bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis of Symmetrical 1, 5‐Bisacyloxyanthraquinone Derivatives and Their Dual Activity of Cytotoxicity and Lipid Peroxidation
Authors: Huang Hsu‐Shan , Chiu Hui‐Fen , Chiou Jeng‐Fong , Yeh Pen‐Fong , Tao Chi‐Wei , Jeng Wei‐Ren
Published: December 2002

Symmetrical bis‐substituted anthraquinones were successfully prepared and demonstrated potent cytotoxicity against the growth of suspended murine and human tumors, i.e. rat glioma C6 cells and human hepatomaG2 cells.We report here a convenient synthetic pathway that leads to symmetrically substituted 1, 5‐bisacyloxyanthraquinone derivatives. Acylation of the hydroxyl group of 1, 5‐dihydroxyanthraquinone with the appropriate acyl chlorides in the presence of pyridine or sodium hydride, respectively, furnished this structural class of anthraquinones. The bis(butyryloxy) analog 2b, bis(2‐chlorobenzoyl) analog 2f, and bisphenylpropionyloxy analog 2n exhibit potent cytotoxicity in inhibition of human hep G2 cell growth in culture, as determined by using XTT colorimetric assay, while their antiproliferative activity is markedly enhanced and is comparable to that of the anticancer agentmitoxantrone. In addition, redox properties of the compounds for the inhibition of lipid peroxidation in model membraneswere determined.Compounds 2n also exhibited stronger antioxidant activity than ascorbic acid, (+)‐α‐tocopherol, and anthrarufin. Biological evaluation and SAR studies of these symmetrical anthraquinones have been performed and the results are discussed.
Crown Ethers as Ancillary Ligands in the Assembly of Silver(I) Aggregates Containing Embedded Acetylenediide
Authors: Wang Quan‐Ming , Mak Thomas C. W.
Published: December 2002

Five silver(I) double salts containing embedded acetylenediide, [Ag([12]crown‐4)2][Ag10(C2)(CF3CO2)9([12]crown‐4)2(H2O)3]⋅H2O (2), [Ag2C2⋅5 AgCF3CO2⋅(benzo[15]crown‐5)⋅2 H2O]⋅0.5 H2O (3), [Ag4([18]crown‐6)4(H2O)3][Ag18(C2)3(CF3CO2)16(H2O)2.5]⋅2.5 H2O (4), [Ag2C2⋅6 AgC2F5CO2⋅2([15]crown‐5)]2 (5), and [(Ag2C2)2⋅(AgC2F5CO2)9⋅([18]crown‐6)2⋅(H2O)3.5]⋅H2O (6), have been isolated by varying the types of crown ethers and anions employed. Single‐crystal X‐ray analysis has shown that complex 2 is composed of winding anionic chains with sandwiched [Ag([12]crown‐4)2]+ ions accommodated in the concave cavities between them. In 3, silver(I) double cages each sandwiched by a couple of benzo[15]crown‐5 ligands are linked by {Ag2(CF3CO2)2} bridges to form a one‐dimensional structure. For 4, an anionic silver column is generated through fusion of two kinds of silver polyhedra (triangulated dodecahedron and bicapped trigonal antiprism), and the charge balance is provided by aqua‐ligated [Ag([18]crown‐6)]+ ions. Complex 5 is a centrosymmetric hexadecanuclear supermolecule composed of two [(η5‐[15]crown‐5)2(C2@Ag7)(μ‐C2F5CO2)5] moieties connected through a {Ag2(C2F5CO2)2} bridge. Compound 6 is a discrete supermolecule containing an asymmetric (C2)2@Ag13 cluster core capped by two [18]crown‐6 ligands in μ3‐η5 and μ4‐η6 ligation modes.
A Fluorescent Sensor for 2,3‐Bisphosphoglycerate Using a Europium Tetra‐N‐oxide Bis‐bipyridine Complex for Both Binding and Signaling Purposes
Authors: Best Michael D. , Anslyn Eric V.
Published: December 2002

Host 1 was designed and synthesized as a fluorescent sensor for 2,3‐bisphosphoglycerate (BPG, 3). The design features a tris‐functionalized triethylbenzene core to preorganize binding groups. The three cationic moieties, a tetra‐N‐oxide bipyridine–europium complex and two ammonium groups, were included to complement the three anionic functionalities on the guest. Beyond acting as a binding site, the europium complex was used to signal binding of the guest through modification of the charge transfer emission. A 1:1 complex with BPG was determined in 50 % methanol/acetonitrile with a Ka of 6.7×105 mol−1 by monitoring the reduction of the fluorescence signal upon guest addition. In the titration of related glycolytic intermediates lacking a second phosphate (4–6) into host 1, 2:1 host to guest binding was observed. Similarly, control compound 2, which lacks the ammonium groups, binds BPG and 4–6 in a 2:1 fashion. Also, phenylphosphate 7 binds to host 1 in a 1:1 stoichiometry with a Ka over three times less than 3.
Cover Picture: Chem. Eur. J. 1/2003
Authors: Orgueira Hernán A. , Bartolozzi Alessandra , Schell Peter , Litjens Remy E. J. N. , Palmacci Emma R. , Seeberger Peter H.
Published: December 2002

