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1

Polymeric assay film for direct colorimetric detection  

SciTech Connect

This invention relates to a lipid bilayer with affinity to an analyte, which directly signals binding by a changes in the light absorption spectra. This novel assay has special applications in the drug development and medical testing fields. Using a spectrometer, the system is easily automated, and a multiple well embodiment allows inexpensive screening and sequential testing. This invention also has applications in industry for feedstock and effluent monitoring.

Charych, D.; Nagy, J.; Spevak, W.

1999-12-14

2

Polymeric assay film for direct colorimetric detection  

DOEpatents

A lipid bilayer with affinity to an analyte, which directly signals binding by a changes in the light absorption spectra. This novel assay means and method has special applications in the drug development and medical testing fields. Using a spectrometer, the system is easily automated, and a multiple well embodiment allows inexpensive screening and sequential testing. This invention also has applications in industry for feedstock and effluent monitoring.

Charych, Deborah (Albany, CA); Nagy, Jon (Bozeman, MT); Spevak, Wayne (Albany, CA)

2002-01-01

3

Polymeric assay film for direct colorimetric detection  

DOEpatents

A lipid bilayer with affinity to an analyte, which directly signals binding by a changes in the light absorption spectra. This novel assay means and method has special applications in the drug development and medical testing fields. Using a spectrometer, the system is easily automated, and a multiple well embodiment allows inexpensive screening and sequential testing. This invention also has applications in industry for feedstock and effluent monitoring.

Charych, Deborah (Albany, CA); Nagy, Jon (Rodeo, CA); Spevak, Wayne (Albany, CA)

1999-01-01

4

Sol-gel matrices for direct colorimetric detection of analytes  

DOEpatents

The present invention relates to methods and compositions for the direct detection of analytes using color changes that occur in immobilized biopolymeric material in response to selective binding of analytes to their surface. In particular, the present invention provides methods and compositions related to the encapsulation of biopolymeric material into metal oxide glass using the sol-gel method.

Charych, Deborah H. (Albany, CA); Sasaki, Darryl (Albuquerque, NM); Yamanaka, Stacey (Dallas, TX)

2000-01-01

5

Sol-Gel Matrices For Direct Colorimetric Detection Of Analytes  

DOEpatents

The present invention relates to methods and compositions for the direct detection of analytes using color changes that occur in immobilized biopolymeric material in response to selective binding of analytes to their surface. In particular, the present invention provides methods and compositions related to the encapsulation of biopolymeric material into metal oxide glass using the sol-gel method.

Charych, Deborah H. (Albany, CA); Sasaki, Darryl (Albuquerque, NM); Yamanaka, Stacey (Dallas, TX)

2002-11-26

6

Direct colorimetric detection of a receptor-ligand interaction by a polymerized bilayer assembly  

SciTech Connect

Detection of receptor-ligand interactions is generally accomplished by indirect assays such as enzyme-linked immunosorbent assay. A direct colorimetric detection method based on a polydiacetylene bilayer assembled on glass microscope slides has been developed. The bilayer is composed of a self-assembled monolayer of octadecylsilane and a Langmuir-Blodgett monolayer of polydiacetylene. The polydiacetylene layer is functionalized with an analog of sialic acid, the receptor-specific ligand for the influenza virus hemagglutinin. The sialic acid ligand serves as a molecular recognition element and the conjugated polymer backbone signals binding at the surface by a chromatic transition. The color transition is readily visible to the naked eye as a blue to red color change and can be quantified by visible absorption spectroscopy. Direct colorimetric detection by polydiacetylene films offers new possibilities for diagnostic applications and screening for new drug candidates or binding ligands.

Charych, D.H.; Nagy, J.O.; Bednarski, M.D. (Lawrence Berkeley Laboratory, CA (United States)); Spevak, W. (Univ. of California, Berkeley (United States))

1993-07-30

7

Gum kondagogu reduced/stabilized silver nanoparticles as direct colorimetric sensor for the sensitive detection of Hg²? in aqueous system.  

PubMed

A highly sensitive and selective method is reported for the colorimetric detection of Hg(2+) in aqueous system by using label free silver nanoparticles (Ag NPs). Ag NPs used in this method were synthesized by gum kondagogu (GK) which acted as both reducing and stabilizing agent. The average size of the GK-Ag NPs was found to be 5.0 ± 2.8 nm as revealed by transmission electron microscope (TEM) analysis and the nanoparticles were stable at various pH conditions (pH 4-11) and salt concentrations (5-100 mM). The GK reduced/stabilized Ag NPs (GK-Ag NPs) were directly used for the selective colorimetric reaction with Hg(2+) without any further modification. The bright yellow colour of Ag NPs was found to fade in a concentration dependent manner with the added Hg(+) ions. The fading response was directly correlated with increasing concentration of Hg(2+). More importantly, this response was found to be highly selective for Hg(2+) as the absorption spectra were found to be unaffected by the presence of other ions like; Na(+), K(+), Mg(2+), Ca(2+), Cu(2+), Ni(2+), Co(2+), As(3+), Fe(2+), Cd(2+), etc. The metal sensing mechanism is explained based on the turbidometric and X-ray diffraction (XRD) analysis of GK-Ag NPs with Hg(2+). The proposed method was successfully applied for the determination of Hg(2+) in various ground water samples. The reported method can be effectively used for the quantification of total Hg(2+) in samples, wherein the organic mercury is first oxidized to inorganic form by ultraviolet (UV) irradiation. The limit of quantification for Hg(2+) using the proposed method was as low as 4.9 × 10(-8) mol L(-1) (50 nM). The proposed method has potential application for on-field qualitative detection of Hg(2+) in aqueous environmental samples. PMID:24274277

Rastogi, Lori; Sashidhar, R B; Karunasagar, D; Arunachalam, J

2014-01-01

8

Colorimetric Immunoassay for Detection of Tumor Markers  

PubMed Central

Tumor markers are substances, usually proteins, produced by the body in response to cancer growth, or by the cancer tissue itself. They can be detected in blood, urine, or tissue samples, and the discovery and detection of tumor markers may provide earlier diagnosis of cancer and improved therapeutic intervention. Colorimetric immunoassays for tumor marker detection have attracted considerable attention, due to their simplicity and high efficiency. The traditionally used colorimetric immunoassays for the detection of tumor markers are based on enzyme-linked immunosorbent assays, and the great achievement of nanotechnology has further opened opportunities for the development of such kind of immunoassays. This paper will summarize recent advances in the field of colorimetric immunoassays for detecting tumor markers, which is aimed to provide an overview in this field, as well as experimental guidance for the learner. PMID:21614193

Yin, Yongmei; Cao, Ya; Xu, Yuanyuan; Li, Genxi

2010-01-01

9

Emergency First Responders' Experience with Colorimetric Detection Methods  

SciTech Connect

Nationwide, first responders from state and federal support teams respond to hazardous materials incidents, industrial chemical spills, and potential weapons of mass destruction (WMD) attacks. Although first responders have sophisticated chemical, biological, radiological, and explosive detectors available for assessment of the incident scene, simple colorimetric detectors have a role in response actions. The large number of colorimetric chemical detection methods available on the market can make the selection of the proper methods difficult. Although each detector has unique aspects to provide qualitative or quantitative data about the unknown chemicals present, not all detectors provide consistent, accurate, and reliable results. Included here, in a consumer-report-style format, we provide “boots on the ground” information directly from first responders about how well colorimetric chemical detection methods meet their needs in the field and how they procure these methods.

Sandra L. Fox; Keith A. Daum; Carla J. Miller; Marnie M. Cortez

2007-10-01

10

Colorimetric Detection and Identification of Natural and Artificial Sweeteners  

E-print Network

Colorimetric Detection and Identification of Natural and Artificial Sweeteners Christopher J. Musto-Champaign, 600 S. Mathews Avenue, Urbana, Illinois 61801 A disposable, low-cost colorimetric sensor array has optoelectronic approach using simple colorimetric sensor arrays for the detection and identification of a wide

Suslick, Kenneth S.

11

A Colorimetric Sensor Array for Detection and Identification of Sugars  

E-print Network

A Colorimetric Sensor Array for Detection and Identification of Sugars Sung H. Lim, Christopher J challenges. We report here a low-cost, simple colorimetric sensor array capable of identification a colorimetric sensor array of chemically responsive dyes for identification and quantification of a wide range

Suslick, Kenneth S.

12

Colorimetric engineered immunoprobe for the detection and quantification of microcystins.  

PubMed

Microcystins (MCs) are heptapeptide toxins produced by cyanobacteria. Their global occurrence in aquatic ecosystems has prompted the development of several detection methods, including antibody-based methods. Here, we propose to apply recombinant antibody technologies to the production of a bivalent colorimetric immunoprobe (scFv-AP) made of the so-called scFv fused to the alkaline phosphatase (AP) of Escherichia coli. Recombinant antibody technologies allow the development of specific probes with improved properties and suitable for the detection of MCs. The fusion protein was produced in the periplasm of recombinant bacteria and was used to develop a direct competitive enzyme immunoassay for specific detection of MCs without requiring further purification. The epitope recognized by the recombinant molecule was circumscribed to a motif common to all MCs. Such a genetic approach offers many advantages over chemical cross-linking of antibodies to colorimetric enzymes and may be adaptable to the analysis of water samples and in situ detection. PMID:24607607

Alvarenga, Larissa M; Muzard, Julien; Ledreux, Aurélie; Bernard, Cécile; Billiald, Philippe

2014-04-01

13

A Simple and Highly Sensitive Colorimetric Detection Method for Gaseous Formaldehyde  

E-print Network

A Simple and Highly Sensitive Colorimetric Detection Method for Gaseous Formaldehyde Liang Feng inexpensive colorimetric methods, which see some field use.5 A number of colorimetric or fluorometric methods colorimetric method for fast formaldehyde detection. Most colorimetric formaldehyde detection methods are based

Suslick, Kenneth S.

14

Colorimetric Method for Beryllium Surface Contamination Detection  

SciTech Connect

To address the need for real-time accurate total beryllium analyses, Savannah River Technology Center Analytical Development Section personnel evaluated and modified a colorimetric screening method developed at Los Alamos National Lab to measure beryllium on surfaces. This method was based on a color complex formed by beryllium and chromium azurol s . SRTC converted this visual method to a quantitative analysis method using spectrophotometric detection. The addition of a cationic surfactant (hexadecyltrimethylammonium bromide, CTAB) to the Be-CAS system shifted the complex absorbance away from the CAS absorbance and allowed for the detection. Assuming complete dissolution and a 10 mL rinse solution volume to remove the beryllium from the wipe, the detection limit was calculated comfortably below the free release limit. The spectrophotometric method was rugged and simple enough that it could be used as a field method.

MCWHORTER, CHRISTOPHER

2004-03-11

15

Colorimetric resonant reflection as a direct biochemical assay technique  

Microsoft Academic Search

A novel approach for the detection of molecular interactions is presented in which a colorimetric resonant diffractive grating surface is used as a surface binding platform. A guided mode resonant phenomenon is used to produce an optical structure that, when illuminated with white light, is designed to reflect only a single wavelength. When molecules are attached to the surface, the

Brian Cunningham; Peter Li; Bo Lin; Jane Pepper

2002-01-01

16

Optical fiber waveguide sensor for the colorimetric detection of ammonia  

NASA Astrophysics Data System (ADS)

We present the development and characterization of a fiber-optic colorimetric gas sensor combined with the electronic circuitry for measurement control and RFID communication. The gas sensor detects ammonia using a 300 ?m polyolefin fiber coated with a gas-sensitive polymer film. The spectral and time-dependent sensitivity of various polymer films was tested in transmission measurements. Light from a standard LED at ? = 590 nm was coupled into the polyolefin fiber through the front face. A prototype of the gas sensor with the direct coupling method was tested under realistic measurement conditions, i.e. battery-driven and in a completely autonomous mode. The sensor system showed good sensitivity to the ammonia concentrations and response times in the order of minutes. The achievable power consumption was below 100?W.The films contained the pH-sensitive dyes bromocresol purple or bromophenol blue embedded in either ethyl cellulose or polyvinyl butyral, and optionally tributyl phosphate as plasticizer. The bromophenol blue based films showed a strong reaction to ammonia, with saturation concentrations around 1000 ppm and response times of about 15 seconds to 100ppm. The colorimetric reaction was simulated using a simple kinetic model which was in good agreement with the experimental results.

Schmitt, Katrin; Rist, Jonas; Peter, Carolin; Wöllenstein, Jürgen

2011-06-01

17

Highly sensitive colorimetric detection of organophosphate pesticides using copper catalyzed click chemistry.  

PubMed

Highly sensitive colorimetric detection of organophosphate pesticides (OPs) was developed using Cu (I)-catalyzed click chemistry as the colorimetric signal amplification process between the acetylcholine esterase-acetylthiocholine system (AChE-ATCl) and azide- terminal alkyne-functionalized Au NPs as the colorimetric probe. It was demonstrated that the involvement of Cu (I)-catalyzed click chemistry allowed greatly improved colorimetric sensitivity for OPs detection based on the indirect modulation of click chemistry-induced Au NPs aggregation by the AChE-ATCl system. Paraoxon as the model OPs in the concentration range from 10(-6) to 10(-4)g/L can be directly detected using the naked-eye-based colorimetric assay without the aid of any complex instruments. The results for paraoxon detection in spiked apple juice were found to be in good agreement with that obtained by the conventional UV-vis spectroscopy. This simple and reliable assay would greatly improve the public safety and environmental protection in an on-site and real-time detection format. PMID:23200365

Fu, Guanglei; Chen, Wenwen; Yue, Xiuli; Jiang, Xingyu

2013-01-15

18

Colorimetric Aptasensor Using Unmodified Gold Nanoparticles for Homogeneous Multiplex Detection  

PubMed Central

Colorimetric aptasensors using unmodified gold nanoparticles (AuNPs) have attracted much attention because of their low cost, simplicity, and practicality, and they have been developed for various targets in the past several years. However, previous research has focused on developing single-target assays. Here, we report the development of a homogeneous multiplex aptasensor by using more than one class of aptamers to stabilize AuNPs. Using sulfadimethoxine (SDM), kanamycin (KAN) and adenosine (ADE) as example targets, a KAN aptamer (750 nM), an SDM aptamer (250 nM) and an ADE aptamer (500 nM) were mixed at a 1?1?1 volume ratio and adsorbed directly onto the surface of unmodified AuNPs by electrostatic interaction. Upon the addition of any of the three targets, the conformation of the corresponding aptamer changed from a random coil structure to a rigid folded structure, which could not adsorb and stabilize AuNPs. The AuNPs aggregated in a specific reaction buffer (20 mM Tris-HCl containing 20 mM NaCl and 5 mM KCl), which led to a color change from red to purple/blue. These results demonstrate that the multiplex colorimetric aptasensor detected three targets simultaneously while maintaining the same sensitivity as a single-target aptasensor for each individual target. The multiplex aptasensor could be extended to other aptamers for various molecular detection events. Due to its simple design, easy operation, fast response, cost effectiveness and lack of need for sophisticated instrumentation, the proposed strategy provides a powerful tool to examine large numbers of samples to screen for a small number of potentially positive samples containing more than one analyte, which can be further validated using sophisticated instruments. PMID:25279730

Niu, Shucao; Lv, Zhenzhen; Liu, Jinchuan; Bai, Wenhui; Yang, Shuming; Chen, Ailiang

2014-01-01

19

A Colorimetric Sensor Array for Detection of Triacetone Triperoxide Vapor Hengwei Lin and Kenneth S. Suslick*  

E-print Network

A Colorimetric Sensor Array for Detection of Triacetone Triperoxide Vapor Hengwei Lin and Kenneth S a simple and highly sensitive colorimetric sensor for the detection of TATP vapor with semiquantitative that a colorimetric sensor array of redox sensitive dyes can detect even very low levels of TATP vapor from its acid

Suslick, Kenneth S.

20

An Allosteric Dual-DNAzyme Unimolecular Probe for Colorimetric Detection of Copper(II)  

E-print Network

An Allosteric Dual-DNAzyme Unimolecular Probe for Colorimetric Detection of Copper(II) Bin by a cleavage process, thus generating colorimetric or chemiluminescence readout signals. The Willner group has-histidine-dependent DNAzymes, yielding HRP-mimicking nucleic acids that enable the colorimetric detection of Pb2+ and L

Tan, Weihong

21

Development of the colorimetric sensor array for detection of explosives and volatile organic compounds in air  

E-print Network

Development of the colorimetric sensor array for detection of explosives and volatile organic of Denmark (DTU) we are developing a simple colorimetric sensor array which can be useful in detection potentially be produced as single use disposable. Keywords: colorimetric sensor array, DNT, chemo

22

Detection and analysis of membrane interactions by a biomimetic colorimetric lipid/polydiacetylene assay  

E-print Network

of a colorimetric assay based on supramolecular assemblies of lipid­polydiacetylene vesicles for analysis biochemical processes. Specifically, we show that the colorimetric assay can be tuned for selective detection colorimetric assay based on lipid­polydiacetylene (PDA)1 vesicles. Sonicated and UV-polymerized as- semblies

Jelinek, Raz

23

Colorimetric detection of uranium in water  

DOEpatents

Disclosed are methods, materials and systems that can be used to determine qualitatively or quantitatively the level of uranium contamination in water samples. Beneficially, disclosed systems are relatively simple and cost-effective. For example, disclosed systems can be utilized by consumers having little or no training in chemical analysis techniques. Methods generally include a concentration step and a complexation step. Uranium concentration can be carried out according to an extraction chromatographic process and complexation can chemically bind uranium with a detectable substance such that the formed substance is visually detectable. Methods can detect uranium contamination down to levels even below the MCL as established by the EPA.

DeVol, Timothy A. (Clemson, SC); Hixon, Amy E. (Piedmont, SC); DiPrete, David P. (Evans, GA)

2012-03-13

24

Colorimetric Detection of Senescence-Associated ? Galactosidase  

PubMed Central

Most normal human cells have a finite replicative capacity and eventually undergo cellular senescence, whereby cells cease to proliferate. Cellular senescence is also induced by various stress signals, such as those generated by oncogenes, DNA damage, hyperproliferation, and an oxidative environment. Cellular senescence is well established as an intrinsic tumor suppressive mechanism. Recent progress concerning senescence research has revealed that cellular senescence occurs in vivo and that, unexpectedly, it has a very complex role in tissue repair, promoting tumor progression and aging via the secretion of various cytokines, growth factors, and enzymes. Therefore, the importance of biomarkers for cellular senescence has greatly increased. In 1995, we described the “senescence-associated ? galactosidase” (SA-?gal) biomarker, which conveniently identifies individual senescent cells in vitro and in vivo. Here, we describe an updated protocol for the detection of cell senescence based on this widely used biomarker, which contributed to recent advances in senescence, aging and cancer research. We provide an example of detecting SA-?gal together with other senescence markers and a proliferation marker, EdU, in single cells. PMID:23296655

Itahana, Koji; Itahana, Yoko; Dimri, Goberdhan P.

2013-01-01

25

Colorimetric detection of metallothioneins using a thymine-rich oligonucleotide-Hg complex and gold nanoparticles.  

PubMed

A simple and sensitive method for label-free, colorimetric detection of metallothioneins (MTs) has been developed by using a thymine (T)-rich oligonucleotide (TRO)-Hg-AuNP system. In this colorimetric strategy, the thiol groups of MTs could interact with mercury from the T-Hg(2+)-T complex to release TRO, resulting in a color change of the system. The response signals linearly correlated with the concentration of MTs over the range of 2.56 × 10(-8) to 3.08 × 10(-7) mol L(-1), and the limit of detection was 7.67 × 10(-9) mol L(-1). The relative standard deviation and the recovery were 2.3-4.8% (n = 11) and 94.2-103.9%, respectively. The proposed method avoids the label and derivatization steps in common methods, allows direct analysis of the samples by the naked eye without costly instruments, and is reliable, inexpensive, and sensitive. PMID:23357234

Qian, Qiu-Mei; Wang, Yong-Sheng; Yang, Hui-Xian; Xue, Jin-Hua; Liu, Lu; Zhou, Bin; Wang, Jia-Cheng; Yin, Ji-Cheng; Wang, Yong-Song

2013-05-01

26

Colorimetric Detection and Identification of Natural and Artificial Sweeteners  

Microsoft Academic Search

A disposable, low-cost colorimetric sensor array has been created by\\u000a pin-printing onto a hydrophilic membrane 16 chemically responsive\\u000a nanoporous pigments that are comprised of indicators immobilized in an\\u000a organic-ally modified silane (ormosil). The array has been used to\\u000a detect and identify 14 different natural and artificial sweeteners at\\u000a millimolar concentrations, as well as commonly used individual-serving\\u000a sweetener packets. The array

Christopher J. Musto; Sung H. Lim; Kenneth S. Suslick

2009-01-01

27

Colorimetric detection and identification of natural and artificial sweeteners.  

PubMed

A disposable, low-cost colorimetric sensor array has been created by pin-printing onto a hydrophilic membrane 16 chemically responsive nanoporous pigments that are comprised of indicators immobilized in an organically modified silane (ormosil). The array has been used to detect and identify 14 different natural and artificial sweeteners at millimolar concentrations, as well as commonly used individual-serving sweetener packets. The array has shown excellent reproducibility and long shelf life and has been optimized to work in the biological pH regime. PMID:20337402

Musto, Christopher J; Lim, Sung H; Suslick, Kenneth S

2009-08-01

28

Colorimetric paper bioassay for the detection of phenolic compounds.  

PubMed

A new type of paper based bioassay for the colorimetric detection of phenolic compounds including phenol, bisphenol A, catechol and cresols is reported. The sensor is based on a layer-by-layer (LbL) assembly approach formed by alternatively depositing layers of chitosan and alginate polyelectrolytes onto filter paper and physically entrapping the tyrosinase enzyme in between these layers. The sensor response is quantified as a color change resulting from the specific binding of the enzymatically generated quinone to the multilayers of immobilized chitosan on the paper. The color change can be quantified with the naked eye but a digitalized picture can also be used to provide more sensitive comparison to a calibrated color scheme. The sensor was optimized with respect to the number of layers, pH, enzyme, chitosan and alginate amounts. The colorimetric response was concentration dependent, with a detection limit of 0.86 (±0.1) ?g/L for each of the phenolic compounds tested. The response time required for the sensor to reach steady-state color varied between 6 and 17 min depending on the phenolic substrate. The sensor showed excellent storage stability at room temperature for several months (92% residual activity after 260 days storage) and demonstrated good functionality in real environmental samples. A procedure to mass-produce the bioactive sensors by inkjet printing the LbL layers of polyelectrolyte and enzyme on paper is demonstrated. PMID:23113670

Alkasir, Ramiz S J; Ornatska, Maryna; Andreescu, Silvana

2012-11-20

29

Masking nanoparticle surfaces for sensitive and selective colorimetric detection of proteins.  

PubMed

We have developed a convenient and efficient colorimetric detection system for protein targets using aptamer-gold nanoparticle conjugates. We take advantage of the correlation between the catalytic properties and the exposed surface area of the nanoparticles, which is inversely proportional to the amount of the aptamer-bound protein targets. As the concentration of the protein target increases, the nanoparticle surface area becomes more masked, thus increasing the reduction time of 4-nitrophenol for the color change. We also reduce the detection time by either redesigning the aptamer sequences or regulating their density. This detection system is highly selective, discriminating the target protein even at a concentration 1000 times higher than the limit of detection (LOD). Importantly, to the best of our knowledge, the LOD with the unaided eye in this work is the lowest for a colorimetric detection system using lysozyme as a model protein (16 nM). Lysozyme in chicken egg whites is directly analyzed using our detection system, whose results are in excellent agreement with the enzyme-linked immunosorbent assay (ELISA) analysis. PMID:24079726

Kim, Byung-Ho; Yoon, In Seon; Lee, Jae-Seung

2013-11-01

30

Reverse-flow apparatus for enhanced colorimetric detection of bacteriuria.  

PubMed Central

The reverse-flow apparatus is a new device for enhancing the detection of bacteria in urine. Bacteria are trapped onto a customized filter, and the pigments, crystals, and other interfering substances in the urine pass through the filter and are discarded. The bacteria are backflushed and are recovered as a concentrate, and the concentrate is then processed through the previously described colorimetric bacteriuria detection device. A total of 1,000 urine samples were obtained from randomly selected patients and were cultured on agar. Upon enumeration of the colonies, 160 urine samples were shown to contain more than 10(5) CFU/ml. In the bacteriuria detection device, 150 urine samples could not be processed (pigmenters and cloggers), and of the 850 urine samples processed, 127 were culture positive for 10(5) CFU/ml or greater, and 150 urine samples contained between 10(4) and 10(5) CFU/ml. At 10(5) CFU/ml, there were 140 false-positives and 14 false-negatives. When duplicate urine samples were processed through and concentrated by our new reverse-flow apparatus, all samples, including the above pigmenters and cloggers, could be tested in the bacteriuria detection device. The 150 unprocessable samples described above yielded 33 additional bacteria-positive urines, 23 at the 10(5)-CFU/ml cutoff and 10 at the 10(4)-to-10(5)-CFU/ml cutoff. There were 105 false-positives at 10(5) CFU/ml and only 2 false-negatives at the same level of bacteria. At 10(4) to 10(5) CFU/ml there was only 1% false-positive and 4% false-negative. The reverse-flow apparatus allows greater specificity and sensitivity in the rapid bacteriuria test. Urine containing 10(4) CFU/ml or more can now be detected with a 96% sensitivity in a total processing time of less than 2 min. Images PMID:6392325

Wallis, C; Melnick, J L

1984-01-01

31

A simple gold nanoparticles based colorimetric assay for the detection of highly reactive OH? radicals  

NASA Astrophysics Data System (ADS)

The design and development of simple methodology to measure short-lived OH? radicals is of considerable importance owing to the deleterious consequences associated with the oxidative stress that it can incur. Here, we describe a facile colorimetric assay that explores the plasmon absorbance of gold nanoparticles to realise rapid detection of OH? radicals. We have employed 4-hydroxy benzoic acid (4-HBA) as the reactive substrate that gives rise to a single hydroxylated product, protocatechuic acid (PCA) on reaction with OH? radicals. The resultant PCA showed capability of directly reducing Au3+ to give AuNPs while the original 4-HBA cannot reduce Au3+. The ensuing surface plasmon absorption of AuNPs was monitored for assaying the OH? radical activity. Redox active Fe2+ was used as a source of OH? radical and a linear relationship was observed between concentration of OH? radical and plasmon absorbance, allowing for quantitative estimation of OH? radical in solution.

Abilash, G.; Nandan, S. Sai; Sudan, C. Madhu; Sri Harsha, D. S. S.; Sadasivan, Rajesh; Janardhana, Ch.

2013-06-01

32

Rapid colorimetric hybridization assay for detecting amplified Helicobacter pylori DNA in gastric biopsy specimens.  

PubMed Central

A very simple, practical, sensitive, and specific colorimetric hybridization assay for detecting amplified Helicobacter pylori DNA is described. This assay, which combines a sensitive sandwich DNA hybridization reaction and a colorimetric protocol similar to those used in conventional enzyme immunoassays, was shown to be suitable for detecting H. pylori-infected gastric biopsy specimens and for monitoring the eradication of the pathogen after treatment. The specificity and sensitivity of the colorimetric hybridization assay were tested by assaying 27 H. pylori strains (4 reference and 23 clinical isolates), 9 strains of other Helicobacter spp. or Campylobacter spp., and 11 clinical isolates of other urease-positive bacteria. The likelihood of H. pylori detection in gastric biopsy specimens by the colorimetric hybridization assay was evaluated with 23 H. pylori-positive and 41 H. pylori-negative biopsy specimens on the basis of positive and negative results, respectively, of culture, rapid urease test, histological examination, and PCR. Biopsy specimens from 33 treated patients, endoscopied 4 to 8 weeks after the end of treatment, were also tested. All H. pylori strains showed positive results in the colorimetric hybridization assay, presenting optical densities at 450 nm (OD450S) of > or = 3.0. None of the other Helicobacter spp., Campylobacter spp., or the clinical isolates of other urease-positive bacteria showed OD450S equal to or greater than the cutoff (mean OD450 cutoff, 0.208). The colorimetric hybridization assay detected all 23 H. pylori-positive biopsy specimens (mean OD450, 2.910 +/- 0.295), while none of the H. pylori-negative biopsy specimens was shown to be positive in the assay (mean OD450, 0.108 +/- 0.025). H. pylori was considered to be not eradicated from three of the posttreatment biopsy specimens by culture, rapid urease test, histological examination, and PCR. They were all positive by the colorimetric hybridization assay, and their OD450S were > or = 3.0. The colorimetric hybridization assay also detected two other H. pylori-positive patients. Specimens from these two patients had negative culture, rapid urease test, and histology results, and a specimen from one of them also tested negative by PCR. These results indicate that the colorimetric hybridization assay is a suitable method both for the diagnosis of H. pylori in biopsy specimens and for the follow-up of patients after the end of treatment. PMID:8904408

Lage, A P; Fauconnier, A; Burette, A; Glupczynski, Y; Bollen, A; Godfroid, E

1996-01-01

33

Colorimetric and fluorescent dual detection of paraquat and diquat based on an anionic polythiophene derivative.  

PubMed

We have developed a colorimetric and fluorescent dual-response probe for the detection of paraquat and diquat in aqueous solutions based on an anionic polythiophene derivative. The detection limit of this approach can be as low as 10(-9) M by fluorescence measurements. PMID:23912221

Yao, Zhiyi; Hu, Xianping; Ma, Wenjuan; Chen, Xueliang; Zhang, Li; Yu, Junhua; Zhao, Yuliang; Wu, Hai-Chen

2013-10-01

34

A plastic colorimetric resonant optical biosensor for multiparallel detection of label-free biochemical interactions  

E-print Network

A plastic colorimetric resonant optical biosensor for multiparallel detection of label®nity assay. A surface receptor immobilization protocol demonstrating low nonspeci®c binding is used to detect; Proteomics; Diagnostics 1. Introduction For the majority of assays currently performed for geno- mics

Cunningham, Brian

35

DNAGOLD NANOPARTICLE BASED COLORIMETRIC COMPETITION ASSAY FOR THE DETECTION OF JaeSeung Lee, Pirmin A. Ulmann, Min Su Han, and Chad A. Mirkin  

E-print Network

DNAGOLD NANOPARTICLE BASED COLORIMETRIC COMPETITION ASSAY FOR THE DETECTION OF CYSTEINE NUNSEC researchers have developed a highly sensitive and selective colorimetric detection system placed thymidinethymidine (TT) mismatches complexed with Hg2+. The assay relies on the distance dependent

Shull, Kenneth R.

36

Carbon nanotube-based labels for highly sensitive colorimetric and aggregation-based visual detection of nucleic acids  

NASA Astrophysics Data System (ADS)

A novel carbon nanotube (CNT) derived label capable of dramatic signal amplification of nucleic acid detection and direct visual detection of target hybridization has been developed. Highly sensitive colorimetric detection of human acute lymphocytic leukemia (ALL) related oncogene sequences amplified by the novel CNT-based label was demonstrated. Atomic force microscope (AFM) images confirmed that a monolayer of horseradish peroxidase and detection probe molecules was immobilized along the carboxylated CNT carrier. The resulting CNT labels significantly enhanced the nucleic acid assay sensitivity by at least 1000 times compared to that of conventional labels used in enzyme-linked oligosorbent assay (ELOSA). An excellent detection limit of 1 × 10-12 M (60 × 10-18 mol in 60 µl) and a four-order wide dynamic range of target concentration were achieved. Hybridizations using these labels were coupled to a concentration-dependent formation of visible dark aggregates. Targets can thus be detected simply with visual inspection, eliminating the need for expensive and sophisticated detection systems. The approach holds promise for ultrasensitive and low cost visual inspection and colorimetric nucleic acid detection in point-of-care and early disease diagnostic application.

Lee, Ai Cheng; Ye, Jian-Shan; Ngin Tan, Swee; Poenar, Daniel P.; Sheu, Fwu-Shan; Kiat Heng, Chew; Meng Lim, Tit

2007-11-01

37

Rapid Colorimetric Detection of Antibody-Epitope Recognition at a Biomimetic Membrane Interface  

E-print Network

Rapid Colorimetric Detection of Antibody-Epitope Recognition at a Biomimetic Membrane Interface and epitopes by antibodies is a fundamental event in the initiation of immune response and plays a central role molecular system in which interactions between antibodies and peptide epitopes displayed at a biomimetic

Jelinek, Raz

38

A new rapid and simple colorimetric method to detect pyrazinamide resistance in Mycobacterium tuberculosis using nicotinamide  

Microsoft Academic Search

Objectives: The purpose of this study was to develop and assess a rapid method for pyrazinamide resistance detection in Mycobacterium tuberculosis using nicotinamide in a colorimetric resazurin assay. Methods: We have tested M. tuberculosis isolates using nicotinamide in a 96-well format with the redox indicator resazurin (REMA) and compared results using the BACTEC 460-TB system with two concentra- tions of

Anandi Martin; Howard Takiff; Peter Vandamme; Jean Swings; Juan Carlos Palomino; Francoise Portaels; Mycobacteriology Unit

2006-01-01

39

An ultra-sensitive colorimetric detection of tetracyclines using the shortest aptamer with highly enhanced affinity.  

PubMed

A shortened 8-mer ssDNA aptamer was successfully truncated for four different tetracyclines with high affinity. The ultrasensitive colorimetric detection of oxytetracycline using this shortened aptamer was possible, which was about 500-fold enhanced compared to that obtained using the original 76-mer aptamer. PMID:24185440

Kwon, Young Seop; Ahmad Raston, Nurul Hanun; Gu, Man Bock

2014-01-01

40

Simple colorimetric method for detecting degenerate strains of the cultivated basidiomycete Flammulina velutipes (Enokitake).  

PubMed

Degeneration of cultivated strains of Flammulina velutipes is a serious problem. We developed a simple colorimetric method to detect degenerate strains by using a liquid medium supplemented with bromothymol blue and lactose. The ability of a strain to develop normal mushrooms could be determined by the color of the medium. PMID:16204563

Magae, Yumi; Akahane, Kobun; Nakamura, Kimiyoshi; Tsunoda, Shigeyuki

2005-10-01

41

Magnetic particle-based enzyme assays and immunoassays for microcystins: from colorimetric to electrochemical detection.  

PubMed

In this work, magnetic particles (MPs) are used as supports for the immobilization of biorecognition molecules for the detection of microcystins (MCs). In one approach, a recombinant protein phosphatase 1 (PP1) has been conjugated to MPs via coordination chemistry, and MC-LR detection has been based on the inhibition of the enzyme activity. In the other approach, a monoclonal antibody (mAb) against MC-LR has been conjugated to protein G-coated MPs, and a direct competitive enzyme-linked immunoparticle assay (ELIPA) has been then performed. Conjugation of biomolecules to MPs has been first checked, and after optimization, MC detection has been performed. The colorimetric PPIA with PP1-MP and the best ELIPA strategy have provided limits of detection (LOD) of 7.4 and 3.9 ?g/L of MC-LR, respectively. The electrochemical ELIPA has decreased the LOD to 0.4 ?g/L, value below the guideline recommended by the World Health Organisation (WHO). The approaches have been applied to the analysis of a cyanobacterial culture and a natural bloom, and MC equivalent contents have been compared to those obtained by conventional assays and liquid chromatography-tandem mass spectrometry (LC-MS/MS). Results have demonstrated the viability of the use of MPs as biomolecule immobilization supports in biotechnological tools for MCs monitoring. PMID:23214443

Reverté, Laia; Garibo, Diana; Flores, Cintia; Diogène, Jorge; Caixach, Josep; Campàs, Mònica

2013-01-01

42

Colorimetric detection of trivalent chromium in aqueous solution using tartrate-capped silver nanoparticles as probe.  

PubMed

This study describes a simple and highly selective method for the colorimetric detection of trivalent chromium (Cr3+) using tartrate-capped silver nanoparticles (AgNPs) as probe. The addition of tartrate to the initially prepared AgNPs gives tartrate-stabilized AgNPs ascribing to the electrostatic repulsion of the highly negatively charged tartrate ions covered on the surface of AgNPs. It is found that, in the presence of Cr3+ in aqueous solution, the aggregation of tartrate-stabilized AgNPs occurs. The color of AgNPs suspension changes from yellow to pink and the surface plasmon absorption band broadens and red shifts, which could be applied for the colorimetric detection of Cr3+ in aqueous solution. The utilization of tartrate-stabilized AgNPs as probe substantially increases the selectivity and sensitivity for colorimetric detection of Cr3+. Control experiments with the addition of over 14 other metal ions, such as Pb2+, Zn2+, Cr2O7(2-), Cd2+, Co2+, Cu2+, Al3+, Ni2+, Mn2+, Ba2+, Fe3+, Ca2+, Mg2+, Sr+ do not result in a distinct change in the color or in the spectrum of the suspension, indicating that these metal ions do not interfere with the colorimetric detection of Cr3+. Under the conditions employed here, A502/A393 (ratio of absorption value at 502 nm to 393 nm) is linear with the concentration of Cr3+ within a concentration range from 0.1 to 1.17 microM with a detection limit of 0.06 microM. This study may offer a simple, rapid and sensitive approach to colorimetric detection of Cr3+ in aqueous solution. PMID:24245149

Xu, Yunbo; Dong, Yangjun; Jiang, Xue; Zhu, Ningning

2013-10-01

43

Gold nanoparticle-mediated detection of melamine based on a dual colorimetric and turbidometric readouts  

Microsoft Academic Search

A simple method for rapid detection of melamine in the food is presented. Citrate-coated gold nanoparticles (AuNPs) and cyanuric acid were utilized to generate melamine-concentration dependent colorimetric and turbidometric signals, respectively. As low as 0.4 ppm of melamine can be detected from the whole milk within 15 minutes with this new detection method and a simple acid precipitation based milk

Na Li; Fang Wei; Robert Lam; Jiaqi Zou; Stacy Cheng; Steven Lu; Dean Ho

2010-01-01

44

A colorimetric sensor based on anodized aluminum oxide (AAO) substrate for the detection of nitroaromatics.  

SciTech Connect

Simple and low cost colorimetric sensors for explosives detection were explored and developed. Anodized aluminum oxide (AAO) with large surface area through its porous structure and light background color was utilized as the substrate for colorimetric sensors. Fabricated thin AAO films with thickness less than {approx} 500 nm allowed us to observe interference colors which were used as the background color for colorimetric detection. AAO thin films with various thickness and pore-to-pore distance were prepared through anodizing aluminum foils at different voltages and times in dilute sulfuric acid. Various interference colors were observed on these samples due to their difference in structures. Accordingly, suitable anodization conditions that produce AAO samples with desired light background colors for optical applications were obtained. Thin film interference model was applied to analyze the UV-vis reflectance spectra and to estimate the thickness of the AAO membranes. We found that the thickness of produced AAO films increased linearly with anodization time in sulfuric acid. In addition, the growth rate was higher for AAO anodized using higher voltages. The thin film interference formulism was further validated with a well established layer by layer deposition technique. Coating poly(styrene sulfonate) sodium salt (PSS) and poly(allylamine hydrochloride) (PAH) layer by layer on AAO thin film consistently shifted its surface color toward red due to the increase in thickness. The red shift of UV-vis reflectance was correlated quantitatively to the number of layers been assembled. This sensitive red shift due to molecular attachment (increase in thickness) on AAO substrate was applied toward nitroaromatics detection. Aminopropyltrimethoxysilane (APTS) which can be attached onto AAO nanowells covalently through silanization and attract TNT molecules was coated and applied for TNT detection. UV-vis spectra of AAO with APTS shifted to the longer wavelength side due to TNT attachment. This red shift implied AAO thickness increased and positive detection of TNT molecules. It was also observed that both APTS and polyethyleneimine (PEI) were electron rich polymers which formed Meisenheimer complexes with TNT in solution and changed its color abruptly. This strong color change due to chemical reaction was applied as another approach for direct TNT detection. Commercial AAO films with long pores (60 {mu}m) and white background color were coated with APTS or PEI and then exposed to TNT in solution. These membranes turned to pink rapidly and eventually became visibly orange after a few hours with a strong absorption around 500 nm that was consistent with the formation of Meisenheimer complexes. The visible color change can be observed by unaided eyes and is suitable for nitroaromatics detection at higher concentration while interference color red shift in AAO thin film is designed for nitroaromatics detection at monolayer (nm) level.

Liu, Y.; Wang, H. H.; Indacochea, J. E.; Wang, M. L. (Materials Science Division); (Northeastern Univ.); (Univ. of Illinois at Chicago)

2011-12-15

45

Molecularly imprinted photonic hydrogels as colorimetric sensors for rapid and label-free detection of vanillin.  

PubMed

A novel colorimetric sensor for the rapid and label-free detection of vanillin, based on the combination of photonic crystal and molecular imprinting technique, was developed. The sensing platform of molecularly imprinted photonic hydrogel (MIPH) was prepared by a noncovalent and self-assembly approach using vanillin as a template molecule. Morphology characterization by scanning electron microscope (SEM) showed that the MIPH possessed a highly ordered three-dimensional (3D) macroporous structure with nanocavities. The vanillin recognition events of the created nonocavities could be directly transferred into readable optical signals through a change in Bragg diffraction of the ordered macropores array of MIPH. The Bragg diffraction peak shifted from 451 to 486 nm when the concentration of the vanillin was increased from 10?¹² to 10?³ mol L?¹ within 60 s, whereas there were no obvious peak shifts for methyl and ethyl vanillin, indicating that the MIPH had high selectivity and rapid response for vanillin. The adsorption results showed that the hierarchical porous structure and homogeneous layers were formed in the MIPH with higher adsorption capacity. The application of such a label-free sensor with high selectivity, high sensitivity, high stability, and easy operation might offer a potential method for rapid real-time detection of trace vanillin. PMID:22292481

Peng, Hailong; Wang, Shenqi; Zhang, Zhong; Xiong, Hua; Li, Jinhua; Chen, Lingxin; Li, Yanbin

2012-02-29

46

Highly sensitive colorimetric detection of 17?-estradiol using split DNA aptamers immobilized on unmodified gold nanoparticles.  

PubMed

Gold nanoparticle (AuNP) based colorimetric aptasensor have been developed for many analytes recently largely because of the ease of detection, high sensitivity, and potential for high-throughput analysis. Most of the target aptamers for detection have short sequences. However, the approach shows poor performance in terms of detection sensitivity for most of the long-sequence aptamers. To address this problem, for the first time, we split the 76?mer aptamer of 17?-estradiol into two short pieces to improve the AuNP based colorimetric sensitivity. Our results showed that the split P1 + P2 still retained the original 76?mer aptamer's affinity and specificity but increased the detection limit by 10-fold, demonstrating that as low as 0.1?ng/mL 17?-estradiol could be detected. The increased sensitivity may be caused by lower aptamer adsorption concentration and a lower affinity to the AuNPs of a short single-strand DNA (ssDNA) sequence. Our study provided a new way to use long-sequence aptamers to develop a highly sensitive AuNP-based colorimetric aptasensor. PMID:25524368

Liu, Jinchuan; Bai, Wenhui; Niu, Shucao; Zhu, Chao; Yang, Shuming; Chen, Ailiang

2014-01-01

47

Highly sensitive colorimetric detection of 17?-estradiol using split DNA aptamers immobilized on unmodified gold nanoparticles  

PubMed Central

Gold nanoparticle (AuNP) based colorimetric aptasensor have been developed for many analytes recently largely because of the ease of detection, high sensitivity, and potential for high-throughput analysis. Most of the target aptamers for detection have short sequences. However, the approach shows poor performance in terms of detection sensitivity for most of the long-sequence aptamers. To address this problem, for the first time, we split the 76?mer aptamer of 17?-estradiol into two short pieces to improve the AuNP based colorimetric sensitivity. Our results showed that the split P1 + P2 still retained the original 76?mer aptamer's affinity and specificity but increased the detection limit by 10-fold, demonstrating that as low as 0.1?ng/mL 17?-estradiol could be detected. The increased sensitivity may be caused by lower aptamer adsorption concentration and a lower affinity to the AuNPs of a short single-strand DNA (ssDNA) sequence. Our study provided a new way to use long-sequence aptamers to develop a highly sensitive AuNP-based colorimetric aptasensor. PMID:25524368

Liu, Jinchuan; Bai, Wenhui; Niu, Shucao; Zhu, Chao; Yang, Shuming; Chen, Ailiang

2014-01-01

48

Colorimetric detection of Shewanella oneidensis based on immunomagnetic capture and bacterial intrinsic peroxidase activity  

NASA Astrophysics Data System (ADS)

Rapid detection and enumeration of target microorganisms is considered as a powerful tool for monitoring bioremediation process that typically involves cleaning up polluted environments with functional microbes. A novel colorimetric assay is presented based on immunomagnetic capture and bacterial intrinsic peroxidase activity for rapidly detecting Shewanella oneidensis, an important model organism for environmental bioremediation because of its remarkably diverse respiratory abilities. Analyte bacteria captured on the immunomagnetic beads provided a bacterial out-membrane peroxidase-amplified colorimetric readout of the immunorecognition event by oxidizing 3, 3', 5, 5'-tetramethylbenzidine (TMB) in the present of hydrogen peroxide. The high-efficiency of immunomagnetic capture and signal amplification of peroxidase activity offers an excellent detection performance with a wide dynamic range between 5.0 × 103 and 5.0 × 106 CFU/mL toward target cells. Furthermore, this method was demonstrated to be feasible in detecting S. oneidensis cells spiked in environmental samples. The proposed colorimetric assay shows promising environmental applications for rapid detection of target microorganisms.

Wen, Junlin; Zhou, Shungui; Chen, Junhua

2014-06-01

49

Rapid colorimetric detection of Salmonella typhimuriumusing a selective filtration technique combined with antibody-magnetic nanoparticle nanocomposites.  

PubMed

Detection of pathogenic bacteria that pose a great risk to human health requires a rapid, convenient, reliable, and sensitive detection method. In this study, we developed a selective filtration method using monoclonal antibody (MAb)-magnetic nanoparticle (MNP) nanocomposites for the rapid and sensitive colorimetric detection of Salmonella typhimurium. The method contains two key steps: the immunomagnetic separation of the bacteria using MAb-MNP nanocomposites and the filtration of the nanocomposite-bound bacteria. Color signals from the nanocomposites remaining on the membrane were measured, which reflected the amount of bacteria in test samples. Immunomagnetic capture efficiencies of 8 to 90 % for various concentrations of the pathogen (2?×?10(4)-2?×?10(1) cells) were obtained. After optimization of the method, 2?×?10(1) cells of S. typhimurium in pure culture solution was detectable as well as in artificially inoculated vegetables (100 cells/g). The method was confirmed to be highly specific to S. typhimurium without cross-reaction to other pathogenic bacteria and could be concluded within 45 min, yielding results in a shorter or similar time period as compared with recently reported antibody immobilized on magnetic-particle-based methods. This study also demonstrated direct application of MAb-MNP nanocomposites without a dissociation step of bacteria from magnetic beads in colorimetric assays in practice. PMID:24337136

Shim, Won-Bo; Song, Jeong-Eon; Mun, Hyoyoung; Chung, Duck-Hwa; Kim, Min-Gon

2014-01-01

50

A cellulose-based bioassay for the colorimetric detection of pathogen DNA.  

PubMed

Cellulose-paper-based colorimetric bioassays may be used at the point of sampling without sophisticated equipment. This study reports the development of a colorimetric bioassay based on cellulose that can detect pathogen DNA. The detection was based on covalently attached single-stranded DNA probes and visual analysis. A cellulose surface functionalized with tosyl groups was prepared by the N,N-dimethylacetamide-lithium chloride method. Tosylation of cellulose was confirmed by scanning electron microscopy, Fourier transform infrared spectroscopy and elemental analysis. Sulfhydryl-modified oligonucleotide probes complementary to a segment of the DNA sequence IS6110 of Mycobacterium tuberculosis were covalently immobilized on the tosylated cellulose. On hybridization of biotin-labelled DNA oligonucleotides with these probes, a colorimetric signal was obtained with streptavidin-conjugated horseradish peroxidase catalysing the oxidation of tetramethylbenzamidine by H2O2. The colour intensity was significantly reduced when the bioassay was subjected to DNA oligonucleotide of randomized base composition. Initial experiments have shown a sensitivity of 0.1 ?M. A high probe immobilization efficiency (more than 90 %) was observed with a detection limit of 0.1 ?M, corresponding to an absolute amount of 10 pmol. The detection of M. tuberculosis DNA was demonstrated using this technique coupled with PCR for biotinylation of the DNA. This work shows the potential use of tosylated cellulose as the basis for point-of-sampling bioassays. PMID:25354892

Saikrishnan, Deepika; Goyal, Madhu; Rossiter, Sharon; Kukol, Andreas

2014-12-01

51

Label-free colorimetric aptasensor for sensitive detection of ochratoxin A utilizing hybridization chain reaction.  

PubMed

The combination of high selectivity of aptamer with the peroxidase-mimicking property of DNAzyme has presented considerable opportunities for designing colorimetric aptasensor for detection of ochratoxin A (OTA). The activities of both aptamer (as biorecognition element) and DNAzyme (as signal amplification element) are blocked via base pairing in the hairpin structure. Hybridization chain reaction (HCR) between two hairpin DNAs was employed to further improve the sensitivity of this method. The presence of OTA triggers the opening of the hairpin structure and the beginning of HCR, which results in the release of many DNAzyme, and generates enhanced colorimetric signals, which is correlated to the amounts of OTA with linear range between 0.01 to 0.32nM, and the limit of detection is 0.01nM under optimal conditions. OTA in yellow rice wine and wheat flour samples was also detected using this method. We demonstrate that a new colorimetric method for the detection of OTA has been established, which is simple, easy to conduct, label-free, sensitive, high throughput, and cost-saving. PMID:25682251

Wang, Chengke; Dong, Xiaoya; Liu, Qian; Wang, Kun

2015-02-20

52

Ultrasensitive colorimetric detection of Cu(2+) ion based on catalytic oxidation of l-cysteine.  

PubMed

As an essential element, copper ion (Cu(2+)) plays important roles in human beings for its participation in diverse metabolic processes as a cofactor and/or a structural component of enzymes. However, excessive uptake of Cu(2+) ion gives rise to the risk of certain diseases. So, it is important to develop simple ways to monitor and detect Cu(2+) ion. In this study, a simple, facile colorimetric sensor for the ultrasensitive determination of Cu(2+) ion was developed based on the following principle: l-cysteine and 1-chloro-2,4-dinitrobenzene (CDNB) could be conjugated to form the yellow product 2,4-dinitrophenylcysteine (DNPC), which was measurable at 355nm; however, upon addition of Cu(2+) ion, the absorbance of DNPC would be decreased owing to the Cu(2+) ion catalytic oxidation of l-cysteine to l-cystine in the presence of O2. Thus, the colorimetric detection of Cu(2+) ion could be achieved. The optimal pH, buffer, temperature and incubation time for the colorimetric sensor were obtained of pH 6.8 in 0.1M HEPES solution, 90°C and 50min, respectively. A good linearity within the range of 0.8-10nM (r=0.996) was attained, with a high detectability up to 0.5nM. Analyses of Cu(2+) ion in drinking water, lake water, seawater and biological samples were carried out and the method performances were found to agree well with that obtained by ICP-MS. The developed simple colorimetric sensor proved applicable for Cu(2+) ion determination in real samples with high sensitivity and selectivity. PMID:25194800

Yin, Kun; Li, Bowei; Wang, Xiaochun; Zhang, Weiwei; Chen, Lingxin

2015-02-15

53

"Red-to-blue" colorimetric detection of cysteine via anti-etching of silver nanoprisms.  

PubMed

The reported strategies for cysteine (Cys) colorimetric detection based on noble metal nanomaterials include triggering aggregation, etching or fluorescence quenching of nanomaterials by Cys. In this study, we propose a new strategy for Cys colorimetric detection, i.e. anti-etching of silver nanoprisms (AgNPRs). In the absence of Cys, iodide ions (I(-)) could etch the corners and edges of AgNPRs and induce the morphology transition from nanoprism to nanodisk, which results in color change of the AgNPR dispersion from blue to red. In its presence, however, Cys can prevent the AgNPRs from I(-) attack. In that case, the color of the AgNPR dispersion containing I(-) and Cys remains blue. The mechanism is confirmed by using UV-vis spectra, TEM, DLS, Raman spectra and XPS spectra. According to the sensing effect of the Cys detection system, the concentration of I(-) incubated with AgNPRs, incubation time of AgNPRs and I(-), and pH of AgNPR dispersions are optimized to 5.0 ?M, 10 min, and pH 6.2, respectively. Under the optimized conditions, the proposed Cys detection system has excellent selectivity and high sensitivity. The limit of detection (LOD) of our Cys detection system is 25 nM by the naked eye, which is much better than the reported lowest LOD by eye-vision (100 nM), and 10 nM by UV-vis spectroscopy. The results of Cys detection in rabbit urine or plasma samples reinforce that our Cys detection system is applicable for rapid colorimetric detection of Cys in real body fluid samples. PMID:25083798

Li, Yonglong; Li, Zihou; Gao, Yuexia; Gong, An; Zhang, Yujie; Hosmane, Narayan S; Shen, Zheyu; Wu, Aiguo

2014-09-21

54

Colorimetric chemosensor for multi-signaling detection of metal ions using pyrrole based Schiff bases  

NASA Astrophysics Data System (ADS)

Pyrrole based Schiff bases act as a highly sensitive probe for metal ions in aqueous medium. Both receptors R1 and R2 are sensitive towards Fe3+, Cu2+, Hg2+ and Cr3+ among the other metal ions. The sensing ability of the receptors are investigated via colorimetric, optical and emission spectroscopic studies. The binding stoichiometries of R1 and R2 with metal ions have been determined as 2:1 by using Job's plot. The colorimetric receptors exhibited high sensitivity with a low detection limit of ?M levels. In the presence of metal ions both receptors shows fluorescence quenching. This might be due to the photo induced electron transfer mechanism. The quenching constant was further determined using Stern-Volmer plot.

Udhayakumari, Duraisamy; Velmathi, Sivan

2014-03-01

55

The Disassembly of a Core-Satellite Nanoassembled Substrate for Colorimetric Biomolecular Detection  

PubMed Central

The disassembly of a core-satellite nanostructured substrate is presented as a colorimetric biosensor observable under dark field illumination. The fabrication method described herein utilizes thiol-mediated adsorption and streptavidin-biotin binding to self-assemble core-satellite nanostructures with a sacrificial linking peptide. Biosensing functionality is demonstrated with the protease trypsin and the optical properties of the nanoassemblies are characterized. A figure of merit is presented to determine the optimal core and satellite size for visual detection. Nanoassemblies with 50 nm cores and 30 nm or 50 nm satellites are superior as these structures achieve an orange to green color shift greater than 70 nm that is easily discernible by naked eye. This colorimetric substrate may prove to be a favorable alternative to liquid-based colloidal sensors and a useful visual readout mechanism for microfluidic diagnostic assays. PMID:21667984

Waldeisen, John R.; Wang, Tim; Ross, Benjamin M.; Lee, Luke P.

2012-01-01

56

NANOSENSOR DETECTS MERCURY IN WATER J.-S. Lee, M. S. Han, C. A. Mirkin, "Colorimetric Detection of Mercuric Ion (Hg2+  

E-print Network

NANOSENSOR DETECTS MERCURY IN WATER J.-S. Lee, M. S. Han, C. A. Mirkin, "Colorimetric Detection ­ 0647560 Mercuric ion (Hg2+ ) is one of the most stable inorganic forms of mercury. It is also a caustic

Shull, Kenneth R.

57

Visual detection of organophosphorus pesticides represented by mathamidophos using Au nanoparticles as colorimetric probe.  

PubMed

With citrate-coated Au nanoparticles as colorimetric probe, a novel visual method for rapid assay of organophosphorus pesticides has been developed. The assay principle is based on catalytic hydrolysis of acetylthiocholine into thiocholine by acetylcholinesterase, which induces the aggregation of Au nanoparticles and the color change from claret-red to purple or even grey. The original plasmon absorption of Au nanoparticles at 522 nm decreases, and simultaneously, a new absorption band appears at 675 nm. The irreversible inhibition of organophosphorus pesticides on acetylcholinesterase prevents aggregation of Au nanoparticles. Under optimum conditions, the absorbance at 522 nm of Au nanoparticles is related linearly to the concentration of mathamidophos in the range of 0.02-1.42 ?g/mL with a detection limit of 1.40 ng/mL. This colorimetric method has been successfully utilized to detect mathamidophos in vegetables with satisfactory results. The proposed colorimetric assay exhibits good reproducibility and accuracy, providing a simple and rapid method for the analysis of organophosphorus pesticides. PMID:22099654

Li, Hongkun; Guo, Jiajia; Ping, Hong; Liu, Lurui; Zhang, Minwei; Guan, Fengrui; Sun, Chunyan; Zhang, Qian

2011-12-15

58

Sensitive colorimetric detection of Listeria monocytogenes based on isothermal gene amplification and unmodified gold nanoparticles.  

