A ratiometric probe for the selective time-gated luminescence detection of potassium in water

A europium probe for the ratiometric detection of potassium in water is presented. This probe demonstrates high sensitivity, with an affinity for K(+) in the mM range, and high selectivity for K(+) over Na(+), Ca(2+), Mg(2+) and Li(+). The long luminescence lifetime of the probe and its large Stokes shift further enable accurate determination of the concentration of K(+) in complex aqueous media.     

微孔板蛋白芯片可视化检测方法的研究

将微孔板生物芯片制备技术与银增强显色方法相结合,建立了一种高通量蛋白免疫分析新方法。研究采用夹心法反应原理,将人IgG捕获抗体以微阵列形式点样于96孔板底部制备成蛋白微阵列,并依次与人IgG、生物素标记二抗及链亲和素胶体金反应,最后用银增强法显色。采用平板式扫描仪对微孔板显色结果进行快速扫描成像,图像采用luxscan 3.0软件处理。结果表明:微孔板蛋白芯片的最低检测量可达0.6 ng/mL,线性范围10 ng/mL~100μg/mL,相关系数为0.98,重复性较好(CV10%)。     

Cationic conjugated polyelectrolytes-triggered conformational change of molecular beacon aptamer for highly sensitive and selective potassium ion detection

We demonstrate highly sensitive and selective potassium ion detection against excess sodium ions in water, by modulating the interaction between the G-quadruplex-forming molecular beacon aptamer (MBA) and cationic conjugated polyelectrolyte (CPE). The K(+)-specific aptamer sequence in MBA is used as the molecular recognition element, and the high binding specificity of MBA for potassium ions offers selectivity against a range of metal ions. The hairpin-type MBA labeled with a fluorophore and quencher at both termini undergoes a conformational change (by complexation with CPEs) to either an open-chain form or a G-quadruplex in the absence or presence of K(+) ions. Conformational changes of MBA as well as fluorescence (of the fluorophore in MBA) quenching or amplification via fluorescence resonance energy transfer from CPEs provide clear signal turn-off and -on in the presence or absence of K(+). The detection limit of the K(+) assays is determined to be ~1.5 nM in the presence of 100 mM Na(+) ions, which is ~3 orders of magnitude lower than those reported previously. The successful detection of 5'-adenosine triphosphate (ATP) with the MBA containing an ATP-specific aptamer sequence is also demonstrated using the same sensor scheme. The scheme reported herein is applicable to the detection of other kinds of G-rich aptamer-binding chemicals and biomolecules.     

Construction of multiporphyrin arrays via selective cross-metathesis

Selective cross-metathesis of type I and type II meso-functionalized porphyrin olefins afforded alkenyl-coupled dimeric and trimeric porphyrin systems in good yield with excellent E/Z selectivity. The synthetic utility of the method is demonstrated through the preparation of mixed metalated (M = 2H, Zn) porphyrin dimer and trimer. [reaction: see text]     

Modified interdigitated arrays by novel poly(1,8-diaminonaphthalene)/carbon nanotubes composite for selective detection of mercury(II)

This study describes a novel type of interdigitated arrays (IDA), microfabricated by electropolymerizing structured Poly(1,8-diaminonaphthalene)/functionalized multi-walled carbon nanotubes (PDAN/CNT) thin film onto a silicon chip for square wave voltammetry (SWV) multi-element heavy metal ion detection. The structure of PDAN/CNT was characterized by Raman, FE-SEM and AFM techniques. Analysed experiments reveal that the uptake of Hg²⁺ by PDAN/CNT is quite specific and it can be used advantageously for electrochemical sensing of Hg²⁺ thanks to original feature of (Hg²⁺/Hg₂²⁺) redox potential with the respect to that of PDAN/CNT. As-developed IDA type electrode can extend its utility in other sensing applications.     

New sensitive fluorophores for selective DNA detection

4,7-Disubstituted benzothiadiazoles containing 1-arylethynyl and 4-methoxyphenyl groups are selective photoluminescent "light up" probes to duplex DNA with unprecedented sensibility in both spectrophotometric and spectrofluorimetric measurements.     

A highly selective bifunctional luminescence probe for potassium and fluoride ions

A novel bifunctional molecule 1 by a combination of 1,3-alternate calix[4]-crown-5 and triarylborane moieties through alkynyl linkers has been designed and synthesized. Compound 1 shows intense fluorescence with a photoluminescence quantum yield of 0.70 in CH(2)Cl(2) solution and can serve as a bifunctional luminescent probe for potassium and fluoride ions with high sensitivity and selectivity.     