The cover picture shows schematically a general, modular strategy for the first completely stereoselective synthesis of defined heparin oligosaccharides. Heparin is currently used as an anticoagulant to prevent the formation of thrombi. A developing thrombus is depicted as background. Di‐ and trisaccharide modules were derived from six monosaccharide building blocks in a fully selective fashion by placing a conformational constraint on uronic acid glycosyl acceptors. A new concept for stereochemical control of α‐glucosamine glycoside formation was utilized. Locking the conformation of the glucuronic acid acceptor allowed for completely selective preparation of the desired cis‐glycosides. This innovation greatly simplified the key step in the preparation of disaccharide building blocks. Combination of disaccharide modules to form trans‐uronic acid linkages proved also completely selective by virtue of C2 participating groups. Coupling reactions between disaccharide modules exhibited sequence dependence. Elaboration of disaccharide building blocks to trisaccharide modules allowed for stereoselective access to oligosaccharides as demonstrated on the example of a hexasaccharide. Final deprotection and sulfation yielded the fully synthetic heparin oligosaccharides. A detailed description of this study is reported by P. H. Seeberger et al. on p. 140 ff.
Mechanism of Dioxygen Cleavage in Tetrahydrobiopterin‐Dependent Amino Acid Hydroxylases
Authors: Bassan Arianna , Blomberg Margareta R. A. , Siegbahn Per E. M.
Published: December 2002

The reaction mechanism for the formation of the hydroxylating intermediate in aromatic amino acid hydroxylases (i.e., phenylalanine hydroxylase, tyrosine hydroxylase, tryptophan hydroxylase) was investigated by means of hybrid density functional theory. These enzymes use molecular oxygen to hydroxylate both the tetrahydrobiopterin cofactor and the aromatic amino acid. A mechanism is proposed in which dioxygen forms a bridging bond between the cofactor and iron. The product is an iron(II)–peroxy–pterin intermediate, and iron was found to be essential for the catalysis of this step. No stable intermediates involving a pterin radical cation and a superoxide ion O2− were found on the reaction pathway. Heterolysis of the OO bond in the iron(II)–peroxy–pterin intermediate is promoted by one of the water molecules coordinated to iron and releases hydroxypterin and the high‐valent iron oxo species FeIVO, which can carry out subsequent hydroxylation of aromatic rings. In the proposed mechanism, the formation of the bridging CO bond is rate‐limiting in the formation of FeIVO.
Guest Binding and Orientation within Open Nanoscale Hosts
Authors: Laughrey Zachary R. , Gibb Corinne L. D. , Senechal Tangi , Gibb Bruce C.
Published: December 2002

The synthesis of three different nanoscale molecular hosts is reported. These cavitands each possess a highly preorganized cavity with an open portal (nearly 1 nm wide), by which guests can enter and egress the cavity. Additionally, these hosts are deep‐functionalized with a crown of weakly acidic benzal CH groups which can form a variety of noncovalent interactions with guest molecules residing within the cavity. Thirty‐one guests were examined for their propensity to form complexes with the hosts. Guests that possess halogen atoms were the strongest binders, suggesting the formation of polydentate CH⋅⋅⋅XR hydrogen bonds with the deep crown of benzal hydrogens. Exchange rates between the free and bound states were noted to be dependent on the size of the guest and the solvent used to study complexation. In general, stronger binding and slower exchange were noted for complexations carried out in DMSO with highly complementary guests. The orientation of each guest within the cavity was determined using either EXSY NMR spectroscopy or 1H NMR shift data. Cumulatively these results showed that the principal factors directing orientation were interactions with the benzal groups and the type of solvent. Van't Hoff analyses of selected complexations were also carried out. As well as revealing that all complexations were entropically unfavorable, these experiments provided support for guest orientation determinations, and gave an estimation that the formation of a CH⋅⋅⋅IR hydrogen bond releases between 1 and 1.5 kcal mol−1.
Mono‐ and Binuclear Ruthenium Corroles: Synthesis, Spectroscopy, Electrochemistry, and Structural Characterization
Authors: Simkhovich Liliya , Luobeznova Inna , Goldberg Israel , Gross Zeev
Published: December 2002

The aim of this research was to prepare mononuclear ruthenium corroles, because of the well‐documented potency of analogous porphyrin complexes in catalysis. The syntheses of the mononuclear nitrosyl complexes [Ru(tpfc)(NO)] and [Ru(tdcc)(NO)] (tpfc=trianion of 5,10,15‐tris(pentafluorophenyl)corrole, tdcc=trianion of 5,10,15‐tris(2,6‐dichlorophenyl)corrole), and of the binuclear [{Ru(tpfc)}2] were achieved by using [{Ru(cod)Cl2}x] (cod=cyclooctadiene) as the metal source. The NMR spectra of all three complexes clearly demonstrate that they are diamagnetic; this is consistent with a triple bond between the metal ions in [{Ru(tpfc)}2] and is expected for classical {MNO}6 complexes. These features were further substantiated by the stretching frequencies of the {MNO} moieties, electrochemical measurements on all complexes, and the X‐ray crystal structures of [Ru(tpfc)(NO)] and [{Ru(tpfc)}2]. A comparison of the spectroscopic and structural characteristics of these new complexes with analogous iron corroles, as well as with iron and ruthenium porphyrins, suggests that it will be hard to obtain mononuclear ruthenium corroles without π‐accepting ligands.
Voltage‐Dependent Formation of Anion Channels by Synthetic Rigid‐Rod Push–Pull β‐Barrels
Authors: Sakai Naomi , Houdebert David , Matile Stefan
Published: December 2002

