bluuebunny/crossref_metadata_2025_split huggingface dataset:
Study of enzymatic reaction by electrophoretically mediated microanalysis in a partially filled capillary with indirect or direct detection
Authors: Telnarová Magdaléna , Vytisková Soňa , Chaloupková Radka , Glatz Zdeněk 
Published: January 2004

AbstractElectrophoretically mediated microanalysis (EMMA), in combination with a partial filling technique and indirect or direct detection, is described for the study of enzymes reacting with the high mobiliby inorganic or organic anions as substrates or products. Part of the capillary is filled with a buffer optimized for the enzymatic reaction, the rest of the capillary with the background electrolyte being optimal for the separation of substrates and products. With haloalkane dehalogenase, chosen as a model enzyme, the enzymatic reaction was performed in a 20 mM glycine buffer (pH 8.6). Because of the wide substrate specifity of this enzyme, utilizing chlorinated as well as brominated substrates and producing either nonabsorbing chloride or absorbing bromide ions, two different background electrolytes and detection approaches were adopted. A 10 mM chromate‐0.1 mM cetyltrimethylammonium bromide background electrolyte (pH 9.2) was used in combination with indirect detection and 20 mM β‐alanine‐hydrochloric acid (pH 3.5) in combination with direct detection. The Michaelis constant (Km) of haloalkane dehalogenase for 1‐bromobutane was determined. The Km values 0.59 mM estimated by means of indirect detection method and 0.17 mM by means of direct detection method were comparable with the value 0.13 mM estimated previously by gas chromatography.
Optimisation of selectivity in the separation of aromatic amino acid enantiomers using sulfated ß‐cyclodextrin and dextran sulfate as pseudostationary phases
Authors: Zakaria Philip , Macka Miroslav , Haddad Paul R. 
Published: January 2004

AbstractControl of selectivity in the enantiomeric separation of three aromatic amino acids (phenylalanine, tyrosine and tryptophan) was demonstrated utilising two separate electrolyte additives. Sulfated‐β‐cyclodextrin (s‐β‐CD) was chosen as the chiral selector while the addition of dextran sulfate provided a means with which to predictably fine‐tune separation selectivity. The two additives were found to interact independently with the amino acids, with the s‐CD providing chiral interactions while the dextran sulfate provided ion‐exchange (IE) interactions. The system was also very robust with reproducibility of migration times being < 2.0% RSD between runs and < 2.6% on using a new capillary. A physical model derived from first principles was also successfully used to describe the two additive system. The model accurately described the observed separations over the range of 0–20 mM s‐β‐CD and 0–1% dextran sulfate with a correlation coefficient of 0.998 between predicted and observed mobilities. The physical model also provided useful information about the system including association constants between the analytes and the pseudostationary phases, together with the mobilities of the associated complexes (analyte‐cyclodextrin and analyte‐dextran sulfate). Selectivity optimisation was achieved using the normalised resolution product and minimum resolution criteria. The physical model also allowed a desired separation selectivity to be obtained, such that experimental conditions could be predicted to lead to a particular migration order.
Novel enantioselective strong cation exchangers based on sulfodipeptide selectors: Evaluation for enantiomer separation of chiral bases by nonaqueous capillary electrochromatography
Authors: Hebenstreit Dieter , Bicker Wolfgang , Lämmerhofer Michael , Lindner Wolfgang 
Published: January 2004

