bluuebunny/crossref_metadata_2025_split huggingface dataset:
Programming Heteropolymetallic Lanthanide Helicates: Thermodynamic Recognition of Different Metal Ions Along the Strands
Authors: Floquet Sébastien , Borkovec Michal , Bernardinelli Gérald , Pinto André , Leuthold Luc‐Alexis , Hopfgartner Gérard , Imbert Daniel , Bünzli Jean‐Claude G. , Piguet Claude 
Published: March 2004

AbstractUnder stoichiometric conditions, the segmental tris‐tridentate ligand L9 assembles with two different lanthanide metal ions Ln1 and Ln2 (Ln1, Ln2=La, Nd, Sm, Eu, Yb, Lu, Y) to give mixtures of the heterotrimetallic triple‐stranded helicates [(Ln1)x(Ln2)3−x(L9)3]9+ (x=0–3) in acetonitrile. The combination of qualitative (ESI‐MS) and quantitative (1H NMR) speciations provides a set of thermodynamic data that were analysed with various statistical chemical models. A satisfying description requires the consideration of different affinities for the terminal N6O3 sites (k${{{\rm t}\hfill \atop {\rm Ln}\hfill}}$) and for the central N9 site (k${{{\rm c}\hfill \atop {\rm Ln}\hfill}}$) for each specific lanthanide. The nontrivial dependence of these parameters on the ionic radius provides size‐discriminating effects that favour the formation of heterotrimetallic helicates in which the central site is occupied by the larger metal of the pair. Combining the latter enthalpic driving forces with entropic contributions due to specific stoichiometric conditions allows partial selection (i.e., programming) of a specific heterotrimetallic species in solution, which can be isolated by crystallisation, as demonstrated for [Eu2.04La0.96(L9)3](CF3SO3)9(CH3NO2)9 (1, Eu2.04La0.96C207H222N48O51S9F27, monoclinic, P21/c, Z=4) in which the cation [EuLaEu(L9)3]9+ is the major component in the crystal. The scope and limitation of this approach is discussed together with the conditions for explicitly considering intermetallic interaction parameters uLn1Ln2 in more sophisticated chemical models.
Photocontrolled Release and Uptake of a Porphyrin Guest by Dithienylethene‐Tethered β‐Cyclodextrin Host Dimers
Authors: Mulder Alart , Juković Amela , van Leeuwen Fijs W. B. , Kooijman Huub , Spek Anthony L. , Huskens Jurriaan , Reinhoudt David. N. 
Published: March 2004

AbstractTwo photoswitchable dithienylethene‐tethered β‐cyclodextrin dimers were synthesized to function as host molecules with an externally controllable binding affinity. The cyclodextrin cavities of these dimers are linked through their secondary sides by a photochromic dithienylethene unit that is connected to the secondary rim either directly (4) or through propyl spacers (9). Irradiation with light switches these dimers between a relatively flexible (open) and a rigid (closed) form. The binding properties of the dimers depend on the configuration of the dithienylethene spacer, as is shown by microcalorimetry performed with tetrakis‐sulfonatophenyl porphyrin (TSPP) as a guest molecule. The differences in binding properties are most pronounced for the more rigid dimer 4, which binds TSPP 35 times more strongly in the open form (4 a) than in the closed form (4 b). The values found for the enthalpy of binding (ΔH°) indicate that this difference in binding is due to the loss of cooperativity between the two β‐cyclodextrin cavities in the closed form. Molecular modeling shows that 4 b is not able to bind TSPP effectively in both cyclodextrin cavities. The open and closed forms of the more flexible dimer 9 show no substantial difference in their binding of TSPP. Thermodynamic values indicative of strong binding of TSPP by two β‐cyclodextrin cavities were measured for both forms of the dimer, and molecular modeling confirms that both are flexible enough to tightly bind TSPP. The binding differences between the forms of dimer 4 allow the photocontrolled release and uptake of TSPP, which renders control of the ratio of complexed to free TSPP in solution possible.
Sterically Hindered Triacylglycerol Analogues as Potent Inhibitors of Human Digestive Lipases
Authors: Constantinou‐Kokotou Violetta , Magrioti Victoria , Verger Robert 
Published: March 2004

