bluuebunny/crossref_metadata_2025_split huggingface dataset:
1,3‐Dialkyl‐ and 1,3‐Diaryl‐3,4,5,6‐tetrahydropyrimidin‐2‐ylidene Rhodium(i) and Palladium(II) Complexes: Synthesis, Structure, and Reactivity
Authors: Mayr Monika , Wurst Klaus , Ongania Karl‐Hans , Buchmeiser Michael R. 
Published: March 2004

AbstractThe synthesis of novel 1,3‐diaryl‐ and 1,3‐dialkylpyrimidin‐2‐ylidene‐based N‐heterocyclic carbenes (NHCs) and their rhodium(i) and palladium(II) complexes is described. The rhodium compounds bromo(cod)[1,3‐bis(2‐propyl)‐3,4,5,6‐tetrahydropyrimidin‐2‐ylidene]rhodium (7), bromo(cod)(1,3‐dimesityl‐3,4,5,6‐tetrahydropyrimidin‐2‐ylidene)rhodium (8) (cod=η4‐1,5‐cyclooctadiene, mesityl=2,4,6‐trimethylphenyl), chloro(cod)(1,3‐dimesityl‐3,4,5,6‐tetrahydropyrimidin‐2‐ylidene)rhodium (9), and chloro(cod)[1,3‐bis(2‐propyl)‐3,4,5,6‐tetrahydropyrimidin‐2‐ylidene]rhodium (10) were prepared by reaction of [{Rh(cod)Cl}2] with lithium tert‐butoxide followed by addition of 1,3‐dimesityl‐3,4,5,6‐tetrahydropyrimidinium bromide (3), 1,3‐dimesityl‐3,4,5,6‐tetrahydropyrimidinium tetrafluoroborate (4), 1,3‐di‐2‐propyl‐3,4,5,6‐tetrahydropyrimidinium bromide (6), and 1,3‐di‐2‐propyl‐3,4,5,6‐tetrahydropyrimidinium tetrafluoroborate, respectively. Complex 7 crystallizes in the monoclinic space group P21/n, and 8 in the monoclinic space group P21. Complexes 9 and 10 were used for the synthesis of the corresponding dicarbonyl complexes dicarbonylchloro(1,3‐dimesityl‐3,4,5,6‐tetrahydropyrimidin‐2‐ylidene)rhodium (11), and dicarbonylchloro[1,3‐bis(2‐propyl)‐3,4,5,6‐tetrahydropyrimidin‐2‐ylidene]rhodium (12). The wavenumbers ν(CO I)/ν(CO II) for 11 and 12 were used as a quantitative measure for the basicity of the NHC ligand. The values of 2062/1976 and 2063/1982 cm−1, respectively, indicate that the new NHCs are among the most basic cyclic ligands reported so far. Compounds 3 and 6 were additionally converted to the corresponding cationic silver(i) bis‐NHC complexes [Ag(1,3‐dimesityl‐3,4,5,6‐tetrahydropyrimidin‐2‐ylidene)2]AgBr2 (13) and [Ag{1,3‐bis(2‐propyl)‐3,4,5,6‐tetrahydropyrimidin‐2‐ylidene}2]AgBr2 (14), which were subsequently used in transmetalation reactions for the synthesis of the corresponding palladium(II) complexes Pd(1,3‐dimesityl‐3,4,5,6‐tetrahydropyrimidin‐2‐ylidene)22+(Ag2Br2Cl44−)1/2 (15) and Pd[1,3‐bis(2‐propyl)‐3,4,5,6‐tetrahydropyrimidin‐2‐ylidene)2]Cl2 (16). Complex 15 crystallizes in the monoclinic space group P21/c, and 16 in the monoclinic space group C2/c. The catalytic activity of 15 and 16 in Heck‐type reactions was studied in detail. Both compounds are highly active in the coupling of aliphatic and aromatic vinyl compounds with aryl bromides and chlorides with turnover numbers (TONs) up to 2 000 000. Stabilities of 15 and 16 under Heck‐couplings conditions were correlated with their molecular structure. Finally, selected kinetic data for these couplings are presented.
Synthesis and Supramolecular Association of Immobilized NCN‐Pincer Platinum(II) Complexes on Hyperbranched Polyglycerol Supports
Authors: Stiriba Salah‐Eddine , Slagt Martijn Q. , Kautz Holger , Klein Gebbink Robertus J. M. , Thomann Ralf , Frey Holger , van Koten Gerard 
Published: March 2004

