bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fast, Solid‐Phase Synthesis of Chiral Peptide Nucleic Acids with a High Optical Purity by a Submonomeric Strategy
Authors: Sforza Stefano , Tedeschi Tullia , Corradini Roberto , Ciavardelli Domenico , Dossena Arnaldo , Marchelli Rosangela 
Published: March 2003

AbstractThe solid‐phase synthesis of chiral peptide nucleic acids (PNAs) usually results in partial epimerization of the products, since the α‐nitrogen atom of the amino acid is involved in an amidic bond. It is also time‐consuming, since all the chiral monomers bearing different nucleobases have to be independently synthesized. In order to prevent racemization and to speed up the synthetic procedure we adopted a submonomeric approach by using a solid‐phase, Boc‐based PNA synthesis in which the chiral backbone orthogonally Nα‐Fmoc‐protected (submonomer) was first linked to the growing chain on the resin, followed by Fmoc‐deprotection and derivatization with the carboxymethylnucleobase. The submonomer bearing the D‐lysine residue was designed by protecting the Nα‐(aminoethyl)amino acid moiety with an Fmoc protecting group, compatible with standard Boc chemistry, and with the use of an MBHA‐PS resin, normally employed for PNA synthesis. Different synthetic pathways towards the desired submonomer were studied by using the amino acid D‐lysine as a chiral synthon, obtaining a fast method leading to a high yield and an excellent enantiomeric excess of the submonomer. The solid‐phase submonomeric reaction conditions were optimized for the synthesis of a thyminyl PNA dimer and then used to synthesize two different chiral PNAs. In this way two advantages were obtained: a lower degree of racemization in the coupling step during the solid‐phase synthesis and the possibility of using the same submonomer for every different nucleobase. All the D‐lysine‐based chiral PNAs were obtained in good yields and, as compared with PNAs synthesized by other coupling methods, showed the highest optical purity reported so far. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Controlled Stepwise Release of Fragrance Alcohols from Dendrimer‐Based 2‐Carbamoylbenzoates by Neighbouring Group Participation
Authors: Frérot Eric , Herbal Karim , Herrmann Andreas 
Published: March 2003

Abstract2‐Carbamoylbenzoates which are chemically bound to the surface of dendrimers were found to release tertiary fragrance alcohols by neighbouring group assisted alkaline hydrolysis under mild reaction conditions. Owing to the excellent separation of the intermediate reaction products by analytical HPLC, the kinetic rate constants of the first two consecutive reaction steps of fragrance release could be determined for a series of modified dendrimers with increasing size. Because of the intramolecular neighbouring group effect, the kinetic rate constants were found to be independent of the dendrimer generation and are not influenced by steric effects on the surface of the macromolecules. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Asymmetric IrI‐Catalysed Allylic Alkylation Of Monosubstituted Allylic Acetates With Phosphorus Amidites As Ligands
Authors: Bartels Björn , García‐Yebra Cristina , Helmchen Günter 
Published: March 2003

AbstractMonodentate phosphorus amidites derived from 2,2′‐binaphthol and a variety of chiral amines were employed as ligands in IrI‐catalysed allylic alkylations of unsymmetrically substituted allylic acetates. The enantio‐ and regioselectivities of these reactions were investigated. Phosphorus amidites of bulky secondary chiral amines induced enantioselectivities of up to 94% ee in reactions of linear substrates. Phosphorus amidites derived from chiral primary amines, which have not been previously employed in asymmetric catalysis, furnished improved regioselectivities. The use of LiCl as additive led to improved regio‐ and enantioselectivities. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
An Aza Analogue of iso‐Levoglucosenone: Synthesis and Application of a New Building Block for Imino Sugars
Authors: Ostrowski Jens , Altenbach Hans‐Josef , Wischnat Ralf , Brauer David J. 
Published: March 2003

AbstractThe aza analogue 3 of iso‐levoglucosenone, which is easily accessible from furylglycine, was used as a flexible building block for the synthesis of various imino sugars. Enantiomerically pure products are available starting from optically active furylglycine derivatives. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Cover Picture: Eur. J. Org. Chem. 6/2003
Authors: Brotin Thierry , Dutasta Jean‐Pierre 
Published: March 2003