Ion channels formed by p‐octiphenyls equipped with amphiphilic, cationic tripeptide strands and either with (5) or without (6) axial dipole moment are described (preliminary communication: N. Sakai, S. Matile, J. Am. Chem. Soc. 2002, 124, 1184–1185). Fluorescence kinetics with variably polarized neutral or anionic vesicles, together with planar bilayer conductance measurements, reveal voltage dependence with weakly lyotropic anion selectivity, and deactivation by competing surface potentials of the ion channels formed by asymmetric 5. In planar bilayers, 5 forms short‐lived, poorly organized channels—similar to those produced by α‐helical natural antibiotics—capable of transforming into stable, ohmic p‐octiphenyl “β‐barrel” ion channels similar to those of the >99 % homologous but symmetric 6. Fluorescence depth quenching and circular dichroism studies confirm the effect of membrane potentials in promotion of the partitioning of 5 (but not 6) into the bilayers, identifying partitioning as the voltage‐dependent step.
Enantioselective Synthesis of Paraconic Acids
Authors: Chhor Rakeshwar B. , Nosse Bernd , Sörgel Sebastian , Böhm Claudius , Seitz Michael , Reiser Oliver
Published: December 2002

The development of a new method for the enantioselective synthesis of disubstituted γ‐butyrolactones is reported. Based on this strategy, the total synthesis of three paraconic acids, that is (−)‐roccellaric acid, (−)‐nephrosteranic acid and (−)‐protopraesorediosic acid, and the formal total synthesis of (−)‐methylenolactocin and (−)‐protolichesterinic acid is described, which are important because of their antibiotic and antitumor properties. Key steps of the synthesis are copper(I)‐catalyzed asymmetric cyclopropanations of furans, highly diastereoselective Sakurai allylations, Lewis acid or Lewis base catalyzed retroaldol/lactonization cascades, and ruthenium(II)‐catalyzed, intermolecular cross metathesis reactions.
Studies on Mimicry of Naturally Occurring Annonaceous Acetogenins: Non‐THF Analogues Leading to Remarkable Selective Cytotoxicity against Human Tumor Cells
Authors: Zeng Bu‐Bing , Wu Yikang , Jiang Sheng , Yu Qian , Yao Zhu‐Jun , Liu Zhong‐Hai , Li Hong‐Yan , Li Yan , Chen Xiao‐Guang , Wu Yu‐Lin
Published: December 2002

A class of structurally simplified analogues of the naturally occurring annonaceous acetogenins were developed, amongst which some non‐THF analogues showed remarkable cytotoxicities against tumor cell lines, as well as good selectivity between human tumor cells and normal cells. The synthetic routes were significantly shortened because of the removal of the chiral centers bearing the THF rings on the natural templates. This simplification also provides access to the parallel synthesis of these mimics by a combinatorial strategy. The remaining stereogenic centers at the positions α to the ethereal links were introduced by the Chiron approach from the easily accessible chiral building blocks 6 a and/or 6 b, made in turn from L‐ascorbic acid or D‐mannitol, while the one in the butenolide segment was taken from L‐lactate. All four diastereomeric non‐THF analogues 2 a–2 d showed remarkable activity against the HCT‐8 cell line, and better differentiation was found when testing against the HT‐29 cell line. It was also discovered that both the butenolide and ethylene glycol subunits play essential roles in the cytotoxicities against tumor cell lines, while the 10‐substituted hydroxy group and the absolute configuration of methyl group at the butenolide moiety are less important for their activity.
Functional Supramolecular Devices: [M4IIL4]8+ [2×2]‐Grid‐Type Complexes as Multilevel Molecular Electronic Species
Authors: Ruben Mario , Breuning Esther , Barboiu Mihail , Gisselbrecht Jean‐Paul , Lehn Jean‐Marie
Published: December 2002

The [M4IIL4]8+ [2×2]‐grid‐type complexes 1–8 present a set of features of particular interest for potential applications. All complexes exhibit multiple reduction levels at low reduction potentials paired with rather high stability. The modulation of the reduction potentials is possible by introduction of appropriate substituents on the ligands. The CoII4 complexes 1–5 present a remarkable regularity in the disposition of the reduction levels, indicating the ability of the CoII sites to transmit electronic interactions between reduced ligands. In general, all investigated molecular systems 1–8 show characteristics typical for multilevel supramolecular electronic devices.
Accurate Quantum‐Chemical Prediction of Enthalpies of Formation of Small Molecules in the Gas Phase
Authors: Klopper Wim , Noga Jozef
Published: December 2002

The coupled‐cluster approach, including single and double excitations and perturbative corrections for triple excitations, is capable of predicting molecular electronic energies and enthalpies of formation of small molecules in the gas phase with very high accuracy (specifically, with error bars less than 5 kJ mol−1), provided that the electronic wavefunction is dominated by the Hartree–Fock configuration. This capability is illustrated by calculations on molecules containing O–H and O–F bonds, namely OH, FO, H2O, HOF, and F2O. To achieve this very high accuracy, it is imperative to account for electron‐correlation effects in a quantitative manner, either by using explicitly correlated two‐particle basis functions (R12 functions) or by extrapolating to the limit of a complete basis. Besides taking into account harmonic zero‐point vibrational energies, it is also necessary to account for anharmonic corrections to the zero‐point vibrational energies, to include the core orbitals into the coupled‐cluster calculations, and to account for spin–orbit corrections and scalar relativistic effects. These additional corrections constitute small but significant contributions in the range of 1–4 kJ mol−1 to the enthalpies of formation of the aforementioned molecules. The highly accurate coupled‐cluster results, obtained by employing R12 functions and by including various corrections, are compared with standard Kohn–Sham density‐functional calculations as well as with the Gaussian‐2 and complete‐basis‐set model chemistries.
Porphyrin‐Containing Glycodendrimers
Authors: Ballardini Roberto , Colonna Barbara , Gandolfi M. T. , Kalovidouris Stacey A. , Orzel Lukasz , Raymo Françisco M. , Stoddart J. Fraser
Published: December 2002

