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1

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

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

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

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

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.

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

2010-01-01

6

Direct colorimetric assay of microcystin using protein phosphatase  

Microsoft Academic Search

A new direct colorimetric assay of microcystin in water and algal samples is proposed consisting of two procedures as follows:\\u000a 1) the elimination of phosphorus in the sample and concentration of microcystin using a C18 cartridge, 2) the detection of the released phosphorus by the ascorbic acid method and determination of protein phosphatase\\u000a (PP) inhibition by microcystin. The optimum amounts

Hee-Mock Oh; Seog June Lee; Jee-Hwan Kim; Chan-Sun Park; Byung-Dae Yoon

2000-01-01

7

Optical colorimetric sensor strip for direct readout glucose measurement.  

PubMed

A novel direct readout colorimetric optical glucose sensor strip was constructed based on a three-layer film, including a green-emitted CdTe/CdS quantum dots (QDs) layer as a stable color background, a red-fluorescent platinum-porphyrin oxygen-sensing layer and a glucose oxidase layer. The sensor achieved high resolution (up to 0.2 mmol L(-1)) glucose determination with a detection range from 0 to 3.0 mmol L(-1). A "glucose ruler" which acts as a glucose standard colorimetric card was obtained. Glucose concentration could easily be directly readout using the "glucose ruler", which made the glucose determination rapid, convenient and easy. The effects of pH, salinity and temperature were systematically investigated. The prepared sensor was finally applied for glucose sample analysis, compared with the "glucose ruler", accurate results could be directly readout. PMID:19523808

Wang, Xu-dong; Chen, Hai-xu; Zhou, Ting-yao; Lin, Zhi-jie; Zeng, Jing-bin; Xie, Zhao-xiong; Chen, Xi; Wong, Kwok-yin; Chen, Guo-nan; Wang, Xiao-ru

2009-08-15

8

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

9

Pre-oxidation for Colorimetric Sensor Array Detection of VOCs  

PubMed Central

A disposable pre-oxidation technique is reported that dramatically improves the detection and identification of volatile organic compounds (VOCs) by a colorimetric sensor array. By passing a vapor stream through a tube packed with chromic acid on silica immediately before the colorimetric sensor array, the sensitivity to less reactive VOCs is substantially increased and limits of detection (LODs) are improved ~300-fold, permitting the detection, identification, and discrimination of 20 commonly found indoor VOC pollutants at both their immediately dangerous to life or health (IDLH) and at permissible exposure limits (PEL) concentrations. LODs of these pollutants were on average 1.4% of their respective PELs.

Lin, Hengwei; Jang, Minseok; Suslick, Kenneth S.

2011-01-01

10

Preoxidation for colorimetric sensor array detection of VOCs.  

PubMed

A disposable preoxidation technique that dramatically improves the detection and identification of volatile organic compounds (VOCs) by a colorimetric sensor array is reported. Passing a vapor stream through a tube packed with chromic acid on silica immediately before the colorimetric sensor array substantially increases the sensitivity to less-reactive VOCs and improves the limits of detection (LODs) ~300-fold, permitting the detection, identification, and discrimination of 20 commonly found indoor VOC pollutants at both their immediately dangerous to life or health (IDLH) and permissible exposure limit (PEL) concentrations. The LODs of these pollutants were on average 1.4% of their respective PELs. PMID:21967478

Lin, Hengwei; Jang, Minseok; Suslick, Kenneth S

2011-10-26

11

Ultrasensitive colorimetric detection of Cu2+ using gold nanorods.  

PubMed

We utilized Cu(2+) induced gold nanorod shortening in the presence of Na2S2O3 and NH3 for colorimetric sensing of copper ions. Compared with conventional methods, this method has good reproducibility, fast response time and very high sensitivity to Cu(2+). The sensor has a large dynamic range for Cu(2+) covering 5 nM to 500 mM with a detection limit of 1.6 nM, which is lower than previously reported for the colorimetric detection of copper ions. PMID:24741668

Niu, Xiaofang; Xu, Dong; Yang, Yunhui; He, Yan

2014-06-01

12

Selectively colorimetric detection of cysteine with triangular silver nanoprisms  

Microsoft Academic Search

Triangular silver nanoprisms were prepared and applied to make colorimetric detection of cysteine based on our findings that cysteine could lead to the blue shift of the dipole plasmon resonance absorption, but other 19 kinds of natural amino acids could not. Cysteine with a concentration 160nmol\\/L can result in a color change that can be discerned with naked eyes.

Tong Wu; Yuan Fang Li; Cheng Zhi Huang

2009-01-01

13

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

14

Colorimetric viral detection based on sialic acid stabilized gold nanoparticles  

PubMed Central

Sialic acid reduced and stabilized gold nanoparticles (d = 20.1 ± 1.8 nm) were synthesized by a simple one-pot, green method without chemically modifying sialic acid for colorimetric detection of influenza virus. The gold nanoparticles showed target-specific aggregation with viral particles via hemagglutinin-sialic acid binding. A linear correlation was observed between the change in optical density and dilution of chemically inactivated influenza B/Victoria and influenza B/Yamagata. Virus dilution (hemagglutinination assay titer, 512) of 0.156 vol% was readily detected. The upper limit of the linearity can be extended with the use of more sialic acid-gold nanoparticles.

Lee, Changwon; Gaston, Marsha A.; Weiss, Alison A.; Zhang, Peng

2012-01-01

15

Catalyst screening for oxidative reforming of methane in direct route using high pressure HTS reactor with syngas detection system by colorimetric reaction and gas chromatograph.  

PubMed

A high-throughput screening (HTS) reactor for high-pressure oxidative reforming of methane in a direct reaction route was developed. With a combination of catalyst preparation by a split-and-pool method and HTS, Ni-K/alpha-Al(2)O(3) catalyst was found to show high activity under 1 MPa at 650 degrees C with high selectivity even when O(2) conversion is less than 100%. The HTS reactor required a new simple syngas detector operable under high pressure because the number of parallel reactor is limited when equipped with the conventional detection system. The complexity of the pressure reducing unit is the main reason of the limitation. Reduction of metal oxide accompanied with the color change was applied to the detection system. Copper oxide was supported on the filter disk made of alumina, and the filter was placed underneath the catalyst bed. After the methane was oxidatively reformed under 1 MPa at 650 degrees C, color change of spots from dark brown to light brown was observed just under the catalyst which produced hydrogen. Color change of the disk can be used to detect hydrogen formation from the reforming catalyst under pressure. PMID:19133839

Omata, Kohji; Ishii, Hidetomo; Horiguchi, Junpei; Kobayashi, Seishiro; Yamazaki, Yuichiro; Yamada, Muneyoshi

2009-01-01

16

Colorimetric Detection and Identification of Natural and Artificial Sweeteners  

PubMed Central

A disposable, low-cost colorimetric sensor array has been created by pin-printing onto a hydrophilic membrane 16 chemically responsive nanoporous pigments made from 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.

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

2009-01-01

17

Colorimetric/fluorogenic detection of thiols by N-fused porphyrin in water.  

PubMed

A water-soluble derivative of N-fused porphyrin (NFP) possessing four cationic side-arms (pPyNFP) serves as a unique class of colorimetric/fluorogenic reporters that selectively react with biothiols in aquaous media to afford N-confused porphyrin (NCP) derivatives, while other nucleophilic amino acids were inert under a wide range of pH conditions. Owing to the large difference of the optical properties between NCP and NFP, the transformation enabled selective detection of biothiols in colorimetric/fluorogenic manner, especially in the near-infrared region. To the best our knowledge, this is the first example of porphyrin-based thiol detection systems that use the direct attack of thiol group on the optical reporter. PMID:24051075

Ikawa, Yoshiya; Touden, Satoshi; Katsumata, Sho; Furuta, Hiroyuki

2013-11-01

18

A colorimetric biosensor for the detection of foodborne bacteria  

Microsoft Academic Search

We have synthesized 10,12-pentacosadyinoic acid (PCDA)+N-[(2-tetradecanamide)-ethyl]-ribonamide (TDER) vesicles to determine the colorimetric response induced by pathogenic bacteria (Staphylococcus aureus and Escherichia coli). The addition of bacterial supernatants caused a colorimetric transition in TDER\\/PCDA vesicles, even in diluted concentrations, indicating that chemical interactions occur between the vesicles and bacterial compounds. Bacterial substrates released from S. aureus induced a greater color change

Ana Clarissa dos Santos Pires; Nilda de Fátima Ferreira Soares; Luis Henrique Mendes da Silva; Maria do Carmo Hespanhol da Silva; Mauro Vieira De Almeida; Mireille Le Hyaric; Nélio José de Andrade; Rêmili Freitas Soares; Aparecida Barbosa Mageste; Samira Gama Reis

2011-01-01

19

Microplate-based colorimetric detection of free hydrogen sulfide.  

PubMed

Hydrogen sulfide (H2S) has recently been recognized as an important physiologically relevant gasotransmitter. Produced by the enzymes involved in the transsulfuration pathway, cystathionine ?-synthase (CBS) and cystathionine ?-lyase (CSE), H2S has been implicated to control biological activity in virtually every organ system. In recent years it is being recognized that many commonly used H2S assays do not measure free H2S specifically and may be prone to artifacts. This has led to large variations in the reported H2S biological concentrations. In order to accurately study H2S's functions in biological systems accurate assays which measure free H2S specifically are required. In this work we present a simple microplate-based colorimetric assay for H2S gas. The underside of a 96-well microplate cover was coated with Nafion polymer doped with Ag(+) ions. H2S is a highly volatile gas, and as it is volatilized in the microplate well it reacts with Ag(+) to produce Ag2S nanoparticles, which have a strong absorbance in the low-UV range. By monitoring the absorbance change from formation of Ag2S nanoparticles, H2S production can be monitored in real time. The assay has a limit of detection (LOD) of 2.61 nmol (8.70 ?M) and a liner range up to 30 nmol (100 ?M). Using the assay, the KM and Vmax of recombinant CSE enzyme were determined to be 11.13 ± 0.57 mM and 0.45 ± 0.01 nmol min(-1), respectively. H2S production from mouse liver homogenate under aerobic conditions in the presence of cysteine was measured and determined to be 4.89 ± 0.19 nmol min(-1) mL(-1) homogenate. The assay is simple, low cost, and specific to free H2S gas. PMID:23477661

Jarosz, Artur P; Yep, Terence; Mutus, Bulent

2013-04-01

20

Colorimetric detection of urea nitrate: The missing link  

Microsoft Academic Search

Traces of the improvised explosive urea nitrate can be characterized by a sensitive colorimetric reaction with p-dimethylaminocinnamalaldehyde (p-DMAC, UN-1 reagent). As recently shown, the dark red product has a structure of a protonated Schiff base. The unprotonated free base, previously postulated in the literature to be the colored product, was now prepared and fully characterized. It shows totally different spectroscopic

Rinat Rozin; Joseph Almog

2011-01-01

21

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

22

Comparison of an electrochemiluminescence assay in plate format over a colorimetric ELISA, for the detection of ricin B chain (RCA-B)  

Microsoft Academic Search

An electrochemiluminescence (ECL) assay for the detection of the B chain of ricin (RCA-B) in a 96-well plate format was developed in parallel with a colorimetric ELISA utilizing the same pair of antibodies. Sensitivity results were interpreted with the ANOVA and Tukey statistical tests, allowing a direct comparison between the two technologies, that can probably be extended to other protein

V. Guglielmo-Viret; P. Thullier

2007-01-01

23

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

24

A colorimetric and fluorometric dual-modal supramolecular chemosensor and its application for HSA detection.  

PubMed

A colorimetric and fluorometric dual-modal supramolecular chemosensor has been fabricated by using the H- and J-aggregates of a cyanine dye, which has been successfully applied to detect human serum albumin (HSA) in urine with high specificity. PMID:24325001

Sun, Hongxia; Xiang, Junfeng; Zhang, Xiufeng; Chen, Hongbo; Yang, Qianfan; Li, Qian; Guan, Aijiao; Shang, Qian; Tang, Yalin; Xu, Guangzhi

2014-02-01

25

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

26

Substitution of thiophene oligomers with macrocyclic end caps and the colorimetric detection of Hg(II).  

PubMed

Alkyl substitution at the ? position(s) of mono-, bi-, and terthiophenes via electrophilic addition of macrocyclic end caps combines linear, ?-conjugated aromatic compounds and annular macrocycles. Addition of the Hg(II) ion to terthiophene adducts produces intense color changes, allowing for the selective, colorimetric detection of mercury(II). Chemical oxidation of the asymmetric terthiophene adduct produces the sexithiophene oligomer. PMID:21476535

Kadarkaraisamy, Mariappan; Thammavongkeo, Soudsakhone; Basa, Prem N; Caple, Gerald; Sykes, Andrew G

2011-05-01

27

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

28

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

29

A colorimetric method for point mutation detection using high-fidelity DNA ligase  

Microsoft Academic Search

The present study reported proof-of-principle for a genotyping assay approach that can detect single nucleotide polymorphisms (SNPs) through the gold nanoparticle assembly and the ligase reaction. By incorporating the high-fidelity DNA ligase (Tth DNA ligase) into the allele-specific ligation-based gold nanoparticle assembly, this assay provided a conve- nient yet powerful colorimetric detection that enabled a straightforward single-base discrimination without the

Jishan Li; Xia Chu; Yali Liu; Jian-Hui Jiang; Zhimin He; Zhiwei Zhang; Guoli Shen; Ru-Qin Yu

2005-01-01

30

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

PubMed Central

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

2014-01-01

31

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

PubMed

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 × 10(3) and 5.0 × 10(6)?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. PMID:24898751

Wen, Junlin; Zhou, Shungui; Chen, Junhua

2014-01-01

32

Gold nanoparticle aggregation-based colorimetric assay for ?-casein detection in bovine milk samples.  

PubMed

Traditional Kjeldahl method, used for quality evaluation of bovine milk, has intrinsic defects of time-consuming sample preparation and two analyses to determine the difference between non-protein nitrogen content and total protein nitrogen content. Herein, based upon antibody functionalized gold nanoparticles (AuNPs), we described a colorimetric method for ?-casein (?-CN) detection in bovine milk samples. The linear dynamic range and the LOD were 0.08-250?gmL(-1), and 0.03?gmL(-1) respectively. In addition, the real content of ?-CN in bovine milk was measured by using the developed assay. The results are closely correlated with those from Kjeldahl method. The advantages of ?-CN triggered AuNP aggregation-based colorimetric assay are simple signal generation, the high sensitivity and specificity as well as no need of complicated sample preparation, which make it for on-site detection of ?-CN in bovine milk samples. PMID:24874352

Li, Y S; Zhou, Y; Meng, X Y; Zhang, Y Y; Song, F; Lu, S Y; Ren, H L; Hu, P; Liu, Z S; Zhang, J H

2014-11-01

33

Novel core etching technique on synthesized gold nanoparticles for colorimetric detection of dopamine biosample  

Microsoft Academic Search

This study develops a novel and high performance colorimetric probe for dopamine (DA) detection. Aqueous-phase gold nanoparticles (AuNPs) extracted with 4-(dimethylamino) pyridine (DMAP) from toluene solvent is used as the reaction probes. The conjugated AuNPs of the diameter around 13 nm disperse into the size of 2–5 nm while adding dopamine (DA), resulting in the color change of the AuNPs

Ho-Cheng Leel; Tzu-Heng Chen; Wei-Lung Tseng; Che-Hsin Linl

2012-01-01

34

Spiropyran as a reusable chemosensor for selective colorimetric detection of aromatic thiols.  

PubMed

Design of optical molecular probes for selective detection of aromatic thiols has attracted much attention. Although several types of probes have been proposed, all of them exhibit colorimetric or fluorometric response via irreversible reaction with aromatic thiols and cannot be reused. Here we report that a spiropyran dye is the first example of a reusable chemosensor for aromatic thiols. A colorless spiropyran dye () dissolved in aqueous media containing aromatic thiols is selectively isomerized to the colored merocyanine form in the dark. In contrast, visible light irradiation of the merocyanine form promotes successful reversion to the colorless spirocyclic form. Kinetic absorption analysis and ab initio calculations of the transition states revealed that this colorimetric response in the dark is ascribed to the decrease in activation energy for isomerization via the nucleophilic interaction between the aromatic thiol and the olefinic carbon of the dye. PMID:24616910

Shiraishi, Yasuhiro; Yamamoto, Kohei; Sumiya, Shigehiro; Hirai, Takayuki

2014-06-28

35

G-quadruplex-generating polymerase chain reaction for visual colorimetric detection of amplicons.  

PubMed

We have developed a self-reporting polymerase chain reaction (PCR) system for visual colorimetric gene detection and distinction of single nucleotide polymorphisms (SNPs). Amplification is performed using target-specific primers modified with a 5'-end tail that is complementary to a G-quadruplex deoxyribozyme-forming sequence. At end-point, G-quadruplexes are forced to fold from PCR-generated duplex DNA and then are used to colorimetrically report the successful occurrence of PCR by assaying their peroxidase activity using a chromogenic substrate. Furthermore, primer design considerations for the G-quadruplex-generating PCR system have allowed us to visually distinguish SNPs associated with Mycobacterium tuberculosis drug resistance alleles. PMID:24135653

Bhadra, Sanchita; Codrea, Vlad; Ellington, Andrew D

2014-01-15

36

[Detection of viable metabolically active yeast cells using a colorimetric assay].  

PubMed

The increasing concern of yeasts able to form biofilm brings about the need for susceptibility testing of both planktonic and biofilm cells. Detection of viability or metabolic activity of yeast cells after exposure to antimicrobials plays a key role in the assessment of susceptibility testing results. Colorimetric assays based on the color change of the medium in the presence of metabolically active cells proved suitable for this purpose. In this study, the usability of a colorimetric assay with the resazurin redox indicator for monitoring the effect of yeast inoculum density on the reduction rate was tested. As correlation between the color change rate and inoculum density was observed, approximate quantification of viable cells was possible. The assay would be of relevance to antifungal susceptibility testing in both planktonic and biofilm yeasts. PMID:18318392

R?zicka, F; Holá, V

2008-02-01

37

A Colorimetric Sensor for Qualitative Discrimination and Quantitative Detection of Volatile Amines  

PubMed Central

We have developed a novel colorimetric sensor based on a digital camera and white LED illumination. Colorimetric sensor arrays (CSAs) were made from a set of six chemically responsive dyes impregnated on an inert substrate plate by solution casting. Six common amine aqueous solutions, including dimethylamine, triethylamine, diisopropylamine, aniline, cyclohexylamine, and pyridine vaporized at 25 °C and six health-related trimethylamine (TMA) concentrations including 170 ppm, 51 ppm, 8 ppm, 2 ppm, 125 ppb and 50 ppb were analyzed by the sensor to test its ability for the qualitative discrimination and quantitative detection of volatile amines. We extracted the feature vectors of the CSA's response to the analytes from a fusional color space, which was obtained by conducting a joint search algorithm of sequential forward selection and sequential backward selection (SFS&SBS) based on the linear discriminant criteria (LDC) in a mixed color space composed of six common color spaces. The principle component analysis (PCA) followed by the hierarchical cluser analysis (HCA) were utilized to discriminate 12 analytes. Results showed that the colorimetric sensor grouped the six amine vapors and five TMA concentrations correctly, while TMA concentrations of 125 ppb and 50 ppb were indiscriminable from each other. The limitation of detection (LOD) of the sensor for TMA was found to be lower than 50 ppb. The CSAs were reusable for TMA concentrations below 8 ppm.

Tang, Zhonglin; Yang, Jianhua; Yu, Junyun; Cui, Bo

2010-01-01

38

A Simple and Highly Sensitive Colorimetric Detection Method for Gaseous Formaldehyde  

PubMed Central

A colorimetric detection method using amine functionalized polymer films doped with a pH indicator has been developed for the rapid, sensitive and quantitative detection of gaseous formaldehyde at concentrations well below the IDLH (immediately dangerous to life or health). In one minute, visible color changes are easily observed even down to the PEL (permissible exposure limit) at 750 ppb. The limit of detection is below 50 ppb (7% of PEL) after 10 min exposure. This sensor is essentially unaffected by changes in humidity or temperature (4 to 50 °C) and is not sensitive to common interferents.

Feng, Liang; Musto, Christopher J.; Suslick, Kenneth S.

2010-01-01

39

A simple and highly sensitive colorimetric detection method for gaseous formaldehyde.  

PubMed

A colorimetric detection method using amine-functionalized polymer films doped with a pH indicator has been developed for the rapid, sensitive, and quantitative detection of gaseous formaldehyde at concentrations well below the immediately dangerous to life or health (IDLH) limit. In 1 min, visible color changes are easily observed, even down to the permissible exposure limit (PEL) at 750 ppb. The limit of detection is below 50 ppb (7% of the PEL) after 10 min of exposure. This sensor is essentially unaffected by changes in humidity or temperature (4 to 50 degrees C) and is not sensitive to common interferents. PMID:20218682

Feng, Liang; Musto, Christopher J; Suslick, Kenneth S

2010-03-31

40

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

41

Prussian blue nanoparticles as peroxidase mimetics for sensitive colorimetric detection of hydrogen peroxide and glucose.  

PubMed

Prussian blue nanoparticles (PB NPs) exhibits an intrinsic peroxidase-like catalytic activity towards the hydrogen peroxide (H2O2)-mediated oxidation of classical peroxidase substrate 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt to produce a colored product. The catalysis follows Michaelis-Menen kinetics and shows strong affinity for H2O2. Using PB NPs as a peroxidase mimetics, a colorimetric method was developed for the detection of 0.05-50.0 ?M H2O2, with a detection limit of 0.031 ?M. When the catalytic reaction of PB NPs was coupled with the reaction of glucose oxidation catalyzed by glucose oxidase, a sensitive and selective colorimetric method for the detection of glucose was realized. The limit of detection for glucose was determined to be as low as 0.03 ?M and the linear range was from 0.1 ?M to 50.0 ?M. The method was successfully applied to the determination of glucose in human serum. Compared with other nanomaterials-based peroxidase mimetics, PB NPs provides 10-100 times higher sensitivity toward the detection of H2O2 and glucose. The detection platform developed showed great potential applications in varieties of physiological importance substances when merged with appropriate H2O2-producing oxidases. PMID:24468383

Zhang, Weimin; Ma, Diao; Du, Jianxiu

2014-03-01

42

[Research on parameters of dynamic colorimetric temperature sensor and it's application to fuel air explosion temperature field detection].  

PubMed

According to the theory of colorimetric thermometry,the influences of center wavelength, wavelength bandwidth and solid angle on response speed and the precision of the sensor was analyzed systematically, and the operating parameters for transient high temperature measurement system were determined. A calculation method based on photoelectric conversion coefficient, and higher and lower operating wavelength of the colorimetric temperature sensor was given. At the optimal operating temperature, calibration experiment was conducted in a high temperature blackbody furnace. Based on the experimental results, the operating parameters of the sensor were determined and the colorimetric temperature response was calculated. The results show that the errors between the calculated response and the experiment one are less than 1%. By using the colorimetric temperature sensor, the temperature response of fuel air explosion field was detected and the variations of temperature with time and space in detonation field were obtained. PMID:24369654

Li, Lei; Liu, Qing-ming; Wang, Jian-ping

2013-09-01

43

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.

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

2014-01-01

44

Cationic surfactant-based colorimetric detection of Plasmodium lactate dehydrogenase, a biomarker for malaria, using the specific DNA aptamer.  

PubMed

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

45

Colorimetric Immuno-Protein Phosphatase Inhibition Assay for Specific Detection of Microcystins and Nodularins of Cyanobacteria  

PubMed Central

A novel immunoassay was developed for specific detection of cyanobacterial cyclic peptide hepatotoxins which inhibit protein phosphatases. Immunoassay methods currently used for microcystin and nodularin detection and analysis do not provide information on the toxicity of microcystin and/or nodularin variants. Furthermore, protein phosphatase inhibition-based assays for these toxins are not specific and respond to other environmental protein phosphatase inhibitors, such as okadaic acid, calyculin A, and tautomycin. We addressed the problem of specificity in the analysis of protein phosphatase inhibitors by combining immunoassay-based detection of the toxins with a colorimetric protein phosphatase inhibition system in a single assay, designated the colorimetric immuno-protein phosphatase inhibition assay (CIPPIA). Polyclonal antibodies against microcystin-LR were used in conjunction with protein phosphatase inhibition, which enabled seven purified microcystin variants (microcystin-LR, -D-Asp3-RR, -LA, -LF, -LY, -LW, and -YR) and nodularin to be distinguished from okadaic acid, calyculin A, and tautomycin. A range of microcystin- and nodularin-containing laboratory strains and environmental samples of cyanobacteria were assayed by CIPPIA, and the results showed good correlation (R2 = 0.94, P < 0.00001) with the results of high-performance liquid chromatography with diode array detection for toxin analysis. The CIPPIA procedure combines ease of use and detection of low concentrations with toxicity assessment and specificity for analysis of microcystins and nodularins.

Metcalf, James S.; Bell, Steven G.; Codd, Geoffrey A.

2001-01-01

46

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

47

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

48

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

2014-07-28

49

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

Microsoft Academic Search

In this paper, we demonstrate a simple and sensitive colorimetric detection of cysteine based on the cysteine-mediated color\\u000a change of ssDNA-stabilized gold nanoparticles (AuNPs). Cysteine is capable of absorbing onto AuNPs surfaces via the strong\\u000a interaction between its thiol group and gold. ssDNA molecules which stabilize AuNPs against salt-induced aggregation are removed\\u000a away by cysteine encapsulation on the AuNPs surfaces,

Zhang Chen; Shenglian Luo; Chengbin Liu; Qingyun Cai

2009-01-01

50

DNA based gold nanoparticles colorimetric sensors for sensitive and selective detection of Ag(I) ions  

Microsoft Academic Search

In this work, we reported both unlabeled and labeled sensing strategies for Ag(I) ions detection by using the DNA based gold nanoparticles (AuNPs) colorimetric method. In the unlabeled strategy, C-base riched single strand DNA (C-ssDNA) enwinded onto AuNPs to form AuNPs\\/C-ssDNA complex. In the labeled method, sulfhydryl group modified C-ssDNA (HS-C-ssDNA) was covalently labeled on AuNPs to produce AuNPs-S-C-ssDNA complex.

Bingling Li; Yan Du; Shaojun Dong

2009-01-01

51

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

52

A reversible competition colorimetric assay for the detection of biothiols based on ruthenium-containing complex.  

PubMed

A novel reversible colorimetric sensor, which based on a competitive ligation of Hg(2+) by thiols, cysteine (Cys) or glutathione (GSH), and thiocyanate (SCN) on the N3 dye (bis(4,4'-dicarboxy-2,2'-bipyridine) dithiocyanato ruthenium (II)), was developed for the detection of biothiols. First, Hg(2+) ions coordinate to the sulfur atom of the dyes' SCN groups, and this interaction induces a change in color from red to yellow, owing to the formation of a complex of Hg(2+)-N3. Then, in the presence of biothiols, the red color of N3 is recovered concomitantly with the dissociation of the Hg(2+)-N3 complex, due to the extraction of Hg(2+) by biothiols. Thus the corresponding color variation in the process of the dissociation of the Hg(2+)-N3 complex can be employed for the quantitative detection of thiols using UV-vis spectroscopy. In particular, the transformation can be readily viewed with the naked eye. A good linear relationship between the change in absorbance (?Abs) of Hg(2+)-N3 at 461 nm and the thiol concentration was obtained in the range of 0.5-25 ?M, and the detection limits are then calculated to be 57 and 52 nM for Cys and GSH, respectively. The proposed colorimetric assay displays a high selectivity for Cys over various other amino acids and GSSG (oxidized glutathione). PMID:24054588

Hao, Yuanqiang; Xiong, Dandan; Wang, Liqiang; Chen, Wansong; Zhou, Binbin; Liu, You-Nian

2013-10-15

53

Colorimetric test-systems for creatinine detection based on composite molecularly imprinted polymer membranes.  

PubMed

An easy-to-use colorimetric test-system for the efficient detection of creatinine in aqueous samples was developed. The test-system is based on composite molecularly imprinted polymer (MIP) membranes with artificial receptor sites capable of creatinine recognition. A thin MIP layer was created on the surface of microfiltration polyvinylidene fluoride (PVDF) membranes using method of photo-initiated grafting polymerization. The MIP layer was obtained by co-polymerization of a functional monomer (e.g. 2-acrylamido-2-methyl-1-propanesulfonic acid, itaconic acid or methacrylic acid) with N, N'-methylenebisacrylamide as a cross-linker. The choice of the functional monomer was based on the results of computational modeling. The creatinine-selective composite MIP membranes were used for measuring creatinine in aqueous samples. Creatinine molecules were selectively adsorbed by the MIP membranes and quantified using color reaction with picrates. The intensity of MIP membranes staining was proportional to creatinine concentration in an analyzed sample. The colorimetric test-system based on the composite MIP membranes was characterized with 0.25 mM detection limit and 0.25-2.5mM linear dynamic range. Storage stability of the MIP membranes was estimated as at least 1 year at room temperature. As compared to the traditional methods of creatinine detection the developed test-system is characterized by simplicity of operation, small size and low cost. PMID:23498699

Sergeyeva, T A; Gorbach, L A; Piletska, E V; Piletsky, S A; Brovko, O O; Honcharova, L A; Lutsyk, O D; Sergeeva, L M; Zinchenko, O A; El'skaya, A V

2013-04-01

54

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 0.5nM 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

55

Colorimetric detection of uranium(VI) on building surfaces after enrichment by solid phase extraction.  

PubMed

A method for detecting and quantifying uranium(VI) levels on building materials that include concrete, Plexiglas, glass and steel surfaces is presented. Uranium(VI) was extracted from building material surfaces using a pH 2.2 buffer rinse and, subsequently complexed by an organic chelating agent, arsenazo III. The application of a uranium-chelating molecule, arsenazo III, allows for concentration enhancement using C(18) solid phase extraction and colorimetric detection of the uranium complex using ultraviolet-visible spectroscopy at 654nm. The method has a detection limit (based on 3sigma) of 40ng/L (5ng/cm(2)) and an overall extraction efficiency greater than 80% for each surface type (concrete, Plexiglas, glass, steel). Methods to prevent interference by metal ions commonly found on building materials are discussed. PMID:18970078

Greene, Philip A; Copper, Christine L; Berv, David E; Ramsey, Jeremy D; Collins, Greg E

2005-05-15

56

Colorimetric detection of dichlorvos using polydiacetylene vesicles with acetylcholinesterase and cationic surfactants.  

