bluuebunny/crossref_metadata_2025 huggingface dataset:
Multivariate Resolution of Coeluted Peaks in Hyphenated Liquid Chromatography – Linear Sweep Voltammetry
Authors: Berbel Francisco , Kapoya Elisabeth , Díaz‐Cruz José Manuel , Ariño Cristina , Esteban Miquel , Tauler Romà
Published: April 2003

A novel application of Multivariate Curve Resolution with Alternating Least Squares (MCR‐ALS) method for the background correction and for the resolution and quantitation of coeluted analyte mixtures in liquid chromatography with voltammetric detection is presented. The selected voltammetric technique for analyte detection was Linear Sweep Voltammetry (LSV), which provides richer multivariate information than the more widespread employed univariate amperometric detection. Use of other voltammetric detection techniques was also attempted but they gave much poorer results because of instrumental and software limitations concerning data acquisition times. The method is tested in the resolution and quantitation of mixtures of pyrocatechol, ascorbic acid and epinephrine coeluting mixtures. In spite of the extremely large background current contributions observed using this voltammetric technique, MCR‐ALS was shown to be able to model this background contribution satisfactory as well as to resolve and give good quantitative estimations of these three analyte in their mixtures. The proposed approach is recommended for resolution and quantitation of complex coeluted mixtures using liquid chromatography with voltammetric detection and also for fast initial screening of optimal potential when amperometric detection is preferred.
Permselective Properties of Electropolymerized Guaiacol Derivatives
Authors: Milczarek Grzegorz , Ciszewski Aleksander
Published: April 2003

Guaiacol (2‐methoxyphenol) and its 5 derivatives such as 4‐allyl‐2‐methoxyphenol,2‐methoxy‐4‐propenylphenol, 2‐methoxy‐4‐propylphenol, 4‐hydroxy‐3‐methoxybenzylamine and 4‐chloro‐2‐methoxyphenol were oxidatively polymerized on platinum electrodes in 0.1 M NaOH solution. The polymer modified electrodes were then checked for their responses towards biologically important analytes such as hydrogen peroxide, ascorbic and uric acids, dopamine and acetaminophen under flow injection conditions. The effect of a monomer chosen on the permselective properties of the deposited film is thoroughly discussed. Feasibility of the application of these polymer modified electrodes in selective flow injection detection of hydrogen peroxide and dopamine is demonstrated.
Voltammetric Determination of Microparticles of Some Local Anesthetics and Antithusics Immobilized on the Graphite Electrode
Authors: Komorsky‐Lovrić Šebojka , Vukašinović Nevenka , Penovski Rahela
Published: April 2003

Solid microparticles of local anesthetics benzocaine, cinchocaine, lidocaine and procaine, and the antithusic codeine were mechanically immobilized on the surface of the paraffin impregnated graphite electrode and investigated by square‐wave and cyclic voltammetry in order to develop a method for their qualitative determination. The measurements were performed in the pH range between 1 and 9. The square‐wave frequency and amplitude were changed between 100 and 1000 Hz, and from 15 to 85 mV, respectively. The scan rate in cyclic voltammetry was 1 V/s.
Fabrication of a Sub‐Micrometer Electrode Array: Electrochemical Characterization and Mapping of an Electroactive Species by Confocal Raman Microspectroscopy
Authors: Szunerits Sabine , Garrigue Patrick , Bruneel Jean‐Luc , Servant Laurent , Sojic Neso
Published: April 2003

The fabrication of an ordered electrode array based on an etched optical fiber bundle is described. The high density sub‐micrometer electrode array is characterized electrochemically using cyclic voltammetry and geometrically via scanning electron microscopy. The observed steady‐state current indicates that individual diffusion layers do not overlap and that the electrodes are diffusively independent. Spatially resolved chemical information of the etched and insulating paint‐covered surface of the electrode array is obtained from confocal Raman microspectroscopy (CRM) experiments. Finally electroactive spots are probed using CRM through the different Raman spectra of the electroactive species of the redox couple Fe(CN)63−/Fe(CN)64−.
A Voltammetric Assay of Antioxidants and Inhibitors of Soybean Lipoxygenase
Authors: Pérusse Pascal , Leech Dónal
Published: April 2003

Antioxidant activity and/or the inhibition of lipoxygenases may contribute to the cell and tissue protective properties of flavonoids. Soybean lipoxygenase‐1 (LOX‐1), is a useful paradigm for lipoxygenases isolated from different sources, and can be used to devise assays of oxygenase inhibitors and antioxidants. Here we describe the voltammetric detection of methylene blue (MB) to assay for antioxidant and lipoxygenase inhibition activity. MB is formed by the catalytic action of hydroperoxide, produced by soybean lipoxygenase reaction on linoleic acid, on benzoyl‐leuco methylene blue (BLMB). Every compound which blocks either the enzymatic reaction, lipoxygenase inhibitors, or the oxidation of BLMB, antioxidants, can thus be detected using this method. The assay involves reaction for a period of one hour of linoleic acid, lipoxygenase, BLMB and inhibitor, followed by injection into a flow‐injection system and detection by square‐wave voltammetry of the methylene blue produced. The problem of irreproducibility induced by adsorption at the solid platinum working electrode is alleviated using the method of alternate injections of control and assay solutions. Assays of several known lipoxygenase inhibitors were undertaken. All of these inhibitors were also, however, shown to be antioxidants. Extension of the assay to the rapid evaluation of novel therapeutic antioxidants and lipoxygenase inhibitors is proposed.
Voltammetric Determination of Free and Total Sulfur Dioxide in Beer
Authors: Almeida P. J. , Rodrigues J. A. , Guido L. F. , Santos J. R. , Barros A. A. , Fogg A. G.
Published: April 2003

