bluuebunny/crossref_metadata_2025 huggingface dataset:
Screen for enhancers of Polycomb and Polycomblike in Drosophila melanogaster
Authors: Landecker Hannah L. , Sinclair Donald A. R. , Brock Hugh W.
Published: May 2005

There are 11 Polycomb group genes known in Drosophila. These genes are negative regulators of homeotic gene expression, and may act by modifying chromatin structure. It is not clear how many members of the Polycomb group of genes exist. Many were discovered because of their homeotic phenotypes, or because they enhance homeotic mutations. Systematic screens for enhancers of Polycomb have identified previously known members of the Polycomb group. In an attempt to discover cytological locations of new Polycomb group genes, we crossed deletions uncovering about 20% of the genome to Polycomb‐like and Polycomb and scored for enhancement of the extra sex combs phenotype. Haploidy for four regions, 36F7‐37A, 43E18; 44B5‐9, 70C2‐6, and 70C6‐15; 70D enhanced the extra sex comb phenotype associated with strong Polycomb group mutations. These regions have homeotic phenotypes either as homozygous embryos or heterozy‐gous adults, or both. We also show that spalt enhances Polycomb group mutations. These results are discussed with respect to previous estimates of Polycomb group gene number. © 1994 Wiley‐Liss, Inc.
Developmental arrest of fertilized eggs from the B6.YDOM sex‐reversed female mouse
Authors: Merchant‐Larios Horacio , Clarke Hugh J. , Taketo Teruko
Published: May 2005

When the Y chromosome of a Mus musculus domesticus mouse strain is placed onto the C57BL/6J (B6) inbred background, the XY progeny develop ovaries or ovotestes but never normal testes during fetal life. While some of the hermaphroditic males become fertile, none of the XY females produces litters. Here, we examined the fertility and development of oocytes derived from the XY female mouse. With or without preceding injection of gonadotropins, female mice were mated with normal B6 males, and their embryos were recovered at various developmental stages. In vitro fertilization was performed with the eggs recovered from the oviduct after treatment with go‐nadotropins. Development of embryos was examined by both light and electron microscopy. The results indicate that the oocytes released from the B6.YDOM ovary were efficiently fertilized and often initiated the first cell cleavage, but all embryos died during early preimplantation periods. Even when oocytes were fertilized in vitro, minimizing their exposure to the XY oviduct/uterus environment, most embryos died at the 1‐ or 2‐cell stage. A few exceptional embryos reached the 4‐ or 8‐cell stage, but abnormalities were evident in both nuclear and cytoplasmic structures of all embryos. After cleavage, neighbouring blastomeres were only loosely associated, and microvilli were abundant at the intercellular interfaces. We postulate that oocytes of the B.6.YDOM female mouse become defective during XY ovarian differentiation, and, hence, fail to proceed through normal embryonic development. © 1994 Wiley‐Liss, Inc.
Epigenetics and the maintenance of gene activity states in Caenorhabditis elegans
Authors: Hodgkin Jonathan
Published: May 2005

The nematode Caenorhabditis elegans has been the subject of many detailed investigations in developmental biology. Molecular analyses have failed to detect covalent alterations to DNA, such as methylation or rearrangement, during development of C. elegans. Genetic experiments indicate that imprinting of gamete genomes does not occur to any significant extent. The maintenance of gene activity states in this organism may depend predominantly on regulatory gene circuitry. Some possible examples of maintenance circuits are discussed. © 1994 Wiley‐Liss, Inc.
Expression of an X‐linked HMG‐lacZ transgene in mouse embryos: Implication of chromosomal imprinting and lineage‐specific X‐chromosome activity
Authors: Tam Patrick P. L. , Williams Elizabeth A. , Tan Seong‐Seng
Published: May 2005

X‐chromosome activity in female mouse embryos was studied at the cellular level using an X‐linked lacZ transgene which encodes β‐galactosidase (β‐Gal). Translation of maternal RNA in oocytes is seen as β‐Gal activity that persists into early cleavage‐stages. Zygotic transcription of the transgene from the maternal X chromosome (Xm) is first found at about the 8‐cell stage. By contrast, expression of the lacZ transgene on the paternal X chromosome (Xp) is not seen until later at the 16‐32‐cell stage. Preferential inactivation of Xp occurs in the mural trophectoderm, the primitive endoderm, and derivatives of the polar trophectoderm, but a small number of cells in these lineages may still retain an active paternal X chromosome. X inactivation begins at 3.5 days in the inner cell mass but contrary to previous findings the process is not completed in the embryonic ectoderm by 5.5 to 6.0 days. Regional variation in β‐Gal activity is also observed in the embryonic ectoderm during gastrulation which may be related to the specification of cell fates. Random inactivation of Xp and Xm ensues in all somatic tissues but the process is completed at different times in different tissues. The slower progression of X inactivation in tissues such as the notochord, the heart, and the embryonic gut is primarily due to the persistent maintenance of two active X chromosomes in a significant fraction of cells in these tissues. Recent findings on the methylation of endogenous X‐linked genes suggest that the prolonged expression of β‐Gal might also be due to the different rate of spreading of inactivation along the X chromosome to the lacZ transgene locus in different tissues. © 1994 Wiley‐Liss, Inc.
Culture of pachytene spermatocytes for analysis of meiosis
Authors: Handel M. A. , Caldwell K. A. , Wiltshire T.
Published: May 2005