PubMed

Widespread use of dichlorvos in agriculture has posed serious concern for food and water contamination. A new colorimetric method for the detection of dichlorvos based on polydiacethylene and acetylcholinesterase inhibition is developed. The blue-to-red color transition of poly(10,12-pentacosadynoic acid) vesicles can be induced by myristoylcholine which is enzymatically hydrolyzed by acetylcholinesterase to myristic acid and choline to prevent the color transition. In the presence of dichlorvos, the hydrolytic activity of the enzyme is inhibited that the blue-to-red color transition is restored with a linear correlation to the dichlorvos concentration. Using UV-vis absorption spectrometer, the limit of dichlorvos detection is 6.7ppb. A naked eye detection of 50ppb dichlorvos is achievable by using dimiristoylphosphatidylcholine to the diacetylene mixed lipid vesicles. PMID:24973536

Pimsen, Rungnapa; Khumsri, Akachai; Wacharasindhu, Sumrit; Tumcharern, Gamolwan; Sukwattanasinitt, Mongkol

2014-12-15

57

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

58

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.

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

2012-01-01

59

Antibody modified gold nanoparticles for fast and selective, colorimetric t7 bacteriophage detection.  

PubMed

Herein, we report a colorimetric immunosensor for T7 bacteriophage based on gold nanoparticles modified with covalently bonded anti-T7 antibodies. The new immunosensor allows for a fast, simple, and selective detection of T7 virus. T7 virions form immunological complexes with the antibody modified gold nanoparticles which causes them to aggregate. The aggregation can be observed with the naked eye as a color change from red to purple, as well as with a UV-vis spectrophotometer. The aggregate formation was confirmed with SEM imaging. Sensor selectivity against the M13 bacteriophage was demonstrated. The limit of detection (LOD) is 1.08 × 10(10) PFU/mL (18 pM) T7. The new method was compared with a traditional plaque test. In contrast to biological tests the colorimetric method allows for detection of all T7 phages, not only those biologically active. This includes phage ghosts and fragments of virions. T7 virus has been chosen as a model organism for adenoviruses. The described method has several advantages over the traditional ones. It is much faster than a standard plaque test. It is more robust since no bacteria-virus interactions are utilized in the detection process. Since antibodies are available for a large variety of pathogenic viruses, the described concept is very flexible and can be adapted to detect many different viruses, not only bacteriophages. Contrary to the classical immunoassays, it is a one-step detection method, and no additional amplification, e.g., enzymatic, is needed to read the result. PMID:24679221

Lesniewski, Adam; Los, Marcin; Jonsson-Niedzió?ka, Martin; Krajewska, Anna; Szot, Katarzyna; Los, Joanna M; Niedziolka-Jonsson, Joanna

2014-04-16

60

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

61

A colorimetric assay optimization for high-throughput screening of dihydroorotase by detecting ureido groups.  

PubMed

Dihydroorotase (DHOase) is the third enzyme in the de novo pyrimidine biosynthesis pathway and is a potential new antibacterial drug target. No target-based high-throughput screening (HTS) assay for this enzyme has been reported to date. Here, we optimized two colorimetric-based enzymatic assays that detect the ureido moiety of the DHOase substrate, carbamyl-aspartate (Ca-asp). Each assay was developed in a 40-?l assay volume using 384-well plates with a different color mix, diacetylmonoxime (DAMO)-thiosemicarbazide (TSC) or DAMO-antipyrine. The sensitivity and color interference of both color mixes were compared in the presence of common HTS buffer additives, including dimethyl sulfoxide, reducing agents, detergents, and bovine serum albumin. DAMO-TSC (Z'-factors 0.7-0.8) was determined to be superior to DAMO-antipyrine (Z'-factors 0.5-0.6) with significantly less variability within replicates. An HTS pilot screening with 29,552 compounds from four structurally diverse libraries confirmed the quality of our newly optimized colorimetric assay with DAMO-TSC. This robust method has no heating requirement, which was the main obstacle to applying previous assays to HTS. More important, this well-optimized HTS assay for DHOase, the first of its kind, should make it possible to screen large-scale compound libraries to develop new inhibitors against any enzymes that produce ureido functional groups. PMID:23769705

Rice, Amy J; Truong, Lena; Johnson, Michael E; Lee, Hyun

2013-10-01

62

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

63

"Naked-eye" colorimetric and "turn-on" fluorometric chemosensors for reversible Hg2+ detection.  

PubMed

Two new Hg(2+)-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 Hg(2+), 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 Cu(2+), Ag(+), Pb(2+), Ca(2+), Cd(2+), Co(2+), Fe(2+), Mn(2+), Na(+), Ni(2+), K(+), Ba(2+), Li(+) and Zn(2+), with a low detection limit of 1.7 ppb toward Hg(2+). PMID:24161855

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

2014-01-24

64

Colorimetric detection of melamine in milk by citrate-stabilized gold nanoparticles.  

PubMed

Here, we report a simple and sensitive colorimetric method for detection of melamine in milk using gold nanoparticles (AuNPs). AuNPs of 21-nm size were synthesized by the citrate reduction method. The method is based on the principle that the melamine causes the aggregation of AuNPs and, hence, the wine red color of AuNPs changes to blue or purple. This change in color can be visualized with the naked eye or an ultraviolet-visible (UV-Vis) spectrometer. Under optimized conditions, AuNPs are highly specific for melamine and can detect melamine down to a concentration of 0.05 mg L(-1). PMID:24727351

Kumar, Naveen; Seth, Raman; Kumar, Harish

2014-07-01

65

New colorimetric screening assays for the directed evolution of fungal laccases to improve the conversion of plant biomass  

PubMed Central

Background Fungal laccases are multicopper oxidases with huge applicability in different sectors. Here, we describe the development of a set of high-throughput colorimetric assays for screening laccase libraries in directed evolution studies. Results Firstly, we designed three colorimetric assays based on the oxidation of sinapic acid, acetosyringone and syringaldehyde with ?max of 512, 520 and 370 nm, respectively. These syringyl-type phenolic compounds are released during the degradation of lignocellulose and can act as laccase redox mediators. The oxidation of the three compounds by low and high-redox potential laccases evolved in Saccharomyces cerevisiae produced quantifiable and linear responses, with detection limits around 1 mU/mL and CV values below 16%. The phenolic substrates were also suitable for pre-screening mutant libraries on solid phase format. Intense colored-halos were developed around the yeast colonies secreting laccase. Furthermore, the oxidation of violuric acid to its iminoxyl radical (?max of 515 nm and CV below 15%) was devised as reporter assay for laccase redox potential during the screening of mutant libraries from high-redox potential laccases. Finally, we developed three dye-decolorizing assays based on the enzymatic oxidation of Methyl Orange (470 nm), Evans Blue (605 nm) and Remazol Brilliant Blue (640 nm) giving up to 40% decolorization yields and CV values below 18%. The assays were reliable for direct measurement of laccase activity or to indirectly explore the oxidation of mediators that do not render colored products (but promote dye decolorization). Every single assay reported in this work was tested by exploring mutant libraries created by error prone PCR of fungal laccases secreted by yeast. Conclusions The high-throughput screening methods reported in this work could be useful for engineering laccases for different purposes. The assays based on the oxidation of syringyl-compounds might be valuable tools for tailoring laccases precisely enhanced to aid biomass conversion processes. The violuric assay might be useful to preserve the redox potential of laccase whilst evolving towards new functions. The dye-decolorizing assays are useful for engineering ad hoc laccases for detoxification of textile wastewaters, or as indirect assays to explore laccase activity on other natural mediators.

2013-01-01

66

On-chip colorimetric detection of Cu2+ ions via density-controlled plasmonic core-satellites nanoassembly.  

PubMed

We report on an on-chip colorimetric method for the detection and analysis of Cu(2+) ions via the targeted assembly of plasmonic silver nanoparticles (2.6 nm satellites) on density-controlled plasmonic gold nanoparticles (50 nm cores) on a glass substrate. Without any ligand modification of the nanoparticles, by directly using an intrinsic moiety (carboxylate ion, COO(-)) surrounded with nanoparticles, the method showed a high selectivity for Cu(2+), resulting in a nearly 2 times greater optical response compared to those of other metal ions via the targeted core-satellites assembly. By modulating the surface chemistry, it was possible to control the density of core gold nanoparticles on the surface, thus permitting easy tuning of the optical responses induced by plasmon coupling generated between each core-satellites nanostructure. Using chips with a controlled optimal core density, we observed the remarkable scattering color changes of the chips from green to yellow and finally to orange with the increase of Cu(2+) concentration. The detection limits of the fabricated chips with controlled core densities (ca. 1821 and 3636 particles/100 ?m(2)) are 10 nM and 10 pM, respectively, which are quite tunable and below the level of 20 ?M (or 1.3 ppm) defined by the United States Environmental Protection Agency. The findings suggest that the method is a potentially promising protocol for detecting small molecules with target selectivity and the tunability of the detection limits by replacing with ligands and adjusting core densities. PMID:23865681

Song, Hyeon Don; Choi, Inhee; Lee, Suseung; Yang, Young In; Kang, Taewook; Yi, Jongheop

2013-08-20

67

Homogeneous detection of unamplified genomic DNA sequences based on colorimetric scatter of gold nanoparticle probes.  

PubMed

Nucleic acid diagnostics is dominated by fluorescence-based assays that use complex and expensive enzyme-based target or signal-amplification procedures. Many clinical diagnostic applications will require simpler, inexpensive assays that can be done in a screening mode. We have developed a 'spot-and-read' colorimetric detection method for identifying nucleic acid sequences based on the distance-dependent optical properties of gold nanoparticles. In this assay, nucleic acid targets are recognized by DNA-modified gold probes, which undergo a color change that is visually detectable when the solutions are spotted onto an illuminated glass waveguide. This scatter-based method enables detection of zeptomole quantities of nucleic acid targets without target or signal amplification when coupled to an improved hybridization method that facilitates probe-target binding in a homogeneous format. In comparison to a previously reported absorbance-based method, this method increases detection sensitivity by over four orders of magnitude. We have applied this method to the rapid detection of mecA in methicillin-resistant Staphylococcus aureus genomic DNA samples. PMID:15170215

Storhoff, James J; Lucas, Adam D; Garimella, Viswanadham; Bao, Y Paul; Müller, Uwe R

2004-07-01

68

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

69

Novel core etching technique of gold nanoparticles for colorimetric dopamine detection.  

PubMed

This study develops a novel and high performance colorimetric probe for dopamine (DA) detection. Aqueous-phase gold nanoparticles (AuNPs) extracted with 4-(dimethylamino)pyridine (DMAP) from toluene solvent are used as the reaction probes. The original AuNPs of diameter around 13 nm separate into 2-5 nm sizes when dopamine (DA) is added, resulting in the color change of the AuNP solution from red to blackish green. Transmission electron microscopy (TEM) observations and dynamic light scattering (DLS) tests show that the AuNPs break into their smaller sizes right after addition of DA. The results confirm that the DMAP capped AuNPs are etched by the DA molecules due to the strong affinity between DA and AuNPs, thus causing a blue shift in the absorption spectrum. The concentration of DA is quantitatively monitored by using a UV-Vis spectrometer with a limit of detection (LOD) as low as 5 nM. In addition, the results also show that the methods developed appear to have no significant problems in detecting DA in the sample even with the presence of (10 mM) common interferents such as ascorbic acid (AA), homovanillic acid (HVA), catechol (CA) and glutathione (GSH). The developed AuNP etching protocol for dopamine detection provides a novel and versatile approach for rapid biosensing applications. PMID:23016153

Lee, Ho-Cheng; Chen, Tzu-Heng; Tseng, Wei-Lung; Lin, Che-Hsin

2012-11-21

70

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

71

ampliPHOX Colorimetric Detection on a DNA Microarray for Influenza  

PubMed Central

DNA microarrays have emerged as a powerful tool for pathogen detection.1-5 For instance, many examples of the ability to type and subtype influenza virus have been demonstrated.6-11 The identification and subtyping of influenza on DNA microarrays has applications in both public health and the clinic for early detection, rapid intervention, and minimizing the impact of an influenza pandemic. Traditional fluorescence is currently the most commonly used microarray detection method. However, as microarray technology progresses towards clinical use,1 replacing expensive instrumentation with low cost detection technology exhibiting similar performance characteristics to fluorescence will make microarray assays more attractive and cost-effective. The ampliPHOX colorimetric detection technology is intended for research applications, and has a limit of detection within one order of magnitude of traditional fluorescence11, with a main advantage being an approximate ten-fold lower instrument cost compared to the confocal microarray scanners required for fluorescence microarray detection. Another advantage is the compact size of the instrument which allows for portability and flexibility, unlike traditional fluorescence instruments. Because the polymerization technology is not as inherently linear as fluorescence detection, however, it is best suited for lower density microarray applications in which a yes/no answer for the presence of a certain sequence is desired, such as for pathogen detection arrays. Currently the maximum spot density compatible with ampliPHOX detection is ˜1800 spots/array. Because of the spot density limitations, higher density microarrays are not suitable for ampliPHOX detection. Here, we present ampliPHOX colorimetric detection technology as a method of signal amplification on a low density microarray developed for the detection and characterization of influenza viruses (FluChip). Although this protocol uses the FluChip (a DNA microarray) as one specific application of ampliPHOX detection, any microarray incorporating biotinylated target can be labeled and detected in a similar manner. The microarray design and biotinylation of the target to be captured are the responsibility of the user. Once the biotinylated target has been captured on the array, ampliPHOX detection can be performed by first tagging the array with a streptavidin-label conjugate (ampliTAG). Upon light exposure using the ampliPHOX Reader instrument, polymerization of a monomer solution (ampliPHY) occurs only in regions containing ampliTAG-labeled targets. The polymer formed can be subsequently stained with a non-toxic solution to improve visual contrast, followed by imaging and analysis using a simple software package (ampliVIEW). The entire FluChip assay from un-extracted sample to result can be performed in about 6 hours, and the ampliPHOX detection steps described above can be completed in about 30 min.

Moulton, Kevin R.; Taylor, Amber W.; Rowlen, Kathy L.; Dawson, Erica D.

2011-01-01

72

Colorimetric Paper-based Detection of Escherichia coli, Salmonella spp., and Listeria monocytogenes from Large Volumes of Agricultural Water.  

PubMed

This protocol describes rapid colorimetric detection of Escherichia coli, Salmonella spp., and Listeria monocytogenes from large volumes (10 L) of agricultural waters. Here, water is filtered through sterile Modified Moore Swabs (MMS), which consist of a simple gauze filter enclosed in a plastic cartridge, to concentrate bacteria. Following filtration, non-selective or selective enrichments for the target bacteria are performed in the MMS. For colorimetric detection of the target bacteria, the enrichments are then assayed using paper-based analytical devices (µPADs) embedded with bacteria-indicative substrates. Each substrate reacts with target-indicative bacterial enzymes, generating colored products that can be detected visually (qualitative detection) on the µPAD. Alternatively, digital images of the reacted µPADs can be generated with common scanning or photographic devices and analyzed using ImageJ software, allowing for more objective and standardized interpretation of results. Although the biochemical screening procedures are designed to identify the aforementioned bacterial pathogens, in some cases enzymes produced by background microbiota or the degradation of the colorimetric substrates may produce a false positive. Therefore, confirmation using a more discriminatory diagnostic is needed. Nonetheless, this bacterial concentration and detection platform is inexpensive, sensitive (0.1 CFU/ml detection limit), easy to perform, and rapid (concentration, enrichment, and detection are performed within approximately 24 hr), justifying its use as an initial screening method for the microbiological quality of agricultural water. PMID:24962090

Bisha, Bledar; Adkins, Jaclyn A; Jokerst, Jana C; Chandler, Jeffrey C; Pérez-Méndez, Alma; Coleman, Shannon M; Sbodio, Adrian O; Suslow, Trevor V; Danyluk, Michelle D; Henry, Charles S; Goodridge, Lawrence D

2014-01-01

73

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

74

Colorimetric detection of copper in water using a Schiff base derivative  

NASA Astrophysics Data System (ADS)

Organic molecular sensors have the advantage of being used through an easy, fast, economical and reliable optical method for detecting toxic metal ions in our environment. In this work, we present a simple but highly specific organic ligand compound 5-Chloro-2-((E)-((E)-3-(4-(dimethylamino)phenyl)allylidene)amino)phenol (L1) that acts as a colorimetric sensor for ions in a mixture of acetonitrile/water (ratio 10:1, v:v). Binding interaction between L1 and various metal-ions has been established by ultraviolet-visible spectroscopic measurements that indicate favorable coordination of the ligand with selective metal ions, particularly, with copper. These results showed that the electronic transition band shape of L1 change after binding with copper in aqueous solution. L1 exhibited binding-induced color changes from yellow to pink one detected by the naked eye. This new sensor presented 2.5 × 10-6 M as limit detection, even under the presence of other metal ions.

Peralta Domínguez, D.; Ramos-Ortiz, G.; Maldonado, J. L.; Rodriguez, M.; Meneses-Nava, M. A.; Barbosa-Garcia, O.; Santillan, R.; Farfán, N.

2013-09-01

75

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

76

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

77

Colorimetric detection of Al3+ ions using triazole-ether functionalized gold nanoparticles.  

PubMed

A sensitive, selective colorimetric Al(3+) detection method has been developed by using triazole-ether functionalized gold nanoparticles (TTP-AuNPs). Gold nanoparticles were prepared by reducing HAuCl4 with sodium borohydride in the presence of 5-(1,2-dithiolan-3-yl)-N-(prop-2-yn-1-yl)pentanamide (TP). The azide part of 2-[2-(2-azidoethoxy)ethoxy]ethanol and the acetylene part of TP were combined to form a triazole structure through a click reaction. Aggregation of TTP-AuNPs was induced immediately in the presence of Al(3+) ions, yielding a color change from red to blue. This Al(3+)-induced aggregation of TTP-AuNPs was monitored first with the naked eye and then UV-vis spectroscopy with a detection limit of 18.0 nM. The TTP-AuNPs showed excellent selectivity for Al(3+), compared to other metal ions (Ag(+), Ca(2+), Cd(2+), Co(2+), Cu(2+), Cr(3+), Fe(2+), Fe(3+), Hg(2+), Mg(2+), Mn(2+), Ni(2+), Pb(2+), and Zn(2+)). In addition, TTP-AuNPs were used to detect Al(3+) in sea water samples, with low interference. PMID:24209312

Chen, Yu-Ching; Lee, I-Lin; Sung, Yi-Ming; Wu, Shu-Pao

2013-12-15

78

Identification of Escherichia coli O157 by Using a Novel Colorimetric Detection Method with DNA Microarrays  

PubMed Central

Abstract Shiga toxin–producing Escherichia coli O157 is a leading cause of foodborne illness worldwide. To evaluate better methods to rapidly detect and genotype E. coli O157 strains, the present study evaluated the use of ampliPHOX, a novel colorimetric detection method based on photopolymerization, for pathogen identification with DNA microarrays. A low-density DNA oligonucleotide microarray was designed to target stx1 and stx2 genes encoding Shiga toxin production, the eae gene coding for adherence membrane protein, and the per gene encoding the O157-antigen perosamine synthetase. Results from the validation experiments demonstrated that the use of ampliPHOX allowed the accurate genotyping of the tested E. coli strains, and positive hybridization signals were observed for only probes targeting virulence genes present in the reference strains. Quantification showed that the average signal-to-noise ratio values ranged from 47.73?±?7.12 to 76.71?±?8.33, whereas average signal-to-noise ratio values below 2.5 were determined for probes where no polymer was formed due to lack of specific hybridization. Sensitivity tests demonstrated that the sensitivity threshold for E. coli O157 detection was 100–1000 CFU/mL. Thus, the use of DNA microarrays in combination with photopolymerization allowed the rapid and accurate genotyping of E. coli O157 strains.

Swimley, Michelle S.; Taylor, Amber W.; Dawson, Erica D.

2011-01-01

79

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

80

Detection and comparison of protein-DNA interactions using DNA-BINDTM plate and horseradish peroxidase-based colorimetric assay  

PubMed Central

We describe a procedure for detection and comparison of protein-DNA interactions using DNA-BINDTM plate and horseradish peroxidase (HRP)-based colorimetric assay. Amino-modified oligonucleotide was covalently immobilized on the surface of the DNA-BINDTM plate. After the complementary oligonucleotide was annealed, the plate was incubated with protein to allow sequence-specific DNA-binding. Primary antibody and HRP-labeled secondary antibody were then employed, and colorimetric assay was conducted before the absorbance was read. This method is sensitive, specific and high-throughput, which has been applied not only in the detection of protein-DNA interaction, but also in quantitative comparison of DNA-binding capabilities among wild type and mutant proteins.

Liu, Bin; Qin, Yu; Wang, Jinzhong; Wang, Ying

2011-01-01

81

Visual and colorimetric detection of Hg(2+) by cloud point extraction with functionalized gold nanoparticles as a probe.  

PubMed

Association with Hg(2+) enhances the hydrophobicity and triggers the cloud point extraction of approximately 4 nm-diameter gold nanoparticle probes functionalized with mercaptopropionic acid and homocystine, which results in the color change of the TX-114-rich phase from colorless to red, and therefore provides a novel approach for visual and colorimetric detection of Hg(2+) with ultrahigh sensitivity and selectivity. PMID:19904384

Tan, Zhi-qiang; Liu, Jing-fu; Liu, Rui; Yin, Yong-guang; Jiang, Gui-bin

2009-12-01

82

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

Microsoft Academic Search

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.,

Jiefang Sun; Lei Guo; Yi Bao; Jianwei Xie

2011-01-01

83

Novel application of CoFe layered double hydroxide nanoplates for colorimetric detection of H(2)O(2) and glucose.  

PubMed

The present communication demonstrates the proof of concept of using CoFe layered double hydroxide (CoFe-LDHs) nanoplates as an effective peroxidase mimetic to catalyze the oxidation of peroxidase substrate 3,3',5,5'-tetramethylbenzidine in the presence of H(2)O(2) to produce a blue solution. We further demonstrate successfully CoFe-LDHs nanoplate-based colorimetric assay to detect H(2)O(2) and glucose. PMID:22290215

Zhang, Yingwei; Tian, Jingqi; Liu, Sen; Wang, Lei; Qin, Xiaoyun; Lu, Wenbo; Chang, Guohui; Luo, Yonglan; Asiri, Abdullah M; Al-Youbi, Abdulrahman O; Sun, Xuping

2012-03-21

84

Optimization of the reactional medium and a food impact study for a colorimetric in situ Salmonella spp. detection method.  

PubMed

Foodborne pathogens are still a major concern for public health authorities. In this paper, we describe the optimization of a previously reported method which combines a highly specific capture of targeted food pathogens with an intracellular staining method. The reaction medium was optimized to simultaneously allow specific enrichment of Salmonella and maximize the staining of the target pathogen. This in situ colorimetric concept was evaluated with a broad range of food samples artificially contaminated with low levels of stressed Salmonella to mimic natural contamination conditions. This direct detection method compared favorably to a commercially available immunoassay system (Vidas® UP Salmonella), for cooked meat, dry milk powder and egg products. Globally 88% agreement was obtained between the two methods with a sensitivity of 80% and a specificity of 100% for the tested method. Main discordances were obtained with food matrices having high levels of competitive Gram negative microflora. These observations show that the design of an adapted culture medium is necessary to enhance the specific in situ capture and revelation system. PMID:24819412

Junillon, Thomas; Mosticon, David; Mallen, Benoît; Baril, Florent; Morand, Lucie; Michel, Déborah; Flandrois, Jean-Pierre

2014-07-01

85

A colorimetric aptasensor for the highly sensitive detection of 8-hydroxy-2'-deoxyguanosine based on G-quadruplex-hemin DNAzyme.  

PubMed

A highly sensitive, low-cost colorimetric aptasensor was developed for the determination of 8-hydroxy-2'-deoxyguanosine (8-OHdG) in human urine. The method is based on a conformational switching of the 8-OHdG aptamer to form a G-quadruplex structure in the presence of 8-OHdG. The resulting G-quadruplex assembles into a peroxidase-like DNAzyme with hemin, which effectively catalyzes the oxidation of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS(2-)) by H2O2 to ABTS(+), resulting in an increase in the absorption signal at 416nm along with a color change of the solution. The response signals linearly correlated with the concentration of 8-OHdG, ranging from 466pM to 247nM with a detection limit of 141pM. The relative standard deviation and the recovery were 1.97-3.47% (n=11) and 98.8-100.2%, respectively. The proposed method avoids the label and derivatization steps in common methods and allows direct analysis of the samples by the naked eye without costly instruments, which is reliable, inexpensive, and sensitive. PMID:24811738

Liu, Hui; Wang, Yong-Sheng; Wang, Jia-Cheng; Xue, Jin-Hua; Zhou, Bin; Zhao, Hui; Liu, Shan-Du; Tang, Xian; Chen, Si-Han; Li, Ming-Hui; Cao, Jin-Xiu

2014-08-01

86

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 Cu(2+). Addition of Cu(2+) to the solution of BMSRH results in a rapid color change from colorless to red together with an obvious new band appeared at 552nm in the UV-vis absorption spectra. This change is attributed to the spirocycle form of BMSRH opened via coordination with Cu(2+) in a 1:1 stoichiometry and their association constant is determined as 3.2×10(4)Lmol(-1). Experimental results indicate that the BMSRH can provide a rapid, selective and sensitive response to Cu(2+) with a linear dynamic range 0.667-240?mol/L. Common interferent ions do not show any interference on the Cu(2+) determination. It is anticipated that BMSRH can be a good candidate probe and has potential application for Cu(2+) 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

87

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

NASA Astrophysics Data System (ADS)

In the framework of the research project 'Xsense' at the Technical University of Denmark (DTU) we are developing a simple colorimetric sensor array which can be useful in detection of explosives like DNT and TNT, and identification of volatile organic compounds in the presence of water vapor in air. The technology is based on an array of chemo-responsive dyes immobilized on a solid support. Upon exposure to the analyte in suspicion the dye array changes color. Each chosen dye reacts chemo selectively with analytes of interest. A change in a color signature indicates the presence of unknown explosives and volatile organic compounds (VOCs). We are working towards the selection of dyes that undergo color changes in the presence of explosives and VOCs, as well as the development of an immobilization method for the molecules. Digital imaging of the dye array before and after exposure to the analytes creates a color difference map which gives a unique fingerprint for each explosive and volatile organic compound. Such sensing technology can be used to screen for relevant explosives in a complex background as well as to distinguish mixtures of volatile organic compounds distributed in gas phase. This sensor array is inexpensive, and can potentially be produced as single use disposable.

Kostesha, N. V.; Alstrøm, T. S.; Johnsen, C.; Nilesen, K. A.; Jeppesen, J. O.; Larsen, J.; Jakobsen, M. H.; Boisen, A.

2010-04-01

88

Colorimetric High-Throughput Screen for Detection of Heme Crystallization Inhibitors?  

PubMed Central

Malaria infects 500 million people annually, a number that is likely to rise as drug resistance to currently used antimalarials increases. During its intraerythrocytic stage, the causative parasite, Plasmodium falciparum, metabolizes hemoglobin and releases toxic heme, which is neutralized by a parasite-specific crystallization mechanism to form hemozoin. Evidence suggests that chloroquine, the most successful antimalarial agent in history, acts by disrupting the formation of hemozoin. Here we describe the development of a 384-well microtiter plate screen to detect small molecules that can also disrupt heme crystallization. This assay, which is based on a colorimetric assay developed by Ncokazi and Egan (K. K. Ncokazi and T. J. Egan, Anal. Biochem. 338:306-319, 2005), requires no parasites or parasite-derived reagents and no radioactive materials and is suitable for a high-throughput screening platform. The assay's reproducibility and large dynamic range are reflected by a Z factor of 0.74. A pilot screen of 16,000 small molecules belonging to diverse structural classes was conducted. The results of the target-based assay were compared with a whole-parasite viability assay of the same small molecules to identify small molecules active in both assays.

Rush, Margaret A.; Baniecki, Mary Lynn; Mazitschek, Ralph; Cortese, Joseph F.; Wiegand, Roger; Clardy, Jon; Wirth, Dyann F.

2009-01-01

89

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

90

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

91

Direct detection of WIMPs  

NASA Astrophysics Data System (ADS)

A generic weakly interacting massive particle (WIMP) is one of the most attractive candidates to account for the cold dark matter in our Universe, since it would be thermally produced with the correct abundance to account for the observed dark matter density. WIMPs can be searched for directly through their elastic scattering with a target material, and a variety of experiments are currently operating or planned with this aim. In these notes we overview the theoretical calculation of the direct detection rate of WIMPs as well as the different detection signals. We discuss the various ingredients (from particle physics and astrophysics) that enter the calculation and review the theoretical predictions for the direct detection of WIMPs in particle physics models.

Cerdeño, D. G.; Green, A. M.

92

A methylation-blocked cascade amplification strategy for label-free colorimetric detection of DNA methyltransferase activity.  

PubMed

DNA methyltransferase (MTase), catalyzing DNA methylation in both eukaryotes and prokaryotes, is closely related with cancer and bacterial diseases. Although there are various methods focusing on DNA MTase detection, most of them share common defects such as complicated setup, laborious operation and requirement of expensive analytical instruments. In this work, a simple strategy based on methylation-blocked cascade amplification is developed for label-free colorimetric assay of MTase activity. When DNA adenine methylation (Dam) MTase is introduced, the hairpin probe is methylated. This blocks the amplified generation of G-riched DNAzyme by nicking endonuclease and DNA polymerase, and inhibits the DNAzyme-catalyzed colorimetric reaction. Contrarily, an effective colorimetric reaction is initiated and high color signal is clearly observed by the naked eye in the absence of Dam MTase. A satisfying sensitivity and high selectivity are readily achieved within a short assay time of 77 min, which are superior to those of some existing approaches. Additionally, the application of the sensing system in human serum is successfully verified with good recovery and reproducibility, indicating great potential for the practicality in high concentrations of interfering species. By using several anticancer and antimicrobial drugs as model, the inhibition of Dam MTase is well investigated. Therefore, the proposed method is not only promising and convenient in visualized analysis of MTase, but also useful for further application in fundamental biological research, early clinical diagnosis and drug discovery. PMID:24333567

Zhao, Yongxi; Chen, Feng; Lin, Manli; Fan, Chunhai

2014-04-15

93

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

94

Colorimetric detection of mercury ion (Hg 2+) based on DNA oligonucleotides and unmodified gold nanoparticles sensing system with a tunable detection range  

Microsoft Academic Search

Here, we report a simple and sensitive colorimetric detection method for Hg2+ ions with a tunable detection range based on DNA oligonucleotides and unmodified gold nanoparticles (DNA\\/AuNPs) sensing system. Complementary DNA strands with T–T mismatches could effectively protect AuNPs from salt-induced aggregation. While in the presence of Hg2+ ions T–Hg2+–T coordination chemistry leads to the formation of DNA duplexes, and

Xiaowen Xu; Juan Wang; Kui Jiao; Xiurong Yang

2009-01-01

95

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

96

Comparison of an electrochemiluminescence assay in plate format over a colorimetric ELISA, for the detection of ricin B chain (RCA-B).  

