bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrochemistry of DNA at Single‐Wall Carbon Nanotubes
Authors: Wang Jianxiu , Li Meixian , Shi Zujin , Li Nanqiang , Gu Zhennan 
Published: January 2004

AbstractSingle‐wall carbon nanotubes (SWNTs) can be used as an electrochemical probe to study the electrochemical oxidation of DNA, two voltammetric oxidation peaks corresponding to electrochemical oxidation of guanine and adenine residues in DNA could be observed, demonstrating a new potential application of SWNTs in DNA analysis. Compared to other types of electrode materials, the electrochemical response of natural DNA was greatly enhanced at the SWNT‐modified electrode. This method can be used to investigate the interaction of SWNTs with DNA.
Nanotube Membrane Based Biosensors
Authors: Kohli Punit , Wirtz Marc , Martin Charles R. 
Published: January 2004

AbstractWe review highly sensitive detection based on electrochemical methods. These methods are based on monodisperse gold and alumina nanotubule membranes with inside diameter approaching molecular dimensions. The analyte species can be detected by measuring a change in trans‐membrane current when the analyte is added to the nanotubule‐based cell. The second method entails the use of a concentration change based on the nanotubule membrane. Biomemtic ion‐gated channels micropore and nanotubule membrane sensors are also reviewed. These synthetic ion channels can be switched from an “off” state to an “on” state in response to an external chemical stimulus. Using these methods, we have achieved detection limits as low as 10 pM. Potential applications for these biosensors are in fields such as bioanalytical, biomedical, pharmaceutical and drug discovery.
The Electrochemical Behavior of Hemoglobin on SWNTs/DDAB Film Modified Glassy Carbon Electrode
Authors: Yang Peilin , Zhao Qiang , Gu Zhennan , Zhuang Qiankun 
Published: January 2004

AbstractThe SWNTs/DDAB film modified glassy carbon electrode was successfully prepared to study the electrochemical behavior of hemoglobin (Hb). A better electrochemical response was observed than that on the DDAB or SWNTs film modified electrode. Cyclic voltammetry of Hb showed two pairs of well‐defined and nearly reversible peaks. The electrochemical reaction of hemoglobin on the SWNTs/DDAB film modified electrode was controlled by absorption. Using the SWNTs/DDAB film modified electrode, the interaction between hemoglobin and tar was studied.
Constant‐Distance Mode Scanning Electrochemical Microscopy. Part II: High‐Resolution SECM Imaging Employing Pt Nanoelectrodes as Miniaturized Scanning Probes
Authors: Ballesteros Katemann Bernardo , Schulte Albert , Schuhmann Wolfgang 
Published: January 2004

AbstractThe potential of needle‐type Pt disk nanoelectrodes as extremely miniaturized scanning probes for high resolution scanning electrochemical microscopy (SECM) was investigated. The accuracy of a piezoelectric shear‐force based distance control allowed a precise positioning of the Pt nanoelectrodes in close proximity to the surface of interest not only in tip approach experiments but also throughout scanning and SECM imaging. As proof of the advanced quality of SECM imaging, high‐resolution current and topography images of a three‐dimensional LIGA microstructure will be presented both simultaneously acquired by operating Pt nanoelectrodes in the constant‐distance mode of SECM.
A Novel Amperometric O2 Gas Sensor Based on Supported Room‐Temperature Ionic Liquid Porous Polyethylene Membrane‐Coated Electrodes
Authors: Wang Rong , Okajima Takeyoshi , Kitamura Fusao , Ohsaka Takeo 
Published: January 2004

