bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stacking and separation of enantiomers by acetonitrile‐salt mixtures in micellar electrokinetic chromatography
Authors: Choy Tom M. H. , Chan Wing‐Hong , Lee Albert W. M. , Huie Carmen W. 
Published: September 2003

AbstractThe feasibility of employing the “acetonitrile stacking” method in micellar electrokinetic chromatography (MEKC) for the on‐line preconcentration and separation of enantiomers is demonstrated for the first time. The effects of various experimental parameters on the stacking and separation of three different pairs of optical isomers, i.e., two substituted naphthyl enantiomers and one dansylated‐DL‐amino acid, were examined. In particular, the effectiveness of the addition of acetonitrile and salt in the sample matrix to induce narrowing of the analyte bands was investigated in the presence of sodium cholate as the chiral surfactant micelle in the separation buffer. For example, it was found that the presence of both acetonitrile and 1% NaCl in the sample matrix (volume ratio = 2:1) led to a significant improvement of the peak height and resolution for the MEKC separation of a pair of R(−)/S(+)‐1,1'‐binaphthyl diyl hydrogen phosphate enantiomers when the injection sample size was relatively large (e.g., 12% capillary volume). Furthermore, the feasibility of combining salting‐out solvent extraction (off‐line) and acetonitrile stacking (on‐line) as a novel approach for sample preconcentration in capillary electrophoresis was also demonstrated.
Discrete wavelets transform for signal denoising in capillary electrophoresis with electrochemiluminescence detection
Authors: Cao Weidong , Chen Xiaoyan , Yang Xiurong , Wang Erkang 
Published: September 2003

AbstractDiscrete wavelets transform (DWT) was applied to noise on removal capillary electrophoresis‐electrochemiluminescence (CE‐ECL) electropherograms. Several typical wavelet transforms, including Haar, Daublets, Coiflets, and Symmlets, were evaluated. Four types of determining threshold methods, fixed form threshold, rigorous Stein's unbiased estimate of risk (rigorous SURE), heuristic SURE and minimax, combined with hard and soft thresholding methods were compared. The denoising study on synthetic signals showed that wave Symmlet 4 with a level decomposition of 5 and the thresholding method of heuristic SURE‐hard provide the optimum denoising strategy. Using this strategy, the noise on CE‐ECL electropherograms could be removed adequately. Compared with the Savitzky‐Golay and Fourier transform denoising methods, DWT is an efficient method for noise removal with a better preservation of the shape of peaks.
Enantioseparation of phenothiazines in cyclodextrin‐modified capillary zone electrophoresis: Reversal of migration order
Authors: Lin Ching‐Erh , Liao Wei‐Ssu , Chen Kuo‐Hsing 
Published: September 2003

AbstractEnantioseparations of phenothiazines with γ‐cyclodextrin (γ‐CD) as a chiral selector were investigated using citrate and phosphate buffer electrolytes at pH 3.0. Reversal of the enantiomer migration order of promethazine, ethopropazine, and trimeprazine was observed by varying γ‐CD concentration in the range of 5–9 mM, 2.5–4.5 mM and 1.5–2.8 mM, respectively, using 100 mM citrate buffer at pH 3.0. As in the case of β‐CD, the (+)‐enantiomers of phenothiazines possess greater binding strength to γ‐CD than the (−)‐enantiomers. The evaluation of the binding constants and limiting mobility of the complexes formed between the enantiomers of phenothiazines and γ‐CD reveals that the binding strength of phenothiazines to γ‐CD and the differences in the binding constants and limiting mobility of the complexes are responsible for the enantiomer migration reversal. Both the binding constants and limiting mobility of the complexes between the (+)‐enantiomers of phenothiazine and γ‐CD are greater than those of the corresponding (−)‐enantiomers in a citrate buffer, while the binding constants of the complexes primarily determined the migration order of the enantiomers in a phosphate buffer. Compared with the results obtained using a phosphate buffer, we may conclude that citrate buffer which involves competitive complexation with chiral selector plays a significant role in the enantiomer migration reversal.
In vivo simultaneous monitoring of γ‐aminobutyric acid, glutamate, and L‐aspartate using brain microdialysis and capillary electrophoresis with laser‐induced fluorescence detection: Analytical developments and in vitro/in vivo validations
Authors: Sauvinet Valérie , Parrot Sandrine , Benturquia Nadia , Bravo‐Moratón Eva , Renaud Bernard , Denoroy Luc 
Published: September 2003