PubMed

An electrochemiluminescence (ECL) assay for the detection of the B chain of ricin (RCA-B) in a 96-well plate format was developed in parallel with a colorimetric ELISA utilizing the same pair of antibodies. Sensitivity results were interpreted with the ANOVA and Tukey statistical tests, allowing a direct comparison between the two technologies, that can probably be extended to other protein antigens such as toxins. Reproducibility, repeatability and rapidity of the two techniques were also compared. The ELISA assay utilized an alkaline phosphatase conjugate for signal generation. After optimization, its limit of detection was 400 pg of RCA-B per ml buffer, with an intra-day standard deviation (SD) of 2.2% of the mean and an inter-day SD of 5.1%. The ECL assay utilized ruthenylated antibodies for detection. The ECL measurement was carried out using a Sector PR 400 plate reader. After optimization, its limit of detection was 50 pg of RCA-B per ml buffer, with an intra-day SD of 4.1% of the mean and an inter-day SD of 4.3%. Starting from a pre-coated plate, the ELISA assay was completed in 7 h and the ECL assay took 2.5 h. While reproducibility and repeatability of the two assays were equivalent, this ECL assay in plate format had an 8-fold better sensitivity for RCA-B detection than the colorimetric ELISA in buffer and in various matrices. The ECL assay was also three times faster, and retained the robustness and convenience of the 96-well plate format. PMID:17854822

Guglielmo-Viret, V; Thullier, P

2007-12-01

97

Solid-phase colorimetric sensor based on gold nanoparticle-loaded polymer brushes: lead detection as a case study.  

PubMed

We introduce a novel solid-phase colorimetric sensor facilely fabricated by loading unmodified gold nanoparticles into poly(oligo(ethylene glycol)methacrylate) (POEGMA) brushes grown on glass. Our work reports the first synergistic combination of metallic nanoparticles acting as a colorimetric sensing module with a nonfouling polymer matrix acting both as a nonrigid scaffold and a screen to reduce interference from nontarget molecules. In addition, as the nanocomposite is formed on a transparent substrate, solid-phase detection can be performed in the same manner as in the solution-phase. We demonstrate the use of this unique platform for label-free lead detection based on the release of gold nanoparticles from the polymer brush upon exposure to lead ions. An ultralow limit-of-detection of 25 pM (S/N = 3) and a dynamic range of 100 pM to 100 nM (R(2) = 0.987) are achieved. Furthermore, the detection is up to 1000-fold more selective to lead over other common heavy metal ions. PMID:23509859

Ferhan, Abdul Rahim; Guo, Longhua; Zhou, Xiaodong; Chen, Peng; Hong, Seungpyo; Kim, Dong-Hwan

2013-04-16

98

Direct Quantification of Carotenoids in Low Fat Baby Foods Via Laser Photoacoustics and Colorimetric Index {{\\varvec{a}}} *  

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 a * 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 a *, R2 = 0.9925 and R2 = 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.

2014-02-01

99

Lab-on-paper with dual electrochemical/colorimetric detection for simultaneous determination of gold and iron.  

PubMed

A novel lab-on-paper device combining electrochemical and colorimetric detection for the rapid screening of Au(III) in the presence of a common interference, Fe(III), in industrial waste solutions is presented here. With dilute aqua regia (0.1 M HCl + 0.05 M HNO(3)) as the supporting electrolyte, square wave voltammetry on paper provided a well-defined reduction peak for Au(III) at approximately 287 +/- 12 mV vs Ag/AgCl. Under the optimized working conditions, the calibration curve showed good linearity in the concentration range of 1-200 ppm of Au(III) with a correlation coefficient of 0.997. The limit of detection (LOD) of the proposed method is 1 ppm. Interferences from various cations were also studied. Fe(III) is the only metal that affects the electrochemical determination of Au(III) when present above a 2.5-fold excess concentration of that of the Au(III). To overcome this limitation, a colorimetric method was used to simultaneously detect Fe(III) as a screening tool. The procedure was then successfully applied to determine Au(III) in gold-refining waste solutions. The results are in agreement with those obtained from inductively coupled plasma-atomic emission spectrometry (ICP-AES). PMID:20121066

Apilux, Amara; Dungchai, Wijitar; Siangproh, Weena; Praphairaksit, Narong; Henry, Charles S; Chailapakul, Orawon

2010-03-01

100

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

101

Colorimetric Nucleic Acid Testing Assay for RNA Virus Detection Based on Circle-to-Circle Amplification of Padlock Probes?  

PubMed Central

We developed a molecular diagnostic method for detection of RNA virus based on padlock probes and colorimetric readout. The feasibility of our approach was demonstrated by using detection of Crimean-Congo hemorrhagic fever (CCHF) virus as a model. Compared with conventional PCR-based methods, our approach does not require advanced equipment, involves easier assay design, and has a sensitivity of 103 viral copies/ml. By using a cocktail of padlock probes, synthetic templates representing different viral strain variants could be detected. We analyzed 34 CCHF patient samples, and all patients were correctly diagnosed when the results were compared to those of the current real-time PCR method. This is the first time that highly specific padlock probes have been applied to detection of a highly variable target sequence typical of RNA viruses.

Ke, Rongqin; Zorzet, Anna; Goransson, Jenny; Lindegren, Gunnel; Sharifi-Mood, Batool; Chinikar, Sadegh; Mardani, Masoud; Mirazimi, Ali; Nilsson, Mats

2011-01-01

102

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

103

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

104

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.

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

2014-01-01

105

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

106

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

107

A highly selective colorimetric chemodosimeter for fast and quantitative detection of hydrogen sulfide.  

PubMed

Based on the fact that hydrogen sulfide (H(2)S) possesses the smallest steric hindrance among thiols and the SH(-) group adds faster to an electron-poor C=C double bond, we designed and synthesized a tricyanoethylene-derived colorimetric chemodosimeter 1 for the fast and highly selective assay of H(2)S. Chemodosimeter 1 exhibited excellent water-solubility due to the introduction of two hydrophilic hydroxyl groups. Upon the addition of Na(2)S, chemodosimeter 1 showed a fast (complete within 400 s) and robust decrease of the absorption intensity (>97%), accompanied by a color change from red to colorless. Additionally, a linear relationship between absorption intensity and the added Na(2)S concentrations (0-130 ?M) was observed in aqueous buffer solution (pH 7.4, 20 mM PBS). Importantly, the proposed paradigm in this paper, adoption of the tricyanoethylene derivative as a recognition receptor to distinguish H(2)S from other thiols and analytes, provides a promising methodology for the design of colorimetric and fluorescent chemodosimeters for fast determination of H(2)S. PMID:23057070

Zhao, Yunzhou; Zhu, Xiaohe; Kan, He; Wang, Weizhang; Zhu, Baocun; Du, Bin; Zhang, Xiaoling

2012-12-01

108

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

109

A simple "clickable" biosensor for colorimetric detection of copper(II) ions based on unmodified gold nanoparticles.  

PubMed

A novel colorimetric copper(II) biosensor has been developed based on the high specificity of alkyne-azide click reaction to the catalysis of copper ions and unmodified gold nanoparticles (AuNPs) as the signal reporter. The clickable DNA probe consists of two parts: an azide group-modified double-stranded DNA (dsDNA) hybrid with an elongated tail and a short alkyne-modified single-stranded DNA (ssDNA). Because of low melting temperature of the short ssDNA, these two parts are separated in the absence of Cu(2+). Copper ion-induced azide-alkyne click ligation caused a structural change of probe from the separated form to entire dsDNA form. This structural change of probe can be monitored by the unmodified AuNPs via mediating their aggregation with a red-to-blue colorimetric read-out because of the differential ability of ssDNA and dsDNA to protect AuNPs against salt-induced aggregation. Under the optimum conditions, this biosensor can sensitively and specifically detect Cu(2+) with a low detection limit of 250 nM and a linear range of 0.5-10 ?M. The method is simple and economic without dual-labeling DNA and AuNPs modification. It is also highly selective for Cu(2+) in the presence of high concentrations of other environmentally relevant metal ions because of the great specificity of the copper-caused alkyne-azide click reaction, which potentially meets the requirement of the detection in real samples. PMID:23089325

Shen, Qinpeng; Li, Wenhua; Tang, Shiyun; Hu, Yufang; Nie, Zhou; Huang, Yan; Yao, Shouzhuo

2013-03-15

110

Adaptation of Ti(III)-NTA colorimetric assay for use in detecting microbial demethylation of lignin and lignin derived compounds in aerobic conditions.  

PubMed

An anaerobic colorimetric assay for quantifying microbial demethylation activity was adapted for aerobic use in studying lignin and lignin-derived compounds. Standard curves of 0-500?M pyrocatechol with and without 0.3% lignin demonstrated the use in either case. This method detects demethylation products up to 500?M without using additional dilutions. PMID:24681305

Gibson, A; Dekker, R F H; Malek, L

2014-06-01

111

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

112

Direct detection of unamplified genomic DNA based on photo-induced silver ion reduction by DNA molecules.  

PubMed

A label-free, colorimetric method has been developed for ultrasensitive detection of nucleic acids that is based on photoinduced silver ion (Ag(+)) reduction around DNA bases. The assay system is capable of directly detecting bacterial genomic DNA without the need for PCR amplification. PMID:23407668

Jung, Ye Lim; Jung, Cheulhee; Park, Jung Hun; Kim, Moon Il; Park, Hyun Gyu

2013-03-21

113

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

114

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 2h, 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 (5ngmL(-1)-200ngmL(-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

115

Sun Direction Detection System.  

National Technical Information Service (NTIS)

A sun sensor detection system is described which includes an illumination detector and a sun angle detector. The illumination detector provides a low resistance output whenever the sun is within a selected field of view and a high resistance output whenev...

L. F. Schmidt G. D. Pace

1975-01-01

116

Novel thieno-imidazole based probe for colorimetric detection of Hg2+ and fluorescence turn-on response of Zn2+.  

PubMed

Novel thieno-imidazole based polymer P showed both colorimetric and ratiometric detections of Hg(2+) as well as fluorometric detection of Zn(2+) via fluorescence turn-on response with augmented lifetime. Its model polymer M did not show any such sensing capability under similar conditions, which further confirmed the unique sensitivity of P toward Hg(2+) and Zn(2+) via the chelation of metal ions to both "S" and "N" heteroatoms. PMID:22571681

Satapathy, Rudrakanta; Wu, Yen-Hsing; Lin, Hong-Cheu

2012-05-18

117

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

PubMed

A colorimetric method that employed extraction of the macerated fruit, followed by a reaction with 2-thiobarbituric acid, was used to quantify potassium sorbate residues in citrus fruit. A recovery of more than 90% in oranges and lemons was obtained. Potassium sorbate residues determined by this method and a standard high-performance liquid chromatography (HPLC) method were similar. Residues were proportionate to the potassium sorbate concentration in the treatment solution. In oranges stored at 15 degrees C, following the potassium sorbate treatments, residues declined initially rapidly and later more slowly, until residues stopped declining after 6 days. A brief double-dip rinse in tap water applied immediately after immersion of lemons in a 2% (wt/vol) potassium sorbate removed more than 90% of the potassium sorbate residue. The influence of high-pressure water washing (HPWW) on potassium sorbate residues in potassium-sorbate-treated fruit was determined. Potassium sorbate residues were more effectively reduced by rinsing oranges than lemons. PMID:19334786

Montesinos-Herrero, Clara; Smilanick, Joseph L; Hurley, J Michael; Palou, Lluís

2009-05-13

118

Hydrogen-bonding-induced colorimetric detection of melamine by nonaggregation-based Au-NPs as a probe.  

PubMed

A colorimetric, label-free, and nonaggregation-based gold nanoparticles probe has been developed for the detection of melamine. Gold nanoparticles were generated using 3,5-dihydroxybenzoic acid as a reducer without adding gold nanoparticle seeds at room temperature. Upon the addition of melamine, the reducer 3,5-dihydroxybenzoic acid can interact with melamine through strong hydrogen-bonding interaction. Consequently, the formation of gold nanoparticles was interrupted by melamine since there was not enough reducer for the reduction of Au(3+) ion. And the color change from purple to yellowgreen with increasing melamine concentration was observed. The plasmon absorbance of the formed Au-NPs allows the quantitative detection of melamine. A sensitive linear correlation existed between the absorbance and the logarithm of melamine concentration ranging from 1x10(-9) M to 1x10(-5) M with a linear coefficiency of 0.993. The system has a high selectivity to melamine with a low detection limit of 8x10(-10) M. PMID:20510598

Cao, Qian; Zhao, Hong; He, Yujian; Li, Xiangjun; Zeng, Lixi; Ding, Nan; Wang, Jian; Yang, Jie; Wang, Guangwei

2010-08-15

119

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

120

Dark Matter (mostly Direct) Detection  

NASA Astrophysics Data System (ADS)

After briefly summarizing the motivations for the ?-CDM model, I will argue rather provocatively that the many candidates already reported by indirect detection experiments are a strong indication that it is nearly impossible to distinguish a WIMP annihilation signal from astrophysical background using the indirect detection method. This structural uncertainty argues strongly in favor of direct detection of WIMP interactions in the controlled environment of the laboratory and I will describe the main strategies developed to detect WIMPs using the direct detection technique in underground sites, protected from the cosmic-ray induced background. I will show that most of the present experimental efforts is now focused on three identification techniques of nuclear recoils, i.e. charge-phonon, light-phonon and charge-scintillation simultaneous detection. Finally, since direct detection has also its own candidate, I will comment on the DAMA annual modulation candidate, and on the lessons that can be learned from the long controversy over this result.

Chardin, G.

2010-06-01

121

Visual and highly sensitive detection of cancer cells by a colorimetric aptasensor based on cell-triggered cyclic enzymatic signal amplification.  

PubMed

Rapid and efficient detection of cancer cells at their earliest stages is one of the central challenges in cancer diagnostics. We developed a simple, cost-effective, and highly sensitive colorimetric method for visually detecting rare cancer cells based on cell-triggered cyclic enzymatic signal amplification (CTCESA). In the absence of target cells, hairpin aptamer probes (HAPs) and linker DNAs stably coexist in solution, and the linker DNA assembles DNA-AuNPs, producing a purple solution. In the presence of target cells, the specific binding of HAPs to the target cells triggers a conformational switch that results in linker DNA hybridization and cleavage by nicking endonuclease-strand scission cycles. Consequently, the cleaved fragments of linker DNA can no longer assemble into DNA-AuNPs, resulting in a red color. UV-vis spectrometry and photograph analyses demonstrated that this CTCESA-based method exhibited selective and sensitive colorimetric responses to the presence of target CCRF-CEM cells, which could be detected by the naked eye. The linear response for CCRF-CEM cells in a concentration range from 10(2) to 10(4) cells was obtained with a detection limit of 40 cells, which is approximately 20 times lower than the detection limit of normal AuNP-based methods without amplification. Given the high specificity and sensitivity of CTCESA, this colorimetric method provides a sensitive, label-free, and cost-effective approach for early cancer diagnosis and point-to-care applications. PMID:24819867

Zhang, Xianxia; Xiao, Kunyi; Cheng, Liwei; Chen, Hui; Liu, Baohong; Zhang, Song; Kong, Jilie

2014-06-01

122

Colorimetric detection of copper and efficient removal of heavy metal ions from water by diamine-functionalized SBA-15.  

PubMed

SBA-15 functionalized with N-[3-(trimethoxysilyl)propyl]ethylene-diamine (TPED) was synthesized and used for the colorimetric detection of Cu(2+) and removal of heavy metal ions in aqueous solutions. Compared to free SBA-15, the adsorption ability of diamine-functionalized SBA-15 (depicted as SBA-TPED) increased remarkably, the maximum adsorption capacity of SBA-TPED for Cu(2+), Pb(2+) and Zn(2+) was 27.22, 96.43 and 12.16 mg g(-1), respectively. Furthermore, SBA-TPED exhibits high selectivity for Cu(2+) with the relative selectivity coefficient of SBA-TPED for Cu(2+)/Pb(2+) being over 10 and for Cu(2+)/Zn(2+) being over 60. The naked-eye detection limit of SBA-TPED for Cu(2+) is 0.95 ppm, and the determination of Cu(2+) in real water samples also displays satisfactory results. Moreover, SBA-TPED possesses fast kinetics for removing Cu(2+) with a saturation time of less than 30 min, and can be regenerated by simple acid treatment. PMID:24745033

Wang, Zhuqing; Wang, Min; Wu, Genhua; Wu, Dayu; Wu, Aiguo

2014-05-13

123

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

PubMed

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 Fe?O? 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 (V(max)) 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. PMID:24322602

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

2014-01-16

124

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

125

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

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

2014-06-01

126

Sensitivity enhancement in the colorimetric detection of lead(II) ion using gallic acid–capped gold nanoparticles: Improving size distribution and minimizing interparticle repulsion  

Microsoft Academic Search

We have developed a colorimetric assay for the highly sensitive and selective detection of Pb2+ by narrowing the size distribution of gallic acid–capped gold nanoparticles (GA–AuNPs) and minimizing electrostatic repulsion between each GA–AuNP. We unveil that the particle size and size distribution of GA–AuNPs could be controlled by varying the pH of HAuCl4 with fixed concentrations of HAuCl4 and GA.

Kuan-Wei Huang; Cheng-Ju Yu; Wei-Lung Tseng

2010-01-01

127

Target recycling amplification for label-free and sensitive colorimetric detection of adenosine triphosphate based on un-modified aptamers and DNAzymes.  

PubMed

Based on target recycling amplification, the development of a new label-free, simple and sensitive colorimetric detection method for ATP by using un-modified aptamers and DNAzymes is described. The association of the model target molecules (ATP) with the corresponding aptamers of the dsDNA probes leads to the release of the G-quadruplex sequences. The ATP-bound aptamers can be further degraded by Exonuclease III to release ATP, which can again bind the aptamers of the dsDNA probes to initiate the target recycling amplification process. Due to this target recycling amplification, the amount of the released G-quadruplex sequences is significantly enhanced. Subsequently, these G-quadruplex sequences bind hemin to form numerous peroxidase mimicking DNAzymes, which cause substantially intensified color change of the probe solution for highly sensitive colorimetric detection of ATP down to the sub-nanomolar (0.33nM) level. Our method is highly selective toward ATP against other control molecules and can be performed in one single homogeneous solution, which makes our sensing approach hold great potential for sensitive colorimetric detection of other small molecules and proteins. PMID:24845818

Gong, Xue; Li, Jinfu; Zhou, Wenjiao; Xiang, Yun; Yuan, Ruo; Chai, Yaqin

2014-05-30

128

Colorimetric detection of the toxic dinoflagellate Alexandrium minutum using sandwich hybridization in a microtiter plate assay  

Microsoft Academic Search

Rapid and reliable detection of harmful algae in coastal areas and shellfish farms is an important requirement for monitoring programs. Molecular technologies are rapidly improving the detection of phytoplankton and their toxins. Assays are based on the discrimination of genetic differences in the species. A commercially available PCR ELISA Dig Detection Kit in a microtiter plate was adapted for the

Sonja Diercks; Linda K. Medlin; Katja Metfies

2008-01-01

129

BacT\\/Alert: anAutomated Colorimetric Microbial Detection System  

Microsoft Academic Search

BacT\\/Alert (Organon Teknika Corp., Durham, N.C.) isanautomated microbial detection system based on thecolorimetric detection ofC02produced bygrowing microorganisms. Results ofanevaluation ofthemedia, sensor, detection system, anddetection algorithm indicate thatthesystem reliably growsanddetects awide variety ofbacteria andfungi. Results ofalimited pilot clinical trial withaprototype research instrument indicate thatthesystem iscomparable totheradiometric BACTEC460system initsability togrowanddetect microorganisms inblood. Onthebasis ofthese initial findings, large-scale clinical trials comparing BacT\\/Alert withother

THURMAN C. THORPE; MICHAEL L. WILSON; JAMES E. TURNER; L. BARTH RELLER

1990-01-01

130

Catalytic formation of silver nanoparticles by bovine serum albumin protected-silver nanoclusters and its application for colorimetric detection of ascorbic acid  

NASA Astrophysics Data System (ADS)

We established a simple spectrophotometric and colorimetric method for detection of ascorbic acid based on the growth of silver nanoparticles in bovine serum albumin protected-silver nanoclusters (BSA-AgNCs) and Ag+ mixture. Due to the catalysis of BSA-AgNCs, ascorbic acid could reduce Ag+ to silver nanoparticles (NPs) at room temperature. The color of the mixture changed from colorless to yellow and a strong absorption band near 420 nm could be found in their absorption spectra owing to localized surface plasmon resonance (LSPR) of produced silver NPs. The absorbance changes at 420 nm had a good relationship with ascorbic acid concentration. Thus, we proposed a spectrophotometric and colorimetric method to determine ascorbic acid in concentration range from 2.0 to 50.0 ?M, with the corresponding limits of determination (3?) of 0.16 ?M.

Yang, Xiu-Hua; Ling, Jian; Peng, Jun; Cao, Qiu-E.; Wang, Lei; Ding, Zhong-Tao; Xiong, Jie

2013-04-01

131

Femtomolar DNA detection by parallel colorimetric darkfield microscopy of functionalized gold nanoparticles  

Microsoft Academic Search

We introduce a sensing platform for specific detection of DNA based on the formation of gold nanoparticles dimers on a surface. The specific coupling of a second gold nanoparticle to a surface bound nanoparticle by DNA hybridization results in a red shift of the nanoparticle plasmon peak. This shift can be detected as a color change in the darkfield image

Remco Verdoold; Ron Gill; Felicia Ungureanu; Robert Molenaar; Rob P. H. Kooyman

2011-01-01

132

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...

133

Colorimetric detection of mutations in epidermal growth factor receptor using gold nanoparticle aggregation  

Microsoft Academic Search

We have detected mutations in the epidermal growth factor receptor (EGFR) of non-small cell lung cancer cells using the selective aggregations of gold nanoparticles. Mutations in exon 19 and exon 21 of EGFR gene were detected in non-amplified genomic DNAs that were isolated from both the lung cancer cell lines and the cancer tissues of non-small cell lung cancer patients.

Hosub Lee; Taegyeong Kang; Kyong-Ah Yoon; So Yeong Lee; Sang-Woo Joo; Kangtaek Lee

2010-01-01

134

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

PubMed

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. PMID:23340972

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

2013-02-21

135

Development of a paper-based analytical device for colorimetric detection of select foodborne pathogens.  

PubMed

Foodborne pathogens are a major public health threat and financial burden for the food industry, individuals, and society, with an estimated 76 million cases of food-related illness occurring in the United States alone each year. Three of the most important causative bacterial agents of foodborne diseases are pathogenic strains of Escherichia coli , Salmonella spp., and Listeria monocytogenes , due to the severity and frequency of illness and disproportionally high number of fatalities. Their continued persistence in food has dictated the ongoing need for faster, simpler, and less expensive analytical systems capable of live pathogen detection in complex samples. Culture techniques for detection and identification of foodborne pathogens require 5-7 days to complete. Major improvements to molecular detection techniques have been introduced recently, including polymerase chain reaction (PCR). These methods can be tedious; require complex, expensive instrumentation; necessitate highly trained personnel; and are not easily amenable to routine screening. Here, a paper-based analytical device (?PAD) has been developed for the detection of E. coli O157:H7, Salmonella Typhimurium, and L. monocytogenes in food samples as a screening system. In this work, a paper-based microspot assay was created by use of wax printing on filter paper. Detection is achieved by measuring the color change when an enzyme associated with the pathogen of interest reacts with a chromogenic substrate. When combined with enrichment procedures, the method allows for an enrichment time of 12 h or less and is capable of detecting bacteria in concentrations in inoculated ready-to-eat (RTE) meat as low as 10(1) colony-forming units/cm(2). PMID:22320200

Jokerst, Jana C; Adkins, Jaclyn A; Bisha, Bledar; Mentele, Mallory M; Goodridge, Lawrence D; Henry, Charles S

2012-03-20

136

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

137

Comparative Evaluation of Colorimetric Microtiter Plate Systems for Detection of Herpes Simplex Virus in Cerebrospinal Fluid  

Microsoft Academic Search

In the past few years, application of the PCR to the detection of herpes simplex virus (HSV) DNA in the cerebrospinal fluid (CSF) from patients with encephalitis and meningitis has become standard laboratory practice. However, from an operational perspective, the true diagnostic value of PCR in this setting is yet to be realized because most laboratories subject the amplification products

YI-WEI TANG; PAUL N. RYS; BARBARA J. RUTLEDGE; P. SHAWN MITCHELL; THOMAS F. SMITH; DAVID H. PERSING

1998-01-01

138

A gold nanoparticle\\/latex microsphere-based colorimetric oligonucleotide detection method  

Microsoft Academic Search

An exceptionally simple and effective DNA detection methodology based on latex microsphere and gold nanoparticle probes has been developed. The latex and gold particle probes, which were functionalized with separate oligonucleotide sequences, undergo hybridization in the presence of target strands that are complementary to both of the probes. Duplex formation thus results in linking of gold nanoparticles to the latex

Robert A. Reynolds; Chad A. Mirkin; Robert L. Letsinger

2000-01-01

139

Synthesis of new heteroaryldi(diindolyl)methanes: Colorimetric detection of DNA by di(diindolylmethyl)carbazoles  

Microsoft Academic Search

We have synthesized di(diindolylmethyl)carbazoles and di(diindolylmethyl)pyrroles by the reaction of substituted indoles with\\u000a the corresponding carbazole and pyrroledicarboxaldehydes by employing a new catalyst PPh3.CF3SO3H. We have also demonstrated the utility of di(diindolylmethyl) carbazole derivatives for the colourimetric and fluorometric\\u000a detection of DNA.

Ramu Meesala; Rajagopal Nagararajan

2009-01-01

140

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

141

A novel porphyrin-containing polyimide nanofibrous membrane for colorimetric and fluorometric detection of pyridine vapor.  

PubMed

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

142

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.

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

2013-01-01

143

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

144

Gold nanoflowers based colorimetric detection of Hg2+ and Pb2+ ions  

NASA Astrophysics Data System (ADS)

An optical detection method based on the interaction of gold nanoflowers with Hg2+ and Pb2+ has been described. After interaction, gold nanoflowers change the color from violet to wine red. The nanoflowers are capable of determining Hg2+ and Pb2+ over a dynamic range of 1.0 × 10-6 and 1.0 × 10-5 M, respectively. The response time of nanoflowers depends on the concentration of ions. The presence of both Hg2+ and Pb2+ ions in the mixture having Au nanoflowers induced color changes of the solution within several seconds even at 1.0 × 10-6 M. Common metal ions were chosen to investigate their interference in Hg2+ and Pb2+ detection, and the concentration of each metal ion studied was 1.0 × 10-5 M. Other metallic ions could not induce color change even at 1.0 × 10-5 M. The feasibility of our method to detect Hg2+ and Pb2+ ions at high concentration in real water samples was verified. Water samples were from our own laboratory and no pretreatment was made. As the particles are stable they can be used for more than 3 months without observing any major deviation.

Nalawade, Pradnya; Kapoor, Sudhir

2013-12-01

145

Polydiacetylene liposomes functionalized with sialic acid bind and colorimetrically detect influenza virus  

SciTech Connect

In this paper we have demonstrated that polymerized liposomes are biomolecular materials that provide a molecular recognition function (sialic acid) and a detection element (polydiacetylene backbone), all within a single supramolecular assembly. The binding event is transduced to a visible color change, readily seen with the naked eye and quantified by absorption spectroscopy. Specificity of the color change was demonstrated by competitive inhibition studies. In addition, nonspecific adsorption, if it occurs. does not appear to affect the color of the liposome solutions. 28 refs., 2 figs.

Reichert, A.; Nagy, J.O.; Spevak, W.; Charych, D. (Lawrence Berkeley Lab., CA (United States))

1995-01-18

146

In Situ Growth of Silver Nanoparticles on Graphene Quantum Dots for Ultrasensitive Colorimetric Detection of H2O2 and Glucose.  

PubMed

We report a facile green approach for in situ growth of silver nanoparticles (AgNPs) on the surface of graphene quantum dots (GQDs). GQDs serve as both reducing agent and stabilizer, and no additional reducing agent and stabilizer is necessary. The GQDs/AgNPs hybrid exhibits a superior absorbance fading response toward the reduction of H2O2. A simple colorimetric procedure is thus proposed for ultrasensitive detection of H2O2 without additional chromogenic agent. It provides a record detection limit of 33 nM for the detection of H2O2 by the AgNPs-based sensing system. This colorimetric sensing system is further extended to the detection of glucose in combination with the specific catalytic effect of glucose oxidase for the oxidation of glucose and formation of H2O2, giving rise to a detection limit of 170 nM. The favorable performances of the GQDs/AgNPs hybrid are due to the peroxidase-like activity of GQDs. PMID:24862345

Chen, Shuai; Hai, Xin; Chen, Xu-Wei; Wang, Jian-Hua

2014-07-01

147

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

PubMed

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 Mn(2+) 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 Mn(2+) ions, which caused cross-linking aggregation. Transmission electron microscopic (TEM) images also revealed the aggregation of gold nanoparticles with the addition of Mn(2+) ions. The extinction ratio of absorbance at 700-550nm (A700/A550) was linear against the concentration of [Mn(2+)] ions. Thus, the optical absorption spectra of gold colloidal solution before and after the addition of Mn(2+) ions reveal the concentration of Mn(2+) ions in solution. PMID:24825666

Narayanan, Kannan Badri; Park, Hyun Ho

2014-10-15

148

Self-assembly of core-satellite gold nanoparticles for colorimetric detection of copper ions.  