Two dendrimers, incorporating tetrasubstituted porphyrin units as their cores and, in one case, four perbenzoylated and, in the other case, twelve peracetylated β‐D‐glucopyranosyl residues at their peripheries, have been synthesized in yields of 39 and 16%, respectively. The deprotection of these dendrimers was achieved quantitatively under Zemplén conditions. The protected and deprotected dendrimers were characterized by liquid secondary‐ion or matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry and by a combination of one‐ and two‐dimensional 1H and 13C NMR spectroscopy. All the glycodendrimers were also characterized by absorption and emission spectroscopy, and lifetime measurements. The most relevant result is that both protected and deprotected dendrimers show two fluorescence lifetime values that are different from the porphyrin model compounds. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Stereoselective Hydrolysis of Quaternary Quinuclidinium Benzoates Catalyzed by Butyrylcholinesterase
Authors: Primoz̆ič Ines , Hrenar Tomica , Tomić Srđanka , Meić Zlatko
Published: December 2002

Four chiral, quaternary, N‐methyl and N‐benzyl derivatives of (R)‐ and (S)‐quinuclidin‐3‐yl benzoates were synthesized and studied as substrates of horse serum butyrylcholinesterase (BChE). The kcat for the substrates decreased in the order (R)‐N‐methyl > (R)‐N‐benzyl (2.3‐fold slower) >> (S)‐N‐methyl (70.5‐fold slower reaction), while for the (S)‐N‐benzyl ester inhibition of the enzyme was observed. The kinetics of inhibition (Ka = 3.3 μM) indicated that binding to the catalytic site of BChE occurred. From the ratio of the kcat/KM values of both enantiomers an enantiomeric excess of 95% was calculated for N‐methyl derivatives. Thus, BChE is suitable as a biocatalyst for the resolution of racemic quaternary quinuclidinium esters. In order to explain the experimental data, combined quantum chemical (HF/3−21G*) and semiempirical (PM3) calculations within the ONIOM scheme of the stable species in the acylation step were performed. Geometry optimizations were carried out for all benzoate esters for an assumed active site model of BChE. It was confirmed that hydrolysis is affected to an appreciable extent by a proper geometrical orientation of substrates at the choline subsite. The energies of the optimized systems were in good agreement with the experimental data. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
A DFT Study on the Interaction of Li+ and Na+ with Alkyl‐Substituted Ethenes
Authors: Froudakis George E. , Stratakis Manolis
Published: December 2002

The interaction of Li+ and Na+ with several alkyl‐substituted ethenes was calculated by the DFT method. Two trends were found. The first is that, for the majority of alkenes, the cations do not bind on top of the double bond, but close to it, either towards the more‐ or the less‐substituted side of the alkene. This type of interaction is found even with highly symmetrical alkenes such as tetramethylethene. The second trend is that there is a relatively strong interaction between both cations and the alkyl chains of the double bond at the homoallylic position. These calculations were correlated to regioselectivity results in the dye‐sensitized photooxygenation of alkenes within alkali‐metal exchanged zeolite Y. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Methanofullerenes from Macrocyclic Malonates
Authors: Carano Maurizio , Corvaja Carlo , Garlaschelli Luigi , Maggini Michele , Marcaccio Massimo , Paolucci Francesco , Pasini Dario , Righetti Pier Paolo , Sartori Elena , Toffoletti Antonio
Published: December 2002

In this paper we describe the synthesis and intercomparison of several new methanofullerenes, each bearing a macrocyclic crown ether containing a malonate moiety directly attached to the C60‐fullerene core. Their complexing abilities with primary alkylammonium ions were investigated by NMR and mass spectrometry, and also by transport experiments through a liquid membrane. We also report on their electrochemical behaviour, together with EPR analysis of their supramolecular complexes with alkyl ammonium molecules labelled with a stable nitroxide radical. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
A Straightforward Synthesis of N‐Functionalized β‐Diimines
Authors: Maraval Alexandrine , Igau Alain , Donnadieu Bruno , Majoral Jean‐Pierre
Published: December 2002

Reaction of Schwartz’s reagent [Cp2ZrHCl]n (1) (one or two equivalents) with gem‐dinitrile compounds of the type X(CN)2 [X = CMe2, CBenz2, P(NiPr2)2] gives the corresponding mono‐ and di‐N‐zirconated imino complexes selectively. Substitution reactions of the zirconocene metal fragment with electrophiles such as, for example, chlorophosphanes of the type R2PCl, acid chlorides RC(O)Cl or the iminium salt [CH2NMe2]Cl allowed the preparation of a large variety of stable N‐functionalized mono‐ and β‐diimine derivatives. The nature of the X group is of particular importance for the success of the substitution reaction step. The X‐ray crystal structures obtained for the N‐functionalized gem‐aldimino‐nitrile compounds 9, 10b, the N‐phosphorylated β‐diimine 32, and the gem‐formyl nitrile derivative 12b are presented. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Effects of prenyl pyrophosphates on the binding of PKCγ with RACK1
Authors: Chen Yu‐Hsun , Wang Han‐Chung , Lin Ching‐Yu , Chuang Nin‐Nin
Published: December 2002