AbstractA novel class of inhibitors of human digestive lipases have been developed. Various sterically hindered triacylglycerols based on 2‐methyl‐ and 2‐butylglycerol, and/or 2‐methyl fatty acids were synthesized. The triacylglycerol analogues were tested for their ability to form stable monomolecular films at the air/water interface by recording their surface‐pressure/molecular‐area compression isotherms. The inhibition of human pancreatic and gastric lipases by the sterically hindered triacylglycerol analogues was studied by using the monolayer technique with mixed films of 1,2‐dicaprin, which contained variable proportions of each inhibitor. Triolein analogues that contain a butyl group at the 2‐position of the glycerol backbone or methyl groups both at the 2‐position of glycerol, and the α‐position of each oleic acid residue were potent inhibitors; this caused a 50 % decrease in HPL activity at 0.003 molar fraction.
Synthesis and Esterolytic Activity of Catalytic Peptide Dendrimers
Authors: Lagnoux David , Delort Estelle , Douat‐Casassus Céline , Esposito Annamaria , Reymond Jean‐Louis 
Published: March 2004

AbstractPeptide dendrimers were prepared by solid‐phase peptide synthesis. Monomeric dendrimers were first obtained by assembly of a hexapeptide sequence containing alternate standard α‐amino acids with diamino acids as branching units. The monomeric dendrimers were then dimerized by disulfide‐bridge formation at the core cysteine. The synthetic strategy is compatible with functional amino acids and different diamino acid branching units. Peptide dendrimers composed of the catalytic triad amino acids histidine, aspartate, and serine catalyzed the hydrolysis of N‐methylquinolinium salts when the histidine residues were placed at the outermost position. The dendrimer‐catalyzed hydrolysis of 7‐isobutyryl‐N‐methylquinolinium followed saturation kinetics with a rate constant of catalysis/rate constant without catalysis (kcat/kuncat) value of 3350 and a rate constant of catalysis/Michaelis constant (kcat/KM) value 350‐fold larger than the second‐order rate constant of the 4‐methylimidazole‐catalyzed reaction; this corresponds to a 40‐fold rate enhancement per histidine side chain. Catalysis can be attributed to the presence of histidine residues at the surface of the dendrimers.
Perceived in‐group threat as a factor moderating the influence of in‐group norms on discrimination against foreigners
Authors: Falomir‐Pichastor Juan Manuel , Muñoz‐Rojas Daniel , Invernizzi Federica , Mugny Gabriel 
Published: March 2004

AbstractWithin the framework of an intergroup relations paradigm, three studies analysed the role of in‐group threat in intergroup discrimination and the influence of in‐group norms on intergroup discrimination. The first study showed that perceived socio‐economic threat underlies Swiss nationals' prejudice and discrimination toward foreigners in Switzerland. The second and third studies experimentally tested the hypotheses, first, that variations in perception of in‐group threat will produce change in initial discrimination, and, second, that the influence of an in‐group norm (pro‐ vs. anti‐ discriminatory) is moderated by the perception of in‐group threat. In support of these predictions, results of both studies indicated that discrimination was reduced when perceived in‐group threat was low. However, the anti‐discriminatory in‐group norm reduced discrimination only when perceived in‐group threat was low. No influence was observed for the pro‐discriminatory in‐group norm. Copyright © 2004 John Wiley & Sons, Ltd.
When the past becomes history: effects of temporal order on explanations of trends
Authors: Teigen Karl Halvor 
Published: March 2004

AbstractWhen people are asked to ‘explain’ a time series consisting of population statistics, they will suggest factors responsible for later events rather than for earlier events. This is shown in Experiment 1 for pairs of events and in Experiment 2 for triads of events with one deviant member. When the deviant statistic is the most recent one, it will in most cases be singled out for explanation. When it comes first, it is rarely explained, but accepted as a given fact. This is seen as an instance of the temporal order effect, where the first event in a pair or a series is taken for granted, whereas later events are considered more ‘mutable’, i.e. they could have been different. In line with this, later statistics are considered to be more in need of support from additional information than earlier statistics (Experiment 3). The focus on temporally later events can be distinguished from other primacy and recency effects by being due to chronological order, rather than order of presentation. Copyright © 2004 John Wiley & Sons, Ltd.
Back to caring after being hurt: the role of forgiveness
Authors: Karremans Johan C. , Van Lange Paul A. M. 
Published: March 2004