PubMed

Molecule-coated nanoparticles are hybrid materials which can be engineered with novel properties. The molecular coating of metal nanoparticles can provide chemical functionality, enabling assembly of the nanoparticles that are important for applications, such as biosensing devices. Herein, we report a new self-assembly of core-satellite gold nanoparticles linked by a simple amino acid l-Cysteine for biosensing of Cu(2+). The plasmonic properties of core-satellite nano-assemblies were investigated, a new red shifted absorbance peak from about 600 to 800 nm was found, with specific wavelength depending on ratios with assembly of large and small gold nanoparticles. The spectral features obtained using surface-enhanced Raman spectroscopy (SERS) provided strong evidence for the assembly of the Cu(2+) ions to the L-Cysteine molecules leading to the successful formation of the core-satellite Cu(l-Cysteine) complex on the gold surfaces. In addition, a linear relationship between the concentration of mediating Cu(2+) and absorbance of self-assembled gold nanoparticles (GNPs) at 680 nm was obtained. These results strongly address the potential strategy for applying the functionalized GNPs as novel biosensing tools in trace detections of certain metal ions. PMID:24216206

Weng, Ziqing; Wang, Hongbin; Vongsvivut, Jitraporn; Li, Runqing; Glushenkov, Alexey M; He, Jin; Chen, Ying; Barrow, Colin J; Yang, Wenrong

2013-11-25

149

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

150

Colorimetric detection of platelet-derived growth factors through competitive interactions between proteins and functional gold nanoparticles.  

PubMed

We have developed a colorimetric assay-using aptamer modified 13-nm gold nanoparticles (Apt-Au NPs) and fibrinogen adsorbed Au NPs (Fib-Au NPs, 56nm)-for the highly selective and sensitive detection of platelet-derived growth factors (PDGF). Apt-Au NPs and Fib-Au NPs act as recognition and reporting units, respectively. PDGF-binding-aptamer (Apt(PDGF)) and 29-base-long thrombin-binding-aptamer (Apt(thr29)) are conjugated with Au NPs to prepare functional Apt-Au NPs (Apt(PDGF)/Apt(thr29)-Au NPs) for specific interaction with PDGF and thrombin, respectively. Thrombin interacts with Fib-Au NPs in solutions to catalyze the formation of insoluble fibrillar fibrin-Au NPs agglutinates through the polymerization of the unconjugated and conjugated fibrinogen. The activity of thrombin is suppressed once it interacts with the Apt(PDGF)/Apt(thr29)-Au NPs. The suppression decreases due to steric effects through the specific interaction of PDGF with Apt(PDGF), occurring on the surfaces of Apt(PDGF)/Apt(thr29)-Au NPs. Under optimal conditions [Apt(PDGF)/Apt(thr29)-Au NPs (25pM), thrombin (400pM) and Fib-Au NPs (30pM)], the Apt(PDGF)/Apt(thr29)-Au NPs/Fib-Au NPs probe responds linearly to PDGF over the concentration range of 0.5-20nM with a correlation coefficient of 0.96. The limit of detection (LOD, signal-to-noise ratio=3) for each of the three PDGF isoforms is 0.3nM in the presence of bovine serum albumin at 100?M. When using the Apt(PDGF)/Apt(thr29)-Au NPs as selectors for the enrichment of PDGF and for the removal of interferences from cell media, the LOD for PDGF provided by this probe is 35pM. The present probe reveals that the concentration of PDGF in the three cell media is 230 (±20)pM, showing its advantages of simplicity, sensitivity, and specificity. PMID:21900002

Lin, Tzu-En; Chen, Wei-His; Shiang, Yen-Chun; Huang, Chih-Ching; Chang, Huan-Tsung

2011-11-15

151

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

152

Structural, morphological and optical studies of l-cysteine modified silver nanoparticles and its application as a probe for the selective colorimetric detection of Hg(2+).  

PubMed

We report an extensive study on the evolution of a highly facile, selective colorimetric probe for Hg(2+) 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 Hg(2+), the absorption peak is quenched resulting in a drastic colour change. The sensor displays high selectivity to Hg(2+) over other metallic ions. PMID:24950383

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

2014-12-10

153

[Fe(CN)6]4- decorated mesoporous gelatin thin films for colorimetric detection and as sorbents of heavy metal ions.  

PubMed

[Fe(CN)6](4-) decorated mesoporous gelatin films, acting as colorimetric sensors and sorbents for heavy metal ions, were prepared by incorporating [Fe(CN)6](4-) ions into the mesoporous gelatin films through electrostatic interaction. Gelatin-Prussian blue (PB) and gelatin-PB analogue composite films were successfully synthesized by immersing the [Fe(CN)6](4-) decorated gelatin films into aqueous solutions of metal ions, such as Fe(3+), Cu(2+), Co(2+), Pb(2+) and Cd(2+) (all as nitrates). The in situ formation process of PB or its analogues in the films was investigated using quartz crystal microbalance (QCM) measurements. According to the different colors of the PB nanoparticles and its analogues, the [Fe(CN)6](4-) decorated mesoporous gelatin films demonstrated colorimetric sensor abilities for detecting the corresponding metal ions by the naked eye with sufficient sensitivity at 1 ppm level and a quite short response time of 5 minutes. Moreover, due to the [Fe(CN)6](4-) functionality and other functional groups of gelatin itself, this [Fe(CN)6](4-) decorated mesoporous gelatin film shows a tens times higher adsorption ability for heavy metal ions in water than that of activated carbon. Due to both the efficient detection and high adsorption ability for heavy metal ions, this film has wide potential applications for the detection and purification of heavy metal ions from polluted water. PMID:23887280

Shi, Li; Huang, Hubiao; Sun, Luwei; Lu, Yanping; Du, Binyang; Mao, Yiyin; Li, Junwei; Ye, Zhizhen; Peng, Xinsheng

2013-09-28

154

Surface-plasmon-based colorimetric detection of Cu(II) ions using label-free gold nanoparticles in aqueous thiosulfate systems  

NASA Astrophysics Data System (ADS)

We report colorimetric, label-free and non-aggregation-based gold nanoparticle (AuNP) probes for the highly selective detection of Cu(II) ions in aqueous environments. This detection scheme relies on the ability of Cu(II) ions to catalyze the leaching of gold at room temperature in the presence of thiosulfate species and ammonia. This simple and cost-effective probe provides rapid detection of Cu(II) ions at concentrations as low as 10 ppm. A similar detection method using AuNPs in ammonia-free thiosulfate solution is also viable at moderate reaction temperature (50?°C). The ammonia-free method also leads to marked damping and red-shifting of the surface plasmon resonance signal of the AuNP dispersion. The two methods clearly differ in the nature of the surface plasmon damping phenomenon, and their working mechanisms are plausibly explained based on the experimental investigations.

Tripathy, Suraj Kumar; Woo, Ju Yeon; Han, Chang-Soo

2012-08-01

155

Colorimetric detection of trace Hg2+ with near-infrared absorbing squaraine functionalized by dibenzo-18-crown-6 and its mechanism  

NASA Astrophysics Data System (ADS)

In this contribution, an improved near-infrared absorbing colorimetric detection of Hg2+ ion with high selectivity and sensitivity had been developed by using bis-dibenzo-18-crown-6-based squaraine (BCSQ) as sensor in aqueous media. The proposed method was applied to analyze trace Hg2+ in synthetic Hg2+ samples and natural Hg2+ samples. Under the optimum conditions, the detection had a linear range of 7.5-150 × 10-8 mol L-1 with a correlation coefficient (R) of 0.9983 combining a limit detection (3?, n = 20) of 5.6 × 10-9 mol L-1. The relative standard deviation (RSD) was lower than 2.4% (n = 5). The proposed method possesses the advantages of simplicity, rapidity, high selectivity and sensitivity. The action mechanism between BCSQ and Hg2+ was discussed in details.

Hu, Lei; Zhang, Yafei; Nie, Li; Xie, Chenggen; Yan, Zhengquan

2013-03-01

156

Direct Fast-Neutron Detection  

SciTech Connect

Direct fast-neutron detection is the detection of fast neutrons before they are moderated to thermal energy. We have investigated two approaches for using proton-recoil in plastic scintillators to detect fast neutrons and distinguish them from gamma-ray interactions. Both approaches use the difference in travel speed between neutrons and gamma rays as the basis for separating the types of events. In the first method, we examined the pulses generated during scattering in a plastic scintillator to see if they provide a means for distinguishing fast-neutron events from gamma-ray events. The slower speed of neutrons compared to gamma rays results in the production of broader pulses when neutrons scatter several times within a plastic scintillator. In contrast, gamma-ray interactions should produce narrow pulses, even if multiple scattering takes place, because the time between successive scattering is small. Experiments using a fast scintillator confirmed the presence of broader pulses from neutrons than from gamma rays. However, the difference in pulse widths between neutrons and gamma rays using the best commercially available scintillators was not sufficiently large to provide a practical means for distinguishing fast neutrons and gamma rays on a pulse-by-pulse basis. A faster scintillator is needed, and that scintillator might become available in the future. Results of the pulse-width studies were presented in a previous report (Peurrung et al. 1998), and they are only summarized here.

Stromswold, David C.; Peurrung, Anthony J.; Hansen, Randy R.; Reeder, Paul L.

1999-12-30

157

Direct Fast-Neutron Detection  

SciTech Connect

Direct fast-neutron detection is the detection of fast neutrons before they are moderated to thermal energy. We have investigated two approaches for using proton-recoil in plastic scintillators to detect fast neutrons and distinguish them from gamma-ray interactions. Both approaches use the difference in travel speed between neutrons and gamma rays as the basis for separating the types of events. In the first method, we examined the pulses generated during scattering in a plastic scintillator to see if they provide a means for distinguishing fast-neutron events from gamma-ray events. The slower speed of neutrons compared to gamma rays results in the production of broader pulses when neutrons scatter several times within a plastic scintillator. In contrast, gamma-ray interactions should produce narrow pulses, even if multiple scattering takes place, because the time between successive scattering is small. Experiments using a fast scintillator confirmed the presence of broader pulses from neutrons than from gamma rays. However, the difference in pulse widths between neutrons and gamma rays using the best commercially available scintillators was not sufficiently large to provide a practical means for distinguishing fast neutrons and gamma rays on a pulse-by-pulse basis. A faster scintillator is needed, and that scintillator might become available in the literature. Results of the pulse-width studies were presented in a previous report (peurrung et al. 1998), and they are only summarized here.

DC Stromswold; AJ Peurrung; RR Hansen; PL Reeder

2000-01-18

158

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)Lmole(-1) between the HSA-AuNC and bilirubin was discerned. The nano clusters each with size ~1.0nm (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±12nM (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±19nM by following the decrease in absorbance (at ?440nm) of the reaction and its rate constant (Kp) of 2.57±0.63mL?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

159

'Naked-eye' detection of fluoride and acetate anions by using simple and efficient urea and thiourea based colorimetric sensors  

NASA Astrophysics Data System (ADS)

Simple and efficient sensors 1 and 2 possessing azo and nitrophenyl as signaling units and urea and thiourea moieties as binding sites were designed and synthesized. These sensors were characterized by combination of 1H, 13C, APT, COSY NMR, FTIR, elemental analysis, and UV–vis spectral data. The interaction and colorimetric sensing properties of receptor 1 and 2 with different anions were investigated by the naked eye, as well as UV–visible and 1H NMR experiments. It was found that the receptor 1 and 2 are highly selective toward fluoride and acetate anions in CHCl3.

Okudan, Ahmet; Erdemir, Serkan; Kocyigit, Ozcan

2013-09-01

160

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.

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

2010-01-01

161

A new pyrene-based Schiff-base: A selective colorimetric and fluorescent chemosensor for detection of Cu(II) and Fe(III).  

PubMed

A new receptor 1 was prepared, for the detection of Cu(2+) and Fe(3+) in solutions as a colorimetric and fluorescent sensor, respectively. Receptor 1 shows highly selective and sensitive recognition toward Cu(2+) and Fe(3+) by naked eye UV-Vis and fluorescent color changes in aqueous solution (DMSO/H2O=8/2, v/v), respectively. The sensitivity toward Cu(2+) or Fe(3+) was not interfered with by the presence of other metal ions such as Mg(2+), Cd(2+), Ag(+), Zn(2+), Ni(2+), Co(2+), Mn(2+), Cr(3+), Ca(2+), Na(+), Pb(2+), K(+), Fe(2+), Li(+) and Hg(2+) ions. Receptor 1 can be used for semi-quantitative recognition of Cu(2+) ions at ppm level. The fluorescence microscopy experiments showed that the receptor is efficient for detection of Fe(3+) in vitro, developing a good image of the biological organelles. PMID:24769379

Bhorge, Yeshwant Ramchandra; Tsai, Haw-Tyng; Huang, Keh-Feng; Pape, Albert J; Janaki, Sudhakar Narasimha; Yen, Yao-Pin

2014-09-15

162

A new pyrene-based Schiff-base: A selective colorimetric and fluorescent chemosensor for detection of Cu(II) and Fe(III)  

NASA Astrophysics Data System (ADS)

A new receptor 1 was prepared, for the detection of Cu2+ and Fe3+ in solutions as a colorimetric and fluorescent sensor, respectively. Receptor 1 shows highly selective and sensitive recognition toward Cu2+ and Fe3+ by naked eye UV-Vis and fluorescent color changes in aqueous solution (DMSO/H2O = 8/2, v/v), respectively. The sensitivity toward Cu2+ or Fe3+ was not interfered with by the presence of other metal ions such as Mg2+, Cd2+, Ag+, Zn2+, Ni2+, Co2+, Mn2+, Cr3+, Ca2+, Na+, Pb2+, K+, Fe2+, Li+ and Hg2+ ions. Receptor 1 can be used for semi-quantitative recognition of Cu2+ ions at ppm level. The fluorescence microscopy experiments showed that the receptor is efficient for detection of Fe3+ in vitro, developing a good image of the biological organelles.

Bhorge, Yeshwant Ramchandra; Tsai, Haw-Tyng; Huang, Keh-Feng; Pape, Albert J.; Janaki, Sudhakar Narasimha; Yen, Yao-Pin

2014-09-01

163

Low-cost preparation of photoluminescent carbon nanodots and application as peroxidase mimetics in colorimetric detection of H2O2 and glucose.  

PubMed

A low-cost and facile preparation of water-soluble photoluminescent carbon nanodots (CDs) with a quantum yield of approximately 12.4% by hydrothermal method utilizing the leaves of Olea Europaea, a large number of planted trees in southwest of China, as a carbon source is developed for the first time. The prepared photoluminescent CDs not only show favorable photoluminescent properties, but also possess intrinsic peroxidase-like activity for colorimetric and UV-Vis absorption detection of hydrogen oxide (H2O2) and glucose. This sensing system exhibits excellent sensitivity toward H2O2 and glucose with the limit of detection as low as 0.6 microM and 5.2 microM. The practical use of this system for glucose determination in serum samples is also demonstrated successfully. The stability and low cost of photoluminescent CDs make them a powerful tool for a wide range of potential applications in biochemical analysis. PMID:24245121

Wu, Di; Deng, Xiang; Huang, Xiaomei; Wang, Kun; Liu, Qingye

2013-10-01

164

Direct cosmic-ray detection  

NASA Astrophysics Data System (ADS)

One century after the discovery of cosmic rays, many questions remain open on their origin, nature, and transport. Experiments to detect them directly have constantly improved, and are today of highly diversified designs. Indeed, precise measurements of cosmic rays in an energy range from ˜104 to ˜1015eV allow one to study the mechanism of acceleration of primary cosmic rays up to very high energy, to characterise their possible sources, and to clarify their interactions with the interstellar medium. Such measurements of elemental cosmic-ray spectra require complementary and redundant charge- and energy-identification detectors, such as the balloon-borne Cosmic-Ray Energetics And Mass (CREAM) experiment, which measures cosmic rays from 1012 to 1015 eV for all elements up to and including iron. Here I present the current status of direct cosmic-ray measurements, with the focus on the latest CREAM results. Finally, I briefly discuss the cosmic-ray identification above the knee.

Putze, Antje

2012-01-01

165

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

166

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

167

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 526nm, 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 20ngmL(-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

168

New colorimetric and fluorometric sensing strategy based on the anisotropic growth of histidine-mediated synthesis of gold nanoclusters for iodide-specific detection.  

PubMed

Iodide, as a biologically important anion, it remains a worthwhile yet challenging undertaking to find a sensitive and specific approach to provide a technically simple iodide detection. In this article, it was found that no other ions than iodide-induced anisotropic growth of gold nanocrystals (AuNCs) originated from a small molecule, histidine-mediated synthesis of AuNCs, were observed. Simultaneously, it is accompanied by the fluorescence quenching of AuNCs and the naked-eye visible color change. Therefore, a new colorimetric and fluorometric sensing strategy was developed for the iodide-specific detection. Compared with currently reported methods, the present one displays the advantages of the visual detection and simplicity. The quenched fluorescence and enhanced surface plasmon resonance absorbance were found to be proportional to the iodide concentration over the range of 0.8-60 and 1.2-50 ?M with a detection limit (3?) of 118 nM and 215 nM, respectively. PMID:23393644

Wang, Yifeng; Zhu, Haiyan; Yang, Xiaoming; Dou, Yao; Liu, Zhongde

2013-04-01

169

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

170

Malonamide-functionalized gold nanoparticles for selective, colorimetric sensing of trivalent lanthanide ions.  

PubMed

A selective and sensitive molecular sensor for trivalent lanthanide (Ln(3+)) ions based upon a malonamide-functionalized gold nanoparticle was developed for colorimetric detection in water. A new synthetic approach permits nanoparticle synthesis, stabilization, and incorporation of a selective lanthanide binding site in a single, direct step. The design incorporates a specifically tailored dual function precursor ligand that bears a sodium thiosulfate (Bunte salt) group that links to the gold nanoparticle core and a tetramethylmalonamide (TMMA) group that serves as a selective Ln(3+) binding site. The sensor's colorimetric response to lanthanide ions is immediate, and it is sensitive down to approximately 50 nM for Eu(3+) and Sm(3+). This study demonstrates a general strategy for direct, convenient nanoparticle synthesis that enables the incorporation of analyte binding groups directly to the nanoparticle surface, allowing colorimetric sensors to be developed for widespread use. The one-step synthesis offers uniform surface ligand composition, reduces the volume of waste generated during nanoparticle synthesis and purification, produces functionalized gold nanoparticles that are stable in nonmodified aqueous environments, and offers colorimetric detection at ambient temperature. PMID:19904966

Lisowski, Carmen E; Hutchison, James E

2009-12-15

171

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

172

Development of a Colorimetric Test for Uranium.  

National Technical Information Service (NTIS)

This paper discusses the development of and proposed enhancements to a colorimetric test for the detection of uranium in biological samples such as urine. The goal of this work is to develop a technique for the detection of uranium that could: (1) be cond...

D. E. McClain J. F. Kalinich

2005-01-01

173

4-(8-Quinolyl)amino-7-nitro-2,1,3-benzoxadiazole as a new colorimetric probe for rapid and visual detection of Hg2+  

NASA Astrophysics Data System (ADS)

4-Amino-7-nitro-2,1,3-benzoxadiazole (ANBD) usually serves as a scaffold for developing fluorescent probes. In this paper, however, ANBD has been used as a chromogenic unit to design a new colorimetric probe, 4-(8-quinolyl)amino-7-nitro-2,1,3-benzoxadiazole (1), for rapid and visual detection of Hg2+. The reaction of 1 with Hg2+ in NaH2PO4-Na2HPO4 buffer (pH 7.0) containing 70% (v/v) acetonitrile forms a 1:1 complex, accompanying a red shift of the absorption maximum from 482 nm to 557 nm and a distinct color change from orange to violet. Moreover the color reaction exhibits a high selectivity and sensitivity to Hg2+ only, instead of other common metal ions. This behavior may be ascribed to the formation of a specific 1-Hg2+ complex, which is supported by 1H NMR titration experiments. The present study is not only a supplement to the detection method of Hg2+, but also a merit to the chemistry of 4-amino-7-nitro-2,1,3-benzoxadiazole.

Wang, Ke; Yang, Lixue; Zhao, Chuan; Ma, Huimin

2013-03-01

174

Novel, highly selective detection of Cr(III) in aqueous solution based on a gold nanoparticles colorimetric assay and its application for determining Cr(VI).  

PubMed

A simple, rapid, sensitive and field-portable colorimetric technique for the determination of Cr(III) in aqueous solution based on an aggregation-induced color transition of gold nanoparticles (AuNPs) has been developed. AuNPs were first functionalized with a dithiocarbamate-modified N-benzyl-4-(pyridin-4-ylmethyl)aniline ligand (BP-DTC). Chelation of Cr(III) by several of these ligands, bound to different nanoparticles, led to nanoparticle aggregation in solution. This gave rise to a color change from wine-red to blue that was discernible by the naked eye and an easily measurable alteration in the extinction spectrum of the particles. The method could be used to determine Cr(III) with a detection limit of 31 ppb. Furthermore, selective detection of trace Cr(III) in aqueous solution in the presence of 12 other transition metal ions has been achieved. Toward the goal of practical applications, the sensor has been further evaluated with a view to monitoring Cr(III) in nutritional supplements and the blood of diabetes patients and also applied in the indirect determination of Cr(VI) in waste water. PMID:22652267

Zhao, Liang; Jin, Yin; Yan, Zhangwei; Liu, Yuanyuan; Zhu, Hongjun

2012-06-20

175

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

176

A highly sensitive and selective turn-on fluorogenic and colorimetric sensor based on pyrene-functionalized magnetic nanoparticles for Hg2+ detection and cell imaging.  

PubMed

In this paper, a colorimetric and "turn-on" fluorescent sensor (Py-Si-Fe3O4@SiO2 NPs) for Hg(2+) detection was designed with pyrene derivative covalently grafted onto the surface of magnetic core/shell Fe3O4@SiO2 nanoparticles using the silanol hydrolysis approach. The Py-Si-Fe3O4@SiO2 inorganic-organic hybrid material was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray power diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and fluorescence emission. The results of fluorescence spectra showed that the resultant multifunctional nanoparticles exhibited selective turn-on type fluorescence enhancement with Hg(2+). In addition, the presence of magnetic Fe3O4 nanoparticles in the sensor Py-Si-Fe3O4@SiO2 NPs would also facilitate the magnetic separation of Hg(2+)-Py-Si-Fe3O4@SiO2 from the solution. The as-prepared chemosensor was also successfully applied to detect Hg(2+) in environmental water samples and serum sample. Results from confocal laser scanning microscopy experiments demonstrated that this chemosensor was cell permeable and can be used as a fluorescent probe for monitoring Hg(2+) in living cells. PMID:24209350

Chen, Ling; Zheng, Baozhan; Guo, Yong; Du, Juan; Xiao, Dan; Bo, Lin

2013-12-15

177

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

178

A new rapid colorimetric detection method of Al(3+) with high sensitivity and excellent selectivity based on a new mechanism of aggregation of smaller etched silver nanoparticles.  

PubMed

As a pathogenic factor of the Alzheimer?s disease, aluminum has been associated with the damage of the central nervous system in humans. In this study, we propose a new facile and rapid colorimetric detection method of Al(3+) with excellent selectivity and high sensitivity based on silver nanoparticles (AgNPs) stabilized by reduced glutathione (GSH) in the presence of l-cysteine (Cys). The new mechanism of our Al(3+) detection system based on GSH-AgNPs, i.e., aggregation of smaller etched GSH-AgNPs, are confirmed by TEM, EDS and DLS. The aggregation of smaller etched GSH-AgNPs results in obvious color change of the nanoparticle dispersion from yellow to reddish brown, and red shift and intensity decrease of the surface plasmon resonance (SPR) absorption. The GSH concentration, Cys concentration and pH value of the GSH-AgNPRs-based detection system are respectively optimized to be 10.0mM, 50.0mM and 6.0 according to the sensing effect of Al(3+). At the optimized conditions, the selectivity of the GSH-AgNPs detection system for Al(3+) is excellent compared with other ions including K(+), Mg(2+), Fe(3+), Co(2+), Mn(2+), Zn(2+), Cd(2+), Pb(2+), Ca(2+), Ba(2+), Cu(2+), Cr(3+), Hg(2+), Ni(2+), [Formula: see text] , [Formula: see text] , [Formula: see text] , [Formula: see text] and [Formula: see text] . Furthermore, this detection system is very sensitive for Al(3+). The limit of detection (LOD) is 1.2µM by the naked eyes and 0.16µM by UV-vis spectra, which are both much lower than the national drinking water standards (7.4µM). Furthermore, the UV-vis detection offers a good linear detection range from 0.4 to 4.0µM (R(2)=0.9924), which indicates that our developed detection system can also be used for the quantitative analysis of Al(3+). The detection results of real water samples indicate that this method can be used for real water detection. PMID:24720995

Yang, Ningning; Gao, Yuexia; Zhang, Yujie; Shen, Zheyu; Wu, Aiguo

2014-05-01

179

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

180

Complementary of Dark Matter Direct Detection Targets.  

National Technical Information Service (NTIS)

We investigate the reconstruction capabilities of 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 thresho...

G. Bertone L. Baudis L. E. Strigari M. Pato R. Trotta R. R. de Austri

2011-01-01

181

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

182

Gaze Direction Detection for Cursor Control  

Microsoft Academic Search

\\u000a In this paper, we describe an efficient and fast method of locating iris for gaze direction detection by using computer vision\\u000a techniques. Then, an application is developed where the cursor movement is achieved according to the detected gaze direction.\\u000a The goal of this project is to create an easy to use application, capable of running on low budget hardware, which

V. Theodorou; C. Zouzoulas; Georgios A. Triantafyllidis; G. Papadourakis

183

Directional structures detection using steerable pyramid  

Microsoft Academic Search

The object of the work described in this paper concerns directional structures detection for particular aspects of inspection, such as scratches and marbling defect detection in leather images. Because of the very specific geometry of these structures, we intend to apply a multiscale and orientation-shiftable method. Scratches and marbling have various shapes and sizes. Multiscale approaches using oriented filters have

Florence Denis; Atilla M. Baskurt

2003-01-01

184

Colorimetric Determination of Citrulline Residues in Proteins  

Microsoft Academic Search

A method is described for the direct colorimetric determination of citrulline residues in proteins based on the reaction with diacetylmonoxime in the presence of lower concentrations of sulfuric acid. The reduced sensitivity due to the lower acid concentration was overcome by the addition of ferric chloride which also contributed to the color stabilization. Insoluble proteins or proteins resulting in turbidity

Kiyoshi Sugawara; Yusuke Yoshizawa; Sinfu Tzeng; William L. Epstein; Kimie Fukuyama

1998-01-01

185

A simple cassette as point-of-care diagnostic device for naked-eye colorimetric bacteria detection.  

PubMed

Effective pathogen detection is necessary for treatment of infectious diseases. Point of care (POC) devices have tremendously improved the global human heath. However, design criteria for sample processing POC devices for pathogen detection in limited infrastructure are challenging and can make a significant contribution to global health by providing rapid and sensitive detection of bacteria in food, water, and patient samples. In this paper, we demonstrate a novel portable POC diagnostic device that is simple to assemble for genetic detection of bacterial pathogens by isothermal DNA amplification. The device is fabricated with very low production cost, using simple methods and easy-to-access materials on a flexible ribbon polyethylene substrate. We showed that the device is capable of detection of 30 CFU mL(-1) of E. coli and 200 CFU mL(-1) of S. aureus in less than 1 hour. Through numerical simulations, we estimated that the device can be extended to high-throughput detection simultaneously performing a minimum of 36 analyses. This robust and sensitive detection device can be assembled and operated by non-specialist personnel, particularly for multiple bacterial pathogen detections in low-resource settings. PMID:24300967

Safavieh, Mohammadali; Ahmed, Minhaz Uddin; Sokullu, Esen; Ng, Andy; Braescu, Liliana; Zourob, Mohammed

2014-01-21

186

Borehole directional radar detection of subsurface cavities  

SciTech Connect

Borehole electromagnetic techniques have emerged as a means for detecting and delineating rock structure details in the vicinity of the drill hole under test. A particular application for such techniques has been the detection of subsurface cavities, either natural or man-made. To date, borehole EM probing systems have only provided omnidirectional response around the drill hole, precluding the interpretation of azimuthal target direction. A new borehole radar probe developed for the US Bureau of Mines having a rotary azimuthal scan antenna with undirectional radiation pattern is capable of providing useful target direction information as well as directionally comparative discrimination of weaker EM contrasts surrounding the borehole.

Owen, T.E.; Suhler, S.A.

1982-04-01

187

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

188

Direct detection of nonchiral dark matter  

SciTech Connect

Direct detection experiments rule out fermion dark matter that is a chiral representation of the electroweak gauge group. Nonchiral real, complex and singlet representations, however, provide viable fermion dark-matter candidates. Although any one of these candidates will be virtually impossible to detect at the LHC, it is shown that they may be detected at future planned direct detection experiments. For the real case, an irreducible radiative coupling to quarks may allow a detection. The complex case in general has an experimentally ruled out tree-level coupling to quarks via Z-boson exchange. However, in the case of two SU(2){sub L} doublets, a higher-dimensional coupling to the Higgs can suppress this coupling, and a remaining irreducible radiative coupling may allow a detection. Singlet dark matter could be detected through a coupling to quarks via Higgs exchange. Since all nonchiral dark matter can have a coupling to the Higgs, at least some of its mass can be obtained from electroweak symmetry breaking, and this mass is a useful characterization of its direct detection cross section.

Essig, Rouven [NHETC, Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854 (United States)

2008-07-01

189

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.

Halliwell, Jennifer; Gwenin, Christopher

2013-01-01

190

Comparison of colorimetric, fluorescent, and enzymatic amplification substrate systems in an enzyme immunoassay for detection of DNA-RNA hybrids.  

PubMed Central

The monoclonal antibody solution hybridization assay is a novel enzyme immunoassay for detection of RNA with a biotinylated DNA probe. To increase the sensitivity of this test, a fluorescent substrate and an enzymatic amplification cycling system were compared with a conventional colorigenic substrate for alkaline phosphatase. The fluorescent, cycling, and colorigenic substrates detected, respectively, 10, 10, and 100 amol of unbound alkaline phosphatase in 2 h. With a prolonged incubation period of 16.6 h, the conventional substrate measured 10 amol of the enzyme. In the immunoassay for RNA detection, the fluorescence and cycling assays were faster than that using the colorigenic substrate and reached an endpoint sensitivity of 3.2 pg/ml (0.16 pg per assay) of cRNA. However, longer incubation periods (16.6 h) for optimal generation of the colorigenic product led to a comparable level of sensitivity for the conventional substrate.

Coutlee, F; Viscidi, R P; Yolken, R H

1989-01-01

191

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

2008-09-02

192

Detection of possible economically motivated adulterants in heparin sodium and low molecular weight heparins with a colorimetric microplate based assay.  