Receptors for activated C kinase (RACKs) are a group of PKC binding proteins that have been shown to mediate isoform‐selective functions of PKC and to be crucial in the translocation and subsequent functioning of the PKC isoenzymes on activation. RACK1 cDNA from the shrimp Penaeus japonicus was isolated by homology cloning. The hepatopancreas cDNA from this shrimp was found to encode a 318‐residue polypeptide whose predicted amino acid sequence shared 91% homology with human Gβ2‐like proteins. Expression of the cDNA of shrimp RACK1 in vitro yielded a 45‐kDa polypeptide with positive reactivity toward the monoclonal antibodies against RACK1 of mammals. The shrimp RACK1 was biotinylated and used to compare the effects of geranylgeranyl pyrophosphate and farnesyl pyrophosphate on its binding with PKCγ in anti‐biotin‐IgG precipitates. PKCγs were isolated from shrimp eyes and mouse brains. Both enzyme preparations were able to inhibit taxol‐induced tubulin polymerization. Interestingly, when either geranylgeranyl pyrophosphate or farnesyl pyrophosphate was reduced to the submicrogram level, the recruitment activity of RACK1 with purified PKCγ was found to increase dramatically. The activation is especially significant for RACK1 and PKCγ from different species. The observation implies that the deprivation of prenyl pyrophosphate might function as a signal for RACK1 to switch the binding from the conventional isoenzymes of PKC (cPKC) to the novel isoenzymes of PKC (nPKC). A hydrophobic binding pocket for geranylgeranyl pyrophosphate in RACK1 is further revealed via prenylation with protein geranylgeranyl transferase I of shrimp P. japonicus. J. Exp. Zool. 295A:71–82, 2003. © 2003 Wiley‐Liss, Inc.
Monoclonal antibody G3 epitope location on Guinea pig sperm membrane protein, sperad
Authors: Ilayperuma Isurani
Published: December 2002

A protein isolated from guinea pig testes was purified, characterized as having a molecular weight of 34 kDa, and subjected to amino acid sequencing. A monoclonal antibody to the protein (G11) was found to cross‐react with a second monoclonal antibody (G3). Two peptide sequences derived from the purified protein, labeled as 34 kDa G11, show sequence homology with sperad. Sperad is a transmembrane protein present in the peri‐acrosomal plasma membrane of guinea pig spermatozoa. Both G11 and G3 monoclonal antibodies recognise antigens on the equatorial segment plasma membrane of guinea pig spermatozoa following the acrosome‐reaction. Therefore, experiments were designed to check whether monoclonal antibody G3 epitope is present on the sperad. The intra‐cytoplasmic domain and the extra‐cytoplasmic domain of sperad was amplified from a guinea pig testes cDNA expression library by polymerase chain reaction and cloned into pGEM T‐Easy vector. The recombinant pGEM T‐Easy plasmids were subjected to in vitro transcription and translation by rabbit reticulocyte lysate system. The resulting translated products were immunoprecipitated with monoclonal antibody G3. The results obtained from this study confirmed that monoclonal antibody G3 epitope is located on the extra‐cytoplasmic domain but not on the intra‐cytoplasmic domain of sperad. J. Exp. Zool. 295A:92–98, 2003. © 2003 Wiley‐Liss, Inc.
The Statistical Regression Calculation in Plastics Processing – Process Analysis, Optimization and Monitoring
Authors: Heim Hans‐Peter
Published: December 2002

Plastics processing companies can only meet up to present‐day quality requirements if they adopt systematic methods. This holds particularly true for the extremely stringent demands that are now placed on injection molding technology. Working on from a sound experimental basis, it is possible to define cause/effect correlations for two sets of empirical data (the current process conditions and the molded part attributes) for each quality variable by using a statistical process model. The process model enables the processor to calculate the effect of each individual combination of parameters in the experimental area and to perform an optimization. If it proves possible to describe the cause/effect correlation between the fluctuations in the molded part attributes and those in the process parameters by means of a statistical process model, then this can be used for the continuous monitoring of production. The statistical experimentation method and continuous process monitoring are grouped together to form the so‐called CPC concept, permitting traceable, gap‐free documentation of the quality data for a production chain. Three examples are set out to illustrate the possibilities for use of the CPC concept; these are then assessed on the basis of the benefit observed.

Engine‐cooling fan.

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Engine‐cooling fan.
Flexible Use of Single‐Screw Extruders through Multiple‐Process Optimization
Authors: Potente Helmut , Pape Jens
Published: December 2002

Using general‐purpose screws to process different types of material offers considerable cost advantages over special‐purpose screws. Designing screws of this type is generally a difficult task, since modifications to different aspects of the geometry can run counter to each other in some cases. Optimization software is thus of particular benefit here. For this reason, a program was developed for the optimization of general‐purpose screws. A central feature of this program is an appraisal system for the computer‐aided evaluation of single‐screw simulations. The performance of the software was verified on the basis of actual extrusion experiments.

Temperature measuring cross for measuring thermal homogeneity.

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Temperature measuring cross for measuring thermal homogeneity.
Extruder Concept for the Direct Plastification of Cereal Materials
Authors: Potente Helmut , Reckert Frank
Published: December 2002

In the wake of a growing environmental awareness, the substitution of conventional plastics by biologically degradable materials is assuming ever‐greater importance. The displacement of conventional plastics made from fossil raw materials by materials that are manufactured either fully or in part from agriculturally‐produced, harvested goods constitutes one of the technically feasible uses of renewable raw materials. The successful market introduction of alternative products, however, requires not only consideration of the qualitative aspect but also an eye to the economic factors. It is for this reason that an extruder concept is presented here that can be used for directly plastificating cereal materials in the form of coarsely ground grain, for example. This then opens up the way to a low‐price basic material which also holds a high potential when viewed in economic terms. After giving a short overview of the possibilities that exist for the plastification of materials containing starch, this paper takes a look at the differences between this alternative extruder concept and the conventional single‐screw extrusion process for thermoplastics. Further details are given of the solids conveyance and plastification processes to this end.

Schematic diagram of the arrangement of the functional sections.