AbstractA novel solid‐state amperometric O2 gas sensor based on the supported 1‐ethyl‐3‐methylimidazolium tetrafluoroborate (EMIBF4) porous polyethylene membrane‐coated electrodes has been proposed with its characterization. By electrochemical impedance technique, the ionic conductivity of the supported EMIBF4 membrane was estimated to be ca. 0.6 S m−1, indicating that the supported EMIBF4 membrane (the thickness: 50 μm) can be used as a solid state ionic conductor at room temperature. The cyclic voltammograms obtained for the one‐electron redox reaction of O2/O2−.(O2−.: superoxide ion) couple at high scan rates (>100 mV s−1) showed a couple of usual redox peaks, while at low scan rates (<30 mV s−1) S‐shaped steady‐state voltammograms similar to those obtained by rotating disk voltammetry were obtained. These results were explained on the basis of the mass transport of O2 at the supported EMIBF4 membrane‐coated electrode system. The transient and steady‐state reduction currents for the reduction of O2 to O2−.as well as the transient oxidation current for the reoxidation of O2−.to O2, which were obtained by potential‐step chronoamperometry, could be used to measure the change of O2 concentration in O2‐N2 mixed gas stream. The present O2 gas sensor demonstrated a wide detection range, a high sensitivity and an excellent reproducibility.
Attachment of Ferrocene‐Capped Gold Nanoparticle/Streptavidin Conjugates onto Electrode Surfaces Covered with Biotinylated Biomolecules for Enhanced Voltammetric Analysis
Authors: Baca Alfred J. , Zhou Feimeng , Wang Jun , Hu Jingbo , Li Jinhua , Wang Jianxiu , Chikneyan Zarui S. 
Published: January 2004

AbstractFerrocene (Fc)‐capped gold nanoparticle/streptavidin conjugates were attached onto electrodes covered with either biotinylated oligodeoxynucleotides (ODNs) duplexes or N‐biotinoyl‐N′‐(6‐maleimidedohexanoyl)hydrazide that had been preadsorbed onto the reduced form of glutathione (GSH) immobilized onto a dithiobissuccinmidyl propionate self‐assembled monolayer (SAM). Effects of the DNA probe and target strand lengths on the voltammetric behavior of the Fc groups residing at the nanoparticle conjugates were studied. The voltammetric behavior was also compared to that arising from the Fc groups present at the end of the ODN duplex in a sandwich complex (Wang et al. Anal. Chem. 2003, 75, 3941). It was found that shorter duplexes would lead to a more reversible voltammetric wave. However, the formation of duplexes with a greater number of base pairs will result in a lower detection level. For the analysis of a biotinylated 30mer target at a mixed SAM of a 30mer probe and hexanethiol, a concentration level as low as 0.25 pM could be detected (which is even lower than our previously reported detection level of 2 pM for an ODN sandwich complex). The detection level for GSH (1 nM) was found to be comparable to those of many other analytical techniques. The capability of our method for trace analysis of biotinylated biomolecules can be attributed to the enhanced voltammetric detection by the large number of Fc moieties present at each conjugate. The method described herein is simple, reproducible, versatile, and selective, and does not require sophisticated analytical instrumentation.
Electrochemical Detection of PCR Amplicons Using Electroconductive Polymer Modified Electrode and Multiple Nanoparticle Labels
Authors: Li Lu‐Lu , Cai Hong , Lee Thomas Ming‐Hung , Barford John , Hsing I‐Ming 
Published: January 2004

AbstractWe report the utilization of an oligonucleotide‐functionalized electroconducting polymer, coupled with a nanoparticle‐based hybridization indicator for a sensitive detection of multi‐labeled PCR amplicons. The electroconducting polymer permits the immobilization of an active probe onto the transducer surface. In this work, 2‐aminobenzoic acid is electropolymerized onto an indium tin oxide electrode. The coated film has carboxyl groups for the immobilization of amino‐terminated probe, mediated by coupling agents of water‐soluble carbodiimide and N‐hydroxysulfosuccinimide. This coupling chemistry has minimal nonspecific adsorption of the gold nanoparticle indicator, leading to a low background signal allowing a more sensitive hybridization detection. Signal transduction of the hybridization event is achieved through a series of steps: i) the binding of the gold nanoparticle label to the hybridized target based on streptavidin‐biotin interaction, ii) the catalytic silver deposition onto the gold label (i.e., the silver enhancement) and iii) potentiometric stripping analysis of the deposited silver. In addition to signal amplification by silver enhancement, multiple‐labeling of the amplicons by the incorporation of biotin‐16‐dUTP is employed to further enhance the signal to background ratio. The sequence‐specific identification of both symmetric and asymmetric PCR amplicons is also demonstrated.
Electrochemistry in the Presence of Mesoporous TiO2 Phytate Nanofilms
Authors: McKenzie Katy J. , Marken Frank , Oyama Munetaka , Gardner Catherine E. , Macpherson Julie V. 
Published: January 2004