A voltammetric method for the determination of free and total sulfur dioxide in beer is described. First, volatile aldehydes (mainly acetaldehyde) are purged with nitrogen from a beer sample diluted in alkaline medium, collected in an appropriate electrolyte trapping solution and determined, after derivatization with hydrazine, by voltammetry using a hanging mercury drop electrode. Then, the remaining beer solution is strongly acidified and (total) sulfur dioxide is purged with nitrogen, collected in an appropriate electrolyte trapping solution and determined by voltammetry. The free sulfur dioxide concentration is calculated by difference between (total) sulfur dioxide and acetaldehyde concentrations. The proposed method has a relative standard deviation of about 2.1% and 4.4%, respectively for (total) sulfur dioxide and free sulfur dioxide concentrations normally found in beer, and results are in good agreement with those obtained by the p‐rosaniline reference method.
A Novel Catalytic Adsorptive Stripping Voltammetric Method of Iron Determination as Its 1,2‐Cyclohexanedione Dioxime Complex
Authors: Bobrowski Andrzej , Królicka Agnieszka
Published: April 2003

The sensitive catalytic adsorptive stripping voltammetric method for the determination of trace iron in the supporting electrolyte consisting of 0.1 M ammonia buffer, 0.05–0.15 mM 1,2‐cycloheksanedione dioxime and 0.14 M NaNO2 is presented. The method is based on adsorptive accumulation of an iron‐nioxime complex on a hanging mercury drop electrode, followed by a stripping voltammetric measurement of the catalytic reduction current of the adsorbed complex in the presence of sodium nitrite. The detection limit obtained for a 20 s accumulation time was 0.90 nM iron, the RDS was 3%, and the linearity range amounted from 3.6 to 107.4 nM of iron. Possible interferences from the coexisting ions and surface‐active substances were investigated.
Delivery of bioactive, gel‐isolated proteins into live cells
Authors: Taylor Jennifer E. , Fernandez‐Patron Carlos
Published: April 2003

The delivery of proteins into live cells is a promising strategy for the targeted modulation of protein‐protein interactions and the manipulation of specific cellular functions. Cellular delivery can be facilitated by complexing the protein of interest with carrier molecules. Recently, an amphipatic peptide was identified, Pep‐1 (KETWWETWWTE WSQPKKKRKV), which crosses the plasma membrane of many cell types to carry and deliver proteins as large as antibodies. Pep‐1 effectively delivers proteins in solution; but Pep‐1 is not suitable for delivering sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE) isolated proteins because Pep‐1 complexes with cargo proteins are destroyed by SDS. Here, we report cellular delivery of SDS‐PAGE‐isolated proteins, without causing cellular damage, by using a nonionic detergent, Triton X‐100, as carrier. To determine the specificity of our method, we separated antibodies against different intracellular targets by nonreducing SDS‐PAGE. Following electrophoresis, the antibody bands were detected by zinc‐imidazole reverse staining, excised, in‐gel refolded with Triton X‐100, and eluted in detergent‐free phosphate‐buffered saline. When overlaid on cultured NIH 3T3 cells, the antibodies penetrated the cells localizing to their corresponding intracellular targets. These results are proof‐of‐principle for the delivery of gel‐isolated bioactive proteins into cultured cells and suggest new ways for experimental protein therapy and for studying protein‐protein interactions using gel‐isolated protein.
Sol‐gel column technology for capillary isoelectric focusing of microorganisms and biopolymers with UV or fluorometric detection
Authors: Horká Marie , Planeta Josef , Růzička Filip , Šlais Karel
Published: April 2003

The sol‐gel surface modification is used for capillary isoelectric focusing of microorganisms and biopolymers. The coating strongly decreases the electroosmotic flow so that it enables the use of the short capillaries down to 100 mm in the separation length. The examples of capillary isoelectric focusing of the low‐molecular‐mass pI markers and mixed cultures of microbial populations of Escherichia coli, Candida albicans, Staphylococcus epidermidis, and Enteroccocus faecalis with UV detection are shown. It is possible to quantify bacterial cells according to their peak areas; the minimum detectable number of microbial cells was 5×102–1×103. The compatibility of sol‐gel capillaries with sensitive fluorometric detection of fluorescent pI markers together with fluorescein labeled proteins is demonstrated.
Size‐based separations of proteins by capillary electrophoresis using linear polyacrylamide as a sieving medium: Model studies and analysis of cider proteins
Authors: Gomis Domingo Blanco , Junco Sara , Expósito Yoana , Gutiérrez Dolores
Published: April 2003

Electrophoretic conditions to separate sodium dodecyl sulfate (SDS)‐protein complexes according to their relative molecular mass by capillary electrophoresis (CE) using linear polyacrylamide as a sieving matrix were examined. Five purified proteins with relative molecular masses between 14 400 and 66 200 Da were separated on a coated fused‐silica capillary with an internal diameter of 100 μm and an effective length of 24 cm (total length, 32.5 cm). Benzoic acid was added to the solution of purified proteins as internal standard; β‐mercaptoethanol was also added as reducing agent. The running buffer composition was 0.05 M tris(hydroxymethyl)aminomethane (Tris), 0.035 M aspartic acid, 0.1% m/v SDS, 4% m/v acrylamide, the resulting pH being 8.0. The applied voltage was 7 kV (reversed voltage polarity) in order to avoid high current intensities. Under optimized conditions, the five proteins were separated in less than 15 min, with a % relative standard deviation (RSD) between 0.2 and 0.4 for migration times in the same day. Good efficiency (values between 150 000 and 40 000 N/m) and resolution (values between 2 and 2.8) were obtained. The inverse of relative migration times was found to correlate with the logarithm of their relative molecular mass. Finally, cider proteins were analyzed and their relative molecular masses were determined. These results were compared with those obtained by SDS‐polyacrylamide gel electrophoresis (SDS‐PAGE).
Speciation of chromium (III) and chromium (VI) by capillary electrophoresis with contactless conductometric detection and dual opposite end injection
Authors: Kubáň Pavel , Kubáň Petr , Kubáň Vlastimil
Published: April 2003