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Schematic diagram of the arrangement of the functional sections.
Calcium fluxes in human trophoblast (BeWo) cells: Calcium channels, calcium‐ATPase, and sodium‐calcium exchanger expression
Authors: Moreau Robert , Simoneau Lucie , Lafond Julie
Published: December 2002

Although placental transfer of maternal calcium (Ca2+) is a crucial process for fetal development, the biochemical mechanisms are poorly understood. In the current study, we have investigated the characteristics of Ca2+ fluxes in relation with cell Ca2+ homeostasis in the human placental trophoblast cell line BeWo. Time‐courses of Ca2+ uptake by BeWo cells displayed rapid initial entry (initial velocity (Vi) of 3.42 ± 0.35 nmol/mg protein/min) and subsequent establishment of a plateau. Ca2+ efflux studies with 45Ca2+‐loaded cells also showed rapid declined of cell‐associated 45Ca2+ with a Vi of efflux (Vei) of 3.30 ± 0.08 nmol/mg protein/min. Further identification of membrane gates for Ca2+ entry in BeWo cells was carried out. Expression of Ca2+ transporter/channel CaT1 and L‐type α1S subunit was showed by RT‐PCR. However, mRNA for CaT2 channel and L‐type α1C and α1D subunits were not revealed. Membrane systems responsible for intracellular Ca2+ extrusion from BeWo cells were also investigated. Plasma membrane Ca2+‐ATPases (PMCA) and Na/Ca exchangers (NCX) were detected by Western blot in BeWo cells. Expression of specific isoforms of PMCA and NCX was further investigated by RT‐PCR. Messenger RNAs of four isoforms of PMCA (PMCA 1–4) were detected. The presence of messenger RNAs of two NCX isoforms (NCX1 and NCX3) was observed. Ca2+ flux studies in Na‐free incubation medium indicated that NCX played a minimal role in the cell Ca2+ fluxes. Inorganic ions such as cadmium and manganese did not modify the Ca2+ fluxes, however, barium increased cell‐associated 45Ca2+ by, in part, by reducing radiolabel exit. Mol. Reprod. Dev. 64: 189–198, 2003. © 2003 Wiley‐Liss, Inc.
Detection of DNA damage in bovine metaphase II oocytes resulting from cryopreservation
Authors: Men H. , Monson R.L. , Parrish J.J. , Rutledge J.J.
Published: December 2002

Developmental competence of mammalian oocytes is compromised by currently available oocyte cryopreservation protocols. Experiments were designed to examine the effect of three cryopreservation protocols on the integrity of bovine oocyte DNA. In vitro matured bovine oocytes were cryopreserved either by slow cooling, vitrification in 0.25 ml straws, or in open pulled straws. After thawing/warming, recovered oocytes were immediately subjected to morphological evaluation. Morphologically intact oocytes underwent comet assay to detect cryoinjury at DNA level. All cryopreservation protocols resulted in significant morphological damage as well as DNA damage compared to unfrozen control. Among the morphologically intact oocytes, there was no difference among protocols in the number of oocytes displaying DNA damage. However, oocytes that had been cryopreserved by slow cooling or by vitrification in open pulled straws exhibited more damage than those vitrified in 0.25 ml straws in the extent of DNA damage. If we combine the number of oocytes with morphological damage and oocytes with DNA damage, oocytes cooled by slow cooling resulted in the most damage. This experiment demonstrated that oocyte DNA is a target of cryoinjury and different protocols result in different degrees of damage. Mol. Reprod. Dev. 64: 245–250, 2003. © 2003 Wiley‐Liss, Inc.
Intrathecal methylprednisolone does not improve outcome after severe spinal cord injury in the rat
Authors: Vanický Ivo , Urdzíková Lucia , Saganová Kamila , Mars̆ala Martin
Published: December 2002

In a rat model of spinal cord compression‐induced injury, we have tested the hypothesis that intrathecally administered methylprednisolone will improve long‐term recovery of the injured rats. The effect of the treatment was evaluated quantitatively as 1, behavioral testing of spontaneous locomotion and 2, morphometric measurement of the tissue loss in the white matter and grey matter, respectively. Intrathecal methylprednisolone elicited remarkable motor reactions in the paraplegic animals immediately after administration. However, during 4 weeks' survival, no significant differences were observed in the parameters of recovery between the methylprednisolone‐treated and placebo‐treated group. We conclude that intrathecal administration of methylprednisolone had no effect on the outcome after compressive spinal cord injury in the rat at the doses and timing used in the present study.
Stimulation of Ca2+/Mg2+‐ATPase activity in adult rat cerebrocortical synaptosomes by 3‐5‐3′‐L‐triiodothyronine
Authors: Chakrabarti Nilkanta , Ray Arun K.
Published: December 2002

Stimulation of the calcium‐stimulated and magnesium‐dependent adenosine triphosphatase (Ca2+/Mg2+‐ATPase) activity by 3‐5‐3′‐L‐triiodothyronine (T3) in synaptosomes prepared from adult rat cerebral cortex was demonstrated both in vitro and in vivo. T3 stimulated the Ca2+/Mg2+‐ATPase activity in time dependent and dose dependent manner to depolarization‐induced synaptosomes suspended in Ca2+‐loaded choline‐chloride buffer, represented involvement of the recovery phase of the changes in intrasynaptosomal Ca2+ level in this activation. T3 (100nM) also stimulated the enzyme activity in nondepolarized intact synaptosomes suspended in choline‐chloride buffer. T3 had direct and dose‐dependent stimulatory effect on the Ca2+/Mg2+‐ATPase activity of the lysed synaptosomal suspension. The effect of T3 on the lysed synaptosomes was higher than that found on the nondepolarized intact synaptosomes. The condition probably represents the direct and/or indirect interaction of T3 with the enzyme through plasmamembrane related phenomenon that needs further investigation. After T3 treatment, a dose‐dependent activation of the enzyme was found in vivo. It appears that T3 plays a role on adult brain neuronal Ca2+‐mobilization through stimulation of the Ca2+/Mg2+‐ATPase activity in nerve terminals.
In‐Situ Determination of the Charging of Nanometer and Submicron Particles at High Temperatures
Authors: Schiel Annette , Weber Alfred P. , Kasper Gerhard , Schmid Hans‐Joachim
Published: December 2002