Dendron arrays for the force-based detection of DNA hybridization events

Single-molecule force measurement methods have attracted increasing interest over recent years for the development of novel approaches for biomolecular screening. However, many of these developments are currently hindered by the available biomolecule surface attachment methods, in that it is still not trivial to create surfaces and devices with highly defined surface functionality and/or uniformity. Here we offer a new approach to address such issues based on the formation of dendron arrays. Through the measurement of forces between dendron surfaces functionalized with complementary DNA oligonucleotides, we observed several unique properties of the surfaces modified via this approach. The capability to record attractive or "jump-in" forces associated with molecular binding events is one of them. Additionally, these events occur in greater than 80% of measurements, and the forces are dependent on the number of complementary DNA bases of the associating strands while being insensitive to the measurement rate. Combined with a narrow distribution of both attractive forces and unbinding forces we suggest such functionalized surfaces offer a significant advance for fast and accurate force-based studies of oligonucleotide hybridization.     

Carbon-on-metal films for surface plasmon resonance detection of DNA arrays

Surface plasmon resonance (SPR) imaging affords label-free monitoring of biomolecule interactions in an array format. A surface plasmon conducting metal thin film is required for SPR measurements. Gold thin films are traditionally used in SPR experiments as they are readily functionalized with thiol-containing molecules through formation of a gold-sulfur bond. The lability of this gold-thiol linkage upon exposure to oxidizing conditions and ultraviolet light renders these surfaces incompatible with light-directed synthetic methods for fabricating DNA arrays. It is shown here that applying a thin carbon overlayer to the gold surface yields a chemically robust substrate that permits light-directed synthesis and also supports surface plasmons. DNA arrays fabricated on these carbon-metal substrates are used to analyze two classes of biomolecular interactions: DNA-DNA and DNA-protein. This new strategy allows the combinatorial study of binding interactions directly from native, unmodified biomolecules of interest and offers the possibility of discovering new ligands in complex mixtures such as cell lysates.     

Microcalorimeter arrays for ultra-high energy resolution X- and gamma-ray detection

Microcalorimeter detectors provide superior energy resolution for the detection of X-rays and gamma-rays. The technology utilizes a cryogenic transition-edge sensor (TES) coupled to a tin bulk absorber. We are working on fabrication methods for the production of arrays with many sensors. In this paper, we present data collected with an array of microcalorimeters using as many as 26 sensor elements simultaneously. Advances in sensor design have extended the useful dynamic range to photon energies up to ～200 keV, while providing resolution performance in the 80–90 eV FWHM range, significantly better than planar high-purity germanium. These sensor arrays have applications in the measurement of nuclear materials. We present data collected from ¹⁵³Gd, a highly-enriched uranium sample, and a plutonium isotopic standard source. We also demonstrate clean separation of the ²³⁵U 185.715 keV peak from the ubiquitous ²²⁶Ra 186.211 keV background peak interference.     

Silica-modified electrode for the selective detection of mercury

Pure silica particles were dispersed within carbon paste and the resulting modified electrode was applied to the selective voltammetric detection of mercury(II) species after their accumulation at open circuit. The remarkable selectivity observed between pH 4 and 7 was attributed to the intrinsic adsorption mechanism which involves a condensation reaction between mercury(II) hydroxide and hydroxyl groups on the silica surface, leading to the formation of an inner-sphere-type surface complex. After optimization with respect to the electrode composition, the detection medium, and the voltammetric scan mode, a linear response was obtained in the concentration range between 2 × 10⁻⁷ M to 1 × 10⁻⁵ M, by applying anodic stripping square wave voltammetry. Various silica samples were used and their sorption behavior was discussed in relation to their specific surface area and porosity. The effect of chloride and pH on the accumulation of mercury(II) on silica was also investigated. Received: 4 September 1999 / Accepted: 5 January 2000     

