—polymers with high weight‐average molecular weights showed broad patterns containing fastmoving tails. There was also a direct correlation between broad patterns and high values for the Flory expansion factor, α. An exception to the agreement between high weight‐average molecular weight and broad Schlieren pattern was found for a sample (B‐1) which was shown by electron microscopy to have very large molecules present in its make‐up. These large molecules, because of their size, greatly influence the light scattering measurements but, because they were present in relatively small numbers, they were not observed in the Schlieren pattern. A number of fractions were also investigated. The Schlieren patterns obtained with fractions prepared by the Guillet et al. adaptation of the chromatographic method of Baker and Williams were sharper than those obtained with fractions prepared by the extraction method of Desreux and Spiegels. Estimates of the degrees of long‐chain branching were made from measurements of intrinsic viscosities and sedimentation rates of fractions. A knowledge of the molecular weight is not required for this estimate; therefore, this method has some advantage over the older method involving light scattering measurements. There is an excellent correlation between the number of branches per molecule and the intrinsic viscosity for a number of fractions obtained from a low‐density polyethylene of broad distribution. This result is predicted from the theoretical considerations of Beasley. It was also found that fractions from polyethylenes of narrower distribution contained fewer branches per molecule than fractions of comparable intrinsic viscosity from a polymer of broader distribution. This result confirms Beasley's theory that the long‐chain branching mechanism is responsible for the broad molecular weight distributions in low‐density polyethylenes. These differences in branching and molecular weight distribution are most likely responsible for many of the differences in behavior among various polyethylenes.
Chemical transformation of insoluble copolymers of styrene
Authors: Trostyanskaya E. B. , Losev I. P. , Tevlina A. S. , Makarova S. B. , Nefedova G. Z. , Syan'‐Zhao Lu
Published: April 2003

With the objective of synthesizing various insoluble polyelectrolytes and complexes, the chemical reactions of insoluble styrene copolymers (styrene–divinylbenzene or styrene–diallyl maleate) and of copolymers which become insoluble during the synthesis (styrene–butadiene) were studied. By substituting the chlorine atom in chloromethylated copolymers for ionic and complexogenic groups new polymer ion exchangers and complexes have been obtained. Chloromethylation of the copolymers was accomplished with the aid of paraformaldehyde and hydrogen chloride in the presence of zinc chloride in dichloroethane (copolymer I). The extent of conversion is determined by the structure and swelling capacity of the polymer and varies between 65 and 95%. The chlorine atom of copolymer I is completely replaced by an amino group under the action of triethanolamine (copolymer II). The polyelectrolytes formed possess the properties of quaternary ammonium bases with basicity 2.6–2.9 meq./g. The high swelling capacity of copolymer II has been utilized for investigating the possibility of polymerizing vinyl derivatives in the copolymer network. The polymerization of α‐methylvinylpyridine in copolymer II granules leads to a polymer‐in‐copolymer system containing up to 30% polymer and incapable of separation by extraction. The basicity of such a system attains a value of 5.1 meq./g. The replacement of chlorine in copolymer I by phosphine or sulfides gave new insoluble polymer of the phosphonium (copolymer III) or sulfonium (copolymer IV) type. A comparative study has been made of the properties of the ammonium, phosphonium, and sulfonium salts. From copolymer II insoluble complexes containing an aminotriacetic or aminodiacetic acid group
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or a β′, β″, β‴‐triaminotriethylamine group
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have been obtained. The instability constants of the Ni++, Cu++, Ca++, and Zn++ complexes with the insoluble polymeric complexes have been determined.
Copolymerization characteristics of sodium styrenesulfonate
Authors: Grabiel C. E. , Decker D. L.
Published: April 2003