AbstractThin composite organic – inorganic membranes are formed at electrode surfaces via a layer‐by‐layer deposition process employing TiO2 nanoparticles and phytic acid as molecular binder. The mesoporous membranes form uniformly across platinum and glass surfaces and are shown via conducting atomic force microscopy (C‐AFM) to behave in dry state as electrically insulating films. Voltammetry at platinum electrodes of 1.5 mm, 100 μm, and 10 μm diameter is used to survey the effect of the composite membrane on electrochemical processes. The electrode diameter as well as concentration and nature of electrolyte have a considerable effect on the electrode process. For the one electron reduction of Ru(NH3)$\rm{ {_{6}^{3+}}}$ in aqueous media adsorption effects, mobility effects, and accumulation or ‘memory’ effects are observed. Similarly, protons or cationic molecules such as dopamine can be accumulated and ‘stored’ in the membrane and then transferred to a clean electrolyte for analysis.
Amplified Electrical Transduction of DNA Hybridization Based on Polymeric Beads Loaded with Multiple Gold Nanoparticle Tags
Authors: Kawde Abdel‐Nasser , Wang Joseph 
Published: January 2004

AbstractA new strategy for amplifying particle‐based electrical DNA detection based on oligonucleotides functionalized with polymeric beads carrying numerous gold nanoparticle tags is described. The gold‐tagged beads were prepared by binding biotinylated metal nanoparticles to streptavidin‐coated polystyrene spheres. Such use of carrier‐sphere amplification platforms is combined with catalytic enlargement of the multiple gold tags and an ultrasensitive electrochemical stripping detection of the dissolved gold tags. The gold‐nanoparticle loaded beads and the resulting DNA‐linked assembly were characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Factors affecting the performance have been optimized. Such amplified electrical transduction allows detection of DNA targets down to the 300amol level, and offers great promise for ultrasensitive detection of other biorecogntion events.
Sensing with Nafion Coated Carbon Nanotube Field‐Effect Transistors
Authors: Star Alexander , Han Tzong‐Ru , Joshi Vikram , Stetter Joseph R. 
Published: January 2004

AbstractSequential CVD and CMOS processes were used to make a FET that has single walled carbon nanotubes to serve as the conducting source to drain channel. This structure can be decorated to provide gas and liquid responses and herein is evaluated as a humdity sensor. The Na+, K+, and Ca2+ ion‐exchanged Nafion polymer acts as the chemically sensitive layer in this electrochemical sensor. The effect of gate voltage on the charge‐sensitive NT structure was found to be RH dependent over the range of 12–93% RH with msec response time.
Nanoengineered Encapsulation of Mediator Microcrystals and Their Use as a Non‐metallic Label System for the Silver Enhancement Technique
Authors: Cheung Mak Wing , Li Yongjun , Keung Lau Wan , Trau Dieter 
Published: January 2004

AbstractWe report on the nanoengineered encapsulation and functionalization of mediator microcrystals and their use as a non‐metallic bioassay label system for the silver enhancement technology. Mediator microcrystals were encapsulated and functionalized by using a Layer‐by‐Layer (LbL) based approach. This is a generic way to transform most low‐soluble mediators (e.g., ferroceneacetic acid) into a label for electrochemical bioassays. Instead of using conventional gold particles, encapsulated mediator microcrystals are used as the primary label for the silver enhancement technique. After the biorecognition reaction the unbound labels were separated and a silver(I) ion solution was added. The mediator reduces silver ions into metallic silver and the mediator microcrystal was transformed into a silver particle. Consecutively a reducing agent was added leading to a further silver growth, representing the silver enhancement step. A large amount of silver was developed from the mediator, resulting in signal amplification. The amount of developed silver was studied in a bioassay and was found proportional to the analyte concentration.
Electroanalytical and Bioelectroanalytical Systems Based on Metal and Semiconductor Nanoparticles
Authors: Katz Eugenii , Willner Itamar , Wang Joseph 
Published: January 2004