A sensitive, rapid and inexpensive capillary electrophoretic method for the determination of Cr(III) and Cr(VI) species is presented. The method is based on the dual opposite end injection principle and contactless conductometric detection. The sample containing cationic and anionic species is injected into the opposite ends of the separation capillary and after the high voltage is applied, the analytes migrate towards the capillary center, where the cell of a contactless conductivity detector is placed. The method does not require any sample pretreatment, except dilution with deionized water. The separation of Cr(III), Cr(VI) and other common inorganic anions and cations is achieved in less than 4 min. The parameters of the separation electrolyte solution, such as pH and concentration of L‐histidine, were optimized. Best results were achieved with electrolyte solution consisting of 4.5 mM L‐histidine, adjusted to pH 3.40 with acetic acid. The detection limits achieved for Cr(III) and Cr(VI) were 10 and 39 μg·L–1, respectively. The repeatability of migration times and peak areas was better than 0.3% and 2.8%, respectively. The developed method was applied to the analyses of rinse water samples from the galvanic industry. The results for the determination of Cr(III) and Cr(VI) were in good agreement with the results obtained by certified differential spectrophotometric method using diphenylcarbazide (CN 83 0520‐40) and with the results for the total chromium concentrations determined by electrothermal atomic absorbance spectrometry (ET‐AAS) and inductively coupled plasma‐mass spectrometry (ICP‐MS).
Investigation of a capillary electrophoretic approach for direct quantification of apolipoprotein A‐I in serum
Authors: Lehmann Rainer , Friess Ulrich , Häring Hans‐Ulrich , Voelter Wolfgang , Liebich Hartmut , Beck Alexander
Published: April 2003

In the present study a rapid, reproducible and robust capillary electrophoresis (CE) procedure for the quantification of apolipoprotein A‐I (Apo A‐I) in serum without pretreatment has been developed (total run time, 11 min). The coefficients of variation (CV; n = 10) for the relative peak area are 1.8% at a concentration of 145 mg/dL and 1.6% at 196 mg/dL; and for the inter‐assay 8.9% at 161 mg/dL (10 consecutive days), i.e., similar to the CVs of a high‐throughput immunonephelometric routine assay. The CV for the migration time is 0.4% (n = 20). The robustness of the CE approach was tested in patient samples with hemolysis, hyperbilirubinemia and hyperlipidemia. A comparison of 99 Apo A‐I serum values with results of a fixed‐time immunonephelometric routine assay showed a positive constant bias of 60% (mean) for the immunonephelometric values, no deviation from linearity, but significant deviations in several samples. Investigations on interferences in the CE analyses gave no evidence that CE failed. Our study shows that CE is amenable to a fast analysis and a reproducible and reliable quantification of Apo A‐I level in sera of various clinical samples.
Proteome analysis of Saccharomyces cerevisiae under metal stress by two‐dimensional differential gel electrophoresis
Authors: Hu Yi , Wang Gang , Chen Grace Y. J. , Fu Xin , Yao Shao Q.
Published: April 2003

The defense mechanism by which cells combat metal stress remains poorly understood. By utilizing a newly developed technique – the differential gel electrophoresis (DIGE) – we evaluated the biological alterations of metal stress on Saccharomyces cerevisiae at its translational level. By simultaneously comparing the differential expression profiles of thousands of proteins as results of 15 different metal treatments, we were able to closely examine the response of a large number of proteins within the yeast proteome towards individual metals, as well as the response of the same proteins towards different metals. This, to our knowledge, is the first case which demonstrates the potential of DIGE as a high‐throughput tool for large‐scale proteome analysis. From our studies, where yeast cells were exhaustively treated with exogenous metals, 20–30% of all proteins detected showed statistically significant changes. According to different effects (up‐/downregulation) of protein expression levels observed, we were able to tentatively divide the 15 metals into three groups. By mass spectrometric analysis, more than 50 protein spots were positively identified, both quantitatively and qualitatively. One of the proteins was identified to be Cu/Zn superoxide dismutase (SOD1), and its expression levels as a result of 15 different metal treatments was further examined in greater details. Significant changes in SOD1 expression were observed throughout all 15 DIGE gels.
Representation of radiation damping by fractional time derivatives
Authors: Ruge P. , Trinks C.
Published: April 2003

When modelling unbounded domains, formulation of a matrix‐valued force–displacement relationship which can take radiation damping into account is of major importance. In this paper, a method to describe the dynamic stiffness by a system of fractional differential equations in the time‐domain is presented. Here, a doubly asymptotic rational approximation of the low‐frequency force–displacement relationship is used, whereas a direct interpretation of the asymptotic part as a fractional derivative is possible. The numerical solution of the corresponding system of fractional differential equations is demonstrated using the infinite beam on elastic foundation as an example. Copyright © 2003 John Wiley & Sons, Ltd.
Bisubstrate Inhibitors for the Enzyme Catechol O‐Methyltransferase (COMT): Dramatic Effects of Ribose Modifications on Binding Affinity and Binding Mode
Authors: Lerner Christian , Siegrist Romain , Schweizer Eliane , Diederich François , Gramlich Volker , Jakob‐Roetne Roland , Zürcher Gerhard , Borroni Edilio
Published: April 2003