An impediment to the investigation of mammalian spermatogenic meiosis has been the lack of an appropriate system for experimental manipulation of meiotic prophase cells. We report here the use of a simple system for the short‐term culture of pachytene spermatocytes. We have assayed parameters of cell function pertinent to meiotic prophase, namely chromosome pairing and synapsis. During the culture period of 24–48 hr, cells maintained typical pachytene morphology, chromatin condensation patterns, and chromosome pairing, as assessed by light and electron microscopy. Uridine incorporation, monitored by autoradiography, reflected the chromosomal distribution found in vivo in that the autosomal chromosomes were transcriptionally active, while the sex chromosomes were not. Thus features of chromosome pairing and sex chromatin inactivation are maintained in these cultures. We have conducted experiments to demonstrate that cultured pachytene spermatocytes can be useful for the analysis of agents, some of which may be suspected mutagens, that might affect chromosome structure and function during meiosis. Treatment of cells with actinomycin D revealed a differential effect on chromatin condensation in the autosomes versus the sex chromosomes. Carnptothecin, a topoisomerase inhibitor, induced desynapsis of paired chromosomes. Okadaic acid, a phosphatase inhibitor, induced premature metaphase‐I condensation of pachytene chromosomes. This last experiment suggests that these cultured cells may be useful for analysis of meiotic cell cycle controls. Taken together, these results demonstrate a culture system that can be useful for analysis of meiotic events as well as in screening for potential mutagenic agents that might affect meiotic chromosome structure and function. © 1995 Wiley‐Liss, Inc.
Regulation of β‐tubulin function and expression in Drosophila spermatogenesis
Authors: Hoyle Henry D. , Hutchens Jeffrey A. , Turner F. Rudolf , Raff Elizabeth C.
Published: May 2005

In this study we examined two aspects of β‐tubulin function in Drosophila spermatogenesis: 1) β‐tubulin structural requirements for assembly of different categories of microtubules and 2) regulatory requirements for production of the correct tubulin protein level. In normal Drosophila spermatogenesis, the testis‐specific β2‐tubulin isoform supports multiple microtubule functions. Our previous work showed that another Drosophila isoform, β3, cannot support spermatogenesis, whereas a carboxyl‐truncated form of β2, β2ΔC, can at least to some extent provide all of β2′s normal functions, save one: β2ΔC cannot support organization of axonemal microtubules into the supramolecular architecture of the axoneme. Here, to test whether β2 carboxyl sequences can rescue the functional failure of the β3 isoform in spermatogenesis, we constructed a gene encoding a chimeric protein, β3β2C, in which β3 sequences in the carboxyl region are replaced with those of β2. Unlike either β3 or β2ΔC, β3β2C can provide partial function for both assembly of axonemal microtubules and their organization into the supramolecular architecture of the axoneme. In particular, the β2 carboxyl sequences mediate morphogenesis of the axoneme doublet tubule complex, including accessory microtubule assembly and attachment of spokes and linkers. However, our data also reveal aspects of β2‐specific function that require structural features other than the primary sequence of the isotype‐defining variable regions, the C terminus and the internal variable region. Tests of fecundity in males that co‐express Δ2 and the chimeric Δ3Δ2C protein showed that in Drosophila there are differential requirements for sperm motility in the male and in the female reproductive tract. Since some aspects of microtubule function in spermatogenesis are sensitive to the tubulin pool size, we examined the mechanisms for control of tubulin protein levels in the male germ cells. We found that both Δ2‐tubulin mRNA accumulation and protein synthesis are dependent on gene dose, and that the level of expression is regulated by 3′ noncoding sequences in the Δ2 gene. Our data show that the regulatory mechanisms that control tubulin pool levels in the Drosophila male germ line differ from those observed in cultured animal somatic cells. Finally, expression of transgenic constructs is consistent with early cessation of × chromosome expression in Drosophila spermatogenesis. © 1995 Wiley‐Liss, Inc.
Differential expression of fork head genes during early Xenopus and zebrafish development
Authors: Dirksen Marie‐Luise , Jamrich Milan
Published: May 2005

Intense efforts have been devoted to the identification of genes that are causatively involved in pattern‐forming events of invertebrates and vertebrates. Several gene families involved in this process have been identified. Here we focus on the Xenopus fork head domain gene family. One of its members, XFKHl/Pintallavis/XFD1, has been shown previously to be involved in axial formation, and the expression patterns of the other family members discussed below suggest that they too play a major role in the initial steps of patterning and axial organization. In this report, we describe four Xenopus fork head genes XFKH3, 4, 5, and 6) and analyze the distribution of their transcripts during early development. XFKH3 is expressed in developing somites but not notochord, XFKH4 in forebrain, anterior retina, and neural crest cells, and XFKH5 in a subset of epidermal cells and the neural floor plate. Finally, transcripts of XFKH6 are seen in neural crest‐derived cranial ganglia. In addition, we show that at least some of the zebrafish fork head genes might serve a comparable function. Zebrafish zf‐FKHl has a similar expression pattern as Xenopus XFKHl/Pintallavis/XFDl. It is transcribed in the notochord and neural floor plate. The polster or “pillow” also shows very high levels of zf‐FKHl mRNA. © 1995 Wiley‐Liss, Inc.
Imprinting of IGF2, insulin‐dependent diabetes, immune function, and apoptosis: A hypothesis
Authors: Polychronakos Constantin , Giannoukakis Nick , Deal Cheri L.
Published: May 2005