AbstractStrong cation exchange (SCX)‐type chiral stationary phases (CSPs) based on β‐amino sulfonic acid‐terminated dipeptide derivatives as chiral selectors, immobilized on thiol‐modified silica particles (3.5 μm), were synthesized and applied to enantiomer separations of chiral bases by nonaqueous capillary electrochromatography (CEC). The effect of structural variations of the sulfodipeptide selectors on the separation factors α was investigated. These studies included variation of the acid‐terminal amino sulfonic acid residue, variation of the configurations, i.e., comparison of the diastereomeric (S,S)‐ and (R,S)‐configurations of the sulfodipeptides, and finally comparison of sulfodipeptide selectors with corresponding β‐amino sulfonic acid analogs. In general, the capillary columns (100 μm ID) packed with the new SCX‐type CSPs showed enantioselectivity for an elaborated set of chiral basic drugs in CEC acting by an enantioselective cation‐exchange retention mechanism. N‐[N‐(4‐Allyloxy‐3,5‐dichlorobenzoyl)‐leucyl]‐2‐amino‐3,3‐dimethylbutane sulfonic acid, in particular with (R,S)‐configuration, turned out to be a more effective SCX‐type selector than a more rigid analog based on N‐[N‐(4‐Allyloxy‐3,5‐dichlorobenzoyl)‐leucyl]‐2‐pyrrolidinemethane sulfonic acid. Both of the former diastereomers were capable to baseline‐resolve the enantiomers of ca. 40% of the tested basic chiral solutes including sympathomimetics and β‐blockers, while for the latter SCX‐type CSPs only 10–20% of the selected solutes afforded resolutions > 1.5.
Ongoing development of two‐dimensional polyacrylamide gel electrophoresis data standards
Authors: Ravichandran Veerasamy , Lubell Joshua , Vásquez Gregory B. , Lemkin Peter , Sriram Ram D. , Gilliland Gary L. 
Published: January 2004

AbstractWe present an approach toward standardizing two‐dimensional polyacrylamide gel electrophoresis (2‐D PAGE) data in support of developing a globally relevant proteomics consensus in order to provide more efficient database querying and data comparisons through the establishment of the necessary definitions and interdisciplinary reference fields for both the 2‐D PAGE community, particularly in the proteomics area, and the clinical and experimental biological research communities, in general. This article covers the need for unifying the 2‐D PAGE data through a common data repository, and its usefulness in data standards and data interoperability.
Cyclic electrophoretic and chromatographic separation methods
Authors: Eijkel Jan C. T. , van den Berg Albert , Manz Andreas 
Published: January 2004

AbstractA review is given of the application of cyclic analytical methods in capillary electroseparation (CE) and liquid chromatography (LC) systems. Cyclic methods have been used since the early sixties in chromatographic systems to overcome pressure limitations to resolution. From the early nineties on they have also been applied in capillary electroseparation systems to overcome voltage limitations. Some basic theory is given, outlining the temporal development of resolution in cyclic CE and LC systems and calculating the maximal resolution that can be obtained as a function of the operational parameters of pressure and electrical field. Simple equations are given for the temporal change in the peak capacity and the loss of peaks from the systems as it occurs in some cyclic systems. Finally, a circular open tubular chromatographic system is proposed using integrated pumping and continuous detection. The performance of such a system is discussed using magnetohydrodynamic and alternating current electroosmotic pumping as examples of integrated pumps and Shah Convolution Fourier transform detection as an example of a continuous detection method.
Determination of cationic mobilities and pKa values of 22 amino acids by capillary zone electrophoresis
Authors: Včeláková Kateřina , Zusková Iva , Kenndler Ernst , Gaš Bohuslav 
Published: January 2004

AbstractThe effective mobilities of the cationic forms of common amino acids – mostly proteinogenic – were determined by capillary zone electrophoresis in acidic background electrolytes at pH between 2.0 and 3.2. The underivatized amino acids were detected by the double contactless conductivity detector. Experimentally measured effective mobilities were fitted with the suitable regression functions in dependence on pH of the background electrolyte. The parameters of the given regression function corresponded to the values of the actual mobilities and the mixed dissociation constants (combining activities and concentrations) of the compound related to the actual ionic strength. McInnes approximation and Onsager theory were used to obtain thermodynamic dissociation constants (pKa) and limiting (absolute) ionic mobilities.
Preparative‐scale, recirculating, pH‐biased binary isoelectric trapping separations
Authors: Shave Evan , Vigh Gyula 
Published: January 2004

AbstractIn order to improve the production rates and lower the specific electrophoretic energy consumption values in preparative‐scale, recirculating, binary isoelectric trapping separations, we propose to add an auxiliary isoelectric agent to the solution in the anodic separation compartment and another to the solution in the cathodic separation compartment to implement pH‐biased isoelectric trapping. The auxiliary isoelectric agents are selected such that they are trapped in the respective anodic and cathodic separation compartments and also, have isoelectric point (pI) values that are different from the pI values of the analytes of interest. By proper selection of the auxiliary isoelectric agents and their concentrations, the analytes of interest can be kept in nonisoelectric, charged state during the entire course of the preparative‐scale, recirculating, binary isoelectric trapping separation. This results in higher electrophoretic mobilities and solubilities for the analytes than in their isoelectric or near‐isoelectric states, and leads to faster binary isoelectric trapping separations.
Preparative free‐flow electrofocusing in a vortex‐stabilized annulus
Authors: Ivory Cornelius F. 
Published: January 2004