PubMed

Recently, we described a 96-well plate format assay for visual detection of oversulfated chondroitin sulfate A (OSCS) contamination in heparin samples based on a water-soluble cationic polythiophene polymer (3-(2-(N-(N'-methylimidazole))ethoxy)-4-methylthiophene (LPTP)) and heparinase digestion of heparin. Here, we establish the specificity of the LPTP/heparinase test with a unique set of reagents that define the structural requirements for significant LPTP chemosensor color change. For example, we observed a biphasic behavior of larger shifts to the red in the UV absorbance spectra with decreasing average molecular weight of heparin chains with a break below 12-mer chain lengths. In addition, the oversulfation of chondroitin sulfate A (CSA) to a partially (PSCS) or fully (OSCS) sulfated form caused progressively less red shift of LPTP solutions. Furthermore, glycosaminoglycans (GAGs) containing glucuronic acid caused distinct spectral patterns compared to iduronic acid containing GAGs. We applied the LPTP/heparinase test to detection of OSCS (?0.03% (w/w) visually or 0.01% using a plate reader) in 10 ?g amounts of low molecular weight heparins (LMWHs; i.e. dalteparin, tinzaparin, or enoxaparin). Furthermore, because other oversulfated GAGs are possible economically motivated adulterants (EMAs) in heparin sodium, we tested the capacity of the LPTP/heparinase assay to detect oversulfated dermatan sulfate (OSDS), heparin (OSH), and heparan sulfate (OSHS). These potential EMAs were visually detectable at a level of ?0.1% when spiked into heparin sodium. We conclude that the LPTP/heparinase test visually detects oversulfated GAGs in heparin sodium and LMWHs in a format potentially amenable to high-throughput screening. PMID:21819047

Sommers, Cynthia D; Keire, David A

2011-09-15

193

Directional structures detection using steerable pyramid  

NASA Astrophysics Data System (ADS)

The object of the work described in this paper concerns directional structures detection for particular aspects of inspection, such as scratches and marbling defect detection in leather images. Because of the very specific geometry of these structures, we intend to apply a multiscale and orientation-shiftable method. Scratches and marbling have various shapes and sizes. Multiscale approaches using oriented filters have proved to be efficient to detect such curvilinear patterns. We first use the information given by the increase of gray levels in the image to locate suspicious regions. The detection is then based on steerable filters, which can be steered to any orientation fixed by the user, and are synthesized using a limited number of basic filters. These filters are used in a recursive multi-scale transform: the steerable pyramid. Then, the curvilinear structures are extracted from the directional images at different scales.

Denis, Florence; Baskurt, Atilla M.

2003-04-01

194

Novel antibody/gold nanoparticle/magnetic nanoparticle nanocomposites for immunomagnetic separation and rapid colorimetric detection of Staphylococcus aureus in milk.  

PubMed

We demonstrated the new antibody/gold nanoparticle/magnetic nanoparticle nanocomposites (antibody/AuNP/MNPs) and their application in the detection of the foodborne pathogen, Staphylococcus aureus (S. aureus), in milk. The nanocomposites were synthesized by coating the MNPs with bovine serum albumin (BSA) then adsorbing the AuNPs and anti-S. aureus antibodies on their surface. Using the completed immunomagnetic nanostructures, S. aureus inoculated in the milk sample was captured and isolated from the medium using the permanent magnet. The nanoparticle-bound cells as well as the unbound cells in the supernatant were enumerated via surface plating to evaluate the target binding capacity of the nanocomposites. The capture efficiencies of the antibody/AuNP/MNPs were 96% and 78% for S. aureus in PBS and the milk sample respectively, which were significantly higher than those of the antibody-coupled MNPs without any AuNP. The captured cells were also applied to the selective filtration system to produce color signals that were used for the detection of the target pathogen. During the filtration, the cells bound to the antibody/AuNP/MNPs remained on the surface of the membrane filter while unbound nanoparticles passed through the uniform pores of the membrane. After the gold enhancement, the cells-particles complex resting on the membrane surface rendered a visible color, and the signal intensity became higher as the target cell concentration increased. The detection limits of this colorimetric sensor were 1.5×10(3) and 1.5×10(5)CFU for S. aureus in PBS and the milk sample respectively. This sensing mechanism also had the high specificity for S. aureus over the other pathogens such as Escherichia coli, Listeria monocytogenes, and Salmonella enterica. The assay required only 40min to obtain the results. With the use of the appropriate antibodies, our immunomagnetic nanocomposites-based detection strategy can provide an easy, convenient, and rapid sensing method for a wide range of pathogens. PMID:23370174

Sung, Yun Ju; Suk, Ho-Jun; Sung, Hwa Young; Li, Taihua; Poo, Haryoung; Kim, Min-Gon

2013-05-15

195

Colorimetric and ratiometric fluorescent detection of sulfite in water via cationic surfactant-promoted addition of sulfite to ?,?-unsaturated ketone.  

PubMed

Three fluorescent probes were constructed by incorporating an ?,?-unsaturated ketone to a coumarin fluorophore. The selective addition of sulfite to the alkene of TSP assisted by cetyltrimethyl ammonium bromide (CTAB) micelle can be visualized by dramatic color and ratiometric fluorescence changes. In CTAB-PBS system, the fluorescence intensity ratio at 465 nm and 592 nm (I465/I592) and the absorbance ratio at 390 nm and 470 nm (A390/A470) were linearly proportional to sulfite concentration in the range of 0.5-150 ?M, and the detection limit was 0.2 ?M. Good selectivity and competition of TSP1 towards sulfite over several anions and biological thiols were acquired. Probe TSP1 was used to detect sulfite in three realistic samples (mineral water, sugar and white wine) with good recovery. PMID:23845496

Tian, Haiyu; Qian, Junhong; Sun, Qian; Bai, Hongyan; Zhang, Weibing

2013-07-25

196

Au nanoparticles and polyaniline coated resin beads for simultaneous catalytic oxidation of glucose and colorimetric detection of the product.  

PubMed

In this letter, we report the synthesis of Au nanoparticles (NPs) and polyaniline (PANI) on the same cation-exchange resin beads and demonstrate their use in catalyzing the oxidation of glucose to gluconic acid by Au NPs and simultaneously in detecting the formation of the acid by the color change of PANI. The synthesis was carried out by exchanging the cations of the resins with HAuCl4 and anilinuium chloride and then reducing the metal ions by NaBH4 to produce Au NPs followed by polymerization of aniline using H2O2. The green emeraldine salt form of PANI thus obtained was treated with NaOH to be converted to blue emeraldine base before use. The deposition of Au NPs was confirmed by a change in color of the bead, visible spectroscopy, X-ray diffraction, and scanning electron microscopic measurements. On the other hand, the presence of PANI was confirmed by Fourier transform infrared (FTIR) and ultraviolet-visible (UV-vis) spectroscopy. The formation of gluconic acid from glucose was confirmed by FTIR spectroscopy. We could detect the presence of glucose of a minimum 1.0 mM concentration in water, using the present method. Our experimental observations demonstrate the possibility of the incorporation of multifunctional components on the surfaces of resins for carrying out a chemical reaction as well as detection of the product. PMID:15723451

Majumdar, Gitanjali; Goswami, Mausumi; Sarma, Tridib Kumar; Paul, Anumita; Chattopadhyay, Arun

2005-03-01

197

Atomic absorption spectroscopic, conductometric and colorimetric methods for determination of some fluoroquinolone antibacterials using ammonium reineckate  

NASA Astrophysics Data System (ADS)

Three accurate, rapid and simple atomic absorption spectrometric (AAS), conductometric and colorimetric methods were developed for the determination of gatifloxacin (GTF), moxifloxacin (MXF) and sparfloxacin (SPF). The proposed methods depend upon the reaction of ammonium reineckate with the studied drugs to form stable precipitate of ion-pair complexes, which was dissolved in acetone. The pink coloured complexes were determined either by AAS or colorimetrically at ?max 525 nm directly using the dissolved complex. Using conductometric titration, the studied drugs could be evaluated in 50% (v/v) acetone. The optimizations of various experimental conditions were described. Optimum concentration ranges for the determination of GTF, MXF and SPF were 5.0-150, 40-440 ?g mL -1 and 0.10-1.5 mg mL -1 using atomic absorption (AAS), conductometric and colorimetric methods, respectively. Detection and quantification limits are ranges from 1.5 to 2.3 ?g mL -1 using AAS method or 30-45 ?g mL -1 using colorimetric method. The proposed procedures have been applied successfully to the analysis of these drugs in pharmaceutical formulations and the results are favourably comparable to the reference methods.

Al-Ghannam, Sheikha M.

2008-04-01

198

Colorimetric detection of morphine in a molecularly imprinted polymer using an aqueous mixture of Fe 3+ and [Fe(CN) 6] 3?  

Microsoft Academic Search

In this work, a molecularly imprinted polymer (MIP) of morphine (MO) was prepared through thermal radical copolymerization of methacrylic acid (MAA) and ethylene glycol dimethacrylate (EDMA) in the presence of MO templates, and a molecularly imprinted sorbent assay (MIA) based on a colorimetric reporter was developed to determine the adsorption isotherm of MO–MIP binding. In practice, the MO-bound MIP was

Huan-Cheng Hsu; Lin-Chi Chen; Kuo-Chuan Ho

2004-01-01

199

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

200

PBXL Fluorescent Dyes for Ultrasensitive Direct Detection  

Microsoft Academic Search

PBXL™ dyes are a group of phycobilisome-based fluors that provide high sensitivity in direct fluorescent detection formats. Phycobilisomes are proteinaceous, supramolecular complexes that are photosynthetic antennae complexes in red algae and cyanobacteria. For the PBXL dyes, the phycobilisome has been chemically cross-linked in such a way that it remains water soluble and stable. Stabilized phycobilisomes (PBXL dyes) have high complex

Steven J. Zoha; Shakuntala Ramnarain; John P. Morseman; Mark W. Moss; F. C. Thomas Allnutt; Yu-Hui Rogers; Bronwen Harvey

1999-01-01

201

Colorimetric detection of fluoride ion by 5-arylidenebarbituric acids: dual interaction mode for fluoride ion with single receptor.  

PubMed

Two 5-arylidenebarbituric acid derivatives (IH and IM) have been synthesized by the Knoevenagel condensation of barbituric acid with 4-N,N-dimethylamino benzaldehyde and studied for anion sensing activities. Both receptors sense fluoride ion with high selectivity and sensitivity and the sensing action has been demonstrated by naked eye detection, UV-visible absorption, and fluorescence spectral changes in the presence of F(-). Indeed, the F(-) sensing mechanism for receptor IH depends on F(-) ion concentration. While at higher concentrations F(-) forms strong hydrogen bonding interaction with the N-H proton of the receptor, at lower concentrations sensing is influenced by the deprotonation of the methylene proton, followed by the chemical reaction, which is also confirmed by the (1)H-NMR technique. On the other hand, when replacing the N-H proton with a methyl group, IM does not show any concentration dependent behaviour with F(-). The F(-) concentration dependent sensing is attributed to the changes in the receptor-anion interaction equilibrium, where at higher F(-) concentrations, F(-) interacts with the receptor through hydrogen bonding and at lower concentrations it induces a chemical reaction. PMID:24500374

Saravanan, Chinnusamy; Easwaramoorthi, Shanmugam; Wang, Leeyih

2014-04-01

202

Wind measurement via direct detection lidar  

NASA Astrophysics Data System (ADS)

Wind sensing Lidar is considered a promising technology for high quality wind measurements required for various applications such as hub height wind resource assessment, power curve measurements and advanced, real time, forward looking turbine control. Until recently, the only available Lidar technology was based on coherent Doppler shift detection, whose market acceptance has been slow primarily due to its exuberant price. Direct detection Lidar technology provides an alternative to remote sensing of wind by incorporating high precision measurement, a robust design and an affordable price tag.

Afek, I.; Sela, N.; Narkiss, N.; Shamai, G.; Tsadka, S.

2013-10-01

203

Direct detection of dark matter axions with directional sensitivity  

NASA Astrophysics Data System (ADS)

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 ?a is sufficiently larger than the cavity dimensions L for a fully coherent conversion, i.e. ?agtrsim2?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.

2012-10-01

204

Direct optical detection in bioanalysis: an update  

Microsoft Academic Search

In biomolecular interaction analysis, direct optical detection is attracting increasing interest in academia and industry.\\u000a Therefore, a previous review has been updated. Optical principles are given in brief, focussing especially on modern and frequently\\u000a used techniques. Commercialized methods are listed with some specific applications. In addition, some of the many applications\\u000a found in the literature are listed; others which have

Günter Gauglitz

2010-01-01

205

A label-free activatable aptamer probe for colorimetric detection of cancer cells based on binding-triggered in situ catalysis of split DNAzyme.  

PubMed

A novel label-free tailed hairpin-shaped activatable aptamer probe (THAAP) was developed by rationally integrating an aptamer and a split G-quadruplex into one sequence. Based on target recognition-triggered in situ catalysis of split DNAzyme, the THAAP strategy achieved a simple, fast, washing-free, specific and quantitative colorimetric assay of human leukemic CCRF-CEM cells. PMID:25037636

Shi, Hui; Li, Duo; Xu, Fengzhou; He, Xiaoxiao; Wang, Kemin; Ye, Xiaosheng; Tang, Jinlu; He, Chunmei

2014-07-28

206

Direct detection of unamplified DNA from pathogenic mycobacteria using DNA-derivatized gold nanoparticles  

Microsoft Academic Search

Mycobacterial infections have a high economic, human and animal health impact. Herein, we present the development of a colorimetric method that relies on the use of gold nanoparticles for fast and specific detection of Mycobacterium spp. dispensing with the need for DNA amplification. The result can be recorded by visual and\\/or spectrophotometric comparison of solutions before and after acid induced

Emmanouil Liandris; Maria Gazouli; Margarita Andreadou; Mirjana ?omor; Nadica Abazovic; Leonardo A. Sechi; John Ikonomopoulos

2009-01-01

207

NASA direct detection laser diode driver  

NASA Technical Reports Server (NTRS)

TRW has developed a prototype driver circuit for GaAs laser diodes as part of the NASA/Goddard Space Flight Center's Direct Detection Laser Transceiver (DDLT) program. The circuit is designed to drive the laser diode over a range of user-selectable data rates from 1.7 to 220 Mbps, Manchester-encoded, while ensuring compatibility with 8-bit and quaternary pulse position modulation (QPPM) formats for simulating deep space communications. The resulting hybrid circuit has demonstrated 10 to 90 percent rise and fall times of less than 300 ps at peak currents exceeding 100 mA.

Seery, B. D.; Hornbuckle, C. A.

1989-01-01

208

Direct detection of multicomponent secluded WIMPs  

SciTech Connect

Dark matter candidates comprising several substates separated by a small mass gap {delta}m, and coupled to the standard model by (sub-)GeV force carriers, can exhibit nontrivial scattering interactions in direct-detection experiments. We analyze the secluded U(1){sub S}-mediated weakly interacting massive particle (WIMP) scenario, and calculate the elastic and inelastic cross sections for multicomponent WIMP scattering off nuclei. We find that second-order elastic scattering, mediated by virtual excited states, provides strong sensitivity to the parameters of the model for a wide range of mass splittings, while for small {delta}m the WIMP excited states have lifetimes exceeding the age of the Universe, and generically have a fractional relative abundance above 0.1%. This generates even stronger constraints for {delta}m < or approx. 200 keV due to exothermic deexcitation events in detectors.

Batell, Brian [Perimeter Institute for Theoretical Physics, Waterloo, ON, N2J 2W9 (Canada); Pospelov, Maxim [Perimeter Institute for Theoretical Physics, Waterloo, ON, N2J 2W9 (Canada); Department of Physics and Astronomy, University of Victoria, Victoria, BC, V8P 1A1 (Canada); Ritz, Adam [Department of Physics and Astronomy, University of Victoria, Victoria, BC, V8P 1A1 (Canada)

2009-06-01

209

The Earth's velocity for direct detection experiments  

NASA Astrophysics Data System (ADS)

The Earth's velocity relative to the Sun in galactic coordinates is required in the rate calculation for direct detection experiments. We provide a rigorous derivation of this quantity to first order in the eccentricity of the Earth's orbit. We also discuss the effect of the precession of the equinoxes, which has hitherto received little explicit discussion. Comparing with other expressions in the literature, we confirm that the expression of Lee, Lisanti and Safdi is correct, while the expression of Lewin and Smith, the de facto standard expression, contains an error. For calculations of the absolute event rate, the leading order expression is sufficient while for modulation searches, an expression with the eccentricity is required for accurate predictions of the modulation phase.

McCabe, Christopher

2014-02-01

210

Glycosylated hemoglobin: colorimetric vs chromatographic measurement.  

PubMed

Glycosylated hemoglobin (GHb) was measured by a chromatographic method using HPLC (HbA1c) as well as a colorimetric method using thiobarbituric acid (TBA) on samples collected from 40 diabetic subjects. GHb measured by HPLC correlated well with the colorimetric method (r = 0.7). Freezing the samples caused an immediate increase of the HbA1a+b but not the HbA1c results. 4 weeks storage of the red cells at room temperature, 4 degrees C or -20 degrees C altered the results of GHb measured by HPLC but not the TBA reaction. Half of the total ketoamine linked hexoses detected by the TBA reaction was found in the HbA0 fraction as measured by ion exchange chromatography. The colorimetric method (r = 0.53) had better correlation than the HPLC method (r = 0.27) with mean blood glucose values during the 4 weeks preceding sample collection. GHb measured by the TBA reaction more accurately represents the ketoamine linked sugar in hemoglobin, is less subject to handling artifacts and more accurately reflects the blood glucose values during the preceding 4 weeks. PMID:3780136

Shah, S C; Malone, J I; Harvey, C

1986-09-01

211

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

212

Direct fast neutron detection: A status report  

SciTech Connect

This report describes the status of efforts to develop direct fast-neutron detection via proton recoil within plastic scintillator. Since recording proton recoil events is of little practical use without a means to discriminate effectively against gamma-ray interactions, the present effort is concentrated on demonstrating a method that distinguishes between pulse types. The proposed method exploits the different pulse shapes that are to be expected primarily on the basis of the slower speed of the recoiling fission neutrons. Should this effort ultimately prove successful, the resulting novel technology will have the potential to significantly lower cost and increase capability for a number of critical neutron-detection applications. Considerable progress has been made toward a clear and compelling demonstration of this new technique. An exhaustive theoretical and numerical investigation of the method has been completed. The authors have been able to better understand the laboratory results and estimate the performance that could ultimately be achieved using the proposed technique. They have assessed the performance of a number of different algorithms for discriminating between neutron and gamma ray events. The results of this assessment will be critical when the construction of low-cost, field-portable neutron detectors becomes necessary. Finally, a laboratory effort to realize effective discrimination is well underway and has resulted in partial success.

Peurrung, A.J.; Hansen, R.R.; Craig, R.A.; Hensley, W.K.; Hubbard, C.W.; Keller, P.E.; Reeder, P.L.; Sunberg, D.S.

1997-12-01

213

Colorimetric Method for Determining MICs of Antimicrobial Agents forMycobacterium tuberculosis  

Microsoft Academic Search

for 29 (58%), 14 (28%), and 7 (14%) of the 50 strains, respectively. When MIC susceptibility results were compared with results obtained by the agar proportion method, increased levels of resistance detected by agar proportion were associated with higher MICs obtained by the colorimetric method. Tentative interpretive criteria for colorimetric MIC results which showed good agreement with results obtained by

DAVID M. YAJKO; JANUSZ J. MADEJ; MICHAEL V. LANCASTER; CYNTHIA A. SANDERS; V. LOUISE CAWTHON; BETTY GEE; ANNA BABST

1995-01-01

214

Direct colorimetric detection of copper(II) ions in sampling using diffusive gradients in thin-films  

Microsoft Academic Search

A novel binding phase was developed for use in diffusive gradients in thin-film (DGT) sampling for Cu(II) by employing methylthymol blue as a chelating and chromogenic agent. Methylthymol blue was adsorbed onto beads of Dowex 1×8 resin (200–400 mesh) and the resin beads were then immobilised onto an adhesive disc. Analysis of exposed binding discs by either UV–vis spectrophotometry or

Russell W. McGifford; Andrew J. Seen; Paul R. Haddad

2010-01-01

215

Switchable reporter enzymes based on mutually exclusive domain interactions allow antibody detection directly in solution  

PubMed Central

Detection of antibodies is essential for the diagnosis of many diseases including infections, allergies and autoimmune diseases. Current heterogeneous immunoassays require multiple time-consuming binding and washing steps, which limits their application in point-of-care diagnostics and high-throughput screening. Here we report switchable reporter enzymes that allow simple colorimetric detection of antibodies directly in solution. Our approach is based on the antibody-induced disruption of an intramolecular interaction between TEM1-?-lactamase and its inhibitor protein BLIP. Using the HIV1-p17 antibody as an initial target, the interaction between enzyme and inhibitor was carefully tuned to yield a reporter enzyme whose activity increased 10-fold in the presence of pM antibody concentrations. Reporter enzymes for two other antibodies (HA-tag and Dengue virus type I) were obtained by simply replacing the epitope sequences. This new sensor design represents a modular and generic approach to construct antibody reporter enzymes without the cumbersome optimization required by previous engineering strategies.

Banala, Sambashiva; Aper, Stijn J.A.; Schalk, Werner; Merkx, Maarten

2013-01-01

216

Switchable reporter enzymes based on mutually exclusive domain interactions allow antibody detection directly in solution.  

PubMed

Detection of antibodies is essential for the diagnosis of many diseases including infections, allergies, and autoimmune diseases. Current heterogeneous immunoassays require multiple time-consuming binding and washing steps, which limits their application in point-of-care diagnostics and high-throughput screening. Here, we report switchable reporter enzymes that allow simple colorimetric detection of antibodies directly in solution. Our approach is based on the antibody-induced disruption of an intramolecular interaction between TEM1 ?-lactamase and its inhibitor protein BLIP. Using the HIV1-p17 antibody as an initial target, the interaction between enzyme and inhibitor was carefully tuned to yield a reporter enzyme whose activity increased 10-fold in the presence of pM antibody concentrations. Reporter enzymes for two other antibodies (HA-tag and Dengue virus type I) were obtained by simply replacing the epitope sequences. This new sensor design represents a modular and generic approach to construct antibody reporter enzymes without the cumbersome optimization required by previous engineering strategies. PMID:23941162

Banala, Sambashiva; Aper, Stijn J A; Schalk, Werner; Merkx, Maarten

2013-10-18

217

Direct Detection of Soil-Bound Prions  

PubMed Central

Scrapie and chronic wasting disease are contagious prion diseases affecting sheep and cervids, respectively. Studies have indicated that horizontal transmission is important in sustaining these epidemics, and that environmental contamination plays an important role in this. In the perspective of detecting prions in soil samples from the field by more direct methods than animal-based bioassays, we have developed a novel immuno-based approach that visualises in situ the major component (PrPSc) of prions sorbed onto agricultural soil particles. Importantly, the protocol needs no extraction of the protein from soil. Using a cell-based assay of infectivity, we also report that samples of agricultural soil, or quartz sand, acquire prion infectivity after exposure to whole brain homogenates from prion-infected mice. Our data provide further support to the notion that prion-exposed soils retain infectivity, as recently determined in Syrian hamsters intracerebrally or orally challanged with contaminated soils. The cell approach of the potential infectivity of contaminated soil is faster and cheaper than classical animal-based bioassays. Although it suffers from limitations, e.g. it can currently test only a few mouse prion strains, the cell model can nevertheless be applied in its present form to understand how soil composition influences infectivity, and to test prion-inactivating procedures.

Genovesi, Sacha; Leita, Liviana; Sequi, Paolo; Andrighetto, Igino; Sorgato, M. Catia; Bertoli, Alessandro

2007-01-01

218

Measurement of microbial activity in soil by colorimetric observation of in situ dye reduction: an approach to detection of extraterrestrial life  

PubMed Central

Background Detecting microbial life in extraterrestrial locations is a goal of space exploration because of ecological and health concerns about possible contamination of other planets with earthly organisms, and vice versa. Previously we suggested a method for life detection based on the fact that living entities require a continual input of energy accessed through coupled oxidations and reductions (an electron transport chain). We demonstrated using earthly soils that the identification of extracted components of electron transport chains is useful for remote detection of a chemical signature of life. The instrument package developed used supercritical carbon dioxide for soil extraction, followed by chromatography or electrophoresis to separate extracted compounds, with final detection by voltammetry and tandem mass-spectrometry. Results Here we used Earth-derived soils to develop a related life detection system based on direct observation of a biological redox signature. We measured the ability of soil microbial communities to reduce artificial electron acceptors. Living organisms in pure culture and those naturally found in soil were shown to reduce 2,3-dichlorophenol indophenol (DCIP) and the tetrazolium dye 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide inner salt (XTT). Uninoculated or sterilized controls did not reduce the dyes. A soil from Antarctica that was determined by chemical signature and DNA analysis to be sterile also did not reduce the dyes. Conclusion Observation of dye reduction, supplemented with extraction and identification of only a few specific signature redox-active biochemicals such as porphyrins or quinones, provides a simplified means to detect a signature of life in the soils of other planets or their moons.

Crawford, Ronald L; Paszczynski, Andrzej; Lang, Qingyong; Erwin, Daniel P; Allenbach, Lisa; Corti, Giancarlo; Anderson, Tony J; Cheng, I Francis; Wai, Chien; Barnes, Bruce; Wells, Richard; Assefi, Touraj; Mojarradi, Mohammad

2002-01-01

219

A colorimetric method for the quantitation of galacturonic acid  

Microsoft Academic Search

A simple, colorimetric assay that is specific for galacturonic acid is presented. The assay uses sulfuric acid, carbazole,\\u000a a controlled heat water bath, and a spectrophotometer. Galacturonic acid can be detected as free sugar or in polymer forms,\\u000a such as pectin.

Kimberley A. C. C. Taylor

1993-01-01

220

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

221

Ink-jet printed colorimetric gas sensors on plastic foil  

NASA Astrophysics Data System (ADS)

An all polymeric colorimetric gas sensor with its associated electronics for ammonia (NH3) detection targeting low-cost and low-power applications is presented. The gas sensitive layer was inkjet printed on a plastic foil. The use of the foil directly as optical waveguide simplified the fabrication, made the device more cost effective and compatible with large scale fabrication techniques, such as roll to roll processes. Concentrations of 500 ppb of NH3 in nitrogen with 50% of RH were measured with a power consumption of about 868 ?W in an optical pulsed mode of operation. Such sensors foresee applications in the field of wireless systems, for environmental and safety monitoring. The fabrication of the planar sensor was based on low temperature processing. The waveguide was made of PEN or PET foil and covered with an ammonia sensitive layer deposited by inkjet printing, which offered a proper and localized deposition of the film. The influence of the substrate temperature and its surface pretreatment were investigated to achieve the optimum deposition parameters for the printed fluid. To improve the light coupling from the light source (LED) to the detectors (photodiodes), polymeric micro-mirrors were patterned in an epoxy resin. With the printing of the colorimetric film and additive patterning of polymeric micro-mirrors on plastic foil, a major step was achieved towards the implementation of full plastic selective gas sensors. The combination with printed OLED and PPD would further lead to an integrated all polymeric optical transducer on plastic foil fully compatible with printed electronics processes.

Courbat, Jerome; Briand, Danick; de Rooij, Nico F.

2010-08-01

222

Directional Detection of a Neutron Source.  

National Technical Information Service (NTIS)

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 ran...

L. Forman P. E. Vanier

2006-01-01

223

Systematic aspects of direct extrasolar planet detection  

NASA Technical Reports Server (NTRS)

Using the first optical observatory in space, the Hubble Space Telescope, images of possible extrasolar planets will have poor contrast against the background of diffracted and scattered starlight. The very long exposure time required to achieve an adequate signal-to-noise ratio will make their detection infeasible. For a future telescope, a 16-fold increase in either the smoothness of the collecting area of the optics would reduce the exposure time to a tolerable value, but the contrast would remain low and the required photometric precision high. In this situation, the feasibility of detection would be contingent on the careful identification and control of systematic errors.

Brown, Robert A.

1988-01-01

224

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

225

Synthesis and Characterization of Colorimetric Metal Sensing Properties Based on Azo Chromophore Moiety  

Microsoft Academic Search

In this work, we have designed and synthesized a particular colorimetric dye sensor for the detection of heavy metal ions. Dye sensor, namely 4-hydroxy-3-(fluoro-phenyl-thiourea-N'-nitrilo-methylidynyl)-azobenzene was synthesized using 5-phenyldiazenyl salicylaldehyde and 4-phenylthiosemi carbazide. The dye sensor has promising properties which are applicable to detect and recognize the presence of heavy metal ions with colorimetric changing functions. Electron rich part in dye

Young-A Son; Young-Sung Kim; Sung-Hoon Kim; Do-Hyun Lee

2011-01-01

226

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

227

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

228

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

229

Colorimetric determination of citrulline residues in proteins.  

PubMed

A method is described for the direct colorimetric determination of citrulline residues in proteins based on the reaction with diacetylmonoxime in the presence of lower concentrations of sulfuric acid. The reduced sensitivity due to the lower acid concentration was overcome by the addition of ferric chloride which also contributed to the color stabilization. Insoluble proteins or proteins resulting in turbidity can be analyzed following partial hydrolysis of those with enzyme or acid. The molar absorption coefficient (epsilon) for citrulline at 464 nm was 2.8 x 10(4). The method enabled us to determine low levels of protein-bound citrulline which are beyond the limitations of conventional methods using an amino acid analyzer. We determined the citrulline contents in the cornified cells of the epidermis of newborn rats, as well as soybean trypsin inhibitor. PMID:9866712

Sugawara, K; Yoshizawa, Y; Tzeng, S; Epstein, W L; Fukuyama, K

1998-12-01

230

Colorimetric detection of copper and chloride in DMSO/H2O media using bromopyrogallol red as a chemosensor with analytical applications  

NASA Astrophysics Data System (ADS)

We report bromopyrogallol red (BPR) as an easily available dye for detection of copper and chloride with distinct visual color changes in DMSO/H2O (9:1 v/v). The chemosensor has a high chromogenic selectivity for Cu2+ over other cations with detection limit of 0.07 ?g mL-1. The obtained complex of Cu2+ with BPR displayed ability to detect Cl- up to 0.79 ?g mL-1 in DMSO/H2O (9:1 v/v) media over a large number of other anions. The linear dynamic ranges for the determinations of Cu2+ and Cl- were 0.53-14.60 and 6.00-36.00 ?g mL-1, respectively. This receptor was successfully applied for the determination of Cl- and Cu2+ in water samples.