Thermal charging of submicron and nanometer particles has been studied for model aerosols of TiO2 and SiO2 as well as Al‐Si (aluminosilicate) at 1 000 °C with a new quasi in‐situ technique. The size dependence of the particle separation efficiency for electrostatic precipitation was determined. The charging state of the particles was obtained from evaluating the global Deutsch number for precipitation in an electric field applied to a laminar flow based on particle trajectory considerations.
2,2‐Dinitro‐1,3‐Bis‐Nitrooxy‐Propane (NPN): A New Energetic Plasticizer
Authors: Wingborg Niklas , Eldsäter Carina
Published: December 2002

A new energetic plasticizer, 2,2‐dinitro‐1,3‐bis‐nitrooxy‐propane (NPN), has been characterized. Its high oxygen balance, +12.5%, and low glass transition temperature, −81.5 °C (midpoint), makes it very attractive as an energetic plasticizer in solid propellants. The ability of NPN to lower the glass transition temperature and viscosity of uncured PolyNIMMO has been studied and compared to other energetic plasticizers, such as BDNPA/F and butyl‐NENA. NPN has a similar plasticizing effect as butyl‐NENA, both on depressing the glass transition temperature and lowering the viscosity. To increase the poor thermal stability of NPN, several conventional nitrocellulose/nitroglycerine stabilizers were evaluated. Further work is however needed to find a more effective stabilizer.
The Incompatibility of RDX and Lead
Authors: Bellamy Anthony J. , Dearing Susannah L.
Published: December 2002

Accelerated ageing at 100 °C of mixtures of RHA (RDX + 6% HMX) and lead has demonstrated that these components are incompatible. The rate of reaction to give N2O, hexamine and triazine was shown to be dependent upon the particle size of the lead, and pressing pressure for discs of these mixtures. In some cases there was more hexamine than RDX after 320 h at 100 °C. It is suggested that the preparation of the sample for the standard vacuum stability test (compatibility test) should be modified, using particles of explosive and nonexplosive of comparable size, and possibly even pressing, in order to simulate the conditions present in operating systems.
Optical properties of Si‐, Ge‐ and Sn‐doped GaN
Authors: Shikanaia A. , Fukahori H. , Kawakami Y. , Hazu K. , Sota T. , Mitani T. , Mukai T. , Fujita Sg.
Published: December 2002

Photoluminescence and reflectance spectra of Si‐, Ge‐ and Sn‐doped GaN epilayers grown on sapphire substrates at 10 K have been investigated, by which ionization energies on the Ga site were determined as 29, 30 and 33 meV, respectively. To investigate the coherent properties of excitons, the dephasing times of excitons in undoped and Si‐doped GaN on sapphire substrates and freestanding GaN were measured using the degenerate four‐wave mixing technique. The resulting homogeneous broadenings in undoped and Si‐doped GaN on sapphire substrates were about twice as large as that in freestanding GaN, which indicates that defect‐induced scattering is stronger in the former than in the latter.
Picosecond time‐resolved studies of excited state lifetime of Be acceptor in GaAs/AlAs multiple quantum wells
Authors: Zheng W.‐M. , Halsall M. P. , Harrison P. , Wells J.‐P. R. , Bradley I. V. , Steer M. J.
Published: December 2002

The influence of the quantum well potential on the carrier dynamics of holes bound to the acceptors in Be δ‐doped AlAs/GaAs multiple quantum wells is investigated by far‐infrared time‐resolved spectroscopy using the Free‐Electron Laser for Infrared eXperiments (FELIX). The lifetime of the 2p excited state of acceptors was measured as a function of the width of the quantum well and the temperature. It is found that the lifetime decreases monotonically with decreasing well width and is independent of temperature. We suggest that the relaxation process of the 2p → 1s is non‐radiative and mediated via confined acoustic phonon modes, in particular, zone‐folded acoustic phonon modes which arise from the periodic nature of the multiple quantum well samples. For one particular well width the lifetime was measured across the inhomogeneously broadened D‐line as 30, 30, 70, and 105 ps for 43, 44, 46, and 47 μm wavelengths, respectively. We believe the latter is due to diffusion of the Be δ‐doped atomic layer in the quantum wells.
Conductivity via impurities in low‐doped uncompensated silicon
Authors: Melnikov A. P.
Published: December 2002

It was found that in low‐doped silicon crystals (2 × 1016 < N < 1017 cm–3) with compensation rate decrease (10–5 < K < 10–2) the experimental results differ from the theoretical ones. At low electric fields (E) this concerns the values of the activation energy (ε3) and the dependence of ε3 on N and K. The results are explained by the influence of neutral impurity interaction on the density of states. With increasing E a previously unknown conductivity (σM) appears. The dependence of σM on N, K, E, magnetic field (H), and temperature (T) is quite different from the dependence that is usual for σ3 conductivity. The results are explained by the appearance of conductivity via H?‐like states of impurities, which are concentrated in the vicinity of edge dislocations.
Far‐infrared spectroscopy of shallow acceptors in semi‐insulating GaAs: evidence for defect interactions with EL2
Authors: Alt H. Ch. , Gomeniuk Y. , Kretzer U.
Published: December 2002