The reactivity ratios (r1 and r2) of sodium styrenesulfonate (M1) with different monomers in aqueous solution were determined by the usual procedures of copolymerization to low conversion followed by isolation and analysis of the copolymer. The values of r1 and r2, respectively, for the monomers (M2) studied were found to be: acrylonitrile, 1.5, 0.05; acrylic acid, 1.0, 0.10; and sodium acrylate, 2.3, 0.34. The substitution of the sodium salt for the potassium salt of styrenesulfonic acid did not alter the reactivity of the monomer. The Q and e values determined for sodium styrenesulfonate in aqueous solution are 2.0 and −0.4, respectively. The values previously published for potassium styrenesulfonate in dimethylformamide solution, 9.18 and 1.32, respectively, indicate that the styrenesulfonic acid is a highly reactive monomer containing a vinyl group with a polarity strongly positive with respect to styrene. However, the Q and e values presented here denote a reactive monomer with the vinyl group polarized only slightly more positive than styrene. The consequences of these differences are shown in the prediction of copolymer compositions.
New Direction in Organopalladium Chemistry: Structure and Reactivity of Unsaturated Hydrocarbon Ligands Bound to Multipalladium Units
Authors: Murahashi Tetsuro , Ogoshi Sensuke , Kurosawa Hideo
Published: April 2003

Examination of the manner of interaction between Pd(0) and allylpalladium(II) complexes, both being involved
as key intermediates in Pd‐catalyzed allylic coupling, led us to discover a new role for such combinations in affecting the
stereochemistry of the transformations. A similar investigation of the system involving Pd(0) and allenyl/propargyl
complexes of Pd(II) led to the discovery of dinuclear Pd(I)Pd(I) complexes containing bridging
allenyl/propargyl ligands, which exhibited novel structural and reactivity aspects of great synthetic significance. A systematic
comparison was made between the structure, stability, and reactivity of allyl and allenyl/propargyl ligands in dinuclear complexes
and those in mononuclear counterparts. On the basis of MO calculations, coordination behavior specific to the ligands of the dinuclear
complex is attributed to the occurrence of the back‐donating interaction from filled PdPd bonding orbitals to vacant
ligand π* orbitals. Similar bonding features are the origin of the ready synthesis of novel one‐dimensional sandwich
complexes composed of conjugated polyene ligands and linear polypalladium chains. A substitutionally labile dipalladium complex reacts
with an equimolar amount of trienes or alkynes to give formal [4π + 2σ] or
[2π + 2σ] adducts, respectively, which undergo further unique transformations with additional
unsaturated substrates. © 2003 The Japan Chemical Journal Forum and Wiley Periodicals, Inc., Chem Rec 3: 101–111; 2003:
Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.10052
Stimulation of transforming growth factor‐β1 transcription by cyclosporine
Authors: Prashar Y. , Khanna A. , Sehajpal P. , Sharma V.K. , Suthanthiran M.
Published: April 2003

In searching for a candidate mechanism for the immunosuppressive as well as fibrogenic consequences of cyclosporine usage, we have explored the hypothesis that cyclosporine stimulates transcription of transforming growth factor‐β
1 (TGF‐β
1), a multifunctional cytokine endowed with immunosuppressive and fibrogenic properties. Our results demonstrate that cyclosporine (i) stimulates TGF‐β
1 promoter‐dependent transcription of chloramphenicol acetyl transferase gene in transiently transfected human A‐549 cells, (ii) stimulates the synthesis of TGF‐β
1 RNA transcripts in human T cells, and (iii) permits the expression/emergence of DNA regulatory proteins (retinoblastoma control factor‐1 (RCF‐1) and RCF‐2) that bind and regulate TGF‐β
1 promoter activity. Our studies demonstrate for the first time that cyclosporine stimulates TGF‐β
1 gene transcription and suggest a novel mechanism of action of cyclosporine.
A novel member of the TRAF family of putative signal transducing proteins binds to the cytosolic domain of CD40
Authors: Sato Takaaki , Irie Shinji , Reed John C.
Published: April 2003