AbstractWhile the topic of forgiveness has only recently started to receive empirical attention, little research has been conducted to examine the notion that forgiveness predicts pro‐relationship responses, motivated by a willingness to set aside personal well‐being to enhance the well‐being of the partner or relationship. The purpose of the present research was to examine whether forgiveness predicts pro‐relationship responses, and whether it does so above and beyond commitment to the offender. Consistent with hypotheses, three studies revealed that forgiveness is significantly associated with (a) willingness to accommodate (i.e. to respond constructively rather than destructively when the partner has engaged in a potentially destructive act), (b) willingness to sacrifice, and (c) level of intended cooperation. Moreover, these associations were independent of commitment to the offender, providing initial evidence for the unique role of forgiveness in understanding pro‐relationship motivation and behaviour. Finally, the results of Study 3 suggested that forgiveness restores, rather than increases, levels of pro‐relationship motivation, compared to baseline levels of pro‐relationship motivation. Copyright © 2004 John Wiley & Sons, Ltd.
Who's the one in trouble? experimental evidence for a ‘psychic state’ bias in lineups
Authors: Weigold Arne , Wentura Dirk 
Published: March 2004

AbstractIn two experiments, a bias in lineups was examined, which has mostly been ignored in previous research. The psychic state of the suspects differs from the state of the fillers, in that they face a situation that can lead to personal loss (if they are identified) or relief (if they are not identified). This state might result in detectable behavioural cues, thus making the lineup unfair. Lineups were conducted with randomly chosen mock suspects who were promised money if they were not identified. Lineup samples were recorded on videotape once before the selection of the mock suspect (serving as a control) and once afterwards. The probability of identification of the mock suspect was significantly increased in the latter compared to the former condition. Copyright © 2004 John Wiley & Sons, Ltd.
High‐throughput single nucleotide polymorphism typing by fluorescent single‐strand conformation polymorphism analysis with capillary electrophoresis
Authors: Doi Kent , Doi Hitomi , Noiri Eisei , Nakao Akihide , Fujita Toshiro , Tokunaga Katsushi 
Published: March 2004

AbstractIn this study, we performed high‐throughput and precise single nucleotide polymorphism (SNP) typing by fluorescent capillary electrophoresis single‐strand conformation polymorphism (CE‐SSCP) analysis. A system composed of a multicapillary DNA analyzer, a newly developed sieving matrix, four different colors of fluorescent labels, and a multiplex polymerase chain reaction (PCR) enabled low‐cost and highly reliable SNP typing. Moreover, this system enabled the estimation of SNP allele frequencies using pooled DNA samples, which should be beneficial for large‐scale association studies. Thus, fluorescent CE‐SSCP analysis is a useful method for large‐scale SNP typing.
Different binding thermodynamics of Ni2+, Cu2+, and Zn2+ to bacitracin A1 determined by capillary electrophoresis
Authors: Castagnola Massimo , Rossetti Diana V. , Inzitari Rosanna , Lupi Alessandro , Zuppi Cecilia , Cabras Tiziana , Fadda Maria B. , Onnis Giuseppina , Petruzzelli Raffaele , Giardina Bruno , Messana Irene 
Published: March 2004

AbstractThermodynamics of the binding of Ni2+, Cu2+ and Zn2+ to bacitracin A1 was studied by capillary electrophoresis measuring the peptide effective mobility at different pH in the presence of increasing concentration of the three ligands. The affinity follows the order Ni2+ > Cu2+ > Zn2+, with association constant values of (2.3 ± 0.1)×104, (4.9 ± 0.2)×103, and (1.5 ± 0.1)×103 M−1, respectively. The only model able to rationalize mobility data implies that metal ion binds to the P0 peptide form. Moreover, mobility values indicated a change of bacitracin A1 acidic properties on Ni2+ and Cu2+ binding, with a shift of the pKa of N‐terminal Ile‐1 from 7.6 to about 5 and of the pKa of the δ‐amino group of D‐Orn‐7 from 9.7 to about 7. Even though on Zn2+ binding a shift of the N‐terminal Ile‐1 pKa was observed, restrictions in the pH range suitable for investigation, due to precipitation phenomena, did not allow establish if the shift of D‐Orn‐7 lateral chain pKa also occurred. Nonetheless, if present, the shift should be limited to the 7.8–9.7 range. Mobility data indicated that the Stokes radius of the complexes is ca. 3 Å lower than that of the free peptide. The present results indicate that metal‐ion binding to bacitracin A1 is more complex than previously assumed.
Capillary electrophoresis analysis of glucooligosaccharide regioisomers
Authors: Joucla Gilles , Brando Thérèse , Remaud‐Simeon Magali , Monsan Pierre , Puzo Germain 
Published: March 2004