Parental genomic imprinting is the phenomenon in which the behavior of a gene is modified, depending on the sex of the transmitting parent [Peterson and Sapienza (1993): Annu Rev Genet 27:7–31]. Recent observations have revealed that the inheritance patterns, age‐of‐onset, severity, and etiology of certain human diseases can be explained by aberrations in the establishment or the maintenance of the imprint. Examples include the Prader‐Willi, Angelman, and Beckwith‐Wiedemann syndromes [Nicholls (1994): Am J Hum Genet 54:733–740], malignancy [Sapienza (1990): Biochim Biophys Acta 1072:51–61; Feinberg (1993): Nat Genet 4:110–113], and insulin‐ependent diabetes mellitus (IDDM) [Julier et al. (1994) Nature 354:155–159; Bennett et al. (1995) Nat Genet 9:284–292]. We review the evidence that implicates an imprinted gene in the INS‐IGF2 region of chromosome llp15 in the etiology of IDDM (referred to as the IDDM2 locus) and show that in human fetal pancreas, INS is not imprinted, thus providing an argument against INS as the candidate gene. We also examine imprinting effects on the expression of IGF2 in components of the human immune system believed to be important in IDDM and show imprinted expression in fetal thymus as early as 15 weeks gestation. We demonstrate further that in the circulating mononuclear cells of two individuals, lectin‐stimulated IGF2 transcription was biallelic, indicating relaxation of imprinting, whereas in one individual, transcription was monoallelic. Finally, we review the current available data supporting a role for insulin‐like growth factor‐ll (IGF‐II) in the immune system and, more specifically, discuss the evidence supporting a role for the IGFs in the prevention of apoptosis. These data have led us to formulate a novel hypothesis that could mechanistically explain the involvement of the IDDM2 locus in the pathogenesis of IDDM. © 1995 Wiley‐Liss, Inc.
Developmental alteration of the chromatin state at promoter/replication origin region of the aldolase b locus precedes transcriptional activation in the liver
Authors: Ito Kikukatsu , Tsutsumi Reiko , Ishikawa Kiichi , Tsutsumi Ken‐Ichi
Published: May 2005

Liver‐specific expression of the rat aldolase B (AldB) gene is conferred by proximal promoter region (‐200 bp to + 1 bp), which is centered on an origin region of DNA replication. Transcriptional activation of the gene in the liver occurs during the late one‐third of fetal stage. To know the mechanism involved in such activation, we studied developmental changes in chromatin structure and in the extent of CpG methylation in the promoter/origin region of the gene. At an early fetal stage, when the AldB gene in the liver is not yet activated, the gene chromatin had two DNase l‐hypersensitive sites in the promoter region. One corresponded to that typical of AldB‐expressing cells in the adult. The other, located ∼200 bp upstream of the above site, disappeared as the activation of transcription started. A CpG dinucleotide in the promoter/origin region was heavily methylated at an early stage of gestation, but progressively demethylated as the liver develops. This CpG site is located at the center of an important binding site for a transcription factor. These changes occurred early in the fetal stage, prior to the gene activation, and were thus thought to be associated with differentiation of the liver cell or with cessation of cell proliferation.
Cloning and developmental expression of the ecdysone receptor gene from the spruce budworm, choristoneura fumiferana
Authors: Kothapalli Ravi , Palli Subba R. , Ladd Tim R. , Sohi Sardar S. , Cress Dean , Dhadialla Tarlochan S. , Tzertzinis George , Retnakaran Arthur
Published: May 2005

Degenerate oligonucleotides were designed on the basis of conserved amino acid sequences in the DNA and ligand‐binding regions of the members of the steroid hormone receptor superfamily. Using these oligonucleotides in RNA‐PCR, a cDNA fragment was isolated from the spruce budworm, Choristoneura fumiferana. Comparison of the deduced amino acid sequence of this cDNA fragment with the members of the steroid hormone receptor superfamily suggested that this PCR fragment is a region of the ecdysone receptor from C. fumiferana. Using this cDNA fragment as a probe, 10 clones were isolated from a cDNA library that was constructed using the RNA from 4‐ and 5‐day old embryos of C. fumiferana. Two cDNA clones (1.3 and 3 kb) that overlap and show amino acid identity with Drosophila melanogaster ecdysone receptor B‐1 isoform (DmEcR) were characterized and sequenced. The longest open reading frame had 539 codons and covered the complete EcR coding region. The deduced amino acid sequence of this open reading frame had all five of the regions typical for a steroid hormone nuclear receptor. The C domain or DNA binding region showed the highest identity with EcR proteins from D. melanogaster, Chironomus tentans, Aedes aegypti, Manduca sexta and Bombyx mori. The A/B region, D domain or hinge region, E domain, or ligand binding region also showed significant amino acid similarity with the EcR proteins from the five insects mentioned above. The C. fumiferana ecdysteroid receptor (CfEcR) cDNA probe detected a 6.0‐kb mRNA that was present throughout the development of C. fumiferana. The CfEcR mRNA increases in abundance at the time of the ecdysteroid peak during the molting phase in the embryonic, larval and pupal stages but remains low during the intermolt period. In the 6th instar larvae, the 6‐kb CfEcR mRNA was detected in the epidermis, fat body, and midgut and maximum expression was observed during the prepupal peak of ecdysteroids in the hemolymph. CfEcR mRNA was induced in ecdysone treated CF‐203 cells as well as in the epidermis and midgut of larvae that were fed the nonsteroidal ecdysteroid agonist, RH‐5992. The induction occurred within an hour and reached maximum levels around 3 hr, after which it decreased to the basal level by 6 hr. In vitro transcription and translation of the CfEcR cDNA yielded a 67‐Kda protein that bound to the ecdysone response element (EcRE) as a heterodimer, along with the ultraspiracle protein.
Complete Structural Elucidation of a Novel Lipooligosaccharide from the Outer Membrane of the Marine Bacterium Shewanella pacifica
Authors: Silipo Alba , Leone Serena , Molinaro Antonio , Sturiale Luisa , Garozzo Domenico , Nazarenko Evgeny L. , Gorshkova Raisa P. , Ivanova Elena P. , Lanzetta Rosa , Parrilli Michelangelo
Published: May 2005