AbstractThis paper describes the development of an annular chamber designed for preparative free‐flow electrophoresis which can operate at voltages up to 20 kV, electric fields up to 65 kV/m, and power densities as high as 10 MW/m3. This apparatus uses counter‐rotating fluid vortices to stabilize the aqueous medium in the annulus against natural convection while improving heat and mass transfer over vortex‐free Couette flow. The vortices are generated by rotating the inner surface of the annulus and, if the rotor and stator have complementary shapes, dispersion induced by electrokinetic and electrohydrodynamic flows can be mitigated even at the highest operating voltages. Following a brief overview of contemporary annular free‐flow instrumentation, the theoretical principles for momentum and heat transport in the vortices are discussed in some detail and then the results of several electrofocusing experiments are provided to illustrate the resolving power of this instrument.
Zeta potential of microfluidic substrates: 2. Data for polymers
Authors: Kirby Brian J. , Hasselbrink Ernest F. 
Published: January 2004

AbstractZeta potential data are reviewed for a variety of polymeric microfluidic substrate materials. Many of these materials currently used for microchip fabrication have only recently been employed for generation of electroosmotic flow. Despite their recent history, polymeric microfluidic substrates are currently used extensively for microchip separations and other techniques, and understanding of the surface ζ potential is crucial for experimental design. This paper proposes the use of pC (the negative logarithm of the counterion concentration) as a useful normalization for the ζ potential on polymer substrates in contact with indifferent univalent counterions. Normalizing ζ by pC facilitates comparison of results from many investigators. The sparseness of available data for polymeric substrates prevents complete and rigorous justification for this normalization; however, it is consistent with double layer and adsorption theory. For buffers with indifferent univalent cations, normalization with the logarithm of the counterion concentration in general collapses data onto a single ζ/pC vs. pH curve, and (with the exception of PMMA) the repeatability of the data is quite encouraging. Normalization techniques should allow improved ability to predict ζ potential performance on microfluidic substrates and compare results observed with different parameters.
Mutation induction in haploid yeast after split‐dose radiation exposure. II. Combination of UV‐irradiation and X‐rays
Authors: Keller B. , Zölzer F. , Kiefer J. 
Published: January 2004

AbstractSplit‐dose protocols can be used to investigate the kinetics of recovery from radiation damage and to elucidate the mechanisms of cell inactivation and mutation induction. In this study, a haploid strain of the yeast, Saccharomyces cerevisiae, wild‐type with regard to radiation sensitivity, was irradiated with 254‐nm ultraviolet (UV) light and then exposed to X‐rays after incubation for 0–6 hr. The cells were incubated either on nutrient medium or salt agar between the treatments. Loss of reproductive ability and mutation to canavanine resistance were measured. When the X‐ray exposure immediately followed UV‐irradiation, the X‐ray survival curves had the same slope irrespective of the pretreatment, while the X‐ray mutation induction curves were changed from linear to linear quadratic with increasing UV fluence. Incubations up to about 3 hr on nutrient medium between the treatments led to synergism with respect to cell inactivation and antagonism with respect to mutation, but after 4–6 hr the two treatments acted independently. Incubation on salt agar did not cause any change in the survival curves, but there was a strong suppression of X‐ray‐induced mutation with increasing UV fluence. On the basis of these results, we suggest that mutation after combined UV and X‐ray exposure is affected not only by the induction and suppression of DNA repair processes, but also by radiation‐induced modifications of cell‐cycle progression and changes in the expression of the mutant phenotype. Environ. Mol. Mutagen. 43:28–35, 2004. © 2004 Wiley‐Liss, Inc.
Population doubling: A simple and more accurate estimation of cell growth suppression in the in vitro assay for chromosomal aberrations that reduces irrelevant positive results
Authors: Greenwood Susan K. , Hill Rosina B. , Sun Joan T. , Armstrong Michael J. , Johnson Timothy E. , Gara Jennifer P. , Galloway Sheila M. 
Published: January 2004