PubMed

Listeria monocytogenes (L. monocytogenes), one of most problematic food-borne bacteria, is mainly transmitted through the food chain and may cause listeriosis. Therefore, the development of rapid and sensitive L. monocytogenes detection technique has become an urgent task. In this study, we proposed a method using hyperbranching rolling circle amplification (HRCA) combined with gold nanoparticle (GNP) based colorimetric strategy to offer an isothermal, highly sensitive and specific assay for the detection of L. monocytogenes. First, a linear padlock probe targeting a specific sequence in the hly gene was designed and followed with a ligation by Taq DNA ligase. After ligation, further amplification by HRCA with a thiolated primer and an unlabeled primer is performed. The resulting thiolated HRCA products were then captured onto GNP surface and made GNP more salt-tolerant. Detection of the bacteria can be achieved by a facilitated GNP based colorimetric testing using naked eyes. Through this approach, as low as 100 aM synthetic hly gene targets and about 75 copies of L. monocytogenes can be detected. The specificity is evaluated by distinguishing target L. monocytogenes from other bacteria. The artificial contaminated food samples were also detected for its potential applications in real food detection. This method described here is ideal for bacteria detection due to its simplicity and high sensitivity. PMID:23948710

Fu, Zhongyu; Zhou, Xiaoming; Xing, Da

2013-12-15

59

Nucleic acid-coupled colorimetric analyte detectors  

DOEpatents

The present invention relates to methods and compositions for the direct detection of analytes and membrane conformational changes through the detection of color changes in biopolymeric materials. In particular, the present invention provide for the direct colorimetric detection of analytes using nucleic acid ligands at surfaces of polydiacetylene liposomes and related molecular layer systems.

Charych, Deborah H. (Albany, CA); Jonas, Ulrich (Mainz, DE)

2001-01-01

60

Cationic Surfactant-Based Colorimetric Detection of Plasmodium Lactate Dehydrogenase, a Biomarker for Malaria, Using the Specific DNA Aptamer  

PubMed Central

A simple, sensitive, and selective colorimetric biosensor for the detection of the malarial biomarkers Plasmodium vivax lactate dehydrogenase (PvLDH) and Plasmodium falciparum LDH (PfLDH) was demonstrated using the pL1 aptamer as the recognition element and gold nanoparticles (AuNPs) as probes. The proposed method is based on the aggregation of AuNPs using hexadecyltrimethylammonium bromide (CTAB). The AuNPs exhibited a sensitive color change from red to blue, which could be seen directly with the naked eye and was monitored using UV-visible absorption spectroscopy and transmission electron microscopy (TEM). The reaction conditions were optimized to obtain the maximum color intensity. PvLDH and PfLDH were discernible with a detection limit of 1.25 pM and 2.94 pM, respectively. The applicability of the proposed biosensor was also examined in commercially available human serum. PMID:24992632

Lee, Seonghwan; Manjunatha, D H; Jeon, Weejeong; Ban, Changill

2014-01-01

61

Colorimetric Detection Of Substances In Liquids And Gases  

NASA Technical Reports Server (NTRS)

Thin polymer films containing solvatochromic dyes used as sensing elements to detect substances dissolved in liquids and gases. Dyes do not react with liquids in which dissolved, but do respond to changes in chemical compositions by changing color. Concentration determined visually by comparison of color with predetermined standard chart, or spectrophotometrically.

Harris, J. Milton; Mcgill, R. Andrew; Paley, Mark S.

1992-01-01

62

Utilization of unmodified gold nanoparticles in colorimetric detection  

NASA Astrophysics Data System (ADS)

This review begins with an overview of the appealing properties and various applications of gold nanoparticles, and briefly summarizes recent advances in using unmodified gold nanoparticles to detect different kinds of targets including nucleic acids, proteins, metal ions and small organic molecules. The key point to the unmodified gold nanoparticle-based visual detection assay is to control dispersion and aggregation of colloidal nanoparticles by targets of interest, which usually relies on affinities between gold nanoparticles and targets. The degree of dispersion or aggregation can be visualized through the change of the solution color or the precipitation of nanoparticles from the solution. Thus, the existence of the target molecules can be translated into optical signals and monitored by the naked eye conveniently. Finally, some future prospects of this research field are given.

He, Sha; Liu, Dingbin; Wang, Zhuo; Cai, Kaiyong; Jiang, Xingyu

2011-10-01

63

A G-quadruplex DNAzyme-based colorimetric method for facile detection of Alicyclobacillus acidoterrestris.  

PubMed

The rapid and sensitive detection of Alicyclobacillus acidoterrestris (AA) has become very important due to the frequent occurrence of fruit juice spoilage by AA. In the present study, using guaiacol, both as the metabolic product of AA related to its concentration and as a green colorimetric substrate of G-quadruplex DNAzyme, a novel G-quadruplex DNAzyme-based colorimetric method for a rapid detection of AA has been developed for the first time. Under optimal conditions, AA has been successfully detected in the concentration range of 10(2)-10(5) cfu mL(-1) with a detection limit of 85 cfu mL(-1). The recoveries ranging from 71.8% to 115.7% with relative standard deviation from 1.2% to 6.6% in spiked apple and orange juice samples were obtained. Results demonstrate that the sensitivity and precision of the developed method is comparable with most other analytical methods and is prominently rapid than them. We believe that the work provides a novel and effective approach and is beneficial for monitoring and reducing the risk of AA contaminations during the process of fruit juice production. PMID:24989256

Liu, Tao; Zhang, Xiao; Zhu, Wenxin; Liu, Wei; Zhang, Daohong; Wang, Jianlong

2014-09-01

64

Selective and sensitive colorimetric detection of stringent alarmone ppGpp with Fenton-like reagent.  

PubMed

Stringent alarmone, namely, guanosine 3'-diphosphate-5'-diphosphate (ppGpp), is a global regulator that plays a critical role in the survival, growth, metabolism, and many other vital processes of microorganisms. Because of its structural similarity to normal nucleotides, it is also a challenge for the selective and sensitive detection of ppGpp nowadays. Herein, we developed a colorimetric method for the selective detection of ppGpp by inhibiting the redox reaction between Fenton-like reagent (composed of Fe(3+) and H2O2) with 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS). Owing to the strong coordination affinity between ppGpp and Fe(3+), the chromogenic reaction between ABTS and Fenton-like reagent, occurred in aqueous medium at 37 °C and resulted in a bluish-green solution, which was inhibited with the addition of ppGpp. This phenomenon forms the basis for the colorimetric detection of ppGpp, with a detection limit of 0.19 ?M and good selectivity for ppGpp over other nucleotides and anions. Furthermore, the results could be visualized by the naked eye, and the sensitivity of the naked-eye observation could even be further improved with the aid of the introduction of a background color. PMID:25315398

Zheng, Lin Ling; Huang, Cheng Zhi

2014-12-01

65

Paper-based vapor detection of hydrogen peroxide: colorimetric sensing with tunable interface.  

PubMed

Vapor detection of hydrogen peroxide still remains challenging for conventional sensing techniques, though such vapor detection implies important applications in various practical areas, including locating IEDs. We report herein a new colorimetric sensor system that can detect hydrogen peroxide vapor down to parts per billion level. The sensory materials are based on the cellulose microfibril network of paper towels, which provide a tunable interface for modification with Ti(IV) oxo complexes for binding and reacting with H(2)O(2). The Ti(IV)-peroxide bond thus formed turns the complex from colorless to bright yellow with an absorption maximum around 400 nm. Such complexation-induced color change is exclusively selective for hydrogen peroxide, with no color change observed in the presence of water, oxygen, common organic reagents or other chelating reagents. This paper-based sensor material is disposable and one-time use, representing a cheap, simple approach to detect peroxide vapors. The reported sensor system also proves the technical feasibility of developing enhanced colorimetric sensing using nanofibril materials that will provide plenty of room to enlarge the surface area (by shrinking the fiber size), so as to enhance the surface interaction with gas phase. PMID:21355618

Xu, Miao; Bunes, Benjamin R; Zang, Ling

2011-03-01

66

Gold nanoparticle-based exonuclease III signal amplification for highly sensitive colorimetric detection of folate receptor  

NASA Astrophysics Data System (ADS)

By combining terminal protection of small molecule (folate)-capped DNA probes, exonuclease III signal amplification and gold nanoparticles, we developed a simple and label-free colorimetric assay for highly sensitive detection of folate receptor (FR). A detection limit of 50 fM FR was obtained using UV-vis spectrometry and 10 pM FR could be visualized by the naked eye.By combining terminal protection of small molecule (folate)-capped DNA probes, exonuclease III signal amplification and gold nanoparticles, we developed a simple and label-free colorimetric assay for highly sensitive detection of folate receptor (FR). A detection limit of 50 fM FR was obtained using UV-vis spectrometry and 10 pM FR could be visualized by the naked eye. Electronic supplementary information (ESI) available: Experimental details, salt and DNA-2 effects on the stability of the AuNP solution. See DOI: 10.1039/c3nr06139f

Yang, Xinjian; Gao, Zhiqiang

2014-02-01

67

Colorimetric detection of pesticides based on calixarene modified silver nanoparticles in water  

NASA Astrophysics Data System (ADS)

Highly stable silver nanoparticles modified with p-sulfonatocalix[n]arene (n = 4, 8) were synthesized via a one-pot protocol in aqueous media and characterized by transmission electron microscopy, FT-IR and UV-vis spectroscopy. In comparison with p-sulfonatocalix[8]arene modified silver nanoparticles, p-sulfonatocalix[4]arene modified silver nanoparticles can be utilized as a novel colorimetric probe for optunal, allowing a rapid quantitative assay of optunal down to a concentration of 10-7 M, showing a great potential for application to real-time in situ detection of optunal. The possible mechanism is discussed.

Xiong, Dejun; Li, Haibing

2008-11-01

68

Simple colorimetric detection of doxycycline and oxytetracycline using unmodified gold nanoparticles  

NASA Astrophysics Data System (ADS)

The interaction between tetracycline antibiotics and gold nanoparticles was studied. With citrate-coated gold nanoparticles as colorimetric probe, a simple and rapid detection method for doxycycline and oxytetracycline has been developed. This method relies on the distance-dependent optical properties of gold nanoparticles. In weakly acidic buffer medium, doxycycline and oxytetracycline could rapidly induce the aggregation of gold nanoparticles, resulting in red-to-blue (or purple) colour change. The experimental parameters were optimized with regard to pH, the concentration of the gold nanoparticles and the reaction time. Under optimal experimental conditions, the linear range of the colorimetric sensor for doxycycline/oxytetracycline was 0.06-0.66 and 0.59-8.85 ?g mL-1, respectively. The corresponding limit of detection for doxycycline and oxytetracycline was 0.0086 and 0.0838 ?g mL-1, respectively. This assay was sensitive, selective, simple and readily used to detect tetracycline antibiotics in food products.

Li, Jie; Fan, Shumin; Li, Zhigang; Xie, Yuanzhe; Wang, Rui; Ge, Baoyu; Wu, Jing; Wang, Ruiyong

2014-08-01

69

Colorimetric and electrochemical genosensors for the detection of Escherichia coli DNA without amplification in seawater.  

PubMed

Monitoring seawater, particularly recreational water, for indicator bacteria presence is required to protect the public from exposure to fecal pollution and to guarantee the safety of the swimming areas. Two methods for the detection and quantification of Escherichia coli DNA were developed: a colorimetric assay in a microplate and an electrochemical biosensor. These assays were based on the double hybridization recognition of a single-strand DNA capture probe immobilized onto the microplate or the screen-printed carbon electrode to its complementary ssDNA, which is hybridized with an ssDNA signal probe labeled with horseradish peroxidase enzyme. The hybridization recognition step used the colorimetric monitoring of the oxidation state of the 3,3',5,5'-tetramethylbenzidine. The electrochemical monitoring of the oxidation state of 5 methyl-phenazinium methyl sulfate was allowed when the horseradish-peroxidase was in the presence of the mediator (5 methyl-phenazinium methyl sulfate and hydrogen peroxide). These approaches allow for the detection and quantification of 10(2) to 10(3) cells of E. coli in 5l of seawater samples in less than 5h. Detection was achieved without a nucleic acid amplification step. The specificity of the two methods against E. coli was demonstrated by testing a panel of bacteria. The two methods can be used for on-site monitoring of seawater quality. PMID:24054570

Paniel, Nathalie; Baudart, Julia

2013-10-15

70

Ultra-rapid colorimetric assay for protease detection using magnetic nanoparticle-based biosensors.  

PubMed

Sensitive protease detection methods often require time-consuming techniques and expensive instrumentation. To overcome this limitation, a novel, simple, sensitive and selective colorimetric detection approach was developed. This biosensing configuration was validated by the use of prostate specific antigen (PSA) protease as a model target. In this method, proteolytically active PSA capable of cleaving PSA substrates caused the release of black-colored magnetic carrier complexes, exposing the gold color sensor surface visible to the naked eye. The assay showed excellent sensitivity as well as specificity, capable of discriminating between different types of protease targets. The biosensor was able to quantitatively detect different PSA concentrations with a detection limit as low as 10 ng mL(-1). The sensor offers the possibility of developing a wash-less and cost-effective point-of-care device due to the simplicity of the probe immobilization process and the elimination of labeling and reporter molecules during the biosensing step. PMID:23676852

Suaifan, Ghadeer A R Y; Esseghaier, Chiheb; Ng, Andy; Zourob, Mohammed

2013-07-01

71

Direct colorimetric determination of formaldehyde in textile fabrics and other materials  

SciTech Connect

A colorimetric method for direct determination of formaldehyde in textile fabrics and other materials is described. Color development and breaking formaldehyde bonds of the analyzed material occur simultaneously in the same reaction mixture without destruction of the material. The method is based on the color reaction of formaldehyde with indole-3-acetic acid or tryptophan. Common inorganic salts, higher aliphatic aldehydes, carbohydrates, amino acids (except tryptophan), and many other organic compounds do not react and do not interfere with the color reaction. Some interferences have been exhibited by acetaldehyde and glyoxal. The method was simple, accurate, and relatively insensitive to the reaction conditions. Only very small amounts of material are needed, and the reaction proceeds at room temperature. Different kinds of polymeric materials have been analyzed successfully (cotton, wool, plastics, collagen, wood, and furs). Most of the dyed fabrics or other materials could be analyzed in the same manner because under the reaction conditions the dyes were not extracted in the reaction mixture.

Chrastil, J.; Reinhardt, R.M.

1986-11-01

72

Direct Quantification of Carotenoids in Low Fat Baby Foods Via Laser Photoacoustics and Colorimetric Index *  

NASA Astrophysics Data System (ADS)

Carotenoids are important antioxidants found in various foods including those for nutrition of infants. In this investigation, the total carotenoid content (TCC) of nine different commercially available baby foods was quantified using colorimetric index * obtained via reflectance colorimetry (RC) and by laser photoacoustic spectroscopy (LPAS) at 473 nm. The latter requires a minimum of sample preparation and only a one time calibration step which enables practically direct quantification of TCC. Results were verified versus UV-Vis spectrophotometry (SP) as the reference technique. It was shown that RC and LPAS (at 473 nm) provide satisfactory results for *, = 0.9925 and = 0.9972, respectively. Other color indices do not show a correlation with TCC. When determining the TCC in baby foods containing tomatoes, it is necessary to select a different analytical wavelength to compensate for the effect of lycopene's presence in the test samples.

Dóka, O.; Ajtony, Zs.; Bicanic, D.; Valinger, D.; Végvári, Gy.

2014-12-01

73

Selective colorimetric NO(g) detection based on the use of modified gold nanoparticles using click chemistry.  

PubMed

A new colorimetric system for NO(g) detection is described. The detection method is based on the aggregation of modified AuNPs through a Cu(i) catalyzed click reaction promoted by the in situ reduction of Cu(ii) by NO. PMID:25613775

Martí, Almudena; Costero, Ana M; Gaviña, Pablo; Parra, Margarita

2015-02-01

74

Cationic polymers and aptamers mediated aggregation of gold nanoparticles for the colorimetric detection of arsenic(III) in aqueous solution.  

PubMed

As(III) specifically interacts with an arsenic-binding aptamer to form an As(III)-aptamer complex, so that the following cationic polymer can aggregate gold nanoparticles (AuNPs) and cause a remarkable change in color, which enables the colorimetric detection of As(III) with high selectivity and a detection limit of 5.3 ppb. PMID:22453203

Wu, Yuangen; Zhan, Shenshan; Wang, Faze; He, Lan; Zhi, Wenting; Zhou, Pei

2012-05-11

75

A simple colorimetric DNA detection by target-induced hybridization chain reaction for isothermal signal amplification.  

PubMed

A novel DNA detection method is presented based on a gold nanoparticle (AuNP) colorimetric assay and hybridization chain reaction (HCR). In this method, target DNA hybridized with probe DNA modified on AuNP, and triggered HCR. The resulting HCR products with a large number of negative charges significantly enhanced the stability of AuNPs, inhibiting aggregation of AuNPs at an elevated salt concentration. The approach was highly sensitive and selective. Using this enzyme-free and isothermal signal amplification method, we were able to detect target DNA at concentrations as low as 0.5 nM with the naked eye. Our method also has great potential for detecting other analytes, such as metal ions, proteins, and small molecules, if the target analytes could make HCR products attach to AuNPs. PMID:24780220

Ma, Cuiping; Wang, Wenshuo; Mulchandani, Ashok; Shi, Chao

2014-07-15

76

Colorimetric Detection of Specific DNA Segments Amplified by Polymerase Chain Reactions  

NASA Astrophysics Data System (ADS)

The polymerase chain reaction (PCR) procedure has many potential applications in mass screening. We describe here a general assay for colorimetric detection of amplified DNA. The target DNA is first amplified by PCR, and then a second set of oligonucleotides, nested between the first two, is incorporated by three or more PCR cycles. These oligonucleotides bear ligands: for example, one can be biotinylated and the other can contain a site for a double-stranded DNA-binding protein. After linkage to an immobilized affinity reagent (such as a cloned DNA-binding protein, which we describe here) and labeling with a second affinity reagent (for example, avidin) linked to horseradish peroxidase, reaction with a chromogenic substrate allows detection of the amplified DNA. This amplified DNA assay (ADA) is rapid, is readily applicable to mass screening, and uses routine equipment. We show here that it can be used to detect human immunodeficiency virus sequences specifically against a background of human DNA.

Kemp, David J.; Smith, Donald B.; Foote, Simon J.; Samaras, N.; Peterson, M. Gregory

1989-04-01

77

An Aptamer-Based Biosensor for Colorimetric Detection of Escherichia coli O157:H7  

PubMed Central

Background An aptamer based biosensor (aptasensor) was developed and evaluated for rapid colorimetric detection of Escherichia coli (E. coli) O157:H7. Methodology/Principal Findings The aptasensor was assembled by modifying the truncated lipopolysaccharides (LPS)-binding aptamer on the surface of nanoscale polydiacetylene (PDA) vesicle using peptide bonding between the carboxyl group of the vesicle and the amine group of the aptamer. Molecular recognition between E. coli O157:H7 and aptamer at the interface of the vesicle lead to blue-red transition of PDA which was readily visible to the naked eyes and could be quantified by colorimetric responses (CR). Confocal laser scanning microscope (CLSM) and transmission electron microscopy (TEM) was used to confirm the specific interactions between the truncated aptamer and E. coli O157:H7. The aptasensor could detect cellular concentrations in a range of 104? 108 colony-forming units (CFU)/ml within 2 hours and its specificity was 100% for detection of E. coli O157:H7. Compared with the standard culture method, the correspondent rate was 98.5% for the detection of E. coli O157:H7 on 203 clinical fecal specimens with our aptasensor. Conclusions The new aptasensor represents a significant advancement in detection capabilities based on the combination of nucleic acid aptamer with PDA vesicle, and offers a specific and convenient screening method for the detection of pathogenic bacteria. This technic could also be applied in areas from clinical analysis to biological terrorism defense, especially in low-resource settings. PMID:23145045

Zhong, Yuhong; Yang, Jie; Zhao, Yuhong; Wu, Wenping; Ye, Wei; Wen, Jie; Wang, Qi; Lu, Jianxin

2012-01-01

78

DNA probe based colorimetric method for detection of rifampicin resistance of Mycobacterium tuberculosis.  

PubMed

Rifampicin resistance of Mycobacterium tuberculosis is due to the occurrence of point mutations of the rpoB gene and the site of mutations vary geographically. Commercialized molecular based methods are not able to comprehensively detect rifampicin resistance as they target a limited number of gene mutations which are thought to be common. The aim of the study was to establish a low cost DNA probe based colorimetric method that can be customized for detection of rifampicin resistance of M. tuberculosis. Thus, enzyme-linked oligosorbent assay (ELOSA) was developed for the detection of polymerase chain reaction (PCR) amplified fragments of rpoB gene of M. tuberculosis DNA on microtiter plates. Forty two M. tuberculosis isolates (rifampicin resistant and susceptible isolates identified by agar proportion method) were used for developing and validating the assay. The point mutations of resistant isolates had been previously determined by DNA sequencing. Two fragments of rpoB gene were labeled with digoxigenin by PCR. The amplified products were hybridized with selected allele specific probes for three mutations and its wild types (six probes) which were captured onto streptavidin coated microtiter plates and detected by color development. Both sensitivity and specificity of all probes were ?96% and there was excellent discrimination (area under the curve (AUC)>0.9) between rifampicin susceptible cases and resistant cases. The probe-based colorimetric assay (PCR-ELOSA) developed in this study showed good agreement with reference mutations that were confirmed by DNA sequencing. In conclusion, PCR-ELOSA is a reliable and economical assay that can be customized for detection of rifampicin resistance. PMID:24275535

Adikaram, Chamila P; Perera, Jennifer; Wijesundera, Sandya S

2014-01-01

79

A gold nanoparticle-based label free colorimetric aptasensor for adenosine deaminase detection and inhibition assay.  

PubMed

A novel strategy for the fabrication of a colorimetric aptasensor using label free gold nanoparticles (AuNPs) is proposed in this work, and the strategy has been employed for the assay of adenosine deaminase (ADA) activity. The aptasensor consists of adenosine (AD) aptamer, AD and AuNPs. The design of the biosensor takes advantage of the special optical properties of AuNPs and the interaction between AuNPs and single-strand DNA. In the absence of ADA, the AuNPs are aggregated and are blue in color under appropriate salt concentration because of the grid structure of an AD aptamer when binding to AD, while in the presence of the analyte, AuNPs remain dispersed with red color under the same concentration of salt owing to ADA converting AD into inosine which has no affinity with the AD aptamer, thus allowing quantitative investigation of ADA activity. The present strategy is simple, cost-effective, selective and sensitive for ADA with a detection limit of 1.526 U L(-1), which is about one order of magnitude lower than that previously reported. In addition, a very low concentration of the inhibitor erythro-9-(2-hydroxy-3-nonyl) adenine (EHNA) could generate a distinguishable response. Therefore, the AuNP-based colorimetric biosensor has great potential in the diagnosis of ADA-relevant diseases and drug screening. PMID:25597304

Cheng, Fen; He, Yue; Xing, Xiao-Jing; Tan, Dai-Di; Lin, Yi; Pang, Dai-Wen; Tang, Hong-Wu

2015-03-01

80

A selectively fluorescein-based colorimetric probe for detecting copper(II) ion.  

PubMed

A novel fluorescein derivative 3-bromo-5-methylsalicylaldehyde fluorescein hydrazone (BMSFH) has been synthesized by reacting fluorescein hydrazide with 3-bromo-5-methylsalicylaldehyde and was developed as a new colorimetric probe for detection of Cu(2+). In the presence of Cu(2+) the BMSFH exhibits a rapid color change from colorless to yellow together with an obvious new band appeared at 502nm in the UV-vis absorption spectra. However, other common alkali-, alkaline earth-, transition- and rare earth metal ions induced no or minimal spectral changes. This change is attributed to BMSFH via coordination with Cu(2+) in a 1:1 stoichiometry and this binding to Cu(2+) is reversible, as indicated by the bleaching of the color when the Cu(2+) is extracted with EDTA. Experimental results indicate that the BMSFH can provide a rapid, selective and sensitive response to Cu(2+) with a linear dynamic range 3.0-330?mol/L and can be used as a potential Cu(2+) colorimetric probe in aqueous solution. PMID:24929315

Zhang, Li; Zhang, Xianhong

2014-12-10

81

A selectively fluorescein-based colorimetric probe for detecting copper(II) ion  

NASA Astrophysics Data System (ADS)

A novel fluorescein derivative 3-bromo-5-methylsalicylaldehyde fluorescein hydrazone (BMSFH) has been synthesized by reacting fluorescein hydrazide with 3-bromo-5-methylsalicylaldehyde and was developed as a new colorimetric probe for detection of Cu2+. In the presence of Cu2+ the BMSFH exhibits a rapid color change from colorless to yellow together with an obvious new band appeared at 502 nm in the UV-vis absorption spectra. However, other common alkali-, alkaline earth-, transition- and rare earth metal ions induced no or minimal spectral changes. This change is attributed to BMSFH via coordination with Cu2+ in a 1:1 stoichiometry and this binding to Cu2+ is reversible, as indicated by the bleaching of the color when the Cu2+ is extracted with EDTA. Experimental results indicate that the BMSFH can provide a rapid, selective and sensitive response to Cu2+ with a linear dynamic range 3.0-330 ?mol/L and can be used as a potential Cu2+ colorimetric probe in aqueous solution.

Zhang, Li; Zhang, Xianhong

2014-12-01

82

Surface modification for the collection and identification of fingerprints and colorimetric detection of urea nitrate.  

PubMed

Glass surfaces were modified with a combination of dyes and reagents to allow for the potential simultaneous recording of a detailed fingerprint and the detection of the explosive urea nitrate (UN), as a proof of principle of surface modification for simultaneous linking of identity to manipulation of explosives. By coating microscope slides with 9,10-diphenylanthracene (DPA), p-dimethylaminobenzaldehyde (p-DMAB) and p-dimethylaminocinnamaldehyde (p-DMAC), a colorimetric change was observed in the presence of UN, while revealing a fingerprint with enough resolution to isolate at least 10 minutiae. This is the first step in creating point-of-care devices capable of detecting low concentrations of explosives and drug metabolites and connecting them to a fingerprint. PMID:25066205

Cross, Shoronia N; Quinteros, Elliot; Roberts, Marcel

2015-01-01

83

“Naked-eye” colorimetric and “turn-on” fluorometric chemosensors for reversible Hg2+ detection  

NASA Astrophysics Data System (ADS)

Two new Hg2+-colorimetric and fluorescent sensors based on 2-[3-(2-aminoethylsulfanyl) propylsulfanyl]ethanamine covalently bound to one and two units of rhodamine-6G moieties, 1 and 2, were synthesised, and their sensing behaviors toward metal ions were investigated by UV/Vis and fluorescence spectroscopy. Upon the addition of Hg2+, the sensors exhibited highly sensitive “turn-on” fluorescence enhancement as well as a color change from colorless to pink, which was readily noticeable for naked eye detection. Especially, 1 exhibited the reversible behavior and revealed a very high selectivity in the presence of competitive ions, particularly Cu2+, Ag+, Pb2+, Ca2+, Cd2+, Co2+, Fe2+, Mn2+, Na+, Ni2+, K+, Ba2+, Li+ and Zn2+, with a low detection limit of 1.7 ppb toward Hg2+.

Wanichacheva, Nantanit; Praikaew, Panida; Suwanich, Thanapat; Sukrat, Kanjarat

2014-01-01

84

Sensitive and selective detection of cysteine using gold nanoparticles as colorimetric probes.  

PubMed

We report herein the development of a highly sensitive and selective colorimetric detection method for cysteine using gold nanoparticles probes. This assay relies upon the distance-dependent optical properties of gold nanoparticles, the self-assembly of cysteine on gold nanoparticles, and the interaction of a 2:1 cysteine/Cu2+ complex. In the presence of Cu2+, cysteine could rapidly induce the aggregation of gold nanoparticles, thereby resulting in red-to-blue (or purple) color change. The concentration of cysteine can be determined by monitoring with the naked eye or a UV-vis spectrometer. The present limit of detection for cysteine is 10 nM. This method exhibits excellent selectivity for cysteine over other alpha-amino acids, glutathione, thioglycolic acid and mercaptoethyl alcohol. PMID:19562202

Li, Li; Li, Baoxin

2009-07-01

85

An enzyme-free and amplified colorimetric detection strategy via target-aptamer binding triggered catalyzed hairpin assembly.  

PubMed

Here we introduce an enzyme-free and colorimetric detection strategy for small molecule adenosine. The approach is based on the adenosine-aptamer binding triggered liberation of an initiator strand that consecutively catalyzes DNA hairpins hybridized from singles to couples. These couples induce gold nanoparticles assembled via crosslinking, which could be visualized by a color change. PMID:25435498

Quan, Ke; Huang, Jin; Yang, Xiaohai; Yang, Yanjing; Ying, Le; Wang, He; He, Yong; Wang, Kemin

2015-01-18

86

One-pot synthesized DNA-templated Ag/Pt bimetallic nanoclusters as peroxidase mimics for colorimetric detection of thrombin.  

PubMed

We developed a facile one-step approach to synthesize DNA-templated Ag/Pt bimetallic nanoclusters (DNA-Ag/Pt NCs), which possess highly-efficient peroxidase-like catalytic activity. With this finding, an aptamer based sandwich-type strategy is employed to design a label-free colorimetric aptasensor for the protein detection with high sensitivity and selectivity. PMID:25223346

Zheng, Cheng; Zheng, Ai-Xian; Liu, Bo; Zhang, Xiao-Long; He, Yu; Li, Juan; Yang, Huang-Hao; Chen, Guonan

2014-11-01

87

A simple and sensitive method for visual detection of heparin using positively-charged gold nanoparticles as colorimetric probes.  

PubMed

The electrostatic interaction between the negatively-charged heparin and the positively-charged gold nanoparticles leads to aggregation of gold nanoparticles and a color change from red to blue in solution, thus providing a simple and visual approach to colorimetric detection of heparin. PMID:21246153

Cao, Rui; Li, Baoxin

2011-03-14

88

Highly sensitive colorimetric detection of lead using maleic acid functionalized gold nanoparticles.  

PubMed

Highly sensitive colorimetric detection for Pb(2+) has been developed using maleic acid (MA) functionalized GNP. The -COOH on MA was used to modify GNP surface whereas the other -COOH functional group have strong affinity to coordination behavior of Pb(2+) allowing the selective formation more than other ions. MA-GNPs solution changed from red to blue color after the addition of Pb(2+) due to nanoparticle aggregation. The different optical absorption and discriminate of particle size between the MA-GNPs solution with and without Pb(2+) were characterized by UV-visible spectroscopy and transmission electron microscopy (TEM), respectively. The color intensity as a function of Pb(2+) concentration gave a linear response in the range of 0.0-10.0µgL(-1) (R(2)=0.990). The detection limit was found at 0.5µgL(-1) by naked eye and can be completed the analysis within 15min. The MA-GNPs aggregated with Pb(2+) showed high selectivity when was compared to other metal ions (As(3+), Ca(2+), Cd(2+), Co(2+), Cu(2+), Fe(3+), Hg(2+), Mg(2+), Mn(2+), Ni(2+), Pb(2+) and Zn(2+)) and anions (Cl(-), NO3(-) and SO4(2-)). Our proposed method was also applied for the determination of Pb(2+) in real drinking water samples from 5 sources. The result of real water samples were not statistically significant different from the standard methods at the 95% confidence level (pair t-test method). Moreover, we evaluated our proposed method for the determination of trace Pb(2+) concentration in real breast milk samples. The recoveries were acceptable and ranged from 101 to 104% for spiked Pb(2+) in real breast milk samples. Thus, MA-GNP colorimetric sensing provides a simple, rapid, sensitive, easy-to-use, inexpensive and low detection limit for the monitoring of Pb(2+). PMID:25476352

Ratnarathorn, Nalin; Chailapakul, Orawon; Dungchai, Wijitar

2015-01-15

89

A fast, sensitive and easy colorimetric assay for chitinase and cellulase activity detection  

PubMed Central

Background Most of the current colorimetric methods for detection of chitinase or cellulase activities on the insoluble natural polymers chitin and cellulose depend on a chemical redox reaction. The reaction involves the reducing ends of the hydrolytic products. The Schales’ procedure and the 3,5-dinitrosalicylic acid (DNS) method are two examples that are commonly used. However, these methods lack sensitivity and present practical difficulties of usage in high-throughput screening assays as they require boiling or heating steps for color development. Results We report a novel method for colorimetric detection of chitinase and cellulase activity. The assay is based on the use of two oxidases: wild-type chito-oligosaccharide oxidase, ChitO, and a mutant thereof, ChitO-Q268R. ChitO was used for chitinase, while ChitO-Q268R was used for cellulase activity detection. These oxidases release hydrogen peroxide upon the oxidation of chitinase- or cellulase-produced hydrolytic products. The hydrogen peroxide produced can be monitored using a second enzyme, horseradish peroxidase (HRP), and a chromogenic peroxidase substrate. The developed ChitO-based assay can detect chitinase activity as low as 10 ?U within 15 minutes of assay time. Similarly, cellulase activity can be detected in the range of 6 to 375 mU. A linear response was observed when applying the ChitO-based assay for detecting individual chito-oligosaccharides and cello-oligosaccharides. The detection limits for these compounds ranged from 5 to 25 ?M. In contrast to the other commonly used methods, the Schales’ procedure and the DNS method, no boiling or heating is needed in the ChitO-based assays. The method was also evaluated for detecting hydrolytic activity on biomass-derived substrates, that is, wheat straw as a source of cellulose and shrimp shells as a source of chitin. Conclusion The ChitO-based assay has clear advantages for the detection of chitinase and cellulase activity over the conventional Schales’ procedure and DNS method. The detection limit is lower and there is no requirement for harsh conditions for the development of the signal. The assay also involves fewer and easier handling steps. There is no need for boiling to develop the color and results are available within 15 minutes. These aforementioned features render this newly developed assay method highly suitable for applications in biorefinery-related research. PMID:24612932

2014-01-01

90

Highly sensitive and selective colorimetric detection of cartap residue in agricultural products.  

PubMed

The residue of pesticide has posed a serious threat to human health. Fast, broad-spectrum detection methods are necessary for on-site screening of various types of pesticides. With citrate-coated Au nanoparticles (Au NPs) as colorimetric probes, a visual and spectrophotometric method for rapid assay of cartap, which is one of the most important pesticides in agriculture, is reported for the first time. Based on the color change of Au colloid solution from wine-red to blue resulting from the aggregation of Au NPs, cartap could be detected in the concentration range of 0.05-0.6 mg/kg with a low detection limit of 0.04 mg/kg, which is much lower than the strictest cartap safety requirement of 0.1 mg/kg. Due to the limited research on the rapid detection of cartap based on Au NPs, the performance of the present method was evaluated through aggregation kinetics, interference influence, and sample pretreatment. To further demonstrate the selectivity and applicability of the method, cartap detection is realized in cabbage and tea with excellent analyte concentration recovery. These results demonstrate that the present method provides an easy and effective way to analyze pesticide residue in common products, which is of benefit for the rapid risk evaluation and on-site screening of pesticide residue. PMID:23158338

Liu, Wei; Zhang, Daohong; Tang, Yafan; Wang, Yashan; Yan, Fei; Li, Zhonghong; Wang, Jianlong; Zhou, H Susan

2012-11-15

91

Colorimetric detection of melamine based on methanobactin-mediated synthesis of gold nanoparticles.  

PubMed

A simple and rapid field-portable colorimetric method for the detection of melamine in liquid milk was reported. Methanobactin (Mb) could reduce Au (III) to Au (0) and mediate the synthesis of gold nanoparticles (Au-NPs). Upon the addition of melamine, melamine interacted with oxazolone ring of Mb, which interrupted the formation of Au-NPs. Melamine could also stimulate the aggregation of formed Au-NPs. In this paper, these characteristics have been used to detect melamine in liquid milk by naked eyes observation with a detection limit of 5.56×10(-6)M (0.7mg/kg). Further, the plasmon absorbance of the formed Au-NPs allowed the quantitative detection of melamine by UV-vis spectrometer. A linear correlation was existed between the absorbance and the melamine concentration ranging from 3.90×10(-7)M to 3.97×10(-6)M with a correlation coefficient of 0.9685. The detection limit (3?) obtained by UV-vis spectrum was as low as 2.38×10(-7)M (i.e., 0.03mg/kg). PMID:25529708

Xin, Jia-Ying; Zhang, Lan-Xuan; Chen, Dan-Dan; Lin, Kai; Fan, Hong-Chen; Wang, Yan; Xia, Chun-Gu

2015-05-01

92

Detection of mercury(II) ions using colorimetric gold nanoparticles on paper-based analytical devices.  

PubMed

An on-field colorimetric sensing strategy employing gold nanoparticles (AuNPs) and a paper-based analytical platform was investigated for mercury ion (Hg(2+)) detection at water sources. By utilizing thymine-Hg(2+)-thymine (T-Hg(2+)-T) coordination chemistry, label-free detection oligonucleotide sequences were attached to unmodified gold nanoparticles to provide rapid mercury ion sensing without complicated and time-consuming thiolated or other costly labeled probe preparation processes. Not only is this strategy's sensing mechanism specific toward Hg(2+), rather than other metal ions, but also the conformational change in the detection oligonucleotide sequences introduces different degrees of AuNP aggregation that causes the color of AuNPs to exhibit a mixture variance. To eliminate the use of sophisticated equipment and minimize the power requirement for data analysis and transmission, the color variance of multiple detection results were transferred and concentrated on cellulose-based paper analytical devices, and the data were subsequently transmitted for the readout and storage of results using cloud computing via a smartphone. As a result, a detection limit of 50 nM for Hg(2+) spiked pond and river water could be achieved. Furthermore, multiple tests could be performed simultaneously with a 40 min turnaround time. These results suggest that the proposed platform possesses the capability for sensitive and high-throughput on-site mercury pollution monitoring in resource-constrained settings. PMID:24932699

Chen, Guan-Hua; Chen, Wei-Yu; Yen, Yu-Chun; Wang, Chia-Wei; Chang, Huan-Tsung; Chen, Chien-Fu

2014-07-15

93

Sensitive and specific colorimetric DNA detection by invasive reaction coupled with nicking endonuclease-assisted nanoparticles amplification.  

PubMed

Colorimetric DNA detection is preferable to methods in clinical molecular diagnostics, because no expensive equipment is required. Although many gold nanoparticle-based colorimetric DNA detection strategies have been developed to analyze DNA sequences of interest, few of them can detect somatic mutations due to their insufficient specificity. In this study, we proposed a colorimetric DNA detection method by coupling invasive reaction with nicking endonuclease-assisted nanoparticles amplification (IR-NEANA). A target DNA firstly produces many flaps by invasive reaction. Then the flaps are converted to targets of nicking reaction-assisted nanoparticles amplification by ligation reaction to produce the color change of AuNPs, which can be observed by naked eyes. The detection limit of IR-NEANA was determined as 1pM. Most importantly, the specificity of the method is high enough to pick up as low as 1% mutant from a large amount of wild-type DNA backgrounds. The EGFR gene mutated at c.2573 T>G in 9 tissue samples from non-small cell lung cancer patients were successfully detected by using IR-NEANA, suggesting that our proposed method can be used to detect somatic mutations in biological samples. PMID:25460881

Zou, Bingjie; Cao, Xiaomei; Wu, Haiping; Song, Qinxin; Wang, Jianping; Kajiyama, Tomoharu; Kambara, Hideki; Zhou, Guohua

2015-04-15

94

Colorimetric detection of human chorionic gonadotropin using catalytic gold nanoparticles and a peptide aptamer.  

PubMed

We combined catalytic gold nanoparticles (AuNPs) with an hCG-specific peptide aptamer to create a simple, sensitive, label-free colorimetric assay for hCG. The applications of this colorimetric biosensor may be expanded by changing the peptide aptamer. PMID:25302679

Chang, Chia-Chen; Chen, Chie-Pein; Lee, Chung-Han; Chen, Chen-Yu; Lin, Chii-Wann

2014-11-28

95

Aptamer-based colorimetric detection of platelet-derived growth factor using unmodified gold nanoparticles.  

PubMed

We developed a simple method for the detection of platelet-derived growth factors (PDGFs) based on base stacking effect coupled with an unmodified gold nanoparticle (AuNP) indicator. In the absence of a target, an aptamer probe and a capture probe stably co-exist in a solution, as it is difficult to sustain an interaction between both these probes due to the short 8bp duplex. However, when a target protein binds to the aptamer probe, the strong base stacking effect can lead to a favorable and stable interaction between the aptamer and capture probes. Hence, the capture probe dissociates from the AuNP surfaces, inducing AuNP aggregation. Compared with other AuNP-based aptasensors for PDGFs, using this base stacking effect can overcome a structured-aptamer method's limitation of requiring thiolated-aptamer-modified AuNPs. Under optimal detection conditions, this label-free colorimetric sensor could detect PDGFs down to 6nM with high selectivity in the presence of other interferring proteins. This simple detection approach provides viable methods for a structured-aptamer sensing protocol. PMID:23202340

Chang, Chia-Chen; Wei, Shih-Chung; Wu, Tzu-Heng; Lee, Chung-Han; Lin, Chii-Wann

2013-04-15

96

Colorimetric detection of DNA, small molecules, proteins, and ions using unmodified gold nanoparticles and conjugated polyelectrolytes.  

PubMed

We have demonstrated a novel sensing strategy employing single-stranded probe DNA, unmodified gold nanoparticles, and a positively charged, water-soluble conjugated polyelectrolyte to detect a broad range of targets including nucleic acid (DNA) sequences, proteins, small molecules, and inorganic ions. This nearly "universal" biosensor approach is based on the observation that, while the conjugated polyelectrolyte specifically inhibits the ability of single-stranded DNA to prevent the aggregation of gold-nanoparticles, no such inhibition is observed with double-stranded or otherwise "folded" DNA structures. Colorimetric assays employing this mechanism for the detection of hybridization are sensitive and convenient--picomolar concentrations of target DNA are readily detected with the naked eye, and the sensor works even when challenged with complex sample matrices such as blood serum. Likewise, by employing the binding-induced folding or association of aptamers we have generalized the approach to the specific and convenient detection of proteins, small molecules, and inorganic ions. Finally, this new biosensor approach is quite straightforward and can be completed in minutes without significant equipment or training overhead. PMID:20534499

Xia, Fan; Zuo, Xiaolei; Yang, Renqiang; Xiao, Yi; Kang, Di; Vallée-Bélisle, Alexis; Gong, Xiong; Yuen, Jonathan D; Hsu, Ben B Y; Heeger, Alan J; Plaxco, Kevin W

2010-06-15

97

Colorimetric detection of DNA, small molecules, proteins, and ions using unmodified gold nanoparticles and conjugated polyelectrolytes  

PubMed Central

We have demonstrated a novel sensing strategy employing single-stranded probe DNA, unmodified gold nanoparticles, and a positively charged, water-soluble conjugated polyelectrolyte to detect a broad range of targets including nucleic acid (DNA) sequences, proteins, small molecules, and inorganic ions. This nearly “universal” biosensor approach is based on the observation that, while the conjugated polyelectrolyte specifically inhibits the ability of single-stranded DNA to prevent the aggregation of gold-nanoparticles, no such inhibition is observed with double-stranded or otherwise “folded” DNA structures. Colorimetric assays employing this mechanism for the detection of hybridization are sensitive and convenient—picomolar concentrations of target DNA are readily detected with the naked eye, and the sensor works even when challenged with complex sample matrices such as blood serum. Likewise, by employing the binding-induced folding or association of aptamers we have generalized the approach to the specific and convenient detection of proteins, small molecules, and inorganic ions. Finally, this new biosensor approach is quite straightforward and can be completed in minutes without significant equipment or training overhead. PMID:20534499

Xia, Fan; Zuo, Xiaolei; Yang, Renqiang; Xiao, Yi; Kang, Di; Vallée-Bélisle, Alexis; Gong, Xiong; Yuen, Jonathan D.; Hsu, Ben B. Y.; Heeger, Alan J.; Plaxco, Kevin W.

2010-01-01

98

Field-deployable colorimetric biosensor system for the rapid detection of pathogenic organisms  

NASA Astrophysics Data System (ADS)

The rapid identification of pathogenic organisms is necessary for recognizing and managing human and environmental health risks. Numerous detection schemes are available, but most are difficult to employ in non-laboratory settings due to their need for bulky, specialized equipment, multiple reagents, or highly trained personnel. To address this problem, a rapid, field-compatible biosensor system based on the colorimetric detection of nucleic acid hybrids was developed. Peptide nucleic acid (PNA) probes were used to capture ribosomal RNA sequences from environmental samples. Non-target nucleic acids, including single-base mismatches flanked by adenines and uracils, were removed with a micrococcal nuclease digestion step. Matched PNA-RNA hybrids remained intact and were indicated by the cyanine dye DiSC2(5). PNA-containing duplexes function as templates for the aggregation of DiSC2(5), visualized as a change in solution color from blue to purple. This transition can be measured as an increase in the solution absorbance at 540 nm (dye aggregate) at the expense of the dye monomer peak at 650 nm. These concomitant spectral changes were used to calculate a "hybridization signal" using the ratio A aggregate/Amonomer ? A540/A650. Testing with pathogenic environmental samples was accomplished using two model organisms: the harmful algal bloom-causing dinoflagellate Alexandrium species, and the potato wart disease-causing fungus Synchytrium endobioticum. In both cases, the colorimetric approach was able to distinguish the targets with sensitivities rivaling those of established techniques, but with the advantages of decreased hands-on time and cost. Assay fieldability was tested with a portable colorimeter designed to quantify the dye-indicated hybridization signal and assembled from commercially available components. Side-by-side testing revealed no difference in the sensing performance of the colorimeter compared to a laboratory spectrophotometer (Pearson's r=0.99935). Assay results were obtained within 15 minutes, with a limit of detection down to 10--17 mole. This quick, inexpensive and robust system has the potential to replace laborious pathogen identification schemes in field environments, and is easily adapted for the detection of different organisms.

Duy, Janice

99

A colorimetric sandwich-type assay for sensitive thrombin detection based on enzyme-linked aptamer assay.  

PubMed

A colorimetric sandwich-type assay based on enzyme-linked aptamer assay has been developed for the fast and sensitive detection of as low as 25 fM of thrombin with high linearity. Aptamer-immobilized glass was used to capture the target analyte, whereas a second aptamer, functionalized with horseradish peroxidase (HRP), was employed for the conventional 3,5,3',5'-tetramethylbenzidine (TMB)-based colorimetric detection. Without the troublesome antibody requirement of the conventional enzyme-linked immunosorbent assay (ELISA), as low as 25 fM of thrombin could be rapidly and reproducibly detected. This assay has superior, or at least equal, recovery and accuracy to that of conventional antibody-based ELISA. PMID:24937288

Park, Jun Hee; Cho, Yea Seul; Kang, Sungmuk; Lee, Eun Jeong; Lee, Gwan-Ho; Hah, Sang Soo

2014-10-01

100

Fabrication of a colorimetric biosensing platform for the detection of protein-DNA interaction.  

PubMed

Protein-DNA interaction plays important roles in many cellular processes, and there is an urgent demand for valid methods to monitor the interaction. In view of this, we propose a simple label-free colorimetric platform for the detection of protein-DNA interaction. Protein-DNA couples together with peroxidase-mimicking DNAzyme and exonuclease are elaborately incorporated into an integrated biosensing system. Besides the simplicity and efficiency, the strategy also has a great advantage for its universality in the detection of different protein-DNA couples. In our experiments, effective validation of our approach can be supported by two different protein-DNA couples (estrogen receptor ? and nuclear factor kappa B). Experimental results show that the DNAzyme is competent to give rise to evident readout signals to monitor protein-DNA couples. Furthermore, with the substitution of DNA binding sequence in the probe, this method could be extended to a general platform for the detection of protein-DNA interaction. PMID:23517826

Ye, Zonghuang; Zhang, Wei; Liu, Lili; Chen, Guifang; Shen, Zhongming; Zhou, Nandi

2013-08-15

101

A field-deployable colorimetric bioassay for the rapid and specific detection of ribosomal RNA.  

PubMed

Rapid and specific on-site detection of disease-causing or toxin-producing organisms is essential to public health and safety. Many molecular recognition methods target ribosomal RNA sequences due to their specificity and abundance in the cell. In this work RNA targets were identified and quantified using a colorimetric bioassay. Peptide nucleic acid (PNA) probes were used to capture RNA targets, and a micrococcal nuclease digestion was performed to remove all non-target nucleic acids, including single base mismatches flanked by adenines or uracils. Perfectly-matched PNA-RNA hybrids remained intact and were detected using the symmetrical cyanine dye 3,3'-diethylthiadicarbocyanine iodide (DiSC2(5)). Assay applicability to complex samples was demonstrated using mixtures containing RNA sequences from two related, harmful algal bloom-causing Alexandrium species. Target RNA was detected even in mixtures with mismatched sequences in excess of the perfect match. The fieldability of the assay was tested with a portable two-wavelength colorimeter developed to quantify the dye-indicated hybridization signal. The colorimeter sensing performance was shown to be comparable to a laboratory spectrophotometer. This quick, inexpensive and robust system has the potential to replace laborious identification schemes in field environments. PMID:22749775

Duy, Janice; Smith, Rosemary L; Collins, Scott D; Connell, Laurie B

2014-02-15

102

Folic acid functionalized silver nanoparticles with sensitivity and selectivity colorimetric and fluorescent detection for Hg2+ and efficient catalysis.  

PubMed

In this research, folic acid functionalized silver nanoparticles (FA-AgNPs) were selected as a colorimetric and a 'turn on' fluorescent sensor for detecting Hg(2+). After being added into Hg(2+), AgNPs can emit stable fluorescence at 440 nm when the excitation wavelength is selected at 275 nm. The absorbance and fluorescence of the FA-AgNPs could reflect the concentration of the Hg(2+) ions. Thus, we developed a simple, sensitive analytical method to detect Hg(2+) based on the colorimetric and fluorescence enhancement of FA-AgNPs. The sensor exhibits two linear response ranges between absorbance and fluorescence intensity with Hg(2+) concentration, respectively. Meanwhile, a detection limit of 1 nM is estimated based on the linear relationship between responses with a concentration of Hg(2+). The high specificity of Hg(2+) with FA-AgNPs interactions provided the excellent selectivity towards detecting Hg(2+) over other metal ions (Pb(2+), Mg(2+), Zn(2+), Ni(2+), Cu(2+), Co(2+), Ca(2+), Mn(2+), Fe(2+), Cd(2+), Ba(2+), Cr(6+) and Cr(3+)). This will provide a simple, effective and multifunctional colorimetric and fluorescent sensor for on-site and real-time Hg(2+) ion detection. The proposed method can be applied to the analysis of trace Hg(2+) in lake water. Additionally, the FA-AgNPs can be used as efficient catalyst for the reduction of 4-nitrophenol and potassium hexacyanoferrate (III). PMID:25116278

Su, Dongyue; Yang, Xin; Xia, Qingdong; Zhang, Qi; Chai, Fang; Wang, Chungang; Qu, Fengyu

2014-09-01

103

Folic acid functionalized silver nanoparticles with sensitivity and selectivity colorimetric and fluorescent detection for Hg2+ and efficient catalysis  

NASA Astrophysics Data System (ADS)

In this research, folic acid functionalized silver nanoparticles (FA-AgNPs) were selected as a colorimetric and a ‘turn on’ fluorescent sensor for detecting Hg2+. After being added into Hg2+, AgNPs can emit stable fluorescence at 440 nm when the excitation wavelength is selected at 275 nm. The absorbance and fluorescence of the FA-AgNPs could reflect the concentration of the Hg2+ ions. Thus, we developed a simple, sensitive analytical method to detect Hg2+ based on the colorimetric and fluorescence enhancement of FA-AgNPs. The sensor exhibits two linear response ranges between absorbance and fluorescence intensity with Hg2+ concentration, respectively. Meanwhile, a detection limit of 1 nM is estimated based on the linear relationship between responses with a concentration of Hg2+. The high specificity of Hg2+ with FA-AgNPs interactions provided the excellent selectivity towards detecting Hg2+ over other metal ions (Pb2+, Mg2+, Zn2+, Ni2+, Cu2+, Co2+, Ca2+, Mn2+, Fe2+, Cd2+, Ba2+, Cr6+ and Cr3+). This will provide a simple, effective and multifunctional colorimetric and fluorescent sensor for on-site and real-time Hg2+ ion detection. The proposed method can be applied to the analysis of trace Hg2+ in lake water. Additionally, the FA-AgNPs can be used as efficient catalyst for the reduction of 4-nitrophenol and potassium hexacyanoferrate (III).

Su, Dongyue; Yang, Xin; Xia, Qingdong; Zhang, Qi; Chai, Fang; Wang, Chungang; Qu, Fengyu

2014-09-01

104

Ultrasensitive label-free amplified colorimetric detection of p53 based on G-quadruplex MBzymes.  

PubMed

A novel label-free DNAzyme molecular beacon (MBzyme) strategy was for the first time developed for colorimetric amplification detection of target nucleic acids. The MBzyme, which is designed to contain peroxidase-mimicking DNAzyme that is locked by a common hairpin, was engineered to form a catalytically active MBzyme through hybridizing with the target p53 DNA. The MBzyme is a multifunctional label-free probe that can act as the target recognition element, catalytic DNAzyme and the primer of polymerization. The target p53 DNA hybridization can induce the isothermal circular strand-displacement polymerization even without any chemical modification and other DNA sequences. This unique amplifying strategy leads to the generation of multiple numbers of active MBzyme molecules even if one hybridization event occurs, achieving a dynamic range of seven orders of magnitude and giving a detection limit down to 25 fM which is 3-5 orders of magnitude lower than those of related literature reports. These achievements might be helpful in the design of highly efficient enhancers for G-quadruplex-hemin DNAzymes to be applied on the fundamental research, biotechnology, and biomedical diagnosis. PMID:23850786

Li, Hongbo; Wu, Zaisheng; Qiu, Liping; Liu, Jinwen; Wang, Cui; Shen, Guoli; Yu, Ruqin

2013-12-15

105

Colorimetric detection of DNA damage by using hemin-graphene nanocomposites  

NASA Astrophysics Data System (ADS)

A colorimetric method for detection of DNA damage was developed by using hemin-graphene nanosheets (H-GNs). H-GNs were skillfully synthesized by adsorping of hemin on graphene through ?-? interactions. The as-prepared H-GNs possessed both the ability of graphene to differentiate the damage DNA from intact DNA and the catalytic action of hemin. The damaged DNA made H-GNs coagulated to different degrees from the intact DNA because there were different amount of negative charge exposed on their surface, which made a great impact on the solubility of H-GNs. As a result, the corresponding centrifugal supernatant of H-GNs solution showed different color in the presence of 3,3',5,5'-tetramethylbenzidine (TMB) and H2O2, which could be discriminated by naked eyes or by ultraviolet (UV)-visible spectrometer. Based on this, the damaged effects of styrene oxide (SO), NaAsO2 and UV radiation on DNA were studied. Results showed that SO exerted most serious damage effect on DNA although all of them damaged DNA seriously. The new method for detection of DNA damage showed good prospect in the evaluation of genotoxicity of new compounds, the maximum limit of pesticide residue, food additives, and so on, which is important in the fields of food science, pharmaceutical science and pesticide science.

Wei, W.; Zhang, D. M.; Yin, L. H.; Pu, Y. P.; Liu, S. Q.

2013-04-01

106

Colorimetric detection of Hg2+ ions in aqueous media using CA-Au NPs  

NASA Astrophysics Data System (ADS)

Based on the selective interaction between Hg2+ ions and cyanuric acid (CA) and the anti-aggregation of CA stabilized gold nanoparticles (CA-Au NPs), a simple colorimetric method was developed for detecting Hg2+ ions. In a medium of pH 7.4 tris-HCl buffer containing 8 × 10-3 M NaCl, the CA-Au NPs solution was red, which was due to CA adsorbed onto the surface of Au NPs, stabilizing Au NPs against aggregation. When CA-HgII-CA complex was formed in the presence of Hg2+, the stability of CA-Au NPs reduced, and then aggregation of Au NPs occurred. Consequently, the color of the solution changed from red to blue and could easily be measured with a common spectrophotometer. The aggregation of Au NPs was also validated using transmission electron microscopy (TEM). The controlled experiment showed that other ions including Ba2+, Ca2+, Zn2+, Cd2+, Co2+, Mn2+, Cu2+, Mg2+, and Ni2+ ions did not induce any distinct spectral changes, which constituted a Hg2+-selective sensor. A dynamic range of 1.6-16 × 10-6 M Hg2+ ions was observed at the optimized reaction condition. This method provides a potentially useful tool for Hg2+ detection.

Liu, Zening; Hu, Jiao; Tong, Sijia; Cao, Qihua; Yuan, Hong

2012-11-01

107

Simple and sensitive colorimetric detection of cysteine based on ssDNA-stabilized gold nanoparticles.  