Inhibition of the enzyme catechol O‐methyltransferase (COMT) is of significant interest in the therapy of Parkinson's disease. Described herein are structural analogs of the potent bisubstrate inhibitor (−)‐1 (IC50=9 nM; Table 1) for COMT, with target modifications of the central ribose moiety. Their synthesis involves, as key intermediates, adenosine derivatives, which are transformed to the potential bisubstrate inhibitors by a similar sequence of six steps (Schemes 1–4). The compounds were submitted to an enzymatic assay for determination of their in vitro inhibitory activity against COMT, and the inhibition mechanism with respect to the binding side of the cofactor S‐adenosylmethionine (SAM) was analyzed by kinetics measurements (Fig. 3). Both binding affinity and binding mode were exceedingly sensitive towards modifications of the ribose moiety (Table 1). Removal of the 2′‐OH group upon changing from (−)‐1 to (−)‐2 (IC50=28 μM) led to a reduction in binding affinity by more than three orders of magnitude. At the same time, competitive inhibition kinetics with respect to the SAM binding site was maintained, thereby supporting a bisubstrate binding mode. Unlike (−)‐2, the dideoxyribose inhibitor (−)‐3 (IC50=3 μM) showed a mixed and the cyclopentane derivative (+)‐4 (IC50=1 μM) an uncompetitive inhibition mechanism with respect to the SAM binding site. In the complex of the latter, the adenine‐substituted cyclopentane ring orients most probably towards the surface of the enzyme into the surrounding solution. The enantiomeric compounds (−)‐5 (IC50=43 μM) and (+)‐5 (IC50=141 μM), wherein the ribose had been replaced by a pyrrolidine ring, showed only low binding affinity.
7,8‐(Dichloromethano)homo[70]fullerene, an Unusual, but Unexceptional, Methanoannulene
Authors: Kiely Andrew F. , Meier Mark S. , Patrick Brian O. , Selegue John P. , Pratt Brock Carolyn
Published: April 2003

The crystal structure of 7,8‐(dichloromethano)homo[70]fullerene shows that addition of the dichlorocarbene (:CCl2) to C70 gives a surprisingly normal methano‐bridged [9]annulene. The structural changes caused by the addition are highly localized; the C(7)C(8) distance lengthens by 0.705(2) Å but no other distance changes by more than 0.022(3) Å. Bond angles within the [9]annulene increase by as much as 7.8(1)°, but changes outside the C9 ring are much smaller. The nearly ellipsoidal molecules form hexagonally close‐packed layers that interact in pairs through short Cl⋅⋅⋅C, and possibly short Cl⋅⋅⋅Cl and C⋅⋅⋅C, interactions.
Promiscuity in Antibody Catalysis: Esterolytic Activity of the Decarboxylase 21D8
Authors: Backes Alexander C. , Hotta Kinya , Hilvert Donald
Published: April 2003

The high structural similarity of decarboxylase antibody 21D8 and esterase antibody 48G7 suggests that 21D8 might also possess hydrolytic activity. Kinetic investigations show that 21D8 does promote the selective hydrolysis of methyl 4‐nitrophenyl carbonate and sodium 4‐(acetoxy)benzenesulfonate with catalytic proficiencies (kcat/Km)/kun of ca. 105 M−1. The ability of 21D8 to accelerate a reaction for which it was not developed suggests that certain antibody scaffolds are intrinsically predisposed toward catalysis, a property that can be enhanced and refined during affinity maturation in response to a transition‐state analog. At the same time, however, the restricted structural diversity of the immune system may ultimately limit the catalytic efficiency that can be achieved.
Crystal Packing: An Examination of the Packing of Molecules Approximately Isosteric with 4,5‐Dichlorophthalic Anhydride
Authors: Britton Doyle , Noland Wayland E. , Pinnow Matthew J. , Young Jr. Victor G.
Published: April 2003

The crystal structures of five 5,6‐disubstituted benzofurazan 1‐oxides are presented and compared with five previously reported structures: three polymorphs of 5,6‐dichlorobenzofurazan 1‐oxide plus 4,5‐dichloro‐ and 4,5‐dibromophthalic anhydride. All but one of these compounds pack with similar two‐dimensional layers. The benzofurazan oxides all show disorder about a crystallographic twofold or pseudo‐twofold axis. In addition, six complexes of phthalic anhydride and benzofurazan oxides are reported. With the packing in the complexes principally directed by the π complexing, the disorder, invariably found in the uncomplexed benzofurazan oxides, is diminished, and, in two cases, eliminated.
Structural Basis for Recognition of Guanosine by a Synthetic Tricyclic Cytosine Analogue: Guanidinium G‐Clamp
Authors: Wilds Christopher J. , Maier Martin A. , Manoharan Muthiah , Egli Martin
Published: April 2003

An oligonucleotide analogue containing a novel heterocyclic analogue, the guanidinium G‐clamp, was designed to allow formation of five H‐bonds to guanosine. The guanidinium group was introduced postsynthetically by treatment of the deprotected oligonucleotide containing a free amino group with a solution of 1H‐pyrazole‐1‐carboxamidine and purified by a combination of size‐exclusion chromatography and reversed‐phase HPLC. A single incorporation of this modification into an oligodeoxynucleotide sequence was found to increase duplex stability by 13° and 16° per modification to RNA and DNA, respectively. Crystals of a self‐complementary decamer sequence containing this modification were grown and diffracted to 1‐Å resolution. The structure was solved by molecular replacement and revealed that the modification forms additional H‐bonds to O(6) and N(7) of guanosine through the amino and imino N‐atoms, respectively. The origins of enhanced duplex stability are also attributed to increased stacking interactions mediated by the phenoxazine moiety of the G‐clamp and formation of H‐bond networks between the positively charged guanidinium group, H2O molecules, and negatively charged O‐atoms from phosphates on the adjacent strand.
Predicting disturbed parental awareness in mothers with a newborn infant: test of a theoretical model
Authors: Grietens Hans , Hellinckx Walter
Published: April 2003