AbstractInternational guidelines for cytotoxicity limits for the in vitro chromosomal aberration assay require reductions in cell growth of greater than 50%. This sets no upper limit on toxicity and there is concern about the number of false or irrelevant results obtained in the aberration assay, i.e., positive results at toxic dose levels only, with no evidence for primary DNA damaging ability and with negative results in the other genotoxicity tests. We have previously proposed that no truly genotoxic compound would be missed if the toxicity of the highest dose did not exceed 50%. Cell growth measured by cell counts as a percentage of controls can underestimate toxicity. For example, if we seed half a million cells per culture, and the controls double to 1 million during the experiment, a culture that truly has no growth will still have a cell count 50% of the control. Measurement of population doublings (PDs) more accurately assesses cell growth. To assess the use of PD in dose selection, we examined previous data from this lab and data from new experiments with “true,” primary DNA damaging clastogens, and with clastogens, including drugs, thought to act indirectly, through cytotoxicity‐associated mechanisms. We compared aberration results where the highest doses scored were based on 50% reductions in final cell counts with results obtained when the highest doses were based on PD. The PD method allows detection of true clastogens, including those that are active in a range with some toxicity, and reduces the number of toxicity‐related “false”‐positive results. Environ. Mol. Mutagen. 43:36–44, 2004. © 2004 Wiley‐Liss, Inc.
Use of a high‐throughput umu‐microplate test system for rapid detection of genotoxicity produced by mutagenic carcinogens and airborne particulate matter
Authors: Oda Yoshimitsu , Funasaka Kunihiro , Kitano Masaaki , Nakama Akihiko , Yoshikura Taro 
Published: January 2004

AbstractIn the present study, we developed a rapid umu‐microplate test system that uses the nitroreductase‐ and O‐acetyltransferase‐overproducing Salmonella typhimurium strain NM3009 and the O‐acetyltransferase‐overproducing S. typhimurium strain NM2009 to detect genotoxic activity in small volume samples. The assay was used to test the genotoxicity of several standard mutagens and environmental samples. Exponentially growing cultures of NM3009, NM2009, and the parental strain TA1535/pSK1002 were incubated in 96‐well microplates with test chemicals both in the presence and in the absence of rat liver S9. The relative β‐galactosidase activities were then determined colorimetrically using either chlorophenol red‐β‐D‐galactopyranoside (CPRG) or O‐nitrophenyl‐β‐D‐galactopyranoside (ONPG) as a measure of umuC gene induction activity. The sensitivities of NM3009 without S9 mix and NM2009 with S9 mix to nitroarenes and aromatic amines were up to 24‐ to 75‐fold higher than those of the parent strain. Induction of umuC gene expression was detected more readily with CPRG than ONPG. The umu‐microplate assay also detected genotoxicity in organic extracts of particulate matter from air samples collected in Osaka City, Japan. The pattern of the responses suggested that the genotoxic activity of the particulate extract was due primarily to nitrated polycyclic aromatic hydrocarbons. Our results indicate that the umu‐microplate assay may be a useful way of carrying out rapid screens for genotoxicity in small‐volume environmental samples. Environ. Mol. Mutagen. 43:10–19, 2004. © 2004 Wiley‐Liss, Inc.
Genetic damage detected in CD‐1 mouse pups exposed perinatally to 3′‐azido‐3′‐deoxythymidine and dideoxyinosine via maternal dosing, nursing, and direct gavage
Authors: Bishop Jack B. , Witt Kristine L. , Tice Raymond R. , Wolfe Gary W. 
Published: January 2004