Shewanella pacifica is a Gram‐negative microrganism that is able to grow in sea water. A novel lipooligosaccharide (LOS) has been isolated from the outer membrane of this bacterium and its primary structure fully characterised. For the first time, the presence of a 2,3‐dihydroxypropanoic acid residue (glyceric acid) has been identified in the core region. The complete structure of the LOS was determined by compositional and methylation analyses, by MALDI mass spectrometry, and by 1H, 13C and 31P NMR spectroscopy on the oligosaccharides formed by selective degradation of the LOS. Strong alkaline treatment, aimed at recovering and identifying the complete carbohydrate backbone, was carried out by hydrazinolysis followed by de‐N‐acylation with hot KOH, whereas mild hydrazinolysis (de‐O‐acylation) allowed us to gain information about the nature of the phosphate and other non‐carbohydrate substituents on the core oligosaccharide. Mild acid hydrolysis was employed to obtain a lipid A moiety with which further degradation and mass spectrometry experiments were carried out in order to determine its primary structure. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Adsorptive stripping tensammetry of commercially available oxyethlated alcohols. Part 1. Surfactants having C10–C13hydrophobes
Authors: Szymanski Andrzej , Lukaszewski Zenon
Published: May 2005

The behavior of oxyethylated oxoalcohols (e.g., Oxetals D104, T105, and C114, and oxyethylatedn‐dodecanol BRIJ‐35) was investigated. The dependence of peak height on concentration of surfactant, preconcentration time, and preconcentration potential was examined. To improve the analytical signal of Oxetals C114 and T105, the influence of methanol on their tensammetric curves was investigated. Roughly, all the surfactants exhibit two peaks: a wide one, corresponding the monomer form, which shifts toward the negative direction with an increase in concentration, and a narrow one, corresponding to the associate form, whose position is stable. Oxetals C114 and T105 exhibit additional peaks, which complicate the determination. The addition of 20% of methanol removes such difficulties and only one peak remains.
Biosensors into the 1990s
Authors: Rechnitz Garry A.
Published: May 2005

The current status and future prospects for biosensors are viewed from a personal perspective of 30 years. It is suggested that the principal obstacles to progress in the biosensor field are at least as much human and organizational as scientific or technical.
Electroluminescence
Authors: Velasco Jaime González
Published: May 2005

A definition of electrogenerated luminescence (ECL) is given. Chemiluminescent reactions of different kinds are cited, as well as various types of pathway to the formation of the emitting excited state. After a consideration of the energetic and kinetic requirements for ECL‐producing reactions, the experimental conditions are examined. The important concept of ECL efficiency is introduced, as well as the feasibility of elucidating the mechanisms of ECL reactions. Some interesting new ECL systems are mentioned, together with examples of analytical applications of such schemes.
Immobilized enzyme carbon paste electrodes as amperometric sensors
Authors: Lorenzo E. , González E. , Pariente F. , Hernández L.
Published: May 2005

The construction and performance of new carbon paste enzyme electrodes as amperometric sensors is described. Xanthine oxidase and alkaline phosphatase have been adsorbed on a carbon paste electrode (CPE), and physically entrapped with a semipermeable membrane. The product of enzymatic reaction, uric acid or p‐nitrophenol, was electrochemically oxidized versus an Ag/AgCl electrode at +0.4 or +0.8 V, respectively, yielding a steady‐state current directly related to the substrate concentration. Response characteristics as well as kinetic parameters have been evaluated.
pH‐ISFET with NMOS technology
Authors: Alegret S. , Bartrolí J. , Jiménez C. , del Valle M. , Domínguez C. , Cabruja E. , Merlos A.
Published: May 2005

The construction of a pH‐ISFET (ion‐selective field effect transistor) fabricated with standard negative‐channel MOS technology, compatible with complementary MOS technology, and using silicon nitride as a pH‐sensitive material, is described. Its main analytical characteristics are discussed. The resulting calibration plot is linear over the pH range from 2 to 11; with a slope of 54 mV per pH unit.
Voltammetric determination of cadmium on a carbon paste electrode modified with a chelating resin
Authors: Agraz Raquel , Sevilla M. Term , Pinilla Jose M. , Hernandez Lucas
Published: May 2005

A method is described for determination of cadmium using a carbon pas electrode modified with Amberlite IRC 718 chelating resin and voltammetric measurement of the collected ion. Optimal conditions for the preconcentration of cadmium were 10 minutes stirring at open circuit in 0.001 M ammonium buffer, pH 9. For electrochemical measurements, the optimal parameters include the use of a 0.1 M HCl solution, a delay time of 36 seconds at −1.1 V (vs. Ag/AgCl) and a 400 mV/s scan rate. The well‐defined anodic peak at −0.7 V obtained is adequate for the quantitation of cadmium at very low concentration levels, with a detection limit of 0.005 mg/L. The method was used with good results for the determination of cadmium in polluted river waters.
Electrochemical behavior of the psychotropic drug pivazepam in determinations in pharmaceutical formulations and in urine
Authors: Rivera Paloma , Bermejo Esperanza , Zapardiel Antonio , López José Antonio Pérez , Hernández Lucas
Published: May 2005