AbstractThe cover picture shows the different NMR spectra of xenon atoms encapsulated in cryptophane‐A and C2‐symmetrical analogs. The high sensitivity of the xenon chemical shift to its environment allows the detection of small structural perturbations of the hosts. A slight modification of the internal volume of the cage compounds leads to an appreciable change of the 129Xe NMR chemical shifts. There exists a direct correlation between the stability constant Ka and the van der Waals volume of the cavity. Details of the synthesis of the new cryptophane hosts and complexation dynamics are presented in the article by T. Brotin and J.‐P. Dutasta on p. 973 ff.
Attributions for the negative historical actions of a group
Authors: Doosje Bertjan , Branscombe Nyla R. 
Published: March 2003

AbstractTwo field studies examined the attributions made for the historically negative behaviour of a group as a whole, depending on whether the actions were committed by the ingroup or an outgroup. In the first study, Jewish people assigned more internal responsibility to Germans for their treatment of Jewish people during the Second World War than Germans assigned to their own group. In the second study, people attributed the negative historical actions of another nation more internally (and less externally) than similar negative historical actions committed by their own nation. This pattern of intergroup attributional bias was more pronounced among people who highly identified with their national ingroup. Outgroup homogeneity and perceptions of differences between the groups were also significantly predicted by ingroup identification. Links between social identity theory and the intergroup attribution bias are considered. Copyright © 2002 John Wiley & Sons, Ltd.
Poly(vinyl alcohol) hydrogels: Their synthesis and steps towards control of electroendosmosis
Authors: Purss Helen K. , Caulfield Marcus J. , Solomon David H. , Sommer‐Knudsen Jens 
Published: March 2003

AbstractPoly(vinyl alcohol) (PVAl) hydrogel networks cross‐linked with glutaraldehyde were prepared and their properties as membranes examined using a variety of techniques including preparative electrophoresis. Electroendosmosis (EEO) was observed and shown to be the result of charges on the membrane and of complexation with borate buffer ions. Investigation of “glutaraldehyde” solutions showed acid entities in, or formed in “glutaraldehyde” were responsible for EEO. Techniques for using “glutaraldehyde” which minimize EEO are described.
A family of single‐isomer, sulfated γ‐cyclodextrin chiral resolving agents for capillary electrophoresis: Octa(6‐O‐sulfo)‐γ‐cyclodextrin
Authors: Zhu Wenhong , Vigh Gyula 
Published: March 2003

AbstractThe second member of the single‐isomer, sulfated γ‐cyclodextrin family, the sodium salt of octa(6‐O‐sulfo)‐γ‐cyclodextrin (OS) has been synthesized, characterized and used to separate the enantiomers of nonelectrolyte, acidic, basic, and ampholytic analytes by capillary electrophoresis in acidic aqueous background electrolytes. The anionic effective mobilities of the nonelectrolyte and anionic analytes increased with increasing concentration of OS. The effective mobilities of strongly complexing cationic analytes became anionic with very low OS concentrations and passed local anionic effective mobility maxima as the OS concentration, and along with it, the ionic strength, of the background electrolyte increased. The effective mobilities of the weakly binding cationic analytes became only slightly anionic at high OS concentration values and did not show the local anionic effective mobility maxima. For nonelectrolyte analytes, separation selectivities decreased with increasing OS concentration. For cationic analytes, separation selectivities were highest where the effective mobilities of the less mobile enantiomers approached zero. OS proved to be a broadly applicable chiral resolving agent.
Practical integration of polymerase chain reaction amplification and electrophoretic analysis in microfluidic devices for genetic analysis
Authors: Rodriguez Isabel , Lesaicherre Marie , Tie Yan , Zou Quanbo , Yu Chen , Singh Janak , Meng Lim T. , Uppili Sridhar , Li Sam F. Y. , Gopalakrishnakone Ponnampalam , Selvanayagam Zachariah E. 
Published: March 2003