Tavallali, Hossein; Deilamy Rad, Gohar; Parhami, Abolfath; Abbasiyan, Elham

2012-11-01

231

Colorimetric detection of copper and chloride in DMSO/H?O media using bromopyrogallol red as a chemosensor with analytical applications.  

PubMed

We report bromopyrogallol red (BPR) as an easily available dye for detection of copper and chloride with distinct visual color changes in DMSO/H(2)O (9:1 v/v). The chemosensor has a high chromogenic selectivity for Cu(2+) over other cations with detection limit of 0.07 ?g mL(-1). The obtained complex of Cu(2+) with BPR displayed ability to detect Cl(-) up to 0.79 ?g mL(-1) in DMSO/H(2)O (9:1v/v) media over a large number of other anions. The linear dynamic ranges for the determinations of Cu(2+) and Cl(-) were 0.53-14.60 and 6.00-36.00 ?g mL(-1), respectively. This receptor was successfully applied for the determination of Cl(-) and Cu(2+) in water samples. PMID:22750338

Tavallali, Hossein; Deilamy Rad, Gohar; Parhami, Abolfath; Abbasiyan, Elham

2012-11-01

232

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

233

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

234

Eco-friendly plasmonic sensors: using the photothermal effect to prepare metal nanoparticle-containing test papers for highly sensitive colorimetric detection.  

PubMed

Convenient, rapid, and accurate detection of chemical and biomolecules would be a great benefit to medical, pharmaceutical, and environmental sciences. Many chemical and biosensors based on metal nanoparticles (NPs) have been developed. However, as a result of the inconvenience and complexity of most of the current preparation techniques, surface plasmon-based test papers are not as common as, for example, litmus paper, which finds daily use. In this paper, we propose a convenient and practical technique, based on the photothermal effect, to fabricate the plasmonic test paper. This technique is superior to other reported methods for its rapid fabrication time (a few seconds), large-area throughput, selectivity in the positioning of the NPs, and the capability of preparing NP arrays in high density on various paper substrates. In addition to their low cost, portability, flexibility, and biodegradability, plasmonic test paper can be burned after detecting contagious biomolecules, making them safe and eco-friendly. PMID:22545942

Tseng, Shao-Chin; Yu, Chen-Chieh; Wan, Dehui; Chen, Hsuen-Li; Wang, Lon Alex; Wu, Ming-Chung; Su, Wei-Fang; Han, Hsieh-Cheng; Chen, Li-Chyong

2012-06-01

235

Directional detection as a strategy to discover Galactic Dark Matter  

NASA Astrophysics Data System (ADS)

Directional detection of Galactic Dark Matter is a promising search strategy for discriminating WIMP events from background. Technical progress on gaseous detectors and read-outs has permitted the design and construction of competitive experiments. However, to take full advantage of this powerful detection method, one need to be able to extract information from an observed recoil map to identify a WIMP signal. We present a comprehensive formalism, using a map-based likelihood method allowing to recover the main incoming direction of the signal and its significance, thus proving its Galactic origin. This is a blind analysis intended to be used on any directional data. Constraints are deduced in the (?,m) plane and systematic studies are presented in order to show that, using this analysis tool, unambiguous Dark Matter detection can be achieved on a large range of exposures and background levels.

Billard, J.; Mayet, F.; Macías-Pérez, J. F.; Santos, D.

2010-07-01

236

Development of a colorimetric test system for detection of point mutations via ligation of a tandem of short oligonucleotides on methacrylate beads  

Microsoft Academic Search

A new approach for detection of point mutations has been developed. The nonradioactive test system proposed is based on enzymatic\\u000a ligation of a tandem of three short oligonucleotides B?pN8+pN4+pN?8 Bio in the presence of a complementary DNA template. The 5?-terminal octanucleotide B?pN8 is immobilized on polymer methacrylate beads (B) and the 3?-terminal octanucleotide pN?8 Bio contains a biotin residue at

L. M. Skobeltsyna; D. V. Pyshnyi; I. G. Shishkina; D. R. Tabatadze; G. M. Dymshits; V. F. Zarytova; E. M. Ivanova

2000-01-01

237

Lightning Direction-Finding Systems for Forest Fire Detection.  

NASA Astrophysics Data System (ADS)

Extensive networks of magnetic direction-finding (DF) stations have been installed throughout the western United States and Alaska to facilitate early detection of lightning-caused fires. Each station contains a new wideband direction-finder that responds primarily to cloud-to-ground lightning and discriminates against cloud discharges and background noise. Good angle accuracy is obtained by measuring the lightning direction at just the time the return-stroke electro-magnetic field reaches its initial peak. Lightning locations are calculated from the intersections of direction vectors and/or from the ratio of signal strengths recorded simultaneously at two, three, or four DF sites. The development of these systems has proved to be a significant aid in the detection of lightning-caused fires and in fire weather forecasting.

Krider, E. P.; Noggle, R. C.; Pifer, A. E.; Vance, D. L.

1980-09-01

238

Maximum patch method for directional dark matter detection  

SciTech Connect

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 will measure both recoil energy and angle, based on the gaps between events in two-dimensional phase space.

Henderson, Shawn; Monroe, Jocelyn; Fisher, Peter [Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Laboratory for Nuclear Science, MIT Kavli Institute for Astrophysics and Space Research, Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

2008-07-01

239

An Introduction to Dark Matter Direct Detection Searches & Techniques  

NASA Astrophysics Data System (ADS)

Weakly Interacting Massive Particles (WIMPs), are a leading candidate for the dark matter that is observed to constitute ˜25% of the total mass-energy density of the Universe. The direct detection of relic WIMPs (those produced during the early moments of the Universe's expansion) is at the forefront of active research areas in particle astrophysics with a numerous international experimental collaborations pursuing this goal. This paper presents an overview of the theoretical and practical considerations common to the design and operation of direct detection experiments, as well as their unique features and capabilities.

Saab, T.

2013-12-01

240

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.

2014-01-01

241

Indicator approach to develop a chemosensor for the colorimetric sensing of thiol-containing water and its application for the thiol detection in plasma.  

PubMed

A strategy for the determination of the presence of thiol-containing amino acids was successfully established by simply assembling copper chloride and xylenol orange (3,3'-bis[N,N-bis(carboxymethyl)aminomethyl]-o-cresolsulfonephthalein trisodium salt; XO) in a 1 : 1 molar ratio in quasi-physiological water solution (pH 6.0). The copper(II)-XO ensemble was highly selective for thiol species such as cysteine, homocysteine, and glutathione without interference from other amino acids and could quantitatively detect thiol in the range from 10 to 200 ?M with a linear relationship having an average molar absorbance constant of 6530 L mol(-1) cm(-1) in pure water. The whole recognition process for thiol gave rise to a rapid visual color change from purple-red to yellow which can be observed simultaneously with the naked-eye. PMID:21373697

Huo, Fang-Jun; Yang, Yu-Tao; Su, Jing; Sun, Yuan-Qiang; Yin, Cai-Xia; Yan, Xu-Xiu

2011-05-01

242

Self-assembly of graphene oxide with a silyl-appended spiropyran dye for rapid and sensitive colorimetric detection of fluoride ions.  

PubMed

Fluoride ion (F(-)), the smallest anion, exhibits considerable significance in a wide range of environmental and biochemical processes. To address the two fundamental and unsolved issues of current F(-) sensors based on the specific chemical reaction (i.e., the long response time and low sensitivity) and as a part of our ongoing interest in the spiropyran sensor design, we reported here a new F(-) sensing approach that, via assembly of a F(-)-specific silyl-appended spiropyran dye with graphene oxide (GO), allows rapid and sensitive detection of F(-) in aqueous solution. 6-(tert-Butyldimethylsilyloxy)-1',3',3'-trimethylspiro [chromene- 2,2'-indoline] (SPS), a spiropyran-based silylated dye with a unique reaction activity for F(-), was designed and synthesized. The nucleophilic substitution reaction between SPS and F(-) triggers cleavage of the Si-O bond to promote the closed spiropyran to convert to its opened merocyanine form, leading to the color changing from colorless to orange-yellow with good selectivity over other anions. With the aid of GO, the response time of SPS for F(-) was shortened from 180 to 30 min, and the detection limit was lowered more than 1 order of magnitude compared to the free SPS. Furthermore, due to the protective effect of nanomaterials, the SPS/GO nanocomposite can function in a complex biological environment. The SPS/GO nanocomposite was characterized by XPS and AFM, etc., and the mechanism for sensing F(-) was studied by (1)H NMR and ESI-MS. Finally, this SPS/GO nanocomposite was successfully applied to monitoring F(-) in the serum. PMID:24164279

Li, Yinhui; Duan, Yu; Zheng, Jing; Li, Jishan; Zhao, Wenjie; Yang, Sheng; Yang, Ronghua

2013-12-01

243

Fast solid support detection of PCR amplified viral DNA sequences using radioiodinated or hapten labelled primers.  

PubMed

Oligonucleotides with novel modifications have been synthesized and incorporated into enzymatically amplified DNA sequences. They allow the fast detection of viral DNA sequences after two rounds of amplification. The hybrids formed are immobilized by affinity on coated tubes and detected by direct beta (32P) or gamma (125I) counting or by colorimetric revelation. The effect of a dilution step between the two amplifications is studied to obtain optimal sensitivity and specificity. This test is used to detect Human Papillomavirus types 16 and 18 in cells and biopsies and for the specific colorimetric detection of HIV1 in extracted DNA. PMID:2162518

Sauvaigo, S; Fouqué, B; Roget, A; Livache, T; Bazin, H; Chypre, C; Téoule, R

1990-06-11

244

Incorporation of the fluoride induced SiO 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 SiO bond and thus destroyed the outer protecting layer of the probe, and further triggered the aggregation of internal MPD-AuNPs by forming NHF 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?gmL(-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

245

Direct detection of reactive oxygen species ex vivo  

Microsoft Academic Search

Direct detection of reactive oxygen species ex vivo. Oxidative stress is thought to play an important role in the initiation and progression of renal, cardiovascular, neoplastic, and neurodegenerative diseases. It is also widely believed that oxidative stress is a main cause of aging. Although considerable progress has been made in the understanding of the sources and actions of oxidative stress,

Ralf P. Brandes; MARIANO JANISZEWSKI

2005-01-01

246

Direct detection of the inflationary gravitational-wave background  

SciTech Connect

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.

Smith, Tristan L.; Kamionkowski, Marc [California Institute of Technology, Mail Code 130-33, Pasadena, California 91125 (United States); Cooray, Asantha [California Institute of Technology, Mail Code 130-33, Pasadena, California 91125 (United States); Department of Physics and Astronomy, University of California, Irvine, Irvine, California 92697 (United States)

2006-01-15

247

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

248

Micromegas detector developments for Dark Matter directional detection with MIMAC  

NASA Astrophysics Data System (ADS)

The aim of the MIMAC project is to detect non-baryonic Dark Matter with a directional TPC using a high precision Micromegas readout plane. We will describe in detail the recent developments done with bulk Micromegas detectors as well as the characterisation measurements performed in an Argon(95%)-Isobutane(5%) mixture. Track measurements with alpha particles will be shown.

Iguaz, F. J.; Attié, D.; Calvet, D.; Colas, P.; Druillole, F.; Ferrer-Ribas, E.; Giomataris, I.; Mols, J. P.; Pancin, J.; Papaevangelou, T.; Billard, J.; Bosson, G.; Bouly, J. L.; Bourrion, O.; Fourel, Ch; Grignon, C.; Guillaudin, O.; Mayet, F.; Richer, J. P.; Santos, D.; Golabek, C.; Lebreton, L.

2011-07-01

249

A colorimetric "naked-eye" Cu(II) chemosensor and pH indicator in 100% aqueous solution.  

PubMed

A new, highly selective and sensitive colorimetric chemosensor 1 for detection of Cu(2+) ions in aqueous solution was developed. Receptor 1 detected Cu(2+) ions by changing its color from colorless to yellow. Moreover, the Cu(2+)-sensitive compound was used as a colorimetric pH detector based on a color change due to 1-Cu(2+) complex formation identifiable by the naked eye. PMID:24599223

Noh, Jin Young; Park, Gyeong Jin; Na, Yu Jeong; Jo, Hyun Yong; Lee, Seul Ah; Kim, Cheal

2014-04-21

250

Detection of laser optic defects using gradient direction matching  

NASA Astrophysics Data System (ADS)

That National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL) will be the world's largest and most energetic laser. It has thousands of optics and depends heavily on the quality and performance of these optics. Over the past several years, we have developed the NIF Optics Inspection Analysis System that automatically finds defects in a specific optic by analyzing images taken of that optic. This paper describes a new and complementary approach for the automatic detection of defects based on detecting the diffraction ring patterns in downstream optic images caused by defects in upstream optics. Our approach applies a robust pattern matching algorithm for images called Gradient Direction Matching (GDM). GDM compares the gradient directions (the direction of flow from dark to light) of pixels in a test image to those of a specified model and identifies regions in the test image whose gradient directions are most in line with those of the specified model. For finding rings, we use luminance disk models whose pixels have gradient directions all pointing toward the center of the disk. After GDM identifies potential rings locations, we rank these rings by how well they fit the theoretical diffraction ring pattern equation. We perform false alarm mitigation by throwing out rings of low fit. A byproduct of this fitting procedure is an estimate of the size of the defect and its distance from the image plane. We demonstrate the potential effectiveness of this approach by showing examples of rings detected in real images of NIF optics.

Chen, Barry Y.; Kegelmeyer, Laura M.; Liebman, Judith A.; Salmon, J. Thaddeus; Tzeng, Jack; Paglieroni, David W.

2006-03-01

251

Assessing the discovery potential of directional detection of dark matter  

NASA Astrophysics Data System (ADS)

There is a worldwide effort toward the development of a large time projection chamber devoted to directional dark matter detection. All current projects are being designed to fulfill a unique goal: identifying weakly interacting massive particle (WIMP) as such by taking advantage of the expected direction dependence of WIMP-induced events toward the constellation Cygnus. However, such proof of discovery requires a careful statistical data treatment. In this paper, the discovery potential of forthcoming directional detectors is addressed by using a frequentist approach based on the profile likelihood ratio test statistic. This allows us to estimate the expected significance of a dark matter detection taking into account astrophysical and experimental uncertainties. We show that the energy threshold and the background contamination are key experimental issues for directional detection, while angular resolution and sense recognition efficiency only mildly affect the sensitivity and the energy resolution is unimportant. This way, we found that a 30 kg.year CF4 directional experiment could reach a 3? sensitivity at 90% C.L. down to 10-5pb and 3.10-4pb for the WIMP-proton axial cross section in the most optimistic and pessimistic detector performance case, respectively.

Billard, J.; Mayet, F.; Santos, D.

2012-02-01

252

Direct Detection of Sub-GeV Dark Matter  

SciTech Connect

Direct detection strategies are proposed for dark matter particles with MeV to GeV mass. In this largely unexplored mass range, dark matter scattering with electrons can cause single-electron ionization signals, which are detectable with current technology. Ultraviolet photons, individual ions, and heat are interesting alternative signals. Focusing on ionization, we calculate the expected dark matter scattering rates and estimate the sensitivity of possible experiments. Backgrounds that may be relevant are discussed. Theoretically interesting models can be probed with existing technologies, and may even be within reach using ongoing direct detection experiments. Significant improvements in sensitivity should be possible with dedicated experiments, opening up a window to new regions in dark matter parameter space.

Essig, Rouven; Mardon, Jeremy; Volansky, Tomer

2012-03-20

253

Direct Fast-Neutron Detection: A Progress Report  

SciTech Connect

It is widely acknowledged that Mure neutron-detection technologies will need to offer increased performance at lower cost. One clear route toward these goals is rapid and direct detection of fast neutrons prior to moderation. This report describes progress to date in an effort to achieve such neutron detection via proton recoil within plastic scintillator. Since recording proton-recoil events is of little practical use without a means to discriminate effectively against gamma-ray interactions, the present effort is concentrated on demonstrating a method that distinguishes between pulse types. The proposed method exploits the substantial difference in the speed of fission neutrons and gamma-ray photons. Should this effort ultimately prove successful, the resulting. technology would make a valuable contribution toward meeting the neutron-detection needs of the next century. This report describes the detailed investigations that have been part of Pacific Northwest National Laborato@s efforts to demonstrate direct fast-neutron detection in the laboratory. Our initial approach used a single, solid piece of scintillator along with the electronics needed for pulse-type differentiation. Work to date has led to the conclusion that faster scintillator and/or faster electronics will be necessary before satisfactory gamma-ray discrimination is achieved with this approach. Acquisition and testing of both faster scintillator and faster electronics are currently in progress. The "advanced" approach to direct fast-neutron detection uses a scintillating assembly with an overall density that is lower than that of ordinary plastic scintillator. The lower average density leads to longer interaction times for both neutrons and gamma rays, allowing easier discrimination. The modeling, optimization, and design of detection systems using this approach are described in detail.

AJ Peurrung; DC Stromswold; PL Reeder; RR Hansen

1998-10-18

254

NBD-based colorimetric and fluorescent turn-on probes for hydrogen sulfide.  

PubMed

Hydrogen sulfide (H2S) is an important endogenous signalling molecule and also an important environmental target for detection. New reaction-based colorimetric and fluorescent turn-on probes based on selective thiolyling of NBD (7-nitro-1,2,3-benzoxadiazole) ether were explored for sensing of H2S in aqueous buffer. The syntheses of both probes are simple and quite straightforward. The probes are highly sensitive and selective toward H2S over other biologically relevant species. Probe 1 can be used to directly visualize H2S by the naked eye and shows more than 1000-fold fluorescence increase upon reaction with H2S. Probe 2 is a near-infrared fluorescent sensor for H2S at physiological pH. PMID:24276473

Wei, Chao; Zhu, Qing; Liu, Weiwei; Chen, Wenbin; Xi, Zhen; Yi, Long

2014-01-21

255

Directional Detection of Fast Neutrons Using a Time Projection Chamber  

SciTech Connect

Spontaneous fission in Special Nuclear Material (SNM) such as plutonium and highly enriched uranium (HEU) results in the emission of neutrons with energies in the MeV range (hereafter 'fast neutrons'). These fast neutrons are largely unaffected by the few centimeters of intervening high-Z material that would suffice for attenuating most emitted gamma rays, while tens of centimeters of hydrogenous materials are required to achieve substantial attenuation of neutron fluxes from SNM. Neutron detectors are therefore an important complement to gamma-ray detectors in SNM search and monitoring applications. The rate at which SNM emits fast neutrons varies from about 2 per kilogram per second for typical HEU to some 60,000 per kilogram per second for metallic weapons grade plutonium. These rates can be compared with typical sea-level (cosmogenic) neutron backgrounds of roughly 5 per second per square meter per steradian in the relevant energy range [1]. The fact that the backgrounds are largely isotropic makes directional neutron detection especially attractive for SNM detection. The ability to detect, localize, and ultimately identify fast neutron sources at standoff will ultimately be limited by this background rate. Fast neutrons are particularly well suited to standoff detection and localization of SNM or other fast neutrons sources. Fast neutrons have attenuation lengths of about 60 meters in air, and retain considerable information about their source direction even after one or two scatters. Knowledge of the incoming direction of a fast neutron, from SNM or otherwise, has the potential to significantly improve signal to background in a variety of applications, since the background arriving from any one direction is a small fraction of the total background. Imaging or directional information therefore allows for source detection at a larger standoff distance or with shorter dwell times compared to nondirectional detectors, provided high detection efficiency can be maintained. Directional detection of neutrons has been previously considered for applications such as controlled fusion neutron imaging [2], nuclear fuel safety research [3], imaging of solar neutrons and SNM [4], and in nuclear science [5]. The use of scintillating crystals and fibers has been proposed for directional neutron detection [6]. Recently, a neutron scatter camera has been designed, constructed, and tested for imaging of fast neutrons, characteristic for SNM material fission [7]. The neutron scatter camera relies on the measurement of the proton recoil angle and proton energy by time of flight between two segmented solid-state detectors. A single-measurement result from the neutron scatter camera is a ring containing the possible incident neutron direction. Here we describe the development and commissioning of a directional neutron detection system based on a time projection chamber (TPC) detector. The TPC, which has been widely used in particle and nuclear physics research for several decades, provides a convenient means of measuring the full 3D trajectory, specific ionization (i.e particle type) and energy of charged particles. For this application, we observe recoil protons produced by fast neutron scatters on protons in hydrogen or methane gas. Gas pressures of a few ATM provide reasonable neutron interaction/scattering rates.

Bowden, N; Heffner, M; Carosi, G; Carter, D; Foxe, M; Jovanovic, I

2009-06-03

256

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

257

Functional self-assembling bolaamphiphilic polydiacetylenes as colorimetric sensor scaffolds.  

PubMed

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 by 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. PMID:15238003

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

2004-07-14

258

Colorimetric Analysis of Ammonia in Water.  

National Technical Information Service (NTIS)

An accurate, reliable method of determing concentration of ammonia in water solution was developed using colorimetric techniques. The procedure involves formation of a colored complex of ammonia with 2,5-dimethoxyoxolane and (E)-p-dimethylamino-cinnamalde...

F. W. Carson R. L. Gross

1977-01-01

259

A Colorimetric Method for Determination of Saxitoxin.  

National Technical Information Service (NTIS)

Saxitoxin, the paralytic shellfish poison, can be conveniently determined by colorimetry after hydrogen peroxide oxidation and reaction of the resultant guanidine with biacetyl. This colorimetric method has been used to assay saxitoxin quantitatively at c...

R. M. Gershey R. A. Neve D. L. Musgrave P. B. Reichardt

1977-01-01

260

Comparison of hemagglutination inhibition assay, an ELISA-based micro-neutralization assay and colorimetric microneutralization assay to detect antibody responses to vaccination against influenza A H1N1 2009 virus  

Microsoft Academic Search

The hemagglutination inhibition (HI) assay has been the main method used to investigate immune responses to vaccination against influenza H1N1 (2009) virus. However microneutralization tests (MNT) have been shown to be more sensitive and more specific. In this study, the three methods of choice: (i) the HI assay, (ii) an ELISA-based conventional MNT and (iii) a colorimetric MNT in terms

S. Grund; O. Adams; S. Wählisch; B. Schweiger

2011-01-01

261

Future directions for H sub x O sub y detection  

NASA Technical Reports Server (NTRS)

The activities and recommendations of the NASA workshop on the Future Directions for H sub x O sub y detection are given. The objective of this workshop was to access future directions for the measurement of the OH radical as well as other H sub x O sub y species. The workshop discussions were focused by two broad questions: (1) What are the capabilities of potential measurement methods? and (2) Will the results from the most promising method be useful in furthering understanding of tropospheric chemistry?

Crosley, David R. (editor); Hoell, James M. (editor)

1986-01-01

262

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

263

Review of Dark Matter Direct Detection Using Cryogenic Detectors  

SciTech Connect

The direct detection of the Universe's Dark Matter is one of the key questions in particle astrophysics. Cryogenic based detectors offer advantages in low radioactive backgrounds, target mass, sensitivity to the small energy depositions and rejection of possible background sources. I will summarize the main experimental approaches, including both cryogenic crystal and liquid targets and the options pursued for their signal readout. Recent advances from around the world and prospects for future proposed experiments will be discussed.

Brink, P.L.; /SLAC

2012-06-13

264

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.

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

265

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

266

New method for analyzing dark matter direct detection data  

NASA Astrophysics Data System (ADS)

The experimental situation of dark matter direct detection has reached an exciting crossroads, with potential hints of a discovery of dark matter (DM) from the CDMS, CoGeNT, CRESST-II and DAMA experiments in tension with null results from xenon-based experiments such as XENON100 and LUX. Given the present controversial experimental status, it is important that the analytical method used to search for DM in direct detection experiments is both robust and flexible enough to deal with data for which the distinction between signal and background points is difficult, and hence where the choice between setting a limit or defining a discovery region is debatable. In this article we propose a novel (Bayesian) analytical method, which can be applied to all direct detection experiments and which extracts the maximum amount of information from the data. We apply our method to the XENON100 experiment data as a worked example, and show that firstly our exclusion limit at 90% confidence is in agreement with their own for the 225 live days data, but is several times stronger for the 100 live days data. Secondly we find that, due to the two points at low values of S1 and S2 in the 225 days data set, our analysis points to either weak consistency with low-mass dark matter or the possible presence of an unknown background. Given the null result from LUX, the latter scenario seems the more plausible.

Davis, Jonathan H.; Enßlin, Torsten; BÅ`hm, Céline

2014-02-01

267

Direct detection portals for self-interacting dark matter  

NASA Astrophysics Data System (ADS)

Dark matter self-interactions can affect the small scale structure of the Universe, reducing the central densities of dwarfs and low surface brightness galaxies in accord with observations. From a particle physics point of view, this points toward the existence of a 1-100 MeV particle in the dark sector that mediates self-interactions. Since mediator particles will generically couple to the Standard Model, direct detection experiments provide sensitive probes of self-interacting dark matter. We consider three minimal mechanisms for coupling the dark and visible sectors: photon kinetic mixing, Z boson mass mixing, and the Higgs portal. Self-interacting dark matter motivates a new benchmark paradigm for direct detection via momentum-dependent interactions, and ton-scale experiments will cover astrophysically motivated parameter regimes that are unconstrained by current limits. Direct detection is a complementary avenue to constrain velocity-dependent self-interactions that evade astrophysical bounds from larger scales, such as those from the bullet cluster.

Kaplinghat, Manoj; Tulin, Sean; Yu, Hai-Bo

2014-02-01

268

APIC. Absolute Position Interfero-Coronagraph for direct exoplanet detection  

NASA Astrophysics Data System (ADS)

Context: For detecting and directly imaging exoplanets, coronagraphic methods are mandatory when the intensity ratio between a star and its orbiting planet can be as large as 10^6. In 1996, a concept of an achromatic interfero-coronagraph (AIC) was presented for detecting very faint stellar companions, such as exoplanets. Aims: We present a modified version of the AIC not only permitting these faint companions to be detected but also their relative position to be determined with respect to the parent star, a problem that was not solved in the original design of the AIC. Methods: In our modified design, two cylindrical lens doublets were used to remove the 180° ambiguity introduced by the AIC's original design. Results: Our theoretical study and the numerical computations show that the axis of symmetry is destroyed when one of the cylindrical doublets is rotated around the optical axis.

Allouche, F.; Glindemann, A.; Aristidi, E.; Vakili, F.

2009-06-01

269

Spectrally efficient optical transmission based on Stokes vector direct detection.  

PubMed

We propose a novel detection scheme called Stokes vector direct detection (SV-DD) to realize high electrical spectral efficiency and cost-effective optical communication for short and medium reach. With SV-DD, the signal is modulated in only one polarization and combined with the carrier in the orthogonal polarization for fiber transmission. At reception, the combined signal is detected in Stokes space by three or four photo-detectors. Compared with conventional DD technique, SV-DD is resilient to both chromatic dispersion and signal-to-signal beat noise. Furthermore, SV-DD does not require polarization tracking or narrow band optical filtering for carrier extraction. In this paper, we present for the first time the numerical analysis and experimental demonstration of single-carrier SV-DD. We report 62.5-Gb/s data rate single-carrier SV-DD transmission over 160-km SSMF using 12.5-Gbaud 32-QAM modulation. PMID:24977825

Li, An; Che, Di; Chen, Vivian; Shieh, William

2014-06-30

270

Direct detection of black holes via electromagnetic radiation  

NASA Astrophysics Data System (ADS)

Many black hole (BH) candidates exist, ranging from supermassive (˜106-1010 M?) to stellar masses (˜1-100 M?), all of them identified by indirect processes. Although there are no known candidate BHs with substellar masses, these might have been produced in the primordial Universe. BHs emit radiation composed of photons, gravitons and, later in their lives, massive particles. We explored the detection of such BHs with present-day masses from 10-22 to 10-11 M?. We determined the maximum distances (d) at which the current best detectors should be placed in order to identify such isolated BHs. Broadly, we conclude that in the visible and ultraviolet BHs can be directly detected at d ? 107 m while in the X-ray band the distances might reach ˜108 m (of the order of the Earth-Moon distance) and in the ?-ray band BHs might even be detected from as far as ˜0.1 pc. Since these results give us realistic hopes of directly detecting BHs, we suggest the scrutiny of current and future space mission data to reach this goal.

Sobrinho, J. L. G.; Augusto, P.

2014-07-01

271

Detecting modulated lasers in the battlefield and determining their direction  

NASA Astrophysics Data System (ADS)

Many different lasers are deployed in the battlefield for range finding, target designation, communications, dazzle, location of targets, munitions guidance, and destruction. Laser warning devices on military systems detect and identify lasers striking them in order to assess their threat level and plan avoidance or retaliation. Types of lasers and their characteristics are discussed: power, frequency, coherence, bandwidth, direction, pulse length and modulation. We describe three approaches for laser warning devices from which specific cases may be tailored: simultaneous estimation of direction and wavelength with a grating, wavefront direction only estimation for low light levels with lenses, absolute simultaneous wavelength only estimation with a Fizeau interferometer. We investigate the feasibility and compare the suitability of these approaches for different applications.

McAulay, Alastair D.

2009-05-01

272

A colorimetric sensor array of porous pigments  

PubMed Central

The development of a low-cost, simple colorimetric sensor array capable of detection and identification of toxic gases is reported. This technology uses a disposable printed array of porous pigments in which metalloporphyrins and chemically responsive dyes are immobilized in a porous matrix of organically modified siloxanes (ormosils) and printed on a porous membrane. The printing of the ormosil into the membrane is highly uniform and does not lessen the porosity of the membrane, as shown by scanning electron microscopy. When exposed to an analyte, these pigments undergo reactions that result in well-defined color changes due to strong chemical interactions: ligation to metal ions, Lewis or Bronsted acid-base interactions, hydrogen bonding, etc. Striking visual identification of 3 toxic gases has been shown at the IDLH (immediately dangerous to life and health), at the PEL (permissible exposure level), and at a level well below the PEL. Identification and quantification of analytes were achieved using the color change profiles, which were readily distinguishable in a hierarchical clustering analysis (HCA) dendrogram, with no misclassifications in 50 trials.

Lim, Sung H.; Kemling, Jonathan W.; Feng, Liang

2010-01-01

273

A colorimetric sensor array of porous pigments.  