Parental awareness refers to parents' perceptions and making sense out of children's responses and behaviours. This study examined a theoretical model on the determinants of disturbed parental awareness, with a central place given to Belsky's buffer hypothesis. Maternal characteristics were hypothesized to have direct effects on parental awareness, whereas effects of negative childhood experiences and low levels of social support were regarded as being mediated by maternal characteristics. The model was examined in a community sample of 101 mothers from different socioeconomic backgrounds with a zero‐to‐three infant. Social nurses providing home visits reported on parental awareness, childhood experiences, social support, and maternal characteristics. Results supported a modified model that added a direct pathway between childhood experiences and parental awareness, supporting the intergenerational transmission hypothesis. Copyright © 2002 John Wiley & Sons, Ltd.
Maternal speech style with prelinguistic twin infants
Authors: Butler Sue , McMahon Catherine , Ungerer Judy A.
Published: April 2003

The mother–infant communicative speech of a group of mothers of 4‐month‐old first‐born twin infants was compared to the speech of a group of mothers of first‐born singleton infants. Maternal groups were matched on age, education level, mother–infant attachment status and infant gender, and maternal depression was assessed as a control variable. Maternal speech was coded for focus, content, complexity and syntax of mothers' utterances. The findings of earlier studies with toddler age twins, that maternal speech style was more directive and less infant‐focused, were replicated in this prelinguistic period of infancy. Compared to mothers of singletons, mothers of twins used less infant‐focused speech, were less responsive to their infants' cues, and attributed less agency to their infants. Mothers of twins also used fewer questions and requests but did not differ from mothers of singletons in their use of negatives and imperatives. These early differences in the language learning environments of twin and singleton infants may be due to the reduced opportunities that mothers of twins have to establish dyadic communicative routines with their infants and to familiarize themselves with their infants as interactive partners, and may have implications for the early language development of twins. Copyright © 2002 John Wiley & Sons, Ltd.
Chemoenzymatic Synthesis of Fucose‐ or Rhamnose‐Branched Polymer
Authors: Raku Takao , Tokiwa Yutaka
Published: April 2003

6‐Deoxy sugars having only secondary alcohols, namely, D‐fucose, L‐fucose, and L‐rhamnose, were regioselectively esterified with divinyl adipate by enzymes. The compounds 2‐O‐vinyl adipolyl D‐fucose and 2‐O‐vinyl adipolyl L‐fucose were effectively produced in dimethylformamide by protease from Bacillus subtilis and Streptomyces griseus. Furthermore, 4‐O‐vinyl adipolyl L‐rhamnose was effectively produced in pyridine by lipase from Pseudomonas sp. Each polymerizable sugar ester was polymerized by 1,1′‐azoisobutyronitrile to give polymers having a number average molecular weight of 5 000–14 000.

Part of the chemoenzymatic synthesis of poly(6‐deoxy sugars).

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Part of the chemoenzymatic synthesis of poly(6‐deoxy sugars).
Complexation reaction of poly(L‐glutamic acid) with Cu ions and the effect of helix‐coil transition of the polymer chain
Authors: Koide Mikio , Tsuchida Eishun , Kurimura Yoshimi
Published: April 2003

The complexation reaction of poly(L‐glutamic acid) (1), with Cu ions in aqueous solution was studied by pH titration, spectroscopy, circular dichroism measurements and solution viscosity. The adsorption of Cu ions depended on the secondary structure of 1; 1 adsorbed Cu ions when its degree of neutralization was higher than 0,6. Thus, this phenomenon was attributed to the helix‐coil transition of 1. It was cleared that the helical structure was retained because of chelating between Cu ions and carboxyl groups of the side chain of 1. The formation of the Cu/1 complex was compared with that of the Cu/poly(acrylic acid) complex (2).
13C NMR study on the mechanism of stereoselective polymerization of methyloxirane catalyzed by a model compound for enantiomorphic catalysts
Authors: Hagiwara Tokio , Ishimori Michihiro , Tsuruta Teiji
Published: April 2003

The reaction of [Zn(OCH3)2·(C2H5ZnOCH3)6] (1) with methyloxirane was investigated by 13C NMR spectroscopy. Complex 1 was assumed to be a model compound for enantiomorphic catalyst sites in the stereoselective polymerization of methyloxirane by organozinc catalyst. Complex 1 was found to retain its structural feature, determined by X‐ray diffraction, even after the propagation reaction had proceeded. Based on 13C NMR studies of the polymerization reaction in terms of spin‐lattice relaxation and signal intensity analysis, the mechanism of the stereoselective polymerization of methyloxirane by the chiral catalyst sites was discussed at molecular level in reference to the enantiomorphic structure of complex 1.
Mechanischer Scherabbau von Polymeren in Lösung mittels turbulenter Strömung, 2. Die Abhängigkeit der Abbaugeschwindigkeit von der Polymergesamtkonzentration in guten Lösungsmitteln
Authors: Müller Hans Georg , Klein Joachim , Rottloff Adelheid
Published: April 2003