AbstractComplex gluco‐oligosaccharide mixtures of two regioisomer series were successfully separated by CE. The gluco‐oligosaccharide series were synthesized, employing a dextransucrase from Leuconostoc mesenteroides NRRL B‐512F, by successive glucopyranosyl transfers from sucrose to the acceptor glucose or maltose. The glucosyl transfer to both acceptors, occurring through the formation of α1→6 linkages, differed for the two series only in the glucosidic bond to the reducing end namely α1→6 or α1→4 bond for glucose or maltose acceptor, respectively. Thus, the combination of the two series results in mixed pairs of gluco‐oligosaccharide regioisomers with different degrees of polymerization (DP). These regioisomer series were first derivatized by reductive amination with 9‐aminopyrene‐1,4,6‐trisulfonate (APTS). Under acidic conditions using triethyl ammonium acetate as electrolyte, the APTS‐gluco‐oligosaccharides of each series were separated enabling unambiguous size determination by coupling CE to electrospray‐mass spectrometry. However, neither these acidic conditions nor alkaline buffer systems could be adapted for the separation of the gluco‐oligosaccharide regioisomers arising from the two combined series. By contrast, increased resolution was observed in an alkaline borate buffer, using differential complexation of the regioisomers with the borate anions. Such conditions were also successfully applied to the separation of glucodisaccharide regioisomers composed of α1→2, α1→3, α1→4, and α1→6 linkages commonly synthesized by glucansucrase enzymes.
Mixed cationic/anionic surfactants for semipermanent wall coatings in capillary electrophoresis
Authors: Wang Chuanzhong , Lucy Charles A. 
Published: March 2004

AbstractMixtures of the cationic surfactant cetyltrimethylammonium bromide (CTAB) with the anionic surfactant sodium dodecyl sulfate (SDS) form more stable coatings in fused‐silica capillaries than CTAB alone. The reversed electroosmotic flow (EOF) generated by CTAB/SDS mixtures remains stable for over 80 min after removal of the surfactants from the buffer. Enhanced stability (relative to CTAB alone) was found even when the ratio of SDS to CTAB was as low as 1%. This greater coating stability is attributed to the structural transition from adsorbed micelle to bilayer, which is induced by addition of SDS. Separation of a mixture of basic proteins yielded efficiencies of 364 000–562 000 plates/m and recoveries ranging from 85% to 98%. Migration time reproducibility was less than 0.9% relative standard deviation (RSD) from run to run and less than 2.6% RSD from day to day.
Determination of the DNA methylation level in tumor cells by capillary electrophoresis and laser‐ induced fluorescence detection
Authors: Wirtz Michaela , Stach Dirk , Kliem Hans‐Christian , Wiessler Manfred , Schmitz Oliver J. 
Published: March 2004

AbstractAn analytical method to determine the genome‐wide DNA methylation in only 100 ng DNA is presented. The analysis is based on DNA isolation and hydrolysis followed by derivatization of the 2'‐desoxyribonucleoside‐3'‐monophosphates with a fluorescence dye (4,4‐difluoro‐5,7‐dimethyl‐4‐bora‐3a,4a‐diaza‐s‐indacene‐3‐propionyl ethylene diamine hydrochloride, Bodipy FL EDA). The separation of the derivatives was carried out by micellar electrokinetic chromatography, and laser‐induced fluorescence was used for detection. To calculate the methylation level, the derivatization factor and the quantum yields of the Bodipy conjugates of 2'‐desoxycytidine‐3'‐monophosphate (dCMP) and 2'‐desoxy‐5‐methylcytidine‐3'‐monophosphate (5m‐dCMP) were determined by measurement of methylated Lambda DNA. The assignment was made by cochromatography with the synthesized and characterized standard compound 5m‐dCMP. After optimization of the method it was possible to determine the methylation level in 100‐ng DNA samples with a standard deviation of less than 5%.
Search for serum protein‐binding disaccharides and disaccharide‐binding serum proteins by affinity capillary electrophoresis
Authors: Taga Atsushi , Yamamoto Yuka , Maruyama Rie , Honda Susumu 
Published: March 2004

AbstractThe potential use of affinity capillary electrophoresis in a microscale search for mutually interacting substances in biological fluid is demonstrated. Some disaccharides, especially gentiobiose (Gen), derivatized with 1‐phenyl‐3‐methyl‐5‐pyrazolone, caused peak retardation when electrophoresed in a neutral running buffer, containing human serum. Gen, the most significantly retarded disaccharide, was converted to its negatively charged bis‐mercaptoethanesulfonate derivative (MerESGen), and a serum sample was analyzed in a neutral buffer containing the derivatized disaccharide. Two peaks, belonging to the β‐globulin fraction, were found to be remarkably retarded in the buffer containing MerES‐Gen in a concentration‐dependent way. These findings prove an interaction between disaccharides and serum proteins.
Ultraviolet sealing and poly(dimethylacrylamide) modification for poly(dimethylsiloxane)/glass microchips
Authors: Chen Lin , Ren Jicun , Bi Rui , Chen Di 
Published: March 2004