CD40 is a member of the tumor necrosis factor receptor (TNF‐R) family that regulates B‐lymphocyte proliferation, immunoglobulin class‐switching, and apoptosis through poorly defined signal transduction mechanisms. Using a yeast two‐hybrid method, cDNAs were obtained that encode a novel protein, CD40‐associated protein‐1 (CAP‐1), which binds specifically to the cytosolic domain of CD40 but not TNF‐R1, TNF‐R2, or Fas. The CAP‐1 protein contains a C‐terminal domain that shares strong amino acid sequence homology with a unique domain found recently in two putative signal transducing proteins that bind to the TNF‐R2 cytosolic tail, TRAF1 and TRAF2. This C‐terminal region of CAP‐1 was sufficient to mediate binding to CD40 and homodimerization of CAP‐1 proteins. The N‐terminal portion of CAP‐1 contains a RING finger motif and three zinc finger‐like domains similar to those found in several regulatory proteins that interact with DNA or RNA. CAP‐1 thus represents a new member of a family of potential signal transducing proteins that contain a conserved domain (the TRAF domain), bind to the cytosolic regions of particular members of TNF‐R family proteins, and that can form homo‐ and heterotypic dimers.
Chaos in DNA partition during the last mitoses of the proliferative life‐span of human fibroblasts
Authors: Macieira-Coelho A.
Published: April 2003

We have followed with autoradiography the course of DNA synthesis and with cytofluorometry the partition of DNA during mitosis, through the different phases of the life‐span of human fibroblasts. Towards the end of the proliferative potential of the cell population, DNA synthesis was disturbed during the late part of the S period. The DNA content of metaphases and of anaphases had a normal Gaussian distribution during the whole proliferative life‐span of the cell population. At the very end, however, when cells entered the post‐mitotic phase, the distribution of DNA content deviated from the normal Gaussian probability, becoming significantly skewed.
Changes in ascorbate peroxidase activities during fruit ripening in Capsicum annuum
Authors: Schantz Marie-Luce , Schreiber Hélène , Guillemaut Pierre , Schantz Rodolphe
Published: April 2003

The ascorbate peroxidase (APX) system was studied in Capsicum annuum during fruit ripening. A large increase in organelle APX activity was found during chloroplast‐chromoplast transition whereas only a slight difference was detected in total fruit extracts. On native gels, four different isoforms were found in total fruit extracts but the patterns for red and green fruit were quite different. In isolated organelles, six isozymes were found and a comparison of the patterns showed significant differences. A cDNA encoding a cytosolic APX was cloned and sequenced. The corresponding transcript was shown to increase 3–4‐fold during fruit ripening.
Rapamycin, FK506 and cyclosporin A inhibit human prolactin gene expression
Authors: Wera Stefaan , Belayew Alexandra , Martial Joseph A.
Published: April 2003

In this work we demonstrate that transcription of the human prolactin gene is inhibited by the immunosuppressants FK506 (IC50 = 25 NM), cyclosporin A (IC50 = 190 NM) and rapamycin (IC50 = 25 NM). Whereas the effect of FK506 and cyclosporin A is specific for prolactin gene transcription, rapamycin has a more general effect on transcription and/or translation in pituitary cells. In view of recent work demonstrating the immunoactivating role of prolactin, these results suggest that inhibition of prolactin gene expression in the pituitary may contribute to the mechanism of action of immunosuppressants.
The assembly state of the intermediate filament proteins desmin and glial fibrillary acidic protein at low ionic strength
Authors: Kooijman Martin , van Amerongen Herbert , Traub Peter , van Grondelle Rienk , Bloemendal Michael
Published: April 2003

The low ionic strength structures of the type III intermediate filament (IF) proteins desmin and glial fibrillary acidic protein (GFAP) have been studied by transient electric birefringence measurements. Flexible dimers with a length of around 45 nm, particles with a length of 68 ± 6 nm (presumably tetramers and hexamers) and larger aggregates of 108 ± 19 nm are found. GFAP has an increased tendency to aggregate upon lowering of the pH. The aggregation state of desmin does not change in the pH range studied. The results are compared with previous results on vimentin.
Structure of three Kdn‐containing oligosaccharide‐alditols released from oviducal secretions of Ambystoma tigrinum: characterization of the carbohydrate sequence Fuc (α1–5) [Fuc (α1–4)] Kdn (α2—3/6)
Authors: Maes Emmanuel , Wieruszeski Jean-Michel , Plancke Yves , Strecker Gérard
Published: April 2003