AbstractPertosylation of hyperbranched polyglycerol (Mn=2000; Mw/Mn=1.3) followed by partial displacement of the tosyl groups with carboxylic acid functionalized NCN‐pincer platinum(II) complexes [PtI‐2,6‐(NMe2CH2)2C6H2‐4‐COOH], resulted in covalent attachment of the NCN‐pincer complexes to the polyglycerol. These functionalized hyperbranched macromolecules have been characterized by 1H, 13C, and 195Pt NMR, UV‐visible, and IR spectroscopy. The presence of Pt and I atoms renders them directly visible by transmission electron microscopy (TEM) without staining procedures, which offers images of associated hyperbranched macromolecules. TEM micrographs show disk‐shaped structures with a small size‐distribution (15–20 nm), and characteristic core‐shell ring structures. The thickness of the corona observed in TEM could be correlated with the substitution degree with pincer platinum moieties.
Hexasubstituted Donor–Acceptor Benzenes as Nonlinear Optically Active Molecules with Multiple Charge‐Transfer Transitions
Authors: Traber Boris , Wolff J. Jens , Rominger Frank , Oeser Thomas , Gleiter Rolf , Goebel Mark , Wortmann Rüdiger 
Published: March 2004

AbstractThe synthesis of three novel nonlinear optical (NLO) chromophores with threefold symmetry, namely 1,3,5‐tris(4‐N,N‐diethylaminophenyl)‐2,4,6‐tris(4‐nitrophenyl)benzene (3), 1,3,5‐tris(4‐N,N‐dihexylaminophenylbutadiynyl)‐2,4,6‐tris(4‐nitrophenyl)benzene (13) and 1,3,5‐tris(4‐N,N‐dihexylaminophenylethynyl)‐2,4,6‐tris(4‐nitrophenylethynyl)benzene (4 b), is reported. We used the [Co2(CO)8]‐catalysed trimerisation of 4‐N,N‐diethylamino‐4′‐nitrotolane (5) to prepare 3. The trimerisation experiment carried out with 1‐(4‐N,N‐diethylaminophenyl)‐6‐(4‐N,N‐nitrophenyl)hexatriyne (6) and [Rh(PPh3)3Cl] afforded 13. A stepwise approach was used to prepare 4 b. 1,3,5‐Trichloro‐2,4,6‐triiodobenzene (8 b) was coupled with 4‐nitrophenyl‐acetylene (14) under Pd0 catalysis to yield 1,3,5‐trichloro‐2,4,6‐tris(4‐nitrophenylethynyl)benzene (15). The coupling reaction of 15 with 4‐N,N‐dihexylaminophenylethynyltributylstannane (21) led to 4 b. X‐ray investigations on 3, 4 b and 13 confirmed the structural assignments and revealed that the peripheral aryl rings in 4 b are less twisted around the connecting bonds than in 3 and 13. A large second‐order polarisability (β) of 4 b relative to 3 and 13 was determined by hyper‐Rayleigh scattering (HRS). Compound 4 b represents an NLO chromophore with second‐order polarisabily among the highest obtained so far for two‐dimensional nondipolar NLO chromophores.
Chromo‐ and Fluororeactands: Indicators for Detection of Neutral Analytes by Using Reversible Covalent‐Bond Chemistry
Authors: Mohr Gerhard J. 
Published: March 2004