Abstractγ‐Aminobutyric acid (GABA), glutamate (Glu), and L‐aspartate (L‐Asp) are three major amino acid neurotransmitters in the central nervous system. In this work, a method for the separation of these three neurotransmitters in brain microdialysis samples using a commercially available capillary electrophoresis (CE) system has been developed. Molecules were tagged on their primary amine function with the fluorogene agent naphthalene‐2,3‐dicarboxaldehyde (NDA), and, after separation by micellar electrokinetic chromatography, were detected by laser‐induced fluorescence using a 442 nm helium‐cadmium laser. The separation conditions for the analysis of derivatized neurotransmitters in standard solutions and microdialysates have been optimized, and this method has been validated on both pharmacological and analytical basis. The separation of GABA, Glu, and L‐Asp takes less than 10 min by using a 75 mmol/L borate buffer, pH 9.2, containing 70 mmol/L SDS and 10 mmol/L hydroxypropyl‐β‐cyclodextrin and + 25 kV voltage. The detection limits were 3, 15 nmol/L and, 5 nmol/L for GABA, Glu, and L‐Asp, respectively. Moreover, submicroliter samples can be analyzed. This method allows a simple, rapid and accurate measurement of the three amino acid neurotransmitters for the in vivo brain monitoring using microdialysis sampling.
Capillary electrochromatography and preconcentration of neutral compounds on poly(dimethylsiloxane) microchips
Authors: Ro Kyung Won , Chang Woo‐Jin , Kim Ho , Koo Yoon‐Mo , Hahn Jong Hoon 
Published: September 2003

AbstractCapillary electrochromatography (CEC) and preconcentration of neutral compounds have been realized on poly(dimethylsiloxane) (PDMS) microchips. The channels are coated with polyelectrolyte multilayers to avoid absorption of hydrophobic analytes into PDMS. The structures of a microchip include an injector and a bead chamber with integrated frits, where the particles of the stationary phase are completely retained. Dimensions of the frit structures are 25 μm×20 μm, and the space between the structures is 3 μm. A neutral compound, BODIPY, that is strongly absorbed into native PDMS, is successfully and selectively retained on octadecylsilane‐coated silica beads in the bead chamber with a concentration enhancement of up to 100 times and eluted with elution buffer solution containing 70% acetonitrile. Preconcentrations and CEC separations of coumarins have been conducted with the same device and achieved complete separations in less than 50 s.
Rapid separation and laser‐induced fluorescence detection of mutated DNA by capillary electrophoresis in a self‐coating, low‐viscosity polymer matrix
Authors: Du Ming , Flanagan James H. , Lin Bingcheng , Ma Yinfa 
Published: September 2003

AbstractThe detection of point and other simple mutations in DNA is important for cancer research and diagnosis and other biological studies. Capillary electrophoresis has been successfully used for separating DNA fragments. However, a low‐viscosity polymer sieving buffer for DNA separation with on‐line coating has never been reported. In this paper, a new method using capillary electrophoresis with on‐line coating and laser‐induced fluorescence detection (CE‐LIF) for screening for point or simple DNA mutations has been demonstrated. The method uses an on‐line dynamic coating technique that increases capillary lifetime and analysis reproducibility, and employs a low‐viscosity polymer solution, which allows the user to rinse the capillary rapidly and refill with polymer solution easily. Experiments proved that the additives in the separation buffer for on‐line capillary coating do not affect the separation efficiency of the running buffer, and do not interfere with the formation of hydrogen‐bonded network between boric acid, mannitol and hydroxypropylmethylcellulose polymers. The stability of the dynamically coated capillary was quantitatively studied; the capillary lifetime was increased 6‐ to 7‐fold compared with that of permanently coated CE columns. Standard DNA fragments containing mutations, with sizes of 209, 219, and 338 bps, were successfully separated and detected with this system, after the mutated DNA fragments were cleaved by CEL‐I endonuclease. The technique is very sensitive for the size‐separation of low‐range, middle‐range, and high‐range DNA fragments. Results were compared with the HPLC methods developed by Transgenomic, Inc. and were in good agreement. The method should be applicable to mutation detection for all relevant biological and clinical studies. The factors influencing separations and the stability of dynamic capillary coatings are also discussed in the paper.
Optimized preparation of poly(styrene‐co‐ divinylbenzene‐co‐methacrylic acid) monolithic capillary column for capillary electrochromatography
Authors: Jin Wenhai , Fu Hongjing , Huang Xiadong , Xiao Hua , Zou Hanfa 
Published: September 2003