Oligosaccharide‐alditols released by reductive β‐elimination from the egg jelly coat of Ambystoma tigrinum were analyzed by 1H NMR spectroscopy. As observed for five other amphibian species, these carbohydrate chains are highly species‐specific, and should support the species‐specificity of gamete interaction. The carbohydrate chains of Ambystoma tigrinum are characterized by the presence of a new type of sequence: Fuc (α1–5) [(Fuc (α1–4)] Kdn (α2–3/6).
Ligand‐induced perturbations in Urtica dioica agglutinin
Authors: Hom Kellie , Gochin Miriam , Peumans Willy J. , Shine Nancy
Published: April 2003

The binding of the trisaccharide, N,N′,N″‐triacetylchitotriose, to Urtica dioica agglutinin (UDA) was investigated using 1H NMR spectroscopy. UDA is a small antiviral plant lectin containing two homologous 43‐amino acid domains. Carbohydrate‐induced perturbations occur in one domain of UDA at trisaccharide concentrations below equimolar. Residues in the second domain are shifted at higher carbohydrate concentrations. This data confirms the presence of two binding sites of non‐identical affinities per UDA monomer. Qualitative analysis of the 2D NOESY spectra indicates that UDA contains two short stretches of antiparallel β‐sheet. The 1H resonance assignments for both antiparallel β‐sheet sequences have been completed and there is one β‐stretch per domain. A number of these β‐sheet residues are perturbed in the presence of carbohydrate.
Changes of cytoplasmic pH in frog nerve fibers during K+‐induced membrane depolarization
Authors: Valkina O.N. , Vergun O.V. , Turovetsky V.B. , Khodorov B.I.
Published: April 2003

Frog sciatic nerve and its thin bundles were loaded with fluorescein diacetate in order to monitor changes in cytoplasmic pH (pHi) caused by high K+ depolarization. Isosmotic substitution of external Na+ by K+ at pHo 7.3 led to a steady concentration‐dependent (20–120 mM K+) decrease in pHi. Elevation of pHo from 7.3 to 8.5 prevented or even reversed these pHi changes, indicating their strong dependence on transmembrane H+ fluxes. The depolarization‐induced intracellular acidification could not be prevented or decreased by any of the following treatments: removal of external Ca2+; application of the Cat2+ antagonists Ni2+ and Co2+; blockade of+ channels by TEA; addition to the external solution of Zn2+, a blocker of putative voltage‐sensitive H+ channels. By contrast, blockade of Na+ channels by 1–3 μM TTX prevented the effect of high K+ concentrations on pHi. It is concluded that the decrease in pHi induced by a prolonged membrane depolarization in frog nerve fibers is mainly due to an enhanced H+ influx through non‐inactivating Na+ channels.
Alterations in the internucleosomal DNA helical twist in chromatin of human erythroleukemia cells in vivo influences the chromatin higher‐order folding
Authors: Krajewski Wladyslaw A.
Published: April 2003

In the present study chloroquine diphosphate, a DNA intercalating drug, was used to alter the internucleosomal DNA helical twist in chromatin of living mammalian cells. The intercalative binding of chloroquine effectively unwinds the DNA double helix and its binding is restricted to nucleosomal linker regions without noticeable disruption of nucleosomes. The results presented here imply that the alterations in the rotation angle between the adjacent nucleosomes in chromatin of eukaryotic cells in vivo significantly influences the way the chain of nucleosomes folds in higher‐order chromatin structures, as evidenced by specific alterations in nuclease susceptibility of chromatin.