PubMed

In this paper, we demonstrate a simple and sensitive colorimetric detection of cysteine based on the cysteine-mediated color change of ssDNA-stabilized gold nanoparticles (AuNPs). Cysteine is capable of absorbing onto AuNPs surfaces via the strong interaction between its thiol group and gold. ssDNA molecules which stabilize AuNPs against salt-induced aggregation are removed away by cysteine encapsulation on the AuNPs surfaces, resulting in a characteristic color change of AuNPs from red to blue as soon as salt is added. The ratio of absorptions at 640 to 525 nm (A(640)/A(525)) is linear dependent on the cysteine concentration in the range from 0.1 to 5 microM. Furthermore, amino acids other than cysteine cannot mediate the color change under the identical conditions due to the absence of thiol groups, suggesting the selectivity of the proposed method toward cysteine. The employment of complicated protocols and sophisticated processes such as the preparation of modified AuNPs are successfully avoided in design to realize the simple and low-cost cysteine detection; and the high sensitivity and low cost of the method is favorable for practical applications. PMID:19641904

Chen, Zhang; Luo, Shenglian; Liu, Chengbin; Cai, Qingyun

2009-09-01

108

Colorimetric sensor array allows fast detection and simultaneous identification of sepsis-causing bacteria in spiked blood culture.  

PubMed

Sepsis is a medical emergency demanding early diagnosis and tailored antimicrobial therapy. Every hour of delay in initiating effective therapy measurably increases patient mortality. Blood culture is currently the reference standard for detecting bloodstream infection, a multistep process which may take one to several days. Here, we report a novel paradigm for earlier detection and the simultaneous identification of pathogens in spiked blood cultures by means of a metabolomic "fingerprint" of the volatile mixture outgassed by the organisms. The colorimetric sensor array provided significantly faster detection of positive blood cultures than a conventional blood culture system (12.1 h versus 14.9 h, P < 0.001) while allowing for the identification of 18 bacterial species with 91.9% overall accuracy within 2 h of growth detection. The colorimetric sensor array also allowed for discrimination between unrelated strains of methicillin-resistant Staphylococcus aureus, indicating that the metabolomic fingerprint has the potential to track nosocomial transmissions. Altogether, the colorimetric sensor array is a promising tool that offers a new paradigm for diagnosing bloodstream infections. PMID:24478493

Lim, Sung H; Mix, Samantha; Xu, Zeyu; Taba, Brian; Budvytiene, Indre; Berliner, Anders N; Queralto, Nuria; Churi, Yair S; Huang, Richard S; Eiden, Michael; Martino, Raymond A; Rhodes, Paul; Banaei, Niaz

2014-02-01

109

A portable lab-on-a-chip system for gold-nanoparticle-based colorimetric detection of metal ions in water.  

PubMed

Heavy metal ions released into various water systems have a severe impact on the environment and human beings, and excess exposure to toxic metal ions through drinking water poses high risks to human health and causes life-threatening diseases. Thus, there is high demand for the development of a rapid, low-cost, and sensitive method for detection of metal ions in water. We present a portable analytical system for colorimetric detection of lead (Pb(2+)) and aluminum (Al(3+)) ions in water based on gold nanoparticle probes and lab-on-a-chip instrumentation. The colorimetric detection of metal ions is conducted via single-step assays with low limits of detection (LODs) and high selectivity. We design a custom-made microwell plate and a handheld colorimetric reader for implementing the assays and quantifying the signal readout. The calibration experiments demonstrate that this portable system provides LODs of 30?ppb for Pb(2+) and 89?ppb for Al(3+), both comparable to bench-top analytical spectrometers. It promises an effective platform for metal ion analysis in a more economical and convenient way, which is particularly useful for water quality monitoring in field and resource-poor settings. PMID:25332734

Zhao, Chen; Zhong, Guowei; Kim, Da-Eun; Liu, Jinxia; Liu, Xinyu

2014-09-01

110

Colorimetric Sensor Array Allows Fast Detection and Simultaneous Identification of Sepsis-Causing Bacteria in Spiked Blood Culture  

PubMed Central

Sepsis is a medical emergency demanding early diagnosis and tailored antimicrobial therapy. Every hour of delay in initiating effective therapy measurably increases patient mortality. Blood culture is currently the reference standard for detecting bloodstream infection, a multistep process which may take one to several days. Here, we report a novel paradigm for earlier detection and the simultaneous identification of pathogens in spiked blood cultures by means of a metabolomic “fingerprint” of the volatile mixture outgassed by the organisms. The colorimetric sensor array provided significantly faster detection of positive blood cultures than a conventional blood culture system (12.1 h versus 14.9 h, P < 0.001) while allowing for the identification of 18 bacterial species with 91.9% overall accuracy within 2 h of growth detection. The colorimetric sensor array also allowed for discrimination between unrelated strains of methicillin-resistant Staphylococcus aureus, indicating that the metabolomic fingerprint has the potential to track nosocomial transmissions. Altogether, the colorimetric sensor array is a promising tool that offers a new paradigm for diagnosing bloodstream infections. PMID:24478493

Mix, Samantha; Xu, Zeyu; Taba, Brian; Budvytiene, Indre; Berliner, Anders N.; Queralto, Nuria; Churi, Yair S.; Huang, Richard S.; Eiden, Michael; Martino, Raymond A.; Rhodes, Paul

2014-01-01

111

Optimization of trichloroethylene oxidation by methanotrophs and the use of a colorimetric assay to detect soluble methane monooxygenase activity  

Microsoft Academic Search

Methylosinus trichosporium OB3b biosynthesizes a broad specificity soluble methane monooxygenase that rapidly oxidizes trichloroethylene (TCE). The selective expression of the soluble methane monooxygenase was followed in vivo by a rapid colorimetric assay. Naphthalene was oxidized by purified soluble methane monooxygenase or by cells grown in copper-deficient media to a mixture of 1-naphthol and 2-naphthol. The naphthols were detected by reaction

Gregory A. Brusseau; Hsien-Chyang Tsien; Richard S. Hanson; Lawrence P. Wackett

1990-01-01

112

Convenient, inexpensive quantification of elemental sulfur by simultaneous in situ reduction and colorimetric detection.  

PubMed

Rapid, inexpensive, and convenient methods for quantifying elemental sulfur (S(0)) with low or sub-?gg(-1) limits of detection would be useful for a range of applications where S(0) can act as a precursor for noxious off-aromas, e.g., S(0) in pesticide residues on winegrapes or as a contaminant in drywall. However, existing quantification methods rely on toxic reagents, expensive and cumbersome equipment, or demonstrate poor selectivity. We have developed and optimized an inexpensive, rapid method (?15 min per sample) for quantifying S(0) in complex matrices. Following dispersion of the sample in PEG-400 and buffering, S(0) is quantitatively reduced to H(2)S in situ by dithiothreitol and simultaneously quantified by commercially available colorimetric H(2)S detection tubes. By employing multiple tubes, the method demonstrated linearity from 0.03 to 100 ?g S(0) g(-1) for a 5 g sample (R(2)=0.994, mean CV=6.4%), and the methodological detection limit was 0.01 ?g S(0) g(-1). Interferences from sulfite or sulfate were not observed. Mean recovery of an S(0) containing sulfur fungicide in grape macerate was 84.7% with a mean CV of 10.4%. Mean recovery of S(0) in a colloidal sulfur preparation from a drywall matrix was 106.6% with a mean CV of 6.9%. Comparable methodological detection limits, sensitivity, and recoveries were achieved in grape juice, grape macerate and with 1g drywall samples, indicating that the methodology should be robust across a range of complex matrices. PMID:21843674

Kwasniewski, Misha T; Allison, Rachel B; Wilcox, Wayne F; Sacks, Gavin L

2011-10-01

113

The three-way junction DNAzyme based probe for label-free colorimetric detection of DNA.  

PubMed

A novel three-way junction DNAzyme based probe has been designed for the colorimetric sensing of target DNA. Specifically, a DNAzyme-linked hairpin DNA is used as a signal probe. In the presence of target DNA, the signal probe, assistant probe and target DNA can hybridize with each other, resulting in the formation of a three-way junction DNA. At the same time, the signal probe is opened and the DNAzyme sequence in the signal probe is dehybridized. Subsequently, in the presence of hemin, the DNAzyme sequence forms a G-quadruplex-hemin complex, which catalyzes oxidation of 2, 2'-azinobis (3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) by H(2)O(2) to the colored ABTS(.-)radical. The significant color changes can be distinguished visually. By the combination of the hairpin probe and the three-way junction DNA probe, the proposed sensor exhibits high recognition property for single-nucleotide polymorphisms (SNPs). This sensor allows the detection of target DNA at a concentration as low as 0.25 nmol L(-1). The proposed sensor is easy to fabricate, which avoids the tedious and expensive labeling procedures, and exhibits high selectivity against single-base mismatched DNA. PMID:23017688

Tang, Shurong; Tong, Ping; Li, Heng; Gu, Fang; Zhang, Lan

2013-03-15

114

A selectively rhodamine-based colorimetric probe for detecting copper(II) ion.  

PubMed

A novel rhodamine derivative 3-bromo-5-methylsalicylaldehyde rhodamine B hydrazone (BMSRH) has been synthesized by reacting rhodamine B hydrazide with 3-bromo-5-methylsalicylaldehyde and developed as a new colorimetric probe for the selective and sensitive detection of Cu2+. Addition of Cu2+ to the solution of BMSRH results in a rapid color change from colorless to red together with an obvious new band appeared at 552 nm in the UV-vis absorption spectra. This change is attributed to the spirocycle form of BMSRH opened via coordination with Cu2+ in a 1:1 stoichiometry and their association constant is determined as 3.2×10(4) L mol(-1). Experimental results indicate that the BMSRH can provide a rapid, selective and sensitive response to Cu2+ with a linear dynamic range 0.667-240 ?mol/L. Common interferent ions do not show any interference on the Cu2+ determination. It is anticipated that BMSRH can be a good candidate probe and has potential application for Cu2+ determination. The proposed probe exhibits the following advantages: a quick, simple and facile synthesis. PMID:24866085

Zhang, Jiangang; Zhang, Li; Wei, Yanli; Chao, Jianbing; Shuang, Shaomin; Cai, Zongwei; Dong, Chuan

2014-11-11

115

A selectively rhodamine-based colorimetric probe for detecting copper(II) ion  

NASA Astrophysics Data System (ADS)

A novel rhodamine derivative 3-bromo-5-methylsalicylaldehyde rhodamine B hydrazone (BMSRH) has been synthesized by reacting rhodamine B hydrazide with 3-bromo-5-methylsalicylaldehyde and developed as a new colorimetric probe for the selective and sensitive detection of Cu2+. Addition of Cu2+ to the solution of BMSRH results in a rapid color change from colorless to red together with an obvious new band appeared at 552 nm in the UV-vis absorption spectra. This change is attributed to the spirocycle form of BMSRH opened via coordination with Cu2+ in a 1:1 stoichiometry and their association constant is determined as 3.2 × 104 L mol-1. Experimental results indicate that the BMSRH can provide a rapid, selective and sensitive response to Cu2+ with a linear dynamic range 0.667-240 ?mol/L. Common interferent ions do not show any interference on the Cu2+ determination. It is anticipated that BMSRH can be a good candidate probe and has potential application for Cu2+ determination. The proposed probe exhibits the following advantages: a quick, simple and facile synthesis.

Zhang, Jiangang; Zhang, Li; Wei, Yanli; Chao, Jianbing; Shuang, Shaomin; Cai, Zongwei; Dong, Chuan

2014-11-01

116

Colorimetric Sensor for Label Free Detection of Porcine PCR Product (ID: 18)  

NASA Astrophysics Data System (ADS)

This report described the use of 40±5 nm in diameter citrate-coated gold nanoparticles (GNPs) as colorimetric sensor to visually detect the presence of a 17-base swine specific conserved sequence and nucleotide mismatch in the mixed PCR products of pig, deer and shad cytochrome b genes. The size of these PCR amplicons was 109 base-pair and was amplified with a pair of common primers. Colloidal GNPs changed color from pinkish- red to purple-gray in 2 mM PBS buffer by losing its characteristic surface plasmon resonance peak at 530 nm and gaining new features between 620 and 800 nm in the absorption spectrum indicating strong aggregation. The particles were stabilized against salt induced aggregation, retained spectral features and characteristic color upon adsorption of single-stranded DNA. The PCR products without any additional processing were hybridized with a 17-nucleotide swine probe prior to exposure to GNPs. At a critical annealing temperature (55° C) that differentiated between the match and mismatch pairing, the probe was hybridized with the pig PCR product and dehybridized from the deer's and shad's. The interaction of dehybridized probe to GNPs prevented them from salt-induced aggregation, retaining their characteristic red color. The assay did not need any surface modification chemistry or labeling steps. The results were determined visually and validated by absorption spectroscopy. The entire assay (hybridization plus visual detection) was performed in less than 10 min. The assay obviated the need of complex RFLP, sequencing or blotting to differentiate the same size PCR products. We find the application of the assay for species assignment in food analysis, mismatch detection in genetic screening and homology study among closely related species.

Ali, M. E.; Hashim, U.; Bari, M. F.; Dhahi, Th. S.

2011-05-01

117

A colorimetric aptamer biosensor based on cationic polymer and gold nanoparticles for the ultrasensitive detection of thrombin.  

PubMed

A colorimetric assay for the ultrasensitive determination of thrombin based on cationic polymer and gold nanoparticles was presented, in which unmodified gold nanoparticles (AuNPs) was used as probes and 21-mer thrombin-binding aptamer (TBA) as sensing elements. Upon the addition of thrombin, TBA interacted specifically with thrombin to form a G-quadruplex structure. As a result, the conformation change facilitated the cationic polymer, poly(diallyldimethylammonium chloride) (PDDA)-induced AuNP aggregation. Thus, the visible change in color from wine-red to blue-purple was readily seen by the naked eye. The colorimetric sensor could detect thrombin down to 1 pM with high selectivity in the presence of other interferring proteins. Furthermore, the assay was successfully employed to determine thrombin in human serum sample, which suggested its great potential for diagnostic purposes. PMID:24463195

Chen, Zhengbo; Tan, Yuan; Zhang, Chenmeng; Yin, Lu; Ma, He; Ye, Nengsheng; Qiang, Hong; Lin, Yuqing

2014-06-15

118

Dual-channel detection of Cu2+ and F- with a simple Schiff-based colorimetric and fluorescent sensor  

NASA Astrophysics Data System (ADS)

A simple and easily synthesized colorimetric and fluorescent receptor 1, based on 4-diethylaminosalicylaldehyde moieties as a binding and signaling unit, has been synthesized and characterized. The receptor 1 has a selective colorimetric sensing ability for copper (II) ion by changing color from colorless to yellow in aqueous solution, and could be utilized to monitor Cu(II) over a wide pH range of 4-11. In addition, the detection limit (12 ?M) of 1 for Cu2+ is much lower than that (30 ?M) recommended by WHO in drinking water, and its copper complex could be reversible simply through treatment with a proper reagent such as EDTA. Moreover, receptor 1 exhibited both a color change from colorless to yellow and fluorescence enhancement with a red shift upon addition to F- in DMSO. The recognition mechanism was attributed to the intermolecular proton transfer between the hydroxyl group of the receptor and the fluoride.

Na, Yu Jeong; Choi, Ye Won; Yun, Jin Yeong; Park, Kyung-Min; Chang, Pahn-Shick; Kim, Cheal

2015-02-01

119

Label-free detection of specific DNA sequence-telomere using unmodified gold nanoparticles as colorimetric probes  

NASA Astrophysics Data System (ADS)

A simple and sensitive label-free colorimetric detection of telomere DNA has been developed. It was based on the color change of gold nanoparticles (AuNPs) due to DNA hybridization. UV-vis spectra and transmission electron microscopy (TEM) were used to investigate the change of AuNPs. Under the optimized conditions, the linear range for determination of telomere DNA was 5.7 × 10 -13 to 4.5 × 10 -6 mol/L. The detection limit (3 ?) of this method has decreased to pico-molar level.

Qi, Yingying; Li, Li; Li, Baoxin

2009-09-01

120

Simple, field portable colorimetric detection device for organic peroxides and hydrogen peroxide  

DOEpatents

A simple and effective system for the colorimetric determination of organic peroxides and hydrogen peroxide. A peroxide pen utilizing a swipe material attached to a polyethylene tube contains two crushable vials. The two crushable vials contain a colorimetric reagent separated into dry ingredients and liquid ingredients. After swiping a suspected substance or surface the vials are broken, the reagent is mixed thoroughly and the reagent is allowed to wick into the swipe material. The presence of organic peroxides or hydrogen peroxide is confirmed by a deep blue color.

Pagoria, Philip F. (Livermore, CA); Mitchell, Alexander R. (Livermore, CA); Whipple, Richard E. (Livermore, CA); Carman, M. Leslie (San Ramon, CA); Reynolds, John G. (San Ramon, CA); Nunes, Peter (Livermore, CA); Shields, Sharon J. (San Ramon, CA)

2010-11-09

121

Luminol functionalized gold nanoparticles as colorimetric and chemiluminescent probes for visual, label free, highly sensitive and selective detection of minocycline  

NASA Astrophysics Data System (ADS)

In this work, luminol functionalized gold nanoparticles (LuAuNPs) were used as colorimetric and chemiluminescent probes for visual, label free, sensitive and selective detection of minocycline (MC). The LuAuNPs were prepared by simple one-pot reduction of HAuCl4 with luminol, which exhibited a good chemiluminescence (CL) activity owing to the presence of luminol molecules on their surface and surface plasmon resonance absorption. In the absence of MC, the color of LuAuNPs was wine red and their size was relatively small (?25 nm), which could react with silver nitrate, producing a strong CL emission. Upon the addition of MC at acidic buffer solutions, the electrostatic interaction between positively charged MC and negatively charged LuAuNPs caused the aggregation of LuAuNPs, generating a purple or blue color. Simultaneously, the aggregated LuAuNPs did not effectively react with silver nitrate, producing a weak CL emission. The signal change was linearly dependent on the logarithm of MC concentration in the range from 30 ng to 1.0 ?g for colorimetric detection and from 10 ng to 1.0 ?g for CL detection. With colorimetry, a detection limit of 22 ng was achieved, while the detection limit for CL detection modality was 9.7 ng.

He, Yi; Peng, Rufang

2014-11-01

122

Luminol functionalized gold nanoparticles as colorimetric and chemiluminescent probes for visual, label free, highly sensitive and selective detection of minocycline.  

PubMed

In this work, luminol functionalized gold nanoparticles (LuAuNPs) were used as colorimetric and chemiluminescent probes for visual, label free, sensitive and selective detection of minocycline (MC). The LuAuNPs were prepared by simple one-pot reduction of HAuCl? with luminol, which exhibited a good chemiluminescence (CL) activity owing to the presence of luminol molecules on their surface and surface plasmon resonance absorption. In the absence of MC, the color of LuAuNPs was wine red and their size was relatively small (?25 nm), which could react with silver nitrate, producing a strong CL emission. Upon the addition of MC at acidic buffer solutions, the electrostatic interaction between positively charged MC and negatively charged LuAuNPs caused the aggregation of LuAuNPs, generating a purple or blue color. Simultaneously, the aggregated LuAuNPs did not effectively react with silver nitrate, producing a weak CL emission. The signal change was linearly dependent on the logarithm of MC concentration in the range from 30 ng to 1.0 ?g for colorimetric detection and from 10 ng to 1.0 ?g for CL detection. With colorimetry, a detection limit of 22 ng was achieved, while the detection limit for CL detection modality was 9.7 ng. PMID:25327146

He, Yi; Peng, Rufang

2014-11-14

123

Synthetic multivalent DNAzymes for enhanced hydrogen peroxide catalysis and sensitive colorimetric glucose detection.  

PubMed

A peroxidase-mimic DNAzyme is a G-quadruplex (G4) DNA-hemin complex, in which the G4-DNA resembles an apoenzyme, and hemin is the cofactor for hydrogen peroxide (H2O2) catalysis. Twenty-one-mer CatG4 is a well-proven G4-DNA as well as a hemin-binding aptamer for constituting a DNAzyme. This work studied if a multivalent DNAzyme with accelerated catalysis could be constructed using a multimeric CatG4 with hemin. We compared CatG4 monomer, dimer, trimer, and tetramer, which were prepared by custom oligo synthesis, for G4 structure formation. According to circular dichroism (CD) analysis, we found that a CatG4 multimer exhibited more active G4 conformation than the sum effect of equal-number CatG4 monomers. However, the DNAzyme kinetics was not improved monotonically along with the subunit number of a multimeric CatG4. It was the trivalent DNAzyme, trimeric CatG4:hemin, resulting in the rapidest H2O2 catalysis instead of a tetravalent one. We discovered that the trivalent DNAzyme's highest catalytic rate was correlated to its most stable hemin-binding G4 structure, evidenced by CD melting temperature analysis. Finally, a trivalent DNAzyme-based colorimetric glucose assay with a detection limit as low as 10?M was demonstrated, and this assay did not need adenosine 5'-tri-phosphate disodium salt hydrate (ATP) as a DNAzyme boosting agent. PMID:25542363

Yang, Deng-Kai; Kuo, Chia-Jung; Chen, Lin-Chi

2015-01-26

124

Multiplexed Colorimetric Solid-Phase Extraction  

NASA Technical Reports Server (NTRS)

Multiplexed colorimetric solid-phase extraction (MC-SPE) is an extension of colorimetric solid-phase extraction (C-SPE) an analytical platform that combines colorimetric reagents, solid phase extraction, and diffuse reflectance spectroscopy to quantify trace analytes in water. In CSPE, analytes are extracted and complexed on the surface of an extraction membrane impregnated with a colorimetric reagent. The analytes are then quantified directly on the membrane surface using a handheld diffuse reflectance spectrophotometer. Importantly, the use of solid-phase extraction membranes as the matrix for impregnation of the colorimetric reagents creates a concentration factor that enables the detection of low concentrations of analytes in small sample volumes. In extending C-SPE to a multiplexed format, a filter holder that incorporates discrete analysis channels and a jig that facilitates the concurrent operation of multiple sample syringes have been designed, enabling the simultaneous determination of multiple analytes. Separate, single analyte membranes, placed in a readout cartridge create unique, analyte-specific addresses at the exit of each channel. Following sample exposure, the diffuse reflectance spectrum of each address is collected serially and the Kubelka-Munk function is used to quantify each water quality parameter via calibration curves. In a demonstration, MC-SPE was used to measure the pH of a sample and quantitate Ag(I) and Ni(II).

Gazda, Daniel B.; Fritz, James S.; Porter, Marc D.

2009-01-01

125

Potassium sorbate residue levels and persistence in citrus fruit as detected by a simple colorimetric method  

Technology Transfer Automated Retrieval System (TEKTRAN)

Postharvest applications of potassium sorbate (PS) to fresh citrus fruit control fungal decay pathogens, such as Penicillium digitatum, cause of green mold. Although PS effectiveness has been examined repeatedly, little is known about PS residues. A colorimetric method that employed extraction of th...

126

A simple colorimetric device for rapid detection of Hg2+ in water.  

PubMed

A 'turn-on' fluorescent colorimetric device for Hg(2+) sensing was built using a dual light-emitting diode system. Fluorescence generated from a rhodamine derivative (RHD), an indicator for Hg(2+) sensing, was combined with a background red light, and the complex light was captured by a commercial charge coupled device camera or by the naked eye. PMID:22854713

Ye, Tingxiu; He, Chunyan; Qu, Yanqin; Deng, Zhuo; Jiang, Yaqi; Li, Meijin; Chen, Xi

2012-09-21

127

Direct colorimetric diagnosis of pathogen infections by utilizing thiol-labeled PCR primers and unmodified gold nanoparticles.  

PubMed

We describe here a greatly simplified colorimetric detection method to identify PCR-amplified nucleic acids. Our method relies on the PCR product having thiol group at one end, which is generated by employing thiolated PCR primer. After PCR amplification reaction, unmodified gold nanoparticles (AuNPs) are added into the reaction tube followed by the addition of NaCl to induce the aggregation of AuNPs. The PCR products strongly bind to the surface of AuNPs through the interaction of the terminal thiol groups and the long chain of DNA which has abundant negative charges enhances the electrostatic and steric repulsion among AuNPs, which consequently leads to the prevention of the salt-induced aggregation. As a result, the color of AuNPs remains red in the presence of the PCR-amplified nucleic acids, while the AuNPs change its color from red to blue due to the salt-induced aggregation in the absence of the PCR products. This simple but very efficient colorimetric strategy was successfully demonstrated by diagnosing Chlamydia infection using a real human urine sample. Since the results can be clearly seen with the naked eye without any complicated step such as surface modification of AuNPs or PCR product purification, this method can be easily applied to point-of-care diagnosis. PMID:20138499

Jung, Ye Lim; Jung, Cheulhee; Parab, Harshala; Li, Taihua; Park, Hyun Gyu

2010-04-15

128

Colorimetric detection of Cd2+ using gold nanoparticles cofunctionalized with 6-mercaptonicotinic acid and L-cysteine.  

PubMed

We have developed a colorimetric assay for the highly sensitive and selective detection of Cd(2+) using gold nanoparticles (AuNPs) cofunctionalized with 6-mercaptonicotinic acid (MNA) and L-Cysteine (L-Cys) through the formation of an Au-S bond. In the presence of Cd(2+), the aggregation of functionalized AuNPs occurred by means of a metal-ligand interaction that led to visible color changes. Most importantly, cofunctionalized AuNPs had better responses for Cd(2+) than that functionalized by either MNA or L-Cys. Cd(2+) could be detected by the colorimetric response of AuNPs that could be detected by the naked eye or a UV-vis spectrophotometer. The absorbance ratio (A(620)/A(523)) was linear with the Cd(2+) concentration in the range of 2.0 × 10(-7) to 1.7 × 10(-6) M. Under optimum conditions (2.0 × 10(-5) M MNA, 2.0 × 10(-6) M L-Cys and 0.020 M NaCl at pH 10.0), the detection limit (3?) of Cd(2+) could be as low as 1.0 × 10(-7) M. Interference experiments showed that Pb(2+) and Cu(2+) caused a slight interference for Cd(2+) determination while other metal ions caused no interference. The proposed method was successfully applied to determine the concentration of Cd(2+) in environmental samples (lake water). PMID:21804959

Xue, Ying; Zhao, Hong; Wu, Zhijiao; Li, Xiangjun; He, Yujian; Yuan, Zhuobin

2011-09-21

129

G-Quadruplex-based DNAzyme for colorimetric detection of cocaine: using magnetic nanoparticles as the separation and amplification element.  

PubMed

The appearance of the aptamer provides good recognition elements for small molecules, especially for drugs. In this work, by combining the advantages of magnetic nanoparticles (MNPs) with colorimetric drug detection using hemin-G-quadruplex complex as the sensing element, we report a simple and sensitive DNAzyme-based colorimetric sensor for cocaine detection in a 3,3,5,5-tetramethylbenzidine sulfate (TMB)-H(2)O(2) reaction system. The whole experimental processes are simplified. Cocaine aptamer fragments, SH-C2, are covalently labeled onto the amine-functionalized MNPs. When the target cocaine and another cocaine aptamer fragments (C1) grafted with G-riched strand AG4 (i.e. C1-AG4) are present simultaneously, the C2 layer on MNPs hybridizes partly with C1-AG4 to bind the cocaine. The C1-AG4 can be combinded with hemin to form DNAzyme which can effectively catalyze the H(2)O(2)-mediated oxidation of TMB, giving rise to a change in solution color. Importantly, using MNPs as the separation and amplification elements could effectively reduce the background signal and the interference from the real samples. A linear response from 0.1 ?M to 20 ?M is obtained for cocaine and a detection limit of 50 nM is achieved, which provides high sensitivity and selectivity to detect cocaine. PMID:21079882

Du, Yan; Li, Bingling; Guo, Shaojun; Zhou, Zhixue; Zhou, Ming; Wang, Erkang; Dong, Shaojun

2011-02-01

130

Label-free and ultrasensitive colorimetric detection of DNA based on target-triggered quadratic amplification strategy.  

PubMed

Highly sensitive detection of DNA plays a crucial role in biomedical research and clinical diagnosis. Herein, we developed a simple, label-free, isothermal, and ultrasensitive colorimetric method for amplified detection of DNA on the basis of a new quadratic amplification strategy. With the presence of three ingeniously designed hairpin structures and Exonuclease III (Exo III), the target DNA can trigger two independent cycles of reactions: hairpin assembly reaction and Exo III cleavage reaction, which are designed to initiate target DNA recycling amplification and reporter DNA amplification, respectively. Therefore, the proposed method exhibits a high sensitivity toward target DNA with a detection limit of as low as 81 fM, and it can discriminate mismatched DNA from completely matched target DNA. Furthermore, this method could be used as a universal tool for the detection of various DNA sequences and might be further extended for the detection of aptamer-binding molecules. PMID:25437364

Wu, Hao; Liu, Yaling; Wang, Hongyong; Wu, Jun; Zhu, Feifan; Zou, Pei

2015-04-15

131

Study on a colorimetric sensor with color switching: Naked-eye detection for Cu(II) ion  

NASA Astrophysics Data System (ADS)

In this paper, we synthesize and report a Cu(II)-sensing probe of N'1,N'2-bis(4-(diethylamino)-2-hydroxybenzylidene)oxalohydrazide (BDHO) with two detection channels. Its colorimetric and fluorescence spectrophotometric responses towards Cu(II) ion are fully investigated. It is found that the absorption and emission spectra of BDHO are both sensitive towards Cu(II) ion with high sensitivity as well as excellent selectivity. In addition, the recognition of BDHO towards Cu(II) ion is also very quick and can be accomplished within less than 1 min. The actual sensing performance of BDHO towards Cu(II) ion is also tentatively explored.

Gao, Yang; Ma, Wenzhong

2012-12-01

132

Use of Colorimetric Culture Methods for Detection of Mycobacterium tuberculosis Complex Isolates from Sputum Samples in Resource-Limited Settings  

PubMed Central

Despite recent advances, tuberculosis (TB) diagnosis remains imperfect in resource-limited settings due to its complexity and costs, poor sensitivity of available tests, or long times to reporting. We present a report on the use of colorimetric methods, based on the detection of mycobacterial growth using colorimetric indicators, for the detection of Mycobacterium tuberculosis in sputum specimens. We evaluated the nitrate reductase assay (NRA), a modified NRA using para-nitrobenzoic acid (PNB) (NRAp), and the resazurin tube assay using PNB (RETAp) to differentiate tuberculous and nontuberculous mycobacteria. The performances were assessed at days 18 and 28 using mycobacterium growth indicator tube (MGIT) and Löwenstein-Jensen (LJ) medium culture methods as the reference standards. We enrolled 690 adults with suspected pulmonary tuberculosis from a regional referral hospital in Uganda between March 2010 and June 2011. At day 18, the sensitivities and specificities were 84.6% and 90.0% for the NRA, 84.1% and 92.6% for the NRAp, and 71.2% and 99.3% for the RETAp, respectively. At day 28, the sensitivity of the RETAp increased to 82.6%. Among smear-negative patients with suspected TB, sensitivities at day 28 were 64.7% for the NRA, 61.3% for the NRAp, and 50% for the RETAp. Contamination rates were found to be 5.4% for the NRA and 6.7% for the RETAp, compared with 22.1% for LJ medium culture and 20.4% for MGIT culture. The median times to positivity were 10, 7, and 25 days for colorimetric methods, MGIT culture, and LJ medium culture,respectively. Whereas the low specificity of the NRA/NRAp precludes it from being used for TB diagnosis, the RETAp might provide an alternative to LJ medium culture to decrease the time to culture results in resource-poor settings. PMID:23658270

Orikiriza, Patrick; Rojas-Ponce, Gabriel; Riera-Montes, Margarita; Atwine, Daniel; Nansumba, Margaret; Bazira, Joel; Tuyakira, Eleanor; De Beaudrap, Pierre; Bonnet, Maryline; Page, Anne-Laure

2013-01-01

133

Colorimetric detection of mercury ion based on unmodified gold nanoparticles and target-triggered hybridization chain reaction amplification  

NASA Astrophysics Data System (ADS)

A novel unmodified gold nanoparticles (AuNPs)-based colorimetric strategy for label-free, specific and sensitive mercury ion (Hg2+) detection was demonstrated by using thymine-Hg2+-thymine (T-Hg2+-T) recognition mechanism and hybridization chain reaction (HCR) amplification strategy. In this protocol, a structure-switching probe (H0) was designed to recognize Hg2+ and then propagated a chain reaction of hybridization events between two other hairpin probes (H1 and H2). In the absence of Hg2+, all hairpin probes could stably coexist in solution, the exposed sticky ends of hairpin probes were capable of stabilizing AuNPs. As a result, salt-induced AuNPs aggregation could be effectively prevented. In the presence of Hg2+, thymine bases of H0 could specifically interact with Hg2+ to form stable T-Hg2+-T complex. Consequently, the hairpin structure of H0 probe was changed. As H1/H2 probes were added, the HCR process could be triggered and nicked double-helixes were formed. Since it was difficult for the formed nicked double-helixes to inhibit salt-induced AuNPs aggregation, a red-to-blue color change was observed in the colloid solution as the salt concentration increased. With the elegant amplification effect of HCR, a detection limit of around 30 nM was achieved (S/N = 3), which was about 1-2 orders of magnitudes lower than that of previous unmodified AuNPs-based colorimetric methods. By using the T-Hg2+-T recognition mechanism, high selectivity was also obtained. As an unmodified AuNPs-based colorimetric strategy, the system was simple in design, convenient in operation, and eliminated the requirements of separation processes, chemical modifications, and sophisticated instrumentations.

Wang, Qing; Yang, Xiaohan; Yang, Xiaohai; Liu, Pei; Wang, Kemin; Huang, Jin; Liu, Jianbo; Song, Chunxia; Wang, Jingjing

2015-02-01

134

A novel colorimetric method for the detection of Escherichia coli using cytochrome c peroxidase-encoding bacteriophage.  

PubMed

A new rapid and simple method was developed for the detection of Escherichia coli by constructing a recombinant T4 phage carrying the cytochrome c peroxidase gene derived from Saccharomyces cerevisiae (T4ccp) using which, the colorimetric detection of E. coli K12 was examined. The oxidation activity toward the chromogenic substrate cytochrome c was demonstrated by the cytochrome c peroxidase (CCP) produced from the T4ccp genome. The color change caused by the oxidation of the substrate could be visually perceived. The possibility of interference in the detection by the coexistence of other bacteria was assessed using Pseudomonas aeruginosa as a nontarget bacterium, and it was confirmed that the coexistence of P. aeruginosa caused no interference in the detection of E. coli K12. PMID:24417350

Hoang, Hoang A; Abe, Michiharu; Nakasaki, Kiyohiko

2014-03-01

135

Gold nanoparticles for the colorimetric and fluorescent detection of ions and small organic molecules  

NASA Astrophysics Data System (ADS)

In recent years, gold nanoparticles (AuNPs) have drawn considerable research attention in the fields of catalysis, drug delivery, imaging, diagnostics, therapy and biosensors due to their unique optical and electronic properties. In this review, we summarized recent advances in the development of AuNP-based colorimetric and fluorescent assays for ions including cations (such as Hg2+, Cu2+, Pb2+, As3+, Ca2+, Al3+, etc) and anions (such as NO2-, CN-, PF6-, F-, I-, oxoanions), and small organic molecules (such as cysteine, homocysteine, trinitrotoluene, melamine and cocaine, ATP, glucose, dopamine and so forth). Many of these species adversely affect human health and the environment. Moreover, we paid particular attention to AuNP-based colorimetric and fluorescent assays in practical applications.

Liu, Dingbin; Wang, Zhuo; Jiang, Xingyu

2011-04-01

136

A colorimetric method for highly sensitive and accurate detection of iodide by finding the critical color in a color change process using silver triangular nanoplates.  

PubMed

In this contribution, we demonstrated a novel colorimetric method for highly sensitive and accurate detection of iodide using citrate-stabilized silver triangular nanoplates (silver TNPs). Very lower concentration of iodide can induce an appreciable color change of silver TNPs solution from blue to yellow by fusing of silver TNPs to nanoparticles, as confirmed by UV-vis absorption spectroscopy and transmission electron microscopy (TEM). The principle of this colorimetric assay is not an ordinary colorimetry, but a new colorimetric strategy by finding the critical color in a color change process. With this strategy, 0.1 ?M of iodide can be recognized within 30 min by naked-eyes observation, and lower concentration of iodide down to 8.8 nM can be detected using a spectrophotometer. Furthermore, this high sensitive colorimetric assay has good accuracy, stability and reproducibility comparing with other ordinary colorimetry. We believe this new colorimetric method will open up a fresh insight of simple, rapid and reliable detection of iodide and can find its future application in the biochemical analysis or clinical diagnosis. PMID:24070486

Yang, Xiu-Hua; Ling, Jian; Peng, Jun; Cao, Qiu-E; Ding, Zhong-Tao; Bian, Long-Chun

2013-10-10

137

Highly sensitive detection of CpG methylation in genomic DNA by AuNP-based colorimetric assay with ligase chain reaction.  

PubMed

We have developed a new ligase chain reaction-based colorimetric assay for detection of DNA methylation with ultrahigh sensitivity and selectivity. Using the proposed assay, as low as 0.01 fM methylated DNA can be detected by visualization of color changes of gold nanoparticles with the naked eye. PMID:25621431

Su, Fengxia; Wang, Limei; Sun, Yueying; Liu, Chenghui; Duan, Xinrui; Li, Zhengping

2015-02-10

138

Continuous colorimetric screening assay for detection of d-amino acid aminotransferase mutants displaying altered substrate specificity.  

PubMed

D-Amino acid aminotransferase (DAAT) catalyzes the synthesis of numerous d-amino acids, making it an attractive biocatalyst for the production of enantiopure d-amino acids. To bolster its biocatalytic applicability, improved variants displaying increased activity toward non-native substrates are desired. Here, we report the development of a high-throughput, colorimetric, continuous coupled enzyme assay for the screening of DAAT mutant libraries that is based on the use of d-amino acid oxidase (DAAO). In this assay, the d-amino acid product of DAAT is oxidized by DAAO with concomitant release of hydrogen peroxide, which is detected colorimetrically by the addition of horseradish peroxidase and o-dianisidine. Using this assay, we measured apparent KM and kcat values for DAAT and identified mutants displaying altered substrate specificity via the screening of cell lysates in 96-well plates. The DAAO coupled assay is sensitive in that it allowed the detection of a DAAT mutant displaying an approximately 2000-fold decrease in kcat/KM relative to wild type. In addition, the DAAO assay enabled the identification of two DAAT mutants (V33Y and V33G) that are more efficient than wild type at transaminating the non-native acceptor phenylpyruvate. We expect that this assay will be useful for the engineering of additional mutants displaying increased activity toward non-native substrates. PMID:24949900

Barber, Janet E B; Damry, Adam M; Calderini, Guido F; Walton, Curtis J W; Chica, Roberto A

2014-10-15

139

Enhanced Colorimetric Immunoassay Accompanying with Enzyme Cascade Amplification Strategy for Ultrasensitive Detection of Low-Abundance Protein  

PubMed Central

Methods based on enzyme labels have been developed for colorimetric immunoassays, but most involve poor sensitivity and are unsuitable for routine use. Herein, we design an enhanced colorimetric immunoassay for prostate-specific antigen (PSA) coupling with an enzyme-cascade-amplification strategy (ECAS-CIA). In the presence of target PSA, the labeled alkaline phosphatase on secondary antibody catalyzes the formation of palladium nanostructures, which catalyze 3,3?,5,5?-tetramethylbenzidine-H2O2 system to produce the colored products, thus resulting in the signal cascade amplification. Results indicated that the ECAS-CIA presents good responses toward PSA, and allows detection of PSA at a concentration as low as 0.05?ng mL?1. Intra- and inter-assay coefficients of variation are below 9.5% and 10.7%, respectively. Additionally, the methodology is validated for analysis of clinical serum specimens with consistent results obtained by PSA ELISA kit. Importantly, the ECAS-CIA opens a new horizon for protein diagnostics and biosecurity. PMID:24509941

Gao, Zhuangqiang; Hou, Li; Xu, Mingdi; Tang, Dianping

2014-01-01

140

Enhanced colorimetric immunoassay accompanying with enzyme cascade amplification strategy for ultrasensitive detection of low-abundance protein.  

PubMed

Methods based on enzyme labels have been developed for colorimetric immunoassays, but most involve poor sensitivity and are unsuitable for routine use. Herein, we design an enhanced colorimetric immunoassay for prostate-specific antigen (PSA) coupling with an enzyme-cascade-amplification strategy (ECAS-CIA). In the presence of target PSA, the labeled alkaline phosphatase on secondary antibody catalyzes the formation of palladium nanostructures, which catalyze 3,3',5,5'-tetramethylbenzidine-H2O2 system to produce the colored products, thus resulting in the signal cascade amplification. Results indicated that the ECAS-CIA presents good responses toward PSA, and allows detection of PSA at a concentration as low as 0.05?ng mL(-1). Intra- and inter-assay coefficients of variation are below 9.5% and 10.7%, respectively. Additionally, the methodology is validated for analysis of clinical serum specimens with consistent results obtained by PSA ELISA kit. Importantly, the ECAS-CIA opens a new horizon for protein diagnostics and biosecurity. PMID:24509941

Gao, Zhuangqiang; Hou, Li; Xu, Mingdi; Tang, Dianping

2014-01-01

141

A simple, label-free AuNPs-based colorimetric ultrasensitive detection of nerve agents and highly toxic organophosphate pesticide.  

PubMed

Here, a simple label-free colorimetric sensing method for organophosphate (OP) nerve agents and pesticide based on catalytic reaction of acetylcholine esterase (AChE) and the aggregation of lipoic acid (LA) capped AuNPs has been established, which is highly sensitive with a limit of detection (LOD) lowered to pM level. In this method, only the AChE hydrolysis product of acetylthiocholine (ATCh), i.e., cationic thiocholine (TCh) can induce the aggregation of LA capped AuNPs along with a distinct color change from red to steel-blue. When OPs as enzyme inhibitors exist, the generation of TCh can be suppressed and the color change of LA capped AuNPs is gradually diminished according to different concentrations of OPs. The feasibility of this method has been demonstrated by sensitive measurement of OP nerve agents and pesticide in a spiked fruit sample with reliable results. This distinct and rapid colorimetric response enables us to readily probe OPs without more technical demand. PMID:21803563

Sun, Jiefang; Guo, Lei; Bao, Yi; Xie, Jianwei

2011-10-15

142

Architecture based on the integration of intermolecular G-quadruplex structure with sticky-end pairing and colorimetric detection of DNA hybridization  

NASA Astrophysics Data System (ADS)

An interesting discovery is reported in that G-rich hairpin-based recognition probes can self-assemble into a nano-architecture based on the integration of an intermolecular G-quadruplex structure with the sticky-end pairing effect in the presence of target DNAs. Moreover, GNPs modified with partly complementary DNAs can intensively aggregate by hybridization-based intercalation between intermolecular G-quadruplexes, indicating an inspiring assembly mechanism and a powerful colorimetric DNA detection. The proposed intermolecular G-quadruplex-integrated sticky-end pairing assembly (called GISA)-based colorimetric system allows a specific and quantitative assay of p53 DNA with a linear range of more than two orders of magnitude and a detection limit of 0.2 nM, suggesting a considerably improved analytical performance. And more to the point, the discrimination of single-base mismatched target DNAs can be easily conducted via visual observation. The successful development of the present colorimetric system, especially the GISA-based aggregation mechanism of GNPs is different from traditional approaches, and offers a critical insight into the dependence of the GNP aggregation on the structural properties of oligonucleotides, opening a good way to design colorimetric sensing probes and DNA nanostructure. An interesting discovery is reported in that G-rich hairpin-based recognition probes can self-assemble into a nano-architecture based on the integration of an intermolecular G-quadruplex structure with the sticky-end pairing effect in the presence of target DNAs. Moreover, GNPs modified with partly complementary DNAs can intensively aggregate by hybridization-based intercalation between intermolecular G-quadruplexes, indicating an inspiring assembly mechanism and a powerful colorimetric DNA detection. The proposed intermolecular G-quadruplex-integrated sticky-end pairing assembly (called GISA)-based colorimetric system allows a specific and quantitative assay of p53 DNA with a linear range of more than two orders of magnitude and a detection limit of 0.2 nM, suggesting a considerably improved analytical performance. And more to the point, the discrimination of single-base mismatched target DNAs can be easily conducted via visual observation. The successful development of the present colorimetric system, especially the GISA-based aggregation mechanism of GNPs is different from traditional approaches, and offers a critical insight into the dependence of the GNP aggregation on the structural properties of oligonucleotides, opening a good way to design colorimetric sensing probes and DNA nanostructure. Electronic supplementary information (ESI) available: Experimental section, supplementary Figures and perspectives. See DOI: 10.1039/c3nr03547f

Li, Hongbo; Wu, Zai-Sheng; Shen, Zhifa; Shen, Guoli; Yu, Ruqin

2014-01-01

143

Colorimetric detection of controlled assembly and disassembly of aptamers on unmodified gold nanoparticles.  

PubMed

Aptamers are nucleic acid ligands that are generated artificially by in vitro selection and behave similar to antibodies. The development of aptamer-based sensing systems or strategies has been in vogue for the past few decades, because aptamers are smaller in size, stable, cheaper and undergo easier modifications. Owing to these advantages, several facile aptamer-based colorimetric strategies have been created by controlling the assembly and disassembly of aptamers on unmodified gold nanoparticle probes. As these kinds of assay systems are rapid and can be visualized unaided by instruments, they have recently become an attractive method of choice. The formation of purple-colored aggregates (attraction) from the red dispersed (repulsion) state of GNPs in the presence of mono- or divalent ions is the key principle behind this assay. Due to its simplicity and versatility, this assay can be an alternative to existing diagnostic assays. Here, we have investigated the critical elements involved in colorimetric assays, and have screened different proteins and small ligands to evaluate biofouling on GNPs. PMID:23948242

Gopinath, Subash C B; Lakshmipriya, Thangavel; Awazu, Koichi

2014-01-15

144

Colorimetric and plasmonic detection of lectins using core-shell gold glyconanoparticles prepared by copper-free click chemistry.  

PubMed

This study describes the simple preparation of core-shell glycosyl gold nanoparticles (AuNPs) using stepwise, copper-free click chemistry-promoted self-assembly. The as-formed glyco-AuNPs can be used for the selective detection of sugar-lectin interactions, which are vital to many important physiological and pathological processes. The approach uses AuNPs as bioprobes since they produce, sensitively, changes in both color visible to the naked eye and surface plasmon resonance (SPR), on aggregation. Strain-promoted click reaction of an azido galactoside with a lipid cyclooctyne affords a galactolipid that can be embedded into polyethylene glycol (PEG)-coated AuNP via self-assembly. Subsequently, using naked-eye and plasmon resonance scattering spectroscopy, we were able to observe the colorimetric and plasmonic variations of the glyco-AuNPs, respectively, in the presence of a selective lectin over other proteins. PMID:25531131

Hu, Xi-Le; Jin, Hong-Ying; He, Xiao-Peng; James, Tony D; Chen, Guo-Rong; Long, Yi-Tao

2015-01-28

145

Graphene oxide-Fe3O4 magnetic nanocomposites with peroxidase-like activity for colorimetric detection of glucose  

NASA Astrophysics Data System (ADS)

In this report, graphene oxide-Fe3O4 magnetic nanocomposites were demonstrated to possess intrinsic peroxidase-like activity and enhanced affinity toward H2O2. The nanocomposites retain their magnetic properties and can be effectively separated by a magnet. Significantly, they were proved to be novel peroxidase mimetics which could quickly catalyze oxidation of the peroxidase substrate 3,3,5,5-tetramethylbenzidine (TMB) in the presence of H2O2, producing a blue-colored solution. Kinetic analysis indicates that the catalytic behavior is in accord with typical Michaelis-Menten kinetics and follows a ping-pong mechanism. On the basis of the high activity, the reaction provides a simple, sensitive and selective method for colorimetric detection of glucose in diabetic urine.

Dong, Ya-Lei; Zhang, Hui-Ge; Rahman, Zia Ur; Su, Li; Chen, Xiao-Jiao; Hu, Jing; Chen, Xing-Guo

2012-06-01

146

Luminescent and colorimetric strategies for the label-free DNA-based detection of enzyme activity.  

PubMed

Enzymes are critically involved in maintaining normal cellular physiology through the catalysis of highly specific and tightly regulated chemical reactions. The inhibition or undesired activation of particular enzymatic functions has been associated with the pathogenesis of a number of diseases. Consequently, the aberrant activity of certain enzymes can be regarded as biomarkers for the diagnosis or monitoring of particular diseases. With rapid technological advances in the field of DNA nanotechnology, oligonucleotides have recently emerged as attractive recognition units for monitoring the activity of enzymes compared with organic small molecules or protein antibodies. In this review article, we present an overview of advantages and versatility of the 'label-free' approach for the fabrication of DNA-based sensing platforms using colorimetric and luminescent molecules as signal transducing units and highlight recent examples of label-free strategies that have been employed for monitoring enzyme activity. PMID:23396725

Leung, Chung-Hang; Zhong, Hai-Jing; Lu, Lihua; Chan, Daniel Shiu-Hin; Ma, Dik-Lung

2013-11-01

147

Peptide functionalized gold nanoparticles for colorimetric detection of matrilysin (MMP-7) activity.  

PubMed

A peptide with two cleavage sites for MMP-7 has been synthesized and immobilized on gold nanoparticles (AuNPs) through a cysteine residue. Digestion of the peptide by MMP-7 decreases its size and net charge, which leads to the aggregation of the AuNPs. The color shift caused by aggregation enables a direct and quantitative measurement of the concentration and activity of MMP-7 with an estimated limit of detection of ?5 nM (0.1 ?g mL(-1)). PMID:23969899

Chen, Peng; Selegård, Robert; Aili, Daniel; Liedberg, Bo

2013-10-01

148

A colorimetric nitrite detection system with excellent selectivity and high sensitivity based on Ag@Au nanoparticles.  

PubMed

Excessive uptake of NO2(-) is detrimental to human health, but the currently available methods used to sensitively detect this ion in the environment are cumbersome and expensive. In this study, we developed an improved NO2(-) detection system based on a redox etching strategy of CTAB-stabilized Ag-Au core-shell nanoparticles (Ag@AuNPs). The detection mechanism was verified by UV-Vis spectroscopy, TEM and XPS. The detection system produces a color change from purple to colorless in response to an increase of NO2(-) concentration. The selectivity of detection of NO2(-), both with the unaided eye and by measurement of UV-Vis spectra, is excellent in relation to other ions, including Cu(2+), Co(2+), Ni(2+), Cr(3+), Al(3+), Pb(2+), Cd(2+), Ca(2+), Ba(2+), Zn(2+), Mn(2+), Mg(2+), Fe(3+), Hg(2+), Ag(+), K(+), F(-), PO4(3-), C2O4(2-), SO3(2-), CO3(2-), SO4(2-), NO3(-) and CH3-COO(-) (Ac(-)). The limit of detection (LOD) for NO2(-) is 1.0 ?M by eye and 0.1 ?M by UV-Vis spectroscopy. The LOD by eye is lower than the lowest previously reported value (4.0 ?M). There is a good linear relationship between A/A0 and the concentration of NO2(-) from 1.0 to 20.0 ?M NO2(-), which permits a quantitative assay. The applicability of our detection system was also verified by analysis of NO2(-) in tap water and lake water. The results demonstrate that our Ag@AuNP-based detection system can be used for the rapid colorimetric detection of NO2(-) in complex environmental samples, with excellent selectivity and high sensitivity. PMID:25564225

Li, Tianhua; Li, Yonglong; Zhang, Yujie; Dong, Chen; Shen, Zheyu; Wu, Aiguo

2015-02-01

149

Fast functionalization of silver decahedral nanoparticles with aptamers for colorimetric detection of human platelet-derived growth factor-BB.  

PubMed

Aptamer-silver decahedral nanoparticles (Ag10NPs-aptamer) based detection was developed for protein. Ag10NPs were synthesized by photochemical method. The advantage of Ag10NPs was its tolerance of NaCl which facilitates the functionalization of silver nanoparticles with all kinds of ssDNA. Attaching aptamers to Ag10NPs could be achieved within 2 h, much faster than traditional methods. Human platelet-derived growth factor-BB (PDGF-BB) was used as a model protein to test the binding capacity of aptamers attached on Ag10NPs. Our data showed that the aptamer-Ag10NPs conjugates were successful in detecting human PDGF-BB. Furthermore, we developed an aptamer-Ag10NPs conjugates-based colorimetric sensor to detect PDGF-BB. The results showed a linear relationship between PDGF-BB concentrations (5 ng mL(-1)-200 ng mL(-1)) and ?OD with excellent detection specificity in serum. Therefore, the sensor based on aptamer-Ag10NPs conjugates was highly effective and sensitive and had great promise for further development and applications. PMID:24856402

Li, Hui; Zhu, Yue; Dong, Shiyu; Qiang, Weibing; Sun, Liang; Xu, Danke

2014-06-01

150

Sensitive and selective colorimetric detection of Cu(2+) in aqueous medium via aggregation of thiomalic acid functionalized Ag nanoparticles.  

PubMed

A simple and effective colorimetric method for determination of Cu(2+) in real samples was developed. In this method, thiomalic acid functionalized silver nanoparticles (TMA-AgNPs) were prepared and changes in solution color, induced by the aggregation of TMA-AgNPs in the presence of Cu(2+), were employed for quantitative analysis. The surface plasmon resonance (SPR) band of our synthesized TMA-AgNPs was located at 392 nm and shifted to a longer wavelength after aggregation due to the interactions between carboxylate and Cu(2+). A band intensity ratio of A455/(A392-A455) was constructed and used to correlate with the concentration of Cu(2+). A linear relationship was found with a linear response up to 50 nM of Cu(2+). Due to the formation of a stable carboxylate Cu(2+) complex, highly sensitive detection of Cu(2+) was achieved with the estimated detection limit approaching 1 nM. Moreover, the formation of the stable complex leads to high selectivity in the detection of Cu(2+), which was verified by examination of 12 other metal ions. In the detection of Cu(2+) in real samples, results indicated that our proposed method is simple, sensitive and selective for application in such measurements. PMID:25316548

Tharmaraj, Vairaperumal; Yang, Jyisy

2014-12-01

151

Novel cellulose polyampholyte-gold nanoparticle-based colorimetric competition assay for the detection of cysteine and mercury(II).  

PubMed

We provide a highly sensitive and selective assay to detect cysteine (Cys) and Hg(2+) in aqueous solutions using Au nanoparticles (NPs) stabilized by carboxylethyl quaternized cellulose (CEQC). This method is based on the thiophilicity of Hg(2+) and Au NPs as well as the unique optical properties of CEQC-stabilized Au NPs. CEQC chains are good stabilizing agents for Au NPs even in a high-salt solution. The addition of Cys results in the aggregation of CEQC-stabilized Au NPs, which induces the visible color change and obvious redshift in UV-visible absorption spectra. On the other hand, Hg(2+) is more apt to interact with thiols than Au NPs; thus, it can remove the Cys and trigger Au NP aggregate redispersion again. By taking advantage of this mechanism, a novel off-on colorimetric sensor has been established for Cys and Hg(2+) detection. This new assay could selectively detect Cys and Hg(2+) with the detection limits as low as 20 and 40 nM in aqueous solutions, respectively. PMID:23527619

You, Jun; Hu, Haoze; Zhou, Jinping; Zhang, Lina; Zhang, Yaping; Kondo, Tetsuo

2013-04-23

152

Detection of measles, mumps and rubella viruses by immuno-colorimetric assay and its application in focus reduction neutralization tests.  

PubMed

Measles, mumps and rubella are vaccine-preventable diseases; however limited epidemiological data are available from low-income or developing countries. Thus, it is important to investigate the transmission of these viruses in different geographical regions. In this context, a cell culture-based rapid and reliable immuno-colorimetric assay (ICA) was established and its utility studied. Twenty-three measles, six mumps and six rubella virus isolates and three vaccine strains were studied. Detection by ICA was compared with plaque and RT-PCR assays. In addition, ICA was used to detect viruses in throat swabs (n?=?24) collected from patients with suspected measles or mumps. Similarly, ICA was used in a focus reduction neutralization test (FRNT) and the results compared with those obtained by a commercial IgG enzyme immuno assay. Measles and mumps virus were detected 2 days post-infection in Vero or Vero-human signaling lymphocytic activation molecule cells, whereas rubella virus was detected 3 days post-infection in Vero cells. The blue stained viral foci were visible by the naked eye or through a magnifying glass. In conclusion, ICA was successfully used on 35 virus isolates, three vaccine strains and clinical specimens collected from suspected cases of measles and mumps. Furthermore, an application of ICA in a neutralization test (i.e., FRNT) was documented; this may be useful for sero-epidemiological, cross-neutralization and pre/post-vaccine studies. PMID:25244651

Vaidya, Sunil R; Kumbhar, Neelakshi S; Bhide, Vandana S

2014-12-01

153

Colorimetric assay for parallel detection of Cd2+, Ni2+ and Co2+ using peptide-modified gold nanoparticles.  