AbstractAn integrated system of a silicon‐based microfabricated polymerase chain reaction (μPCR) chamber and microfabricated electrophoretic glass chips have been developed. The PCR chamber was made of silicon and had aluminum heaters and temperature sensors integrated on the glass anodically bonded cover. Temperature uniformity in the reaction chamber was ±0.3°C using an improved novel “joint‐heating” scheme. Thermal cycling was digitally controlled with a temperature accuracy of ± 0.2°C. Small operating volumes together with high thermal conductivity of silicon made the device well suited to rapid cycling; 16 s/cycle were demonstrated. For analysis of the PCR products, the chamber output was transferred to the glass microchip by pressure. Analysis time of PCR amplified genomic DNA was obtained in the microchip in less than 180 s. The analysis procedure employed was reproducible, simple and practical by using viscous sieving solutions of hydroxypropylmethylcellulose and dynamically coated microchip channels with poly(vinylpyrrolidone). DNA fragments that differ in size by 18 base pairs (bp) were resolved. Analysis of genomic male and female amplified DNA by μPCR was achieved in microchip, and application of the integrated μPCR‐μchip for the identification of bird sex was tested. Genomic DNA samples from several bird species such as pigeon and chicken were analyzed. Hence, the system could be used as well to determine the sex of avian species.
Dynamic analyte introduction and focusing in plastic microfluidic devices for proteomic analysis
Authors: Li Yan , DeVoe Donald L. , Lee Cheng S. 
Published: March 2003

AbstractIsoelectric focusing (IEF) separations, in general, involve the use of the entire channel filled with a solution mixture containing protein/peptide analytes and carrier ampholytes for the creation of a pH gradient. Thus, the preparative capabilities of IEF are inherently greater than most microfluidics‐based electrokinetic separation techniques. To further increase sample loading and therefore the concentrations of focused analytes, a dynamic approach, which is based on electrokinetic injection of proteins/peptides from solution reservoirs, is demonstrated in this study. The proteins/peptides continuously migrate into the plastic microchannel and encounter a pH gradient established by carrier ampholytes originally present in the channel for focusing and separation. Dynamic sample introduction and analyte focusing in plastic microfluidic devices can be directly controlled by various electrokinetic conditions, including the injection time and the applied electric field strength. Differences in the sample loading are contributed by electrokinetic injection bias and are affected by the individual analyte's electrophoretic mobility. Under the influence of 30 min electrokinetic injection at constant electric field strength of 500 V/cm, the sample loading is enhanced by approximately 10–100 fold in comparison with conventional IEF.
Extraction of proteins from plant tissues for two‐dimensional electrophoresis analysis
Authors: Giavalisco Patrick , Nordhoff Eckhard , Lehrach Hans , Gobom Johan , Klose Joachim 
Published: March 2003

AbstractTo increase the number of proteins detectable by two‐dimensional electrophoresis (2‐DE) in plants, we present a new procedure for extracting total proteins from plant tissue. This method avoids any loss of proteins in the course of sample preparation and results in two different fractions, one comprising mainly the cytoplasmatic proteins, the other one containing predominantly structure bond proteins. 2‐DE patterns obtained from these two fractions show that the total number of different protein spots detected exceeds the degree of resolution commonly reported for plant proteins threefold.
Proteomic analysis of immunostained, laser‐capture microdissected brain samples
Authors: Moulédous Lionel , Hunt Sybille , Harcourt Rebecca , Harry Jenny L. , Williams Keith L. , Gutstein Howard B. 
Published: March 2003

AbstractProteomic analysis is often performed on homogenized preparations of whole tissues, which does not provide any information about relevant biochemical changes in specific cell types. Laser‐capture microdissection (LCM) is a technique that is precise enough to dissect single cells within a tissue section. Phenotypically defined cells of interest may be visualized by immunostaining prior to microdissection. Previously published immunostaining protocols adapted to LCM require the use of very high antibody titers and very short incubation times. This raises the concern that low‐abundance antigens would not be detected and that antisera would be rapidly depleted. In addition, protein recovery from samples was not evaluated in most of these studies. Here, we describe an optimized immunostaining method based on immunofluorescence. By comparing two‐dimensional electrophoresis (2‐DE) results obtained from immunostained LCM brain tissue samples to those obtained from unstained, manually dissected samples, we demonstrated that immunofluorescent staining gave comparable protein recovery and similar resolution of protein spots on 2‐DE gels. Moreover, matrix‐assisted laser desorption/ionization‐time of flight (MALDI‐TOF) mass spectrometry analysis of selected spots from gels derived from control and immunostained LCM samples revealed that the immunostaining process had minimal effect on protein identification. LCM of immunofluorescently labeled tissue sections is a practical and powerful method to perform proteomic studies on specifically defined cell groups.
Monitoring of protein profiles for the optimization of recombinant fermentation processes using public domain databases
Authors: Dürrschmid Karin , Marzban Gorji , Dürrschmid Eberhard , Striedner Gerald , Clementschitsch Franz , Cserjan‐Puschmann Monika , Bayer Karl 
Published: March 2003