AbstractHuman immunodeficiency virus (HIV)‐infected pregnant women are administered nucleoside‐analogue antiretrovirals to reduce maternal‐infant viral transmission. The current protocol recommends treating newborns for 6 additional weeks postpartum. The treatment is effective, but the risk of drug‐induced chromosomal damage in neonates remains undefined. We used a mouse model to investigate this concern. In a multigeneration reproductive toxicity study, female CD‐1 mice received 3′‐azido‐3′‐deoxythymidine (AZT) and dideoxyinosine (ddI) (50/250, 75/375, 150/750 mg/kg/day AZT/ddI) by gavage twice daily in equal fractions beginning prior to mating and continuing throughout gestation and lactation. Direct pup dosing (same regimen) began on postnatal day (PND) 4. Peripheral blood erythrocytes of male pups were screened for micronuclei, markers of chromosomal damage, on PNDs 1, 4, 8, and 21. Extraordinary increases in micronucleated cells were noted in pups for each treatment group at each sampling time; treated dams exhibited smaller yet significant increases in micronucleated erythrocytes. The frequencies of micronucleated cells in untreated pups were higher than in the untreated dams, and all pups had markedly elevated levels of circulating reticulocytes compared to dams. These observations suggest that fetal and neonatal mouse hematopoietic precursor cells have heightened sensitivity to genotoxic agents, perhaps due to rapid cell proliferation during the perinatal period of development. The amount of genetic damage observed in treated pups raises concern for the potential of similar damage in humans. Investigations of chromosomal integrity in exposed newborns and children are recommended. Environ. Mol. Mutagen. 43:3–9, 2004. © 2004 Wiley‐Liss, Inc.
Comparative genomic hybridization analysis of N‐methyl‐N′‐nitrosoguanidine‐induced rat gastrointestinal tumors discloses a cytogenetic fingerprint
Authors: Corso Chiara , Parry James M. 
Published: January 2004

AbstractExposure to N‐nitroso compounds is thought to play a key role in the development of gastric cancer in humans. The alkylating agent N‐methyl‐N′‐nitrosoguanidine (MNNG) is carcinogenic in a number of animal models and its preferential target tissue is the gastrointestinal (GI) tract. The genetic synteny among rats and humans makes the rat a useful model for induced tumorigenesis. However, because of the limited availability of genetic information, cytogenetic and molecular studies are rarely performed in the rat. We report an investigation of eight MNNG‐induced rat gastric tumors by comparative genomic hybridization (CGH). The tumors were from forestomach (induced by a single dose of MNNG) and from pylorus (induced by chronic exposure). CGH identified a genetic fingerprint of chromosomal imbalances common to the two types of the tumors. Frequent gains were observed at 9q11–q12, 15q22–25, and Xq11–q12. Forestomach carcinomas were also characterized by gains in 7q11–q12, 20q13, and Yq12. Homology studies between the rat and human genomes indicate the presence of genes within these regions with potential relevance to tumorigenesis in the GI tract. Our findings provide new insights into the location of genes involved in MNNG‐induced gastric cancer initiation and/or progression in the rat. Environ. Mol. Mutagen. 43:20–27, 2004. © 2004 Wiley‐Liss, Inc.
Effect of cyanidin 3‐O‐β‐glucopyranoside on micronucleus induction in cultured human lymphocytes by four different mutagens
Authors: Fimognari Carmela , Berti Fausto , Cantelli‐Forti Giorgio , Hrelia Patrizia 
Published: January 2004

AbstractThe anthocyanin cyanidin 3‐O‐β‐glucopyranoside (Cy‐g) is reported to be one of the most effective antioxidants, but little is currently known regarding its potential chemopreventive properties. In this study, we evaluated the ability of Cy‐g to protect cultured human lymphocytes from micronucleus (MN) induction by four different mutagens: ethyl methanesulfonate (EMS), colchicine (COL), H2O2, and mitomycin C (MMC). To gain insight into the mechanisms of action of Cy‐g, the cultures were treated with the compound before, during, and after treatment with the mutagens; in addition, the cultures were evaluated for the induction of apoptosis. When used by itself, up to 100 μg/ml of Cy‐g was nongenotoxic, while 100 μg/ml Cy‐g reduced the replicative index of the cells by nearly 50%. In addition, Cy‐g was able to reduce the frequency of micronuclei induced by EMS, COL, and H2O2 using all three treatment protocols, but it had no significant effect on MN induction by MMC in any of the protocols. Apoptosis was produced in the cultures treated with Cy‐g alone and was increased under conditions in which Cy‐g produced anti‐genotoxic effects, suggesting that Cy‐g mediated‐apoptosis may remove highly damaged cells. However, increases in apoptosis were found under conditions in which Cy‐g was not significantly anti‐genotoxic, indicating that the increases in apoptosis were not sufficient to account for the anti‐genotoxicity of Cy‐g. Taken together, our findings indicate that Cy‐g possesses anti‐genotoxic activity in vitro, which suggests its potential use as a chemopreventive agent. Environ. Mol. Mutagen. 43:45–52, 2004. © 2004 Wiley‐Liss, Inc.