PubMed

The development of a low-cost, simple colorimetric sensor array capable of the detection and identification of toxic gases is reported. This technology uses a disposable printed array of porous pigments in which metalloporphyrins and chemically-responsive dyes are immobilized in a porous matrix of organically modified siloxanes (ormosils) and printed on a porous membrane. The printing of the ormosil into the membrane is highly uniform and does not lessen the porosity of the membrane, as shown by scanning electron microscopy. When exposed to an analyte, these pigments undergo reactions that result in well-defined color changes due to strong chemical interactions: ligation to metal ions, Lewis or Brønsted acid-base interactions, hydrogen bonding, etc. Striking visual identification of 3 toxic gases has been shown at the IDLH (immediately dangerous to life and health) concentration, at the PEL (permissible exposure level), and at a level well below the PEL. Identification and quantification of analytes were achieved using the color change profiles, which were readily distinguishable in a hierarchical clustering analysis (HCA) dendrogram, with no misclassifications in 50 trials. PMID:19918616

Lim, Sung H; Kemling, Jonathan W; Feng, Liang; Suslick, Kenneth S

2009-12-01

274

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

275

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

276

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

277

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

278

A simplified colorimetric method for the measurement of glycosylated hemoglobin.  

PubMed

A colorimetric method for the measurement of glycosylated hemoglobin is described. The method is based on the detection of hydroxymethylfurfural liberated from the ketoamine-linked hexose of glycosylated hemoglobin. Rapid hydrolysis is achieved by heating at 120-124 degrees C under pressure, and simplification of the procedure enables the test to be performed in one disposable test tube. Standardization is by means of easily prepared lyophilized human hemoglobin preparations. The test has proven to be reliable and economical in routine use. PMID:6674873

Nicol, D J; Davis, R E; Curnow, D H

1983-10-01

279

Direct detection of alpha synuclein oligomers in vivo  

PubMed Central

Background Rat models of Parkinson’s disease are widely used to elucidate the mechanisms underlying disease etiology or to investigate therapeutic approaches. Models were developed using toxins such as MPTP or 6-OHDA to specifically target dopaminergic neurons resulting in acute neuronal loss in the substantia nigra or by using viral vectors to induce the specific and gradual expression of alpha synuclein in the substantia nigra. The detection of alpha- synuclein oligomers, the presumed toxic species, in these models and others has been possible using only indirect biochemical approaches to date. Here we coinjected AAVs encoding alpha-synuclein fused to the N- or C-terminal half of VenusYFP in rat substantia nigra pars compacta and describe for the first time a novel viral vector rodent model with the unique ability to directly detect and track alpha synuclein oligomers ex vivo and in vivo. Results Viral coinjection resulted in widespread VenusYFP signal within the nigrostriatal pathway, including cell bodies in the substantia nigra and synaptic accumulation in striatal terminals, suggestive of in vivo alpha-synuclein oligomers formation. Transduced rats showed alpha-synuclein induced dopaminergic neuron loss in the substantia nigra, the appearance of dystrophic neurites, and gliosis in the striatum. Moreover, we have applied in vivo imaging techniques in the living mouse to directly image alpha-synuclein oligomers in the cortex. Conclusion We have developed a unique animal model that provides a tool for the Parkinson’s disease research community with which to directly detect alpha- synuclein oligomers in vivo and screen therapeutic approaches targeting alpha-synuclein oligomers.

2013-01-01

280

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

281

Ultrabroadband direct detection of nonclassical photon statistics at telecom wavelength  

NASA Astrophysics Data System (ADS)

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.

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

2014-04-01

282

Optical filtering in directly modulated/detected OOFDM systems.  

PubMed

This work presents a theoretical investigation on the performance of directly modulated/detected (DM/DD) optical orthogonal frequency division multiplexed (OOFDM) systems subject to optical filtering. The impact of both linear and nonlinear distortion effects are taken into account to calculate the effective signal-to-noise ratio of each subcarrier. These results are then employed to optimize the design parameters of two simple optical filtering structures: a Mach Zehnder interferometer and a uniform fiber Bragg grating, leading to a significant optical power budget improvement given by 3.3 and 3dB, respectively. These can be further increased to 5.5 and 4.2dB respectively when balanced detection configurations are employed. We find as well that this improvement is highly dependent on the clipping ratio. PMID:24514636

Sánchez, C; Ortega, B; Wei, J L; Capmany, J

2013-12-16

283

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.

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

2014-01-01

284

Direct Hydrocarbon Detection Using Multi-channel Transient Electromagnetics  

NASA Astrophysics Data System (ADS)

We present a transient electromagnetic method for the detection of hydrocarbons and for monitoring their movement within a reservoir. Replacement of brine by gas or oil can cause a change in electrical resistivity of a porous rock of as much as 4 orders of magnitude. Seismic methods on the other hand are generally poor at detecting fluid content because the fluid content of a media has only a slight effect on its acoustic impedance. The data presented in this paper were collected as part of two Multi-channel Transient ElectroMagnetic (MTEM) surveys carried out in 1994 and 1996 over an underground gas storage reservoir at St. Illiers la Ville in France. The reservoir is a 30% porosity sandstone anticline about 30m thick at a depth of around 700m. In the summer gas is pumped in and the gas-water contact falls; in the winter gas is extracted and the gas- water contact rises. The position of the contact is known from constant monitoring at over 40 wells. The surveys had two objectives: first, to attempt to detect the reservoir directly from the data; second, to detect the movement of the gas water contact be- tween the 2 survey times. A recent breakthrough in the understanding of the system has allowed both these objectives to be achieved.

Hobbs, B. A.; Ziolkowski, A. M.; Wright, D. A.

285

Highly selective colorimetric sensing of Cu(II) ions in aqueous solution via modulation of intramolecular charge transfer transition of aminonaphthoquinone chemosensor  

NASA Astrophysics Data System (ADS)

An aminonaphthoquinone based colorimetric chemosensor has been developed and demonstrated for the highly selective detection of Cu(II) ions in aqueous solution. The intramolecular charge transfer (ICT) transition exits in amine moiety directly attached to the quinone ring is modulated by the d-d transition of a square planar Cu(II)-receptor complex resulting in a change of color from yellow to blue. No significant color change was observed upon addition of other selected metal ions. The sensing property has been investigated using various spectral techniques (UV-Vis, fluorescence) and product analysis (Elemental analysis, magnetic moment, UV-Vis, FT-IR, EPR).

Madhupriya, Selvaraj; Elango, Kuppanagounder P.

2012-11-01

286

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

287

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

288

Direct detection experiments explained with mirror dark matter  

NASA Astrophysics Data System (ADS)

Recently, the CDMS/Si experiment has observed a low energy excess of events in their dark matter search. In light of this new result we update the mirror dark matter explanation of the direction detection experiments. We find that the DAMA, CoGeNT, CRESST-II and CDMS/Si data can be simultaneously explained by halo ?Fe? interactions provided that vrot?200 km/s. Other parameter space is also possible. Forthcoming experiments, including CDMSlite, CDEX, COUPP, LUX, C-4, … should be able to further scrutinize mirror dark matter and closely related hidden sector models in the near future.

Foot, R.

2014-01-01

289

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

290

Active THz medical imaging using broadband direct detection  

NASA Astrophysics Data System (ADS)

Research in THz imaging is generally focused on three primary application areas: medical, security, and nondestructive evaluation (NDE). While work in THz security imaging and personnel screening is populated by a number of different active and passive system architectures, research in medical imaging in is generally performed with THz time-domain systems. These systems typically employ photoconductive or electro-optic source/detector pairs and can acquire depth resolved data or spectrally resolved pixels by synchronously sampling the electric field of the transmitted/reflected waveform. While time-domain is a very powerful scientific technique, results reported in the literature suggest that desired THz contrast in medical imaging may not require the volume of data accessible from time-resolved measurements and that a simpler direct detection, active technique may be sufficient for specific applications. In this talk we discuss an active direct detection reflectometer system architecture operating at a center frequency of ~ 525 GHz that uses a photoconductive source and schottky diode detector. This design takes advantage or radar-like pulse rectification and novel reflective optical design to achieve high target imaging contrast with significant potential for high speed acquisition time. Results in spatially resolved hydration mapping of burn wounds are presented and future outlooks discussed.

Taylor, Zachary D.; Garritano, James; Tewari, Priyamvada; Diebold, Eric; Sung, Shijun; Bajwa, Neha; Nowroozi, Bryan; Stojadinovic, Alexander; Llombart, Nuria; Brown, Elliott R.; Grundfest, Warren S.

2013-03-01

291

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

292

Simple flow injection system for colorimetric determination of iodate in iodized salt  

Microsoft Academic Search

This work presents a flow injection (FI) system that was developed for determination of iodate. The system utilizes the oxidation of iodide by the analyte to iodine, which subsequently forms tri-iodide. In the presence of starch, the blue I3?–starch complex is developed within the sample zone and can be colorimetrically detected at 590 nm. Optimization was carried out to make

N Choengchan; K Uraisin; K Choden; W Veerasai; Kate Grudpan; D Nacapricha

2002-01-01

293

Evaluation of a Colorimetric PCR-Based Assay To Diagnose Plasmodium falciparum Malaria in Travelers  

Microsoft Academic Search

New diagnostic tests are needed to facilitate the diagnosis of Plasmodium falciparum malaria in the returned traveler. We performed a blinded evaluation of a nonisotopic colorimetric PCR-based assay (Digene SHARP Signal System) and compared the results with those obtained by microscopy and nested PCR for the detection of P. falciparum malaria in 150 febrile travelers. By using nested PCR as

KATHLEEN J. Y. ZHONG; KEVIN C. KAIN

1999-01-01

294

Spectroscopic direct detection of reflected light from extrasolar planets  

NASA Astrophysics Data System (ADS)

At optical wavelengths, an exoplanet's signature is essentially reflected light from the host star - several orders of magnitude fainter. Since it is superimposed on the star spectrum its detection has been a difficult observational challenge. However, the development of a new generation of instruments like Echelle Spectrograph for Rocky Exoplanets and Stable Spectroscopic Observations (ESPRESSO) and next-generation telescopes like the European Extremely Large Telescope (E-ELT) put us in a privileged position to detect these planets' reflected light as we will have access to extremely high signal-to-noise ratio spectra. With this work, we propose an alternative approach for the direct detection of the reflected light of an exoplanet. We simulated observations with ESPRESSO at Very Large Telescope (VLT) and high-resolution spectrograph (HIRES) at E-ELT of several star+planet systems, encompassing 10 h of the most favourable orbital phases. To the simulated spectra we applied the cross-correlation function to operate in a much higher signal-to-noise ratio domain than when compared with the spectra. The use of the cross-correlation function permitted us to recover the simulated planet signals at a level above 3?noise significance on several prototypical (e.g. Neptune-type planet with a 2 d orbit with the VLT at 4.4?noise significance) and real planetary systems (e.g. 55 Cnc e with the E-ELT at 4.9?noise significance). Even by using a more pessimistic approach to the noise level estimation, where systematics in the spectra increase the noise 2-3 times, the detection of the reflected light from large close-orbit planets is possible. We have also shown that this kind of study is currently within reach of current instruments and telescopes (e.g. 51 Peg b with the VLT at 5.2?noise significance), although at the limit of their capabilities.

Martins, J. H. C.; Figueira, P.; Santos, N. C.; Lovis, C.

2013-12-01

295

Ion-directed assembly of gold nanorods: a strategy for mercury detection.  

PubMed

Water-soluble gold nanorods (Au NRs) have been functionalized with an N-alkylaminopyrazole ligand, 1-[2-(octylamino)ethyl]-3,5-diphenylpyrazole (PyL), that has been demonstrated able to coordinate heavy metal ions. The N-alkylaminopyrazole functionalized Au NRs have been characterized by electron microscopy and spectroscopic investigation and tested in optical detection experiments of different ions, namely, Zn(2+), Cd(2+), Hg(2+), Cu(2+), Pb(2+), and As(3+). In particular, the exposure of the functionalized NRs to increasing amounts of Hg(2+) ions has resulted in a gradual red-shift and broadening of the longitudinal plasmon band, up to 900 nm. Interestingly, a significantly different response has been recorded for the other tested ions. In fact, no significant shift in the longitudinal plasmon band has been observed for any of them, while a nearly linear reduction in the plasmon band intensity versus ion concentration in solution has been detected. The very high sensitivity for Hg(2+) with respect to other investigated ions, with a limit of detection of 3 ppt, demonstrates that the functionalization of Au NRs with PyL is a very effective method to be implemented in a reliable colorimetric sensing device, able to push further down the detection limit achieved by applying similar strategies to spherical Au NPs. PMID:23305173

Placido, Tiziana; Aragay, Gemma; Pons, Josefina; Comparelli, Roberto; Curri, M Lucia; Merkoçi, Arben

2013-02-01

296

Direct detection of dark matter in universal bound states  

NASA Astrophysics Data System (ADS)

We study the signatures for internal structure of dark matter in direct detection experiments in the context of asymmetric self-interacting dark matter. The self-interaction cross section of two dark matter particles at low energies is assumed to come close to saturating the S-wave unitarity bound, which requires the presence of a resonance near their scattering threshold. The universality of S-wave near-threshold resonances then implies that the low-energy scattering properties of a two-body bound state of dark matter particles are completely determined by its binding energy, irrespective of the underlying microphysics. The form factor for elastic scattering of the bound state from a nucleus and the possibility of break up of the bound state produce new signatures in the nuclear recoil energy spectrum. If these features are observed in experiments, it will give a smoking-gun signature for the internal structure of dark matter.

Laha, Ranjan; Braaten, Eric

2014-05-01

297

SPIFI: a direct-detection imaging spectrometer for submillimeter wavelengths.  

PubMed

The South Pole Imaging Fabry-Perot Interferometer (SPIFI) is the first instrument of its kind-a direct-detection imaging spectrometer for astronomy in the submillimeter band. SPIFI's focal plane is a square array of 25 silicon bolometers cooled to 60 mK; the spectrometer consists of two cryogenic scanning Fabry-Perot interferometers in series with a 60-mK bandpass filter. The instrument operates in the short submillimeter windows (350 and 450 microm) available from the ground, with spectral resolving power selectable between 500 and 10,000. At present, SPIFI's sensitivity is within a factor of 1.5-3 of the photon background limit, comparable with the best heterodyne spectrometers. The instrument's large bandwidth and mapping capability provide substantial advantages for specific astrophysical projects, including deep extragalactic observations. We present the motivation for and design of SPIFI and its operational characteristics on the telescope. PMID:12009168

Bradford, C Matt; Stacey, Gordon J; Swain, Mark R; Nikola, Thomas; Bolatto, Alberto D; Jackson, James M; Savage, Maureen L; Davidson, Jacqueline A; Ade, Peter A R

2002-05-01

298

New observables for direct detection of axion dark matter  

NASA Astrophysics Data System (ADS)

We propose new signals for the direct detection of ultralight dark matter such as the axion. Axion or axionlike particle dark matter may be thought of as a background, classical field. We consider couplings for this field which give rise to observable effects including a nuclear electric dipole moment, and axial nucleon and electron moments. These moments oscillate rapidly with frequencies accessible in the laboratory, ˜ kilohertz to gigahertz, given by the dark matter mass. Thus, in contrast to WIMP detection, instead of searching for the hard scattering of a single dark matter particle, we are searching for the coherent effects of the entire classical dark matter field. We calculate current bounds on such time-varying moments and consider a technique utilizing NMR methods to search for the induced spin precession. The parameter space probed by these techniques is well beyond current astrophysical limits and significantly extends laboratory probes. Spin precession is one way to search for these ultralight particles, but there may well be many new types of experiments that can search for dark matter using such time-varying moments.

Graham, Peter W.; Rajendran, Surjeet

2013-08-01

299

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

300

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

301

Detection and enumeration of Vibrio vulnificus by direct colony immunoblot.  

PubMed

A direct colony immunoblot method (DCI) for the enumeration of Vibrio vulnificus was developed. Bacterial colonies were transferred from agar plates to membranes, which were then dried and blocked with bovine serum albumin. Subsequently, the membranes were treated with anti-V. vulnificus H antibodies, washed and incubated with peroxidase-conjugated goat anti-rabbit IgG. After a final wash, the membranes were exposed to a substrate mixture containing H(2)O(2) which resulted in the development of a purple color by V. vulnificus colonies. The DCI detected all clinical and environmental V. vulnificus strains tested and did not cross-react with other Vibrio species including V. cholerae, V. parahaemolyticus, or V. fluvialis. The DCI was then compared to the DNA hybridization procedure (DNAH) using V. vulnificus agar plates inoculated with mixed cultures of V. vulnificus and V. parahaemolyticus and V. vulnificus-seeded oyster homogenates. Both DCI and DNAH detected 1 to 2 log colony forming units (CFU)/mL V. vulnificus mixed with 4 log CFU/mL V. parahaemolyticus. Both methods were comparable and demonstrated no significant statistical differences when enumerating V. vulnificus in mixed cultures or in oyster homogenates seeded with levels of V. vulnificus from 2 to 6 log CFU/mL. The DCI demonstrated clearer color development and was less time consuming than the DNAH. PMID:19200106

Senevirathne, R N; Janes, M E; Simonson, J G

2009-01-01

302

Direct Detections of Young Stars in Nearby Elliptical Galaxies  

NASA Astrophysics Data System (ADS)

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 × 10-5 M ? yr-1. The star formation history was roughly constant from 0.5 to 1.5 Gyr (at (3-5) × 10-4 M ? yr-1), but decreased by a factor of several in the past 0.3 Gyr. Most star clusters have a mass between 102 and 104 M ?. The specific star formation rates of ~10-16 yr-1 (at the present day) or ~10-14 yr-1 (when averaging over the past Gyr) imply that a fraction 10-8 of the stellar mass is younger than 100 Myr and 10-5 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. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program 11583.

Ford, H. Alyson; Bregman, Joel N.

2013-06-01

303

Direct detection of dark matter with liquid argon and neon  

NASA Astrophysics Data System (ADS)

There is a great deal of observational evidence across a wide variety of scales that a large fraction of the universe and most of the matter in the universe is made up of some form of non-baryonic, dark matter. The most prominent candidate for dark matter is the weakly interacting massive particle or WIMP, with a mass between 1 GeV to a few TeV, and there are many current experiments aiming to detect these particles directly. The DEAP/CLEAN program seeks to detect dark matter and pp-solar neutrinos using liquid argon and liquid neon as targets. When ionizing radiation interacts in these liquids, scintillation light is produced. The timing or pulse shape of scintillation provides pulse shape discrimination (PSD) with which to identify the type of recoil that occurred in the liquid. As WIMP-nucleus scattering events would produce nuclear recoils but most of the backgrounds produce electronic recoils, PSD provides background rejection, allowing liquid argon- and neon-based detectors to achieve excellent sensitivity to dark matter. In this work, I describe the evidence for dark matter and review the state of current detection efforts. I then discuss observations of scintillation in liquid argon and liquid neon performed in prototype detectors at Yale and underground at SNOLAB in Ontario, Canada, focusing on measurements of PSD, the nuclear recoil scintillation efficiency and alpha backgrounds in these detectors. I describe the implications of these measurements for both the argon and neon components of the DEAP/CLEAN program, including simulations of a possible 10-tonne liquid neon detector. In the first appendix, I describe efforts at Yale to build a thermal column for the separation of isotopes, with applications to both dark matter and neutrinoless double-beta decay searches. In the second appendix, I describe operation of an evaporator system.

Lippincott, W. Hugh

2010-12-01

304

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

305

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

306

Direct Detection Doppler Lidar for Spaceborne Wind Measurement  

NASA Technical Reports Server (NTRS)

Aerosol and molecular based versions of the double-edge technique can be used for direct detection Doppler lidar spaceborne wind measurement. The edge technique utilizes the edge of a high spectral resolution filter for high accuracy wind measurement using direct detection lidar. The signal is split between an edge filter channel and a broadband energy monitor channel. The energy monitor channel is used for signal normalization. The edge measurement is made as a differential frequency measurement between the outgoing laser signal and the atmospheric backscattered return for each pulse. As a result the measurement is insensitive to laser and edge filter frequency jitter and drift at a level less than a few parts in 10(exp 10). We have developed double edge versions of the edge technique for aerosol and molecular-based lidar measurement of the wind. Aerosol-based wind measurements have been made at Goddard Space Flight Center and molecular-based wind measurements at the University of Geneva. We have demonstrated atmospheric measurements using these techniques for altitudes from 1 to more than 10 km. Measurement accuracies of better than 1.25 m/s have been obtained with integration times from 5 to 30 seconds. The measurements can be scaled to space and agree, within a factor of two, with satellite-based simulations of performance based on Poisson statistics. The theory of the double edge aerosol technique is described by a generalized formulation which substantially extends the capabilities of the edge technique. It uses two edges with opposite slopes located about the laser frequency at approximately the half-width of each edge filter. This doubles the signal change for a given Doppler shift and yields a factor of 1.6 improvement in the measurement accuracy compared to the single edge technique. The use of two high resolution edge filters substantially reduces the effects of Rayleigh scattering on the measurement, as much as order of magnitude, and allows the signal to noise ratio to be substantially improved in areas of low aerosol backscatter. We describe a method that allows the Rayleigh and aerosol components of the signal to be independently determined using the two edge channels and an energy monitor channel. The effects of Rayleigh scattering may then subtracted from the measurement and we show that the correction process does not significantly increase the measurement noise for Rayleigh to aerosol ratios up to 10. We show that for small Doppler shifts a measurement accuracy of 0.4 m/s can be obtained for 5000 detected photon, 1.2 m/s for 1000 detected photons, and 3.7 m/s for 50 detected photons for a Rayleigh to aerosol ratio of 5. Methods for increasing the dynamic range of the aerosol-based system to more than +/- 100 m/s are given.

Korb, C. Laurence; Flesia, Cristina

1999-01-01

307

Direct detection of Helicobacter pylori resistance to macrolides by a polymerase chain reaction/DNA enzyme immunoassay in gastric biopsy specimens  

PubMed Central

BACKGROUND—The increasing use of macrolides especially in the treatment of Helicobacter pylori infection has led to an increase in resistant strains. The resistance of H pylori to macrolides, especially clarithromycin, is one of the major causes of eradication failure. In H pylori, clarithromycin resistance is due to point mutations localised in domain V of 23S rRNA. ?AIM—To develop a molecular technique based on amplification of a relevant fragment of the 23S rRNA and colorimetric hybridisation in liquid phase to detect directly in biopsy specimens the type of mutation associated with resistance of H pylori to clarithromycin. ?METHODS—Gastric biopsy samples from 61 patients were submitted to this test. The results were compared with standard methods (determination of minimal inhibition concentration, polymerase chain reaction/restriction fragment length polymorphism, and/or DNA sequencing) in order to evaluate the test and to define the cut off values, specificity, and sensitivity. ?RESULTS—The 14 biopsy samples in which H pylori was not detected did not give a positive result in any assay, and the 14 samples harbouring strains susceptible to clarithromycin gave a positive result with the wild type probe as expected. The 33 biopsy specimens containing resistant strains always gave a positive signal with one of the probes detecting resistant organisms, but in eight cases they also reacted with the wild type probe, indicating that a mixture of resistant and susceptible organisms was present. ?CONCLUSION—The importance of this new assay is that it allows the detection of multiple genotypes corresponding to either heterogeneous genotypes or mixed infections. Moreover, it allows in a single step not only the detection of H pylori but also the determination of its susceptibility to clarithromycin directly in biopsy specimens without the need for culture. ?? Keywords: Helicobacter pylori; resistance; clarithromycin; macrolide; polymerase chain reaction (PCR); immunoassay

Marais, A; Monteiro, L; Occhialini, A; Pina, M; Lamouliatte, H; Megraud, F

1999-01-01

308

A Novel Colorimetric Immunoassay Utilizing the Peroxidase Mimicking Activity of Magnetic Nanoparticles  

PubMed Central

A simple colorimetric immunoassay system, based on the peroxidase mimicking activity of Fe3O4 magnetic nanoparticles (MNPs), has been developed to detect clinically important antigenic molecules. MNPs with ca. 10 nm in diameter were synthesized and conjugated with specific antibodies against target molecules, such as rotaviruses and breast cancer cells. Conjugation of the MNPs with antibodies (MNP-Abs) enabled specific recognition of the corresponding target antigenic molecules through the generation of color signals arising from the colorimetric reaction between the selected peroxidase substrate, 3,3?,5,5?-tetramethylbenzidine (TMB) and H2O2. Based on the MNP-promoted colorimetric reaction, the target molecules were detected and quantified by measuring absorbance intensities corresponding to the oxidized form of TMB. Owing to the higher stabilities and economic feasibilities of MNPs as compared to horseradish peroxidase (HRP), the new colorimetric system employing MNP-Abs has the potential of serving as a potent immunoassay that should substitute for conventional HRP-based immunoassays. The strategy employed to develop the new methodology has the potential of being extended to the construction of simple diagnostic systems for a variety of biomolecules related to human cancers and infectious diseases, particularly in the realm of point-of-care applications.

Woo, Min-Ah; Kim, Moon Il; Jung, Jae Hwan; Park, Ki Soo; Seo, Tae Seok; Park, Hyun Gyu

2013-01-01

309

Direct detection of renal function markers using microchip CE with pulsed electrochemical detection.  

PubMed

Creatinine, creatine, and uric acid are three important compounds that are measured in a variety of clinical assays, most notably for renal function. Traditional clinical assays for these compounds have focused on the use of enzymes or chemical reactions. Electrophoretic microchips have the potential to integrate separation power of capillary electrophoresis with devices that are small, portable, and have the speed of conventional sensors. The development of a microchip CE system for the direct detection of creatinine, creatine, and uric acid is presented. The device uses pulsed amperometric detection (PAD) to detect the nitrogen-containing compounds as well as the easily oxidizable uric acid. Baseline separation of creatinine, creatine and uric acid was achieved using 30 mM borate buffer (pH = 9.4) in less than 200 s. Linear calibration curves were obtained with limits of detection of 80 microM, 250 microM and 270 microM for creatinine, creatine and uric acid respectively. An optimization of the separation conditions and a comparison of PAD with other amperometric detection modes is also shown. Finally, analysis of a real urine sample is presented with validation of creatinine concentrations using a clinical assay kit based on the Jaffé reaction. PMID:15213822

Garcia, Carlos D; Henry, Charles S

2004-07-01

310

Solvent colorimetric paper-based polydiacetylene sensors from diacetylene lipids.  

PubMed

A well known unique property of polydiacetylenes (PDAs) is the colorimetric response to external stimuli making it one of the most studied conjugated polymers for sensing applications. Here we report the synthesis of a novel series of diacetylene acids from the condensation of pentacosa-10,12-diynylamine (PCDAmine) and dicarboxylic acid or its anhydrides. One of these diacetylene lipids, 4-(pentacosa-10,12-diynylamino)-4-oxobutanoic acid (PCDAS), is used in combination with pentacosa-10,12-diynoic acid (PCDA) for dropcasting on pieces of filter paper which are consequently irradiated by UV light to generate a paper based sensor array for solvent detection and identification. Upon the exposure to various types of organic solvents, the blue colored sensors colorimetrically respond to give different shades of colors between blue to red. The color patterns of the sensor array are recorded as RedGreenBlue (RGB) values and statistically analyzed by principal component analysis (PCA). The PCA score plot reveals that the array is capable of identifying eleven common organic solvents. PMID:21943512

Pumtang, Suricha; Siripornnoppakhun, Warathip; Sukwattanasinitt, Mongkol; Ajavakom, Anawat

2011-12-15

311

Detection and performance analysis for a moving point source in speckle noise, application to exoplanet detection by direct imaging  

Microsoft Academic Search

With the current development of astronomical instruments able to detect the direct light of exoplanets, such as the very large telescope instrument SPHERE, statistical tools need to be developed in order to make precise detection and estimation assessments. We propose a detection algorithm that delivers an estimation of the position and the intensity of the potentially detected exoplanet. Because of

Isabelle Smith; André Ferrari; Marcel Carbillet

2008-01-01

312

Galactic substructure and direct detection of dark matter  

SciTech Connect

We study the effects of substructure in the Galactic halo on direct detection of dark matter, on searches for energetic neutrinos from weakly interacting massive particles (WIMP) annihilation in the Sun and Earth, and on the enhancement in the WIMP annihilation rate in the halo. Our central result is a probability distribution function (PDF) P({rho}) for the local dark-matter density. This distribution must be taken into account when using null dark-matter searches to constrain the properties of dark-matter candidates. We take two approaches to calculating the PDF. The first is an analytic model that capitalizes on the scale-invariant nature of the structure-formation hierarchy in order to address early stages in the hierarchy (very small scales; high densities). Our second approach uses simulation-inspired results to describe the PDF that arises from lower-density larger-scale substructures which formed in more recent stages in the merger hierarchy. The distributions are skew positive, and they peak at densities lower than the mean density. The local dark-matter density may be as small as 1/10th the canonical value of {approx_equal}0.4 GeV cm{sup -3}, but it is probably no less than 0.2 GeV cm{sup -3}.

Kamionkowski, Marc; Koushiappas, Savvas M. [California Institute of Technology, Mail Code 130-33, Pasadena, CA 91125 (United States); Los Alamos National Laboratory, Mail Stop B227, Los Alamos, NM 87545 (United States)

2008-05-15

313

Mirror dark matter: Cosmology, galaxy structure and direct detection  

NASA Astrophysics Data System (ADS)

A simple way to accommodate dark matter is to postulate the existence of a hidden sector. That is, a set of new particles and forces interacting with the known particles predominantly via gravity. In general, this leads to a large set of unknown parameters, however, if the hidden sector is an exact copy of the standard model sector, then, an enhanced symmetry arises. This symmetry, which can be interpreted as space-time parity, connects each ordinary particle (e, ?, p, n, ?, …) with a mirror partner (e?, ??, p?, n?, ??, …). If this symmetry is completely unbroken, then the mirror particles are degenerate with their ordinary particle counterparts, and would interact amongst themselves with exactly the same dynamics that govern ordinary particle interactions. The only new interaction postulated is photon-mirror photon kinetic mixing, whose strength ?, is the sole new fundamental (Lagrangian) parameter relevant for astrophysics and cosmology. It turns out that such a theory, with suitably chosen initial conditions effective in the very early universe, can provide an adequate description of dark matter phenomena provided that ? 10-9. This review focusses on three main developments of this mirror dark matter theory during the last decade: early universe cosmology, galaxy structure and the application to direct detection experiments.

Foot, R.