The electrochemical reduction of pivazepam was investigated by differential pulse polarography. Reduction of the drug was carried out in one irreversible, diffusion‐controlled step using Britton–Robinson buffers. The peak potential at pH 5.0 and 10% methanol–water solutions was −0.95 V (vs. Ag/AgCl/3M KCl). Pivazepam can be determined (down to the nanomolar level) by using adsorptive preconcentration prior to the differential pulse voltammetric scan. The applicability to assays of commercial preparations and human urine is described. The detection limit was 15 ng per milliliter of urine with 60 seconds adsorption, and the mean standard deviation was lower than 4.6% for 200 ng/mL sample (n = 5, 60 seconds), with a mean recovery of 82%.
Voltammetric determination of cocaine in confiscated samples
Authors: Abedul María Teresa Fernández , Rodríguez José Ramón Barreira , García Agustín Costa , Blanco Paulino Tuñón
Published: May 2005

The electrochemical behavior of the abuse drug cocaine has been studied. Cocaine undergoes an irreversible oxidation process on carbon paste electrodes. It was calculated that 2 electrons were involved, and the value obtained for the charge transfer coefficient was 0.362 ± 0.006. Comparative voltammetric experiments yielded an estimated diffusion coefficient value for cocaine of 0.27 × 10−5 cm2 s−1. A linear calibration plot from 1.0 × 10−6 to 1.0 × 10−4M was obtained by using a scan rate of 50 mV s−1. A simple and reproducible procedure is proposed for the determination of cocaine in illegal dosage forms confiscated by police authorities; the results agree with those of a HPLC‐UV method.
Determination of Dinoseb by adsorptive stripping voltammetry
Authors: Pedrero María , de Villena F. Javier Manuel , Pingarrón José M. , Polo Luis M.
Published: May 2005

A sensitive method is described for the determination of Dinoseb (2‐sec‐butyl‐4, 6‐dinitrophenol) at nanomolar levels by adsorptive stripping voltammetry (AdSV) at the hanging mercury drop electrode. Cyclic voltammetry studies showed two well‐defined reduction peaks, at −0.21 and −0.36 V, and demonstrated the adsorption of Dinoseb and its intermediate reduction product on the electrode. A systematic study of the experimental parameters that affect the stripping response was carried out using differential pulse voltammetry. Using a 120 second adsorption time, the limits of determination and detection were 1.5 × 10−9 and 4.6 × 10−10 M, respectively, and the relative standard deviation (n = 10) was 3.9% at a concentration level of 6.0 × 10−9 M.
Fluoride and chloride determination in cheese with ion‐selective electrodes
Authors: González M. A. , Aller A. J. , Pardo R. , Barrado E. , Deban L.
Published: May 2005

We studied the possibility, of using ion‐selective electrodes (ISEs) for the determination of chloride and fluoride anions in cheese samples. For chloride, we propose the use of potentiometric titration with silver and direct potentiometry, whereas for fluoride, best results were obtained with a standard additions method. The proposed procedures have been applied to Spanish cheese samples. Chloride was found in all samples in concentrations ranging between 3200 and 25,000 g/kg. Fluoride was present only in some types of cheese, in concentrations lesser than 0.7 mg/kg.
Electrochemistry of cyclodextrins and cyclodextrin inclusion complexes
Authors: Bersier Pierre M. , Bersier Jacques , Klingert Bernd
Published: May 2005

The state of the art of the electrochemistry of α‐, β‐, and γ‐cyclodextrins (CDs) and cyclodextrin inclusion complexes and their polarographic and voltammetric assay are reviewed. The polarographic and voltammetric determination of physicochemical parameters of CD inclusion complexes are discussed. Practical applications of adsorption and inclusion effects for electroanalytical purposes are presented future prospects are discussed, and 95 references are given.
Flow injection stripping analysis
Authors: Luque Castro M. D. De , Izquierdo A.
Published: May 2005

A review of the two main electrochemical stripping techniques (voltammetric and potentiometric), associated with flow injection analysis (FIA), is presented. The versatility and flexibility provided by the FIA, manifold for performing unique stripping procedures such as medium exchange, flow reversal, and subtractive operation are evaluated. The instrumentation, features and applications of these associations are critically discussed, and unexplored possibilities are commented on. These developments are summarized in 58 references.
The determination of trace levels of iron in seawater, using adsorptive cathodic stripping voltammetry
Authors: Van Berg C. M. G. Den , Nimmo M. , Abollino O. , Mentasti E.
Published: May 2005

A sensitive procedure to determine trace levels of iron in, seawater is proposed which utilizes adsorptive deposition of the complex of Fe(III) with 1‐nitroso‐2‐naphthol (1‐N‐2‐N) on the mercury drop electrode. Optimized conditions include a solution concentration of 20 μM 1‐N‐2‐N and a pH of 6.9; an adsorption potential of −0.25 V is applied, and the potential scan is in the linear sweep mode. The limit of detection is 0.2 nM Fe using a deposition time of 10 minutes. Peak instability due to adsorption of Fe(III) on either the voltammetric cell or rejected mercury drops is eliminated by addition of hydroxylammonium, which reduces the dissolved Fe(III) to Fe(II). The reaction mechanism of the analytical procedure therefore includes oxidation of Fe(II) to Fe(III) at the electro surface with the subsequent complexation by 1‐N‐2‐N and adsorption on the mercury drop; the reduction current of the adsorbed and complexed, Fe(III) is then measured.
Cobalt‐porphyrin‐nafion film on carbon microarray electrode to monitor oxygen for enzyme analysis of glucose
Authors: Dong Shaojun , Kuwana Theodore
Published: May 2005