PubMed

A colorimetric assay has been developed for parallel detection of Cd(2+), Ni(2+) and Co(2+) utilizing peptide-modified gold nanoparticles (P-AuNPs) as a sensing element based on its unique surface plasmon resonance properties. The functional peptide ligand, CALNNDHHHHHH, was self-assembled on gold nanoparticles (AuNPs) to produce P-AuNPs probe. The P-AuNPs probe could be used to simultaneously detect and showed different responses to the three ions Cd(2+), Ni(2+) and Co(2+) in an aqueous solution based on the aggregation-induced color change of AuNPs. The method showed good selectivity for Cd(2+), Ni(2+) and Co(2+) over other metal ions, and detection limit as low as 0.05 ?M Cd(2+), 0.3 ?M Ni(2+) or 2 ?M Co(2+). To simultaneously (or parallel) detect the three metal ions coexisting in a sample, EDTA and imidazole were applied to mask Co(2+) and Ni(2+) for detecting Cd(2+), glutathione and EDTA were applied to mask Cd(2+) and Co(2+) for detecting Ni(2+), and glutathione and imidazole were applied to mask Cd(2+) and Ni(2+) for detecting Co(2+). Finally, the simple and cost-effective probe could be successfully applied for simultaneously detecting Cd(2+), Ni(2+), and Co(2+) in river water. Because this novel P-AgNPs-based probe design offers many advantages, including simplicity of preparation and manipulation compared with other methods that employ specific strategies, the sensing system shows potential application in the developing region for monitoring water quality. PMID:22158918

Zhang, Min; Liu, Yu-Qiang; Ye, Bang-Ce

2012-02-01

154

Highly efficient colorimetric detection of target cancer cells utilizing superior catalytic activity of graphene oxide-magnetic-platinum nanohybrids  

NASA Astrophysics Data System (ADS)

Enzyme-linked immunosorbent assays (ELISAs) have most widely been applied in immunoassays for several decades. However, several unavoidable limitations (e.g., instability caused by structural unfolding) of natural enzymes have hindered their widespread applications. Here, we describe a new nanohybrid consisting of Fe3O4 magnetic nanoparticles (MNPs) and platinum nanoparticles (Pt NPs), simultaneously immobilized on the surface of graphene oxide (GO). By synergistically integrating highly catalytically active Pt NPs and MNPs on GO whose frameworks possess high substrate affinity, the nanohybrid is able to achieve up to a 30-fold higher maximal reaction velocity (Vmax) compared to that of free GO for the colorimetric reaction of the peroxidase substrate, 3,3',5,5'-tetramethylbenzidine (TMB), and enable rapid detection of target cancer cells. Specifically, using this new assay system, clinically important breast cancer cells are detected in a 5 min time period at room temperature with high specificity and sensitivity. The remarkably high capability to catalyze oxidation reactions could allow the nanohybrid to replace conventional peroxidase-based immunoassay systems as part of new, rapid, robust and convenient assay systems which can be widely utilized for the identification of important target molecules.Enzyme-linked immunosorbent assays (ELISAs) have most widely been applied in immunoassays for several decades. However, several unavoidable limitations (e.g., instability caused by structural unfolding) of natural enzymes have hindered their widespread applications. Here, we describe a new nanohybrid consisting of Fe3O4 magnetic nanoparticles (MNPs) and platinum nanoparticles (Pt NPs), simultaneously immobilized on the surface of graphene oxide (GO). By synergistically integrating highly catalytically active Pt NPs and MNPs on GO whose frameworks possess high substrate affinity, the nanohybrid is able to achieve up to a 30-fold higher maximal reaction velocity (Vmax) compared to that of free GO for the colorimetric reaction of the peroxidase substrate, 3,3',5,5'-tetramethylbenzidine (TMB), and enable rapid detection of target cancer cells. Specifically, using this new assay system, clinically important breast cancer cells are detected in a 5 min time period at room temperature with high specificity and sensitivity. The remarkably high capability to catalyze oxidation reactions could allow the nanohybrid to replace conventional peroxidase-based immunoassay systems as part of new, rapid, robust and convenient assay systems which can be widely utilized for the identification of important target molecules. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr05539f

Kim, Moon Il; Kim, Min Su; Woo, Min-Ah; Ye, Youngjin; Kang, Kyoung Suk; Lee, Jinwoo; Park, Hyun Gyu

2014-01-01

155

A label-free DNA hairpin biosensor for colorimetric detection of target with suitable functional DNA partners.  

PubMed

The combination of aptamer and peroxidase-mimicking DNAzyme within a hairpin structure can form a functional DNA probe. The activities of both aptamer (as biorecognition element) and DNAzyme (as signal amplification element) are blocked via base pairing in the hairpin structure. The presence of target triggers the opening of the hairpin to form target/aptamer complex and releases G-quadruplex sequence which can generate amplified colorimetric signals. In this work, we elaborated a universal and simple procedure to design an efficient and sensitive hairpin probe with suitable functional DNA partners. A fill-in-the-blank process was developed for sequence design, and two key points including the pretreatment of the hairpin probe and the selection of suitable signal transducer sequence were proved to enhance the detection sensitivity. Cocaine was chosen as a model target for a proof of concept. A series of hairpins with different numbers of base pairs in the stem region were prepared. Hairpin-C10 with ten base pairs was screened out and a lowest detectable cocaine concentration of 5 ?M by colorimetry was obtained. The proposed functional DNA hairpin showed good selectivity and satisfactory analysis in spiked biologic fluid. The whole "mix-and-measure" detection based on DNA hairpin without the need of immobilization and labeling was indicated to be time and labor saving. The strategy has potential to be transplanted into more smart hairpins toward other targets for general application in bioanalytical chemistry. PMID:23770395

Nie, Ji; Zhang, De-Wen; Tie, Cai; Zhou, Ying-Lin; Zhang, Xin-Xiang

2013-11-15

156

A sensitive and selective colorimetric method for detection of copper ions based on anti-aggregation of unmodified gold nanoparticles.  

PubMed

A highly sensitive and selective colorimetric method for detection of copper ions, based on anti-aggregation of D-penicillamine (D-PC) induced aggregated gold nanoparticles (AuNPs) was developed. Copper ions can hinder the aggregation of AuNPs induced by D-PC, through formation of mixed-valence complex with D-PC that is a selective copper chelator. In the presence of a fixed amount of D-PC, the aggregation of AuNPs decreases with increasing concentrations of Cu(2+) along with a color change from blue to red in AuNPs solution and an increase in the absorption ratio (A520/A650). Under the optimum experimental conditions (pH 7, [AuNPs] =3.0 nmol L(-1) and [NaCl]=25 mmol L(-1)), a linear calibration curve for Cu(2+) was obtained within the range of 0.05-1.85 µmol L(-1) with a limit of detection (3Sb) of 30 nmol L(-1). Excellent selectivity toward Cu(2+) was observed among various metal ions due to a specific complex formation between Cu(2+) and D-PC. The proposed method has been successfully applied for the detection of Cu(2+) in various real samples. PMID:25127588

Hormozi-Nezhad, M Reza; Abbasi-Moayed, Samira

2014-11-01

157

Simple azo-based salicylaldimine as colorimetric and fluorescent probe for detecting anions in semi-aqueous medium.  

PubMed

A series of novel, highly sensitive, and selective azo-based anion sensors 1-3 have been designed and synthesized from the condensation reaction between 4-amino azo benzene and three different aldehydes. The structure of the sensors 1-3 were confirmed by IR, HRMS, (1)H NMR, and (13)C NMR spectroscopic methods. Colorimetric naked-eye analysis revealed the anion detection by receptors 2 and 3 as color changes from yellow to pink and yellow to orange, respectively. Anion sensing ability of all receptors was further investigated by (1) H NMR titration, UV-vis experiment, and fluorescence titration. UV-vis measurements highly indicate the selective recognition of fluoride and acetate ions in 9:1 dimethyl sulfoxide-H2O (v/v) for receptors 2 and 3. Binding constant value showed among all receptors, receptor 3 has strong affinity toward F(-) and AcO(-) in semi-aqueous medium, which is due to the presence of chromogenic signaling unit in it. The F(-) ion detection property of receptor 2 in organic medium was also extended in the real sample like toothpaste. PMID:23595807

Suganya, Sivalingam; Velmathi, Sivan

2013-06-01

158

Microsystem-assisted synthesis of carbon dots with fluorescent and colorimetric properties for pH detection  

NASA Astrophysics Data System (ADS)

The present paper describes the use of a microfluidic system to synthesize carbon dots (Cdots) and their use as optical pH sensors. The synthesis is based on the thermal decomposition of ascorbic acid in dimethyl sulfoxide. The proposed microsystem is composed of a fluidic and a thermal platform, which enable proper control of synthesis variables. Uniform and monodispersed 3.3 nm-sized Cdots have been synthesized, the optical characterization of which showed their down/upconversion luminescence and colorimetric properties. The obtained Cdots have been used for pH detection with down and upconverison fluorescent properties as excitation sources. The naked eye or a photographic digital camera has also been implemented as detection systems with the hue parameter showing a linear pH range from 3.5 to 10.2. On the other hand, experiments on the cytotoxicity and permeability of the Cdots on human embryonic kidney cells revealed their adsorption on cells without causing any impact on the cellular morphology.

Pedro, S. Gómez-De; Salinas-Castillo, A.; Ariza-Avidad, M.; Lapresta-Fernández, A.; Sánchez-González, C.; Martínez-Cisneros, C. S.; Puyol, M.; Capitan-Vallvey, L. F.; Alonso-Chamarro, J.

2014-05-01

159

Microsystem-assisted synthesis of carbon dots with fluorescent and colorimetric properties for pH detection.  

PubMed

The present paper describes the use of a microfluidic system to synthesize carbon dots (Cdots) and their use as optical pH sensors. The synthesis is based on the thermal decomposition of ascorbic acid in dimethyl sulfoxide. The proposed microsystem is composed of a fluidic and a thermal platform, which enable proper control of synthesis variables. Uniform and monodispersed 3.3 nm-sized Cdots have been synthesized, the optical characterization of which showed their down/upconversion luminescence and colorimetric properties. The obtained Cdots have been used for pH detection with down and upconverison fluorescent properties as excitation sources. The naked eye or a photographic digital camera has also been implemented as detection systems with the hue parameter showing a linear pH range from 3.5 to 10.2. On the other hand, experiments on the cytotoxicity and permeability of the Cdots on human embryonic kidney cells revealed their adsorption on cells without causing any impact on the cellular morphology. PMID:24777567

Gómez-de Pedro, S; Salinas-Castillo, A; Ariza-Avidad, M; Lapresta-Fernández, A; Sánchez-González, C; Martínez-Cisneros, C S; Puyol, M; Capitan-Vallvey, L F; Alonso-Chamarro, J

2014-06-01

160

Binding-induced and label-free colorimetric method for protein detection based on autonomous assembly of hemin/G-quadruplex DNAzyme amplification strategy.  

PubMed

In this work, a new binding-induced and label-free colorimetric method for protein detection has been developed on the basis of an autonomous assembly of hemin/G-quadruplex DNAzyme amplification strategy. The system consists of two proximity probes carrying two aptamer sequences as recognition elements for target, and two hairpin structures include three-fourths and one-fourth of the G-quadruplex sequences in inactive configuration as functional elements. In the presence of target protein, two proximity probes bind to the protein simultaneously, forming a stable DNA-protein complex. Then the complex triggers an autonomous cross-opening of the two functional hairpin structures, leading to the formation of numerous hemin/G-quadruplex DNAzymes. The resulting DNAzymes catalyze the oxidation of colorless 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS(2-)) to the green-colored ABTS(•-) with the presence of H2O2, thus providing the amplified colorimetric detection of target. Using human ?-thrombin as the protein target, this binding-induced DNAzyme amplification colorimetric method affords high sensitivity with a detection limit of 1.9 pM. Furthermore, this method might be further extended to sensitive detection of other proteins by simply replacing recognition elements of proximity probes. PMID:25310491

Wu, Hao; Zhang, Kai; Liu, Yaling; Wang, Hongyong; Wu, Jun; Zhu, Feifan; Zou, Pei

2015-02-15

161

Dark Matter: Direct Detection  

SciTech Connect

The identification of Dark Matter is an outstanding question of contemporary physics. I summarize the main experimental strategies developed to answer this question, focusing on cryogenic detectors and comparing these detectors to their double-phase xenon and argon competitors. I discuss in particular the main developments in charge-phonon (CDMS, EDELWEISS) and light-phonon detectors (CRESST, ROSEBUD). Finally, I discuss the prospects of WIMP detection within the next few years by the CDMS, CRESST, EDELWEISS and XENON experiments, and their successors EURECA, GEODM and XENON-1 ton.

Chardin, G. [CSNSM, CNRS/IN2P3 and Universite Paris-Sud, Orsay (France)

2009-12-16

162

Genotoxic activity detected in soils from a hazardous waste site by the Ames test and an SOS colorimetric test  

SciTech Connect

Ten soil samples from a hazardous waste site were compared for their genotoxic activity by the Ames test (Salmonella reverse mutation assay) and a modified SOS colorimetric test. Polynuclear aromatic hydrocarbons known to produce frameshift mutations were found in high levels in the soils. Salmonella typhimurium TA98, sensitive to frameshift mutations, was selected as the Ames tester strain. Escherichia coli K12 PQ37 (sulA::lacZ) was the SOS tester strain. Organic extracts were prepared from the soil samples by Soxhlet extraction. One set of the soil samples was extracted with methylene chloride and a second set with cyclohexane. Two criteria from reproducible dose-related increases in response to the soil were used to compare the positive responses: 1. the concentrations required for doubling responses and 2. a minimum concentration required to produce statistically significant increases from background controls. Analysis of variance indicated that with S9 mix, Ames and SOS results were similar for the same soils and solvent extractions. However, without S9 mix, the SOS test was significantly more sensitive than the Ames test to the genotoxins extracted from the soils. Both the Ames and SOS tests detected lower concentrations of genotoxins in methylene chloride than in cyclohexane extracts. The simplicity of the method, reduction in expenses, and results within 1 working day all contribute to the advantages of the SOS test.

McDaniels, A.E.; Reyes, A.L.; Wymer, L.J.; Rankin, C.C.; Stelma, G.N. Jr. (Environmental Protection Agency, Cincinnati, OH (United States))

1993-01-01

163

BSA-stabilized Pt nanozyme for peroxidase mimetics and its application on colorimetric detection of mercury(II) ions.  

PubMed

Bovine serum albumin (BSA) is chosen as the nucleation templates to synthesize Pt-based peroxidase nanomimetics with the average diameter of 2.0nm. The efficient Pt nanozymes consist of 57% Pt(0) and 43% Pt(2+), which possess highly peroxidase-like activity with the Km values of 0.119mM and 41.8mM toward 3,3',5,5'-tetramethylbenzidine (TMB) and hydrogen peroxide (H2O2), respectively. Interestingly, Hg(2+) is able to down-regulate the enzymatic activity of Pt nanoparticles, mainly through the interactions between Hg(2+) and Pt(0). It is the first report to explore a colorimetric Hg(2+) sensing system on the basis of peroxidase mimicking activities of Pt nanoparticles. One of our most intriguing results is that BSA-stabilized Pt nanozymes demonstrate the ability to sense Hg(2+) ions in aqueous solution without significant interference from other metal ions. The Hg(2+) detection limit of 7.2nM is achieved with a linear response range of 0-120nM, and the developed sensing system is potentially applicable for quantitative determination of Hg(2+) in drinking water. PMID:25437360

Li, Wei; Chen, Bin; Zhang, Haixiang; Sun, Yanhua; Wang, Jun; Zhang, Jinli; Fu, Yan

2015-04-15

164

Microfluidic Toner-Based Analytical Devices: Disposable, Lightweight, and Portable Platforms for Point-of-Care Diagnostics with Colorimetric Detection.  

PubMed

This chapter describes the development of microfluidic toner-based analytical devices (?TADs) to perform clinical diagnostics using a scanner or cell-phone camera. ?TADs have been produced in a platform composed of polyester and toner by the direct-printing technology (DPT) in a matter of minutes. This technology offers simplicity and versatility, and it does not require any sophisticated instrumentation. Toner-based devices integrate the current generation of disposable analytical devices along paper-based chips. The cost of one ?TAD has been estimated to be lower than $0.10. In addition, these platforms are lightweight and portable thus enabling their use for point-of-care applications. In the last 5 years, great efforts have been dedicated to spread out the use of ?TADs in bioassays. The current chapter reports the fabrication of printed microplates and integrated microfluidic toner-based devices for dengue diagnostics and rapid colorimetric assays with clinically relevant analytes including cholesterol, triglycerides, total proteins, and glucose. The use of ?TADs associated with cell-phone camera may contribute to the health care, in special, to people housed in developing regions or with limited access to clinics and hospitals. PMID:25626533

Oliveira, Karoliny Almeida; de Souza, Fabrício Ribeiro; de Oliveira, Cristina Rodrigues; da Silveira, Lucimeire Antonelli; Coltro, Wendell Karlos Tomazelli

2015-01-01

165

Wimp/Neutralino Direct Detection  

E-print Network

The most popular candidate for non baryonic dark matter is the neutralino. More than twenty experiments are dedicated to its direct detection. This review describes the most competitive and promising experiments with different detection techniques. The most recent results are presented with some prospects for the near future.

M. De Jesus

2004-02-02

166

Immunosorbent analysis of ricin contamination in milk using colorimetric, chemiluminescence, and electrochemiluminescence detection  

Technology Transfer Automated Retrieval System (TEKTRAN)

Analytical methodology to detect ricin in food matrices is important because of the potential use of foodborne ricin as a terrorist weapon. Monoclonal antibodies (mAbs) that bind ricin were used for both capture and detection in sandwich enzyme-linked immunosorbent assay (ELISA) and electrochemilumi...

167

Multiplexed colorimetric detection of Kaposi's sarcoma associated herpesvirus and Bartonella DNA using gold  

E-print Network

for each target and a multi-color change system is developed capable of detecting both targets down-of-care KS detection. Introduction With the onset of the acquired immunodeciency syndrome (AIDS) epidemic hematoxylin and eosin (H&E) stained histology slide has a number of unique features, including vascular spaces

Erickson, David

168

pKa Modulation in rhodamine based probes for colorimetric detection of picric acid.  

PubMed

Tuning the pKa in acid sensitive rhodamine spirolactam derivatives as a function of the solvent medium resulted in the selective detection of picric acid from its lower nitro phenolic analogues and a few other carboxylic acids. PMID:25339183

Nagarajan, V; Bag, Bamaprasad

2014-12-21

169

A SIMPLE COLORIMETRIC METHOD TO DETECT BIOLOGICAL EVIDENCE OF HUMAN EXPOSURE TO MICROCYSTINS  

EPA Science Inventory

Toxic cyanobacteria are contaminants of surface waters worldwide. Microcystins are some of the most commonly detected toxins. Biological evidence of human exposure may be difficult to obtain due to limitations associated with cost, laboratory capacity, analytic support, and exp...

170

Multiplexed colorimetric detection of Kaposi's sarcoma associated herpesvirus and Bartonella DNA using gold and silver nanoparticles  

NASA Astrophysics Data System (ADS)

Kaposi's sarcoma (KS) is an infectious cancer occurring most commonly in human immunodeficiency virus (HIV) positive patients and in endemic regions, such as Sub-Saharan Africa, where KS is among the top four most prevalent cancers. The cause of KS is the Kaposi's sarcoma-associated herpesvirus (KSHV, also called HHV-8), an oncogenic herpesvirus that while routinely diagnosed in developed nations, provides challenges to developing world medical providers and point-of-care detection. A major challenge in the diagnosis of KS is the existence of a number of other diseases with similar clinical presentation and histopathological features, requiring the detection of KSHV in a biopsy sample. In this work we develop an answer to this challenge by creating a multiplexed one-pot detection system for KSHV DNA and DNA from a frequently confounding disease, bacillary angiomatosis. Gold and silver nanoparticle aggregation reactions are tuned for each target and a multi-color change system is developed capable of detecting both targets down to levels between 1 nM and 2 nM. The system developed here could later be integrated with microfluidic sample processing to create a final device capable of solving the two major challenges in point-of-care KS detection.

Mancuso, Matthew; Jiang, Li; Cesarman, Ethel; Erickson, David

2013-01-01

171

A simple visual and highly selective colorimetric detection of Hg2+ based on gold nanoparticles modified by 8-hydroxyquinolines and oxalates.  

PubMed

Gold nanoparticles (AuNPs) modified by 8-hydroxy-quinoline (8-HQ) and stabilized by polyvinylpyrrolidone (PVP) were used for highly selective and sensitive colorimetric detection of Hg(2+) based on the quick aggregation of AuNPs leading to a color change from wine red to gray. The limit of Hg(2+) detection in real environmental water samples is 4.0 × 10(-7) M by the naked eyes and 1.0 × 10(-8) M by UV-vis spectroscopy. PMID:24622578

Gao, Yuexia; Li, Xing; Li, Yonglong; Li, Tianhua; Zhao, Yayun; Wu, Aiguo

2014-06-21

172

Colorimetric detection of Ehrlichia canis via nucleic acid hybridization in gold nano-colloids.  

PubMed

Canine monocytic ehrlichiosis (CME) is a major thick-bone disease of dog caused by Ehrlichia canis. Detection of this causal agent outside the laboratory using conventional methods is not effective enough. Thus an assay for E. canis detection based on the p30 outer membrane protein gene was developed. It was based on the p30 gene amplification using loop-mediated isothermal DNA amplification (LAMP). The primer set specific to six areas within the target gene were designed and tested for their sensitivity and specificity. Detection of DNA signals was based on modulation of gold nanoparticles' surface properties and performing DNA/DNA hybridization using an oligonucleotide probe. Presence of target DNA affected the gold colloid nanoparticles in terms of particle aggregation with a plasmonic color change of the gold colloids from ruby red to purple, visible by the naked eye. All the assay steps were completed within 90 min including DNA extraction without relying on standard laboratory facilities. This method was very specific to target bacteria. Its sensitivity with probe hybridization was sufficient to detect 50 copies of target DNA. This method should provide an alternative choice for point of care control and management of the disease. PMID:25111239

Muangchuen, Ajima; Chaumpluk, Piyasak; Suriyasomboon, Annop; Ekgasit, Sanong

2014-01-01

173

Colorimetric Detection of Ehrlichia Canis via Nucleic Acid Hybridization in Gold Nano-Colloids  

PubMed Central

Canine monocytic ehrlichiosis (CME) is a major thick-bone disease of dog caused by Ehrlichia canis. Detection of this causal agent outside the laboratory using conventional methods is not effective enough. Thus an assay for E. canis detection based on the p30 outer membrane protein gene was developed. It was based on the p30 gene amplification using loop-mediated isothermal DNA amplification (LAMP). The primer set specific to six areas within the target gene were designed and tested for their sensitivity and specificity. Detection of DNA signals was based on modulation of gold nanoparticles' surface properties and performing DNA/DNA hybridization using an oligonucleotide probe. Presence of target DNA affected the gold colloid nanoparticles in terms of particle aggregation with a plasmonic color change of the gold colloids from ruby red to purple, visible by the naked eye. All the assay steps were completed within 90 min including DNA extraction without relying on standard laboratory facilities. This method was very specific to target bacteria. Its sensitivity with probe hybridization was sufficient to detect 50 copies of target DNA. This method should provide an alternative choice for point of care control and management of the disease. PMID:25111239

Muangchuen, Ajima; Chaumpluk, Piyasak; Suriyasomboon, Annop; Ekgasit, Sanong

2014-01-01

174

DETECTION OF ESCHERICHIA COLI IN WATER USING A COLORIMETRIC GENE PROBE ASSAY  

EPA Science Inventory

A commercially available DNA hydribization assay (Gene-trak , Framingham, MA. USA) was compared with the EC-MUG procedure for the detection of Escherichia coli in water. The gene probe gave positive responses for pure cultures of E. coli 0157:H7, E. fergusonii, Shigella sonnei, S...

175

Simple Colorimetric Method for Detecting Degenerate Strains of the Cultivated Basidiomycete Flammulina velutipes (Enokitake)  

Microsoft Academic Search

The primary objective of this study was to develop a simple method for detecting degenerate Flammulina velutipes (Eno- kitake) cultures. Cultural degeneration of cultivated strains of Enokitake similar to the degeneration observed for Agaricus bisporus (1, 2) has become a serious problem in Japan. Previ- ous efforts to evaluate the fruiting potential of Enokitake have been made using isozyme electrophoresis

Yumi Magae; Kobun Akahane; Kimiyoshi Nakamura; Shigeyuki Tsunoda

2005-01-01

176

A Novel Porphyrin-Containing Polyimide Nanofibrous Membrane for Colorimetric and Fluorometric Detection of Pyridine Vapor  

PubMed Central

A novel zinc porphyrin-containing polyimide (ZPCPI) nanofibrous membrane for rapid and reversible detection of trace amounts of pyridine vapor is described. The membrane displays a distinct color change, as well as dramatic variations in absorption and fluorescent emission spectra, upon exposure to pyridine vapor. This condition allows the detection of the analyte at concentrations as low as 0.041 ppm. The vapochromic and spectrophotometric responses of the membrane are attributed to the formation of the ZPCPI-pyridine complex upon axial coordination. From surface plasmon resonance analysis, the affinity constant of ZPCPI-pyridine complex was calculated to be (3.98 ± 0.25) × 104 L·mol?1. The ZPCPI nanofibrous membrane also showed excellent selectivity for pyridine vapor over other common amines, confirming its applicability in the manufacture of pyridine-sensitive gas sensors. PMID:24256976

Lv, Yuanyuan; Zhang, Yani; Du, Yanglong; Xu, Jiayao; Wang, Junbo

2013-01-01

177

Use of a colorimetric system to detect enzymes expressed by germinating conidia of entomopathogenic fungi.  

PubMed

An apiZYM system, with 19 substrates, was used to detect enzymes expressed by germinating conidia of Nomuraea rileyi (5 isolates), Nomuraea atypicola, Nomuraea anemonoides, Beauveria bassiana and Metarhizium anisopliae. Similar enzyme profiles were obtained for two of the N. rileyi isolates (Mississippi, Ecuador) regardless of whether culture medium (Sabouraud-maltose-yeast) or cuticle (from larvae of Trichoplusia ni, Heliothis zea or Heliothis virescens) were used as substrates. Centroid-clustering analysis revealed three distinct enzyme profiles. PMID:1406899

el-Sayed, G N; Ignoffo, C M; Leathers, T D; Gupta, S C

1992-04-01

178

A colorimetric and fluorescent turn on chemodosimeter for Pd(2+) detection.  

PubMed

A novel rhodamine derivative L had been successfully developed and well characterized by NMR, and Mass spectroscopy. Chemodosimeter L is a naked-eye fluorescent chemodosimeter for Pd(2+) in aqueous solution. More over the detection limit of Chemodosimeter L is in 10(-7)M level. The Ligand to L ratio was determined to be 1:2 according to the job's plot. PMID:25534416

Li, Lianqing; Liu, Zhihong

2015-03-01

179

BODIPY based colorimetric fluorescent probe for selective thiophenol detection: theoretical and experimental studies.  

PubMed

A BODIPY-based selective thiophenol probe capable of discriminating aliphatic thiols is reported. The fluorescence off-on effect upon reaction with thiol is elucidated with theoretical calculations. The sensing of thiophenol is associated with a color change from red to yellow and 63-fold enhancement in green fluorescence. Application of the probe for selective thiophenol detection is demonstrated by live cell imaging. PMID:22751002

Kand, Dnyaneshwar; Mishra, Pratyush Kumar; Saha, Tanmoy; Lahiri, Mayurika; Talukdar, Pinaki

2012-09-01

180

Colorimetric detection of hydrogen peroxide and glucose using the magnetic mesoporous silica nanoparticles.  

PubMed

In this work, we synthesized a type of magnetic mesoporous silica nanoparticle (denoted as Fe3O4@MSN) with Fe3O4 as the core and mesoporous silica the shell. The superparamagnetic Fe3O4-core provides high peroxidase-mimic activity and makes the artificial enzymatic system easily recyclable. Furthermore, Fe3O4 nanoparticles are encapsulated in MSN shells to hinder the aggregation and keep them stable even under harsh conditions. Meanwhile, small active molecules are allowed to diffuse in and out of the MSN shells. Based on these functional units, the Fe3O4@MSN as robust nanoreactors can catalyze a self-organized cascade reaction, which includes oxidation of glucose by oxygen to yield gluconic acid and H2O2, and the latter further oxidizes 3,3,5,5-tetramethylbenzidine (TMB) to produce a color change. The Fe3O4@MSN, whose catalytic efficiency was not strongly dependent on pH and temperature, was successfully used for the detection of glucose and showed excellent sensitivity with a detection limit of 0.4×10(-5)mol/L. Nevertheless, the assay is also highly selective toward the glucose detection. PMID:25618726

Wang, Yonghong; Zhou, Bo; Wu, Shun; Wang, Kemin; He, Xiaoxiao

2015-03-01

181

A colorimetric chemosensor for Cu2+ ion detection based on an iridium(III) complex  

NASA Astrophysics Data System (ADS)

We report herein the synthesis and application of a series of novel cyclometalated iridium(III) complexes 1-3 bearing a rhodamine-linked NˆN ligand for the detection of Cu2+ ions. Under the optimised conditions, the complexes exhibited high sensitivity and selectivity for Cu2+ ions over a panel of other metal ions, and showed consistent performance in a pH value range of 6 to 8. Furthermore, the potential application of this system for the monitoring of Cu2+ ions in tap water or natural river water samples was demonstrated.

Wang, Modi; Leung, Ka-Ho; Lin, Sheng; Chan, Daniel Shiu-Hin; Kwong, Daniel W. J.; Leung, Chung-Hang; Ma, Dik-Lung

2014-10-01

182

A Highly Selective Turn-On Colorimetric, Red Fluorescent Sensor for Detecting Mobile Zinc in Living Cells  

E-print Network

We describe ZRL1, a turn-on colorimetric and red fluorescent zinc ion sensor. The Zn2+-promoted ring opening of the rhodamine spirolactam ring in ZRL1 evokes a 220-fold fluorescence turn-on response. In aqueous media, ZRL1 ...

Du, Pingwu

183

Colorimetric detection of manganese(II) ions using gold/dopa nanoparticles  

NASA Astrophysics Data System (ADS)

We report here a one-pot, greener, eco-friendly strategy for the synthesis of gold nanoparticles using L-dopa. The as-prepared dopa-functionalized gold nanoparticles (AuNPs/dopa) can detect low concentrations of manganese(II) metal ions in aqueous solution. The binding forces between dopa and Mn2+ ions cause dopa-functionalized gold nanoparticles to come closer together, decreasing the interparticle distance and aggregating it with a change in color of colloidal solution from red to purplish-blue. Dynamic light scattering (DLS) analysis showed a decreased surface charge on the surface of gold nanoparticles when exposed to Mn2+ ions, which caused cross-linking aggregation. Transmission electron microscopic (TEM) images also revealed the aggregation of gold nanoparticles with the addition of Mn2+ ions. The extinction ratio of absorbance at 700-550 nm (A700/A550) was linear against the concentration of [Mn2+] ions. Thus, the optical absorption spectra of gold colloidal solution before and after the addition of Mn2+ ions reveal the concentration of Mn2+ ions in solution.

Narayanan, Kannan Badri; Park, Hyun Ho

2014-10-01

184

Structural, morphological and optical studies of L-cysteine modified silver nanoparticles and its application as a probe for the selective colorimetric detection of Hg2+  

NASA Astrophysics Data System (ADS)

We report an extensive study on the evolution of a highly facile, selective colorimetric probe for Hg2+ detection using cysteine modified silver nanoparticles. The nanoparticles are stable in a basic medium and the Surface Enhanced Raman Spectrum (SERS) reveal that the cysteine is bound to the Ag surface through the thiolate moiety with the charged carboxylate group pointing outwards in a morphology that lends itself to sensor applications. In the presence of Hg2+, the absorption peak is quenched resulting in a drastic colour change. The sensor displays high selectivity to Hg2+ over other metallic ions.

Nidya, M.; Umadevi, M.; Rajkumar, Beulah J. M.

2014-12-01

185

A colorimetric sensor based on catechol-terminated mixed self-assembled monolayers modified gold nanoparticles for ultrasensitive detections of copper ions.  

PubMed

A colorimetric sensor for Cu(II) ions has been developed based on mixed self-assembled monolayers (SAMs) modified gold nanoparticles (AuNPs). The AuNPs were modified with mixed SAMs consisting of mercaptosuccinic acid and the product of electrochemically triggered Michael addition reaction of 4-thiouracil and catechol. In the presence of Cu(II) ions, the coordination of Cu(2+) to catechol-terminated AuNPs leads to aggregation-induced changes of surface plasmon resonance. The cost-effective chemical sensor allows rapid, sensitive and selective detection of Cu(2+) ions, indicating its potential application in environmental field. PMID:22662323

Ye, Siqiu; Shi, Xinhao; Gu, Wei; Zhang, Yixuan; Xian, Yuezhong

2012-07-21

186

A nanosized metal-organic framework of Fe-MIL-88NH? as a novel peroxidase mimic used for colorimetric detection of glucose.  

PubMed

In this paper, a nanosized porous metal-organic framework, Fe-MIL-88NH?, was facilely prepared with a uniform octahedral shape by the addition of acetic acid, and for the first time was demonstrated to possess intrinsic peroxidase-like activity. Kinetic analysis and electron spin resonance measurements indicated that the catalytic behavior was consistent with typical Michaelis-Menten kinetics and follows a ping-pong mechanism. As a novel peroxidase mimic material, Fe-MIL-88NH? shows the advantages of high catalytic efficiency, ultrahigh stability and high biocompatibility in aqueous medium compared with natural enzymes and other peroxidase nanomimetics. Here, Fe-MIL-88NH? was used to quickly catalyze oxidation of the peroxidase substrate 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H?O? to produce a colored product, which provided a simple, sensitive and selective method for the colorimetric detection of glucose. Glucose could be linearly detected in the range from 2.0 × 10?? to 3.0 × 10?? M with a detection limit of 4.8 × 10?? M, and the color variation for glucose response was also obvious by visual observation at concentrations as low as 2.0 × 10?? M. More importantly, the colorimetric method could be successfully applied to the determination of glucose in diluted serum samples. PMID:23775015

Liu, Ya Li; Zhao, Xi Juan; Yang, Xiao Xi; Li, Yuan Fang

2013-08-21

187

A gold nanoparticles colorimetric assay for label-free detection of protein kinase activity based on phosphorylation protection against exopeptidase cleavage.  

PubMed

Protein kinases are significant regulators in the cell signaling pathways, and it is still greatly desirable to achieve simple and quick kinase detection. Herein, we present a novel colorimetric gold nanoparticles (AuNPs)/peptide platform for probing the activity and inhibition of protein kinases based on phosphorylation-induced suppression of carboxypeptidase Y (CPY) cleavage. This AuNPs/peptide platform can easily monitor the kinase activity by a UV-vis spectrometer or even by the naked eye. The feasibility of the method has been demonstrated by sensitive measurement of the cAMP-dependent protein kinase (PKA) activity with a low detection limit of 0.232 mU/µL and assessment of kinase inhibition by H-89 with an IC50 value of 18.13 nM. The assay was also successfully put into practice for the detection of kinase activity in cell lysate. Because of its label-free, homogenous and colorimetric merits, the proposed assay presents great potential in high-throughput screening for kinase-targeted drug discovery. PMID:24157613

Zhou, Jiang; Xu, Xiahong; Liu, Xin; Li, Hao; Nie, Zhou; Qing, Meng; Huang, Yan; Yao, Shouzhuo

2014-03-15

188

Poly(acrylic acid)-templated silver nanoclusters as a platform for dual fluorometric turn-on and colorimetric detection of mercury (II) ions.  

PubMed

An easy prepared fluorescence turn-on and colorimetric dual channel probe was developed for rapid assay of Hg(2+) ions with high sensitivity and selectivity by using poly(acrylic acid)-templated silver nanoclusters (PAA-AgNCs). The PAA-AgNCs exhibited weak fluorescence, while upon the addition of Hg(2+) ions, AgNCs gives a dramatic increase in fluorescence as a result of the changes of the AgNCs states. The detection limit was estimated to be 2 nM, which is much lower than the Hg(2+) detection requirement for drinking water of U.S. Environmental Protection Agency, and the turn-on sensing mode offers additional advantage to efficiently reduce background noise. Also, a colorimetric assay of Hg(2+) ions can be realized due to the observed absorbance changes of the AgNCs. More importantly, the method was successfully applied to the determination of Hg(2+) ions in real water samples, which suggests our proposed method has a great potential of application in environmental monitoring. PMID:22265501

Tao, Yu; Lin, Youhui; Huang, Zhenzhen; Ren, Jinsong; Qu, Xiaogang

2012-01-15

189

Colorimetric detection of anions in aqueous media using N-monosubstituted diaminomaleonitrile-based azo-azomethine receptors: Real-life applications.  

PubMed

New N-monosubstituted diaminomaleonitrile-based azo-azomethine dyes have been synthesized in order to develop colorimetric sensors for detection of biologically important anions in aqueous media. Importantly, the reported sensor decorated with strong electron-withdrawing group can detect inorganic fluoride in water even at 0.037ppm level, which is lower than WHO permissible level (below 1ppm). Successfully, the prepared dyes were used for qualitative and quantitative detection of inorganic fluoride in toothpaste and mouthwash. The anion recognition mechanism was also investigated by detailed UV-Vis and (1)H NMR experiments. The detailed (1)H NMR experiments corroborated that anion recognition is based on the deprotonation phenomenon. PMID:25576937

Khanmohammadi, Hamid; Rezaeian, Khatereh; Abdollahi, Alieh

2015-03-15

190

Selective and sensitive detection of free bilirubin in blood serum using human serum albumin stabilized gold nanoclusters as fluorometric and colorimetric probe.  

PubMed

We report here a fluorescence quenching based non-enzymatic method for sensitive and reliable detection of free bilirubin in blood serum samples using human serum albumin (HSA) stabilized gold nanoclusters (HSA-AuNCs) as fluorescent probe. The fluorescence of the nanoclusters was strongly quenched by bilirubin in a concentration dependent manner by virtue of the inherent specific interaction between bilirubin and HSA. A strong binding constant of 0.55×10(6) L mole(-1) between the HSA-AuNC and bilirubin was discerned. The nano clusters each with size ~1.0 nm (in diameter) and a core of Au18 were homogeneously distributed in HSA molecules as revealed from the respective high resolution transmission electron microscopic and mass spectroscopic studies. The fluorescence quenching phenomena which obeyed a simple static quenching mechanism, was utilized for interference free detection of bilirubin with minimum detection limit (DL) of 248±12 nM (S/N=3). The fluorescence response of HSA-AuNCs against bilirubin was practically unaltered over a wide pH (6-9) and temperature (25-50 °C) range. Additionally, peroxidase-like catalytic activity of these nanoclusters was exploited for colorimetric detection of bilirubin in serum sample with a DL of 200±19 nM by following the decrease in absorbance (at ?440 nm) of the reaction and its rate constant (Kp) of 2.57±0.63 mL ?g(-1) min(-1). Both these fluorometric and colorimetric methods have been successfully used for detection of free bilirubin in blood serum samples. PMID:24752148

Santhosh, Mallesh; Chinnadayyala, Somasekhar R; Kakoti, Ankana; Goswami, Pranab

2014-09-15

191

Multifunctional oval-shaped gold-nanoparticle-based selective detection of breast cancer cells using simple colorimetric and highly sensitive two-photon scattering assay.  

PubMed

Breast cancer is the most common cancer among women, and it is the second leading cause of cancer deaths in women today. The key to the effective and ultimately successful treatment of diseases such as cancer is early and accurate diagnosis. Driven by the need, in this article, we report for the first time a simple colorimetric and highly sensitive two-photon scattering assay for highly selective and sensitive detection of breast cancer SK-BR-3 cell lines at a 100 cells/mL level using a multifunctional (monoclonal anti-HER2/c-erb-2 antibody and S6 RNA aptamer-conjugated) oval-shaped gold-nanoparticle-based nanoconjugate. When multifunctional oval-shaped gold nanoparticles are mixed with the breast cancer SK-BR-3 cell line, a distinct color change occurs and two-photon scattering intensity increases by about 13 times. Experimental data with the HaCaT noncancerous cell line, as well as with MDA-MB-231 breast cancer cell line, clearly demonstrated that our assay was highly sensitive to SK-BR-3 and it was able to distinguish from other breast cancer cell lines that express low levels of HER2. The mechanism of selectivity and the assay's response change have been discussed. Our experimental results reported here open up a new possibility of rapid, easy, and reliable diagnosis of cancer cell lines by monitoring the colorimetric change and measuring TPS intensity from multifunctional gold nanosystems. PMID:20155973

Lu, Wentong; Arumugam, Sri Ranjini; Senapati, Dulal; Singh, Anant K; Arbneshi, Tahir; Khan, Sadia Afrin; Yu, Hongtao; Ray, Paresh Chandra

2010-03-23

192

Multifunctional Oval Shape Gold Nanoparticle Based Selective Detection of Breast Cancer Cells Using Simple Colorimetric and Highly Sensitive Two-Photon Scattering Assay  

PubMed Central

Breast cancer is the most common cancer among women and it is the second leading cause of cancer deaths in women today. The key to the effective and ultimately successful treatment of diseases such as cancer is an early and accurate diagnosis. Driven by the need, in this article, we report for the first time a simple colorimetric and highly sensitive two-photon scattering assay for highly selective and sensitive detection of breast cancer SK-BR-3 cell lines in 100-cells/ml level using multifunctional (monoclonal anti-HER2/c-erb-2 antibody and S6 RNA aptamers conjugated) oval shape gold nanoparticle based nanoconjugate. When multifunctional oval shape gold nanoparticles were mixed with breast cancer SK-BR-3 cell line, a distinct color change occurs and two-photon scattering intensity increases by about 13 times. Experimental data with HaCaT non-cancerous cell line, as well as with MDA-MB-231 breast cancer cell line clearly demonstrated that our assay was highly sensitive to SK-BR-3 and it was able to distinguish from other breast cancer cell line which expresses low levels of HER-2. The mechanism of selectivity and assay’s response change, have been discussed. Our experimental results reported here open up a new possibility of rapid, easy and reliable diagnosis of cancer cell lines by monitoring the colorimetric change and measuring TPS intensity from multifunctional gold nanosystems. PMID:20155973

Lu, Wentong; Arumugam, Sri Ranjini; Senapati, Dulal; Singh, Anant K.; Arbneshi, Tahir; Yu, Sadia Afrin Khan Hongtao; Ray, Paresh Chandra

2010-01-01

193

Simple, Fast and Selective Detection of Adenosine Triphosphate at Physiological pH Using Unmodified Gold Nanoparticles as Colorimetric Probes and Metal Ions as Cross-Linkers  

PubMed Central

We report a simple, fast and selective colorimetric assay of adenosine triphosphate (ATP) using unmodified gold nanoparticles (AuNPs) as probes and metal ions as cross-linkers. ATP can be assembled onto the surface of AuNPs through interaction between the electron-rich nitrogen atoms and the electron-deficient surface of AuNPs. Accordingly, Cu2+ ions induce a change in the color and UV/Vis absorbance of AuNPs by coordinating to the triphosphate groups and a ring nitrogen of ATP. A detection limit of 50 nM was achieved, which is comparable to or lower than that achievable by the currently used electrochemical, spectroscopic or chromatographic methods. The theoretical simplicity and high selectivity reported herein demonstrated that AuNPs-based colorimetric assay could be applied in a wide variety of fields by rationally designing the surface chemistry of AuNPs. In addition, our results indicate that ATP-modified AuNPs are less stable in Cu2+, Cd2+ or Zn2+-containing solutions due to the formation of the corresponding dimeric metal-ATP complexes. PMID:23202201

Deng, Dehua; Xia, Ning; Li, Sujuan; Xu, Chunying; Sun, Ting; Pang, Huan; Liu, Lin

2012-01-01

194

Highly selective colorimetric detection and estimation of Hg2+ at nano-molar concentration by silver nanoparticles in the presence of glutathione  

NASA Astrophysics Data System (ADS)

The present study investigated the colorimetric detection of mercury (Hg2+) ions by using silver nanoparticles (Ag NPs) in the presence of glutathione. The nanoparticles used in the study were synthesized biologically by using Polyalthia longifolia leaf extract. The synthesized nanoparticles were characterized by UV-visible spectrophotometer, transmission electron microscope, X-ray diffraction, particle size analyzer and zeta sizer. The particles were spherical in shape and it possesses the effective diameter of 5 nm. The zeta potential of the particles was determined to be -28.6 mV. Ag NPs-glutathione conjugates were able to detect Hg2+ in nanomolar level. Ag NPs-glutathione conjugates upon interaction with Hg2+ changes from yellowish brown to pale yellow and finally colorless. The study may be applied for the qualitative and quantitative estimation of mercury at very low concentration.

Alam, Ayesha; Ravindran, Aswathy; Chandran, Preethy; Sudheer Khan, S.

2015-02-01

195

Direct, Rapid, and Label-Free Detection of Enzyme-Substrate Interactions in Physiological Buffers Using CMOS-Compatible  

E-print Network

detection mostly include colorimetric, fluorometric, chromatographic, and radioactive assays, which either to synthesize but may alter its interaction with the enzyme. Other methods based on electrochemical assays have

Reed, Mark

196

Colorimetric dosimeter  

SciTech Connect

A gas dosimeter comprises a strip substrate coated or impregnated with a color-changing reagent; the strip is disposed lengthwise in a transparent tube, one end of which is openable and is spaced by a diffusion path from one end of the strip. When the dosimeter tube is opened and exposed to the atmosphere containing detectable gas, a color change develops lengthwise of the strip dependent on the dosage exposure to the gas.

McConnaughey, P.W.; McKee, E.S.

1982-09-07

197

Rapid colorimetric sensing of tetracycline antibiotics with in situ growth of gold nanoparticles.  

PubMed

A colorimetric assay utilizing the formation of gold nanoparticles was developed to detect tetracycline antibiotics in fluidic samples. Tetracycline antibiotics showed the capability of directly reducing aurate salts into atomic gold which form gold nanoparticles spontaneously under proper conditions. The resulted gold nanoparticles showed characteristic plasmon absorbance at 526 nm, which can be visualized by naked eyes or with a spectrophotometer. UV-vis absorbance of the resulted gold nanoparticles is correlated directly with the concentrations of tetracycline antibiotics in the solution, allowing for quantitative colorimetric detection of tetracycline antibiotics. Reaction conditions, such as pH, temperature, reaction time, and ionic strength were optimized. Sensitivity of the colorimetric assay can be enhanced by the addition of gold nanoparticle seeds, a LOD as low as 20 ng mL(-1) can be achieved with the help of seed particles. The colorimetric assay showed minimum interference from ethanol, methanol, urea, glucose, and other antibiotics such as sulfonamides, amino glycosides etc. Validity of the method was also evaluated on urine samples spiked with tetracycline antibiotics. The method provides a broad spectrum detection method for rapid and sensitive detection of reductive substances such as tetracycline antibiotics in liquid and biological samples. PMID:25066722

Shen, Li; Chen, Jing; Li, Na; He, Pingli; Li, Zhen

2014-08-11

198

Colorimetric detection with aptamer-gold nanoparticle conjugates coupled to an android-based color analysis application for use in the field.  

PubMed

The feasibility of using aptamer-gold nanoparticle conjugates (Apt-AuNPs) to design colorimetric assays for in the field detection of small molecules was investigated. An assay to detect cocaine was designed using two clones of a known cocaine-binding aptamer. The assay was based on the AuNPs difference in affinity for single-stranded DNA (non-binding) and double stranded DNA (target bound). In the first assay, a commonly used design was followed, in which the aptamer and target were incubated to allow binding followed by exposure to the AuNPs. Interactions between the non-bound analytes and the AuNPs surface resulted in a number of false positives. The assay was redesigned by incubating the AuNPs and the aptamer prior to target addition to passivate the AuNPs surface. The adsorbed aptamer was able to bind the target while preventing non-specific interactions. The assay was validated with a number of masking and cutting agents and other controlled substances showing minimal false positives. Studies to improve the assay performance in the field were performed, showing that assay activity could be preserved for up to 2 months. To facilitate the assay analysis, an android application for automatic colorimetric characterization was developed. The application was validated by challenging the assay with cocaine standards of different concentrations, and comparing the results to a conventional plate reader, showing outstanding agreement. Finally, the rapid identification of cocaine in mixtures mimicking street samples was demonstrated. This work established that Apt-AuNPs can be used to design robust assays to be used in the field. PMID:24607135

Smith, Joshua E; Griffin, Daniel K; Leny, Juliann K; Hagen, Joshua A; Chávez, Jorge L; Kelley-Loughnane, Nancy

2014-04-01

199

Molecular recognition and colorimetric detection of cholera toxin by poly(diacetylene) liposomes incorporating G{sub m1} ganglioside  

SciTech Connect

Molecular recognition sites on cell membranes serve as the main communication channels between the inside of a cell and its surroundings. Upon receptor binding, cellular messages such as ion channel opening or activation of enzymes are triggered. In this report, we demonstrate that artificial cell membranes made from conjugated lipid polymers (poly(diacetylene)) can, on a simple level, mimic membrane processes of molecular recognition and signal transduction. The ganglioside GM1 was incorporated into poly(diacetylene) liposomes. Molecular recognition of cholera toxin at the interface of the liposome resulted in a change of the membrane color due to conformational charges in the conjugated (ene-yne) polymer backbone. The `colored liposomes` might be used as simple colorimetric sensors for drug screening or as new tools to study membrane-membrane or membrane-receptor interactions. 21 refs., 3 figs.

Pan, J.J.; Charych, D. [Lawrence Berkeley Lab., CA (United States)] [Lawrence Berkeley Lab., CA (United States)

1997-03-19

200

Measuring Dark Matter Distribution in Directional Direct Detection  

NASA Astrophysics Data System (ADS)

Direct detection of dark matter with directional sensitivity offers not only measurement of both recoil energy and direction of dark matter, but also a way to understand dark matter distribution in the Galaxy. Maxwell distribution is usually supposed as the distribution near the Earth, however, result of N-body simulations suggest deviation from that due to tidal stream in the Galaxy. We explore the possibility of distinguishing the distribution by direct detection using nuclear emulsions.

Nagao, Keiko I.

2013-12-01

201

Specific detection of reverse transcription-loop-mediated isothermal amplification amplicons for Taura syndrome virus by colorimetric dot-blot hybridization.  

PubMed

The goal of this study was to develop a field diagnosis system based on isothermal reverse transcription-loop-mediated amplification (RT-LAMP) for shrimp Taura syndrome virus (TSV), placing emphasis on specific and simple detection of the LAMP amplicons. After a single-tube RT-LAMP reaction for TSV was established, colorimetric dot-blot hybridization (DBH) was adopted to detect signals only from the target-derived amplicons. The results showed that the modified DBH offered unambiguous and sensitive detection of the TSV RT-LAMP amplicons without the UV cross-linking and denaturation steps. Together, TSV RT-LAMP-DBH assay reached the same dilution point as reverse transcription-nested polymerase chain reaction-agarose gel electrophoresis (RT-nPCR-AGE) for TSV detection. Specificity of the assay was demonstrated by the absence of DBH signal from yeast tRNA and various shrimp viruses. TSV RT-LAMP-DBH was applied to 125 Penaeus vannamei and demonstrated a very good concordance (kappa value, 0.823) with RT-nPCR-AGE assay in detection efficiency. Furthermore, a one-step guanidinium thiocyanate (GuSCN) homogenization method was established to provide RNA extraction efficiency comparable to that of the TRIzol Reagent for RT-LAMP. Requiring simply a heating apparatus, the GuSCN RNA extraction-isothermal RT-LAMP-DBH protocol has the potential for further development for diagnosis of diseases in the field. PMID:17868915

Teng, Ping-Hua; Chen, Chu-Liang; Sung, Ping-Feng; Lee, Fu-Chun; Ou, Bor-Rung; Lee, Pei-Yu

2007-12-01

202

Highly sensitive colorimetric detection of Hg(II) and Cu(II) in aqueous solutions: from amino acids toward solid platforms.  

PubMed

A chemosensor () based on an amino acid with 7-nitro-2,1,3-benzoxadiazole was used for selective detection of Hg(II) and Cu(II) among 15 metal ions in aqueous solutions by a colorimetric change. sensitively differentiated Hg(II) and Cu(II) in aqueous solutions by a color change; a pink color for Hg(II) and an orange color for Cu(II). showed nanomolar detection limits for Hg(II) (176 nM, R(2) = 0.996) and Cu(II) (163 nM, R(2) = 0.996). The detection limit for Cu(II) was much lower than the maximum allowable level of Cu(II) in drinking water recommended by the U.S. EPA. The binding mode study showed that deprotonation of the NH group of played a critical role in the binding and sensing of metal ions. immobilized on PEG-PS resin maintained the potent binding affinity and sensing ability for the metal ions. The resin with was recyclable for the detection of metal ions in 100% aqueous solutions. PMID:25471472

Park, Jooyoung; In, Byunggyu; Neupane, Lok Nath; Lee, Keun-Hyeung

2014-12-01

203

Colorimetric and dynamic light scattering detection of DNA sequences by using positively charged gold nanospheres: a comparative study with gold nanorods  

NASA Astrophysics Data System (ADS)

We introduce a new genosensing approach employing CTAB (cetyltrimethylammonium bromide)-coated positively charged colloidal gold nanoparticles (GNPs) to detect target DNA sequences by using absorption spectroscopy and dynamic light scattering. The approach is compared with a previously reported method employing unmodified CTAB-coated gold nanorods (GNRs). Both approaches are based on the observation that whereas the addition of probe and target ssDNA to CTAB-coated particles results in particle aggregation, no aggregation is observed after addition of probe and nontarget DNA sequences. Our goal was to compare the feasibility and sensitivity of both methods. A 21-mer ssDNA from the human immunodeficiency virus type 1 HIV-1 U5 long terminal repeat (LTR) sequence and a 23-mer ssDNA from the Bacillus anthracis cryptic protein and protective antigen precursor (pagA) genes were used as ssDNA models. In the case of GNRs, unexpectedly, the colorimetric test failed with perfect cigar-like particles but could be performed with dumbbell and dog-bone rods. By contrast, our approach with cationic CTAB-coated GNPs is easy to implement and possesses excellent feasibility with retention of comparable sensitivity—a 0.1 nM concentration of target cDNA can be detected with the naked eye and 10 pM by dynamic light scattering (DLS) measurements. The specificity of our method is illustrated by successful DLS detection of one-three base mismatches in cDNA sequences for both DNA models. These results suggest that the cationic GNPs and DLS can be used for genosensing under optimal DNA hybridization conditions without any chemical modifications of the particle surface with ssDNA molecules and signal amplification. Finally, we discuss a more than two-three-order difference in the reported estimations of the detection sensitivity of colorimetric methods (0.1 to 10-100 pM) to show that the existing aggregation models are inconsistent with the detection limits of about 0.1-1 pM DNA and that other explanations should be developed.

Pylaev, T. E.; Khanadeev, V. A.; Khlebtsov, B. N.; Dykman, L. A.; Bogatyrev, V. A.; Khlebtsov, N. G.

2011-07-01

204

Design and characterization of a recombinant colorimetric SAG1-alkaline phosphatase conjugate to detect specific antibody responses against Toxoplasma gondii.  

PubMed

The purpose of this study was to design a novel in vitro tool by using recombinant protein technology to detect specific antibody responses against Toxoplasma gondii in a simple, rapid and highly sensitive reagent. The surface T. gondii SAG1 protein is an important immunodominant target, which provides a great interest as a diagnostic antigen. To further exploit its immunodetection capacity, in the present study, the full length sag1 gene was inserted into the pLIP6 prokaryotic expression vector so as to produce a SAG1 antigen genetically fused to the bacterial alkaline phosphatase (AP). After expression optimization, the recombinant fusion protein folded correctly in soluble form in the periplasmic space and preserved both the AP enzymatic activity and the SAG1 immunoreactivity. Subsequently, direct-ELISA and dot-blot immunoassays were designed, using crude preparation SAG1-AP conjugate, to explore its value in serodiagnosis of human toxoplasmosis. We demonstrate that the recombinant SAG1-AP can detect specific T. gondii antibodies in one-step procedure and can successfully discriminate between T. gondii immune and non-immune patients, in agreement with the standard gold test. In conclusion, the present study shows that the genetic fusion protein provides a new tool for one-step T. gondii immunodetection, which was easily, quickly and reproducibly produced as homogeneous bi-functional reagent. Thus, this recombinant immunoconjugate is a promising marker for Toxoplasma serodiagnosis, requiring further evaluation on a larger series and could provide the basis for direct antibody capture enzyme-immunoassay for specific immunoglobulin M and G detection. PMID:23727049

Chahed Bel-Ochi, Nouha; Bouratbine, Aïda; Mousli, Mohamed

2013-08-30

205

Measurement of seawater pCO[sub 2] using a renewable-reagent fiber optic sensor with colorimetric detection  

SciTech Connect

A new method, based on a renewable-reagent fiber optic sensor, for measuring the partial pressure of CO[sub 2] (pCO[sub 2]) in seawater is presented. The sensor operates by measuring the light intensity at the absorbing wavelengths of a colorimetric acid-base indicator which is continuously delivered to the fiber tips through capillary tubing. The light intensity is modulated by pH changes that occur when CO[sub 2] diffuses across a gas-permeable membrane. The sensor operates both in a diffusion-dependent steady state and equilibrium regime depending upon the indicator flow rate. At low flow rates, an equilibrium model can be used to predict the response of the sensor. The results indicate that the sensor operates within the steady-state regime at flow rates higher than approximately 0.2 [mu]L/min. The optimal precision is [+-]0.8 [mu]atm from 300--550 [mu]atm of CO[sub 2], calculated from the response sensitivity and 3[times] the root mean square noise. Response times (100%) range from 11 to 28 min and depend upon the indicator flow rate. Sensitivity to temperature and sample hydrodynamics is also discussed. The sensor performance was tested on a research cruise, and these results are compared to the underway pCO[sub 2] measured simultaneously by an infrared CO[sub 2] analyzer. 18 refs., 8 figs., 2 tabs.