AbstractPreparation of a poly(styrene‐co‐divinylbenzene‐co‐methacrylic acid) monolithic stationary phase for the use in capillary electrochromatography (CEC) has been improved by optimizing the polymerization conditions. It is observed that the reaction time strongly affects column efficiency, while the proportion of isooctane in porogen influences peak symmetry of some solutes seriously. The lifetime of the monolithic columns prepared mainly depends on the pH of buffers used. Reproducibility of electroosmotic flow (EOF) from batch to batch columns are lower than 2.8% relative standard deviation. Unlike other types of capillary electrochromatographic monoliths, a pH‐dependent EOF was observed on this type of column. Separation of various types of compounds including aromatic hydrocarbons, hormones, anilines, basic pharmaceuticals, and peptides was achieved. The facile preparation and wide application of this monolithic column may make styrene‐based polymer a potential stationary phase in CEC.
Surface grafting of glycidyl methacrylate on silica gel and polyethylene beads
Authors: Choi Seong‐Ho , Hwang Young‐Mi , Ryoo Jae Jeong , Lee Kwang‐Pill , Ohta Kazutoku , Takeuchi Toyohide , Jin Ji‐Ye , Fujimoto Chuzo 
Published: September 2003

AbstractSurface grafting of glycidyl methacrylate (GMA) on silica gel and a polyethylene bead was performed by radical polymerization and radiation‐induced polymerization, respectively, in order to improve softness. Subsequently, diethylene triamine (DETA), triethylene tetraamine (TETA), and iminodiacetic acid (IDA) were introduced to the grafted GMA for use as affinity columns. The efficiency of the affinity column was investigated by use of bovine serum albumin (BSA) and hemoglobin (Hb) as model proteins. The affinity degree of BSA was higher than Hb for the DETA and TETA column, whereas the affinity degree of Hb was higher than BSA for the IDA column supported by silica gel. The affinity degree of BSA was higher than Hb for the DETA and TTA column supported by polyethylene (PE) beads.
Formation of S‐[2‐carboxy‐1‐(1H‐imidazol‐4‐yl) ethyl]glutathione, a new metabolite of L‐histidine, from cis‐urocanic acid and glutathione by the action of glutathione S‐transferase
Authors: Kinuta Masahiro , Kinuta Keiko , Yamada Hiroshi , Abe Tadashi , Yoshida Yumi , Araki Kenta , Li Shun‐Ai , Otsuka Atsushi , Nakanishi Akira , Moriyama Yoshinori , Takei Kohji 
Published: September 2003