A microcarbon array electrode was modified by the placement of a Nafion film containing cobalt tetra‐methylpyridyl phorphyrin on its surface. This electrode was applied to the analysis of solution glucose when it was further modified by the immobilization of glucose oxidase on the outermost surface of the Nafion by the cross‐linking of serum albumin with glutaraldehyde. The concomitant decrease in the concentration of oxygen, as it was consumed in the enzymatic reaction of glucose with glucose oxidase, was determined by either cyclic voltammetry or a double potential step method at the porphyrin‐Nafion catalytic electrode. Glucose could be determined in the range, of 0.01‐;4 mM rapidly, without interference from substances such as accurate or other saccharides.
Tensammetric and indirect amperometric detection of phospholipids
Authors: Schmidt Thomas , Emons Hendrik
Published: May 2005

Electrochemical detection procedures for electroinactive phospholipids were developed for flow injection (FI) systems and high performance liquid chromatography (HPLC). The methods are based on the adsorption of these surface‐active compounds, which was characterized in solutions containing acetonitrile, water, and methanol. Tensammetric FI detection at mercury electrodes was systematically studied with respect to various experimental parameters. The method was also applied to the normal phase HPLC determination of phospholipids, but with higher detection limits. In addition, an indirect amperometric detection method based on the inhibition effect of adsorbed phospholipids on electrode reactions at glassy carbon fibers was explored. This can be also used for FI systems and in HPLC. Significantly wide linear dynamic ranges were obtained for the determination of phospholipids.
Enzymatic determination of ethanol by flow injection analysis using a Kel‐F wax carbon paste electrode
Authors: Wangsa Julie , Danielson Neil D.
Published: May 2005

Surface passivation during oxidation of NADH at a fluorocarbon polymer‐carbon paste electrode (CPE) was about 25% less than that of the glassy carbon or Nujol‐oil CPE. After repeated injections of 1.5 mM NADH for 12 h, the Kel‐F wax CPE maintained about 85% of its initial response. The determination of ethanol in wine samples using soluble alcohol dehydrogenase stabilized by polyethyleneglycol was demonstrated. Linearity of response extended from the detection limit of 0.44 mM to 33 mM.
Microarray electrodes as biosensors
Authors: Sohn Tae‐Won , Stoecker Paul W. , Carp Wendy , Yacynych Alexander M.
Published: May 2005

Microdisk and microhole array electrodes were used to construct amperometric glucose biosensors based on the detection of hydrogen peroxide. All‐chemical methods such as platinization, glucose oxidase immobilization, and electropolymerization permit electrodes of any size, shape, or surface complexity to be used for biosensors. This also gives the biosensor surface a multifunctional character, where the platinization decreases the operating potential, the immobilized enzyme provides the specificity, and the electropolymerized film prevents interferences and fouling. All of these functions are accomplished in a layer that is about 10 nm thick. The microdisk and microhole biosensors were linear to about 3 mM and 4 mM glucose, respectively, and were accurate, as checked by standard reference serum.
Hg(II) voltammetry on a 1,5‐diphenylcarbazide containing carbon paste electrode
Authors: Navrátilová Zuzana
Published: May 2005

The differential pulse voltammetric determination of Hg(II) at a carbon past electrode modified by 1,5‐diphenylcarbazide is described. Voltammetry of Hg(II) on various types of modified electrodes in 0.1 M KSCN (pH = 2) was studied. A detection limit 5 × 10−9 M was achieved at the carbon paste electrode containing 5% of 1,5−diphenylcarbazide in this background electrolyte.
Mercury ion‐selective polymeric membrane electrodes based on substituted diaza crown ethers
Authors: Brzozka Zbigniew , Pietraszkiewicz Marek
Published: May 2005

The potentiometric selectivities of membranes based on new N, N' ‐substituted 4, 13‐diaza‐18‐crown‐6 ethers were determined under different internal filling electrolytes and conditioning time of the membranes. The preference of Hg2+ over other divalent cations was observed for compounds bearing 2‐methylquinolyl or 2‐methylquinolyl‐1‐oxide groups. The membrane electrodes with ionophores 1 and 2 exhibited a linear response in the activity range 10−5 − 10−3 M Hg(NO3)2.
Enzyme electrodes with pyrolyzed CoTMPP catalyst
Authors: Gamburzev S. , Iliev I. , Atanasov P. , Kaisheva A. , Scheller F. , Pfeifer D.
Published: May 2005

Catalytic electrode with pyrolyzed cobalt‐tetramethoxy‐phenylporphyrine (CoTMPP) for facilitating the anodic detection of hydrogen peroxide is investigated. This modified electrode can operate at potentials lower (by ca. 0.2 V) than a platinum electrode. The electrode is tested in membrane enzyme biosensors for the determination of glucose and lactate in water solutions.
Nucleoside oxidase‐modified carbon paste electrode containing quinone: Cathodic current response to nucleosides
Authors: Ikeda Tokuji , Hashimoto Yutaka , Senda Mitsugi , Isono Yoshikazu
Published: May 2005

The cathodic current for the reduction of benzoquinone at a glassy carbon electrode was increased in the presence of nucleoside oxidase and inosine. This was attributed to the regeneration of benzoquinone from hydroquinone by the laccaselike reaction of the enzyme, the rate of which depended on the concentration of inosine in the solution. Accordingly, an enzyme electrode for nucleosides was constructed by immobilizing nucleoside oxidase behind a dialysis membrane on a carbon paste electrode containing p‐benzoquinone or hydroquinone. The current response of the electrode to nucleosides was studied and the results were discussed on the basis of the laccaselike activity of the enzyme. The nucleoside oxidase‐modified electrode was tested as an amperometric enzyme electrode for nucleosides and could be used at least for three weeks.
Studies on the electrochemical behavior of 2‐(3,5‐dibromo‐2‐pyridyl)azo‐5‐diethylaminophenol‐co(II) complex in the presence of nitrite: Trace, measurements of cobalt
Authors: Zhao Zaofan , Cai Xiaohua , Pei Jianhong , Zhang Yeming , Zhou Xingyao
Published: May 2005