DeGrandpre, M.D. (Woods Hole Oceanographic Inst., MA (United States))

1993-02-15

206

A colorimetric sensor array of porous pigments Sung H. Lim,a  

E-print Network

A colorimetric sensor array of porous pigments Sung H. Lim,a Jonathan W. Kemling,b Liang Fengb colorimetric sensor array capable of the detection and identification of toxic gases is reported different, but quite simple, optoelectronic approach using a colorimetric sensor array of chemically

Suslick, Kenneth S.

207

DATA REPRESENTATION AND FEATURE SELECTION FOR COLORIMETRIC SENSOR ARRAYS USED AS EXPLOSIVES DETECTORS  

E-print Network

DATA REPRESENTATION AND FEATURE SELECTION FOR COLORIMETRIC SENSOR ARRAYS USED AS EXPLOSIVES of Denmark, we are developing a colorimetric sensor array which can be useful for detection of explosives of water vapor in air. In order to analyze colorimetric sen- sors with statistical methods, the sensory

208

A colorimetric sensor array for identification of toxic gases below permissible exposure limitsw  

E-print Network

A colorimetric sensor array for identification of toxic gases below permissible exposure limitsw Article on the web 11th February 2010 DOI: 10.1039/b926848k A colorimetric sensor array has been developed and of course colorimetric detectors tailored to specific single analytes.2 Most such detection technologies

Suslick, Kenneth S.

209

DOI: 10.1002/anie.200905570 An Aptamer Cross-Linked Hydrogel as a Colorimetric  

E-print Network

as a Colorimetric Platform for Visual Detection** Zhi Zhu, Cuichen Wu, Haipeng Liu, Yuan Zou, Xiaoling Zhang cost, rapidity, and simplicity are essential. A variety of colorimetric reagents, such as visible dyes-consuming manipulation and sophisticated instru- ments. Herein, we propose a colorimetric agent-caging hydrogel

Tan, Weihong

210

Doped colorimetric assay liposomes  

DOEpatents

The present invention provides compositions comprising colorimetric assay liposomes. The present invention also provides methods for producing colorimetric liposomes and calorimetric liposome assay systems. In preferred embodiments, these calorimetric liposome systems provide high levels of sensitivity through the use of dopant molecules. As these dopants allow the controlled destabilization of the liposome structure, upon exposure of the doped liposomes to analyte(s) of interest, the indicator color change is facilitated and more easily recognized.

Charych, Deborah (Albany, CA); Stevens, Raymond C. (Albany, CA)

2001-01-01

211

A simple green route to prepare stable silver nanoparticles with pear juice and a new selective colorimetric method for detection of cysteine.  

PubMed

In this work, a new cost-effective, rapid and simple method for the preparation of stable silver nanoparticles (AgNPs) was developed, which can be completed within 15 minutes at room temperature by oxidizing the reductants in pear juice with AgNO3. Compared with the most used citrate-capped AgNPs, the as-prepared AgNPs showed high stability, good biocompatibility and enhanced antibacterial activity. Based on the formation of Ag-S covalent bonds between cysteine and AgNPs as well as the electrostatic interaction of COO(-) and NH4(+) between cysteine molecules, which selectively lead to the aggregation of the as-prepared AgNPs and give a specific yellow-to-red colour change, a new selective colorimetric method for detection of cysteine was proposed with the as-prepared AgNPs by coupling the decrease of the characteristic localized surface plasmon resonance (LSPR) absorption at 406 nm of the as-prepared AgNPs and the increase of the new aggregation-induced band at 530 nm. The ratio of the absorbance at 530 nm to 406 nm (A530/A406) was found to be linearly dependent on the cysteine concentrations in the range of 5.0 × 10(-7) to 1.0 × 10(-5) M with a limit of detection of 6.8 × 10(-8) M. PMID:23869382

Huang, Jing Tao; Yang, Xiao Xi; Zeng, Qiao Ling; Wang, Jian

2013-09-21

212

Highly selective colorimetric detection of spermine in biosamples on basis of the non-crosslinking aggregation of ssDNA-capped gold nanoparticles.  

PubMed

The selective adsorption of single-stranded oligonucleotides (ssDNA) on gold nanoparticles (AuNPs) is well known for stabilizing the AuNPs against aggregation even at high salt concentrations. Our investigation shows that the non-crosslinking aggregation of arbitrary ssDNA-capped AuNPs occurs due to their interaction with the cationic polyamine, spermine (Spm), even without any addition of NaCl. The non-crosslinking aggregation mechanism is that the Spm, served as multivalent counterions, plays the dual roles of charge shielding and ion bridging among the ssDNA-capped AuNPs, which jointly result in the aggregation of the ssDNA-capped AuNPs. Therefore, a sensitive and highly selective colorimetric method for the detection of Spm was developed. To the best of our knowledge, it is the first successful case as to the efforts towards the development of optical assays for cationic polyamine, showing neither natural UV absorption nor fluorescence. Compared with the traditional methods of chromatography and capillary electrophoresis, the approach described here would provide a convenient alternative and new train of thought for the specific detection of Spm in both biological fluid and fermented products. PMID:23598125

Liu, Zhong De; Zhu, Hai Yan; Zhao, Heng Xin; Huang, Cheng Zhi

2013-03-15

213

Synthesis, characterization and application of poly(acrylamide-co-methylenbisacrylamide) nanocomposite as a colorimetric chemosensor for visual detection of trace levels of Hg and Pb ions.  

PubMed

In this study, a new colorimetric chemosensor based on TiO2/poly(acrylamide-co-methylenbisacrylamide) nanocomposites was designed for determination of mercury and lead ions at trace levels in environmental samples. The removal and preconcentration of lead and mercury ions on the sorbent was achieved due to sharing an electron pair of N and O groups of polymer chains with the mentioned heavy metal ions. The hydrogel sensor was designed by surface modification of a synthesized TiO2 nanoparticles using methacryloxypropyltrimethoxysilan (MAPTMS), which provided a reactive CC bond that polymerized the acrylamide and methylenbisacrylamide. The sorbent was characterized using X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscope (SEM), EDS analysis and Fourier transform in frared (FT-IR) spectrometer. This nanostructured composite with polymer shell was developed as a sensitive and selective sorbent for adsorption of mercury and lead ions from aqueous solution at optimized condition. This method involves two-steps: (1) preconcentration of mercury and lead ions by the synthesized sorbent and (2) its selective monitoring of the target ions by complexation with dithizone (DZ). The color of the sorbent in the absence and presence of mercury and lead ions shifts from white to violet and red, respectively. The detection limit of the synthesized nanochemosensor for mercury and lead ions was 1 and 10?gL(-1), respectively. The method was successfully applied for trace detection of mercury and lead ions in tap, river, and sea water samples. PMID:25497023

Sedghi, Roya; Heidari, Bahareh; Behbahani, Mohammad

2015-03-21

214

Ni(II)NTA AuNPs as a low-resource malarial diagnostic platform for the rapid colorimetric detection of Plasmodium falciparum Histidine-Rich Protein-2.  

PubMed

Diagnosing infectious diseases remains a challenge in the developing world where there is a lack of dependable electricity, running water, and skilled technicians. Although rapid immunochromatographic tests (RDTs) have been deployed to diagnose diseases such as malaria, the extreme climate conditions encountered in these regions compounded with the discrepancies in test manufacturing have yielded varying results, so that more innovative and robust technologies are sought. Devoid of antibodies and thermally sensitive materials, we present a robust, colorimetric diagnostic platform for the detection of a malarial biomarker, Plasmodium falciparum Histidine-Rich Protein 2 (PfHRP-II). The assay exploits the optical properties of gold nanoparticles, covalently coupling them to a Ni(II)NTA recognition element specific for PfHRP-II. In the presence of the recombinant malarial biomarker (rcHRP-II), the Ni(II)NTA AuNPs begin to crosslink and aggregate in as little as one minute, triggering a red-to-purple color change in solution. To increase assay sensitivity and platform stability suitable for low-resource regions, the Ni(II)NTA AuNPs were assembled with varying spacer ligands in a mixed monolayer presentation. When assembled with a negatively charged Peg4-thiol ligand, the Ni(II)NTA AuNPs demonstrate low nanomolar limits of rcHRP-II detection in physiological concentrations of human serum albumin and maintain excellent stability at 37°C when stored for four weeks. Detection of the malaria biomarker is also measured by capturing and processing images of aggregated gold nanoparticles with a smartphone camera. By utilizing a smartphone camera and image processing application, there is no significant difference in assay sensitivity and rcHRP-II limit of detection in comparison to a spectrophotometer, further making this diagnostic platform applicable for use in low-resource regions. PMID:25640131

Gulka, Christopher P; Swartz, Joshua D; Wright, David W

2015-04-01

215

A Colorimetric Bioassay for Perchlorate  

NASA Astrophysics Data System (ADS)

Recognition of perchlorate (ClO4-) as a widespread contaminant across the United States and its potential adverse affects towards human health has motivated the EPA to place ClO4- on its contaminant candidate list for drinking water supplies. While a federal MCL has not yet been set, a recommended public health goal of 1 ppb (?g.L-1) was established by the US EPA in 2002. To date, methods of detection require use of sensitive ion chromatographic equipment that are expensive, time consuming, and require highly trained personnel for use. Our studies are focused on the development of a highly sensitive, simple, and robust colorimetric bioassay based on the primary enzyme involved in microbial ClO4- reduction, the perchlorate reductase (Pcr). A previously published assay used reduced methyl viologen (MV, the dye is reduced with sodium hydrosulfite) as an electron donor to demonstrate Pcr activity. The assay directly correlates the amount of MV oxidized with the amount of ClO4- reduced by assuming a transfer of four electrons. To test this assumption, we compared actual concentrations of MV oxidized to ClO4- reduced in this assay. ClO4- concentrations were determined using a Dionex ICS-500 ion chromatography system, while MV concentrations were determined using a standard curve generated at 578 nm. Comparisons between the two revealed that twelve molecules of MV were oxidized for each molecule of ClO4- reduced. The oxidation of these additional eight MV molecules is explained by the interaction of the dye with chlorite (the product of the Pcr reaction) and other contaminants that could be present in the enzyme prep. This unsettling result indicated this assay would be problematic for the detection of ClO4- in soil, which has many chemicals that could react with MV. To improve upon this assay, we have tried to reduce ClO4- using less reactive dyes and reductants. The reductants ascorbic acid, NADH, and dithiothreitol drive Pcr catalyzed ClO4- reduction, however, they are not effective unless an accompanying dye is used as a shuttle. N-methylphenazinium methosulfate (PMS) was selected as the most suitable dye because of its interaction with NADH, an oxygen stable reductant. In addition, the positive redox potential of PMS (E°' = +80 mV), makes it significantly less reactive than MV (E°' = -450 mV). A comparison of actual concentrations of ClO4- reduced vs. NADH oxidized show exactly four molecules of NADH oxidized for each molecule of ClO4- that is reduced (8 electrons). These studies have resulted in the successful development of a method that can accurately determine ClO4- concentrations with a small error using the enzyme Pcr and indicate the great potential for the ultimate development of a simple, robust, and highly sensitive colorimetric bioassay for perchlorate that can be widely used to screen laboratory and environmental samples .

Heinnickel, M. L.; Smith, S.; Coates, J. D.

2007-12-01

216

Facile synthesis of enzyme-inorganic hybrid nanoflowers and its application as a colorimetric platform for visual detection of hydrogen peroxide and phenol.  

PubMed

This study reports a facile approach for the synthesis of horseradish peroxidise (HRP)-inorganic hybrid nanoflowers by self-assembly of HRP and copper phosphate (Cu3(PO4)2·3H2O) in aqueous solution. Several reaction parameters that affect the formation of the hybrid nanoflowers were investigated and a hierarchical flowerlike spherical structure with hundreds of nanopetals was obtained under the optimum synthetic conditions. The enzymatic activity of HRP embedded in hybrid naonflowers was evaluated based on the principle of HRP catalyzing the oxidation of o-phenylenediamine (OPD) in the presence of hydrogen peroxide (H2O2). The results showed that 506% enhancement of enzymatic activity in the hybrid nanoflowers could be achieved compared with the free HRP in solution. Taking advantages of the structural feature with catalytic property, a nanoflower-based colorimetric platform was newly designed and applied for fast and sensitive visual detection of H2O2 and phenol. The limits of detection (LODs) for H2O2 and phenol were as low as 0.5 ?M and 1.0 ?M by the naked-eye visualization, which meet the requirements of detection of both analytes in clinical diagnosis and environmental water. The proposed method has been successfully applied to the analysis of low-level H2O2 in spiked human serum and phenol in sewage, respectively. The recoveries for all the determinations were higher than 92.6%. In addition, the hybrid nanoflowers exhibited excellent reusability and reproducibility in cycle analysis. These primary results demonstrate that the hybrid nanoflowers have a great potential for applications in biomedical and environmental chemistry. PMID:24937087

Lin, Zian; Xiao, Yun; Yin, Yuqing; Hu, Wenli; Liu, Wei; Yang, Huanghao

2014-07-01

217

Quantitative method for colorimetric determination of formate in fermentation media  

SciTech Connect

The effect of fermentation products and media supplements on a colorimetric assay for formate were evaluated. Formate was detected at concentrations as low as 0.5 mM in fermentation media. 10 references, 1 figure, 2 tables.

Sleat R.; Mah, R.A.

1984-04-01

218

ORIGINAL ARTICLE Colorimetric / fluorescent bacterial sensing by agarose-  

E-print Network

and fluorescence transformations in response to bacterial growth. The sensing constructs comprise glassORIGINAL ARTICLE Colorimetric / fluorescent bacterial sensing by agarose- embedded lipid The development of simple and rapid bacterial detection techniques is drawing intense scientific and technological

Jelinek, Raz

219

ORIGINAL ARTICLE Colorimetric / fluorescent bacterial sensing by agarose-  

E-print Network

in response to bacterial growth. The sensing constructs comprise glass-supported LangmuirORIGINAL ARTICLE Colorimetric / fluorescent bacterial sensing by agarose- embedded lipid The development of simple and rapid bacterial detection techniques is drawing intense scientific and technological

Jelinek, Raz

220

Colorimetric detection of mercury(II) in a high-salinity solution using gold nanoparticles capped with 3-mercaptopropionate acid and adenosine monophosphate.  

PubMed

A new colorimetric sensor for sensing Hg2+ in a high-salinity solution has been developed using gold nanoparticles (AuNPs) decorated with 3-mercaptopropionate acid (MPA) and adenosine monophosphate (AMP). Because of the high negative charge density of AMP on each AuNP surface, MPA/AMP-capped AuNPs are well dispersed in a high-salt solution. In contrast, the aggregation of MPA-capped AuNPs was induced by sodium ions, which shield the negative charges of the carboxylic groups of MPA. Through the coordination between the carboxylic group of MPA and Hg2+, the selectivity of MPA/AMP-capped AuNPs for Hg2+ in a high-salt solution is remarkably high over that of the other metals without the addition of a masking agent or a change in the temperature. We have carefully investigated the effect of the AMP concentration on the stability and sensitivity of MPA/AMP-capped AuNPs. Under optimum conditions, the lowest detectable concentration of Hg2+ using this probe was 500 nM on the basis of the measurement of the ratio of absorption at 620 nm to that at 520 nm. The sensitivity to Hg2+ can be further improved by modifying the MPA/AMP-capped AuNPs with highly fluorescent rhodamine 6G (R6G). By monitoring the fluorescence enhancement, the lowest detectable concentration of Hg2+ using R6G/MPA/AMP-capped AuNPs was 50 nM. PMID:18839969

Yu, Cheng-Ju; Tseng, Wei-Lung

2008-11-01

221

A FRET-based ratiometric fluorescent and colorimetric probe for the facile detection of organophosphonate nerve agent mimic DCP.  

PubMed

A FRET ratiometric fluorescent probe enabling a fast and highly sensitive response to OP nerve agent mimic DCP within 1 min and with as low as 0.17 ppm concentration detection limit has been developed. Moreover, the probe exhibits noticeable color changes under UV light and even with the naked eye. It is also demonstrated that it can detect both liquid and gas nerve agents. PMID:24080856

Xuan, Weimin; Cao, Yanting; Zhou, Jiahong; Wang, Wei

2013-11-18

222

A label free colorimetric assay for the detection of active botulinum neurotoxin type A by SNAP-25 conjugated colloidal gold.  

PubMed

Botulinum neurotoxins are one of the most potent toxins known to man. Current methods of detection involve the quantification of the toxin but do not take into account the percentage of the toxin that is active. At present the assay used for monitoring the activity of the toxin is the mouse bioassay, which is lengthy and has ethical issues due to the use of live animals. This report demonstrates a novel assay that utilises the endopeptidase activity of the toxin to detect Botulinum neurotoxin in a pharmaceutical sample. The cleaving of SNAP-25 is monitored via UV-Visible spectroscopy with a limit of detection of 373 fg/mL and has been further developed into a high throughput method using a microplate reader detecting down to 600 fg/mL of active toxin. The results show clear differences between the toxin product and the placebo, which contains the pharmaceutical excipients human serum albumin and lactose, showing that the assay detects the active form of the toxin. PMID:23925142

Halliwell, Jennifer; Gwenin, Christopher

2013-08-01

223

A ratiometric colorimetric detection of the folate receptor based on terminal protection of small-molecule-linked DNA.  

PubMed

Development of strategies for the sensitive and selective detection of the folate receptor (FR) that are simple and low cost is of great importance for assessing cancer therapeutics due to its crucial role in physiological, pharmacological and pathological processes. In this paper, gold nanoparticle (AuNP)-based novel ratiometric colorimetry for the detection of the folate receptor (FR) is proposed based on terminal protection of small-molecule-linked DNA. The single-stranded DNA (ssDNA) terminally tethered to folic acid (FA) is protected from degradation by exonuclease I (Exo I) when the FA moiety is bound to FR. The hybridization between FR-protected DNA and DNA-functionalized Au NPs generated a red-to-purple colour change, allowing the visual detection of FR. The detection limit of FR can be as low as 0.33 ng mL(-1) with the naked eye. It provides a promising strategy for visual detection of the binding event of FA to its protein receptor-FR with advantages such as simplicity, high selectivity, and a wide linear range. PMID:25553613

Zhu, Yanhong; Wang, Guangfeng; Sha, Liang; Qiu, Yuwei; Jiang, Hong; Zhang, Xiaojun

2015-02-01

224

A Label Free Colorimetric Assay for the Detection of Active Botulinum Neurotoxin Type A by SNAP-25 Conjugated Colloidal Gold  

PubMed Central

Botulinum neurotoxins are one of the most potent toxins known to man. Current methods of detection involve the quantification of the toxin but do not take into account the percentage of the toxin that is active. At present the assay used for monitoring the activity of the toxin is the mouse bioassay, which is lengthy and has ethical issues due to the use of live animals. This report demonstrates a novel assay that utilises the endopeptidase activity of the toxin to detect Botulinum neurotoxin in a pharmaceutical sample. The cleaving of SNAP-25 is monitored via UV-Visible spectroscopy with a limit of detection of 373 fg/mL and has been further developed into a high throughput method using a microplate reader detecting down to 600 fg/mL of active toxin. The results show clear differences between the toxin product and the placebo, which contains the pharmaceutical excipients human serum albumin and lactose, showing that the assay detects the active form of the toxin. PMID:23925142

Halliwell, Jennifer; Gwenin, Christopher

2013-01-01

225

Pd/V.sub.2O.sub.5 device for colorimetric H.sub.2 detection  

DOEpatents

A sensor structure for chemochromic optical detection of hydrogen gas over a wide response range, that exhibits stability during repeated coloring/bleaching cycles upon exposure and removal of hydrogen gas, comprising: a glass substrate (20); a vanadium oxide layer (21) coated on the glass substrate; and a palladium layer (22) coated on the vanadium oxide layer.

Liu, Ping (San Diego, CA); Tracy, C. Edwin (Golden, CO); Pitts, J. Roland (Lakewood, CO); Smith, II, R. Davis (Golden, CO); Lee, Se-Hee (Lakewood, CO)

2008-09-02

226

Disentangling Dark Matter Dynamics with Directional Detection  

SciTech Connect

Inelastic dark matter reconciles the DAMA anomaly with other null direct detection experiments and points to a non-minimal structure in the dark matter sector. In addition to the dominant inelastic interaction, dark matter scattering may have a subdominant elastic component. If these elastic interactions are suppressed at low momentum transfer, they will have similar nuclear recoil spectra to inelastic scattering events. While upcoming direct detection experiments will see strong signals from such models, they may not be able to unambiguously determine the presence of the subdominant elastic scattering from the recoil spectra alone. We show that directional detection experiments can separate elastic and inelastic scattering events and discover the underlying dynamics of dark matter models.

Lisanti, Mariangela; Wacker, Jay G.; /SLAC

2009-12-16

227

Directional detection of dark matter streams  

NASA Astrophysics Data System (ADS)

Directional detection of weakly interacting massive particles, in which the energies and directions of the recoiling nuclei are measured, currently presents the only prospect for probing the local velocity distribution of Galactic dark matter. We investigate the extent to which future directional detectors would be capable of probing dark matter substructure in the form of streams. We analyze the signal expected from a Sagittarius-like stream and also explore the full parameter space of stream speed, direction, dispersion and density. Using a combination of nonparametric directional statistics, a profile likelihood ratio test and Bayesian parameter inference we find that within acceptable exposure times [O (10 ) kg yr for cross sections just below the current exclusion limits] future directional detectors will be sensitive to a wide range of stream velocities and densities. We also examine and discuss the importance of the energy window of the detector.

O'Hare, Ciaran A. J.; Green, Anne M.

2014-12-01

228

Specific and sensitive colorimetric detection of Al3+ using 5-mercaptomethyltetrazole capped gold nanoparticles in aqueous solution.  

PubMed

Contamination of food and drinking water by health-risk levels of Al(3+) calls for convenient assays. Here, we report a method to visibly detect Al(3+) at room temperature. Firstly, the chelating ligand of 5-mercaptomethyltetrazole (MMT) was synthesized and modified on the surface of AuNPs through the strong Au-S interaction to form a MMT-AuNP probe, which can remain well-dispersed and stable in an aqueous solution for a long time. Upon the addition of Al(3+), the interparticle crosslinking induced aggregation (color change from red to blue) of MMT-AuNPs was triggered through the Al(3+)-MMT interaction. Under optimal conditions, the absorbance ratio (A620/A520) of MMT-AuNPs is linear within the Al(3+) concentration range from 1.0 to 10.0 ?M, and the detection limit (3?) was as low as 0.53 ?M. Moreover, an interference study showed that this MMT-AuNP probe discriminated Al(3+) from a wide range of environmentally dominant metal ions and anions. The practical utility of the new method was demonstrated by determining Al(3+) in several environmental water and human urine specimens, obtaining satisfactory results. Being a rapid, convenient and cost-effective method, it should become a powerful alternative to conventional methods for selective quantification of Al(3+) in routine laboratory practice or rapid on-site assay. PMID:24401419

Xue, Dingshuai; Wang, Hongyue; Zhang, Yanbin

2014-02-01

229

A direct optical immunosensor for atrazine detection  

Microsoft Academic Search

Immunoanalytical techniques represent one of the most important applications of biomolecules in analytical procedures. Direct monitoring of immunoreactions by an analytical device is a particularly attractive approach to environmental sensing as it offers speed, a simple test scheme and does not require labelled compounds. Target limits of detection for pesticides are imposed by the EU drinking water act (0.1 ?g\\/l

Andreas Brecht; Jacob Piehler; Gerd Lang; Günter Gauglitz

1995-01-01

230

Direct detection of dark matter axions with directional sensitivity  

SciTech Connect

We study the directional effect of the expected axion dark matter signal in a resonant cavity of an axion haloscope detector, for cavity geometries not satisfying the condition that the axion de Broglie wavelength ?{sub a} is sufficiently larger than the cavity dimensions L for a fully coherent conversion, i.e. ?{sub a}?>2?L. We focus on long thin cavities immersed in dipole magnets and find, for appropriately chosen cavity lengths, an O(1) modulation of the signal with the cavity orientation with respect the momentum distribution of the relic axion background predicted by the isothermal sphere model for the galactic dark matter halo. This effect can be exploited to design directional axion dark matter detectors, providing an unmistakable signature of the extraterrestrial origin of a possible positive detection. Moreover, the precise shape of the modulation may give information of the galactic halo distribution and, for specific halo models, give extra sensitivity for higher axion masses.

Irastorza, Igor G.; García, Juan A., E-mail: Igor.Irastorza@cern.ch, E-mail: jagarpas@unizar.es [Laboratorio de Física Nuclear y Astropartículas, Departamento de Física Teórica, Universidad de Zaragoza, C/ Pedro Cerbuna 12, 50009, Zaragoza (Spain)

2012-10-01

231

Direct detection of dark matter polarizability  

E-print Network

We point out that the direct detection of dark matter via its electro-magnetic polarizability is described by two new nuclear form factors, which are controlled by the 2-nucleon nuclear density. The signature manifests a peculiar dependence on the atomic and mass numbers of the target nuclei, as well as on the momentum transfer, and can differ significantly from experiment to experiment. We also discuss UV completions of our scenario.

Grigory Ovanesyan; Luca Vecchi

2014-10-02

232

Direct Detection of Exoplanets with Polarimetry  

NASA Astrophysics Data System (ADS)

The detection of scattered light from exoplanets gives direct access to physical conditions and composition of their atmospheres. Currently, most scattered light experiments focus on nearly edge-on, transiting systems. The temporal changes that occur during planetary occultations are used to suppress systematic errors that would otherwise overwhelm the planetary signal. Linear polarimetry also has the potential to detect scattered light from exoplanets, because the polarization state of light scattered by a planetary atmosphere distinguishes it from both the direct light from the host star and thermal re-radiation from the planet. This scattered flux should be identifiable even in face-on systems, because both degree and position angle of polarization are modulated continuously throughout the orbit. Orbital inclination, mean number of scattering events, and scattering particle index of refraction and size are potentially discernable with polarimetry. I will report on the search for scattered light from known exoplanets using the POLISH2 polarimeter on the Lick 3-m telescope. This instrument has recently been upgraded with simultaneous full-Stokes capability and UBV filters. This polarimeter has achieved nightly precisions at the part per million level on V < 9 stars, and systematic effects have been suppressed to this level as well. The POLISH2 polarimeter is therefore ideally suited for direct detection of close-in exoplanets. This work was supported by a UC Lab Fees Research Grant, UCO/Lick Observatory, and a NExScI Sagan Fellowship.

Wiktorowicz, Sloane

2011-09-01

233

Direct Detection of Exoplanets with Polarimetry  

NASA Astrophysics Data System (ADS)

The detection of scattered light from exoplanets gives direct access to the structure and composition of their atmospheres. Currently, most scattered light experiments focus on nearly edge-on, transiting systems. The temporal changes that occur during planetary occultations are used to suppress systematic errors that would otherwise overwhelm the planetary signal. However, linear polarimetry also has the potential to detect scattered light from exoplanets. This is because the polarization state of light scattered by a planetary atmosphere distinguishes it from both the direct light from the host star and the Wien tail of thermal re-radiation from the planet. Scattered flux should be identifiable regardless of orbital inclination, because both degree and position angle of polarization are modulated continuously throughout the orbit. Orbital inclination, mean number of scattering events, and scattering particle size and index of refraction are potentially discernable with polarimetry. I will report on the search for scattered light from known exoplanets using the POLISH2 polarimeter on the Lick 3-m telescope. This instrument simultaneously measures all four Stokes parameters (I, Q, U, and V), and it achieves precision at 2.5 times the photon shot noise limit over an entire observing run. The POLISH2 polarimeter is therefore ideally suited for direct detection of spatially unresolved exoplanets. This work is supported by a NExScI Sagan Fellowship, UC Lab Fees Research Grant, and UCO/Lick Observatory.

Wiktorowicz, Sloane

2013-01-01

234

Direct Detection of Exoplanets with Polarimetry  

NASA Astrophysics Data System (ADS)

The detection of scattered light from exoplanets gives direct access to structure and composition of their atmospheres. Currently, most scattered light experiments focus on nearly edge-on, transiting systems. The temporal changes that occur during planetary occultations are used to suppress systematic errors that would otherwise overwhelm the planetary signal. However, linear polarimetry also has the potential to detect scattered light from exoplanets. This is because the polarization state of light scattered by a planetary atmosphere distinguishes it from both the direct light from the host star and the Wien tail of thermal re-radiation from the planet. Scattered flux should be identifiable even in face-on systems, because both degree and position angle of polarization are modulated continuously throughout the orbit. Orbital inclination, mean number of scattering events, and scattering particle size and index of refraction are potentially discernable with polarimetry. We will report on the search for scattered light from known exoplanets using the POLISH2 polarimeter on the Lick 3-m telescope. This instrument simultaneously measures all four Stokes parameters (I, Q, U, and V), and it achieves precision within 60% of the photon shot noise limit over an entire observing run. The POLISH2 polarimeter is therefore ideally suited for direct detection of close-in exoplanets. This work is supported by a UC Lab Fees Research Grant, UCO/Lick Observatory, and a NExScI Sagan Fellowship.

Wiktorowicz, Sloane; Laughlin, G.

2012-01-01

235

Colorimetric elastase sensor with peptide conjugated cellulose nanocrystals is interfaced to dialysis membranes  

Technology Transfer Automated Retrieval System (TEKTRAN)

Clinical detection of human neutrophil elastase (HNE) as point of care biomarker or in situ colorimetric adjuvant to chronic wound dressings presents potential advantages in the management of chronic wounds. A colorimetric approach to the detection of HNE using cotton cellulose nanocrystals (CCN) i...

236

Simple method of detecting enteroviruses in contaminated molluscs and sewage by using polymerase chain reaction coupled with a colorimetric microwell detection assay  

Microsoft Academic Search

The methods normally used for the detection of enteroviruses in environmental [MM1]samples involve the use of cell cultures, which are expensive and time consuming. The Polymerase Chain Reaction (PCR) is a useful tool for the detection of enteroviruses in several matrixes because primary cell culture is not needed and the increased sensitivity of PCR allows detection of the low numbers

O. Gualillo; D. Biscardi; R. Di Carlo; R. De Fusco

1999-01-01

237

Aberration features in directional dark matter detection  

SciTech Connect

The motion of the Earth around the Sun causes an annual change in the magnitude and direction of the arrival velocity of dark matter particles on Earth, in a way analogous to aberration of stellar light. In directional detectors, aberration of weakly interacting massive particles (WIMPs) modulates the pattern of nuclear recoil directions in a way that depends on the orbital velocity of the Earth and the local galactic distribution of WIMP velocities. Knowing the former, WIMP aberration can give information on the latter, besides being a curious way of confirming the revolution of the Earth and the extraterrestrial provenance of WIMPs. While observing the full aberration pattern requires extremely large exposures, we claim that the annual variation of the mean recoil direction or of the event counts over specific solid angles may be detectable with moderately large exposures. For example, integrated counts over Galactic hemispheres separated by planes perpendicular to Earth's orbit would modulate annually, resulting in Galactic Hemisphere Annual Modulations (GHAM) with amplitudes larger than the usual non-directional annual modulation.

Bozorgnia, Nassim; Gelmini, Graciela B. [Department of Physics and Astronomy, UCLA, 475 Portola Plaza, Los Angeles, CA 90095 (United States); Gondolo, Paolo, E-mail: nassim@physics.ucla.edu, E-mail: gelmini@physics.ucla.edu, E-mail: paolo@physics.utah.edu [Department of Physics and Astronomy, University of Utah, 115 South 1400 East 201, Salt Lake City, UT 84112 (United States)

2012-08-01

238

Complementarity of dark matter direct detection targets  

SciTech Connect

We investigate the reconstruction capabilities of the dark matter mass and spin-independent cross section from future ton-scale direct detection experiments using germanium, xenon, or argon as targets. Adopting realistic values for the exposure, energy threshold, and resolution of dark matter experiments which will come online within 5 to 10 years, the degree of complementarity between different targets is quantified. We investigate how the uncertainty in the astrophysical parameters controlling the local dark matter density and velocity distribution affects the reconstruction. For a 50 GeV WIMP, astrophysical uncertainties degrade the accuracy in the mass reconstruction by up to a factor of {approx}4 for xenon and germanium, compared to the case when astrophysical quantities are fixed. However, the combination of argon, germanium, and xenon data increases the constraining power by a factor of {approx}2 compared to germanium or xenon alone. We show that future direct detection experiments can achieve self-calibration of some astrophysical parameters, and they will be able to constrain the WIMP mass with only very weak external astrophysical constraints.

Pato, Miguel [Institute for Theoretical Physics, University of Zuerich, Winterthurerst. 190, 8057 Zuerich CH (Switzerland); Institut d'Astrophysique de Paris, UMR 7095-CNRS, University Pierre and Marie Curie, 98bis Bd Arago 75014 Paris (France); Dipartimento di Fisica, Universita degli Studi di Padova, via Marzolo 8, I-35131, Padova (Italy); Baudis, Laura [Physics Institute, University of Zuerich, Winterthurerst. 190, 8057 Zuerich CH (Switzerland); Bertone, Gianfranco [Institute for Theoretical Physics, University of Zuerich, Winterthurerst. 190, 8057 Zuerich CH (Switzerland); Institut d'Astrophysique de Paris, UMR 7095-CNRS, University Pierre and Marie Curie, 98bis Bd Arago 75014 Paris (France); Ruiz de Austri, Roberto [Instituto de Fisica Corpuscular, IFIC-UV/CSIC, Valencia (Spain); Strigari, Louis E. [Kavli Institue for Particle Astrophysics and Cosmology, Stanford University, Stanford, California, 94305 (United States); Trotta, Roberto [Astrophysics Group, Imperial College London, Blackett Laboratory, Prince Consort Road, London SW7 2AZ (United Kingdom)

2011-04-15

239

Bayesian analysis of multiple direct detection experiments  

NASA Astrophysics Data System (ADS)

Bayesian methods offer a coherent and efficient framework for implementing uncertainties into induction problems. In this article, we review how this approach applies to the analysis of dark matter direct detection experiments. In particular we discuss the exclusion limit of XENON100 and the debated hints of detection under the hypothesis of a WIMP signal. Within parameter inference, marginalizing consistently over uncertainties to extract robust posterior probability distributions, we find that the claimed tension between XENON100 and the other experiments can be partially alleviated in isospin violating scenario, while elastic scattering model appears to be compatible with the frequentist statistical approach. We then move to model comparison, for which Bayesian methods are particularly well suited. Firstly, we investigate the annual modulation seen in CoGeNT data, finding that there is weak evidence for a modulation. Modulation models due to other physics compare unfavorably with the WIMP models, paying the price for their excessive complexity. Secondly, we confront several coherent scattering models to determine the current best physical scenario compatible with the experimental hints. We find that exothermic and inelastic dark matter are moderatly disfavored against the elastic scenario, while the isospin violating model has a similar evidence. Lastly the Bayes' factor gives inconclusive evidence for an incompatibility between the data sets of XENON100 and the hints of detection. The same question assessed with goodness of fit would indicate a 2 ? discrepancy. This suggests that more data are therefore needed to settle this question.

Arina, Chiara

2014-12-01

240

Direct Detection of Dark Matter Debris Flows  

E-print Network

Tidal stripping of dark matter from subhalos falling into the Milky Way produces narrow, cold tidal streams as well as more spatially extended "debris flows" in the form of shells, sheets, and plumes. Here we focus on the debris flow in the Via Lactea II simulation, and show that this incompletely phase-mixed material exhibits distinctive high velocity behavior. Unlike tidal streams, which may not necessarily intersect the Earth's location, debris flow is spatially uniform at 8 kpc and thus guaranteed to be present in the dark matter flux incident on direct detection experiments. At Earth-frame speeds greater than 450 km/s, debris flow comprises more than half of the dark matter at the Sun's location, and up to 80% at even higher speeds. Therefore, debris flow is most important for experiments that are particularly sensitive to the high speed tail of the dark matter distribution, such as searches for light or inelastic dark matter or experiments with directional sensitivity. We show that debris flow yields a distinctive recoil energy spectrum and a broadening of the distribution of incidence direction.

Michael Kuhlen; Mariangela Lisanti; David N. Spergel

2012-01-31

241

Directly detecting exozodiacal dust and disk variability  

NASA Astrophysics Data System (ADS)

Dust is common throughout stellar systems. The architecture of stellar systems may be typically comprised of a distant cold debris disk, a warm exozodiacal disk, and a hot inner disk. Dust in this exozodiacal region confounds exoplanet detections by scattering light or mimicking planetary emission. This environment must be well-modelled in order to find Earth-sized exoplanets. Interferometry at the Center for High Resolution Astronomy (CHARA) Array provides the angular resolution to directly detect near-infrared (NIR) excesses originating from warm and hot dust close to the host star. The recently upgraded Fiber-Linked Unit for Optical Recombination (JouFLU) is capable of measuring interferometric visibility contrasts to a precision of <0.1% and dust disk fluxes equal to 1% of the host star. There is likely a connection between these hot interferometrically detected dust disks and the harder-to-detect warm zodiacal dust analogues. In this way interferometric studies can observe the tip-of-the-iceberg of stellar system dust, providing details such as composition and grain size of dust, as well as statistics on the correlation of dust populations and stellar properties. These inner dust regions may exhibit a high degree of variability which should also be characterized and may give hint to the dust origin and replenishment mechanisms. JouFLU is currently involved in a large survey of exozodiacal dust stars of spectral types A through K with the aim to provide statistics about dust disk occurrence in relation to their host stars and the presence of cold dust reservoirs. Complementing this survey is a project of re-observing the earliest excess detections in order to determine their variability. In addition, NASA's InfraRed Telescope Facility (IRTF) provides a method for spectrophotometric detections of excess stellar flux corresponding to the presence of hot/warm exozodiacal dust. Multiple NIR interferometric instruments as well as medium resolution spectroscopy are a sensitive and affordable method of discovering inner disks and characterizing nearby habitable zone environments.

Scott, Nicholas J.

2015-01-01

242

Colorimetric Sensor Arrays for Volatile Organic Michael C. Janzen, Jennifer B. Ponder, Daniel P. Bailey, Crystal K. Ingison, and Kenneth S. Suslick*  

E-print Network

Colorimetric Sensor Arrays for Volatile Organic Compounds Michael C. Janzen, Jennifer B. Ponder-cost, sensitive colorimetric sensor array for the detection and identification of volatile organic compounds (VOCs of the ability of our colorimetric sensor arrays to distinguish among a large family of volatile organic

Suslick, Kenneth S.

243

MEMS and the direct detection of exoplanets  

NASA Astrophysics Data System (ADS)

Deformable mirrors, and particularly MEMS, are crucial components for the direct imaging of exoplanets for both ground-based and space-based instruments. Without deformable mirrors, coronagraphs are incapable of reaching contrasts required to image Jupiter-like planets. The system performance is limited by image quality degradation resulting from wavefront error introduced from multiple effects including: atmospheric turbulence, static aberrations in the system, non-common-path aberrations, all of which vary with time. Correcting for these effects requires a deformable mirror with fast response and numerous actuators having moderate stroke. Not only do MEMS devices fulfill this requirement but their compactness permits their application in numerous space- and ground-based instruments, which are often volume- and mass-limited. In this paper, I will briefly explain how coronagraphs work and their requirements. I then will discuss the Extreme Adaptive Optics needed to compensate for the introduced wavefront error and how MEMS devices are a good choice to achieve the performance needed to produce the contrasts necessary to detect exoplanets. As examples, I will discuss a facility instrument for the Gemini Observatory, called the Gemini Planet Imager, that will detect Jupiter-like planets and present recent results from the NASA Ames Coronagraph Experiment laboratory, in the context of a proposed space- based mission called EXCEDE. EXCEDE is planned to focus on protoplanetary disks.

Thomas, Sandrine J.; Macintosh, Bruce; Belikov, Ruslan

2014-03-01

244

EXTRAGALACTIC DARK MATTER AND DIRECT DETECTION EXPERIMENTS  

SciTech Connect

Recent astronomical data strongly suggest that a significant part of the dark matter content of the Local Group and Virgo Supercluster is not incorporated into the galaxy halos and forms diffuse components of these galaxy clusters. A portion of the particles from these components may penetrate the Milky Way and make an extragalactic contribution to the total dark matter containment of our Galaxy. We find that the particles of the diffuse component of the Local Group are apt to contribute {approx}12% to the total dark matter density near Earth. The particles of the extragalactic dark matter stand out because of their high speed ({approx}600 km s{sup -1}), i.e., they are much faster than the galactic dark matter. In addition, their speed distribution is very narrow ({approx}20 km s{sup -1}). The particles have an isotropic velocity distribution (perhaps, in contrast to the galactic dark matter). The extragalactic dark matter should provide a significant contribution to the direct detection signal. If the detector is sensitive only to the fast particles (v > 450 km s{sup -1}), then the signal may even dominate. The density of other possible types of the extragalactic dark matter (for instance, of the diffuse component of the Virgo Supercluster) should be relatively small and comparable with the average dark matter density of the universe. However, these particles can generate anomaly high-energy collisions in direct dark matter detectors.

Baushev, A. N., E-mail: baushev@gmail.com [DESY, D-15738 Zeuthen (Germany); Institut fuer Physik und Astronomie, Universitaet Potsdam, D-14476 Potsdam-Golm (Germany)

2013-07-10

245

An azodye-rhodamine-based fluorescent and colorimetric probe specific for the detection of Pd(2+) in aqueous ethanolic solution: synthesis, XRD characterization, computational studies and imaging in live cells.  

PubMed

Azodye-rhodamine hybrid colorimetric fluorescent probe () has been designed and synthesized. The structure of has been established based on single crystal XRD. It has been shown to act as a selective turn-on fluorescent chemosensor for Pd(2+) with >40 fold enhancement by exhibiting red emission among the other 27 cations studied in aqueous ethanol. The coordination features of the species of recognition have been computationally evaluated by DFT methods and found to have a distorted tetrahedral Pd(2+) center in the binding core. The probe () has been shown to detect Pd up to 0.45 ?M at pH 7.4. Furthermore, the probe can be used to image Pd(2+) in living cells. PMID:25537648

Mahapatra, Ajit Kumar; Manna, Saikat Kumar; Maiti, Kalipada; Mondal, Sanchita; Maji, Rajkishor; Mandal, Debasish; Mandal, Sukhendu; Uddin, Md Raihan; Goswami, Shyamaprosad; Quah, Ching Kheng; Fun, Hoong-Kun

2015-02-01

246

Halo Microlensing: Direct Detection of a Microlens  

NASA Astrophysics Data System (ADS)

The MACHO project has recently released 5.7 years of LMC microlensing data, presenting 17 candidate microlensing events. These events suggest an 8-50 MACHO halo and a most likely MACHO mass of 0.2-0.9 M_odot. However, nearly a decade after the first reported event {Alcock et al. 1993} there still remains much debate about the nature and location of the lensing matter. MACHO has also obtained WFPC2 follow-up data of the microlensing source stars, to date we have observed 16 candidates with HST. The WFPC2 follow-up data of MACHO event LMC-5 provided unexpected insight into the nature of the lens. This image revealed a very red, faint object displaced by 0.134^ from the source star which may well be the first direct detection of the dark matter component {lens} of a microlensing event. A second epoch of WFPC2 photometry will verify the proper motion of the lens and allow for a parallax measurement of its distance.

Cook, Kem

2002-07-01

247

CCMR: VOC Capture on Fibrous Substrates: Colorimetric Sensors  

NSDL National Science Digital Library

Volatile Organic Compounds (VOCs) such as chloroform, toluene and trichloroethylene can cause health hazards and affect indoor air quality. Therefore, cost effective and reusable sensors for the detection of these volatile gases are required. In this study, the potential use of diacetylene monomers as colorimetric sensors combined with electrospinning is investigated in order to develop sensor membranes from biodegradable Polylactic Acid (PLA).

Molina, Anna M.

2007-08-29

248

Colorimetric barbiturate sensing with hybrid spin crossover assemblies.  

PubMed

Spin crossover complexes based on either iron(II) or iron(III) give a colorimetric response upon self-assembly with barbituric acids. They can be used as visible sensors for these narcotics, selectively detecting barbiturates in the presence of other biologically-relevant hydrogen bonding species. PMID:24715100

Young, Michael C; Liew, Erica; Hooley, Richard J

2014-05-21

249

Colorimetric disposable paper coated with ZnO@ZnS core-shell nanoparticles for detection of copper ions in aqueous solutions.  

PubMed

In this study, we have proposed a new nanoparticle-containing test paper sensor that could be used as an inexpensive, easy-to-use, portable, and highly selective sensor to detect Cu(2+) ions in aqueous solutions. This disposable paper sensor is based on ZnO@ZnS core-shell nanoparticles. The core-shell nanoparticles were synthesized using a chemical method and then they were used for coating the paper. The synthesis of the ZnO@ZnS core-shell nanoparticles was performed at a temperature as low as 60 °C, and so far this is the lowest temperature for the synthesis of such core-shell nanoparticles. The sensitivity of the paper sensor was investigated for different Cu(2+) ion concentrations in aqueous solutions and the results show a direct linear relation between the Cu(2+) ions concentration and the color intensity of the paper sensor with a visual detection limit as low as 15 ?M (?0.96 ppm). Testing the present paper sensor on real river turbulent water shows a maximum 5% relative error for determining the Cu(2+) ions concentration, which confirms that the presented paper sensor can successfully be used efficiently for detection in complex solutions with high selectivity. Photographs of the paper sensor taken using a regular digital camera were transferred to a computer and analyzed by ImageJ Photoshop software. This finding demonstrates the potential of the present disposable paper sensor for the development of a portable, accurate, and selective heavy metal detection technology. PMID:25275616

Sadollahkhani, Azar; Hatamie, Amir; Nur, Omer; Willander, Magnus; Zargar, Behrooz; Kazeminezhad, Iraj

2014-10-22

250

Colorimetric Correction for Stereoscopic Camera Arrays  

E-print Network

Colorimetric Correction for Stereoscopic Camera Arrays Clyde Mouffranc and Vincent Nozick Gaspard Monge Institute, UMR 8049 Paris-Est Marne-la-Vallee University, France Abstract. Colorimetric correction that minimizes the colorimetric properties of the images. This lookup table is represented by a polynomial basis

Paris-Sud XI, Université de

251

A colorimetric sensor for determination of cysteine by carboxymethyl cellulose-functionalized gold nanoparticles.  

PubMed

A simple and sensitive colorimetric method for cysteine detection was established based on the carboxymethyl cellulose-functionalized gold nanoparticles (CMC-AuNPs). The nanoparticles were directly synthesized with sodium carboxymethyl cellulose by a simple approach, which would protect particles against salt-induced aggregation. Then the CMC-AuNPs solution exhibited a high colorimetric selectivity to cysteine. The assay results indicated that the introduction of cysteine could induce the aggregation of the colloidal solutions at the presence of sodium chloride, displaying changes in color and in UV-vis absorption spectra. Thus an exceptionally simple, rapid method for detecting cysteine was obtained at the linear range of 10.0-100.0 microM with the relative coefficient of 0.997. The proposed method possessed the advantages of simplicity and sensitivity, and was applied to real urine sample detection. The results were satisfying and the proposed method was especially appropriate for detection of cysteine in biological samples. PMID:20541646

Wei, Xiaoyi; Qi, Li; Tan, Junjun; Liu, Ruigang; Wang, Fuyi

2010-06-25

252

Reversible colorimetric probes for mercury sensing.  

PubMed

The selectivity and sensitivity of two colorimetric sensors based on the ruthenium complexes N719 [bis(2,2'-bipyridyl-4,4'-dicarboxylate)ruthenium(II) bis(tetrabutylammonium) bis(thiocyanate)] and N749 [(2,2':6',2' '-terpyridine-4,4',4' '-tricarboxylate)ruthenium(II) tris(tetrabutylammonium) tris(isothiocyanate)] are described. It was found that mercury ions coordinate reversibly to the sulfur atom of the dyes' NCS groups. This interaction induces a color change in the dyes at submicromolar concentrations of mercury. Furthermore, the color change of these dyes is selective for mercury(II) when compared with other ions such as lead(II), cadmium(II), zinc(II), or iron(II). The detection limit for mercury(II) ions--using UV-vis spectroscopy--in homogeneous aqueous solutions is estimated to be approximately 20 ppb for N719 and approximately 150 ppb for N749. Moreover, the sensor molecules can be adsorbed onto high-surface-area mesoporous metal oxide films, allowing reversible heterogeneous sensing of mercury ions in aqueous solution. The results shown herein have important implications in the development of new reversible colorimetric sensors for the fast, easy, and selective detection and monitoring of mercuric ions in aqueous solutions. PMID:16131215

Coronado, Eugenio; Galán-Mascarós, José R; Martí-Gastaldo, Carlos; Palomares, Emilio; Durrant, James R; Vilar, Ramón; Gratzel, M; Nazeeruddin, Md K

2005-09-01

253

A smartphone-based colorimetric reader for bioanalytical applications using the screen-based bottom illumination provided by gadgets.  

PubMed

A smartphone-based colorimetric reader (SBCR) was developed using a Samsung Galaxy SIII mini, a gadget (iPAD mini, iPAD4 or iPhone 5s), integrated with a custom-made dark hood and base holder assembly. The smartphone equipped with a back camera (5 megapixels resolution) was used for colorimetric imaging via the hood and base-holder assembly. A 96- or 24-well microtiter plate (MTP) was positioned on the gadget's screensaver that provides white light-based bottom illumination only in the specific regions corresponding to the bottom of MTP's wells. The pixel intensity of the captured images was determined by an image processing algorithm. The developed SBCR was evaluated and compared with a commercial MTP reader (MTPR) for three model assays: our recently developed human C-reactive protein sandwich enzyme-linked immunosorbent assay (ELISA), horseradish peroxidase direct ELISA, and bicinchoninic acid protein estimation assay. SBCR had the same precision, dynamic range, detection limit and sensitivity as MTPR for all three assays. With advanced microfabrication and data processing, SBCR will become more compact, lighter, inexpensive and enriched with more features. Therefore, SBCR with a remarkable computing power could be an ideal point-of-care (POC) colorimetric detection device for the next-generation of cost-effective POC diagnostics, immunoassays and diversified bioanalytical applications. PMID:25168283

Vashist, Sandeep Kumar; van Oordt, Thomas; Schneider, E Marion; Zengerle, Roland; von Stetten, Felix; Luong, John H T

2015-05-15

254

Indirect detection of radiation sources through direct detection of radiolysis products  

DOEpatents

A system for indirectly detecting a radiation source by directly detecting radiolytic products. The radiation source emits radiation and the radiation produces the radiolytic products. A fluid is positioned to receive the radiation from the radiation source. When the fluid is irradiated, radiolytic products are produced. By directly detecting the radiolytic products, the radiation source is detected.

Farmer, Joseph C. (Tracy, CA); Fischer, Larry E. (Los Gatos, CA); Felter, Thomas E. (Livermore, CA)

2010-04-20

255

Enzymatic assay for Cu(II) with horseradish peroxidase and its application in colorimetric logic gate.  

PubMed

We report an ultrasensitive and colorimetric assay for Cu(II) via enzymatic amplification strategy. The enzymatic activity of horseradish peroxidase (HRP) is strongly inhibited by Cu(I), which can be used indirectly to assay Cu(II). The limit of detection (LOD) is 0.37 nM, and the detection of 20 nM Cu(II) in solution can be achieved with naked eyes. This assay can be used to construct a colorimetric logic gate. PMID:23879883

Xianyu, Yunlei; Zhu, Kui; Chen, Wenwen; Wang, Xuefei; Zhao, Hongmei; Sun, Jiashu; Wang, Zhuo; Jiang, Xingyu

2013-08-01

256

A direct detection of Escherichia coli genomic DNA using gold nanoprobes  

PubMed Central

Background In situation like diagnosis of clinical and forensic samples there exists a need for highly sensitive, rapid and specific DNA detection methods. Though conventional DNA amplification using PCR can provide fast results, it is not widely practised in diagnostic laboratories partially because it requires skilled personnel and expensive equipment. To overcome these limitations nanoparticles have been explored as signalling probes for ultrasensitive DNA detection that can be used in field applications. Among the nanomaterials, gold nanoparticles (AuNPs) have been extensively used mainly because of its optical property and ability to get functionalized with a variety of biomolecules. Results We report a protocol for the use of gold nanoparticles functionalized with single stranded oligonucleotide (AuNP- oligo probe) as visual detection probes for rapid and specific detection of Escherichia coli. The AuNP- oligo probe on hybridization with target DNA containing complementary sequences remains red whereas test samples without complementary DNA sequences to the probe turns purple due to acid induced aggregation of AuNP- oligo probes. The color change of the solution is observed visually by naked eye demonstrating direct and rapid detection of the pathogenic Escherichia coli from its genomic DNA without the need for PCR amplification. The limit of detection was ~54 ng for unamplified genomic DNA. The method requires less than 30 minutes to complete after genomic DNA extraction. However, by using unamplified enzymatic digested genomic DNA, the detection limit of 11.4 ng was attained. Results of UV-Vis spectroscopic measurement and AFM imaging further support the hypothesis of aggregation based visual discrimination. To elucidate its utility in medical diagnostic, the assay was validated on clinical strains of pathogenic Escherichia coli obtained from local hospitals and spiked urine samples. It was found to be 100% sensitive and proves to be highly specific without any cross reaction with non-Escherichia coli strains. Conclusion This work gives entry into a new class of DNA/gold nanoparticles hybrid materials which might have optical property that can be controlled for application in diagnostics. We note that it should be possible to extend this strategy easily for developing new types of DNA biosensor for point of care detection. The salient feature of this approach includes low-cost, robust reagents and simple colorimetric detection of pathogen. PMID:22309695

2012-01-01

257

ccsd00003303, Dark Matter Direct Detection using Cryogenic  

E-print Network

ccsd­00003303, version 1 ­ 17 Nov 2004 Dark Matter Direct Detection using Cryogenic Detectors. Solving the Dark Matter enigma represents one of the key objectives of contemporary physics. Recent Matter gap, and direct detection Dark Matter experiments have recently reached sensitivities allowing

258

Brief Report: Eye Direction Detection Improves with Development in Autism  

ERIC Educational Resources Information Center

Eye direction detection has been claimed to be intact in autism, but the development of this skill has not been investigated. Eleven children with autism and 11 typically developing children performed a demanding face-to-face eye direction detection task. Younger children with autism demonstrated a deficit in this skill, relative to younger…

Webster, Simon; Potter, Douglas D.

2008-01-01

259

Dark matter direct detection constraints from gauge bosons loops  

NASA Astrophysics Data System (ADS)

While many interactions of dark matter (DM) with the standard model (SM) affect direct detection and LHC searches, there are only a few operators generating annihilation of DM into photons. All of these operators, except four of them, give rise to unsuppressed rates, rendering indirect detection superior to other search strategies. For two of the four effective interactions with velocity-suppressed annihilation cross sections, we identify a new type of loop effect which significantly enhances the associated direct detection rates. As a result, relevant constraints from next-generation direct detection experiments on DM-SM interactions, so far only bounded by the LHC, are obtained.

Crivellin, Andreas; Haisch, Ulrich

2014-12-01

260

Photonic crystal structures with tunable structure color as colorimetric sensors.  