AbstractExposure of the skin to sunlight results in an increase of the content of epidermal trans‐urocanic acid, a key metabolite of L‐histidine, and also in occurrence of the isomerization of trans‐urocanic acid to the cis isomer. S‐[2‐Carboxy‐1‐(1H‐imidazol‐4‐yl)ethyl]glutathione (GS(CIE)), an adduct of urocanic acid and glutathione, is a presumed origin of a urinary compound S‐[2‐carboxy‐1‐(1H‐imidazol‐4‐yl)ethyl]‐L‐cysteine (Cys(CIE)). The formation of GS(CIE) is stimulated by exposing the skin to sunlight irradiation. In this study we investigated an enzymatic formation of GS(CIE) from glutathione and cis‐urocanic acid by incubation with rat liver extract that contained glutathione S‐transferase (GST) at high activity. The formation of GS(CIE) was suppressed significantly when a liver extract depleted of GST activity was used. Enzymatic degradation of GS(CIE) with γ ‐glutamyl transpeptidase resulted in the formation of N‐{S‐[2‐carboxy‐1‐(1H‐imidazol‐4‐yl)ethyl]‐L‐cysteinyl}glycine, a metabolic intermediate between the glutathione adduct and Cys(CIE). A hydrolyzed product of GS(CIE) by HCl was identical with the urinary Cys(CIE). Compounds were analyzed by high‐voltage paper electrophoresis, capillary electrophoresis, and fast atom bombardment mass spectrometry. From these results, we suggest that GS(CIE) formed from cis‐urocanic acid and glutathione is an origin of the urinary compound Cys(CIE) and that the formation reaction is catalyzed mostly by the action of GST.
Mixed C18 and C1 modification on an optical fiber for chromatographic sensing
Authors: Zhou Leiji , Wang Kemin , Zuo Xinbing , Choi Martin M. F. , Chen Yunqing , Huang Shasheng 
Published: September 2003

AbstractAn optical fiber‐chromatographic sensor, aiming at simultaneous and selective response to multiple components following a chromatographic separation, is described. We report an improved approach for immobilization of octadecyl (C18) and methyl (C1) moieties as stationary phase on an optical fiber suitable as a sensing phase for organic solutes. By this approach, the stability and lifetime of the sensing layer as well as the detectability and retention behavior of the chromatographic sensor could be improved. Infrared spectroscopy was employed to confirm the presence of C18 and C1 moieties on the modified surface of the optical fiber. The chromatographic sensor was applied, with good sensitivity and chemical selectivity, to the simultaneous separation and detection of bromobenzene and toluene, using water as the mobile phase.
Analysis of chicken and turkey ovalbumins by microchip electrophoresis combined with exoglycosidase digestion
Authors: Mao Xiuli , Wang Keyi , Du Yuguang , Lin Bingcheng 
Published: September 2003

AbstractThe polypeptide and carbohydrate patterns of two glycoproteins, chicken ovalbumin (CO) and turkey ovalbumin (TO), were analyzed by microchip electrophoresis (ME), following digestion with proteases and exoglycosidases. Glycopeptides derived from ovalbumin were obtained by digestion with Pronase, followed by dialysis, and then separated by ME. Using CO as model, the method was developed to deduce the structure of glycans from glycoproteins by comparing the electropherograms of glycopeptides with and without digestion of exolycosidases. Applying the same approach, the structure of oligosaccharides linked to TO was determined. TO was found to contain high‐mannose type oligosaccharides and oligosaccharides with terminal N‐acetylglucosamine residues. The complete primary analysis of CO and TO by ME described in this paper provides a basis for an analysis of glycoproteins with an integrated microfluidic chip.
New species of Astragalus L. (Fabaceae) from Iran, mainly of sects. Incani and Malacothrix
Authors: Podlech D. , Maassoumi A. A. 
Published: September 2003

AbstractDuring the work on Astragalus for “Flora Iranica” 39 new species of Astragalus, mainly from sects. Incani and Malacothrix could be discovered among the rich material collected in recent times. They are described here: Sect. Erioceras : A. pakravaniae ; Sect. Hololeuce : A. chaldoranicus ; Sect. Incani : A. abharensis, A. bukanensis, A. estahbanensis, A. fagh‐soleimanensis, A. homandicus, A. insularis, A. khadem‐kandicus, A. kiamaky‐daghensis, A. lacus‐valashti, A. maarofii, A. pseudorobustus, A. sabetii, A. safavii, A. sarabensis, A. semiromensis, A. siahcheshmehensis, A. subglaberrimus, A. zanjanensis ; Sect. Malacothrix : A. ashtianensis, A. aznaicus, A. bejourensis, A. belgheisicoides, A. chichesticus, A. clivicola, A. hajiabadensis, A. lasiocalycinus, A. markasicus, A. mehrizianus, A. pileh‐khasehensis, A. reconditus, A. runemarkii, A. shabilensis, A. shahinii, A. sisakhtianus, A. sivendicus, A. spachianiformis ; Sect. Stereothrix : A. altimontanus.
Die Häufigkeit von Oenothera‐Arten im westlichen Mitteleuropa
Authors: Wittig R. , Tokhtar V. K. 
Published: September 2003