AbstractChromo‐ and fluororeactands are indicator dyes that allow the optical detection of electrically neutral analytes. Unlike complexing agents such as calixarenes, cyclodextrines or cyclophanes, reactands form a reversible covalent bond with the analyte molecule. This chemical reaction causes strong changes in absorbance or fluorescence. In this article reactands for analytes such as amines, alcohols, aldehydes, saccharides, carbon dioxide and sulfur dioxide are presented. Methods to enhance the sensitivity of the reactands as well as the operational and shelf lives of the corresponding optical sensors are discussed.
On the psychology of procedural justice: reactions to procedures of ingroup vs. outgroup authorities
Authors: Ståhl Tomas , Van Prooijen Jan‐Willem , Vermunt Riël 
Published: March 2004

AbstractTheorizing on procedural justice has assumed that people's reactions to outgroup authorities are to a large extent based on instrumental concerns. Therefore, attention is primarily directed to outcomes rather than procedures in encounters with outgroup authorities. In the current article we propose that in order for people dealing with outgroup authorities to be strongly affected by procedural fairness, the available outcome information should be ambiguous. Furthermore, we argue that people confronted with an outgroup authority react particularly negatively to unfair procedures that give them negative outcome expectancies. These patterns are not expected in encounters with ingroup authorities. Two experiments support our line of reasoning. The discussion focuses on the implications of these findings for the integration of theoretical perspectives on procedural justice. Copyright © 2004 John Wiley & Sons, Ltd.
Sources of respect: the effects of being liked by ingroups and outgroups
Authors: Ellemers Naomi , Doosje Bertjan , Spears Russell 
Published: March 2004

AbstractWe investigated the effects of ingroup and outgroup sources of respect, defined as positive social evaluations of self, on group members' emotional reactions and collective self‐esteem. We used both natural group memberships (Studies 1 and 2) and laboratory groups (Study 3). We expected that the positive effects of respect derived from an ingroup would not hold when derived from an outgroup source. In Study 1 (N = 294) respect was manipulated as deriving either from ingroup or outgroup. Although respect produced a positive emotional reaction irrespective of source, collective self‐esteem was only enhanced by an ingroup source. In Study 2 (N = 248), we investigated the concurrent effects of ingroup respect and outgroup respect. As in Study 1, ingroup and outgroup respect both produced positive emotional reactions, but collective self‐esteem was only affected by ingroup respect. Additionally, outgroup respect intensified the shame people experienced due to lack of ingroup respect. In Study 3 (N = 66), participants were immersed in experimental groups and ingroup and outgroup respect were manipulated orthogonally. Interactive effects of the two sources of respect indicated that high outgroup respect could not compensate for low ingroup respect, and if anything had an adverse effect. Copyright © 2004 John Wiley & Sons, Ltd.
Diffusion constant in gel electrophoresis at high fields
Authors: Krawczyk Małgorzata J. , Dulak Józef , Paściak Paweł , Kułakowski Krzysztof 
Published: March 2004

AbstractWe present new measurements of the diffusion constant D in standard (slab‐gel) electrophoresis of DNA at fields up to 10 V/cm. Molecules investigated are bacteriophages: T4 of length 173 kbp and λ of length 48.5 kbp cut by restriction enzyme HindIII. We show, that D increases with the molecule length for electric field E above 5 V/cm. The results are interpreted within the geometration model.
Precision and accuracy in fluorescent short tandem repeat DNA typing: Assessment of benefits imparted by the use of allelic ladders with the AmpFlSTR®Profiler Plus™ kit
Authors: Leclair Benoît , Frégeau Chantal J. , Bowen Kathy L. , Fourney Ron M. 
Published: March 2004