AbstractThe expression of human superoxide dismutase in fed‐batch fermentation of E. coli HMS174(DE3)(pET3ahSOD) was studied as model system. Due to the frequently used strong T7 promoter system a high metabolic load is exerted, which triggers stress response mechanisms and finally leads to the differentiation of the host cell. As a consequence, host cell metabolism is partly shifted from growth to survival accompanied by significant alterations of the protein pattern. In terms of process optimization two‐dimensional electrophoresis deserves as a powerful tool to monitor these changes on protein level. For the analysis of samples derived from different states of recombinant protein production wide‐range Immobiline Dry Strips pH 3–10 were used. In order to establish an efficient procedure for accelerated process optimization and to avoid costly and time‐consuming analysis like mass spectrometry (MS), a database approach for the identification of significant changes of the protein pattern was evaluated. On average, 935 spots per gel were detected, whereby 50 are presumably stress‐relevant. Out of these, 24 proteins could be identified by using the SWISS‐2DPAGE database (www.expasy.ch/ch2d/). The identified proteins are involved in regulatory networks, energy metabolism, purine and pyrimidine nucleotide synthesis and translation. By this database approach, significant fluctuations of individual proteins in relation to recombinant protein production could be identified. Seven proteins show strong alterations (>100%) directly after induction and can therefore be stated as reliable marker proteins for the assessment of stress response. For distinctive interpretation of this highly specific information, a bioinformatic and statistic tool would be essential in order to perceive the role and contribution of individual proteins in stress response.
Multiplexed DNA sizing by capillary electrophoresis using entangled polymer solutions and diode array detection
Authors: Sulzbacher Caruso Célia , Lanças Fernando Mauro , Carrilho Emanuel 
Published: March 2003

AbstractWe developed a method for the analysis of multiplexed double‐stranded DNA (dsDNA) samples complexed to various intercalating dyes using entangled polymer solution. A commercial single‐column capillary electrophoresis (CE) instrument with diode array detection was used for multiplexed detection of DNA samples by addition of intercalating fluorescent molecules. A X174HinfI and a pGEM® DNA ladder (1 mg/mL) were used for the electrophoretic separation of dsDNA fragments ranging in size from 24 to 726 and 36 to 2645 bp, respectively. The results suggested that simultaneous electrophoretic separation of different DNA ladders multiplexed with different dyes could be performed in the same capillary yielding fast DNA sizing separations. CE analysis, which is often overpowered by slab gel in sample throughput, could now overcome this disadvantage by allowing multiplexed sample analysis in a fraction of the time needed for slab gel analysis. The separation efficiency of stained DNA molecules with both dyes were dramatically improved with buffers containing a large cation such as tetrapentylammonium ion (Npe4+) as the only cation in the buffer.
Monitoring folding transitions of synthetic, branched‐chain polypeptides by capillary zone electrophoresis
Authors: Verzola Barbara , Perduca Massimiliano , Mezô Gábor , Hudecz Ferenc , Righetti Pier Giorgio 
Published: March 2003

AbstractThe coil/helix transition of a synthetic, branched‐chain polymeric polypeptide (poly (Lys(Glu1‐DL‐Ala3)EAK), 50‐Lys residues long in the backbone, as a function of increasing molarities of methanol in solution, is here studied by both, circular dichroism (CD) and capillary zone electrophoresis. CD spectra showed that, at 75% v/v methanol, the transition from random coil to fully helical structure was obtained, in a pH 1.1 HCI solution in the presence of 20 mMNaCI. CZE studies, run in parallel, exhibited the classical unfolding to folding sigmoidal transition, with mid‐point at 60% v/v methanol concentration, plateauing atca.80% v/v organic solvent. Surprisingly, though, such unfolding to folding transition was accompanied by an expansion, rather than a contraction, of the resulting ordered polypeptide. As the charge of the polypeptide (a pure polycation at a pH of 2.1 in CZE) was kept rigorously constant, a plot of the radius of the polymer along the sigmoidal transition clearly showed that the radius of gyration of the helical, structured polypeptide was in fact larger than that of the random coil. Such results were confirmed by molecular dynamics simulations, which indicated that the dimensions of such polypeptide, in α‐helix configuration, were 8.5 nm (in length) and 3.2 nm (in diameter), whereas those of the corresponding random coil were 7.2 nm (in length) and 5.1 nm (length of shorter axis). It would thus appear that the randomized structure assumes the shape of a more compact object, roughly resembling a “rugby ball”.
Failure of immunocompetitive capillary electrophoresis assay to detect disease‐specific prion protein in buffy coat from humans and chimpanzees with Creutzfeldt‐Jakob disease
Authors: Cervenakova Larisa , Brown Paul , Soukharev Serguei , Yakovleva Oksana , Diringer Heino , Saenko Evgueni L. , Drohan William N. 
Published: March 2003