AbstractMetal, semiconductor and magnetic particles act as functional units for electroanalytical applications. Metal nanoparticles provide three important functions for electroanalysis. These include the roughening of the conductive sensing interface, the catalytic properties of the nanoparticles permiting their enlargement with metals and the amplified electrochemical detection of the metal deposits and the conductivity properties of nanoparticles at nanoscale dimensions that allow the electrical contact of redox‐centers in proteins with electrode surfaces. Also, metal and semiconductor nanoparticles provide versatile labels for amplified electroanalysis. Dissolution of the nanoparticle labels and the electrochemical collection of the dissolved ions on the electrode followed by the stripping‐off of the deposited metals represents a general electroanalytical procedure. These unique functions of nanoparticles were employed for developing electrochemical gas sensors, electrochemical sensors based on molecular‐ or polymer‐functionalized nanoparticle sensing interfaces, and for the construction of different biosensors including enzyme‐based electrodes, immunosensors and DNA sensors. Semiconductor nanoparticles enable the photoelectrochemical detection of analytes. Several studies have revealed the photocurrent generation by enzyme‐mediated processes and as a result of DNA hybridization. Magnetic particles act as functional components for the separation of biorecognition complexes and for the amplified electrochemical sensing of DNA or antigen/antibody complexes. Also, electrocatalytic and bioelectrocatalytic processes at electrode surfaces are switched by means of functionalized magnetic particles and in the presence of an external magnet.
Disposable Carbon Nanotube Modified Screen‐Printed Biosensor for Amperometric Detection of Organophosphorus Pesticides and Nerve Agents
Authors: Lin Yuehe , Lu Fang , Wang Joseph 
Published: January 2004

AbstractA disposable carbon nanotube‐based biosensor was successfully developed and applied to the detection of organophosphorus (OP) pesticides and nerve agents. The biosensors using acetycholinesterase (AChE)/choline oxidase (CHO) enzymes provided a high sensitivity, large linear range, and low detection limits for the analysis of OP compounds. Such characteristics may be attributed to the catalytic activity of carbon nanotube to promote the redox reaction of hydrogen peroxide produced during AChE/CHO enzymatic reactions with their substrate, as well as the large surface area of carbon nanotube materials.
Analysis of RING finger genes required for embryogenesis in C. elegans
Authors: Moore Rhonda , Boyd Lynn 
Published: January 2004

AbstractThe RING finger motif exists in E3 ligases of the ubiquitination pathway. These ubiquitin ligases bind to target proteins, leading to their modification by covalent addition of ubiquitin peptides. Current databases contain hundreds of proteins with RING finger motifs. This study investigates the role of RING finger genes in embryogenesis of the nematode, Caenorhabditis elegans. We expand the previous list of RING finger‐containing genes and show that there are 103 RING finger‐containing genes in the C. elegans genome. DNA microarrays of these 103 genes were probed with various RNA samples to identify 16 RING finger genes whose expression is enriched in the germline. RNA interference (RNAi) analysis was then used to determine the developmental role of these genes. One RING finger gene, C32D5.10, showed a dramatic larval arrest upon RNAi. Three RING finger genes exhibited embryonic lethality after RNAi. These three genes include par‐2, and two small RING finger proteins: F35G12.9 (an ortholog of APC11) and ZK287.5 (an ortholog of rbx1). Embryos from RNAi of the APC11 and rbx1 orthologs were arrested in the cell cycle, confirming the role of these particular RING finger proteins in regulation of the cell cycle. genesis 38:1–12, 2004. © 2003 Wiley‐Liss, Inc.
Zebrafish intestinal fatty acid binding protein (I‐FABP) gene promoter drives gut‐specific expression in stable transgenic fish
Authors: Her Guor Mour , Chiang Chia‐Chang , Wu Jen‐Leih 
Published: January 2004

AbstractMammalian intestinal fatty acid‐binding protein (I‐FABP) is a small cytosolic protein and is thought to play a crucial role of intracellular fatty acid trafficking and metabolism in gut. To establish an in vivo system for investigating its tissue‐specific regulation during zebrafish intestinal development, we isolated 5′‐flanking sequences of the zebrafish L‐FABP gene and used a transgenic strategy to generate gut‐specific transgenic zebrafish with green/red fluorescent intestine. The 4.5‐kb 5′‐flanking sequence of zebrafish I‐FABP gene was sufficient to direct fluorescent expression in intestinal tube, first observed in 3 dpf embryos and then continuously to the adult stage. This pattern of transgenic expression is consistent with the expression pattern of the endogenous gene. In all five transgenic lines 45–52% of the F2 inheritance rates were consistent with the ratio of Mendelian segregation. These fish can also provide a valuable resource of labeled adult intestinal cells for in vivo or in vitro studies. Finally, it is possible to establish an in vivo system using these fish for screening genes required for gut development. genesis 38:26–31, 2004. © 2003 Wiley‐Liss, Inc.
General method for the modification of different BAC types and the rapid generation of BAC transgenic mice
Authors: Sparwasser Tim , Gong Shiaoching , Li James Y.H. , Eberl Gerard 
Published: January 2004