AbstractBase‐calling precision of short tandem repeat (STR) allelic bands on dynamic slab‐gel electrophoresis systems was evaluated. Data was collected from over 6000 population database allele peaks generated from 468 population database samples amplified with the AmpFlSTR®Profiler Plus™ (PP) kit and electrophoresed on ABD 377 DNA sequencers. Precision was measured by way of standard deviations and was shown to be essentially the same, whether using fixed or floating bin genotyping. However, the allelic ladders have proven more sensitive to electrophoretic variations than database samples, which have caused some floating bins of D18S51 to shift on occasion. This observation prompted the investigation of polyacrylamide gel formulations in order to stabilize allelic ladder migration. The results demonstrate that, although alleles comprised in allelic ladders and questioned samples run on the same gel should migrate in an identical manner, this premise needs to be verified for any given electrophoresis platform and gel formulation. We show that the compilation of base‐calling data is a very informative and useful tool for assessing the performance stability of dynamic gel electrophoresis systems, stability on which depends genotyping result quality.
Monomer surface modifications for rapid peptide analysis by capillary electrophoresis and capillary electrochromatography coupled to electrospray ionization‐mass spectrometry
Authors: Johannesson Nina , Wetterhall Magnus , Markides Karin E. , Bergquist Jonas 
Published: March 2004

AbstractIn this study, positively charged alkylaminosilyl monomers were used to modify the inner surface of fused silica capillaries, which subsequently were employed in capillary electrophoresis (CE) and capillary electrochromatography (CEC). The obtained surfaces yield a reversed electroosmotic flow (EOF) and have varying carbon chain lengths, that interact with the analytes and give chromatographic retention. The coating procedure is very simple and fast. The performance of the modified capillaries was evaluated regarding pH influence on EOF and chromatographic interactions. The experiments were conducted with UV and mass spectrometry (MS) and applied to the separation of various neuropeptides. The derivatized surfaces showed a linear (R2 ∼0.99) pH dependence with isoelectric points (pI) at 8.6–8.8. Rapid separations of peptide standards and a protein digest with efficiencies as high as 5×105 plates/m were performed.
Efficient and reproducible analysis of peptides by capillary electrophoresis using noncovalently bilayer‐coated capillaries
Authors: Catai Jonatan R. , Somsen Govert W. , de Jong Gerhardus J. 
Published: March 2004

AbstractThe usefulness of a noncovalent capillary coating consisting of two layers of oppositely charged polymers for the separation of peptides with capillary electrophoresis (CE) was studied. Capillaries were coated simply by subsequently flushing with solutions of 1% m/v Polybrene and 1% v/v poly(vinylsulfonate) (PVS) forming a bilayer, which showed to produce a strong and highly reproducible electroosmotic flow (EOF) at low pH. Using this coating in combination with a background electrolyte (BGE) containing sodium phosphate (pH 2.5) and 0.01% v/v PVS, initially broadened and overlapping peaks were obtained for some test peptides. By omitting the PVS from the BGE, the peak width and shape of the peptides improved resulting in baseline separation. A systematic study of the influence of the BGE composition showed that considerable further enhancement of the separation efficiency was achieved by increasing the ionic strength of the BGE. Using a BGE of 200 mM tris(hydroxymethyl)aminomethane (Tris)‐phosphate (pH 2.5) plate numbers for the peptides were in the 300 000–600 000 range and the relative standard deviation of the peptide migration times was less then 0.3% (n = 5). The use of Tris‐phosphate instead of sodium phosphate allowed the current to stay within acceptable limits when 30 kV was used as separation voltage. Overall, the bilayer coating showed a remarkable EOF repeatability, as well as long‐term stability. Compared to bare fused‐silica capillaries the intraday and interday repeatability of migration times was very favorable and coated capillaries could be used for over a month performing analyses with low and high ionic strength BGEs without any performance deterioration. The usefulness of the bilayer‐coated capillaries for the analysis of positively charged peptides was demonstrated by the fast and efficient separation of various closely related enkephalins and the baseline separation of an isomeric peptide/peptoid couple exhibiting efficiencies of over 550 000 plates.
Immobilized pH gradients as a first dimension in shotgun proteomics and analysis of the accuracy of pI predictability of peptides
Authors: Cargile Benjamin J. , Talley Dana L. , Stephenson James L. 
Published: March 2004