Mechanical shear degradation of poly(decyl methacrylate), (viscosity average molecular weight in tetrahydrofuran M̄η = 1,3·106, M̄w/M̄n = 5) in the thermodynamically good solvent tetrahydrofuran has been studied in turbulent flow through a capillary as a function of polymer concentration in the range from 0,22 to 8,9 g/100 cm3. Due to turbulent flow conditions the shear stress, shear rate and shear energy proved to be the same for all concentrations and remained constant during degradation, giving a general insight into mechanism of degradation. The rate of degradation has been followed using molecular weight distribution curves obtained by gel permeation chromatography. The reaction was found to be of first order. Rate constants determined for molecular weights from 3,2–9,5·106 decreased with increasing concentration following a law of the type ki = (K + b·c)−1, K and b being constants for each molecular weight. Hydrodynamic volumes of polymer molecules have been calculated according to models of Rudin as function of molecular weight and concentration. It can be shown that rate constants of degradation and calculated hydrodynamic volumes are proportional for the whole range of molecular weight and concentrations up to 3,6 g/100 cm3. There is also a rather good proportionality between these rate constants and the volumes of polymer coils predicted by de Gennes. This result is an additional confirmation of the concept that hydrodynamic volume governs shear degradation of polymer solutions. Additional experiments show that this type of concentration dependence is also to be found for other polymers in other solvents.
Investigations on the Film‐Formation Process of Latex Dispersions by Solid‐State NMR Spectroscopy
Authors: Rottstegge Jörg , Traub Bernd , Wilhelm Manfred , Landfester Katharina , Heldmann Carsten , Spiess Hans Wolfgang
Published: April 2003

Various latex dispersions based on poly(vinyl acetate) stabilised by different surfactants and polyelectrolytes were investigated by NMR methods to elucidate the macroscopic and molecular film‐formation process of these latex dispersions. Macroscopically, theinhomogeneousdrying in the film‐formation process was investigated by NMR‐imaging techniques. Here the influence of different amounts of surfactant on the homogeneity of the drying process was monitored. The molecular film‐formation process was investigated by1H,2H, and13C solid‐state NMR spectroscopy. For these bulk measurements, films of latex dispersions werehomogeneouslydried to different defined solid contents. Spectroscopic analysis allows the investigation of the drying process of the water at different solid contents with a pronounced influence on the polymer/water interface and the latex particle core. The film‐formation process is correlated to the drying mechanism of different types of water within the film. External water, water at ionic and non‐ionic groups at surfactants in the polymer/water interface, and water in the swollen and mobilised polymer, could be distinguished during the drying process.

Latex domains as selected by solid‐state NMR spectroscopy as a function of temperature.

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Latex domains as selected by solid‐state NMR spectroscopy as a function of temperature.
Viscoelastic Properties of Polystyrene Nanocomposites Based on Layered Silicates
Authors: Meincke Olaf , Hoffmann Botho , Dietrich Christoph , Friedrich Christian
Published: April 2003

Nanocomposites based on polystyrene (PS) and organophilic layered silicates (organoclays) were prepared and characterised with respect to their morphological and rheological properties. The organoclays were obtained by means of ion exchange of clay with protonated, amine‐terminated PS. Two different exchange agents – a high (Mw = 5 800 g/mol) molecular mass amine functionalised PS, and 2‐phenylethylamine – were used to study the influence of their molecular weight on morphological and rheological properties of corresponding composites. Wide‐angle X‐ray scattering measurements show a significant increase in the interlayer spacing upon the ion exchange. Composites of organoclay prepared from the high molecular mass amine‐terminated PS and PS‐matrix polymer reveal a fine and stable dispersion of exfoliated silicate layers in the PS matrix if the compounding time in a conical twin screw extruder exceeds 180 s at a temperature of 200 °C. This composite, i.e. nanocomposite, shows unique elastic properties which can be understood quantitatively if one assumes that above a characteristic concentration of about 1 vol.‐% percolating strands of platelets are present in the material. Composites of PS and organoclay prepared from 2‐phenylethylamine did not exfoliate and consequently exhibited the rheological behaviour of a conventional composite. Qualitatively all morphological and rheological features of the PS nanocomposite can be entirely understood if one considers this material as a mixture of hairy platelets dispersed in an entangled PS matrix.

“Hairy platelets” model for exfoliation of layered silicates.

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“Hairy platelets” model for exfoliation of layered silicates.
Clathrate Phases of Styrene/p‐Methylstyrene co‐Syndiotactic Copolymers
Authors: Loffredo Fausta , Pranzo Annamaria , Venditto Vincenzo , Longo Pasquale , Guerra Gaetano
Published: April 2003

The possible formation of clathrate phases with several different guest molecules for co‐syndiotactic random copolymers of styrene and p‐methylstyrene has been investigated. In the presence of suitable guests, like carbon disulfide and tetrahydrofuran, clathrate phases are stable for the entire copolymer composition range. However, discontinuous changes between clathrates structurally similar to those observed for syndiotactic polystyrene and syndiotactic poly(p‐methylstyrene) have been observed by wide‐angle X‐ray diffraction and differential scanning calorimetry. Wide copolymer composition ranges of stability have been observed for carbon disulfide/syndiotactic polystyrene and for tetrahydrofuran/syndiotactic poly(p‐methylstyrene) clathrates. A phase diagram including clathrate and crystalline forms of this copolymer system has been presented.

Schematic presentation of along the chain (c axis) projection of packing of the clathrate form of syndiotactic polystyrene including carbon disulfide.