In an acetate acid buffer solution (pH = 4.5) containing 2‐(3,5‐dibromo‐2‐pridyl)azo‐5‐diethylaminophenol or 3,5‐2Br‐PADAP and nitrite, there is a catalytic single‐sweep polarographic peak that is very sensitive and selective to cobalt(II). The linear range is from 1 × 10−10 M to 1 × 10−6 M, with a detection limit of 5 × 10−11 M. Most common cations and anions do not interfere with the determination. The method has been used or the determination of trace cobalt in human hair and pure nickel nitrate samples. The mechanism involved has been investigated by various electrochemical methods, and the catalytic process is magnified image.
Theory of potentiometric stripping analysis in the case of reversible and quasi‐reversible electrode reactions
Authors: Garai Tibor , Mészáros Lajos , Bartalits Liliana , Locatelli Clinio , Fagioli Francesco
Published: May 2005

The theoretical treatment of potentiometric stripping analysis is presented for the cases of reversible and quasi‐reversible electrode reactions. The experimental results were found to be in good agreement with calculated data. Derivations based on different assumptions (e.g., stripping in stirred solutions, diffusion layer of constant thickness) are compared.
The determination of iron in seawater using catalytic cathodic stripping voltammetry
Authors: Yokoi Kunihiko , van den Berg Constant M. G.
Published: May 2005

The sensitivity of the determination of iron in natural waters, including seawater, using cathodic stripping voltammetry (CSV) with adsorptive collection of complexes with 1‐nitroso‐2‐naphthol is greatly enhanced by catalytic reoxidation in the presence of hydrogen peroxide. The limit of detection is lowered to 0.16 nM Fe (using an adsorption time of 60 s) and further to 0.03 nM Fe by increasing the adsorption time to 10 min. Interference from an increase in the background current, brought about by catalysis of the hydrogen evolution, is overcome by addition of an anionic surfactant (sodium dodecyl sulfate (SDS)). Optimal conditions include a hydrogen peroxide concentration of 1.8 mM and 5 ppm SDS. Procedures to purify the reagents from contaminant levels of iron are described. The method is successfully applied to certified seawater and samples from the North Atlantic.
Voltammetric behavior of dihydronicotinamide adenine dinucleotide phosphate at enzyme‐modified electrodes
Authors: Hua Chi , Walsh Sean , Smyth Malcolm R. , Švancara Ivan , Vytřas Karel
Published: May 2005

The oxidation of nicotinamide‐adenine dinucleotide phosphate (reduced form, NADPH) at glassy carbon electrodes modified with different enzymes has been studied. It was found that NADPH yielded a well‐defined anodic peak about +0.70 V (vs. Ag/AgCl) at glassy carbon electrodes coated with three different enzymes, glutathione reductase, glutathione peroxidase, and glucose oxidase, in 1.4 M potassium phosphate supporting electrolyte. It was confirmed that the enzymes immobilized at the working electrode surface reduced the overpotential for the oxidation of NADPH. This method provides a way to study the mechanism of some enzymatic reactions.
Photoelectrochemical detection and speciation of thallium (I) and thallium (III)
Authors: Barisci Joseph N. , Wallace Gordon G.
Published: May 2005

A method that allows speciation and electrochemical detection of thallium in flowing solutions has been developed. Thallous ions are determined using oxidative detection at a platinum electrode in a sulphuric acid‐formic acid solution. In the presence of thallic ions, iiradiation of the solution with UV light induces the reduction of Tl(III) to Tl(I) which is subsequently detected as described above. Under these conditions total thallium is determined. Irradiation of the flowing solution is carried out within the detector flow cell.
Automated system for on‐line adsorptive stripping voltammetric monitoring of trace levels of uranium
Authors: Wang Joseph , Setiadji Rossi , Chen Liang , Lu Jianmin , Morton Stephen G.
Published: May 2005

An automated system for on‐line monitoring of trace uranium, based on a flow‐through adsorptive stripping operation, is described. The on‐line formation of the uranium‐oxine complex is followed by its adsorptive accumulation and voltammetric quantitation at the downstream working electrode. About 10–60 runs can be made every hour with high reproducibility (RSD of 3–5%) and a detection limit of 0.7 μg/L. The dependence of the peak current on different experimental variables is reported. The sequence of events involved in the adsorptive stripping voltammetric cycle is controlled by a computer. Analogous on‐line monitoring of chromium (VI) are also reported with 36 runs/h (2.1% RSD), and detection limit of 1.5 μg/L. The system holds great promise for field‐based operation.
Amount adsorbed in adsorption voltammetry. Part 2. Amount adsorbed in the adsorption accumulation at a symmetric spherical electrode during the rest period
Authors: Jin Wenrui , Hou Yongchun , Yan Changtai , Wang Jianyan , Sun Changlin
Published: May 2005

The equation for the amount absorbed in adsorptive accumulation at a symmetric spherical electrode, during the rest period (under strong adsorption conditions) has been derived:
equation image
.