AbstractIn this work, we demonstrate the potential use of immobilized pH gradient isoelectric focusing as a first dimension in shotgun proteomics. The high resolving power and resulting reduction in matrix ionization effects due to analyzing peptides with almost the exact same physiochemical properties, represents a significant improvement in performance over traditional strong cation‐exchange first‐dimensional analysis associated with the shotgun proteomics approach. For example, using this technology, we were able to identify more than 6000 peptides and > 1200 proteins from the cytosolic fraction of Escherichia coli from approximately 10 μg of material analyzed in the second‐dimensional liquid chromatography‐tandem mass spectrometry experiment. Sample loads on the order of 1 mg can be resolved to 0.25 isoelectric point (pI) units, which make it possible to analyze organisms with significantly larger genomes/proteomes. Accurate pI prediction can then be employed using currently available algorithms to very effectively filter data for peptide/protein identification, and thus lowering the false‐positive rate for cross‐correlation‐based peptide identification algorithms. By simplifying the protein mixture problem to tryptic peptides, the effect of specific amino acids on pI prediction can be evaluated as a function of their position in the peptide chain.
Analysis of proteins stained by Alexa dyes
Authors: Huang Shijun , Wang Houyi , Carroll Christopher A. , Hayes Shirley J. , Weintraub Susan T. , Serwer Philip 
Published: March 2004

AbstractAlexa dye staining of proteins is used for the fluorescence microscopy of single particles that are sometimes multimolecular protein complexes. To characterize the staining, post‐staining determination must be made of which protein(s) in a complex have been Alexa‐stained. The present communication describes the use of sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE) for performing this determination. The Alexa‐stained proteins are observed directly in gels by illumination with an ultraviolet transilluminator. The test multimolecular particle is bacteriophage T7. The protein capsid of T7 is a multimolecular complex that has both external and internal proteins. SDS‐PAGE of Alexa‐stained bacteriophage T7 produces fluorescent capsid proteins each of which usually comigrates with an unstained protein. However, one Alexa‐induced modification of protein migration was observed by SDS‐PAGE. Mass spectrometry shows that the protein with modified migration is the major protein of the outer shell of the T7 capsid. The procedures used are generally applicable. The distribution of Alexa staining among T7 capsid proteins depends on the size of the dye molecule used. The larger the dye molecule is, the greater the preference for external proteins.
Capillary zone electrophoresis investigation of the interaction between heparin and granulocyte‐colony stimulating factor
Authors: Liang Aiye , He Xinya , Du Yuguang , Wang Keyi , Fung Yingsing , Lin Bingcheng 
Published: March 2004

AbstractThe interaction between standard heparin, low‐molecular‐weight heparin (LMWH), and granulocyte‐colony stimulating factor (G‐CSF) was studied by capillary zone electrophoresis. Both qualitative and quantitative characterizations of the heparin‐protein binding were determined. The binding constants of the two different groups of heparins with G‐CSF, calculated from the Scatchard plot by regression, were 4.805×105 M−1 and 4.579×105 M−1, respectively. The two binding constants measured are of the same order of magnitude at 105 M−1, indicating that LMWH contains most of the functional groups bound to G‐CSF by standard heparin.
Renal prothrombin: Quantification of mRNA using reverse transcription‐polymerase chain reaction in a rat model
Authors: Grover Phulwinder K. , Miyazawa Katsuhito , Ryall Rosemary Lyons 
Published: March 2004