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Schematic presentation of along the chain (c axis) projection of packing of the clathrate form of syndiotactic polystyrene including carbon disulfide.
A method of estimating the parameters in the Mark‐Houwink equation from molecular weight and second virial coefficient
Authors: Kawai Tōro , Kamide Kenji
Published: April 2003

A new method has been proposed for estimating the parameters Km and a in the Mark‐Houwink equation [η] = KmM̄va from the measurements of molecular weight and second virial coefficient for a single polymer sample. Although the treatment has been based upon existing theories, the partly draining effect has been taken into account as well as the excluded volume effect. Only one sample need be used, and thus the usual more laborious method is unnecessary. General applicability of our method has been shown by several examples cited from published data.
Urea‐induced contraction–relaxation of rat tail tendons
Authors: Elden Harry R. , Cassac Betty
Published: April 2003

A contraction and relaxation of rat tail tensons that can be induced by aqueous urea solutions is described in this report. Studies with 2–10M urea at pH 7.0 and 37°C. showed that the length–time curves could be divided into five periods: (1) lag period, (2) contraction, (3) point of maximum contraction, (4) relaxation, and finally (5) rupture. An empirical analysis of the rate showed that (dL/dt)c, the initial velocity of contraction. (dL/dt)r, the terminal velocity of relaxation, and dL/dt, the velocity at any time (t), could be related with a specific rate constant, Kcr, by log [dL/dt − (dL/dt)r] = log [(dL/dt)c − (dL/dt)r] − Kcrt. (dL/dt)c was related linearly (positive slope) with Kcr whereas (dL/dt)r was independent of (dL/dt)c and Kcr. The rate constant Kcr obeyed the usual Arrhenius temperature equation on the basis of linearity between log Kcr and 1/T. Dilute solutions (2M) required a long period (tB) before rupture occured and no change in length ΔLmax/L0 was observed. Concentrated solutions (10M) had much shorter tB and elevated ΔLmax/L0. At a fixed concentration of urea tB and ΔLmax/L0 were dependent upon tendon size (W0 = area × density). Induction of the contraction–relaxation process appears to be due to melting of crystalline regions in the collagenmucopolysaccharides structure of the tendon.
Nuclear magnetic relaxation in polymer melts and solutions
Authors: McCall David W. , Douglass Dean C. , Anderson Ernest W.
Published: April 2003

Nuclear magnetic relaxation times have been studied in some polymer liquids and solutions. The nonexponential decay of the transverse magnetization has been ascribed to the distribution of molecular weights. The use of such measurements as a means of determining average molecular weights and distributions is discussed. A preliminary application of this use is made for polyethylene. The implications of nuclear magnetic relaxation measurements are discussed in terms of molecular motional processes of the polymer chains.
Sound velocity and young's modulus in polyethylene
Authors: Davidse P. D. , Waterman H. I. , Westerdijk J. B.
Published: April 2003

The sound velocity was measured in bars for a number of low‐ and high‐density polyethylene samples. The longitudinal oscillations in the bar were generated electrodynamically. It was observed that the sound velocity decreased somewhat with length. Therefore all sound velocity measurements were made in bars with the same length and diameter. After each measurement the density was determined also. It was observed that a linear relationship exists between sound velocity and density. The degree of polymerization has no direct influence on the sound velocity. Young's modulus obtained from sound velocity measurements was represented as a function of density also. Young's modulus obtained from sound velocity measurments proved to be about three times larger than values obtained from bending and tensile tests. The very small deformations involved in sound velocity measurements and the elimination of time‐dependent viscoelastic effects because of the oscillations are mentioned as the most likely reasons for this.
Functionalizing Inorganic Solids: Towards Organic–Inorganic Nanostructured Materials for Intelligent and Bioinspired Systems
Authors: Ruiz‐Hitzky Eduardo
Published: April 2003

The design, preparation, and properties of organic–inorganic hybrid compounds are described and discussed with respect to their potential
uses as intelligent and bioinspired materials. Several synthesis strategies based on intercalation in 2D solids, the grafting of organic groups onto
silica and silicates, and the self‐assembly of organo‐silica materials are presented, focusing on the soft procedures that are used to
modify the functionality of the inorganic substrates. The combination of both organic and inorganic moieties at the nanometer level forms the basis for
preparing multifunctional solids that are provided with specific functions in response to different types of stimuli. In some cases these resemble
materials that are found in biological systems. Examples include organic–inorganic membranes that are based on intercalated macrocyclic compounds
and bi‐layer vesicles that consist of alkyl long‐chains arranged either in the confined region of layered silicates or as
self‐organized organo‐silica micelles. The role of certain hybrid materials such as membranes provides a different approach to the
development of artificial liposomes and other mimetic systems that have an organic–inorganic composition and nanostructural organization. Their
potential uses for DDS or DNA‐dense phases are also discussed and novel alternatives to bioinspired systems development are proposed. © 2003
The Japan Chemical Journal Forum and Wiley Periodicals, Inc., Chem Rec 3: 88–100; 2003: Published online in Wiley InterScience
(www.interscience.wiley.com) DOI 10.1002/tcr.10054
Oxidized low‐density lipoprotein is cytotoxic to human monocyte‐macrophages: protection with lipophilic antioxidants
Authors: Marchant Christine E. , Law Nadine S. , van der Veen Carina , Hardwick Simon J. , Carpenter Keri L.H. , Mitchinson Malcolm J.
Published: April 2003

Human monocyte‐macrophages were incubated for 24 h with low‐density lipoprotein (LDL) which had been previously oxidized for varying periods up to 24 h with copper ions, in the presence or absence of dl‐α‐tocopherol or probucol. The release of radioactivity from cells preloaded with tritiated adenine was used as an assay of toxicity. Toxicity of oxidized LDL increased with duration of copper oxidation and with increasing evidence of lipid oxidation, measured by assay of thiobarbituric acid‐reactive substances and by gas chromatography. Oxidation and toxicity were inhibited by dl‐α‐tocopherol (200 μM) and probucol (50 μM).
A mitochondrial elongation factor‐like protein is over‐expressed in tumours and differentially expressed in normal tissues
Authors: Wells Jeremy , Henkler Frank , Leversha Margaret , Koshy Rajen
Published: April 2003