PubMed

Colorimetric sensing, which transduces environmental changes into visible color changes, provides a simple yet powerful detection mechanism that is well-suited to the development of low-cost and low-power sensors. A new approach in colorimetric sensing exploits the structural color of photonic crystals (PCs) to create environmentally-influenced color-changeable materials. PCs are composed of periodic dielectrics or metallo-dielectric nanostructures that affect the propagation of electromagnetic waves (EM) by defining the allowed and forbidden photonic bands. Simultaneously, an amazing variety of naturally occurring biological systems exhibit iridescent color due to the presence of PC structures throughout multi-dimensional space. In particular, some kinds of the structural colors in living organisms can be reversibly changed in reaction to external stimuli. Based on the lessons learned from natural photonic structures, some specific examples of PCs-based colorimetric sensors are presented in detail to demonstrate their unprecedented potential in practical applications, such as the detections of temperature, pH, ionic species, solvents, vapor, humidity, pressure and biomolecules. The combination of the nanofabrication technique, useful design methodologies inspired by biological systems and colorimetric sensing will lead to substantial developments in low-cost, miniaturized and widely deployable optical sensors. PMID:23539027

Wang, Hui; Zhang, Ke-Qin

2013-01-01

261

Photonic Crystal Structures with Tunable Structure Color as Colorimetric Sensors  

PubMed Central

Colorimetric sensing, which transduces environmental changes into visible color changes, provides a simple yet powerful detection mechanism that is well-suited to the development of low-cost and low-power sensors. A new approach in colorimetric sensing exploits the structural color of photonic crystals (PCs) to create environmentally-influenced color-changeable materials. PCs are composed of periodic dielectrics or metallo-dielectric nanostructures that affect the propagation of electromagnetic waves (EM) by defining the allowed and forbidden photonic bands. Simultaneously, an amazing variety of naturally occurring biological systems exhibit iridescent color due to the presence of PC structures throughout multi-dimensional space. In particular, some kinds of the structural colors in living organisms can be reversibly changed in reaction to external stimuli. Based on the lessons learned from natural photonic structures, some specific examples of PCs-based colorimetric sensors are presented in detail to demonstrate their unprecedented potential in practical applications, such as the detections of temperature, pH, ionic species, solvents, vapor, humidity, pressure and biomolecules. The combination of the nanofabrication technique, useful design methodologies inspired by biological systems and colorimetric sensing will lead to substantial developments in low-cost, miniaturized and widely deployable optical sensors. PMID:23539027

Wang, Hui; Zhang, Ke-Qin

2013-01-01

262

DIRECTIONAL DETECTION OF A NEUTRON SOURCE.  

SciTech Connect

Advantages afforded by the development of new directional neutron detectors and imagers are discussed. Thermal neutrons have mean free paths in air of about 20 meters, and can be effectively imaged using coded apertures. Fission spectrum neutrons have ranges greater than 100 meters, and carry enough energy to scatter at least twice in multilayer detectors which can yield both directional and spectral information. Such strategies allow better discrimination between a localized spontaneous fission source and the low, but fluctuating, level of background neutrons generated by cosmic rays. A coded aperture thermal neutron imager will be discussed as well as a proton-recoil double-scatter fast-neutron directional detector with time-of-flight energy discrimination.

VANIER, P.E.; FORMAN, L.

2006-10-23

263

Paper-based colorimetric immunosensor for visual detection of carcinoembryonic antigen based on the high peroxidase-like catalytic performance of ZnFe2O4-multiwalled carbon nanotubes.  

PubMed

A new paper-based colorimetric immunosensor for the detection of carcinoembryonic antigen (CEA) was developed based on the intrinsic peroxidase activity of ZnFe2O4-multiwalled carbon nanotubes (ZnFe2O4@MWNTs). The immunosensor platform was prepared by depositing chitosan and porous gold onto filter paper and entrapping the primary antibodies (Ab1) onto the layers. Secondary antibodies (Ab2) were assembled on the surface of the functionalized ZnFe2O4@MWNTs. The immunosensor response was quantified as a color change resulting from ZnFe2O4@MWNTs catalyzing the oxidation of 3,3',5,5'-tetramethylbenzidine in the presence of H2O2. The catalytic performance of ZnFe2O4@MWNTs was higher than ZnFe2O4 due to the high electrical conductance of MWNTs, moreover, the electron communications between ZnFe2O4@MWNTs and substrates are electrically "wired". Detection was achieved by measuring the color change when the concentrations of CEA were different. The color change can be quantified with the naked eye but a digitalized picture can also be used to provide more sensitive comparison to a calibrated color scheme. This method was simple for CEA detection with a linear range from 0.005 to 30 ng mL(-1) and a detection limit of 2.6 pg mL(-1). Such an equipment-free immunoassay has great potential in resource-limited environments. PMID:24205509

Liu, Weiyan; Yang, Hongmei; Ding, Yanan; Ge, Shenguang; Yu, Jinghua; Yan, Mei; Song, Xianrang

2014-01-01

264

Simultaneous direct detection of Shiga-toxin producing Escherichia coli (STEC) strains by optical biosensing with oligonucleotide-functionalized gold nanoparticles.  

PubMed

A simultaneous direct detection of Shiga-toxin producing strains of E. coli (STEC; "Big Six" - O26, O45, O103, O111, O121, and O145) as well as O157 strains by optical biosensing with oligonucleotide-functionalized gold nanoparticles (AuNPs) was developed. Initially, conserved regions of stx genes were amplified by asymmetric polymerase chain reaction (asPCR). Pairs of single stranded thiol-modified oligonucleotides (30-mer) were immobilized onto AuNPs and used as probes to capture regions of stx1 (119-bp) and/or stx2 (104-bp) genes from STEC strains. DNA samples from pure cultures and food samples were sandwich hybridized with AuNP-oligo probes at optimal conditions (50 °C, 30 min). A complex was formed from the hybridization of AuNP-probes and target DNA fragments that retained the initial red color of the reaction solutions. For non-target DNA, a color change from red to purplish-blue was observed following an increase in salt concentration, thus providing the basis of simultaneous direct colorimetric detection of target DNA in the samples. Enrichment and pooling systems were incorporated to efficiently process a large number of food samples (ground beef and blueberries) and detection of live targets. The detection limit was <1 log CFU g(-1), requiring less than 1 h to complete after DNA sample preparation with 100% specificity. Gel electrophoresis verified AuNP-DNA hybridization while spectrophotometric data and transmission electron microscope (TEM) images supported color discrimination based on the occurrence of molecular aggregation. In conclusion, the significant features of this approach took advantage of the unique colorimetric properties of AuNPs as a low-cost and simple approach yet with high specificity for simultaneous detection of STEC strains. PMID:25563863

Quintela, Irwin A; de Los Reyes, Benildo G; Lin, Chih-Sheng; Wu, Vivian C H

2015-01-28

265

Molecular diagnosis of ?-thalassemias by the colorimetric nanogold.  

PubMed

A new application of gold nanoparticles (AuNPs) as a colorimetric method for gene detection of ?-thalassemia 1 (SEA deletion) is reported here for the first time. This technique is based on color changes from salt-induced aggregation of un-hybridized nanogold probes after hybridization with the target DNA. Specific DNA probes were synthesized, thiol modified and conjugated on the surface of AuNPs. The target DNA was amplified and hybridized with the AuNPs-immobilized probe. Salt solution (NaCl) was added to induce aggregation of the un-hybridized nanogold probes. The color changes were visualized either by the naked eye or by UV-vis spectrophotometry at 520 nm. By this nanogold colorimetric method samples carrying normal ?-globin genes could be successfully identified from samples carrying ?-globin genes causing ?-thalassemia 1 (SEA deletion), either as a carrier or disease form. Results demonstrated that the new colorimetric nanogold method is a definite gene diagnosis of ?-thalassemia. It is accurate, simple, rapid, specific, sensitive, and cost effective. It is also a promising point-of-care testing (POCT) method for thalassemias and other genetic disorders. The new colorimetric nanogold is a method of choice for areas where access to sophisticated molecular diagnosis is limited. PMID:24383063

Chomean, Sirinart; Wangmaung, Nantawan; Sritongkham, Pornpimol; Promptmas, Chamras; Mas-Oodi, Sumana; Tanyong, Dalina; Ittarat, Wanida

2014-02-21

266

A novel highly selective colorimetric sensor for aluminum (III) ion using Schiff base derivative  

NASA Astrophysics Data System (ADS)

A novel colorimetric sensor, 2-hydroxy naphthaldehyde isonicotinoyl hydrazone (HINH), was easily synthesized by the condensation of isoniazid and 2-hydroxy-1-naphthaldehyde. The as-prepared compound showed effective colorimetric single selectivity and high sensitivity for aluminum cation in CH3CN/H2O (1:3) binary solutions. The detection limit is 1.0 × 10-8 M Al3+ based on UV-vis changes.

Wang, Dong-Fang; Ke, Ying-Chang; Guo, Hong-Xu; Chen, Jianhua; Weng, Wen

2014-03-01

267

Colorimetric characterization of LED luminaires  

NASA Astrophysics Data System (ADS)

The Optical Metrology Division of Inmetro – National Institute of Metrology, Quality and Technology has recently started the colorimetric characterization of lamps by implementing Correlated Color Temperature (CCT) and Color Rendering Index (CRI) measurements of incandescent lamps, followed by the CFL, and LED lamps and luminaires. Here we present the results for the verification of the color characterization of samples of SSL luminaires for public as well as indoor illumination that are sold in Brazil.

Costa, C. L. M.; Vieira, R. R.; Pereira, R. C.; Silva, P. V. M.; Oliveira, I. A. A.; Sardinha, A. S.; Viana, D. D.; Barbosa, A. H.; Souza, L. P.; Alvarenga, A. D.

2015-01-01

268

Colorimetric determination of indolic drugs.  

PubMed

A colorimetric method has been developed for the quantitative determination of the rescinnamine, reserpine upto (-10(-4M)), Yohimbine on complexation with bromothymol blue. The coloured complexes exhibit absorption maxima in the region 415-416 nm. The RSD (Relative Standard Deviation) of the method is 2.02%. The method is simple, easy, rapid and convenient for routine analysis of the indolic drugs. PMID:16431399

Azhar, Iqbal; Mazhar, Farah; Manzar, Qazi Nawab; Hussain, Iftekhar; Shamim, Sumbul

2005-04-01

269

Detecting Blackholes and Volcanoes in Directed Networks  

E-print Network

In this paper, we formulate a novel problem for finding blackhole and volcano patterns in a large directed graph. Specifically, a blackhole pattern is a group which is made of a set of nodes in a way such that there are only inlinks to this group from the rest nodes in the graph. In contrast, a volcano pattern is a group which only has outlinks to the rest nodes in the graph. Both patterns can be observed in real world. For instance, in a trading network, a blackhole pattern may represent a group of traders who are manipulating the market. In the paper, we first prove that the blackhole mining problem is a dual problem of finding volcanoes. Therefore, we focus on finding the blackhole patterns. Along this line, we design two pruning schemes to guide the blackhole finding process. In the first pruning scheme, we strategically prune the search space based on a set of pattern-size-independent pruning rules and develop an iBlackhole algorithm. The second pruning scheme follows a divide-and-conquer strategy to fur...

Li, Zhongmou; Liu, Yanchi

2010-01-01

270

Direct Detection of the Asteroidal YORP Effect  

NASA Astrophysics Data System (ADS)

The Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect is a torque that can modify the rotation rates and obliquities of small bodies in the solar system via the combined effects of incident solar radiation pressure and the recoil effect from anisotropic emission of thermal photons. The YORP effect is the only realistic mechanism for explaining the intriguing spin-axis alignments within the Koronis asteroid family, and quite possibly explains the anomalous distribution of spin rates for small asteroids. YORP is now thought to be an important mechanism in the formation of binary asteroid systems, and has a direct bearing on the related Yarkovsky effect, which affects the orbital motion of small asteroids. Despite its importance, there exists only indirect evidence for the presence of YORP on solar system objects, until now. We conducted an optical-imaging monitoring campaign from 2001-2005 on a small near-Earth asteroid, 2000 PH5, now known as asteroid (54509) YORP. We found that the asteroid has been continuously increasing its sidereal rotation rate by (2.0 ± 0.2)*10-4 deg./day2, over this 4-yr period (Lowry et al., 2007, Science 316, 272-274). The observed YORP strength is consistent with detailed shape-model-based theoretical calculations of the effect (Taylor et al., 2007, Science 316, 274-277). We simulated the asteroid's close Earth approaches from 2001 to 2005, showing that gravitational torques cannot explain the observed spin rate increase. Dynamical simulations suggest that 2000 PH5 may reach a rotation period of just 20 seconds toward the end of its expected lifetime.

Lowry, Stephen C.; Fitzsimmons, A.; Pravec, P.; Vokrouhlicky, D.; Boehnhardt, H.; Taylor, P. A.; Margot, J. L.; Galád, A.; Irwin, M.; Irwin, J.; Kusnirák, P.

2007-10-01

271

Status of the XENON Direct Dark Matter Detection Experiment  

Microsoft Academic Search

The XENON Collaboration is developing a dark matter detector using liquid xenon (LXe) as the target medium for detecting weakly interacting massive particles (WIMPs). The goal of the collaboration is to operate an array of LXe time projection chambers (TPCs) with 1000 times greater sensitivity to WIMPs than current direct dark matter detection experiments. Recent measurements by members of the

Richard Hasty

2006-01-01

272

Status of the XENON Direct Dark Matter Detection Experiment  

Microsoft Academic Search

The XENON collaboration is developing a dark matter detector using liquid xenon (LXe) as the target medium for detecting Weakly Interacting Massive Particles (WIMPs). The goal of the collaboration is to operate an array of LXe time projection chambers (TPCs) with 1000 times greater sensitivity to WIMPs than current direct dark matter detection experiments. Recent measurements by members of the

Richard Hasty

2006-01-01

273

Maximum patch method for directional dark matter detection  

Microsoft Academic Search

Present and planned dark matter detection experiments search for WIMP-induced nuclear recoils in poorly known background conditions. In this environment, the maximum gap statistical method provides a way of setting more sensitive cross section upper limits by incorporating known signal information. We give a recipe for the numerical calculation of upper limits for planned directional dark matter detection experiments, that

Shawn Henderson; Jocelyn Monroe; Peter Fisher

2008-01-01

274

A Study on Plagiarism Detection and Plagiarism Direction Identification Using  

E-print Network

A Study on Plagiarism Detection and Plagiarism Direction Identification Using Natural Language is dedicated to the memory of my grandfather, Yuk Ming Chong. iii #12;iv #12;"Iron is full of impurities plagiarism detection. This is a computational approach which assists humans in judging whether pieces

Mitkov, Ruslan

275

Directional Dark Matter Detection Beyond the Neutrino Bound Philipp Grothaus  

E-print Network

Directional Dark Matter Detection Beyond the Neutrino Bound Philipp Grothaus and Malcolm Fairbairn creates an irreducible background for direct dark matter experiments with sensitivities to WIMP the potential to study dark matter beyond the neutrino bound by fitting event distributions in multiple dimen

276

Portable paper-based device for quantitative colorimetric assays relying on light reflectance principle.  

PubMed

This paper presents a novel paper-based analytical device based on the colorimetric paper assays through its light reflectance. The device is portable, low cost (<20 dollars), and lightweight (only 176 g) that is available to assess the cost-effectiveness and appropriateness of the original health care or on-site detection information. Based on the light reflectance principle, the signal can be obtained directly, stably and user-friendly in our device. We demonstrated the utility and broad applicability of this technique with measurements of different biological and pollution target samples (BSA, glucose, Fe, and nitrite). Moreover, the real samples of Fe (II) and nitrite in the local tap water were successfully analyzed, and compared with the standard UV absorption method, the quantitative results showed good performance, reproducibility, and reliability. This device could provide quantitative information very conveniently and show great potential to broad fields of resource-limited analysis, medical diagnostics, and on-site environmental detection. PMID:24375226

Li, Bowei; Fu, Longwen; Zhang, Wei; Feng, Weiwei; Chen, Lingxin

2014-04-01

277

A selective colorimetric and ratiometric fluorescent probe for hydrogen sulfide.  

PubMed

A reaction-based colorimetric and ratiometric fluorescent probe based on an ICT-strategy for selective detection of H(2)S that exploited the H(2)S-mediated reduction of nitrocompound to amines was explored. And it displayed high selectivity for H(2)S over other relevant reactive sulfur, oxygen, nitrogen species and other anions with more than 120 nm blue shift and the change of emission intensity ratio inducted by H(2)S was over 4750. PMID:22965805

Wu, Ming-Yu; Li, Kun; Hou, Ji-Ting; Huang, Zheng; Yu, Xiao-Qi

2012-10-01

278

Comparing readout strategies to directly detect dark matter  

NASA Astrophysics Data System (ADS)

Over the past decades, several ideas and technologies have been developed to directly detect weakly interacting massive particles (WIMP) from the galactic halo. All these detection strategies share the common goal of discriminating a WIMP signal from the residual backgrounds. By directly detecting WIMPs, one can measure some or all of the observables associated to each nuclear recoil candidates, such as their energy and direction. In this study, we compare and examine the discovery potentials of each readout strategies from counting only (bubble chambers) to directional detectors (Time Projection Chambers) with 1d-, 2d-, and 3d-sensitivity. Using a profile likelihood analysis, we show that, in the case of a large and irreducible background contamination characterized by an energy distribution similar to the expected WIMP signal, directional information can improve the sensitivity of the experiment by several orders of magnitude. We also found that 1d directional detection is only less effective than a full 3d directional sensitivity by about a factor of 3, or 10 if we assume no sense recognition, still improving by a factor of 2 or more if only the energy of the events is being measured.

Billard, J.

2015-01-01

279

On the Direct Detection of Dark Matter Annihilation  

E-print Network

We investigate the direct detection phenomenology of a class of dark matter (DM) models in which DM does not directly interact with nuclei, {but rather} the products of its annihilation do. When these annihilation products are very light compared to the DM mass, the scattering in direct detection experiments is controlled by relativistic kinematics. This results in a distinctive recoil spectrum, a non-standard and or even {\\it absent} annual modulation, and the ability to probe DM masses as low as a $\\sim$10 MeV. We use current LUX data to show that experimental sensitivity to thermal relic annihilation cross sections has already been reached in a class of models. Moreover, the compatibility of dark matter direct detection experiments can be compared directly in $E_{min}$ space without making assumptions about DM astrophysics. Lastly, when DM has direct couplings to nuclei, the limit from annihilation to relativistic particles in the Sun can be stronger than that of conventional non-relativistic direct detect...

Cherry, John F; Shoemaker, Ian M

2015-01-01

280

On the Direct Detection of Dark Matter Annihilation  

E-print Network

We investigate the direct detection phenomenology of a class of dark matter (DM) models in which DM does not directly interact with nuclei, {but rather} the products of its annihilation do. When these annihilation products are very light compared to the DM mass, the scattering in direct detection experiments is controlled by relativistic kinematics. This results in a distinctive recoil spectrum, a non-standard and or even {\\it absent} annual modulation, and the ability to probe DM masses as low as a $\\sim$10 MeV. We use current LUX data to show that experimental sensitivity to thermal relic annihilation cross sections has already been reached in a class of models. Moreover, the compatibility of dark matter direct detection experiments can be compared directly in $E_{min}$ space without making assumptions about DM astrophysics. Lastly, when DM has direct couplings to nuclei, the limit from annihilation to relativistic particles in the Sun can be stronger than that of conventional non-relativistic direct detection by more than three orders of magnitude for masses in a 2-8 GeV window.

John F. Cherry; Mads T. Frandsen; Ian M. Shoemaker

2015-01-13

281

Highly sensitive, colorimetric detection of mercury(II) in aqueous media by quaternary ammonium group-capped gold nanoparticles at room temperature.  

PubMed

We provide a highly sensitive and selective assay to detect Hg(2+) in aqueous solutions using gold nanoparticles modified with quaternary ammonium group-terminated thiols at room temperature. The mechanism is the abstraction of thiols by Hg(2+) that led to the aggregation of nanoparticles. With the assistance of solar light irradiation, the detection limit can be as low as 30 nM, which satisfies the guideline concentration of Hg(2+) in drinking water set by the WHO. In addition, the dynamic range of detection is wide (3 × 10(-8)-1 × 10(-2) M). This range, to our best knowledge, is the widest one that has been reported so far in gold nanoparticle (AuNP)-based assays for Hg(2+). PMID:21069969

Liu, Dingbin; Qu, Weisi; Chen, Wenwen; Zhang, Wei; Wang, Zhuo; Jiang, Xingyu

2010-12-01

282

Routine use of a protease zymogen-based colorimetric assay for the detection of Beta-glucan and its role in clinical practice.  

PubMed

The detection of Aspergillus antigen (galactomannan) is considered a reliable marker for the diagnosis of invasive aspergillosis (IA), yet the sensibility and specificity of the assays commonly employed in routine are not optimal. The aim of the present study was to investigate whether the detection of another panfungal antigen, the (1,3)-b-D-glucan could have an auxiliary role in the identification of patients with IA. The study was carried out on 63 sera belonging to patients who had been screened for galactomannan, according to the clinical suspect of IA. Our data show that the positive galactomannan results were not confirmed by positive (1,3)-b-D-glucan results in patients receiving therapy with beta-lactam antibiotics associated with tazobactam, whereas in all the other cases, with the exception of four, the results of the (1,3)-b-D-glucan test were confirmatory of the galactomannan results. PMID:25572748

Farina, C; Lombardi, G; Andreoni, S; Manso, E; Perin, S; Panellis, D; Fazii, P; Conte, M; Sanna, S; Pini, P; Blasi, E

2014-01-01

283

A "light-on" colorimetric assay for anion detection using the inhibitory effect of anions on the catalytic activity of metal nanoparticles for the degradation of methyl orange.  

PubMed

In this communication, we studied the inhibitory effects of anions on the catalytic activity of metal nanoparticles for the degradation of methyl orange (MO). Some anions have great affinity with specific metal nanoparticles, thus resulting in the change of surface state and inhibition of catalytic activity, which can be observed with the naked eye or manifested in the UV spectrum of MO for anion detection. PMID:25317955

Lu, Lixia; Yang, Fan; Yang, Xiurong

2014-12-01

284

Gold nanoparticle-based simple colorimetric and ultrasensitive dynamic light scattering assay for the selective detection of Pb(II) from paints, plastics, and water samples.  

PubMed

Pb (II) is a common water pollutant with high toxicity. According to the CDC, about 310,000 U.S. children of ages 1-5 have high levels of lead in their blood that it is due to the exposure to lead from plastic toys and other products. As a result, the development of ultrasensitive assays for the real-time detection of Pb(II) from plastic toys and paints is very important for water controlling, clinical toxicology and industrial processes. Driven by the need to detect trace amounts of Pb(II) from water samples, we report a label-free, highly selective and ultra sensitive glutathione modified gold nanoparticle based dynamic light scattering (DLS) probe for Pb(II) recognition in 100 ppt level from aqueous solution with excellent discrimination against other heavy metals. The sensitivity of our assay to detect Pb(II) level in water is almost 2 orders of magnitude higher than the EPA standard limit. We have also demonstrated that our DLS assay is capable of measuring the amount of Pb(II) in paint, plastic toys, and water from MS river. A possible mechanism and operating principles of our DLS assay have been discussed. Ultimately, this nanotechnology driven assay could have enormous potential applications in rapid, on-site monitoring of Pb(II) from day-to-day sample. PMID:21306127

Beqa, Lule; Singh, Anant Kumar; Khan, Sadia Afrin; Senapati, Dulal; Arumugam, Sri Ranjini; Ray, Paresh Chandra

2011-03-01

285

Colorimetric Solid-Phase Extractor  

NASA Technical Reports Server (NTRS)

The heart of a colorimetric solid phase extractor (CSPE) test kit quickly measures the concentration of the biocides silver or iodine in astronauts' drinking water to determine whether concentrations are safe. When 10 milliliters (ml) of water is drawn through the disk, the disk will turn color (yellow in this picture for iodine) indicating the presence of the biocides. The device could someday be used to test water safety at reservoirs and water treatment plants on Earth. (photo credit: Microanalytical Instrumentation Center, Iowa State University).

2003-01-01

286

Can the Existence of Dark Energy Be Directly Detected?  

E-print Network

The majority of astronomers and physicists accept the reality of dark energy and also believe that it can only be studied indirectly through observation of the motions of stars and galaxies. In this paper I open the experimental question of whether it is possible to directly detect dark energy through the presence of dark energy density. Two thirds of this paper outlines the major aspects of dark energy density as now comprehended by the astronomical and physics community. The final third summarizes various proposals for direct detection of dark energy density or its possible effects. At this time I do not have a fruitful answer to the question: Can the Existence of Dark Energy Be Directly Detected?

Martin L. Perl

2008-10-06

287

Halo Independent Direct Detection of Momentum-Dependent Dark Matter  

E-print Network

We show that the momentum dependence of dark matter interactions with nuclei can be probed in direct detection experiments without knowledge of the dark matter velocity distribution. This is one of the few properties of DM microphysics that can be determined with direct detection alone, given a signal of dark matter in multiple direct detection experiments with different targets. Long-range interactions arising from the exchange of a light mediator are one example of momentum-dependent DM. For data produced from the exchange of a massless mediator we find for example that the mediator mass can be constrained to be $\\lesssim 10$ MeV for DM in the 20-1000 GeV range in a halo-independent manner.

John F. Cherry; Mads T. Frandsen; Ian M. Shoemaker

2014-10-13

288

65 nm CMOS Sensors Applied to Mathematically Exact Colorimetric Reconstruction  

E-print Network

Extracting colorimetric image information from the spectral characteristics of image sensors is a key issue in accurate image acquisition. Technically feasible filter/sensor combinations usually do not replicate colorimetric responses with sufficient accuracy to be directly applicable to color representation. A variety of transformations have been proposed in the literature to compensate for this. However, most of those rely on heuristics and/or introduce a reconstruction dependent on the composition of the incoming illumination. In this work, we present a spectral reconstruction method that is independent of illumination and is derived in a mathematically strict way. It provides a deterministic method to arrive at a least mean squared error approximation of a target spectral characteristic from arbitrary sensor response curves. Further, we present a new CMOS sensor design in a standard digital 65nm CMOS technology. Novel circuit techniques are used to achieve performance comparable with much larger-sized spe...

Mayr, C; Krause, A; Schlüßler, J -U; Schüffny, R

2014-01-01

289

Highly selective colorimetric detection and preconcentration of Bi(III) ions by dithizone complexes anchored onto mesoporous TiO2  

NASA Astrophysics Data System (ADS)

We successfully developed a single-step detection and removal unit for Bi(III) ions based on dithizone (DZ) anchored on mesoporous TiO2 with rapid colorometric response and high selectivity for the first time. [(DZ)3-Bi] complex is easily separated and collected by mesoporous TiO2 as adsorbent and preconcentrator without any color change of the produced complex onto the surface of mesoporous TiO2 (TiO2-[(DZ)3-Bi]) at different Bi(III) concentrations. This is because highly potent mesoporous TiO2 architecture provides proficient channeling or movement of Bi(III) ions for efficient binding of metal ion, and the simultaneous excellent adsorbing nature of mesoporous TiO2 provides an extra plane for the removal of metal ions.

Faisal, Mohd; Ismail, Adel A.; Harraz, Farid A.; Bouzid, Houcine; Al-Sayari, Saleh A.; Al-Hajry, Ali

2014-02-01

290

Highly selective colorimetric detection and preconcentration of Bi(III) ions by dithizone complexes anchored onto mesoporous TiO2  

PubMed Central

We successfully developed a single-step detection and removal unit for Bi(III) ions based on dithizone (DZ) anchored on mesoporous TiO2 with rapid colorometric response and high selectivity for the first time. [(DZ)3-Bi] complex is easily separated and collected by mesoporous TiO2 as adsorbent and preconcentrator without any color change of the produced complex onto the surface of mesoporous TiO2 (TiO2-[(DZ)3-Bi]) at different Bi(III) concentrations. This is because highly potent mesoporous TiO2 architecture provides proficient channeling or movement of Bi(III) ions for efficient binding of metal ion, and the simultaneous excellent adsorbing nature of mesoporous TiO2 provides an extra plane for the removal of metal ions. PMID:24502680

2014-01-01

291

Highly selective colorimetric detection and preconcentration of Bi(III) ions by dithizone complexes anchored onto mesoporous TiO2.  

PubMed

We successfully developed a single-step detection and removal unit for Bi(III) ions based on dithizone (DZ) anchored on mesoporous TiO2 with rapid colorometric response and high selectivity for the first time. [(DZ)3-Bi] complex is easily separated and collected by mesoporous TiO2 as adsorbent and preconcentrator without any color change of the produced complex onto the surface of mesoporous TiO2 (TiO2-[(DZ)3-Bi]) at different Bi(III) concentrations. This is because highly potent mesoporous TiO2 architecture provides proficient channeling or movement of Bi(III) ions for efficient binding of metal ion, and the simultaneous excellent adsorbing nature of mesoporous TiO2 provides an extra plane for the removal of metal ions. PMID:24502680

Faisal, Mohd; Ismail, Adel A; Harraz, Farid A; Bouzid, Houcine; Al-Sayari, Saleh A; Al-Hajry, Ali

2014-01-01

292

Direct IR Interferometric Detection of Extra Solar Planets  

NASA Technical Reports Server (NTRS)

This paper describes a concept for the direct detection of extra solar planets. The concept is based on a decade old idea from Bracewell but expanded. A long baseline interferometer is examined with two three meter telescopes, cooled to 70K and a baseline of 30-50 meters. In space, this instrument would be able to detect an Earth sized planet around a solar like star at 10 parsec in approximately 1 hour of integration (5 sigma). The total number of candidate stars with detectable "Earths" number in the thousands.

Shao, Michael

1989-01-01

293

Incorporation of the fluoride induced Si-O bond cleavage and functionalized gold nanoparticle aggregation into one colorimetric probe for highly specific and sensitive detection of fluoride.  

PubMed

A highly selective and sensitive probe was developed for the field test of F(-) in environmental waters. The probe was fabricated by anchoring 4-mercaptopyridine (MPD) on AuNPs via Au-S interaction to form MPD-AuNPs, and further assembling 3-aminopropyltrimethoxysilane (APTMS) on the surface of MPD-AuNPs. The hydrolysis and cross-link of APTMS resulted in a thin monolayer of Si-O-Si protecting layer to encapsulated MPD-AuNPs. In the assay, F(-) reacted with Si-O bond and thus destroyed the outer protecting layer of the probe, and further triggered the aggregation of internal MPD-AuNPs by forming N-H-F hydrogen bond. The F(-) induced aggregation of functionalized AuNPs gave rise to significant solution color switch from red to blue, which facilitated visual assay of F(-) in the range of 1.0-7.0 ?g mL(-1) by naked eyes. The probe is able to discriminate F(-) from a wide range of environmentally dominant ions, thus it can be applied to detect F(-) in drinkable water with satisfactory results that is agreed well with that of using ion chromatography. PMID:24745747

Sun, Jie-Fang; Liu, Rui; Zhang, Zhong-Mian; Liu, Jing-Fu

2014-04-11

294

Comparison of direct and heterodyne detection optical intersatellite communication links  

NASA Technical Reports Server (NTRS)

The performance of direct and heterodyne detection optical intersatellite communication links are evaluated and compared. It is shown that the performance of optical links is very sensitive to the pointing and tracking errors at the transmitter and receiver. In the presence of random pointing and tracking errors, optimal antenna gains exist that will minimize the required transmitter power. In addition to limiting the antenna gains, random pointing and tracking errors also impose a power penalty in the link budget. This power penalty is between 1.6 to 3 dB for a direct detection QPPM link, and 3 to 5 dB for a heterodyne QFSK system. For the heterodyne systems, the carrier phase noise presents another major factor of performance degradation that must be considered. In contrast, the loss due to synchronization error is small. The link budgets for direct and heterodyne detection systems are evaluated. It is shown that, for systems with large pointing and tracking errors, the link budget is dominated by the spatial tracking error, and the direct detection system shows a superior performance because it is less sensitive to the spatial tracking error. On the other hand, for systems with small pointing and tracking jitters, the antenna gains are in general limited by the launch cost, and suboptimal antenna gains are often used in practice. In which case, the heterodyne system has a slightly higher power margin because of higher receiver sensitivity.

Chen, C. C.; Gardner, C. S.

1987-01-01

295

Analysis of the theoretical bias in dark matter direct detection  

E-print Network

Fitting the model "A" to dark matter direct detection data, when the model that underlies the data is "B", introduces a theoretical bias in the fit. We perform a quantitative study of the theoretical bias in dark matter direct detection, with a focus on assumptions regarding the dark matter interactions, and velocity distribution. We address this problem within the effective theory of isoscalar dark matter-nucleon interactions mediated by a heavy spin-1 or spin-0 particle. We analyze 24 benchmark points in the parameter space of the theory, using frequentist and Bayesian statistical methods. First, we simulate the data of future direct detection experiments assuming a momentum/velocity dependent dark matter-nucleon interaction, and an anisotropic dark matter velocity distribution. Then, we fit a constant scattering cross section, and an isotropic Maxwell-Boltzmann velocity distribution to the simulated data, thereby introducing a bias in the analysis. The best fit values of the dark matter particle mass differ from their benchmark values up to 2 standard deviations. The best fit values of the dark matter-nucleon coupling constant differ from their benchmark values up to several standard deviations. We conclude that common assumptions in dark matter direct detection are a source of potentially significant bias.

Riccardo Catena

2014-07-01

296

Compiler-Directed Instruction Duplication for Soft Error Detection  

Microsoft Academic Search

In this work, we experiment with complier-directed instruction duplication to detect soft errors in VLIW datapaths. Inthe proposed approach, the compiler determines the instruction schedule by balancing the permissible performance degradation with the required degree of duplication. Our experimental results show that our algorithms allow the designer to perform tradeoff analysis between performance and reliability.

Jie S. Hu; Feihui Li; Vijay Degalahal; Mahmut T. Kandemir; Narayanan Vijaykrishnan; Mary Jane Irwin

2005-01-01

297

Direct ice detection based on fiber optic sensor architecture  

Microsoft Academic Search

Ice growth on the wings of aircraft affects their aerodynamic performance and handling qualities which change depending on the location of the ice accretion. Ice detection technology has changed little over the last 30 years relying on indirect atmospheric conditions to determine the existence of icing conditions. This letter reports on a simple optical method to measure directly ice thickness

Aristidis A. Ikiades

2007-01-01

298

Direct detection of the inflationary gravitational wave background  

E-print Network

Inflation generically predicts a stochastic background of gravitational waves over a broad range of frequencies, from those accessible with cosmic microwave background (CMB) measurements, to those accessible directly with gravitational-wave detectors, like NASA's Big-Bang Observer (BBO) or Japan's Deci-Hertz Interferometer Gravitational-wave Observer (DECIGO), both currently under study. Here we investigate the detectability of the inflationary gravitational-wave background at BBO/DECIGO frequencies. To do so, we survey a range of slow-roll inflationary models consistent with constraints from the CMB and large-scale structure (LSS). We go beyond the usual assumption of power-law power spectra, which may break down given the 16 orders of magnitude in frequency between the CMB and direct detection, and solve instead the inflationary dynamics for four classes of inflaton potentials. Direct detection is possible in a variety of inflationary models, although probably not in any in which the gravitational-wave signal does not appear in the CMB polarization. However, direct detection by BBO/DECIGO can help discriminate between inflationary models that have the same slow-roll parameters at CMB/LSS scales.

Tristan L. Smith; Marc Kamionkowski; Asantha Cooray

2005-06-17

299

Impact of laser frequency offset on DQPSK direct detection  

Microsoft Academic Search

Frequency-offset impact on DQPSK direct detection is experimentally addressed with free-running sources. The heterodyned-measured frequency offset is related both with DQPSK BER performance and power penalty. Polarization-dependent delay impairment is isolated as well.

Lucia Marazzi; Paola Parolari; Pierpaolo Boffi; R. Siano; M. Feroldi; M. Martinelli

2005-01-01

300

Channel simulation for direct-detection optical communication systems  

NASA Technical Reports Server (NTRS)

A technique is described for simulating the random modulation imposed by atmospheric scintillation and transmitter pointing jitter on a direct-detection optical communication system. The system is capable of providing signal fading statistics which obey log-normal, beta, Rayleigh, Ricean, or chi-square density functions. Experimental tests of the performance of the channel simulator are presented.

Tycz, M.; Fitzmaurice, M. W.

1974-01-01

301

Directed energy active illumination for near-Earth object detection  

NASA Astrophysics Data System (ADS)

On 15 February 2013, a previously unknown ~20 m asteroid struck Earth near Chelyabinsk, Russia, releasing kinetic energy equivalent to ~570 kt TNT. Detecting objects like the Chelyabinsk impactor that are orbiting near Earth is a difficult task, in part because such objects spend much of their own orbits in the direction of the Sun when viewed from Earth. Efforts aimed at protecting Earth from future impacts will rely heavily on continued discovery. Ground-based optical observatory networks and Earth-orbiting spacecraft with infrared sensors have dramatically increased the pace of discovery. Still, less than 5% of near-Earth objects (NEOs) >=100 m/~100 Mt TNT have been identified, and the proportion of known objects decreases rapidly for smaller sizes. Low emissivity of some objects also makes detection by passive sensors difficult. A proposed orbiting laser phased array directed energy system could be used for active illumination of NEOs, enhancing discovery particularly for smaller and lower emissivity objects. Laser fiber amplifiers emit very narrow-band energy, simplifying detection. Results of simulated illumination scenarios are presented based on an orbiting emitter array with specified characteristics. Simulations indicate that return signals from small and low emissivity objects is strong enough to detect. The possibility for both directed and full sky blind surveys is discussed, and the resulting diameter and mass limits for objects in different observational scenarios. The ability to determine both position and speed of detected objects is also discussed.

Riley, Jordan; Lubin, Philip; Hughes, Gary B.; O'Neill, Hugh; Meinhold, Peter; Suen, Jonathan; Bible, Johanna; Johansson, Isabella E.; Griswold, Janelle; Cook, Brianna

2014-09-01

302

A new adaptive switching filter with directional impulse detection  

NASA Astrophysics Data System (ADS)

A novel adaptive switching filter (ASF) based on directional detection is proposed for denoising the images that are highly corrupted by impulse noise. The proposed algorithm employs an efficient noise detection mechanism. It first employs an efficient method to estimate the differences between the current pixel and its neighbors aligned with 28 directions. The current noise pixel is replaced by a median or a mean value within an adaptive filter window with respect to different noise densities. Experimental results show that the proposed approach can not only achieve very low miss-detection ratio and false-alarm ratio even up to high noise corruption, but also preserve the detailed information of an image very well.

Sun, Jing; Liu, Hui-gang; Zhang, Fu-hai

2014-03-01

303

A selective colorimetric and fluorometric ammonium ion sensor based on the H-aggregation of an aza-BODIPY with fused pyrazine rings.  

PubMed

The synthesis of a novel aza-BODIPY dye functionalized with fused pyrazine rings, suitable for use as a selective colorimetric and fluorometric sensor for NH(4)(+), is outlined. In addition to significant fluorescence quenching, an obvious colorimetric change from green to red-pink is observed enabling facile "naked-eye" detection of NH(4)(+). PMID:22006224

Liu, Hanzhuang; Mack, John; Guo, Qiuli; Lu, Hua; Kobayashi, Nagao; Shen, Zhen

2011-11-28

304

Sensitive colorimetric visualization of perfluorinated compounds using poly(ethylene glycol) and perfluorinated thiols modified gold nanoparticles.  

PubMed

In this work, we have developed a novel sensing strategy employing mixed poly(ethylene glycol)-terminated (PEG-thiols) and perfluoroalkyl-terminated (F-thiols) alkanethiols modified gold nanoparticles (Au@PEG-F NPs) as a probe to detect perfluorinated compounds (PFCs) from water samples. PEG-thiols with high density and long carbon chains make the Au NPs probe well-dispersed in solution and stable even in high concentration of salt solution; F-thiols provide specific fluorous-fluorous interactions to PFCs, which results in adsorption of PFCs on Au@PEG-F NPs. The adsorbed PFCs cause the aggregation of Au@PEG-F NPs probes and thus induce the insolubility of probes and precipitation directly from reaction solution due to the superhydrophobicity of perfluorocarbon monolayers, leading to color and absorbance response of the assay to PFCs. The preparation of the Au@PEG-F NPs probe is very simple, and the colorimetric assay based on this mechanism for the detection of PFCs is selective and convenient. Combined with UV-vis spectrophotometry, the assay demonstrates good sensitivities to PFCs with wide linear range. In the designed concentration range, the response of the colorimetric assay to long-chain PFCs (perfluoroalkyl chain ?7) is discerned even as the concentration of these PFCs is as low as 10 ?g L(-1). This low-cost and sensitive assay shows great potential to measure total PFCs in water samples. To the best of our knowledge, this is the first application of the specific fluorous-fluorous interactions and Au NPs based probes for colorimetric recognition for PFCs. PMID:24684731

Niu, Hongyun; Wang, Saihua; Zhou, Zhen; Ma, Yurong; Ma, Xunfeng; Cai, Yaqi

2014-05-01

305

Functional self-assembling bolaamphiphilic polydiacetylenes as colorimetric sensor scaffolds  

SciTech Connect

Conjugated polymers capable of responding to external stimuli by changes in optical, electrical or electrochemical properties can be used for the construction of direct sensing devices. Polydiacetylene-based systems are attractive for sensing applications due to their colorimetric response to changes in the local environment. Here we present the design, preparation and characterization of self-assembling functional bolaamphiphilic polydiacetylenes (BPDAs) inspired by Nature's strategy for membrane stabilization. We show that by placing polar headgroups on both ends of the diacetylene lipids in a transmembranic fashion, and altering the chemical nature of the polar surface residues, the conjugated polymers can be engineered to display a range of radiation-, thermal- and pH-induced colorimetric responses. We observed dramatic nanoscopic morphological transformations accompanying charge-induced chromatic transitions, suggesting that both side chain disordering and main chain rearrangement play important roles in altering the effective conjugation lengths of the poly(ene-yne). These results establish the foundation for further development of BPDA-based colorimetric sensors.

Song, Jie; Cisar, Justin S.; Bertozzi, Carolyn R.

2004-05-28

306

Directional Dark Matter Detection Beyond the Neutrino Bound  

E-print Network

Coherent scattering of solar, atmospheric and diffuse supernovae neutrinos creates an irreducible background for direct dark matter experiments with sensitivities to WIMP-nucleon spin-independent scattering cross-sections of 10^(-46)-10^(-48) cm^2, depending on the WIMP mass. Even if one could eliminate all other backgrounds, this "neutrino floor" will limit future experiments with projected sensitivities to cross-sections as small as 10^(-48) cm^2. Direction-sensitive detectors have the potential to study dark matter beyond the neutrino bound by fitting event distributions in multiple dimensions: recoil kinetic energy, recoil track angle with respect to the sun, and event time. This work quantitatively explores the impact of direction-sensitivity on the neutrino bound in dark matter direct detection.

Philipp Grothaus; Malcolm Fairbairn; Jocelyn Monroe

2014-09-30

307

Small-signal analysis of OOFDM signal transmission with directly modulated laser and direct detection.  

PubMed

This work presents a small-signal analysis for investigating the transmission performance of optical orthogonal frequency division multiplexing signals with a directly modulated DFB laser (DML). The analysis shows the positive chirp of DMLs can intensify power fading after transmission with positive dispersion and provide power gain instead with negative dispersion. The power of subcarrier-to-subcarrier intermixing interference after square-law direct detection, however, is independent on the sign of dispersion. PMID:21263483

Wei, Chia-Chien

2011-01-15

308

Spaceborne Simulations of Two Direct-Detection Doppler Lidar Techniques  

NASA Technical Reports Server (NTRS)

Direct-detection (or incoherent) lidar is now a proven technique for measuring winds in the atmosphere. Over the last few years, several types of direct-detection lidar have evolved. These methods rely on Fabry-Perot interferometers(also termed etalons) or other narrow-passband filters to provide the required spectral resolution. One method, now called the edge (EDG) technique, uses a sharply-sloping filter and measures changes in the filter transmission caused by Doppler shifting of the laser wavelength. A variation of the EDG method, called the double-edge (DEDG) technique, uses two filters. The molecular DEDG method was first demonstrated by Chanin et al. for stratospheric measurements and more recently Korb et al. successfully demonstrated the aerosol DEDG through the troposphere. A second method, here termed the multi-channel (MC) technique, measures Doppler shifts by observing angular displacement of a Fabry-Perot fringe in a spatially resolving detector. The EDG technique thus employs the Fabry-Perot to convert the frequency shift into an amplitude signal, while the MC technique uses the Fabry-Perot to resolve the spectral signature which is then fitted to determine the centroid. The focus of this presentation is on the DEDG and MC methods because these are viewed as the current state of the art in direct-detection lidar. Successful ground-based demonstrations of direct-detection wind measurements have resulted in proposals for spaceborne systems. With this new emphasis on spaceborne systems comes the need for accurate prediction of spaceborne direct-detection Doppler lidar performance. Previously, the EDG and MC methods have been compared although only for aerosol Doppler systems. A recent paper by McGill and Spinhirne compares the DEDG and MC methods in a non-system specific manner for both the aerosol and molecular Doppler systems. The purpose of this presentation is to extend the previous work of McGill and Spinhirne to examine the performance of spaceborne profiling systems. Particular emphasis will be placed on the molecular systems, as these are viewed as the strength of direct-detection Doppler lidar.

McGill, Matthew J.; Li, Steve X.

1998-01-01

309

[Gold nanoparticle-aptamer based colorimetric biosensing assays].  

PubMed

The single strand nucleic acid based aptamer could bound to targets with high sensitivity and specificity. Gold nanoparticles have strong particle space optical effects and could take a color change from red to blue when the dispersed nanoparticles were aggregated. Aptamer could be immobilized through covalent coupling or direct adsorption to the surface of gold nanoparticle. Various approaches have been designed for biosensing based on the target induced aptamer-gold nanoparticle system color changes. The recent developments in the gold nanoparticle-aptamer based colorimetric biosensing assays were reviewed and the directions for future research were discussed and proposed. PMID:25508710

Liu, Jin-chuan; Lü, Zhen-zhen; Chen, Ai-liang

2014-08-01

310

[Gold nanoparticle-aptamer based colorimetric biosensing assays].  

PubMed

The single strand nucleic acid based aptamer could bound to targets with high sensitivity and specificity. Gold nanoparticles have strong particle space optical effects and could take a color change from red to blue when the dispersed nanoparticles were aggregated. Aptamer could be immobilized through covalent coupling or direct adsorption to the surface of gold nanoparticle. Various approaches have been designed for biosensing based on the target induced aptamer-gold nanoparticle system color changes. The recent developments in the gold nanoparticle-aptamer based colorimetric biosensing assays were reviewed and the directions for future research were discussed and proposed. PMID:25474931

Liu, Jin-chuan; Lü, Zhen-zhen; Chen, Ai-liang

2014-08-01

311

Status of the XENON Direct Dark Matter Detection Experiment  

SciTech Connect

The XENON Collaboration is developing a dark matter detector using liquid xenon (LXe) as the target medium for detecting weakly interacting massive particles (WIMPs). The goal of the collaboration is to operate an array of LXe time projection chambers (TPCs) with 1000 times greater sensitivity to WIMPs than current direct dark matter detection experiments. Recent measurements by members of the XENON collaboration have demonstrated the promise of the LXe TPC approach, particularly measurements of the scintillation efficiency and charge response of LXe to nuclear recoils. The collaboration plans to operate a 10 kg fiducial volume prototype, XENON10, underground in the spring of 2006.

Hasty, Richard [Yale University, New Haven, CT (United States)

2006-07-11

312

Status of the XENON Direct Dark Matter Detection Experiment  

NASA Astrophysics Data System (ADS)

The XENON Collaboration is developing a dark matter detector using liquid xenon (LXe) as the target medium for detecting weakly interacting massive particles (WIMPs). The goal of the collaboration is to operate an array of LXe time projection chambers (TPCs) with 1000 times greater sensitivity to WIMPs than current direct dark matter detection experiments. Recent measurements by members of the XENON collaboration have demonstrated the promise of the LXe TPC approach, particularly measurements of the scintillation efficiency and charge response of LXe to nuclear recoils. The collaboration plans to operate a 10 kg fiducial volume prototype, XENON10, underground in the spring of 2006.

Hasty, Richard

2006-07-01

313

Status of the XENON Direct Dark Matter Detection Experiment  

NASA Astrophysics Data System (ADS)

The XENON collaboration is developing a dark matter detector using liquid xenon (LXe) as the target medium for detecting Weakly Interacting Massive Particles (WIMPs). The goal of the collaboration is to operate an array of LXe time projection chambers (TPCs) with 1000 times greater sensitivity to WIMPs than current direct dark matter detection experiments. Recent measurements by members of the XENON collaboration demonstrate the promise of the LXe TPC approach, particularly measurements of the scintillation efficiency and charge extraction from nuclear recoils in LXe. The collaboration is currently installing a 10 kg fiducial volume prototype in the Gran Sasso National Laboratory in Italy for low background operation.

Hasty, Richard

2006-04-01

314

Nanoparticle-catalyzed reductive bleaching for fabricating turn-off and enzyme-free amplified colorimetric bioassays.  

PubMed

Nanoparticle-catalyzed reductive bleaching reactions of colored substrates are emerging as a class of novel indicator reactions for fabricating enzyme-free amplified colorimetric biosensing (turn-off mode), which are exactly opposite to the commonly used oxidative coloring processes of colorless substrates in traditional enzyme-catalyzed amplified colorimetric bioassays (turn-on mode). In this work, a simple theoretical analysis shows that the sensitivity of this colorimetric bioassay can be improved by increasing the amplification factor (kcat?t), or enhancing the binding affinity between analyte and receptor (Kd), or selecting the colored substrates with high extinction coefficients (?). Based on this novel strategy, we have developed a turn-off and cost-effective amplified colorimetric thrombin aptasensor. This aptasensor made full use of sandwich binding of two affinity aptamers for increased specificity, magnetic particles for easy separation and enrichment, and gold nanoparticle (AuNP)-catalyzed reductive bleaching reaction to generate the amplified colorimetric signal. With 4-nitrophenol (4-NP) as the non-dye colored substrate, colorimetric bioassay of thrombin was achieved by the endpoint method with a detection limit of 91pM. In particular, when using methylene blue (MB) as the substrate, for the first time, a more convenient and efficient kinetic-based colorimetric thrombin bioassay was achieved without the steps of acidification termination and magnetic removal of particles, with a low detection limit of 10pM, which was superior to the majority of the existing colorimetric thrombin aptasensors. The proposed colorimetric protocol is expected to hold great promise in field analysis and point-of-care applications. PMID:23962710

Li, Wei; Qiang, Weibing; Li, Jie; Li, Hui; Dong, Yifan; Zhao, Yaju; Xu, Danke

2014-01-15

315

Optimetric system facilitates colorimetric and fluorometric measurements  

NASA Technical Reports Server (NTRS)

Compact, unitary optimetric systems uses a single device for colorimetric, fluorometric and spectral absorption measurements. The basic element of the unitary systems is a test cell containing filter elements with uniquely fabricated lenses.

Haley, F. C.

1968-01-01

316

Hunting electroweakinos at future hadron colliders and direct detection experiments  

E-print Network

We analyse the mass reach for electroweakinos at future hadron colliders and their interplay with direct detection experiments. Motivated by the LHC data, we focus on split supersymmetry models with different electroweakino spectra. We find for example that a 100 TeV collider may explore Winos up to ~ 7 TeV in low scale gauge mediation models or thermal Wino dark matter around 3 TeV in models of anomaly mediation with long-lived Winos. We show moreover how collider searches and direct detection experiments have the potential to cover large part of the parameter space even in scenarios where the lightest neutralino does not contribute to the whole dark matter relic density.

Giovanni Grilli di Cortona

2014-12-18

317

Receiver processing for direct-detection optical communication systems.  

NASA Technical Reports Server (NTRS)

A model that is sufficiently general to describe the predominant statistical characteristics of the output of many real optical detectors is formulated. This model is used to study the optimum receiver processing for direct-detection optical communication systems. In particular, the structures of detectors and estimators for filtered doubly stochastic Poisson processes (DSPP) observed in additive white Gaussian noise are considered. Representations for the posterior statistics of a vector Markov process that modulates the intensity of the DSPP are obtained.

Hoversten, E. V.; Snyder, D. L.

1972-01-01

318

Gif Lectures on direct detection of Dark Matter  

E-print Network

These notes cover some of the topics associated with direct detection of dark matter at an introductory level. The general principles of dark matter search are summarized. The current status of some experiments is described, with an emphasis on bolometric and noble liquid techniques. Plots and illustrations associated to these notes may be found on transparencies presented during the lecture, on the web site of Gif school 2009.

Eric Armengaud

2010-03-11

319

Future Directions for the Early Detection of Recurrent Breast Cancer  

PubMed Central

The main goal of follow-up care after breast cancer treatment is the early detection of disease recurrence. In this review, we emphasize the multidisciplinary approach to this continuity of care from surgery, medical oncology, and radiology. Challenges within each setting are briefly addressed as a means of discussion for the future directions of an effective and efficient surveillance plan of post-treatment breast cancer care. PMID:24790657

Schneble, Erika J.; Graham, Lindsey J.; Shupe, Matthew P.; Flynt, Frederick L.; Banks, Kevin P.; Kirkpatrick, Aaron D.; Nissan, Aviram; Henry, Leonard; Stojadinovic, Alexander; Shumway, Nathan M.; Avital, Itzhak; Peoples, George E.; Setlik, Robert F.

2014-01-01

320

Closing supersymmetric resonance regions with direct detection experiments  

SciTech Connect

One of the few remaining ways that neutralinos could potentially evade constraints from direct detection experiments is if they annihilate through a resonance, as can occur if 2m{sub ?{sup 0}} falls within about ?10% of either m{sub A/H}, m{sub h}, or m{sub Z}. Assuming a future rate of progress among direct detection experiments that is similar to that obtained over the past decade, we project that within 7 years the light Higgs and Z pole regions will be entirely closed, while the remaining parameter space near the A/H resonance will require that 2m{sub ?{sup 0}} be matched to the central value (near m{sub A}) to within less than 4%. At this rate of progress, it will be a little over a decade before multi-ton direct detection experiments will be able to close the remaining, highly-tuned, regions of the A/H resonance parameter space.

Kelso, Chris [Department of Physics and Astronomy, University of Utah, Salt Lake City, Utah 84112 (United States)

2014-06-24

321

Figure of merit for direct-detection optical channels  

NASA Technical Reports Server (NTRS)

The capacity and sensitivity of a direct-detection optical channel are calculated and compared to those of a white Gaussian noise channel. Unlike Gaussian channels in which the receiver performance can be characterized using the noise temperature, the performance of the direct-detection channel depends on both signal and background noise, as well as the ratio of peak to average signal power. Because of the signal-power dependence of the optical channel, actual performance of the channel can be evaluated only by considering both transmit and receive ends of the systems. Given the background noise power and the modulation bandwidth, however, the theoretically optimum receiver sensitivity can be calculated. This optimum receiver sensitivity can be used to define the equivalent receiver noise temperature and calculate the corresponding G/T product. It should be pointed out, however, that the receiver sensitivity is a function of signal power, and care must be taken to avoid deriving erroneous projections of the direct-detection channel performance.

Chen, C.-C.

1992-01-01

322

The Tevatron at the frontier of dark matter direct detection  

NASA Astrophysics Data System (ADS)

Direct detection of dark matter (DM) requires an interaction of dark matter particles with nucleons. The same interaction can lead to dark matter pair production at a hadron collider, and with the addition of initial state radiation this may lead to mono-jet signals. Mono-jet searches at the Tevatron can thus place limits on DM direct detection rates. We study these bounds both in the case where there is a contact interaction between DM and the standard model and where there is a mediator kinematically accessible at the Tevatron. We find that in many cases the Tevatron provides the current best limit, particularly for light dark matter, below ˜5 GeV, a and for spin dependent interactions. Non-standard dark matter candidates are also constrained. The introduction of a light mediator significantly weakens the collider bound. A direct detection discovery that is in apparent conflict with mono-jet limits will thus point to a new light state coupling the standard model to the dark sector. Mono-jet searches with more luminosity and including the spectrum shape in the analysis can improve the constraints on DM-nucleon scattering cross section.

Bai, Yang; Fox, Patrick J.; Harnik, Roni

2010-12-01

323

Gold nanoparticles based colorimetric nanodiagnostics for cancer and infectious diseases  

NASA Astrophysics Data System (ADS)

Traditional in vitro diagnostics requires specialized laboratories and costly instrumentation, both for the amplification of nucleic acid targets (usually achieved by PCR) and for the assay readout, often based on fluorescence. We are developing hybrid nanomaterials-based sensors for the rapid and low-cost diagnosis of various disease biomarkers, for applications in portable platforms for diagnostics at the point-of-care. To this aim, we exploited the size and distancedependent optical properties of gold nanoparticles (AuNPs) to achieve colorimetric detection. Moreover, in order to avoid the complexity of thermal cycles associated to traditional PCR, the design of our systems includes signal amplification schemes, achieved by the use of enzymes (nucleases, helicase) or DNAzymes. Focused on instrument-free and sensitive detection, we carefully combined the intrinsic sensitivity by multivalency of functionalized AuNPs with isothermal and non-stringent enzyme-aided reaction conditions, controlled AuNPs aggregates, universal reporters and magnetic microparticles, the latter used both as a substrate and as a means for the colorimetric detection. We obtained simple and robust assays for the sensitive (pM range or better) naked-eye detection of cancer or infectious diseases (HPV, HCV) biomarkers, requiring no instrumentation except for a simple heating plate. Finally, we are also developing non-medical applications of these bio-nanosensors, such as in the development of on-field rapid tests for the detection of pollutants and other food and water contaminants.