AbstractSimple sealing methods for poly(dimethylsiloxane) (PDMS)/glass‐based capillary electrophoresis (CE) microchips by UV irradiation are described. Further, we examined the possibility to modify the inner surface of separation channels, using polymethylacrylamide (PDMA) as a dynamic coating reagent. The surface properties of native PDMS, UV‐irradiated PDMS, and PDMA‐coated PDMS were systematically studied by atomic force microscopy (AFM), infrared absorption by attenuated total reflection infrared (ATR‐IR) spectroscopy, and contact angle measurement. We found that PDMA forms a stable coating on PDMS and glass surfaces, eliminating the nonhomogeneous electroosmotic flow (EOF) in channels on PDMS/glass microchips, and improving the hydrophilicity of PDMS surfaces. Mixtures of flavin mononucleotide (FMN), flavin adenine dinucleotide (FAD), and fluorescein were separated in 35 s using PDMA‐coated PDMS/glass microchips. A high efficiency of theoretical plates with at least 1365 (105 000 N/m) and a good reproducibility with relative standard deviations (RSD) below 4% in five successive separations were achieved.
Plasma thiols redox status by laser‐induced fluorescence capillary electrophoresis
Authors: Carru Ciriaco , Deiana Luca , Sotgia Salvatore , Pes Giovanni Mario , Zinellu Angelo 
Published: March 2004

AbstractHigh concentrations of total plasma thiols such as cysteine and homocysteine are important risk factors for atherosclerosis and cardiovascular diseases. We have recently described a new laser‐induced fluorescence capillary electrophoresis (CE‐LIF) method to measure total plasma thiols, in which the baseline separation of cysteinylglycine, homocysteine, cysteine, and glutathione was achieved by adding the organic base N‐methyl‐D‐glucamine to the run buffer. However, because the active fractions of homocysteine and cysteine responsible for vascular injuries are still unknown, research calls for a set up of methods able to analyze different forms of plasma thiols. In this paper, we present an improvement of our previous method that allows the measurement of different thiol forms. Total, reduced, and free thiols were measured by varying the order of disulfide reduction with tributylphosphine and proteins precipitation with 5‐sulfosalicylic acid. After derivatization with 5‐iodoacetamidofluorescein, samples were separated and measured by CE‐LIF using a phosphate/borate buffer in the presence of 75 mmol/L N‐methyl‐D‐glucamine. Oxidized thiols and protein bound thiols were calculated by difference, free minus reduced and total minus free form, respectively. Linearity, reproducibility, analytical recovery, and sensitivity were evaluated. The assay was used to measure the thiols redox status in 15 plasma samples from healthy volunteers.
Rapid analysis of genetically modified organisms by in‐house developed capillary electrophoresis chip and laser‐induced fluorescence system
Authors: Obeid Pierre J. , Christopoulos Theodore K. , Ioannou Penelope C. 
Published: March 2004

AbstractA microfabricated, inexpensive, reusable glass capillary electrophoresis chip and a laser‐induced fluorescence system were developed in‐house for the rapid DNA‐based analysis of genetically modified organisms (GMOs). The 35S promoter sequence of cauliflower mosaic virus and the terminator of the nopaline synthase (NOS) gene from Agrobacterium tumefaciens were both detected since they are present in most genetically modified organisms. The detection of genetically modified soybean in the presence of unaltered soybean was chosen as a model. Lectin, a plant‐specific gene, was also detected for confirmation of the integrity of extracted DNA. The chip was composed of two glass plates, each 25×76 mm, thermally bonded together to form a closed structure. Photomasks with cross‐topology were prepared rapidly by using polymeric material instead of chrome plates. The widths of the injection and separation channels were 30 and 70 μm, respectively, the effective separation length 4.5 cm. The glass slide was etched to a depth of 30 μm for both the injection and separation channel. The cost of the chip was less than 1 $ and required 2 days for photomask preparation and microfabrication. The separation and detection of polymerase chain reaction‐amplified NOS, 35S, and lectin sequences (180, 195, and 181 bp, respectively) was completed in less than 60 s. As low as 0.1% GMO content was detectable by the proposed system after 35 and 40 amplification cycles for 35S and NOS, respectively, using 25 ng of extracted DNA as starting material. This corresponds to only 20 genome copies of genetically modified soybean.