The tissue‐specific expression of an antigen (P43) ubiquitously expressed at high levels in a variety of tumours of human and animal origin was investigated using a monoclonal antibody to P43. Whereas low amounts of P43 are expressed in the spleen, skeletal muscle and pancreas, P43 is abundantly produced in the liver and in other tissues such as the kidney, heart and brain which have high levels of oxidative metabolism. Interestingly, a related protein of higher molecular weight is abundantly expressed in the lung and in amounts which were higher than those observed with other tissues. The human cDNA for P43 was isolated from a human liver cDNA library and mapped to chromosome 16 between p11.2 and 12 and also to a position near the centromere on the long arm of chromosome 17. The deduced amino acid sequence of P43 is remarkably similar to that of E. coli EF‐Tu and the mitochondrial EF‐Tu of S. cerevisiae with the structurally and functionally important amino acids of EF‐Tu being completely conserved in P43. A comparison of the distribution of P43 and a mitochondrial protein Hsp 60 among different cellular fractions indicated a likely mitochondrial localisation for P43. Taken together these results suggest that P43 is a human mitochondrial elongation factor.
Antibody characterisation of two distinct conformations of the chaperonin‐containing TCP‐1 from mouse testis
Authors: Hynes Gillian , Kubota Hiroshi , Willison Keith R.
Published: April 2003

We describe a panel of antibodies specific to individual subunits of the chaperonin‐containing TCP‐1 (CCT) and one antibody that reacts with all the subunits of CCT. Immunoblot analysis of CCT purified from mouse testis suggests that the testis‐specific subunit, S6, may be related to CCTζ and that a co‐purifying 63 kDa protein may be a novel subunit of CCT. Using these antibodies in the analysis of CCT subjected to non‐denaturing IEF we observed the resolution of two distinct conformations of CCT, which differ in their susceptibility to proteolysis and in the number of associated polypeptides.
Identification of two cell cycle regulated genes affecting the β1,3‐glucan content of cell walls in Saccharomyces cerevisiae
Authors: Ram A.F.J. , Brekelmans S.S.C. , Oehlen L.J.W.M. , Klis F.M.
Published: April 2003

The Calcofluor white‐hypersensitive mutants cwh52 and cwh53 are severely reduced in β1,3‐glucan. CWH52 was equivalent to GAS1. CWH53 represented a new gene, located on the right arm of chromosone XII, and predicted to encode a 215 kDa protein with multiple transmembrane domains. The transcription of CWH53 was cell cycle‐dependent and, similar to GAS1/CWH52, increased in late G1, indicating that the formation of β‐glucan is cell cycle‐regulated. Further, in some mutant alleles of both gas1/cwh52 and cwh53 lethal concentrations of Calcofluor induced growth arrest at a specific phase of the cell cycle.
Activation of an Asp‐124→Asn mutant of haloalkane dehalogenase by hydrolytic deamidation of asparagine
Authors: Pries Frens , Kingma Jaap , Janssen Dick B.
Published: April 2003

Haloalkane dehalogenase hydrolyses various 1‐halo‐n‐alkanes to the corresponding alcohols by covalent catalysis with formation of an alkyl‐enzyme intermediate. The carboxylate function of the nucleophilic aspartate (Asp‐124) that displaces the halogen during formation of the intermediate was changed to an amide by site‐directed mutagenesis (Asp‐124→Asn). Activity measurements and analysis of peptides containing the nucleophilic residue showed that the mutant enzyme was inactive, but that the activity increased by rapid deamidation of the asparagine residue, yielding wild type enzyme. There was no indication for isoaspartate formation during this process. The results suggest that a water molecule that is located close to the carboxyl function of Asp‐124 in the X‐ray structure is highly reactive and is responsible for the observed deamidation.
The second zinc atom in the matrix metalloproteinase catalytic domain is absent in the full‐length enzymes: a possible role for the C‐terminal domain
Authors: Willenbrock Frances , Murphy Gillian , Phillips Ian R. , Brocklehurst Keith
Published: April 2003

Domain deletion mutants of the matrix metalloproteinases consisting of the catalytic domain only contain two zinc atoms per molecule. One is essential for catalysis, while the other may fulfil a structural role. We have analysed the zinc contents of both the full‐length and the truncated mutants of prostromelysin‐1 and progelatinase A and report that the second zinc atom is not present in the full‐length form of the proenzymes. Thus it seems likely that the role proposed for this zinc atom in maintaining the structure of the enzyme catalytic domain is performed by the C‐terminal domain in the full‐length enzyme.
The termini of a new citrus viroid contain duplications of the central conserved regions from two viroid groups
Authors: Stasys Robert A. , Dry Ian B. , Ali Rezaian M.
Published: April 2003

A citrus viroid associated with dwarfing, CVdIIIA, has been sequenced and its 294 nucleotide residues can be arranged to form the typical rod‐like secondary structure of other viroids with 71% of nucleotides base‐paired. CVdIIIA has greatest sequence similarity with apple scar skin viroid (ASSVd; 69%) and has the central sequence which is conserved in the ASSVd group. CVdIIIA is the smallest member of the ASSVd group but contains the terminal conserved region shared by all viroids over 300 nucleotides. The two ends of CVdIIIA are highly unusual in that each end appears to be derived from the conserved central core region of a different viroid group.