Valentini, Paola; Persano, Stefano; Cecere, Paola; Sabella, Stefania; Pompa, Pier Paolo

2014-03-01

324

Magnetic Bead-Based Colorimetric Immunoassay for Aflatoxin B1 Using Gold Nanoparticles  

PubMed Central

A competitive colorimetric immunoassay for the detection of aflatoxin B1 (AFB) has been established using biofunctionalized magnetic beads (MBs) and gold nanoparticles (GNPs). Aflatoxin B1-bovine serum albumin conjugates (AFB-BSA) modified MBs were employed as capture probe, which could specifically bind with GNP-labeled anti-AFB antibodies through immunoreaction, while such specific binding was competitively inhibited by the addition of AFB. After magnetic separation, the supernatant solution containing unbound GNPs was directly tested by UV-Vis spectroscopy. The absorption intensity was directly proportional to the AFB concentration. The influence of GNP size, incubation time and pH was investigated in detail. After optimization, the developed method could detect AFB in a linear range from 20 to 800 ng/L, with the limit of detection at 12 ng/L. The recoveries for spiked maize samples ranged from 92.8% to 122.0%. The proposed immunoassay provides a promising approach for simple, rapid, specific and cost-effective detection of toxins in the field of food safety. PMID:25405511

Wang, Xu; Niessner, Reinhard; Knopp, Dietmar

2014-01-01

325

Magnetic bead-based colorimetric immunoassay for aflatoxin B1 using gold nanoparticles.  

PubMed

A competitive colorimetric immunoassay for the detection of aflatoxin B1 (AFB) has been established using biofunctionalized magnetic beads (MBs) and gold nanoparticles (GNPs). Aflatoxin B1-bovine serum albumin conjugates (AFB-BSA) modified MBs were employed as capture probe, which could specifically bind with GNP-labeled anti-AFB antibodies through immunoreaction, while such specific binding was competitively inhibited by the addition of AFB. After magnetic separation, the supernatant solution containing unbound GNPs was directly tested by UV-Vis spectroscopy. The absorption intensity was directly proportional to the AFB concentration. The influence of GNP size, incubation time and pH was investigated in detail. After optimization, the developed method could detect AFB in a linear range from 20 to 800 ng/L, with the limit of detection at 12 ng/L. The recoveries for spiked maize samples ranged from 92.8% to 122.0%. The proposed immunoassay provides a promising approach for simple, rapid, specific and cost-effective detection of toxins in the field of food safety. PMID:25405511

Wang, Xu; Niessner, Reinhard; Knopp, Dietmar

2014-01-01

326

(In)direct Detection of Boosted Dark Matter  

E-print Network

We initiate the study of novel thermal dark matter (DM) scenarios where present-day annihilation of DM in the galactic center produces boosted stable particles in the dark sector. These stable particles are typically a subdominant DM component, but because they are produced with a large Lorentz boost in this process, they can be detected in large volume terrestrial experiments via neutral-current-like interactions with electrons or nuclei. This novel DM signal thus combines the production mechanism associated with indirect detection experiments (i.e. galactic DM annihilation) with the detection mechanism associated with direct detection experiments (i.e. DM scattering off terrestrial targets). Such processes are generically present in multi-component DM scenarios or those with non-minimal DM stabilization symmetries. As a proof of concept, we present a model of two-component thermal relic DM, where the dominant heavy DM species has no tree-level interactions with the standard model and thus largely evades direct and indirect DM bounds. Instead, its thermal relic abundance is set by annihilation into a subdominant lighter DM species, and the latter can be detected in the boosted channel via the same annihilation process occurring today. Especially for dark sector masses in the 10 MeV-10 GeV range, the most promising signals are electron scattering events pointing toward the galactic center. These can be detected in experiments designed for neutrino physics or proton decay, in particular Super-K and its upgrade Hyper-K, as well as the PINGU/MICA extensions of IceCube. This boosted DM phenomenon highlights the distinctive signatures possible from non-minimal dark sectors.

Kaustubh Agashe; Yanou Cui; Lina Necib; Jesse Thaler

2014-05-28

327

(In)direct detection of boosted dark matter  

NASA Astrophysics Data System (ADS)

We initiate the study of novel thermal dark matter (DM) scenarios where present-day annihilation of DM in the galactic center produces boosted stable particles in the dark sector. These stable particles are typically a subdominant DM component, but because they are produced with a large Lorentz boost in this process, they can be detected in large volume terrestrial experiments via neutral-current-like interactions with electrons or nuclei. This novel DM signal thus combines the production mechanism associated with indirect detection experiments (i.e. galactic DM annihilation) with the detection mechanism associated with direct detection experiments (i.e. DM scattering off terrestrial targets). Such processes are generically present in multi-component DM scenarios or those with non-minimal DM stabilization symmetries. As a proof of concept, we present a model of two-component thermal relic DM, where the dominant heavy DM species has no tree-level interactions with the standard model and thus largely evades direct and indirect DM bounds. Instead, its thermal relic abundance is set by annihilation into a subdominant lighter DM species, and the latter can be detected in the boosted channel via the same annihilation process occurring today. Especially for dark sector masses in the 10 MeV–10 GeV range, the most promising signals are electron scattering events pointing toward the galactic center. These can be detected in experiments designed for neutrino physics or proton decay, in particular Super-K and its upgrade Hyper-K, as well as the PINGU/MICA extensions of IceCube. This boosted DM phenomenon highlights the distinctive signatures possible from non-minimal dark sectors.

Agashe, Kaustubh; Cui, Yanou; Necib, Lina; Thaler, Jesse

2014-10-01

328

Direct real-time detection of vapors from explosive compounds.  

PubMed

The real-time detection of vapors from low volatility explosives including PETN, tetryl, RDX, and nitroglycerine along with various compositions containing these substances was demonstrated. This was accomplished with an atmospheric flow tube (AFT) using a nonradioactive ionization source coupled to a mass spectrometer. Direct vapor detection was accomplished in less than 5 s at ambient temperature without sample preconcentration. The several seconds of residence time of analytes in the AFT provided a significant opportunity for reactant ions to interact with analyte vapors to achieve ionization. This extended reaction time, combined with the selective ionization using the nitrate reactant ions (NO3(-) and NO3(-)·HNO3), enabled highly sensitive explosives detection from explosive vapors present in ambient laboratory air. Observed signals from diluted explosive vapors indicated detection limits below 10 ppqv using selected ion monitoring (SIM) of the explosive-nitrate adduct at m/z 349, 378, 284, and 289 for tetryl, PETN, RDX, and NG, respectively. Also provided is a demonstration of the vapor detection from 10 different energetic formulations sampled in ambient laboratory air, including double base propellants, plastic explosives, and commercial blasting explosives using SIM for the NG, PETN, and RDX product ions. PMID:24090362

Ewing, Robert G; Clowers, Brian H; Atkinson, David A

2013-11-19

329

Direct Real-Time Detection of Vapors from Explosive Compounds  

SciTech Connect

The real-time detection of vapors from low volatility explosives including PETN, tetryl, RDX and nitroglycerine along with various compositions containing these substances is demonstrated. This was accomplished with an atmospheric flow tube (AFT) using a non-radioactive ionization source and coupled to a mass spectrometer. Direct vapor detection was demonstrated in less than 5 seconds at ambient temperature without sample pre-concentration. The several seconds of residence time of analytes in the AFT provides a significant opportunity for reactant ions to interact with analyte vapors to achieve ionization. This extended reaction time, combined with the selective ionization using the nitrate reactant ions (NO3- and NO3-•HNO3), enables highly sensitive explosives detection. Observed signals from diluted explosive vapors indicate detection limits below 10 ppqv using selected ion monitoring (SIM) of the explosive-nitrate adduct at m/z 349, 378, 284 and 289 for tetryl, PETN, RDX and NG respectively. Also provided is a demonstration of the vapor detection from 10 different energetic formulations, including double base propellants, plastic explosives and commercial blasting explosives using SIM for the NG, PETN and RDX product ions.

Ewing, Robert G.; Clowers, Brian H.; Atkinson, David A.

2013-10-03

330

Direct and indirect detection of dissipative dark matter  

NASA Astrophysics Data System (ADS)

We study the constraints from direct detection and solar capture on dark matter scenarios with a subdominant dissipative component. This dissipative dark matter component in general has both a symmetric and asymmetric relic abundance. Dissipative dynamics allow this subdominant dark matter component to cool, resulting in its partial or total collapse into a smaller volume inside the halo (e.g., a dark disk) as well as a reduced thermal velocity dispersion compared to that of normal cold dark matter. We first show that these features considerably relax the limits from direct detection experiments on the couplings between standard model (SM) particles and dissipative dark matter. On the other hand, indirect detection of the annihilation of the symmetric dissipative dark matter component inside the Sun sets stringent and robust constraints on the properties of the dissipative dark matter. In particular, IceCube observations force dissipative dark matter particles with mass above 50 GeV to either have a small coupling to the SM or a low local density in the solar system, or to have a nearly asymmetric relic abundance. Possible helioseismology signals associated with purely asymmetric dissipative dark matter are discussed, with no present constraints.

Fan, JiJi; Katz, Andrey; Shelton, Jessie

2014-06-01

331

Toward Direct Detection of Hot Jupiters with Precision Closure Phase  

NASA Astrophysics Data System (ADS)

Direct detection of thermal emission from nearby hot Jupiters has greatly advanced our knowledge of extrasolar planets in recent years. Since hot Jupiter systems can be regarded as analogs of high-contrast binaries, ground-based infrared long-baseline interferometers have the potential to resolve them and detect their thermal emission with precision closure phase—a method that is immune to the systematic errors induced by the Earth's atmosphere. Here we present closure phase studies toward direct detection of nearby hot Jupiters using the CHARA interferometer array outfitted with the MIRC instrument. We find much larger systematic errors than expected in our observations, most likely caused by dispersion across different wavelengths. We also find that using higher spectral resolution modes (e.g., R=150) can significantly reduce the systematics. By combining all calibrators in an observing run together, we are able to roughly re-calibrate the lower spectral resolution data, allowing us to obtain upper limits of the star-planet contrast ratios of ? And b across the H band. The data also allow us to get a refined stellar radius of 1.625±0.011R?. Our best upper limit corresponds to a contrast ratio of 2.1×103:1 with 90% confidence level at 1.52?m, suggesting that we are starting to have the capability of constraining atmospheric models of hot Jupiters with interferometry.

Zhao, M.; Monnier, J. D.; Che, X.; Pedretti, E.; Thureau, N.

2014-09-01

332

Phase space distribution and directional direct detection of dark matter weakly interacting massive particles  

NASA Astrophysics Data System (ADS)

There is overwhelming evidence for dark matter in the Universe. Particles of a new kind are excellent dark matter candidates, but they have not been detected yet. Dozens of detectors are attempting to find them directly, analyzing their interaction with target nuclei underground, and indirectly, searching for their annihilation products. New techniques for the laboratory direct detection of dark matter weakly interacting massive particles (WIMPs) are sensitive to the recoil direction of the struck nuclei. This thesis is devoted to a study of the distribution and directional direct detection of dark matter WIMPs. We analyze the effect of the Sun's gravitational field on the phase-space distribution of unbound dark matter particles approaching the Earth. We determine the phase-space distribution of the flow both numerically, tracing particle trajectories back in time, and analytically, providing a simple correct relation between the velocity of particles at infinity and at the Earth. We use our results to produce sky maps of the distribution of arrival directions of dark matter particles on Earth at various times of the year. We assume various Maxwellian velocity distributions at infinity describing the standard dark halo and streams of dark matter. We illustrate the formation of a ring, analogous to the Einstein ring, when the Earth is directly downstream of the Sun. We resolve discrepancies in previous analyses of the flow of collisionless dark matter particles in the Sun's gravitational field. We compute and compare the directional recoil rates for several WIMP velocity distributions including the standard dark halo and anisotropic models such as Sikivie's late-infall halo model and logarithmic-ellipsoidal models. Since some detectors may be unable to distinguish the beginning of the recoil track from its end, we introduce a "folded" directional recoil rate that resolve this lack of head-tail discrimination. We compute the CS 2 and CF 4 exposures required to distinguish a signal from an isotropic background noise, and find that the "folded" directional recoil rate is effective for the standard dark halo and some but not all anisotropic models.

Alenazi, Moqbil Salem T.

333

Clustering and community detection in directed networks: A survey  

NASA Astrophysics Data System (ADS)

Networks (or graphs) appear as dominant structures in diverse domains, including sociology, biology, neuroscience and computer science. In most of the aforementioned cases graphs are directed - in the sense that there is directionality on the edges, making the semantics of the edges nonsymmetric as the source node transmits some property to the target one but not vice versa. An interesting feature that real networks present is the clustering or community structure property, under which the graph topology is organized into modules commonly called communities or clusters. The essence here is that nodes of the same community are highly similar while on the contrary, nodes across communities present low similarity. Revealing the underlying community structure of directed complex networks has become a crucial and interdisciplinary topic with a plethora of relevant application domains. Therefore, naturally there is a recent wealth of research production in the area of mining directed graphs - with clustering being the primary method sought and the primary tool for community detection and evaluation. The goal of this paper is to offer an in-depth comparative review of the methods presented so far for clustering directed networks along with the relevant necessary methodological background and also related applications. The survey commences by offering a concise review of the fundamental concepts and methodological base on which graph clustering algorithms capitalize on. Then we present the relevant work along two orthogonal classifications. The first one is mostly concerned with the methodological principles of the clustering algorithms, while the second one approaches the methods from the viewpoint regarding the properties of a good cluster in a directed network. Further, we present methods and metrics for evaluating graph clustering results, demonstrate interesting application domains and provide promising future research directions.

Malliaros, Fragkiskos D.; Vazirgiannis, Michalis

2013-12-01

334

Quantitative colorimetric measurement of cellulose degradation under microbial culture conditions.  

PubMed

We have developed a simple, rapid, quantitative colorimetric assay to measure cellulose degradation based on the absorbance shift of Congo red dye bound to soluble cellulose. We term this assay "Congo Red Analysis of Cellulose Concentration," or "CRACC." CRACC can be performed directly in culture media, including rich and defined media containing monosaccharides or disaccharides (such as glucose and cellobiose). We show example experiments from our laboratory that demonstrate the utility of CRACC in probing enzyme kinetics, quantifying cellulase secretion, and assessing the physiology of cellulolytic organisms. CRACC complements existing methods to assay cellulose degradation, and we discuss its utility for a variety of applications. PMID:22391973

Haft, Rembrandt J F; Gardner, Jeffrey G; Keating, David H

2012-04-01

335

Ultrabroadband direct detection of nonclassical photon statistics at telecom wavelength  

PubMed Central

Broadband light sources play essential roles in diverse fields, such as high-capacity optical communications, optical coherence tomography, optical spectroscopy, and spectrograph calibration. Although a nonclassical state from spontaneous parametric down-conversion may serve as a quantum counterpart, its detection and characterization have been a challenging task. Here we demonstrate the direct detection of photon numbers of an ultrabroadband (110?nm FWHM) squeezed state in the telecom band centred at 1535?nm wavelength, using a superconducting transition-edge sensor. The observed photon-number distributions violate Klyshko's criterion for the nonclassicality. From the observed photon-number distribution, we evaluate the second- and third-order correlation functions, and characterize a multimode structure, which implies that several tens of orthonormal modes of squeezing exist in the single optical pulse. Our results and techniques open up a new possibility to generate and characterize frequency-multiplexed nonclassical light sources for quantum info-communications technology. PMID:24694515

Wakui, Kentaro; Eto, Yujiro; Benichi, Hugo; Izumi, Shuro; Yanagida, Tetsufumi; Ema, Kazuhiro; Numata, Takayuki; Fukuda, Daiji; Takeoka, Masahiro; Sasaki, Masahide

2014-01-01

336

Ultrabroadband direct detection of nonclassical photon statistics at telecom wavelength.  

PubMed

Broadband light sources play essential roles in diverse fields, such as high-capacity optical communications, optical coherence tomography, optical spectroscopy, and spectrograph calibration. Although a nonclassical state from spontaneous parametric down-conversion may serve as a quantum counterpart, its detection and characterization have been a challenging task. Here we demonstrate the direct detection of photon numbers of an ultrabroadband (110 nm FWHM) squeezed state in the telecom band centred at 1535 nm wavelength, using a superconducting transition-edge sensor. The observed photon-number distributions violate Klyshko's criterion for the nonclassicality. From the observed photon-number distribution, we evaluate the second- and third-order correlation functions, and characterize a multimode structure, which implies that several tens of orthonormal modes of squeezing exist in the single optical pulse. Our results and techniques open up a new possibility to generate and characterize frequency-multiplexed nonclassical light sources for quantum info-communications technology. PMID:24694515

Wakui, Kentaro; Eto, Yujiro; Benichi, Hugo; Izumi, Shuro; Yanagida, Tetsufumi; Ema, Kazuhiro; Numata, Takayuki; Fukuda, Daiji; Takeoka, Masahiro; Sasaki, Masahide

2014-01-01

337

Direct Detection of Gravity Waves from Neutron Stars  

E-print Network

In light of the discovery of the first-ever double pulsar system, PSR J0737-3039, we re-examine an earlier proposal to directly detect gravity waves from neutron stars, which was predicated on a hypothetical system almost identical to the later discovered double pulsar. We re-derive the effect in more detail, and confirm the initial estimate--sometimes doubted in the literature--that it includes a 1/b dependence, where b is the impact parameter of a pulsar with respect to its foreground, gravity-wave emitting, neutron star companion. A coherent modulation in pulsar time-of-arrival measurements of 10 nano-sec/sec is possible. A one-year intermittent experiment on an instrument comparable to the SKA could thus detect the exceedingly faint gravity waves from individual neutron stars.

Redouane Al Fakir; William G. Unruh

2008-05-24

338

Problem detection during tripping operations in horizontal and directional wells  

SciTech Connect

Most directional well drilling problems detected in Brazil, and also verbally reported by service companies abroad, occur during tripping operations. A comprehensive research program was undertaken to study this problem. The work is summarized in this paper, and shows the development of a field analysis procedure that proved to be reliable and thus translates into significant cost savings. The field data was obtained using an in-house mud logging offshore unit and service companies` drilling sensors. The analysis was performed using the new developed method--Two Stage Type Curve Matching: an alert hook load expert system, followed by a pseudo friction factor ``signature`` analysis. Field results showed this to be useful for early borehole detection.

Cordoso, J.V. Jr. [Petrobras, Rio de Janeiro (Brazil); Maidla, E.E.; Idagawa, L.S. [State Univ. in Campinas (Brazil)

1995-06-01

339

Theoretical Interpretation of Experimental Data from Direct Dark Matter Detection  

E-print Network

Weakly Interacting Massive Particles (WIMPs) are one of the leading candidates for Dark Matter. Currently, the most promising method to detect WIMPs is the direct detection of the recoil energy deposited in a low-background laboratory detector due to elastic WIMP-nucleus scattering. So far the usual procedure has been to predict the event rate of direct detection of WIMPs based on some model(s) of the Galactic halo from cosmology and of WIMPs from elementary particle physics. The aim of this work is to invert this process. In this thesis I present methods which allow to reconstruct (the moments of) the WIMP velocity distribution function as well as to determine the WIMP mass from the recoil energy spectrum as well as from experimental data directly. The reconstruction of the velocity distribution function has been further extended to take into account the annual modulation of the event rate. Moreover, the reconstruction of the amplitude of the annual modulation of the velocity distribution and an alternative, better way for confirming the annual modulation of the event rate have been discussed. On the other hand, the determination of the WIMP mass by combining two (or more) experiments with different detector materials has been developed. All formulae and expressions given here are not only independent of the model of Galactic halo but also of that of WIMPs. This means that we need neither the as yet unknown WIMP density near the Earth nor the WIMP-nucleus cross section. The only information which we need is the measured recoil energies and their measuring times.

Chung-Lin Shan

2007-07-03

340

WIMP physics with ensembles of direct-detection experiments  

NASA Astrophysics Data System (ADS)

The search for weakly-interacting massive particle (WIMP) dark matter is multi-pronged. Ultimately, the WIMP-dark-matter picture will only be confirmed if different classes of experiments see consistent signals and infer the same WIMP properties. In this work, we review the ideas, methods, and status of direct-detection searches. We focus in particular on extracting WIMP physics (WIMP interactions and phase-space distribution) from direct-detection data in the early discovery days when multiple experiments see of order dozens to hundreds of events. To demonstrate the essential complementarity of different direct-detection experiments in this context, we create mock data intended to represent the data from the near-future Generation 2 experiments. We consider both conventional supersymmetry-inspired benchmark points (with spin-independent and -dependent elastic cross sections just below current limits), as well as benchmark points for other classes of models (inelastic and effective-operator paradigms). We also investigate the effect on parameter estimation of loosening or dropping the assumptions about the local WIMP phase-space distribution. We arrive at two main conclusions. Firstly, teasing out WIMP physics with experiments depends critically on having a wide set of detector target materials, spanning a large range of target nuclear masses and spin-dependent sensitivity. It is also highly desirable to obtain data from low-threshold experiments. Secondly, a general reconstruction of the local WIMP velocity distribution, which will only be achieved if there are multiple experiments using different target materials, is critical to obtaining a robust and unbiased estimate of the WIMP mass.

Peter, Annika H. G.; Gluscevic, Vera; Green, Anne M.; Kavanagh, Bradley J.; Lee, Samuel K.

2014-12-01

341

Direct detection of baryogenesis mechanism from squark decays at LHC  

NASA Astrophysics Data System (ADS)

We investigate the feasibility of directly detecting a generation mechanism of the cosmic baryon asymmetry by repeating the same particle physics process inside the LHC. We propose a framework with R-parity and CP violating squark decays responsible for baryogenesis, which can be embedded in supersymmetric models and is partly motivated by naturalness. We argue that the baryon number generation here is closely related to lepton charge asymmetry on the resonance. We emphasize the importance of the single charged lepton plus multijet channel in the absence of significant missing energy in search of such a scenario.

An, Haipeng; Zhang, Yue

2014-04-01

342

Direct/indirect detection signatures of nonthermally produced dark matter  

SciTech Connect

We study direct and indirect detection possibilities of neutralino dark matter produced nonthermally by, e.g., the decay of long-lived particles, as is easily implemented in the case of anomaly or mirage-mediation models. In this scenario, large self-annihilation cross sections are required to account for the present dark matter abundance, and it leads to significant enhancement of the gamma-ray signature from the galactic center and the positron flux from the dark matter annihilation. It is found that GLAST and PAMELA will find the signal or give tight constraints on such nonthermal production scenarios of neutralino dark matter.

Nagai, Minoru [Theory Group, KEK, Oho 1-1, Tsukuba, Ibaraki 305-0801 (Japan); Nakayama, Kazunori [Institute for Cosmic Ray Research, University of Tokyo, Kashiwa, Chiba 277-8582 (Japan)

2008-09-15

343

A new colorimetric method for determining the isomerization activity of sucrose isomerase.  

PubMed

A new colorimetric method for determining the isomerization activity of sucrose isomerase was developed. This colorimetric method is based on the enzymatic reactions of invertase and glucose oxidase-peroxidase (GOD-POD). The main scheme for assaying sucrose isomerase activity is to degrade sucrose in the reaction mixture to glucose and fructose by invertase and to detect the concentration of glucose generated using GOD-POD. The concentrations of trehalulose and isomaltulose, reaction products of sucrose isomerase, are calculated from the concentration of glucose. This method allows rapid and accurate determination of the isomerization activity of sucrose isomerase without inhibition by hydrolysis activity. PMID:17284828

Park, Sang-Eun; Cho, Mee-Hyun; Lim, Jin Kyu; Kim, Jong-Sang; Kim, Jeong Hwan; Kwon, Dae Young; Park, Cheon-Seok

2007-02-01

344

Passive, Direct-Read Monitoring System for Selective Detection and Quantification of Hydrogen Chloride  

NASA Technical Reports Server (NTRS)

Monitoring the exposure of an employee to hydrogen chloride or hydrochloric acid in the presence of other acids has been a challenge to the industrial hygiene community. The capability of a device to differentiate the levels of acid vapors would allow for more accurate determinations of exposure and therefore improved occupational health. In this work, a selective direct-read colorimetric badge system was validated for Short Term Exposure Limit (STEL) monitoring of hydrogen chloride. The passive colorimetric badge system consists of a direct reading badge and a color scale. The badge has a coated indicator layer with a diffusive resistance in the shape of an exclamation mark. An exclamation mark will appear if hydrogen chloride is present in the atmosphere at concentrations at or above 2.0 ppm. By using the color scale, the intensity of the color formed on the badge can be further quantified up to 25 ppm. The system was validated according to a protocol based on the NIOSH Protocol for the Evaluation of Passive Monitors. The badge was exposed to relative humidities ranging from 11% to 92%, temperatures ranging from 7 C to 400 C and air velocities ranging from 5 cm/sec to 170 cm/sec. All experiments were conducted in a laboratory vapor generation system. Hydrofluoric acid, nitric acid, sulfuric acid, chlorine, hydrogen sulfide and organic acids showed no effect on the performance of the hydrogen chloride monitoring system. The passive badge and color scale system exceeded the accuracy requirements as defined by NIOSH. At ambient conditions, the mean coefficient of variation was 10.86 and the mean bias was 1.3%. This data was presented previously at the American Industrial Hygiene Conference and Exposition in Toronto, Canada in June 1999.

Chapman, K. B.; Mihaylov, G. M.; Kirollos, K. S.

2000-01-01

345

Assessing Alternatives for Directional Detection of a WIMP Halo  

E-print Network

The future of direct terrestrial WIMP detection lies on two fronts: new, much larger low background detectors sensitive to energy deposition, and detectors with directional sensitivity. The former can large range of WIMP parameter space using well tested technology while the latter may be necessary if one is to disentangle particle physics parameters from astrophysical halo parameters. Because directional detectors will be quite difficult to construct it is worthwhile exploring in advance generally which experimental features will yield the greatest benefits at the lowest costs. We examine the sensitivity of directional detectors with varying angular tracking resolution with and without the ability to distinguish forward versus backward recoils, and compare these to the sensitivity of a detector where the track is projected onto a two-dimensional plane. The latter detector regardless of where it is placed on the Earth, can be oriented to produce a significantly better discrimination signal than a 3D detector without this capability, and with sensitivity within a factor of 2 of a full 3D tracking detector. Required event rates to distinguish signals from backgrounds for a simple isothermal halo range from the low teens in the best case to many thousands in the worst.

Craig J. Copi; Lawrence M. Krauss; David Simmons-Duffin; Steven R. Stroiney

2005-08-30

346

Diagnosis of lung cancer by the analysis of exhaled breath with a colorimetric sensor array  

Microsoft Academic Search

Background: The pattern of volatile organic compounds (VOCs) in the exhaled breath of patients with lung cancer may be unique. New sensor systems that detect patterns of VOCs have been developed. One of these sensor systems, a colorimetric sensor array, has 36 spots composed of different chemically sensitive compounds impregnated on a disposable cartridge. The colours of these spots change

Peter J Mazzone; Jeffrey Hammel; Raed Dweik; Jie Na; Carmen Czich; Daniel Laskowski; Tarek Mekhail

2007-01-01

347

A colorimetric sensor array for identification of toxic gases below permissible exposure limits†  

PubMed Central

A colorimetric sensor array has been developed for the rapid and sensitive detection of 20 toxic industrial chemicals (TICs) at their PELs (permissible exposure limits). The color changes in an array of chemically responsive nanoporous pigments provide facile identification of the TICs with an error rate below 0.7%. PMID:20221484

Feng, Liang; Musto, Christopher J.; Kemling, Jonathan W.; Lim, Sung H.; Suslick, Kenneth S.

2010-01-01

348

Colorimetric determination of o-phenylenediamine in water samples based on the formation of silver nanoparticles as a colorimetric probe.  

PubMed

A simple, rapid and cost-effective method for visual colorimetric detection of o-phenylenediamine (OPD) based on the formation of silver nanoparticles (AgNPs) has been developed in this paper. Silver ions can be reduced to AgNPs by OPD in a few minutes, causing changes in absorption spectra and color of the reaction system. Therefore, colorimetric detection of OPD could be realized by a UV-vis spectrophotometer or even the naked eye. Results showed that the absorption intensity of AgNPs at 416nm exhibited a good linear correlation (R(2)=0.998) with OPD concentration in the range from 10(-6) to 8×10(-5)molL(-1) and the detection limit (3?/S) was calculated to be 1.61×10(-7)molL(-1). Furthermore, as low as 4×10(-6)molL(-1)OPD can be visualized by the naked eye without the requirement of any complicated or expensive instruments. This proposed method has been successfully applied to determine OPD in water samples, and may provide an innovative platform in the development of sensors for guiding environmental monitoring in the future. PMID:25615678

Li, Nan; Gu, Yu; Gao, Mengmeng; Wang, Zilu; Xiao, Deli; Li, Yun; Lin, Rui; He, Hua

2015-04-01

349

Spectrum Recovery from Colorimetric Data for Color Reproductions  

E-print Network

Spectrum Recovery from Colorimetric Data for Color Reproductions Gaurav Sharma and Shen-ge Wang Xerox Corp., MS0128-27E, 800 Phillips Rd., Webster, NY 14580 ABSTRACT Colorimetric data can be readily data to colorimetric values is many-to-one and therefore typically not invertible. In this paper, we

Sharma, Gaurav

350

Development of an Intelligent Polymerized Crystalline Colloidal Array Colorimetric Reagent  

E-print Network

Development of an Intelligent Polymerized Crystalline Colloidal Array Colorimetric Reagent Chad E, University of Pittsburgh, Pittsburgh, Pennsylvania 15260 We have developed a novel colorimetric reagent angle relative to the incident light. We have developed a new colorimetric reagent for the determination

Asher, Sanford A.

351

Polynomial modeling and optimization for colorimetric characterization of scanners  

E-print Network

Polynomial modeling and optimization for colorimetric characterization of scanners Simone Bianco device, while a point in a colorimetric space, such as CIELAB space, indicates how the color is perceived-dependent space the colorimetric value of the corresponding color. The colo- rimetric characterization

Schettini, Raimondo

352

Polynomial modeling and optimization for colorimetric characterization of scanners  

E-print Network

Polynomial modeling and optimization for colorimetric characterization of scanners May 20, 2008 S present different computational strategies for colorimetric char- acterization of scanners using how a color stimulus is produced by a given device, while a point in a colorimetric space

Schettini, Raimondo

353

Notes & Tips Colorimetric determination of pure Mg2+  

E-print Network

for a colorimetric assay of pure Mg2+ -dependent phosphatidate phosphatase activ- ity. This enzyme plays a major role, and with the concentration of water-soluble dioctanoyl phosphatidate. The colorimetric assay was used to examine enzyme- active colorimetric PAP1 assay based on orthophosphate analysis using the malachite green

Chen, Kuang-Yu

354

Effect of nuclear response functions in dark matter direct detection  

NASA Astrophysics Data System (ADS)

We examine the effect of nuclear response functions, as laid out by Fitzpatrick et al. [J. Cosmol. Astropart. Phys. 02 (2013) 004], on dark matter (DM) direct detection in the context of well-motivated UV completions, including electric and magnetic dipoles, anapole, spin-orbit, and pseudoscalar-mediated DM. Together, these encompass five of the six nuclear responses extracted from the nonrelativistic effective theory of Fitzpatrick et al. [J. Cosmol. Astropart. Phys. 02 (2013) 004] (with the sixth difficult to UV complete), with two of the six combinations corresponding to standard spin-independent and spin-dependent responses. For constraints from existing direct detection experiments, we find that only the COUPP constraint, due to its heavy iodine target with large angular momentum and an unpaired spin, and its large energy range sensitivity, is substantially modified by the new responses compared to what would be inferred using the standard form factors to model the energy dependence of the response. For heavy targets such as xenon and germanium, the behavior of the new nuclear responses as recoil energy increases can be substantially different from that of the standard responses, but this has almost no impact on the constraints derived from experiments such as LUX, XENON100, and CDMS since the maximum nuclear recoil energy detected in these experiments is relatively low. We simulate mock data for 80 and 250 GeV DM candidates utilizing the new nuclear responses to highlight how they might affect a putative signal, and find the new responses are most important for highly momentum-suppressed interactions such as the magnetic dipole or pseudoscalar-mediated interaction when the target is relatively heavy (such as xenon and iodine).

Gresham, Moira I.; Zurek, Kathryn M.

2014-06-01

355

Direct and Dynamic Detection of HIV-1 in Living Cells  

PubMed Central

In basic and applied HIV research, reliable detection of viral components is crucial to monitor progression of infection. While it is routine to detect structural viral proteins in vitro for diagnostic purposes, it previously remained impossible to directly and dynamically visualize HIV in living cells without genetic modification of the virus. Here, we describe a novel fluorescent biosensor to dynamically trace HIV-1 morphogenesis in living cells. We generated a camelid single domain antibody that specifically binds the HIV-1 capsid protein (CA) at subnanomolar affinity and fused it to fluorescent proteins. The resulting fluorescent chromobody specifically recognizes the CA-harbouring HIV-1 Gag precursor protein in living cells and is applicable in various advanced light microscopy systems. Confocal live cell microscopy and super-resolution microscopy allowed detection and dynamic tracing of individual virion assemblies at the plasma membrane. The analysis of subcellular binding kinetics showed cytoplasmic antigen recognition and incorporation into virion assembly sites. Finally, we demonstrate the use of this new reporter in automated image analysis, providing a robust tool for cell-based HIV research. PMID:23209635

Helma, Jonas; Schmidthals, Katrin; Lux, Vanda; Nüske, Stefan; Scholz, Armin M.; Kräusslich, Hans-Georg; Rothbauer, Ulrich; Leonhardt, Heinrich

2012-01-01

356

Monthly Modulation in Dark Matter Direct-Detection Experiments  

E-print Network

The count rate in dark matter direct-detection experiments should exhibit modulation signatures due to the Earth's motion with respect to the Galactic dark matter halo. The annual and daily modulations, due to the Earth's revolution about the Sun and rotation about its own axis, have been explored previously. Monthly modulation is another such feature present in rate counts, and provides a nearly model-independent method of distinguishing dark matter signal events from background. We study here monthly modulations in detail, examining both the effect of the motion of the Earth about the Earth-Moon barycenter and the gravitational focusing due to the Moon. We show that the former is the dominant source of monthly modulation, and that the amplitude of the monthly modulation varies on an annual cycle. The expected amplitude of monthly modulation is quite small which makes its detection challenging; any such detection however, would provide very strong evidence that candidate events are due to dark matter scattering.

Vivian Britto; Joel Meyers

2014-09-09

357

Detecting Tsunami Genesis and Scales Directly from Coastal GPS Stations  

NASA Astrophysics Data System (ADS)

Different from the conventional approach to tsunami warnings that rely on earthquake magnitude estimates, we have found that coastal GPS stations are able to detect continental slope displacements of faulting due to big earthquakes, and that the detected seafloor displacements are able to determine tsunami source energy and scales instantaneously. This method has successfully replicated several historical tsunamis caused by the 2004 Sumatra earthquake, the 2005 Nias earthquake, the 2010 Chilean earthquake, and the 2011 Tohoku-Oki earthquake, respectively, and has been compared favorably with the conventional seismic solutions that usually take hours or days to get through inverting seismographs (reference listed). Because many coastal GPS stations are already in operation for measuring ground motions in real time as often as once every few seconds, this study suggests a practical way of identifying tsunamigenic earthquakes for early warnings and reducing false alarms. Reference Song, Y. T., 2007: Detecting tsunami genesis and scales directly from coastal GPS stations, Geophys. Res. Lett., 34, L19602, doi:10.1029/2007GL031681. Song, Y. T., L.-L. Fu, V. Zlotnicki, C. Ji, V. Hjorleifsdottir, C.K. Shum, and Y. Yi, 2008: The role of horizontal impulses of the faulting continental slope in generating the 26 December 2004 Tsunami, Ocean Modelling, doi:10.1016/j.ocemod.2007.10.007. Song, Y. T. and S.C. Han, 2011: Satellite observations defying the long-held tsunami genesis theory, D.L. Tang (ed.), Remote Sensing of the Changing Oceans, DOI 10.1007/978-3-642-16541-2, Springer-Verlag Berlin Heidelberg. Song, Y. T., I. Fukumori, C. K. Shum, and Y. Yi, 2012: Merging tsunamis of the 2011 Tohoku-Oki earthquake detected over the open ocean, Geophys. Res. Lett., doi:10.1029/2011GL050767 (Nature Highlights, March 8, 2012).

Song, Y. Tony

2013-04-01

358

Sensitiveness of the colorimetric estimation of titanium  

USGS Publications Warehouse

The accuracy of the colorimetric estimation of titanium is practically constant over concentrations ranging from the strongest down to those containing about 1.5 mg. TiO2 in 100 cc. The change in concentration required to produce a perceptible difference in intensity between two solutions, at favorable concentrations, was found to be about 6.5 per cent, which does not differ much from the results of others with chromium and copper solutions. With suitable precautions, such as comparing by substitution and taking the mean of several settings or of the two perceptibly different extremes, the accuracy of the colorimetric comparisons appears to be about 2 per cent.

Wells, R.C.

1911-01-01

359

Detections and confirmations of electromagnetic pulses directly excited by earthquakes  

NASA Astrophysics Data System (ADS)

In order to detect and confirm electromagnetic (EM) pulses directly excited by earthquakes, we have been observing EM noise in boreholes of 100 m in depth at various places such as on mountain sides and seashores, inserting EM sensor systems into the boreholes. In the observations, we detected tremendous number of EM pulses of a few kHz with duration of a few millisecond. From detailed analysis of these EM pulses, we found that almost all of these EM pulses were lightning and artificial ones, and we could not confirm any earthquake-related EM pulse at all. The reason why earthquake-related EM pulses could not be detected in the earth was considered that the amplitude of the EM pulses would be strongly decayed during their propagations in the earth due to high electrical conductivity of the earth's medium. The decay rate is generally given by a specific distance so-called 'Skin depth ' through which the amplitude decays to 1/e (e = 2.718), and the skin depth is inversely proportional to square root of EM frequency. This means that high frequency EM waves decay and fade out in a short distance but lower frequency ones can survive for a long distance. Therefore EM waves of a few kHz had been severe to propagate for long distance in the earth. So we shifted down the monitoring frequency to the range of a few tens of Hz. As the result, we have finally detected earthquake-excited EM pulses in the earth and above the ground. By simultaneous capturing of waveforms of detected EM pulses and of seismic accelerations measured at the same observation site, we have confirmed close relationship between earthquakes and EM pulses, in which the waveform of magnetic component clearly shows primary tremor corresponding to seismic P-wave although it can't be seen in the waveform of seismic acceleration. Furthermore, by a laboratory experiment on giving stress impact to a granite pillar, excitation mechanism of EM pulses from granite has been confirmed as the Piezo-electric effect. These results have proved that seismic P-wave could be easily generated even by extremely weak stress impact to earth's crusts compared to that for causing earthquakes, and that EM waves could be excited by small seismic vibrations. Furthermore, we found an analogy of situations in EM pulse excitations between in the laboratory experiment and in active faults, which means that EM pulses can be excited by the fractures of small stones in active faults before earthquakes. So we here propose a method for detecting EM pulses as a precursor of earthquakes.

Tsutsui, M.

2013-12-01

360

Tropospheric Wind Profile Measurements with a Direct Detection Doppler Lidar  

NASA Technical Reports Server (NTRS)

Research has established the importance of global tropospheric wind measurements for large scale improvements in numerical weather prediction. In addition, global wind measurements provide data that are fundamental to the understanding and prediction of global climate change. These tasks are closely linked with the goals of the NASA Earth Science Enterprise and Global Climate Change programs. NASA Goddard has been actively involved in the development of direct detection Doppler lidar methods and technologies to meet the wind observing needs of the atmospheric science community. In this paper we describe a recently developed prototype wind lidar system using a direct detection Doppler technique for measuring wind profiles from the surface through the troposphere. This system uses a pulsed ND:YAG laser operating at 1064 nm as the transmitter. The laser pulse is directed to the atmosphere using a 40 cm diameter scan mirror. The portion of the laser energy backscattered from aerosols and molecules is collected by a 40 cm diameter telescope and coupled via fiber optics into the Doppler receiver. Single photon counting APD's are used to detect the atmospheric backscattered signal. The principle element of the receiver is a dual bandpass tunable Fabry Perot etalon which analyzes the Doppler shift of the incoming laser signal using the double edge technique. The double edge technique uses two high resolution optical filters having bandpasses offset relative to one another such that the 'edge' of the first filter's transmission function crosses that of the second at the half power point. The outgoing laser frequency is located approximately at the crossover point. Due to the opposite going slopes of the edges, a Doppler shift in the atmospheric backscattered laser frequency produces a positive change in signal for one filter and a negative change in the second filter. Taking the ratio of the two edge channel signals yields a result which is directly proportional to the component of the wind along the line-of-sight of the laser. Measuring the radial wind in several directions provides sufficient information to determine the true wind speed and direction. The lidar has operated from our laboratory at Goddard since June, 1997. Wind profiles have been obtained to altitudes of 12 km with a vertical resolution of 330 in. Vector wind data are obtained by rotating the scan mirror to measure line-of-sight wind profiles for at least two azimuth angles at an elevation angle of 45 degrees. The precision of the data as determined from the standard deviation of multiple independent lidar profiles is in the range of 1 to 3 m/sec up to 10 km. Good agreement is obtained when the lidar data are compared with the upper air rawinsonde soundings taken at Dulles airport. Examples of the wind lidar data will be presented along with a description of the instrument and future developments.

Gentry, Bruce M.; Li, Steven X.; Korb, C. Laurence; Chen, Huailin; Mathur, Savyasachee

1998-01-01

361

Paper-based tuberculosis diagnostic devices with colorimetric gold nanoparticles  

NASA Astrophysics Data System (ADS)

A colorimetric sensing strategy employing gold nanoparticles and a paper assay platform has been developed for tuberculosis diagnosis. Unmodified gold nanoparticles and single-stranded detection oligonucleotides are used to achieve rapid diagnosis without complicated and time-consuming thiolated or other surface-modified probe preparation processes. To eliminate the use of sophisticated equipment for data analysis, the color variance for multiple detection results was simultaneously collected and concentrated on cellulose paper with the data readout transmitted for cloud computing via a smartphone. The results show that the 2.6 nM tuberculosis mycobacterium target sequences extracted from patients can easily be detected, and the turnaround time after the human DNA is extracted from clinical samples was approximately 1 h.

Tsai, Tsung-Ting; Shen, Shu-Wei; Cheng, Chao-Min; Chen, Chien-Fu

2013-08-01

362

Halo independent comparison of direct dark matter detection data  

NASA Astrophysics Data System (ADS)

We extend the halo-independent method of Fox, Liu, and Weiner to include energy resolution and efficiency with arbitrary energy dependence, making it more suitable for experiments to use in presenting their results. Then we compare measurements and upper limits on the direct detection of low mass ( ~ 10 GeV) weakly interacting massive particles with spin-independent interactions, including the upper limit on the annual modulation amplitude from the CDMS collaboration. We find that isospin-symmetric couplings are severely constrained both by XENON100 and CDMS bounds, and that isospin-violating couplings are still possible at the lowest energies, while the tension of the higher energy CoGeNT bins with the CDMS modulation constraint remains. We find the CRESST-II signal is not compatible with the modulation signals of DAMA and CoGeNT.

Gondolo, Paolo; Gelmini, Graciela B.

2012-12-01

363

Halo independent comparison of direct dark matter detection data  

E-print Network

We extend the halo-independent method of Fox, Liu, and Weiner to include energy resolution and efficiency with arbitrary energy dependence, making it more suitable for experiments to use in presenting their results. Then we compare measurements and upper limits on the direct detection of low mass ($\\sim10$ GeV) weakly interacting massive particles with spin-independent interactions, including the upper limit on the annual modulation amplitude from the CDMS collaboration. We find that isospin-symmetric couplings are severely constrained both by XENON100 and CDMS bounds, and that isospin-violating couplings are still possible at the lowest energies, while the tension of the higher energy CoGeNT bins with the CDMS modulation constraint remains. We find the CRESST II signal is not compatible with the modulation signals of DAMA and CoGeNT.

Paolo Gondolo; Graciela B. Gelmini

2012-09-07

364

Halo independent comparison of direct dark matter detection data  

SciTech Connect

We extend the halo-independent method of Fox, Liu, and Weiner to include energy resolution and efficiency with arbitrary energy dependence, making it more suitable for experiments to use in presenting their results. Then we compare measurements and upper limits on the direct detection of low mass ( ? 10 GeV) weakly interacting massive particles with spin-independent interactions, including the upper limit on the annual modulation amplitude from the CDMS collaboration. We find that isospin-symmetric couplings are severely constrained both by XENON100 and CDMS bounds, and that isospin-violating couplings are still possible at the lowest energies, while the tension of the higher energy CoGeNT bins with the CDMS modulation constraint remains. We find the CRESST-II signal is not compatible with the modulation signals of DAMA and CoGeNT.

Gondolo, Paolo [Department of Physics and Astronomy, University of Utah, 115 South 1400 East 201, Salt Lake City, UT 84112 (United States); Gelmini, Graciela B., E-mail: paolo@physics.utah.edu, E-mail: gelmini@physics.ucla.edu [Department of Physics and Astronomy, UCLA, 475 Portola Plaza, Los Angeles, CA 90095 (United States)

2012-12-01

365

Sensitivity enhancement for colorimetric glucose assays on whole blood by on-chip beam-guidance.  

PubMed

In this paper, we present a novel concept for optical beam-guidance to significantly enhance the sensitivity of colorimetric assays by extending the optical path length through the detection cell which linearly impacts the resulting attenuation of a probe beam according to the law of Beer-Lambert. In our setup, the incident probe beam is deflected by 90( composite function) into the chip plane at monolithically integrated V-grooves to pass a flat detection cell at its full width (i.e., with a path length of 10 mm) instead of its usually much smaller height. Afterwards, the attenuated beam is redirected by another V-groove towards an external detector. The general beam-guidance concept is demonstrated by a glucose assay on human whole blood on a centrifugal microfluidic "lab-on-a-disk" platform made of COC. We achieve an excellent linearity with a correlation coefficient (R (2)) of 0.997 paired with a lower limit of detection (200 microM) and a good reproducibility with a coefficient of variation (CV) of 4.0% over nearly three orders of magnitude. With an accelerated sedimentation of cellular constituents by centrifugal forces, the sample of whole blood can be analyzed in a fully integrated fashion within 210 s. This time-to-result can even be improved by the numerical extrapolation of the saturation value. Additionally, the direct assay on whole blood also shows a negligible correlation with the hematocrit of the blood sample. PMID:16732473

Grumann, M; Steigert, J; Riegger, L; Moser, I; Enderle, B; Riebeseel, K; Urban, G; Zengerle, R; Ducrée, J

2006-09-01

366

Subcarrier multiplexing with dispersion reduction and direct detection  

DOEpatents

An SCM system for simultaneously reducing the concomitant problems of receiver complexity and dispersion penalty and without requiring the use of an expensive, high-bandwidth optical detector. The system provides both a dispersion reduction and a direct detection to the receiver, with microwave mixers and lithium niobate external modulators that produce sidebands that are only separated by a few gigahertz from a principal laser optical carrier. Digital data streams are independently impressed upon these sidebands for transmission over an ordinary single-mode fiber. Independent high-speed data streams are upconverted to microwave frequencies. These subcarriers are then combined with a microwave power combiner and amplified with a microwave amplifier. A solid-state 1550-nm laser carrier is modulated by the microwave subcarriers. An erbium-doped fiber amplifier (EDFA) is used just prior to long-distance transmission over ordinary single-mode fiber. The transmitted optical signal may then traverse multiple EDFAs to compensate for long-haul optical fiber losses prior to detection. At a receiving end, the optical signal is split into multiple paths. The subcarrier channels are optically pre-selected using a narrowband optical filter, such as a fiber Fabry-Perot (FFP) filter. An optical detector converts the selected optical signal into a baseband electrical data stream.

Sargis, Paul D. (Modesto, CA); Haigh, Ronald E. (Tracy, CA); McCammon, Kent G. (Livermore, CA)

1997-01-01

367

Subcarrier multiplexing with dispersion reduction and direct detection  

DOEpatents

An SCM system is disclosed for simultaneously reducing the concomitant problems of receiver complexity and dispersion penalty and without requiring the use of an expensive, high-bandwidth optical detector. The system provides both a dispersion reduction and a direct detection to the receiver, with microwave mixers and lithium niobate external modulators that produce sidebands that are only separated by a few gigahertz from a principal laser optical carrier. Digital data streams are independently impressed upon these sidebands for transmission over an ordinary single-mode fiber. Independent high-speed data streams are upconverted to microwave frequencies. These subcarriers are then combined with a microwave power combiner and amplified with a microwave amplifier. A solid-state 1550-nm laser carrier is modulated by the microwave subcarriers. An erbium-doped fiber amplifier (EDFA) is used just prior to long-distance transmission over ordinary single-mode fiber. The transmitted optical signal may then traverse multiple EDFAs to compensate for long-haul optical fiber losses prior to detection. At a receiving end, the optical signal is split into multiple paths. The subcarrier channels are optically pre-selected using a narrowband optical filter, such as a fiber Fabry-Perot (FFP) filter. An optical detector converts the selected optical signal into a baseband electrical data stream. 2 figs.

Sargis, P.D.; Haigh, R.E.; McCammon, K.G.

1997-01-21

368

Direct Detection of Bacterial Protein Secretion Using Whole Colony Proteomics*  

PubMed Central

Bacteria use a variety of secretion systems to transport proteins beyond their cell membrane to interact with their environment. For bacterial pathogens, these systems are key virulence determinants that transport bacterial proteins into host cells. Genetic screens to identify bacterial genes required for export have relied on enzymatic or fluorescent reporters fused to known substrates to monitor secretion. However, they cannot be used in analysis of all secretion systems, limiting the implementation across bacteria. Here, we introduce the first application of a modified form of whole colony MALDI-TOF MS to directly detect protein secretion from intact bacterial colonies. We show that this method is able to specifically monitor the ESX-1 system protein secretion system, a major virulence determinant in both mycobacterial and Gram-positive pathogens that is refractory to reporter analysis. We validate the use of this technology as a high throughput screening tool by identifying an ESAT-6 system 1-deficient mutant from a Mycobacterium marinum transposon insertion library. Furthermore, we also demonstrate detection of secreted proteins of the prevalent type III secretion system from the Gram-negative pathogen, Pseudomonas aeruginosa. This method will be broadly applicable to study other bacterial protein export systems and for the identification of compounds that inhibit bacterial protein secretion. PMID:22580590

Champion, Matthew M.; Williams, Emily A.; Kennedy, George M.; DiGiuseppe Champion, Patricia A.

2012-01-01

369

DIRECT DETECTIONS OF YOUNG STARS IN NEARBY ELLIPTICAL GALAXIES  

SciTech Connect

Small amounts of star formation in elliptical galaxies are suggested by several results: surprisingly young ages from optical line indices, cooling X-ray gas, and mid-infrared dust emission. Such star formation has previously been difficult to directly detect, but using ultraviolet Hubble Space Telescope Wide Field Camera 3 imaging, we have identified individual young stars and star clusters in four nearby ellipticals. Ongoing star formation is detected in all galaxies, including three ellipticals that have previously exhibited potential signposts of star-forming conditions (NGC 4636, NGC 4697, and NGC 4374), as well as the typical ''red and dead'' NGC 3379. The current star formation in our closest targets, where we are most complete, is between 2.0 and 9.8 Multiplication-Sign 10{sup -5} M{sub Sun} yr{sup -1}. The star formation history was roughly constant from 0.5 to 1.5 Gyr (at (3-5) Multiplication-Sign 10{sup -4} M{sub Sun} yr{sup -1}), but decreased by a factor of several in the past 0.3 Gyr. Most star clusters have a mass between 10{sup 2} and 10{sup 4} M{sub Sun }. The specific star formation rates of {approx}10{sup -16} yr{sup -1} (at the present day) or {approx}10{sup -14} yr{sup -1} (when averaging over the past Gyr) imply that a fraction 10{sup -8} of the stellar mass is younger than 100 Myr and 10{sup -5} is younger than 1 Gyr, quantifying the level of frosting of recent star formation over the otherwise passive stellar population. There is no obvious correlation between either the presence or spatial distribution of postulated star formation indicators and the star formation we detect.

Ford, H. Alyson; Bregman, Joel N., E-mail: aford@nrao.edu [Department of Astronomy, University of Michigan, Ann Arbor, MI 48109 (United States)

2013-06-20

370

Filtered Back Projection Type Direct Edge Detection of Real Synthetic Aperture Radar Images  

E-print Network

Filtered Back Projection Type Direct Edge Detection of Real Synthetic Aperture Radar Images Noe American, Edinburg, TX 78539 USA ABSTRACT Edge detection algorithms applied to Synthetic Aperture Radar with significant results. Keywords: Synthetic Aperture Radar, Backprojection, Edge Detection, Imaging 1

Qiao, Zhijun "George" - Department of Mathematics, University of Texas

371

Direct Detection of Polarized, Scattered Light from Exoplanets  

NASA Astrophysics Data System (ADS)

We propose to radically advance the state of exoplanet characterization, which lags dramatically behind exoplanet discovery. We propose to directly detect scattered light from the atmospheres of close-in, highly eccentric, and extended/non-spherical exoplanets and thereby determine the following: orbital inclination (and therefore masses free of the M sin i mass ambiguity), geometric albedo, presence or lack of hazes and cloud layers, and scattering particle size and composition. Such measurements are crucial to the understanding of exoplanet atmospheres, because observations with NASA s Hubble, Spitzer, and Kepler space telescopes present the following questions: 1) Do exoplanets have highly reflective haze layers? 2) How does the upper atmospheric composition differ between exoplanets with and without thermal inversions? 3) What are the optical manifestations of the extreme heating of highly eccentric exoplanets? 4) Are the atmospheres of certain exoplanets truly escaping their Roche lobes? Using the POLISH2 polarimeter developed by the Postdoctoral Associate (Wiktorowicz) for the Lick 3-m telescope, we propose to monitor the linear polarization state of exoplanet host stars at the part per million level. POLISH2 consistently delivers nearly photon shot noise limited measurements with this precision. In addition, the simultaneous full-Stokes measurements of POLISH2 and the equatorial mount of the Lick 3-m telescope ensure that systematic effects are mitigated to the part per million level. Indeed, we find the accuracy of the POLISH2 polarimeter to be 0.1 parts per million. This instrument and telescope represent the highest precision polarimeter in the world for exoplanet research. We present potential detection of polarized, scattered light from the HD 189733b, Tau Boo b, and WASP-12b exoplanets. We propose to observe hot Jupiters on circular orbits, highly eccentric exoplanets, exoplanets with extended or non-spherical scattering surfaces, and 55 Cnc e, the super-Earth with the highest expected polarimetric signal-to- noise ratio. These exoplanets should all produce detectable polarization, and they present unique opportunities to study the atmospheres of wildly different exoplanets. Extending the PI s (Laughlin) Monte Carlo ray-tracing code, and utilizing the Co-I s (Fortney) experience in modeling exoplanet atmospheres, we propose to fund a graduate student to model the polarization data obtained from POLISH2 and invert the above variables. This is because they affect the amplitude and shape of the periodic variability in the polarization state of light from the system. Indeed, the discovery of spherical, sulfuric acid droplets suspended in the Venusian atmosphere was made forty years ago with Mie scattering models to fit polarimetric measurements. The PI s ray-tracing code, which has been used to model the rapid heating of the eccentric HD 80606b exoplanet, currently includes Rayleigh scattering and alkali metal absorption in a self-consistent manner. The direct detection of exoplanets as well as characterization of their atmospheric compositions and structure is directly related to the goals of the Origins program and to the NASA 2010 Science Plan, which emphasizes exploration of exoplanets and exoplanetary systems.

Laughlin, Gregory

372

Colorimetric Titration Experiment for the Undergraduate Laboratory.  

ERIC Educational Resources Information Center

Describes a colorimetric titration instrument usable in the undergraduate laboratory that fulfills the objectives of ruggedness, freedom from ambient light interference, and low cost. Although accessories can be added (raising the price), the basic instrument is low priced and can be used manually with a simple voltmeter. (JN)

Lopez, Edwin; Vassos, Basil H.

1984-01-01

373

Visualizing Capsaicinoids: Colorimetric Analysis of Chili Peppers  

ERIC Educational Resources Information Center

A colorimetric method for total capsaicinoids in chili pepper ("Capsicum") fruit is described. The placental material of the pepper, containing 90% of the capsaicinoids, was physically separated from the colored materials in the pericarp and extracted twice with methanol, capturing 85% of the remaining capsaicinoids. The extract, evaporated and…

Thompson, Robert Q.; Chu, Christopher; Gent, Robin; Gould, Alexandra P.; Rios, Laura; Vertigan, Theresa M.