Far‐infrared FTIR absorption measurements are carried out at 10 K in order to assess the uncompensated fraction of shallow acceptors in semi‐insulating GaAs after optical bleaching of EL2. In carbon‐doped material a linear correlation of the G line at 122.3 cm–1 with the CAs concentration is found in the whole concentration range between 1 × 1014 and 2 × 1016 cm–3. In samples co‐doped with zinc in the range around 1 × 1016 cm–3 and 1 to 2 × 1015 cm–3 carbon, both, ZnGa‐ and CAs‐related far‐infrared absorption lines are observed. Taking into consideration the Fermi level position after bleaching of EL2, it can be concluded that no other donors than EL2 are present above a total concentration of 1 × 1015 cm–3. In addition to the far‐infrared measurements, the intracentre transition of EL2 (A1 → T2) at 1.0389 eV is studied. The results are compatible only with an increase of the total EL2 concentration with the shallow acceptor concentration. Possible mechanisms for the interaction between shallow‐ and deep‐level defects are discussed.
Study of IR absorption and photoconductivity spectra of thermal double donors in silicon
Authors: Andreev B. A. , Emtsev V. V. , Kryzhkov D. I. , Kuritsyn D. I. , Shmagin V. B.
Published: December 2002

The IR absorption and photoconductivity spectra of a double donor (TDD) family with ionization energies less than 70 meV in silicon were investigated using Fourier transform spectroscopy with a resolution down to 0.25 cm–1. The values of line frequencies, widths, splitting and absorption cross sections for transitions from the ground to p‐states (including high‐excited states) were obtained. Determination of absorption cross sections was made using Hall data and concerted changes of boron and TDDi concentrations caused by neutralization of impurities under band gap illumination.
N‐type (P, Sb) and p‐type (B) doping of hydrogenated amorphous Si by reactive rf co‐sputtering
Authors: Ohmura Y. , Takahashi M. , Suzuki M. , Emura A. , Sakamoto N. , Meguro T. , Yamamoto Y.
Published: December 2002

B, P or Sb were doped into amorphous silicon films by the reactive radio‐frequency co‐sputtering method. The targets used were composed of silicon wafers and small about 1 mm thick chips of the respective impurity element, which were attached to the silicon wafers with silver powder cement and epoxy resins. Argon and hydrogen partial pressures used were 5 × 10–3 and 5 × 10–4 torr, respectively. The impurity concentration in the film was determined by secondary ion mass spectroscopy for B and P and by He backscattering spectroscopy for Sb. The substrates were kept at 200–250 °C during deposition. Raman spectra revealed that films prepared even at 250 °C were amorphous. Heterostructures, where P‐, Sb‐ or B‐doped films were deposited on p‐ or n‐type Si, exhibited good rectification characteristics of n diodes. It has been shown that the co‐sputtering method can produce low‐resistivity p‐type (B) and n‐type (P) a‐SH films for relatively low concentrations of B and P, respectively.
Lithium as a normalizer for the assessment of anthropogenic metal contamination of sediments of the southern area of Patos Lagoon
Authors: Niencheski Luis Felipe Hax , Baraj Besnik , Franca Rosilea Garcia , Mirlean Nicolai
Published: December 2002

In order to compare their usefulness, various approaches were used for the assessment of the natural background of metals in sediments of the Southern end of Patos Lagoon, Brazil. Lithium and aluminum were chosen as the most appropriate normalizers for the sampling sites because iron demonstrated elevated values, particularly in the harbor. A strong correlation of Li with Al was observed, which confirmed the presence of pegmatite in the studied area which is rich in Li minerals. Using Li as a normalizer and applying an enrichment factor, cadmium presented elevated results, mainly in the harbor, probably due to 25 years of activity of a fertilizer complex, which uses raw material enriched with Cd up to 100 times the region's natural background.
Status of ecological health of wetlands in Punjab, India
Authors: Ladhar Satnam Singh
Published: December 2002

To identify important wetlands from ecological, socio-economic, hydro-biological, religious and recreational points of view, a study was undertaken in the state of Punjab with the aim of designing suitable conservation strategies and developing site-specific management plans for their timely implementation. The survey shows that in Punjab, all the natural and man-made wetlands cover an area of about 23000 ha. While most of the natural wetlands are under severe stress from reclamation for agriculture, the man-made wetlands which are primarily being maintained for the purpose of meeting water requirements of Punjab and other adjoining states are under threat of general ecological degradation. Though conservation and protection of wetlands in the state have attracted the attention of the government, the general attitude of the public towards these ecosystems is negative with efforts directed toward making alternate uses of the wetlands in the short-term. As a consequence, a large number of natural wetlands have vanished and the trend is continuing. Some of the very prominent wetlands that have totally lost their ecological character due to reclamation include Bhupinder Sagar, Chhangali Chhamb, and Rahon de Chhamb. Major reasons for their loss include drainage of low lands, reduced flow of water into natural wetlands, siltation and encroachments. Due to the continuous loss of natural wetlands in the state not only the local hydrological regime is changing rapidly but also the biological diversity has come under threatening pressure. This study has found that immediate conservation measures have to be implemented in some important wetlands in the state. The Punjab State Council for Science and Technology has identified five wetlands, Keshopur-Miani Jheel, Chhawarian Bhangar Chhamb, Jastarwal Jheel, Mand Bharthala and Dholbaha Reservoir, to be designated as wetlands of state significance. These are in addition to Harike, Kanjli and Ropar wetlands that have been included in the list of wetlands of national importance.