The equation has been verified experimentally. The equation for the total amount adsorbed in adsorption voltammetry at a symmetric spherical electrode is
equation image
.
Development of an amperometric assay for the determination of reduced glutathione, using glutathione peroxidase and screen‐printed carbon electrodes chemically modified with cobalt phthalocyanine
Authors: Wring Stephen A. , Hart John P. , Birch Brian J.
Published: May 2005

The systematic characterization and optimization of bovine erythrocyte glutathione peroxidase is described, together with its application in an assay employing amperometry in stirred solutions for the determination of endogenous levels of reduced glutathione (GSH). Initial studies employed UV spectroscopy, cyclic voltammetry, and amperometry in stirred solutions (to construct hydrodynamic voltammograms) for several investigations including the selection of a suitable hydroperoxide second substrate, the investigation of solution conditions on the enzyme reaction rate, and reconstituted enzyme stability. Subsequently, amperometry in stirred solutions was used to monitor the enzyme‐catalyzed rate of GSH oxidation and to construct calibration plots over the concentration range 10 to 50 μM (corresponding to normal circulating GSH levels after the envisaged sample preparation step consisting of a simple twenty fold dilution of whole blood). Enzyme selectivity studies were performed using several potential physiological interferents and selected pharmaceuticals that may be encountered in the circulation of patients being treated for rheumatoid arthritis. The coefficient of variation for the enzyme linked amperometric assay was 7.28% (n = 5) for solutions containing 40 μM GSH.
A comparative study of the cylindrical wire, thin‐layer, and wall‐jet detector cells for the deterrnination of inorganic arsenic by ion exclusion chromatography with constant and pulsed amperometric detection
Authors: Stojanovic R. S. , Bond A. M. , Butler E. C. V.
Published: May 2005

An ion chromatographic method for the separation and determination of As(III) empolying both constant and pulsed potential amperometric detection at platinum electrodes has been compared using cylindrical wire, thin layer, and wall‐jet flow cell detectors. Operational parameters such as limit of detection, linear dynamic range, stability, reproducibility, and flow rate dependence are reported for each detector cell. The different detector designs have features which make them individually appealing, depending on the type of application being considered and which operational parameter is most important. However, the limit of detection with the wall‐jet electrode of 1 × 10−9 M is superior to the other electrode designs (this may not necessarily be the case for other analytes) and makes this the preferred method for the determination of arsenic in bottled mineral water. Additionally, a lower limit of detection is achieved with constant potential amperometric detection than is the case with pulsed potential amperometric detection, which suggests that pulsed methods may not be advantageous for the detection of species at potentials where a large background current is exhibited at very positive potentials as required for the determination of arsenic.
Indirect amperometric detection of reducible analytes using a reductor column
Authors: Halasz J. , Horvai G.
Published: May 2005

Anodic amperometric detection of reducible analytes like nitrate ion, organic nitrates and nitro compounds is possible after on‐line reduction on a cadmium reductor column. HPLC application is limited by the dispersion in the reductor column.
The number of components in noisy data from a swept‐potential electrochemical detector
Authors: Msimanga Huggins Z. , Sturrock Peter E.
Published: May 2005

Experimental data obtained from a conventional HPLC using a swept‐potential electrochemical detector are analyzed for the number of components present under varying conditions of signal‐to‐noise (S/N) ratios. The autocorrelation, multiple determination, and single‐vector uniqueness test functions are evaluated under low S/N conditions, and also tested on Fourier‐smoothed data. The autocorrelation and multiple determination functions give good predictions down to the S/N ratio of 2.4. Below this value the autocorrelation function gives fewer counts of the components than expected as the components signal becomes buried in the background noise. On the other hand, the multiple determination function gives too many counts of the components actually present. The single‐vector uniqueness test function proves to be superior to the other two. Its predictions are more consistent even at S/N ratios lower than 2.4 Data smoothing significantly improves the performance of all three functions.
Sensitive yeast bioelectrode to L‐lactate
Authors: Kulys Juozas , Wang Lizhong , Razumas Valdemaras
Published: May 2005

Amperometric L‐lactate bioelectrodes based on carbon paste chemically modified with yeast Hansenula anomala and mediators are described. The bioelectrodes acted over a potential range at 0.05 – 0.3 V (vs SCE), the sensitivity was 14 – 116 μM−1 cm−2 and optimum pH was at 7.6 – 7.7. The apparent Michaelis constant for the calibration curves of bioelectrodes was different for mediators and varied in the range from 1.3 to 18.9 mM of L‐lactate. The bioelectrode was insensitive to glucose and ethanol. The bioelectrode's response to ascorbic acid was 1.4% at the normal physiological level of vitamin C and L‐lactate in blood. The bioelectrode was used for L‐lactate determination in serum, and remained stable for more than 2 months. The biocatalytic action of the cytochrome b2 in yeast was suggested.
Differential pulse anodic stripping voltammetric determination of trace bismuth in minerals with nafion mercury film modified electrode
Authors: Liu Kuai‐Zhi , Wu Qing‐Gro
Published: May 2005

An electrode for the differential pulse anodic stripping voltammetric determination of trace bismuth in mineral has been made by coating glassy carbon with Nafion. The sensitivity is enhanced by the ion‐exchange character of the Nafion film. A detection limit of 1 × 10−11 M has been obtained after electrodeposition for 16 min. The overlapping interference of Sb is addressed successfully. The method is sensitive, simple, and relatively rapid, with good reproducibility.
Determination of mercury on a carbon paste electrode modified with humic acid
Authors: Navrátilová Zuzana , Kula Petr
Published: May 2005

The binding of Hg(II) with humic acid, incorporated into the carbon paste electrode, was verified. This modified humic acid electrode was used for the trace determination of Hg(II). The differential‐pulse voltammetry on the electrode modified with humic acid yielded good performance over the concentration range 5 × 10−8–5 × 10−7 M Hg(II). Only Cu(II) interferes with the determination.