2012-01-01

374

Colorimetric fluorescent cyanide chemodosimeter based on triphenylimidazole derivative.  

PubMed

In this paper, we demonstrated a highly selective colorimetric chemodosimeter for cyanide anion detection. This chemodosimeter having a triphenylimidazole group as a fluorescent signal unit and a dicyano-vinyl group as a reaction unit was synthesized by the Knoevenagel condensation of 4-(4,5-diphenyl-1H-imidazol-2-yl)benzaldehyde with malononitrile in a reasonable yield. The probe exhibited an intramolecular charge transfer (ICT) absorption band at 420 nm and emission band at 620 nm, respectively. Upon the addition of cyanide anion, the probe displayed a blue-shifted spectrum and loss in color due to the disruption of conjugation. With the aid of the fluorescence spectrometer, the chemodosimeter exhibited a detection limit of 0.11 ?M (S/N=3). Interferences from other common anions associated with cyanide anion analysis were effectively inhibited. PMID:24463246

Zheng, Wei; He, Xiangzhu; Chen, Hongbiao; Gao, Yong; Li, Huaming

2014-04-24

375

NEW COMPLETENESS METHODS FOR ESTIMATING EXOPLANET DISCOVERIES BY DIRECT DETECTION  

SciTech Connect

We report on new methods for evaluating realistic observing programs that search stars for planets by direct imaging, where observations are selected from an optimized star list and stars can be observed multiple times. We show how these methods bring critical insight into the design of the mission and its instruments. These methods provide an estimate of the outcome of the observing program: the probability distribution of discoveries (detection and/or characterization) and an estimate of the occurrence rate of planets ({eta}). We show that these parameters can be accurately estimated from a single mission simulation, without the need for a complete Monte Carlo mission simulation, and we prove the accuracy of this new approach. Our methods provide tools to define a mission for a particular science goal; for example, a mission can be defined by the expected number of discoveries and its confidence level. We detail how an optimized star list can be built and how successive observations can be selected. Our approach also provides other critical mission attributes, such as the number of stars expected to be searched and the probability of zero discoveries. Because these attributes depend strongly on the mission scale (telescope diameter, observing capabilities and constraints, mission lifetime, etc.), our methods are directly applicable to the design of such future missions and provide guidance to the mission and instrument design based on scientific performance. We illustrate our new methods with practical calculations and exploratory design reference missions for the James Webb Space Telescope (JWST) operating with a distant starshade to reduce scattered and diffracted starlight on the focal plane. We estimate that five habitable Earth-mass planets would be discovered and characterized with spectroscopy, with a probability of zero discoveries of 0.004, assuming a small fraction of JWST observing time (7%), {eta} = 0.3, and 70 observing visits, limited by starshade fuel.

Brown, Robert A.; Soummer, Remi [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

2010-05-20

376

Direct Detection Rates of Dark Matter Coupled to Dark Energy  

E-print Network

We investigate the effect of a coupling between dark matter and dark energy on the rates for the direct detection of dark matter. The magnitude of the effect depends on the strength $\\kappa$ of this new interaction relative to gravity. The resulting isothermal velocity distribution for dark matter in galaxy halos is still Maxwell-Boltzmann (M-B), but the characteristic velocity and the escape velocity are increased by $\\sqrt{1+\\kappa^2}$. We adopt a phenomenological approach and consider values of $\\kappa$ near unity. For such values we find that: (i) The (time averaged) event rate increases for light WIMPs, while it is somewhat reduced for WIMP masses larger than 100 GeV. (ii) The time dependence of the rate arising from the modulation amplitude is decreased compared to the standard M-B velocity distribution. (iii) The average and maximum WIMP energy increase proportionally to $1+\\kappa^2$, which, for sufficiently massive WIMPs, allows the possibility of designing experiments measuring $\\gamma$ rays following nuclear de-excitation.

N. Tetradis; J. D. Vergados; Amand Faessler

2006-09-07

377

Investigation of possible dark matter direct detection in electron accelerators  

NASA Astrophysics Data System (ADS)

We investigate a possibility of neutralino dark matter (DM) direct detection in the future electron accelerators. That is counting of high pT electron recoil events by neutralinos in halo. If selectron and neutralino masses would be precisely measured in future collider experiments, the beam energy could be tuned so that the scatterings are dominated by on-pole selectron exchange. When selectron and neutralino mass difference is smaller than O(10) GeV, the elastic cross section exceeds over micro barn. Discovery of the high pT electron events would be a firm prove of the neutralino DM component in halo. In the experiment, the electron beam energy must be tuned within O(10) MeV and the electron beam with high currents of O(100)A is required for the detectors of the total length of a few hundred meters so that the sufficient event rate is obtained. The dependence of the event rate on the DM velocity distribution in halo is also discussed. This method might be applicable to other DM candidates.

Hisano, Junji; Nagai, Minoru; Nojiri, Mihoko M.; Senami, Masato

2006-02-01

378

Direct detection of light anapole and magnetic dipole DM  

NASA Astrophysics Data System (ADS)

We present comparisons of direct detection data for ``light WIMPs'' with an anapole moment interaction (ADM) and a magnetic dipole moment interaction (MDM), both assuming the Standard Halo Model (SHM) for the dark halo of our galaxy and in a halo-independent manner. In the SHM analysis we find that a combination of the 90% CL LUX and CDMSlite limits or the new 90% CL SuperCDMS limit by itself exclude the parameter space regions allowed by DAMA, CoGeNT and CDMS-II-Si data for both ADM and MDM. In our halo-independent analysis the new LUX bound excludes the same potential signal regions as the previous XENON100 bound. Much of the remaining signal regions is now excluded by SuperCDMS, while the CDMSlite limit is much above them. The situation is of strong tension between the positive and negative search results both for ADM and MDM. We also clarify the confusion in the literature about the ADM scattering cross section.

Del Nobile, Eugenio; Gelmini, Graciela B.; Gondolo, Paolo; Huh, Ji-Haeng

2014-06-01

379

Enabling Technologies for Direct Detection Optical Phase Modulation Formats  

NASA Astrophysics Data System (ADS)

Phase modulation formats are believed to be one of the key enabling techniques for next generation high speed long haul fiber-optic communication systems due to the following main advantages: (1) with a balanced detection, a better receiver sensitivity over conventional intensity modulation formats, e.g., a ˜3-dB sensitivity improvement using differential phase shift keying (DPSK) and a ˜1.3-dB sensitivity improvement using differential quadrature phase shift keying (DQPSK); (2) excellent robustness against fiber nonlinearities; (3) high spectrum efficiency when using multilevel phase modulation formats, such as DQPSK. As the information is encoded in the phase of the optical field, the phase modulation formats are sensitive to the phase-related impairments and the deterioration induced in the phase-intensity conversion. This consequently creates new challenging issues. The research objective of this thesis is to depict some of the challenging issues and provide possible solutions. The first challenge is the cross-phase modulation (XPM) penalty for the phase modulated channels co-propagating with the intensity modulated channels. The penalty comes from the pattern dependent intensity fluctuations of the neighboring intensity modulated channels being converted into phase noise in the phase modulation channels. We propose a model to theoretically analyze the XPM penalty dependence on the walk off effect. From this model, we suggest that using fibers with large local dispersion or intentionally introducing some residual dispersion per span would help mitigate the XPM penalty. The second challenge is the polarization dependent frequency shift (PDf) induced penalty during the phase-intensity conversion. The direct detection DPSK is usually demodulated in a Mach-Zehnder delay interferometer (DI). The polarization dependence of DI introduces a PDf causing a frequency offset between the laser's frequency and the transmissivity peak of DI, degrading the demodulated DPSK signal. We found that PDf ratio, defined as PDf/FSR, plays a predominant role in determining the performance of the demodulator. We further investigate on the PDf induced penalty for a 40-GHz DPSK demodulator on a 40-Gb/s return-to-zero (RZ)-DPSK signal to study PDf incurred optical filtering effect and spectrum distortion. Degradation for the RZ signal has been found in the presence the PDf. The third challenge is fiber dispersion induced inter-symbol interference for the phase modulated signals. Traditionally the dispersion is compensated using dispersion compensation fibers (DCF). Recently emerged electronic dispersion compensation (EDC) not only avoids the attenuation that would be introduced by DCF, but also is capable of simultaneously compensating the chromatic dispersion (CD) and polarization mode dispersion (PMD). We investigate on EDC's CD and PMD compensation capabilities for the direct detection return-to-zero (NRZ)-DPSK signal. The simulation results show that around 300-ps/nm CD and 10-ps differential group delay (DGD) can be compensated by employing EDC. However, compared with the on-off keying (OOK) signal, the EDC is actually less effective with the DPSK signal. The investigation is extended to the RZ-DPSK signal and found out the decision feedback equalizer (DFE) exhibits better performance with the RZ-DPSK signal.

Xu, Xian

380

Direct detection of hyaluronidase in urine using cationic gold nanoparticles: a potential diagnostic test for bladder cancer.  

PubMed

Hyaluronidase (HAase) was reported as a urinary marker of bladder cancer. In this study, a simple colorimetric gold nanoparticle (AuNP) assay was developed for rapid and sensitive detection of urinary HAase activity. Charge interaction between polyanionic hyaluronic acid (HA) and cationic AuNPs stabilized with cetyl trimethyl ammonium bromide (CTAB) led to formation of gold aggregates and a red to blue color shift. HAase digests HA into small fragments preventing the aggregation of cationic AuNPs. The nonspecific aggregation of AuNPs in urine samples was overcome by pre-treatment of samples with the polycationic chitosan that was able to agglomerate all negatively charged interfering moieties before performing the assay. The developed AuNP assay was compared with zymography for qualitative detection of urinary HAase activity in 40 bladder carcinoma patients, 11 benign bladder lesions patients and 15 normal individuals, the assay sensitivity was 82.5% vs. 65% for zymography, while the specificity for both assays was 96.1%. The absorption ratio, A530/A620 of the reacted AuNP solution was used to quantify the HAase activity. The best cut off value was 93.5 ?U/ng protein, at which the sensitivity was 90% and the specificity was 80.8%.The developed colorimetric AuNP HAase assay is simple, inexpensive, and can aid noninvasive diagnosis of bladder cancer. PMID:24240162

Nossier, Ahmed Ibrahim; Eissa, Sanaa; Ismail, Manal Fouad; Hamdy, Mohamed Ahmed; Azzazy, Hassan Mohamed El-Said

2014-04-15

381

Highly selective colorimetric bacteria sensing based on protein-capped nanoparticles.  

PubMed

A rapid and cost-effective colorimetric sensor has been developed for the detection of bacteria (Bacillus subtilis was selected as an example). The sensor was designed to rely on lysozyme-capped AuNPs with the advantages of effective amplification and high specificity. In the sensing system, lysozyme was able to bind strongly to Bacillus subtilis, which effectively induced a color change of the solution from light purple to purplish red. The lowest concentration of Bacillus subtilis detectable by the naked eye was 4.5 × 10(3) colony-forming units (CFU) mL(-1). Similar results were discernable from UV-Vis absorption measurements. A good specificity was observed through a statistical analysis method using the SPSS software (version 17.0). This simple colorimetric sensor may therefore be a rapid and specific method for a bacterial detection assay in complex samples. PMID:25503063

Qiu, Suyan; Lin, Zhenyu; Zhou, Yaomin; Wang, Donggen; Yuan, Lijuan; Wei, Yihua; Dai, Tingcan; Luo, Linguang; Chen, Guonan

2015-02-01

382

Passive colorimetric dosimeter tubes for ammonia, carbon monoxide, carbon dioxide, hydrogen sulfide, nitrogen dioxide, and sulfur dioxide  

SciTech Connect

Colorimetric, stain length, personal dosimeters operating by gas diffusion have been developed to determine worker exposure for up to an 8-h period for several inorganic airborne contaminants in the range of their threshold limit values. Length of stain, colorimetric dosimeters have been made for the detection of ammonia (NH/sub 3/), carbon monoxide (CO), carbon dioxide (CO/sub 2/), hydrogen sulfide (H/sub 2/S), nitrogen dioxide (NO/sub 2/), and sulfur dioxide (SO/sub 2/) in air. For each gas detection system, the sampler depends on the transfer of the gas by diffusion into a glass tube containing a colorimetric length of stain indicator. The stain length developed in a given period of time is compared to a calibration chart to determine, on the spot, the average gas concentration to which the dosimeter has been exposed. These dosimeters are known by the trade name Vapor Gard.

McKee, E.S.; Pritts, I.M.

1981-08-01

383

Passive colorimetric dosimeter tubes for ammonia, carbon monoxide, carbon dioxide, hydrogen sulfide, nitrogen dioxide and sulfur dioxide  

SciTech Connect

Colorimetric, stain length, personal dosimeters operating by gas diffusion have been developed to determine worker exposure for up to an eight-hour period for several inorganic airborne contaminants in the range of their Threshold Limit Values. Length of stain, colorimetric dosimeters have been made for the detection of ammonia (NH/sub 3/), carbon monoxide (CO), carbon dioxide (CO/sub 2/), hydrogen sulfide (H/sub 2/S), nitrogen dioxide (NO/sub 2/), and sulfur dioxide (SO/sub 2/) in air. For each gas detection system, the sampler depends on the transfer of the gas by diffusion into a glass tube containing a colorimetric length of stain indicator. The stain length developed in a given period of time is compared to a calibration chart to determine, on the spot, the average gas concentration to which the dosimeter has been exposed. These dosimeters are known by the trade name Vapor Gard.

McConnaughey, P.W.; McKee, E.S.; Pritts, I.M.

1985-07-01

384

Determining Properties of WIMP Dark Matter with Direct Detection Experiments as Model Independently as Possible  

E-print Network

Determining Properties of WIMP Dark Matter with Direct Detection Experiments as Model Independently) are one of the leading candidates for Dark Matter. Currently, the most promising method to detect and their couplings on nucleons from direct Dark Matter detection experiments are essential. In this talk I

Peters, Achim

385

A system for multiplexed direct electrical detection of DNA synthesis  

Microsoft Academic Search

An electronic system for the multiplexed detection of DNA polymerization is designed and characterized. DNA polymerization is detected by the measurement of small transient currents arising from ion diffusion during polymerization. A transimpedance amplifier is used to detect these small currents; we implemented a 24 channel recording system on a single printed circuit board. Various contributions to the input-referred current

Erik P. Anderson; Jonathan S. Daniels; Heng Yu; Miloslav Karhanek; Thomas H. Lee; Ronald W. Davis; Nader Pourmand

2008-01-01

386

Absolute colorimetric characterization of a DSLR camera  

NASA Astrophysics Data System (ADS)

A simple but effective technique for absolute colorimetric camera characterization is proposed. It offers a large dynamic range requiring just a single, off-the-shelf target and a commonly available controllable light source for the characterization. The characterization task is broken down in two modules, respectively devoted to absolute luminance estimation and to colorimetric characterization matrix estimation. The characterized camera can be effectively used as a tele-colorimeter, giving an absolute estimation of the XYZ data in cd=m2. The user is only required to vary the f - number of the camera lens or the exposure time t, to better exploit the sensor dynamic range. The estimated absolute tristimulus values closely match the values measured by a professional spectro-radiometer.

Guarnera, Giuseppe Claudio; Bianco, Simone; Schettini, Raimondo

2014-03-01

387

Colorimetric analysis of Carrollton water sources  

SciTech Connect

In recent years there has been a growing concern over pollution in water supplies. In the last couple of years there have been illnesses reported that were caused by pollution in the water system in the city of Carrollton. These reports of illness led to an investigation of Hardness levels in the local water supplies. The results of the Hardness test led to the investigation of fourteen possible contaminants in the city's water supplies by Colorimetric Analysis. The results of the Colorimetric test show that chlorides are present on amounts up to 700 parts per million, and total dissolved solids are present in amounts up to 190 parts per million in the local water sources. also other contaminants such as iron, lead, copper, and low pH reading were found in these water supplies.

Spidle, D.; Kay, A. (West Georgia College, Carrollton (USA))

1990-01-01

388

Enzyme-free Detection of Hydrogen Peroxide from Cerium Oxide Nanoparticles Immobilized on Poly(4-vinylpyridine) Self-Assembled Monolayers  

SciTech Connect

A single layer of oxygen-deficient cerium oxide nanoparticles (CNPs) are immobilized on microscopic glass slide using poly(4-vinylpyridine) (PVP) self-assembled monolayers (SAMs). A specific colorimetric property of CNPs when reacted with hydrogen peroxide allows for the direct, single-step peroxide detection which can be used in medical diagnosis and explosives detection. Multiple PVP-CNP immobilized layers improve sensitivity of detection and the sensor can be regenerated for reuse.

Gaynor, James D.; Karakoti, Ajay S.; Inerbaev, Talgat; Sanghavi, Shail P.; Nachimuthu, Ponnusamy; Shutthanandan, V.; Seal, Sudipta; Thevuthasan, Suntharampillai

2013-05-02

389

Colorimetric sensor array for soft drink analysis  

Microsoft Academic Search

Fourteen commercial soft drinks have been analyzed using colorimetric\\u000a sensor arrays made from a set of 25 chemically responsive dyes printed\\u000a on a hydrophobic membrane. Digital imaging of the dye array before and\\u000a after immersion provides a color change profile as a unique fingerprint\\u000a for each specific analyte. The digital data library generated was\\u000a analyzed with statistical and chemometric methods,

Chen Zhang; Kenneth S. Suslick

2007-01-01

390

Colorimetric determination of phenols in water samples  

SciTech Connect

A colorimetric method for determination of phenols in water has been developed. The method, which is a modification of Liebermann's reaction, uses resorcinol as a chromogenic agent. The developed method is more sensitive, and the difficulties encountered in the widely used 4-aminoantipyrine method have been avoided. Application of both the proposed and 4-aminoantipyrine methods to the analysis of natural and tap water samples are presented.

Hassan, S.M.; Salem, F.B.; El-Salam, N.A.

1987-05-01

391

Aptamer-based colorimetric probe for cocaine.  

PubMed

Complex of an anti-cocaine aptamer and the dye diethylthiotricarbocyanine behaves as a colorimetric sensor with attenuation in absorbance at 760 nm for cocaine in the concentration range of 2-600 muM. Mechanistic studies indicate an intermolecular displacement of the dye as the mechanism of action of the sensor. As the dye is insoluble in buffer, cocaine binding can be followed with the unaided eye as displaced dye precipitates and supernatant decolorizes. PMID:12175205

Stojanovic, Milan N; Landry, Donald W

2002-08-21

392

Research Paper Colorimetric Polymer Films for Predicting Lipid Interactions and Percutaneous  

E-print Network

Research Paper Colorimetric Polymer Films for Predicting Lipid Interactions and Percutaneous June 3, 2008 Purpose. To develop and demonstrate a rapid and simple colorimetric film assay for evaluating lipid interactions of pharmaceutical compounds and gel formulations. Methods. The colorimetric

Jelinek, Raz

393

FUSION OF SVM-BASED MICROSCOPIC COLOR IMAGES THROUGH COLORIMETRIC TRANSFORMATION  

E-print Network

FUSION OF SVM-BASED MICROSCOPIC COLOR IMAGES THROUGH COLORIMETRIC TRANSFORMATION Christophe containing cells, the major problem lies in the spatial and the colorimetric configuration of the nuclei on pixel classification methods are firstly used through differ- ent colorimetric transformation

Lezoray, Olivier

394

Results on Discrete-Time, Decision-Directed Integrated Detection, Estimation, and Identification  

E-print Network

New results are presented for symbol-by-symbol detection with decision-directed tracking of colored channel disturbances. Recursive sampled-data algorithms are shown for Maximum A Posteriori Probability of detection under colored additive...

Painter, John H.; Jones, S.

395

Visual Motion-Detection Circuits in Flies: Parallel Direction-and Non-Direction-Sensitive Pathways between the Medulla and  

E-print Network

Visual Motion-Detection Circuits in Flies: Parallel Direction- and Non-Direction-Sensitive Pathways into parallel retinotopic pathways that subsequently are reunited at higher levels. In insects, achromatic to the lobula. Further parallel subdivisions of the retinotopic pathways to the lobula plate have been suggested

Bermingham, Eldredge

396

Three dimensional colorimetric assay assemblies  

SciTech Connect

A direct assay is described using novel three-dimensional polymeric assemblies which change from a blue to red color when exposed to an analyte, in one case a flu virus. The assemblies are typically in the form of liposomes which can be maintained in a suspension, and show great intensity in their color changes. Their method of production is also described.

Charych, D.; Reichart, A.

2000-06-27

397

Three dimensional colorimetric assay assemblies  

DOEpatents

A direct assay is described using novel three-dimensional polymeric assemblies which change from a blue to red color when exposed to an analyte, in one case a flu virus. The assemblies are typically in the form of liposomes which can be maintained in a suspension, and show great intensity in their color changes. Their method of production is also described.

Charych, Deborah (Albany, CA); Reichart, Anke (Albany, CA)

2000-01-01

398

Direct detection of intermolecular forces by atomic force microscopy  

NASA Astrophysics Data System (ADS)

The phenomenon of adhesion appears in various applications of everyday life, ranging from PostIt Notes(TM) and Scotch Tape(TM), to the assembly of aircraft and space shuttles. However, adhesion on the molecular scale is fundamentally different from the adhesion that we experience in the macroscopic world. While macroscopic objects require special adhesives or glues to bind them together, microscale and nanoscale objects and molecules commonly have a high affinity to adhere to each other. A detailed description of intermolecular forces is therefore of key importance in order to understand a wide range of phenomena, ranging from macroscopic properties of materials to molecular recognition. Two key aspects of the atomic force microscope (AFM), namely its sensitivity to sub-nanoNewton forces and its very sharp probe, offer the opportunity to measure interactions between very small numbers of molecules. Through chemical tailoring of both substrates and AFM probes with self-assembled monolayers (SAMs), measurements of forces acting between specific functional groups can be measured. Furthermore, the force required to rupture a single chemical bond can be obtained by a detailed analysis of the histograms of rupture forces. A new model was derived to examine the relationship between the various experimental variables and the shape of histograms of rupture forces when discrete chemical bonds are formed between the AFM probe and substrate. Calculations based on the model demonstrated that in measurements aimed at detecting single bond rupture forces, strict limits are put on the size of the AFM probe, the relative magnitude of the interfacial energies and the bond formation probability. These results were used in two experimental systems where the single bond rupture force was successfully measured: (i) the abstraction of a single Au-S complex from an Au coated AFM probe; and (ii) the rupture of a single charge-transfer (CT) complex between tetramethylphenylenediamine (TMPD) and tetracyanoquinodimethane (TCNQ). Measurements involving only one molecule at a time were conducted using polymer chains chemically grafted to the AFM probe and substrate. In these measurements, the effect of the solvent on the elasticity of the poly-ethylene-propylene oligomers was directly observed in the force-elongation profile.

Skulason, Hjalti

399

A real-time colorimetric and ratiometric fluorescent probe for sulfite.  

PubMed

A real-time colorimetric and ratiometric fluorescent probe based on modulating the intramolecular charge transfer (ICT) of the coumarin platform for selective detection of sulfite is presented. This reaction based probe utilized the Michael addition to the dicyano-vinyl group with the detection limit of 5.8 × 10(-5) M. The probe displayed a high selectivity for sulfite over other anions and reactive sulfur especially for biothiols including cysteine (Cys), homocysteine (Hcy) and glutathione (GSH), with about 100 nm blue shift and more than 230 times intensity ratios change of the emission spectrum. Meanwhile, it could be easily observed that the probe for sulfite changes from red to pale yellow by the naked eye, and from red to blue under UV lamp immediately after the sulfite is added. To the best of our knowledge, it is the fastest response probe for sulfite ever reported, which could give a colorimetric and ratiometric fluorescent response instantly. PMID:23563108

Wu, Ming-Yu; He, Ting; Li, Kun; Wu, Ming-Bo; Huang, Zheng; Yu, Xiao-Qi

2013-05-21

400

Detection of methicillin-resistant Staphylococcus aureus directly by loop-mediated isothermal amplification and direct cefoxitin disk diffusion tests.  

PubMed

We evaluated the utility of 2 methods for detection of methicillin-resistant Staphylococcus aureus (MRSA) directly from signal-positive blood culture bottles: loop-mediated isothermal amplification (LAMP) assay, and direct cefoxitin disk diffusion (DCDD) test using a 30 ?g cefoxitin disk. In parallel, standard microbiological identification and oxacillin susceptibility testing with MecA PCR was performed. Of 60 blood cultures positive for Gram-positive cocci in clusters, LAMP (via detection of the FemA and MecA genes) showed 100% sensitivity and specificity for identification of MRSA/MSSA. When coagulase-negative staphylococci were tested, sensitivity for detection of methicillin resistance was 91.7% and specificity was 100%. DCDD along with direct tube coagulase assay detected only 80.6% of MRSA/MSSA. LAMP showed higher diagnostic accuracy although DCDD was more cost-effective and did not require additional reagents or supplies. PMID:24952125

Metwally, L; Gomaa, N; Hassan, R

2014-04-01

401

Colorimetric determination of lead in tree leaves as indicators of atmospheric pollution  

SciTech Connect

Leaves from four species of trees were sampled at 48 different locations in Jos, Nigeria, and were analyzed for an indication of trace-metal lead using the colorimetric method. The lead levels, 7.4-28.0 ..mu..gpb/100 cm/sup 2/, detected in different areas on leaf surfaces show correlation with traffic density and leaf features. 10 references, 1 figure, 3 tables.

Fatoki, O.S.

1987-01-01

402

A 1536 Colorimetric SPAP Reporter Assay: Comparison with 96- and 384Well Formats  

Microsoft Academic Search

We report the successful miniaturization of a functional cell-based reporter gene assay. Utilizing interleukin-1beta (IL-1\\/&bgr;)-induced secreted placental alkaline phosphatase (SPAP)-catalyzed colorimetric readout, we reduced the assay volume to 10 &mgr;l using a Greiner 1536-well microplate. Our experiences of assay development, liquid handling (using a Hydra® 96; Robbins Scientific, Sunnyvale, CA), and detection (using the SpectraImage and SpectraFluor-Plus plate readers, Tecan

John C. W. Comley; Tony Reeves; Phil Robinson

1998-01-01

403

Mesoporous silica-coated gold nanorods: towards sensitive colorimetric sensing of ascorbic acid via target-induced silver overcoating  

NASA Astrophysics Data System (ADS)

This article describes a nonaggregation-based colorimetric assay of ascorbic acid by tailoring the optical properties of mesoporous silica-coated gold nanorods (MS GNRs) via silver overcoating. The colorimetric measurement of ascorbic acid (AA) concentration strongly relies on the fact that the blue shift effect of localized surface plasmon resonance (LSPR) peak of MS GNRs is gradually enlarged with the increase of AA amount. The limit of detection is determined to be 49 nM, which is comparable to that of quantum dots (QDs)-based fluorimetric methods.

Wang, Guoqing; Chen, Zhaopeng; Chen, Lingxin

2011-04-01

404

Localized surface plasmon resonance of gold nanoparticles as colorimetric probes for determination of Isoniazid in pharmacological formulation  

NASA Astrophysics Data System (ADS)

Isoniazid is an important antibiotic, which is widely used to treat tuberculosis. This study presents a colorimetric method for the determination of Isoniazid based on localized surface plasmon resonance (LSPR) property of gold nanoparticles. An LSPR band is produced by reducing gold ions in solution using Isoniazid as the reducing agent. Influences of the following relevant variables were examined and optimized in the experiment, formation time of gold nanoparticles, pH, buffer and stabilizer. These tests demonstrated that under optimum conditions the absorbance of Au nanoparticles at 530 nm related linearly to the concentration of Isoniazid in the range of 1.0-8.0 ?g mL-1 with a detection limit of 0.98 ?g mL-1. This colorimetric method has been successfully applied to the determine Isoniazid in tablets and spiked serum samples. The proposed colorimetric assay exhibits good reproducibility and accuracy, providing a simple and rapid method for analysis of Isoniazid.

Zargar, Behrooz; Hatamie, Amir

2013-04-01

405

Colorimetric and "turn-on" fluorescent determination of Cu2+ ions based on rhodamine-quinoline derivative.  

PubMed

A novel rhodamine-quinoline derivative-based indicator for Cu(2+) ion determination was designed and synthesized. It exhibited highly selective and sensitive colorimetric and "turn-on" fluorescent responses toward Cu(2+) ions based on the ring-opening mechanism of the rhodamine spirolactam in aqueous solution. The colorimetric and fluorescent responses were recorded using a domestic scanner and camera-based home-made fluorescent imaging unit, separately. The images were digitized, and the red (R), green (G), and blue (B) values were investigated. Both colorimetric and fluorescent methods showed good selectivity, and the color/fluorescence changes were remarkable for the Cu(2+) ion detection even in the presence of other metal ions. The good linear relationship was easily obtained between the color/fluorescence changes and the concentrations in the range of 20-120 ?M. PMID:23099824

Feng, Liang; Li, Hui; Lv, Yongjun; Guan, Yafeng

2012-12-21

406

Colorimetric determination of thiram based on formation of gold nanoparticles using ascorbic acid.  

PubMed

A novel optical method for the determination of thiram has been developed using surface plasmon resonance peak of gold nanoparticles (AuNPs). The stable and dispersed AuNPs were directly synthesized by reduction of HAuCl4 with ascorbic acid in micellar media according to a simple approach. The presence of thiram during formation of AuNPs results in the decrease of the intensity of plasmon resonance peak. The variation in the plasmon absorbance allows the colorimetric determination of thiram. The effect of different variables such as pH, ascorbic acid and CTAB concentrations was studied and optimized. The proposed method is capable of determining thiram over a range of 2.0×10(-7)-1.0×10(-5) mol L(-1) with a limit of detection 1.7×10(-7) mol L(-1). The relative standard deviation of the method was <3.7%. The method was successfully applied to the determination of thiram in water and plant seed samples. PMID:23597883

Rastegarzadeh, S; Abdali, Sh

2013-01-30

407

Bed Bug Detection: Current Technologies and Future Directions  

PubMed Central

Technologies to detect bed bugs have not kept pace with their global resurgence. Early detection is critical to prevent infestations from spreading. Detection based exclusively on bites is inadequate, because reactions to insect bites are non-specific and often misdiagnosed. Visual inspections are commonly used and depend on identifying live bugs, exuviae, or fecal droplets. Visual inspections are inexpensive, but they are time-consuming and unreliable when only a few bugs are present. Use of a dog to detect bed bugs is gaining in popularity, but it can be expensive, may unintentionally advertise a bed bug problem, and is not foolproof. Passive monitors mimic natural harborages; they are discreet and typically use an adhesive to trap bugs. Active monitors generate carbon dioxide, heat, a pheromone, or a combination to attract bed bugs to a trap. New technologies using DNA analysis, mass spectrometry, and electronic noses are innovative but impractical and expensive for widespread use. PMID:23553226

Vaidyanathan, Rajeev; Feldlaufer, Mark F.

2013-01-01

408

A System for Multiplexed Direct Electrical Detection of DNA Synthesis  

PubMed Central

An electronic system for the multiplexed detection of DNA polymerization is designed and characterized. DNA polymerization is detected by the measurement of small transient currents arising from ion diffusion during polymerization. A transimpedance amplifier is used to detect these small currents; we implemented a twenty-four channel recording system on a single printed circuit board. Various contributions to the input-referred current noise are analyzed and characterized, as it limits the minimum detectable current and thus the biological limit of detection. We obtained 8.5 pA RMS mean noise current (averaged over all 24 channels) over the recording bandwidth (DC to 2 kHz). With digital filtering, the input-referred current noise of the acquisition system is reduced to 2.4 pA, which is much lower than the biological noise. Electrical crosstalk between channels is measured, and a model for the crosstalk is presented. Minimizing the crosstalk is critical because it can lead to erroneous microarray data. With proper precautions, crosstalk is reduced to a negligible value (less than 1.4%). Using a micro-fabricated array of 24 gold electrodes, we demonstrated system functionality by detecting the presence of a target DNA oligonucleotide which hybridized onto its corresponding target. PMID:19183700

Anderson, Erik P.; Daniels, Jonathan S.; Yu, Heng; Karhanek, Miloslav; Lee, Thomas H.; Davis, Ronald W.; Pourmand, Nader

2008-01-01

409

Colorimetric surface plasmon resonance imaging (SPRI) biosensor array based on polarization orientation.  

PubMed

A colorimetric surface plasmon resonance (SPR) imaging biosensor array based on polarization orientation rotation is presented in this paper. It measures the spectral characteristic variations caused by the steep phase difference between the p- and s-polarization occurring at surface plasmon excitation. It provides one-order of magnitude sensor resolution improvement comparing to existing phase-sensitive SPR imaging sensors and the two-dimensional (2D) sensing capability of the imaging sensor enables multiplex, high throughput array based simultaneous detection for a range of different bio-molecular interactions. Experiments on the binding interactions detection between anti-bovine serum albumin (anti-BSA) and BSA antigen have been performed. All binding interactions occurred at 5×4 protein array were real-time monitored simultaneously. A sensor resolution of 8.26ng/ml (125pM) has been demonstrated, which is one-order of magnitude (12 times) better than the detection limit reported by existing phase-sensitive SPR imaging sensors in the literature, while no time-consuming phase modulation and phase extraction processes are required. Furthermore, the optical colorimetric image read-out of the sensor is easy to be identified by the end users comparing to conventional intensity or phase information. The colorimetric SPR imaging biosensor array can find promising potential applications in high throughput clinical disease diagnosis, protein biomarkers screening and drug screening. PMID:23644060

Wong, Chi Lok; Chen, George Chung Kit; Li, Xiaochao; Ng, Beng Koon; Shum, Ping; Chen, Peng; Lin, Zhiping; Lin, Chinlon; Olivo, Malini

2013-09-15

410

Detection of direction in scrambled motion: a simple 'life detector'?  

Microsoft Academic Search

pSpatially scrambled point-light displays of humans oranimals in locomotion contain unambiguous information about the direction in which the agent is facing. Observers are well able to retrieve this information, but only if the displays are presented right-side up. Even though spatial integrity is not required for direction discrimination the temporal relations between dots may still be important. Here, we report

N. F. Troje; C. Westhoff

2005-01-01

411

A colorimetric assay for the determination of acetyl xylan esterase or cephalosporin C acetyl esterase activities using 7-amino cephalosporanic acid, cephalosporin C, or acetylated xylan as substrate.  

PubMed

A bromothymol blue-based colorimetric assay has been devised to screen for acetyl xylan esterase or cephalosporin C (CPC) deacetylase activities using 7-amino cephalosporanic acid (7-ACA), CPC, or acetylated xylan as substrate. These enzymes are not screened with their natural substrates because of the tedious procedures available previously. Acetyl xylan esterase from Bacillus pumilus CECT 5072 was cloned, expressed in Escherichia coli Rosetta (DE3), and characterized using this assay. Similar K(M) values for 7-ACA and CPC were obtained when compared with those described using HPLC methods. The assay is easy to perform and can be carried out in robotic high-throughput colorimetric devices normally used in directed evolution experiments. The assay allowed us to detect improvements in activity at a minimum of twofold with a very low coefficient of variance in 96-well plates. This method is significantly faster and more convenient to use than are known HPLC and pH-stat procedures. PMID:17651681

Martínez-Martínez, Irene; Montoro-García, Silvia; Lozada-Ramírez, José Daniel; Sánchez-Ferrer, Alvaro; García-Carmona, Francisco

2007-10-15

412

A comparison of two colorimetric assays, based upon Lowry and Bradford techniques, to estimate total protein in soil extracts  

PubMed Central

Soil extracts usually contain large quantities of dissolved humified organic material, typically reflected by high polyphenolic content. Since polyphenols seriously confound quantification of extracted protein, minimising this interference is important to ensure measurements are representative. Although the Bradford colorimetric assay is used routinely in soil science for rapid quantification protein in soil-extracts, it has several limitations. We therefore investigated an alternative colorimetric technique based on the Lowry assay (frequently used to measure protein and humic substances as distinct pools in microbial biofilms). The accuracies of both the Bradford assay and a modified Lowry microplate method were compared in factorial combination. Protein was quantified in soil-extracts (extracted with citrate), including standard additions of model protein (BSA) and polyphenol (Sigma H1675-2). Using the Lowry microplate assay described, no interfering effects of citrate were detected even with concentrations up to 5 times greater than are typically used to extract soil protein. Moreover, the Bradford assay was found to be highly susceptible to two simultaneous and confounding artefacts: 1) the colour development due to added protein was greatly inhibited by polyphenol concentration, and 2) substantial colour development was caused directly by the polyphenol addition. In contrast, the Lowry method enabled distinction between colour development from protein and non-protein origin, providing a more accurate quantitative analysis. These results suggest that the modified-Lowry method is a more suitable measure of extract protein (defined by standard equivalents) because it is less confounded by the high polyphenolic content which is so typical of soil extracts. PMID:24302786

Redmile-Gordon, M.A.; Armenise, E.; White, R.P.; Hirsch, P.R.; Goulding, K.W.T.

2013-01-01

413

Direct detection of RDX vapor using a conjugated polymer network.  

PubMed

1,3,5-Trinitroperhydro-1,3,5-triazine (RDX) is a principal component of plastic explosives used in acts of terrorism and within improvised explosive devices, among others. Approaches to detect RDX compatible with remote, "stand-off" sampling that do not require preconcentration strategies, such as the swabs commonly employed in airports, will benefit military and civilian security. Such detection remains a significant challenge because RDX is 10(3) less volatile than 1,3,5-trinitrotoluene (TNT), corresponding to a parts-per-trillion vapor pressure under ambient conditions. Therefore, while fluorescence quenching of conjugated polymers is sufficiently sensitive to detect TNT vapors, RDX vapor detection is undemonstrated. Here we report a cross-linked phenylene vinylene polymer network whose fluorescence is quenched by trace amounts of RDX introduced from solution or the vapor phase. Fluorescence quenching is reduced, but remains significant, when partially degraded RDX is employed, suggesting that the polymer responds to RDX itself. The polymer network also responds to TNT and PETN similarly introduced from solution or the vapor phase. Pure solvents, volatile amines, and the outgassed vapors from lipstick or sunscreen do not quench polymer fluorescence. The established success of TNT sensors based on fluorescence quenching makes this a material of interest for real-world explosive sensors and will motivate further interest in cross-linked polymers and framework materials for sensing applications. PMID:23641956

Gopalakrishnan, Deepti; Dichtel, William R

2013-06-01

414

The Maximum Patch Method for Directional Dark Matter Detection  

Microsoft Academic Search

Present and planned dark matter detection experiments search for WIMP-induced nuclear recoils in poorly known background conditions. In this environment, the maximum gap statistical method provides a way of setting more sensitive cross-section upper limits by incorporating known signal information. We give a recipe for the numerical calculation of maximum gap cumulative distribution functions in one dimension, and extend the

Shawn Henderson; Jocelyn Monroe; Peter Fisher

2008-01-01

415

Direct Gray-Scale Minutiae Detection In Fingerprints  

Microsoft Academic Search

Most automatic systems for fingerprint comparison are based on minutiae matching. Minutiae are essentially terminations and bifurcations of the ridge lines that constitute a fingerprint pattern. Automatic minutiae detection is an extremely critical process, especially in low-quality fingerprints where noise and contrast deficiency can originate pixel configurations similar to minutiae or hide real minutiae. Several approaches have been proposed in

Dario Maio; Davide Maltoni

1997-01-01

416

Detection of regions of interest and camouflage breaking by direct convexity estimation  

Microsoft Academic Search

Detection of regions of interest is usually based on edge maps. We suggest a novel nonedge-based mechanism for detection of regions of interest, which extracts 3D information from the image. Our operator detects smooth 3D convex and concave objects based on direct processing of intensity values. Invariance to a large family of functions is mathematically proved. It follows that our

Ariel Tankus; Yehezkel Yeshurun

1998-01-01

417

Effect of Directional Speech Warnings on Road Hazard Detection  

Microsoft Academic Search

Background: In the last 2 decades, cognitive science and the transportation psychology field have dedicated a lot of effort to designing advanced driver support systems. Verbal warning systems are increasingly being implemented in modern automobiles in an effort to increase road safety.Objective: The study presented here investigated the impact of directional speech alert messages on the participants’ speed to judge

Jesús Serrano; Leandro L. Di Stasi; Alberto MegíAs; Andrés Catena

2011-01-01

418

High-throughput colorimetric assays for nucleotide sugar formation and glycosyl transfer.  

PubMed

Glycosyltransferases are ubiquitous in nature, catalyzing glycosidic bond formation in the context of an enormous range of substrates, which include all major classes of biological molecules. Because this wide range of substrates lacks a shared, distinguishable feature that can be altered by glycosyl transfer, general assays for detection of glycosyltransferase activity have long been largely limited to low-throughput methods. Of those high-throughput assays reported in the literature, many are confined to specific glycosyl transfer reactions with modified aglycon acceptors selected for their unique analytical properties. Herein are described a series of protocols centered on the use of 2-chloro-4-nitrophenyl glycoside donors and the reversibility of glycosyltransferase-catalyzed reactions to enable a colorimetric assay for the formation of sugar nucleotides, coupled reaction systems for the glycodiversification of small molecules, and a general colorimetric assay for glycosyltransfer, applicable to drug discovery, protein engineering, and other fundamental sugar nucleotide-dependent investigations. PMID:23034237

Gantt, Richard W; Thorson, Jon S

2012-01-01

419

PoS(ICHEP2010)539 Dark Matter direct detection searches  

E-print Network

PoS(ICHEP2010)539 Dark Matter direct detection searches Jules Gascon IPNL, Université de Lyon searches for Dark Matter is presented. These experi- ments look for energetic recoiling ions produced)539 Direct Searches for Dark Matter Jules Gascon Direct searches for Dark Matter in the form of Weakly

Boyer, Edmond

420

2001 Progress on a Direct Brain Interface Based on Detection of ERPs in ECoG  

E-print Network

University Graz: G. Pfurtscheller, B. Graimann A direct brain interface is defined as a human-computer2001 Progress on a Direct Brain Interface Based on Detection of ERPs in ECoG The University interface that accepts voluntary commands directly from the brain. This NIH bioengineering research

Fessler, Jeffrey A.

421

Protein-based nanobiosensor for direct detection of hydrogen sulfide  

NASA Astrophysics Data System (ADS)

The chemically modified cytochrome c from equine heart, EC (232-700-9), was immobilized onto gold nanoparticles in order to develop a specific biosensing system for monitoring hydrogen sulfide down to the micromolar level, by means of a localized surface plasmon resonance spectroscopy. The sensing mechanism is based on the cytochrome-c conformational changes in the presence of H2S which alter the dielectric properties of the gold nanoparticles and the surface plasmon resonance peak undergoes a redshift. According to the experiments, it is revealed that H2S can be detected at a concentration of 4.0 ? \\text{M} (1.3 \\text{ppb}) by the fabricated biosensor. This simple, quantitative and sensitive sensing platform provides a rapid and convenient detection for H2S at concentrations far below the hazardous limit.

Omidi, Meisam; Amoabediny, Ghasem; Yazdian, Fatemeh; Habibi-Rezaei, M.

2015-01-01

422

Enabling Technologies for Direct Detection Optical Phase Modulation Formats  

Microsoft Academic Search

Phase modulation formats are believed to be one of the key enabling techniques for next generation high speed long haul fiber-optic communication systems due to the following main advantages: (1) with a balanced detection, a better receiver sensitivity over conventional intensity modulation formats, e.g., a ˜3-dB sensitivity improvement using differential phase shift keying (DPSK) and a ˜1.3-dB sensitivity improvement using

Xian Xu

2009-01-01

423

Rapid Detection and Identification of Respiratory Viruses by Direct Immunofluorescence  

PubMed Central

The use of fluorescein-conjugated antiserum against respiratory syncytial (RS) and parainfluenza 1 and 3 viruses was compared with conventional techniques in the rapid detection of virus in tissue cultures inoculated with pharyngeal specimens known to contain these viruses. Twenty-three specimens were tested: 9 RS, 8 parainfluenza 1, and 6 parainfluenza 3. The fluorescent-antibody technique (FA) detected virus in 52% of the tissue cultures in 24 hr, and, by 72 hr, 22 of the 23 cultures were FA-positive whereas only 5 were positive by conventional techniques. Additionally, conjugated antisera were prepared against herpes simplex, influenza A2, and adenovirus type 5. All conjugates stained only the homologous virus and were 100- to 10,000-fold more sensitive than conventional techniques in detecting descending dilutions of virus inocula by 24 hr. With the procedures described, several antisera could be conjugated and ready for use within 24 hr. Serum fractionation was by ammonium sulfate precipitation, and with the procedure outlined virtually complete recovery of the globulin fraction and elimination of all of the albumin were accomplished. Images PMID:4098101

D'Alessio, Donn; Williams, Stanley; Dick, Elliot C.

1970-01-01

424

Bio-functionalized silver nanoparticles for selective colorimetric sensing of toxic metal ions and antimicrobial studies  

NASA Astrophysics Data System (ADS)

Hibiscus Sabdariffa (Gongura) plant extracts (leaves (HL) and stem (HS) were used for the first time in the green synthesis of bio-functionalized silver nanoparticles (AgNPs). The bio-functionality of AgNPs has been successfully utilized for selective colorimetric sensing of potentially health and environmentally hazardous Hg2+, Cd2+ and Pb2+ metal ions at ppm level in aqueous solution. Importantly, clearly distinguishable colour for all three metal ions was observed. The influence of extract preparation condition and pH were also explored on the formation of AgNPs. Both selectivity and sensitivity differed for AgNPs synthesized from different parts of the plant. Direct correlation between the stability of green synthesized AgNPs at different pH and its antibacterial effects has been established. The selective colorimetric sensing of toxic metal ions and antimicrobial effect of green synthesized AgNPs demonstrated the multifunctional applications of green nanotechnology.

Vinod Kumar, V.; Anbarasan, S.; Christena, Lawrence Rene; SaiSubramanian, Nagarajan; Philip Anthony, Savarimuthu

2014-08-01

425

Bio-functionalized silver nanoparticles for selective colorimetric sensing of toxic metal ions and antimicrobial studies.  

PubMed

Hibiscus Sabdariffa (Gongura) plant extracts (leaves (HL) and stem (HS)) were used for the first time in the green synthesis of bio-functionalized silver nanoparticles (AgNPs). The bio-functionality of AgNPs has been successfully utilized for selective colorimetric sensing of potentially health and environmentally hazardous Hg(2+), Cd(2+) and Pb(2+) metal ions at ppm level in aqueous solution. Importantly, clearly distinguishable colour for all three metal ions was observed. The influence of extract preparation condition and pH were also explored on the formation of AgNPs. Both selectivity and sensitivity differed for AgNPs synthesized from different parts of the plant. Direct correlation between the stability of green synthesized AgNPs at different pH and its antibacterial effects has been established. The selective colorimetric sensing of toxic metal ions and antimicrobial effect of green synthesized AgNPs demonstrated the multifunctional applications of green nanotechnology. PMID:24717716

Vinod Kumar, V; Anbarasan, S; Christena, Lawrence Rene; SaiSubramanian, Nagarajan; Philip Anthony, Savarimuthu

2014-08-14

426

A prototype direct-detection CCD for protein crystallography  

PubMed Central

The fabrication and testing of a prototype deep-depletion direct-conversion X-ray CCD detector are described. The device is fabricated on 600?µm-thick high-resistivity silicon, with 24?×?24?µm pixels in a 4k?×?4k pixel format. Calibration measurements and the results of initial protein crystallography experiments at the Cornell High Energy Synchrotron Source (CHESS) F1 beamline are described, as well as suggested improvements for future versions of the detector. PMID:24046505

Green, Katherine S.; Szebenyi, Doletha M. E.; Boggs, Kasey; Bredthauer, Richard; Tate, Mark W.; Gruner, Sol M.

2013-01-01

427

Colorimetric artificial tongue for protein identification.  

PubMed

Artificial tongue systems are multisensory devices which are highly desirable for the analysis and recognition of complicated composition samples. Herein, a low-cost and simple colorimetric sensor array for identification and quantification of proteins were reported. Using prophyrin, porphyrin derivatives (mainly metalloporphyrins) and chemically responsive dyes as the sensing elements, the developed sensor array of artificial tongue showed a unique pattern of colorific change upon its exposure to proteins. The composite pattern for each sample was subjected to principal component analysis (PCA), thus providing a clustering map for more practical visualization. All the pure and mixed proteins, as well as denatured proteins, gave distinct patterns, thus resulting in their unambiguous identification. The PCA analysis also suggested that the unique pattern of colorific change may be due to the change of protein conformation and local environmental pH. These results demonstrate that the developed colorimetric artificial tongue system is an excellent sensing platform for identification and quantitative analysis of protein samples. PMID:21546237

Hou, Changjun; Dong, Jiale; Zhang, Guoping; Lei, Yu; Yang, Mei; Zhang, Yuchan; Liu, Zhen; Zhang, Suyi; Huo, Danqun

2011-06-15

428

Direct detection of a microlens in the Milky Way.  

PubMed

The nature of dark matter remains mysterious, with luminous material accounting for at most approximately 25 per cent of the baryons in the Universe. We accordingly undertook a survey looking for the microlensing of stars in the Large Magellanic Cloud (LMC) to determine the fraction of Galactic dark matter contained in massive compact halo objects (MACHOs). The presence of the dark matter would be revealed by gravitational lensing of the light from an LMC star as the foreground dark matter moves across the line of sight. The duration of the lensing event is the key observable parameter, but gives non-unique solutions when attempting to estimate the mass, distance and transverse velocity of the lens. The survey results to date indicate that between 8 and 50 per cent of the baryonic mass of the Galactic halo is in the form of MACHOs (ref. 3), but removing the degeneracy by identifying a lensing object would tighten the constraints on the mass in MACHOs. Here we report a direct image of a microlens, revealing it to be a nearby low-mass star in the disk of the Milky Way. This is consistent with the expected frequency of nearby stars acting as lenses, and demonstrates a direct determination of a lens mass from a microlensing event. Complete solutions such as this for halo microlensing events will probe directly the nature of the MACHOs. PMID:11740553

Alcock, C; Allsman, R A; Alves, D R; Axelrod, T S; Becker, A C; Bennett, D P; Cook, K H; Drake, A J; Freeman, K C; Geha, M; Griest, K; Keller, S C; Lehner, M J; Marshall, S L; Minniti, D; Nelson, C A; Peterson, B A; Popowski, P; Pratt, M R; Quinn, P J; Stubbs, C W; Sutherland, W; Tomaney, A B; Vandehei, T; Welch, D

2001-12-01

429

Detection of nucleic acid sequences by invader-directed cleavage  

SciTech Connect

The present invention relates to means for the detection and characterization of nucleic acid sequences, as well as variations in nucleic acid sequences. The present invention also relates to methods for forming a nucleic acid cleavage structure on a target sequence and cleaving the nucleic acid cleavage structure in a site-specific manner. The 5{prime} nuclease activity of a variety of enzymes is used to cleave the target-dependent cleavage structure, thereby indicating the presence of specific nucleic acid sequences or specific variations thereof. The present invention further relates to methods and devices for the separation of nucleic acid molecules based by charge.

Brow, M.A.D.; Hall, J.S.G.; Lyamichev, V.; Olive, D.M.; Prudent, J.R.

1999-12-14

430

Detection of nucleic acid sequences by invader-directed cleavage  

DOEpatents

The present invention relates to means for the detection and characterization of nucleic acid sequences, as well as variations in nucleic acid sequences. The present invention also relates to methods for forming a nucleic acid cleavage structure on a target sequence and cleaving the nucleic acid cleavage structure in a site-specific manner. The 5' nuclease activity of a variety of enzymes is used to cleave the target-dependent cleavage structure, thereby indicating the presence of specific nucleic acid sequences or specific variations thereof. The present invention further relates to methods and devices for the separation of nucleic acid molecules based by charge.

Brow, Mary Ann D. (Madison, WI); Hall, Jeff Steven Grotelueschen (Madison, WI); Lyamichev, Victor (Madison, WI); Olive, David Michael (Madison, WI); Prudent, James Robert (Madison, WI)

1999-01-01

431

A direct immunoassay for detecting diatoms in groundwater as an indicator of the direct influence of surface water  

USGS Publications Warehouse

Groundwater under the direct influence of surface water (GWUDISW) is of concern in communities where growing public demand on groundwater resources has resulted in increased withdrawals and hydraulic stress near surface water bodies. Under these conditions, contaminants such as methyl-tert butyl ether (MTBE) and biological materials have been detected in domestic wells. Other contaminants and pathogens associated with surface water are not routinely tested for in groundwater-supplied systems. To address the need for methods to easily identify potentially vulnerable supplies, a direct immunoassay for the quantitative detection of diatoms in raw water samples was developed as a measure of surface water influence on groundwater. Cell wall preparations from Nitzschia palea Ku??tzing, a freshwater diatom found throughout North America, were used to produce a polyclonal antibody that was applied in a direct enzyme-linked immunosorbent assay (ELISA) developed to detect the presence of N. palea cell wall components. The direct immunoassay allows detection at 500 cells L-1, a level similar to diatom concentrations observed in samples of groundwater collected near the test site. This investigation was the first attempt to utilize an ELISA as an indicator of surface water influence on groundwater. Further research is needed to develop more specific diatom-based monoclonal antibodies, determine cross-reactivity, and optimize sample processing and ELISA procedures for development of a standardized method. ?? Springer 2005.

Walker, C.E.; Schrock, R.M.; Reilly, T.J.; Baehr, A.L.

2005-01-01

432

Semiparametric detection of nonlinear causal coupling using partial directed coherence.  

PubMed

Infering causal relationships from observed time series has attracted much recent attention. In cases of nonlinear coupling, adequate inference is often hindered by the need to specify coupling details that call for many parameters and global minimization of nonconvex functions. In this paper we use an example to investigate a new concept, termed here running entropy mapping, whereby time series are mapped onto other entropy related time sequences whose analysis via a linear parametric time series methods, such as partial directed coherence, is able to expose the presence of formerly linearly undetectable causal relationships. PMID:22255689

Massaroppe, Lucas; Baccalá, Luiz Antonio; Sameshima, Koichi

2011-01-01

433

Dark matter direct detection in the MSSM with heavy scalars  

SciTech Connect

We explore the dark matter detection prospects in the Minimal Supersymmetric Standard Model in the scenario where the scalar partners of the fermions and the Higgs particles (except for the Standard-Model-like one) are assumed to be very heavy and are removed from the low-energy spectrum. We analyse the neutralino LSP (?{sub 1}{sup 0}) in scenarios where the gaugino mass parameters are universal at the GUT scale and also the case where they are non-universal. This analysis is carried out in the framework of a Xenon-like 100 kg experiment. In general, an important fraction of the parameter space giving rise to the dark matter relic density measured by WMAP can be probed and excluded in the case of not detecting any WIMP. In the opposite case, once a WIMP signal has been found, we show that for a light ?{sub 1}{sup 0} which is a higgsino-gaugino mixture it is possible to reconstruct efficiently the mass and the scattering cross-section of the neutralino LSP. Moreover, we show that it is also feasible to put strong constraints over some of the parameters of the Lagrangian, e.g. the higgsino and the gaugino mass parameters.

Bernal, Nicolás, E-mail: bernal@ecm.ub.es [High Energy Physics Group, Dept. ECM, and Institut de Ciències del Cosmos, Univ. de Barcelona, Av. Diagonal 647, E-08028 Barcelona, Catalonia (Spain)

2009-08-01

434

Future Directions for the Early Detection of Colorectal Cancer Recurrence  

PubMed Central

Surgical resection remains a mainstay of treatment and is highly effective for localized colorectal cancer. However, ~30-40% of patients develop recurrence following surgery and 40-50% of recurrences are apparent within the first few years after initial surgical resection. Several variables factor into the ultimate outcome of these patients, including the extent of disease, tumor biology, and patient co-morbidities. Additionally, the time from initial treatment to the development of recurrence is strongly associated with overall survival, particularly in patients who recur within one year of their surgical resection. Current post-resection surveillance strategies involve physical examination, laboratory, endoscopic and imaging studies utilizing various high and low-intensity protocols. Ultimately, the goal is to detect recurrence as early as possible, and ideally in the asymptomatic localized phase, to allow initiation of treatment that may still result in cure. While current strategies have been effective, several efforts are evolving to improve our ability to identify recurrent disease at its earliest phase. Our aim with this article is to briefly review the options available and, more importantly, examine emerging and future options to assist in the early detection of colon and rectal cancer recurrence. PMID:24790655

Walker, Avery S.; Johnson, Eric K.; Maykel, Justin A.; Stojadinovic, Alex; Nissan, Aviram; Brucher, Bjorn; Champagne, Bradley J.; Steele, Scott R.

2014-01-01

435

Colorimetric consideration of transparencies for a typical LACIE scene  

NASA Technical Reports Server (NTRS)

The production film converter used to produce LACIE imagery is described as well as schemes designed to provide the analyst with operational film products. Two of these products are discussed from the standpoint of color theory. Colorimetric terminology is defined and the mathematical calculations are given. Topics covered include (1) history of product 1 and 3 algorithm development; (2) colorimetric assumptions for product 1 and 3 a