AbstractAuf ausgewählten Industrie‐ und Verkehrstandorten in drei Ballungsgebieten des westlichen Mitteleuropas (Rhein‐Ruhr‐Gebiet: Nordrhein‐Westfalen/ Deutschland; Frankfurt: Hessen/Deutschland; Oberrheingebiet: Baden‐Württemberg/Deutschland und Elsass/ Frankreich) wurde in den Jahren 1999 bis 2002 an ausgewählten, Oenothera ‐reichen Standorten (Industriegelände, Bahngelände, Hafenanlagen) eine quantitative Bestandsaufnahme der Oenothera ‐Arten vorgenommen. Hierbei belegten O. biennis und O. fallax nahezu gleichrangig den ersten Platz in der Häufigkeitsliste. Mit teilweise recht deut‐lichem Abstand folgen O. pycnocarpa und O. glazioviana auf den Plätzen 3 und 4. Bemerkenswer‐terweise ergab eine gleichzeitig in Frankfurt durchgeführte Rasterkartierung der Oenothera ‐Arten die gleiche Reihenfolge dieser vier Spezies im Hinblick auf die Zahl der von ihnen besiedelten Rasterfelder. Wie der Vergleich mit älteren Arbeiten zeigt, in denen O. biennis stets als die eindeutig häufigste Art genannt wird, hat sich O. fallax offensichtlich erst in jüngster Zeit stark ausgebreitet.
Carotenoids in certain lichens from the Colombian Andes
Authors: Czeczuga B. , Czeczuga‐Semeniuk E. , Sipman H. 
Published: September 2003

AbstractReverse‐phase high‐performance liquid chromato‐graphy, column and thin‐layer chromatography re‐vealed the presence of following carotenoids in the thalli of 10 species (14 specimens) of lichens from the Colombian Andes: β‐carotene, β‐cryptoxanthin, zeaxanthin, lutein, calthaxanthin, caloxanthin, 3′‐hydroxyechinenone, canthaxanthin, fritschiellaxanthin, astaxanthin, antheraxanthin, violaxanthin, neoxanthin, mutatoxanthin and capsochrome. The total content of carotenoids ranged from 18.41 μg g−1 (Stereocaulon ramulosum ) to 45.78 μg g−1 (Thamnolia vermicularis, no. 3) dry mass.
Upregulation of the truncated basic hair keratin 1(hHb1‐ΔN) in carcinoma cells by Epstein‐Barr virus (EBV)
Authors: Nishikawa Jun , Kiss Csaba , Imai Shousuke , Takada Kenzo , Okita Kiwamu , Klein George , Szekely Laszlo 
Published: September 2003

AbstractTo investigate the role of Epstein‐Barr virus (EBV) in epithelial tumors, we compared the expression pattern of cellular genes in the EBV‐infected gastric carcinoma cell line, NU‐GC‐3, and its uninfected control. Subtractive suppression hybridization (SSH) was combined with high‐density DNA array screening to identify differentially expressed genes. We have discovered that EBV infection upregulated a truncated variant of human basic hair keratin 1 (hHb1‐ΔN), a gene that had previously been identified in metastatic breast carcinoma. We verified the differential expression of hHb1‐ΔN in 3 independent EBV‐positive and ‐negative NU‐GC‐3 clones by Northern blotting. We further verified the EBV‐dependent upregulation of hHb1‐ΔN in 3 other carcinoma cell lines (AGS, TWO3 and DLD1) by RT‐PCR. Inhibition of CpG methylation by 5‐Aza‐CdR induced hHb1‐ΔN mRNA expression in the EBV‐negative clones but did not alter the expression in the EBV‐positive clones. The expression of hHb1‐ΔN protein was detectable by immunofluorescence and Western blotting in EBV‐positive but not in EBV‐negative NU‐GC‐3 clones after proteasome inhibitor (MG132) treatment. hHb1‐ΔN protein formed fibrous structures in the cytoplasm and accumulated in distinct nuclear bodies in the euchromatic areas of the cell nucleus. We suggest that the unstable hHb1‐ΔN protein may inhibit some of the functions of the keratin cytoskeleton and/or interfere with transcription regulation. It also may establish a link between EBV and the low differentiated or anaplastic status of the carcinomas that carry the virus. © 2003 Wiley‐Liss, Inc.
Human T‐cell leukemia virus type 1 Tax activates cyclin‐dependent kinase inhibitor p21/Waf1/Cip1 expression through a p53‐independent mechanism: Inhibition of cdk2
Authors: Chowdhury Iqbal H. , Farhadi Arash , Wang Xiao‐Fan , Robb Merlin L. , Birx Deborah L. , Kim Jerome H. 
Published: September 2003