AbstractAttempts to quantify renal prothrombin (PT) have failed due to interference of its hepatic counterpart. In order to gauge PT synthesized by the kidney, the expression of PT mRNA was compared in renal and hepatic tissues of rats. PT mRNAs were quantified, using quantitative competitive reverse transcription‐polymerase chain reaction (RT‐PCR), from RNA extracts of kidneys and livers of ten hooded Wistar rats. To control variations in sample preparation, the amount of PT transcript in each sample was normalized to the amount of its β‐actin transcript. The median ratio of PT to β‐actin transcript of 0.0011 (with a mean ± standard deviation (SD) of 0.0010 ± 0.0002, range 0.0007–0.0014) in the renal tissues was significantly (p ≤ 0.001) lower than its corresponding value of 0.3669 (with a mean ± SD of 0.3729 ± 0.0716, range 0.2718–0.4675) in the hepatic tissues. Thus, expression of PT mRNA in the rat kidney was almost 300‐fold less as compared with its expression in hepatic tissue.
Contactless conductivity detection of selected organic ions in on‐chip electrophoresis
Authors: Tanyanyiwa Jatisai , Abad‐Villar Eva M. , Hauser Peter C. 
Published: March 2004

AbstractThe detection of underivatized anionic sulfonates, carboxylates, amino acids, sugars, and artificial sweeteners, and of cationic dopamine, ephedrine, and metanephrine in microfabricated electrophoresis devices is demonstrated. This was achieved by high‐voltage contactless conductivity measurements with external electrodes. Poly(methyl methacrylate) chips with thin covers to enable sensitive contactless detection were used for most determinations but glass microchips had to be employed for amino acids and sugars. The plastic chips were found not be stable in the alkaline media required to render those two classes of species in the ionic form amenable for separation and detection. The reproducibility of peak area measurements was about 1% or better and the detection limits ranged between 1 and 30 μM for the different compounds examined.
On‐chip potential gradient detection with a portable capillary electrophoresis system
Authors: Feng Hua‐Tao , Wei Hong‐Ping , Y. Li Sam F. 
Published: March 2004

AbstractA portable chip‐CE system with potential gradient detection (PGD) was developed and applied to the determinations of alkali metals and alkaloids. The separation efficiency appeared to be satisfactory and nonaqueous capillary electrophoresis (NACE) proved to be applicable to PGD or conductivity detection. The power supplies, separation and detection were built on a device of 3 kg in weight. A branch channel near the end of the separation channel was designed to perform PGD and make the application of relatively high field strength possible. The study is the first report on the application of PGD on the microchip platform. The design of the chip‐CE system shows several advantages, such as simplicity, miniaturization and wide applicability.
Determination of oxidized and reduced glutathione, by capillary zone electrophoresis, in Brassica juncea plants treated with copper and cadmium
Authors: Mendoza Jorge , Soto Paula , Ahumada Inés , Garrido Tatiana 
Published: March 2004

AbstractA rapid method of capillary zone electrophoresis is described to determine the oxidized (GSSG) and reduced (GSH) form of glutathione in plant tissue. In order to separate both analytes in a fused‐silica capillary, the pH and composition of the electrolyte solution were optimized. The electrolyte composition was 100 mmol/L, borate 25 mmol/L Tris, and 0.2% w/v metaphosphoric acid (MPA), pH 8.2. Some instrumental conditions used to run the samples were hydrostatic injection for 30 s, 30 kV applied voltage, and UV detection (185 nm) at 25°C. Linearity and useful range obtained for the calibration curves were optimum, with correlation coefficients about 0.999 in the 0–120 μmol/L range. The migration time was highly reproducible, less than 5 min being afforded to run a sample. Electrolyte buffer and samples required a careful pH control for optimal separation of both analytes. This aspect constitutes a critical analytical step when acids are used in the procedure for sample preparation. Simultaneous analysis of GSH and GSSG may provide a useful tool for comparative studies of plants in order to select those species with a potential capacity for detoxification from toxic elements or those appearing promising from phytoremediation for these elements.