Label-free aptamer biosensor for selective detection of thrombin

We fabricated a novel fluorescence biosensor for the selective detection of thrombin by using bovine serum albumin-capped CdS quantum dots (BSA-CdS QDs). Two kinds of designed DNA (DNA1 and DNA2) could bind to CdS QDs through the electrostatic interaction between DNA and Cd²⁺ on the surface of CdS QDs. The obtained DNA/BSA-CdS QDs kept stable in the solution with the fluorescence intensity obviously enhanced. Hairpin structure of DNA1contained two domains, one is the aptamer sequence of thrombin and the other is the complementary sequence of DNA2. When thrombin was added, it would bind to DNA1 and induce the hairpin structure of DNA1 changed into G-quadplex structure. Meanwhile, DNA2 would transfer from the surface of CdS QDs to DNA1 via hybridization, which resulted in the removal of DNA1 and DNA2 from the surface of CdS QDs, and led to the fluorescence intensity of CdS QDs reduced. Thus, the determination of thrombin could be achieved by monitoring the change of the fluorescence intensity of CdS QDs. The present method is simple and fast, and exhibits good selectivity for thrombin over other proteins. We have successfully detected thrombin in human serum samples with satisfactory results.     

The detection of potassium sulfate in excess of potassium pyrosulfate

X-Ray diffraction, infrared, and raman spectroscopic methods were investigated for the detection of K₂SO₄ in excess of K₂S₂O₇ in solid solutions.The X-ray diffraction lines of K₂SO₄ were found to be overlapped by the diffraction pattern of K₂S₂O₇ and infrared studies indicated that K₂SO₄ absorption bands corresponded to regions of strong absorption in K₂S₂O₇. The detection of sulfate could not be carried out by the X-ray diffraction and infrared methods. However, the raman method indicated that a strong and narrow K₂SO₄ band at 981 cm^?1 could unambiguously be used for the detection of sulfate in solid solutions of K₂SO₄ in K₂S₂O₇, as pyrosulfate showed no absorption around this band.     

A potassium selective 'nanosponge' with well defined pores

The novel spherical cluster-compound K2Na6[K20 [symbol: see text] Mo80-V22O282(SO4)12(H2O)66]. approximately 140H2O 1 has been obtained in a 'one-pot' reaction and exhibits several remarkable structural features: 30 open shell centers, i.e. 8 Mov and 22 VIV spanning an icosidodecahedron, the incorporation of 20 K+ cations capping 20 appropriate [M6O6] pores/rings present at the surface of the spherical cluster-anion, and an encapsulated aggregate of water molecules.     

Porous three-dimensional nanorod arrays through selective chemical etching of nanocomposites

Three-dimensional Cu-Si and Cu-SiO(2) nanorod arrays containing ~68 at% Cu have been fabricated by a glancing angle co-deposition technique. By selectively etching Cu in 0.05 M KCN methanol solution, porous nanorods with different shapes form, which are promising for applications in sensors, catalysts, and as medical capsules that are able to be loaded with functional materials.     

A selective metabolite array for the detection of phosphometabolites

Immobilised metal ion affinity (IMA) has been traditionally used specifically for the separation of phosphorylated proteins and nucleic acids, in proteomics and genomics, respectively. This report describes the novel application of IMA in metabolomics for the development of metabolite arrays to detect phosphometabolites using a plasma polymer-modified surface. Immobilisation of gallium, zirconium, cobalt, copper, zinc, nickel, iron, and chromium to acrylic acid plasma polymer followed by subsequent exposure to metabolites (phospho- and non-phosphometabolites) was investigated. Results analysed using ToF-SIMS suggests that gallium and zirconium exhibit higher phosphometabolite affinity and specificity compared to other metals, and can be used to develop metabolite arrays for the detection of phosphometabolites.     

Fluorescent peptide sensor for the selective detection of Cu

A new fluorescent peptidyl chemosensor for Cu²⁺ ions with fluorescence resonance energy transfer (FRET) capabilities has been synthesized via Fmoc solid-phase peptide synthesis. The metal chelating unit, which is flanked by the fluorophores tryptophan (donor) and dansyl chloride (acceptor), consists of the amino acids glycine and aspartic acid (Gly-Gly-Asp-Gly-Gly-Asp-Gly-Gly-Asp-Gly-Gly-Asp-Gly-Gly). Coordination of the Cu²⁺ ions to the metal chelating unit results in fluorescent quenching of both the donor and acceptor fluorophores. Although it was determined that Cu²⁺ binding causes no change in FRET efficiency, emission and Cu²⁺-induced quenching of the acceptor dye can be used to monitor the concentration of the copper ions, with a detection limit of 32 μg L⁻¹. The sensor also demonstrated sensitivity, reversibility and selectivity towards Cu²⁺ in a transition metal matrix at pH 7.0.