AbstractMost genome projects have relied on the sequencing of bacterial artificial chromosomes (BACs), which encompass 100–300 kb of genomic DNA. As a consequence, several thousand BAC clones are now mapped to the human and mouse genome. It is therefore possible to identify in silico a BAC clone that carries a particular gene and obtain it commercially. Given the large size of BACs, most if not all regulatory sequences of a gene are present and can be used to direct faithful and tissue‐specific expression of heterologous genes in vitro in cell cultures and in vivo in BAC‐transgenic mice. We describe here an optimized and comprehensive protocol to select, modify, and purify BACs in order to generate BAC‐transgenic mice. Importantly, this protocol includes a method to generate, within 2 days, complex plasmid cassettes required to modify BACs, and to efficiently modify different types of BACs selected from the two major BAC libraries available. Altogether, using a combination of genomic database analysis, overlap PCR cloning, and BAC recombination in bacteria, our approach allows for the rapid and reliable generation of “pseudo knockin” mice. genesis 38:39–50, 2004. © 2003 Wiley‐Liss, Inc.
Histone deacetylase activity is required for embryonic stem cell differentiation
Authors: Lee Jeong‐Heon , Hart Suzanne R.L. , Skalnik David G. 
Published: January 2004

AbstractMammalian development requires commitment of cells to restricted lineages, which requires epigenetic regulation of chromatin structure. Epigenetic modifications were examined during in vitro differentiation of murine embryonic stem (ES) cells. Global histone acetylation, a euchromatin marker, declines dramatically within 1 day of differentiation induction and partially rebounds by day 2. Histone H3‐Lys9 methylation, a heterochromatin marker, increases during in vitro differentiation. Conversely, the euchromatin marker H3‐Lys4 methylation transiently decreases, then increases to undifferentiated levels by day 4, and decreases by day 6. Global cytosine methylation, another heterochromatin marker, increases slightly during ES cell differentiation. Chromatin structure of the Oct4 and Brachyury gene promoters is modulated in concert with their pattern of expression during ES cell differentiation. Importantly, prevention of global histone deacetylation by treatment with trichostatin A prevents ES cell differentiation. Hence, ES cells undergo functionally important global and gene‐specific remodeling of chromatin structure during in vitro differentiation. genesis 38:32–38, 2004. © 2003 Wiley‐Liss, Inc.
Androgen receptor: A key molecule in the progression of prostate cancer to hormone independence
Authors: Taplin Mary‐Ellen , Balk Steven P. 
Published: January 2004

AbstractDespite earlier detection and recent advances in surgery and radiation, prostate cancer is second only to lung cancer in male cancer deaths in the United States. Hormone therapy in the form of medical or surgical castration remains the mainstay of systemic treatment in prostate cancer. Over the last 15 years with the clinical use of prostate specific antigen (PSA), there has been a shift to using hormone therapy earlier in the disease course and for longer duration. Despite initial favorable response to hormone therapy, over a period of time these tumors will develop androgen‐independence that results in death. The androgen receptor (AR) is central to the initiation and growth of prostate cancer and to its response to hormone therapy. Analyses have shown that AR continues to be expressed in androgen‐independent tumors and AR signaling remains intact as demonstrated by the expression of the AR regulated gene, PSA. Androgen‐independent prostate cancers have demonstrated a variety of AR alterations that are either not found in hormone naïve tumors or found at lower frequency. These changes include AR amplification, AR point mutation, and changes in expression of AR co‐regulatory proteins. These AR changes result in a “super AR” that can respond to lower concentrations of androgens or to a wider variety of agonistic ligands. There is also mounting evidence that AR can be activated in a ligand independent fashion by compounds such as growth factors or cytokines working independently or in combination. These growth factors working through receptor tyrosine kinase pathways may promote AR activation and growth in low androgen environments. The clinical significance of these AR alterations in the development and progression of androgen‐independent prostate cancer remains to be determined. Understanding the changes in AR signaling in the evolution of androgen‐independent prostate cancer will be key to the development of more effective hormone therapy. © 2003 Wiley‐Liss, Inc.