AbstractWe investigated the possible involvement of HTLV‐1 Tax in the transcriptional activation of p21/Waf1/Cip1 (hereafter p21), a potent inhibitor of cyclin‐dependent kinases and cell growth. Tax transfection resulted in enhanced expression of p21 protein in T and fibroblastoid cells. Similarly, Tax‐expressing cells have higher amounts of endogenous p21 protein and RNA. However, neither Tax‐negative, HTLV‐1 transformed cells or HTLV‐1‐negative T cell lines had detectable levels of p21 protein and RNA. Cotransfection of Tax strongly activated the p21 promoter. CREB/ATF defective Tax mutant (M47) activated the p21 promoter significantly less efficiently. Tax activated wild type (wt) p21 promoter in p53‐negative Jurkat and p53‐positive A301cells, irrespective of endogenous p53 status, and activated a mutant p21 promoter containing a p53 responsive element (p53RE) deletion as strongly as wt promoter. Of importance, cdk2 activity was almost completely abolished in Tax‐induced p21‐expressing MT‐2 cells, suggesting that Tax‐induced p21 predominantly affects the activity of cdk2, a late G1 and S phase kinase. Taken together, these findings suggest that HTLV‐1 Tax activates p21/Waf1/Cip1, a cell growth inhibitor, in a p53‐independent mechanism through CREB/ATF‐related transcription factors, and inhibits cdk2. Tax induction of p21 may balance the T‐cell proliferation function of Tax and may contribute to the long clinical latency of HTLV‐1 infection and the delayed development of adult T‐cell leukemia. © 2003 Wiley‐Liss, Inc.
Inhibition of JNK signaling diminishes early but not late cellular stress‐induced apoptosis
Authors: Krilleke Dominik , Ucur Esat , Pulte Dianne , Schulze‐Osthoff Klaus , Debatin Klaus‐Michael , Herr Ingrid 
Published: September 2003

AbstractThe human leukemic T‐cell line Jurkat was used to define the role of the cellular stress pathway with its key player kinase JNK in cancer therapy‐induced apoptosis. JNK activity was inhibited by stable transfection with a dominant negative mutant of the upstream kinase JNKK/MKK4 or with the novel, potent and selective JNK1, ‐2 and ‐3 inhibitor SP600125. Inhibition of JNK activity delayed the onset of apoptosis induced by cisplatin, doxorubicin, γ‐irradiation and CD95‐L but did not prevent apoptosis per se. Early events during apoptosis such as induction of CD95‐L, activation of caspase‐8 and exposure of phosphatidylserine on the cell surface were strongly inhibited. Also, at early time points of apoptosis, loss of the mitochondrial membrane potential and release of cytochrome c were markedly impaired. However, late signaling events during apoptosis such as cleavage of PARP and DNA fragmentation apoptosis were only marginally affected. These findings are in accordance with the activity of initiator and effector caspases. Whereas activity of the initiator caspase‐8 was strongly inhibited early and late after induction, an inhibition of caspase‐3 activity was only observed early after induction of apoptosis. We therefore suggest that cellular stress signaling contributes to the initiation of apoptosis, whereas it might be dispensable for the progression of apoptosis. Dysfunction of this pathway under pathological conditions might contribute to therapy resistance of cancer cells. © 2003 Wiley‐Liss, Inc.