AbstractThe emergence of a new environmentally caused variant of Creutzfeldt‐Jakob disease (vCJD), the result of food‐born infection by the causative agent of bovine spongiform encephalopathy (BSE), has stimulated research on a practical diagnostic screening test. The immunocompetitive capillary electrophoresis (ICCE) assay has been reported to detect disease‐specific, proteinase‐resistant prion protein (PrPres) in the blood of scrapie‐infected sheep. We have applied this method to blood from CJD‐infected chimpanzees and humans. The threshold of detection achieved with our ICCE was 0.6 nM of synthetic peptide corresponding to the prion protein (PrP) C‐terminus, and 2 nM of recombinant human PrP at the optimized conditions. However, the test was unable to distinguish between extracts of leucocytes from healthy and CJD‐infected chimpanzees, and from healthy human donors and patients affected with various forms of CJD. Thus, the ICCE assay as presently performed is not suitable for use as a screening test in human transmissible spongiform encephalopathies (TSEs).
Determination of egg white lysozyme by on‐line coupled capillary isotachophoresis with capillary zone electrophoresis
Authors: Kvasnička František 
Published: March 2003

AbstractAn on‐line coupled capillary isotachophoresis – capillary zone electrophoresis method for the determination of lysozyme in selected food products is described. The optimized electrolyte system consisted of 10 mM NH4OH + 20 mM acetic acid (leading electrolyte), 5 mM ε‐aminocaproic acid +5 mM acetic acid (terminating electrolyte), and 20 mM ε‐aminocaproic acid +5 mM acetic acid +0.1% m/v hydroxypropylmethylcellulose (background electrolyte). A clear separation of lysozyme from other components of acidic sample extract was achieved within 15 min. Method characteristics, i.e., linearity (0–50 νg/mL), accuracy (recovery 96±5%), intra‐assay (3.8%), quantification limit (1 νg/ml), and detection limit (0.25 νg/mL) were determined. Low laboriousness, sufficient sensitivity and low running costs are important attributes of this method. The developed method is suitable for the quantification of the egg content in egg pasta.
A glycopeptide antibiotic chiral stationary phase for the enantiomer resolution of hydroxy acid derivatives by capillary electrochromatography
Authors: Fanali Salvatore , Catarcini Paolo , Presutti Carla , Quaglia Maria G. , Righetti Pier‐Giorgio 
Published: March 2003

AbstractSeparation of hydroxy acid enantiomers was achieved by using capillary electrochromatography (CEC) employing a chiral stationary phase (CSP) based on MDL 63,246 (Hepta‐Tyr), a macrocyclic antibiotic of the teicoplanin family. The chiral selector was chemically bonded to 5 νm diol‐modified silica particles and the CSP mixed with amino silica (3:1 w/w) was packed into a 75 νm ID fused‐silica capillary. The CEC experiments were carried out by using an aqueous reversed‐phase mode for the enantiomeric resolution of hydroxy acid compounds. Good enantioresolution was achieved for mandelic acid (MA), m‐hydroxymandelic acid (m‐OH‐MA), p‐OH‐MA, and 3‐hydroxy‐4‐methoxymandelic acid (3‐OH‐4‐MeO‐MA). The CEC system was less enantioselective towards 2‐phenyllactic acid (2‐PhL) and 3‐PhL while mandelic acid methyl ester (MA‐Et‐Est) enantiomers were not resolved. Several experimental parameters, such as organic solvent type and concentration, buffer pH, capillary temperature, on enantioresolution factor, retention time, and retention factor were studied.