2014-04-01

314

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

315

Effects of Mn 2+ on oligonucleotide-gold nanoparticle hybrids for colorimetric sensing of Hg 2+: Improving colorimetric sensitivity and accelerating color change  

Microsoft Academic Search

In this paper, we present a simple and rapid colorimetric assay – using the polythymine oligonucleotide T33, citrate-capped gold nanoparticles (AuNPs), and phosphate-buffer saline (PBS) in the presence of Mn2+ – for the highly selective and sensitive detection of Hg2+ in an aqueous solution. Citrate-capped AuNPs adsorbed on randomly coiled T33 were dispersed well in PBS because of strong electrostatic

Cheng-Ju Yu; Tian-Lu Cheng; Wei-Lung Tseng

2009-01-01

316

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

317

A water-soluble near-infrared probe for colorimetric and ratiometric sensing of SO2 derivatives in living cells.  

PubMed

A coumarin TCF-based water-soluble near-infrared fluorescent probe was presented, which could be used for the rapid, colorimetric and ratiometric detection of SO2 derivatives with a detection limit of 0.27 nM. Moreover, this probe could successfully image the analyte in living cells. PMID:24217742

Wu, Ming-Yu; Li, Kun; Li, Chun-Yan; Hou, Ji-Ting; Yu, Xiao-Qi

2014-01-01

318

Colorimetric characterization models based on colorimetric characteristics evaluation for active matrix organic light emitting diode panels.  

PubMed

The colorimetric characterization of active matrix organic light emitting diode (AMOLED) panels suffers from their poor channel independence. Based on the colorimetric characteristics evaluation of channel independence and chromaticity constancy, an accurate colorimetric characterization method, namely, the polynomial compensation model (PC model) considering channel interactions was proposed for AMOLED panels. In this model, polynomial expressions are employed to calculate the relationship between the prediction errors of XYZ tristimulus values and the digital inputs to compensate the XYZ prediction errors of the conventional piecewise linear interpolation assuming the variable chromaticity coordinates (PLVC) model. The experimental results indicated that the proposed PC model outperformed other typical characterization models for the two tested AMOLED smart-phone displays and for the professional liquid crystal display monitor as well. PMID:23089779

Gong, Rui; Xu, Haisong; Tong, Qingfen

2012-10-20

319

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

320

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

321

Development of colorimetric solid phase extraction (C-SPE) for in-flight monitoring of spacecraft water supplies  

NASA Astrophysics Data System (ADS)

Colorimetric solid phase extraction (C-SPE) is a sorption-spectrophotometric technique that combines colorimetric reagents, solid phase extraction, and diffuse reflectance spectroscopy to quantify trace analytes in water samples. In C-SPE, a syringe is used to meter a known volume of sample through a membrane impregnated with a selective colorimetric reagent along with any additives required to optimize the complexation of the reagent and analyte. As the sample is passed through the membrane, analytes are extracted and complexed, leading to a detectable change in the optical characteristics of the membrane. The analyte-reagent complex is then quantified directly on the membrane, using a hand-held diffuse reflectance spectrophotometer. This dissertation focuses on the development, ground testing, and microgravity flight demonstration of C-SPE methods to meet the near- and long-term water quality monitoring needs of NASA. To this end, the ability of C-SPE to function in a microgravity environment was tested through performance evaluations of methods for the determination of the biocidal agents silver(I) and iodine on the KC-135 microgravity simulator. The biocidal iodine platform was investigated further to determine which iodine species is responsible for the C-SPE signal. Through systematic comparisons of C-SPE results and UV-Visible absorbance studies it was determined that biocidally active I2 is the iodine species complexed by poly(vinylpyrrolidone). The application of C-SPE to additional target water quality parameters is demonstrated through the determination of nickel(II), a metal leachate found in archived water samples from the International Space Station, using dimethylglyoxime. This method introduced a new variation of C-SPE, the quantification of trace analytes based on the collection of an insoluble, colored precipitate. The nickel(II) method was then combined with the method for biocidal silver(I) and a new method to measure sample pH to create a multiplexed C-SPE platform. This invention is presented as an approach to increase the collection of on-orbit water quality data collected without requiring additional crew time. The dissertation is concluded with a summation of the current work and a look at future directions.

Gazda, Daniel Bryan

322

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

323

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.

Anderson, Erik P.; Daniels, Jonathan S.; Yu, Heng; Karhanek, Miloslav; Lee, Thomas H.; Davis, Ronald W.; Pourmand, Nader

2008-01-01

324

Colorimetric sensor array for determination and identification of toxic industrial chemicals.  

PubMed

A low-cost yet highly sensitive colorimetric sensor array for the detection and identification of toxic industrial chemicals (TICs) has been developed. The sensor consists of a disposable array of cross-responsive nanoporous pigments whose colors are changed by diverse chemical interactions with analytes. Clear differentiation among 20 different TICs has been easily achieved at both their IDLH (immediately dangerous to life or health) concentration within 2 min of exposure and PEL (permissible exposure limit) concentration within 5 min of exposure with no errors or misclassifications. Detection limits are generally well below the PEL (in most cases below 5% of PEL) and are typically in the low ppb range. The colorimetric sensor array is not responsive to changes in humidity or temperature over a substantial range. The printed arrays show excellent batch to batch reproducibility and long shelf life (greater than 3 months). PMID:20954720

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

2010-11-15

325

A Colorimetric Estimation of Polyethyleneglycol-Conjugated Phospholipid in Stealth Liposomes  

Microsoft Academic Search

The paper describes a colorimetric method for estimation of polyethyleneglycol (PEG)-conjugated phospholipid in either form, free or bound to liposomes. It provides a rapid, highly reproducible, and sensitive tool to detect PEG-coupled phospholipid in amounts as low as 1 ?g giving a linear response over a range of 1–100 ?g. The method makes use of the biphasic system comprising aqueous

Alo Nag; Gargi Mitra; Prahlad C. Ghosh

1997-01-01

326

A simple colorimetric FIA method for the determination of pyrite oxidation rates  

Microsoft Academic Search

A method for the rapid determination of the oxidation rate of naturally occurring pyrite (FeS2) samples is presented. The progress of the oxidation reaction was followed by measurement of the concentration of total dissolved iron using flow injection analysis. Iron was determined using UV–vis detection after reaction with the colorimetric reagent 5-sulfosalicylic acid in the presence of ammonia. The calibration

Owen D. Osborne; Allan Pring; Claire E. Lenehan

2010-01-01

327

Mesoporous silica-coated gold nanorods: towards sensitive colorimetric sensing of ascorbic acid via target-induced silver overcoating.  

PubMed

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. PMID:21331422

Wang, Guoqing; Chen, Zhaopeng; Chen, Lingxin

2011-04-01

328

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

329

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

330

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

331

Masking Model for Accurate Colorimetric Characterization of LCD  

Microsoft Academic Search

A color management system (CMS) such as ICC profile or sRGB space have been proposed for color transformation and reproduction of cross media. In such a CMS, accurate colorimetric char- acterization of a display device plays a critical role in achieving device-independent color reproduc- tion. In the case of a CRT, colorimetric characterization based on a GOG model is accurate

Nobuhiko Tamura; Norimichi Tsumura; Yoichi Miyake

2002-01-01

332

Exotic PeV particle detection using Direct Cerenkov Light  

NASA Astrophysics Data System (ADS)

We describe the potential use of the Direct ?Cerenkov light (D ?C) observation technique for observing new cosmic ray and astrophysical phenomena. This technique may allow for high resolution charge measurements of cosmic ray nuclei in the PeV energy region as well as searches for exotic particle states. The same instrument might be used for an allsky survey for TeV ?-ray sources. We detail the conceptual design of a wide field-of-view "Direct ?Cerenkov Observatory" for exploiting this technique, and describe several new science goals that can be addressed by this instrument.

Kieda, D. B.; Swordy, S. P.; Wakely, S. P.

2001-08-01

333

Tomographic motion detection and correction directly in sinogram space  

Microsoft Academic Search

Patient motion, especially respiratory motion, results in various artefacts such as blurring and streaks in tomographic images. The interplay of the movement of the beam aperture and variations of organ anatomy during delivery can create 'hot' and 'cold' spots throughout the field in intensity-modulated radiation therapy (IMRT). Detection and correction of patient motion is extremely important in tomographic imaging and

Weiguo Lu; Thomas R. Mackie

2002-01-01

334

Aptamer Beacons for the Direct Detection of Proteins  

Microsoft Academic Search

We have designed a new class of molecules, which we term aptamer beacons, for detecting a wide range of ligands. Similar to molecular beacons, aptamer beacons can adopt two or more conformations, one of which allows ligand binding. A fluorescence-quenching pair is used to report changes in conformation induced by ligand binding. An anti-thrombin aptamer was engineered into an aptamer

Nobuko Hamaguchi; Andrew Ellington; Martin Stanton

2001-01-01

335

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

336

Direct detection of variable tropospheric clouds near Titan's south pole  

Microsoft Academic Search

Atmospheric conditions on Saturn's largest satellite, Titan, allow the possibility that it could possess a methane condensation and precipitation cycle with many similarities to Earth's hydrological cycle. Detailed imaging studies, of Titan have hitherto shown no direct evidence for tropospheric condensation clouds, although there has been indirect spectroscopic evidence for transient clouds,. Here we report images and spectra of Titan

Antonin H. Bouchez; Caitlin A. Griffith; Michael E. Brown

2003-01-01

337

A New Colorimetric Assay of Tabletop Sweeteners Using a Modified Biuret Reagent: An Analytical Chemistry Experiment for the Undergraduate Curriculum  

ERIC Educational Resources Information Center

A new, fast and effective colorimetric analysis of the artificial sweetener aspartame is presented for application in undergraduate laboratory courses. This new method incorporates the use of a modified biuret reagent for selective detection and analysis of aspartame in aqueous solutions. The modified reagent is less caustic than the traditional…

Fenk, Christopher J.; Kaufman, Nathan; Gerbig, Donald G., Jr.

2007-01-01

338

Direct detection of DNA with an integrated detector on a microfluidic chip  

Microsoft Academic Search

Summary form only given. A microfluidic chip has been developed which allows for the direct detection of several distinct DNA targets present in a sample. The direct detection of underivatized DNA is advantageous for the analysis of very small amounts of sample, where contamination is a major concern. DNA probes can be attached in microchannels present on the chip via

W. G. Kuhr; C. B. Davis; S. Brazill

1999-01-01

339

Determination of MICs forMycobacterium avium-M. intracellulare Complex in Liquid Medium by a Colorimetric Method  

Microsoft Academic Search

We investigated the potential of a rapid colorimetric microassay based on the reduction of dimethylthiazol- diphenyltetrazolium bromide (MTT) for determining the growth of Mycobacterium avium-M. intracellulare complex (MAC) and MICs of clofazimine, resorcinomycin A, and the quinolone PD 127391 against MAC. The reduction of MTT was directly proportional to the number of viable bacteria. A comparison of the MTT reductiontestwiththe(

R. GOMEZ-FLORES; S. GUPTA; R. TAMEZ-GUERRA; T. MEHTA

1995-01-01

340

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.

Green, Katherine S.; Szebenyi, Doletha M. E.; Boggs, Kasey; Bredthauer, Richard; Tate, Mark W.; Gruner, Sol M.

2013-01-01

341

Gene doping detection: evaluation of approach for direct detection of gene transfer using erythropoietin as a model system  

Microsoft Academic Search

As clinical gene therapy has progressed toward realizing its potential, concern over misuse of the technology to enhance performance in athletes is growing. Although ‘gene doping’ is banned by the World Anti-Doping Agency, its detection remains a major challenge. In this study, we developed a methodology for direct detection of the transferred genetic material and evaluated its feasibility for gene

A Baoutina; T Coldham; G S Bains; K R Emslie

2010-01-01

342

Early detection of Pseudomonas aeruginosa – comparison of conventional versus molecular (PCR) detection directly from adult patients with cystic fibrosis (CF)  

Microsoft Academic Search

BACKGROUND: Pseudomonas aeruginosa (PA) is the most important bacterial pathogen in patients with cystic fibrosis (CF) patients. Currently, routine bacteriological culture on selective\\/non- selective culture media is the cornerstone of microbiological detection. The aim of this study was to compare isolation rates of PA by conventional culture and molecular (PCR) detection directly from sputum. METHODS: Adult patients (n = 57)

Jiru Xu; John E Moore; Philip G Murphy; B Cherie Millar; J Stuart Elborn

2004-01-01

343

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

344

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.

Redmile-Gordon, M.A.; Armenise, E.; White, R.P.; Hirsch, P.R.; Goulding, K.W.T.

2013-01-01

345

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

346

Direct detection of DNA conformation in hybridization processes.  

PubMed

DNA hybridization studies at surfaces normally rely on the detection of mass changes as a result of the addition of the complementary strand. In this work we propose a mass-independent sensing principle based on the quantitative monitoring of the conformation of the immobilized single-strand probe and of the final hybridized product. This is demonstrated by using a label-free acoustic technique, the quartz crystal microbalance (QCM-D), and oligonucleotides of specific sequences which, upon hybridization, result in DNAs of various shapes and sizes. Measurements of the acoustic ratio ?D/?F in combination with a "discrete molecule binding" approach are used to confirm the formation of straight hybridized DNA molecules of specific lengths (21, 75, and 110 base pairs); acoustic results are also used to distinguish between single- and double-stranded molecules as well as between same-mass hybridized products with different shapes, i.e., straight or "Y-shaped". Issues such as the effect of mono- and divalent cations to hybridization and the mechanism of the process (nucleation, kinetics) when it happens on a surface are carefully considered. Finally, this new sensing principle is applied to single-nucleotide polymorphism detection: a DNA hairpin probe hybridized to the p53 target gene gave products of distinct geometrical features depending on the presence or absence of the SNP, both readily distinguishable. Our results suggest that DNA conformation probing with acoustic wave sensors is a much more improved detection method over the popular mass-related, on/off techniques offering higher flexibility in the design of solid-phase hybridization assays. PMID:22248021

Papadakis, George; Tsortos, Achilleas; Bender, Florian; Ferapontova, Elena E; Gizeli, Electra

2012-02-21

347

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

348

Unamplified direct detection sensor for passive millimeter wave imaging  

NASA Astrophysics Data System (ADS)

We have demonstrated a high efficiency package for zero bias Sb-based backward tunnel diodes developed for passive millimeter wave imaging. Flip-chip mounting of detector MMICs onto quartz substrates permit placement of the detector directly within the WR-10 waveguide feeds for diagonal horn antennas. This arrangement minimizes the losses between the detectors and antennas while providing an impedance match over a majority of W band. A 2x2 array of radiometers was fabricated, assembled, and measured using coherent measurement techniques. The resulting noise equivalent temperature difference, calculated assuming a 30 Hz frame rate is 10 degrees K.

Lynch, Jonathan; Moyer, Harris; Schulman, Joel; Lawyer, Phillip; Bowen, Ross; Schaffner, James; Choudhury, Debabani; Foschaar, Jim; Chow, David

2006-06-01

349

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.

Walker, Avery S.; Johnson, Eric K.; Maykel, Justin A.; Stojadinovic, Alex; Nissan, Aviram; Brucher, Bjorn; Champagne, Bradley J.; Steele, Scott R.

2014-01-01

350

Chemically responsive nanoporous pigments: colorimetric sensor arrays and the identification of aliphatic amines.  

PubMed

A general method has been developed for the preparation of microspheres of nanoporous pigments, their formulation into chemically responsive pigment inks, and the printing of these inks as colorimetric sensor arrays. Using an ultrasonic-spray aerosol-gel synthesis from chemically responsive dyes and common silica precursors, 16 different nanoporous pigment microspheres have been prepared and characterized. New colorimetric sensor arrays have been created by printing inks of these chemically responsive pigments as primary sensor elements; these arrays have been successfully tested for the detection, identification, and quantitation of toxic aliphatic amines. Among 11 structurally similar amines, complete identification of each analyte without confusion was achieved using hierarchical cluster analysis (HCA). Furthermore, visual identification of ammonia gas was easily made at the IDLH (immediately dangerous to life or health), PEL (permissible exposure limits), and 0.1 PEL concentrations with high reproducibility. PMID:18950204

Bang, Jin Ho; Lim, Sung H; Park, Erwin; Suslick, Kenneth S

2008-11-18

351

Copolythiophene-derived colorimetric and fluorometric sensor for lysophosphatidic acid based on multipoint interactions.  

PubMed

3-Phenylthiophene-based water-soluble copolythiophenes (CPT9) were designed for colorimetric and fluorometric detection of lysophosphatidic acid (LPA) based on electrostatic interaction, hydrophobic interaction, and hydrogen bonding. Other negatively charged species gave nearly no interference, and the detection limit reached to 0.6 ?M, which is below the requisite detection limits for LPA in human plasma samples. The appealing performance of CPT9 was demonstrated to originate from the multipoint interaction-induced conformational change of conjugated backbone and weakened electron transfer effect. To our best knowledge, this is the first polythiophene based optical sensor which displays emission peak red-shift followed with fluorescence enhancement. PMID:23459452

Lan, Minhuan; Liu, Weimin; Wang, Ying; Ge, Jiechao; Wu, Jiasheng; Zhang, Hongyan; Chen, Jianhong; Zhang, Wenjun; Wang, Pengfei

2013-03-01

352

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

353

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

354

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

355

Direct detection of variable tropospheric clouds near Titan's south pole.  

PubMed

Atmospheric conditions on Saturn's largest satellite, Titan, allow the possibility that it could possess a methane condensation and precipitation cycle with many similarities to Earth's hydrological cycle. Detailed imaging studies of Titan have hitherto shown no direct evidence for tropospheric condensation clouds, although there has been indirect spectroscopic evidence for transient clouds. Here we report images and spectra of Titan that show clearly transient clouds, concentrated near the south pole, which is currently near the point of maximum solar heating. The discovery of these clouds demonstrates the existence of condensation and localized moist convection in Titan's atmosphere. Their location suggests that methane cloud formation is controlled seasonally by small variations in surface temperature, and that the clouds will move from the south to the north pole on a 15-year timescale. PMID:12490943

Brown, Michael E; Bouchez, Antonin H; Griffith, Caitlin A

356

Direct Detection of Legionella Species from Bronchoalveolar Lavage and Open Lung Biopsy Specimens: Comparison of LightCycler PCR, In Situ Hybridization, Direct Fluorescence Antigen Detection, and Culture  

PubMed Central

We developed a rapid thermocycling, real-time detection (also known as real-time PCR) method for the detection of Legionella species directly from clinical specimens. This method uses the LightCycler (Roche Molecular Biochemicals, Indianapolis, Ind.) and requires approximately 1 to 2 h to perform. Both a Legionella genus PCR assay and Legionella pneumophila species-specific PCR assay were designed. A total of 43 archived specimens from 35 patients were evaluated, including 19 bronchoalveolar lavage (BAL) specimens and 24 formalin-fixed, paraffin-embedded open lung biopsy specimens. Twenty-five of the specimens were culture-positive for Legionella (9 BAL specimens and 16 tissue specimens). BAL specimens were tested by LightCycler PCR (LC-PCR) methods and by a direct fluorescent antibody (DFA) assay, which detects L. pneumophila serogroups 1 to 6 and several other Legionella species. Tissue sections were tested by the two LC-PCR methods, by DFA, by an in situ hybridization (ISH) assay, specifically designed to detect L. pneumophila, and by Warthin-Starry (WS) staining. The results were compared to the “gold standard” method of bacterial culture. With BAL specimens the following assays yielded the indicated sensitivities and specificities, respectively: Legionella genus detection by Legionella genus LC-PCR, 100 and 100%; Legionella genus detection by DFA assay, 33 and 100%; and L. pneumophila detection by L. pneumophila species-specific LC-PCR, 100 and 100%. With open lung biopsy specimens the following assays yielded the indicated sensitivities and specificities, respectively: Legionella genus detection by LC-PCR 68.8 and 100%; Legionella genus detection by DFA assay, 44 and 100%; Legionella genus detection by WS staining, 63 and 100%; L. pneumophila species-specific detection by LC-PCR, 17 and 100%; and L. pneumophila species-specific detection by ISH, 100 and 100%. The analytical sensitivity of both LC-PCR assays was <10 CFU/reaction. LC-PCR is a reliable method for the direct detection of Legionella species from BAL specimens. The Legionella genus LC-PCR assay could be performed initially; if positive, L. pneumophila species-specific LC-PCR could then be performed (if species differentiation is desired). The speed with which the LC-PCR procedure can be performed offers significant advantages over both culture-based methods and conventional PCR techniques. In contrast, for the methods evaluated, culture was the best for detecting multiple Legionella species in lung tissue. WS staining, Legionella genus LC-PCR, and L. pneumophila species-specific ISH were useful as rapid tests with lung tissue.

Hayden, R. T.; Uhl, J. R.; Qian, X.; Hopkins, M. K.; Aubry, M. C.; Limper, A. H.; Lloyd, R. V.; Cockerill, F. R.

2001-01-01

357

First direct detection of clay minerals on Mars  

NASA Technical Reports Server (NTRS)

Magnesian clays or clay-type minerals were conclusively detected in the martian regolith. Near-IR spectral observations of Mars using the Mauna Kea 2.2-m telescope show weak but definite absorption bands near microns. The absorption band positions and widths match those produced by combined OH stretch and Mg-OH lattice modes and are diagnostic of minerals with structural OH such as clays and amphiboles. Likely candidate minerals include serpentine, talc, hectorite, and sponite. There is no spectral evidence for aluminous hydroxylated minerals. No distinct band occurs at 2.55 microns, as would be expected if carbonates were responsible for the 2.35 micron absorption. High-albedo regions such as Elysium and Utopia have the strongest bands near 2.35 microns, as would be expected for heavily weathered soils. Low-albedo regions such as Iapygia show weaker but distinct bands, consistent with moderate coatings, streaks, and splotches of bright weathered material. In all areas observed, the 2.35-micron absorption is at least three times weaker than would be expected if well-crystallized clay minerals made up the bulk of bright soils on Mars.

Singer, R. B.; Owensby, P. D.; Clark, R. N.

1985-01-01

358

Detecting biological responses to flow management: Missed opportunities; future directions  

USGS Publications Warehouse

The conclusions of numerous stream restoration assessments all around the world are extremely clear and convergent: there has been insufficient appropriate monitoring to improve general knowledge and expertise. In the specialized field of instream flow alterations, we consider that there are several opportunities comparable to full-size experiments. Hundreds of water management decisions related to instream flow releases have been made by government agencies, native peoples, and non-governmental organizations around the world. These decisions are based on different methods and assumptions and many flow regimes have been adopted by formal or informal rules and regulations. Although, there have been significant advances in analytical capabilities, there has been very little validation monitoring of actual outcomes or research related to the response of aquatic dependent species to new flow regimes. In order to be able to detect these kinds of responses and to better guide decision, a general design template is proposed. The main steps of this template are described and discussed, in terms of objectives, hypotheses, variables, time scale, data management, and information, in the spirit of adaptive management. The adoption of such a framework is not always easy, due to differing interests of actors for the results, regarding the duration of monitoring, nature of funding and differential timetables between facilities managers and technicians. Nevertheless, implementation of such a framework could help researchers and practitioners to coordinate and federate their efforts to improve the general knowledge of the links between the habitat dynamics and biological aquatic responses. Copyright ?? 2008 John Wiley & Sons, Ltd.

Souchon, Y.; Sabaton, C.; Deibel, R.; Reiser, D.; Kershner, J.; Gard, M.; Katopodis, C.; Leonard, P.; Poff, N. L.; Miller, W. J.; Lamb, B. L.

2008-01-01

359

Fast and accurate circle detection using gradient-direction-based segmentation.  

PubMed

We present what is to our knowledge the first-ever fitting-based circle detection algorithm, namely, the fast and accurate circle (FACILE) detection algorithm, based on gradient-direction-based edge clustering and direct least square fitting. Edges are segmented into sections based on gradient directions, and each section is validated separately; valid arcs are then fitted and further merged to extract more accurate circle information. We implemented the algorithm with the C++ language and compared it with four other algorithms. Testing on simulated data showed FACILE was far superior to the randomized Hough transform, standard Hough transform, and fast circle detection using gradient pair vectors with regard to processing speed and detection reliability. Testing on publicly available standard datasets showed FACILE outperformed robust and precise circular detection, a state-of-art arc detection method, by 35% with regard to recognition rate and is also a significant improvement over the latter in processing speed. PMID:24323106

Wu, Jianping; Chen, Ke; Gao, Xiaohui

2013-06-01

360

Direct detection and solar capture of spin-dependent dark matter  

NASA Astrophysics Data System (ADS)

We investigate the implication of different elastic spin-dependent (SD) operators on both the direct and indirect detections of the weakly interacting massive particle (WIMP). Six representative building blocks of SD operators, together with their counterparts with a massless mediator, are considered to interpret the direct detection experiments (Xenon100, SIMPLE, and COUPP) in a comprehensive way. We also study the solar capture and annihilation of WIMPs with these effective SD operators and place the constraints on the relevant annihilation rate from neutrino detection experiments Super-Kamionkande and IceCube. Upper limits on the WIMP-nucleon couplings drawn from direct detections are also projected to the annihilation rate for contrast and complementarity. We find that the efficiency of these mentioned detection strategies depends specifically on the six SD operators, while the neutrino-based detections are more effective in exploring the parameter space for the massless mediator scenario.

Liang, Zheng-Liang; Wu, Yue-Liang

2014-01-01

361

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 algorithms; (3) qualitative results from a colorimetric analysis of a typical LACIE scene; and (4) image-to-image color stability.

Juday, R. D. (principal investigator)

1979-01-01

362

Constraining the initial entropy of directly detected exoplanets  

NASA Astrophysics Data System (ADS)

The post-formation, initial entropy Si of a gas giant planet is a key witness to its mass-assembly history and a crucial quantity for its early evolution. However, formation models are not yet able to predict reliably Si, making unjustified the use solely of traditional, `hot-start' cooling tracks to interpret direct-imaging results and calling for an observational determination of initial entropies to guide formation scenarios. Using a grid of models in mass and entropy, we show how to place joint constraints on the mass and initial entropy of an object from its observed luminosity and age. This generalizes the usual estimate of only a lower bound on the real mass, through hot-start tracks. Moreover, we demonstrate that with mass information, e.g. from dynamical-stability analyses or radial velocity, tighter bounds can be set on the initial entropy. We apply this procedure to 2M1207 b and find that its initial entropy is at least 9.2 kB/baryon, assuming that it does not burn deuterium. For the planets of the HR 8799 system, we infer that they must have formed with Si > 9.2 kB/baryon, independent of uncertainties about the age of the star. Finally, a similar analysis for ? Pic b reveals that it must have formed with Si > 10.5 kB/baryon, using the radial-velocity mass upper limit. These initial entropy values are, respectively, ca. 0.7, 0.5 and 1.5 kB/baryon higher than the ones obtained from core-accretion models by Marley et al., thereby quantitatively ruling out the coldest starts for these objects and constraining warm starts, especially for ? Pic b.

Marleau, G.-D.; Cumming, A.

2014-01-01

363

Direct alkalinity detection with ion-selective chronopotentiometry.  

PubMed

We explore the possibility to directly measure pH and alkalinity in the sample with the same sensor by imposing an outward flux of hydrogen ions from an ion-selective membrane to the sample solution by an applied current. The membrane consists of a polypropylene-supported liquid membrane doped with a hydrogen ionophore (chromoionophore I), ion exchanger (KTFBP), and lipophilic electrolyte (ETH 500). While the sample pH is measured at zero current, alkalinity is assessed by chronopotentiometry at anodic current. Hydrogen ions expelled from the membrane undergo acid-base solution chemistry and protonate available base in the diffusion layer. With time, base species start to be depleted owing to the constant imposed hydrogen ion flux from the membrane, and a local pH change occurs at a transition time. This pH change (potential readout) is correlated to the concentration of the base in solution. As in traditional chronopotentiometry, the observed square root of transition time (?) was found to be linear in the concentration range of 0.1 mM to 1 mM, using the bases tris(hydroxymethyl)aminomethane, ammonia, carbonate, hydroxide, hydrogen phosphate, and borate. Numerical simulations were used to predict the concentration profiles and the chronopotentiograms, allowing the discussion of possible limitations of the proposed method and its comparison with volumetric titrations of alkalinity. Finally, the P-alkalinity level is measured in a river sample to demonstrate the analytical usefulness of the proposed method. As a result of these preliminary results, we believe that this approach may become useful for the in situ determination of P-alkalinity in a range of matrixes. PMID:24866096

Afshar, Majid Ghahraman; Crespo, Gastón A; Xie, Xiaojiang; Bakker, Eric

2014-07-01

364

Positive cloud-to-ground lightning detection by a direction-finder network  

NASA Technical Reports Server (NTRS)

Consideration is given to the ability of an automatic direction-finder network to identify cloud-to-ground flashes that effectively lower positive charge to the ground (+CG flashes). Records from an extremely low frequency system are examined to determine whether or not 340 +CG flashes detected by the network have coincident waveforms characteristic of +CG flashes. It is found that false detection in the system is negligible for +CG flashes with range-normalized amplitudes of at least 50 direction-finder units. Also, it is shown that no more than about 15 percent of the +CG flashes detected by the system at smaller amplitudes are false detections.

Macgorman, Donald R.; Taylor, William L.

1989-01-01

365

A rapid, multiwell colorimetric assay for chemotaxis.  

PubMed

This paper describes a colorimetric assay for the rapid quantification of chemotaxis in multiple samples. In this assay, cells that have migrated through polycarbonate membrane filters are collected onto the bottom wells of a chemotaxis chamber after centrifugation then the number of viable cells collected in the bottom well is quantified by measurement of the reduction of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenol tetrazolium bromide (MTT). The degree of MTT reduction, which corresponds to the relative cell number, is measured automatically with an ELISA reader. The MTT method of quantitation is as sensitive as the standard manual method, is especially useful for large numbers of samples and requires no specialized laboratory equipment. PMID:8370922

Shi, Y; Kornovski, B S; Savani, R; Turley, E A

1993-09-15

366

Signal to Noise Ratios of Pulsed and Sinewave Modulated Direct Detection Lidar for IPDA Measurements  

NASA Technical Reports Server (NTRS)

The signal-to-noise ratios have been derived for IPDA lidar using a direct detection receiver for both pulsed and sinewave laser modulation techniques, and the results and laboratory measurements are presented

Sun, Xiaoli; Abshire, James B.

2011-01-01

367

Direct (13)C NMR detection in HPLC hyphenation mode: analysis of Ganoderma lucidum terpenoids.  

PubMed

Solid phase extraction (SPE) was introduced as a crucial step in the HPLC-SPE-NMR technique to enable online analyte enrichment from which proton-detected NMR experiments on submicrogram amounts from complex mixtures were possible. However, the significance of direct-detected (13)C NMR experiments is indubitable in simplifying structural elucidations. In the current study, we demonstrated direct (13)C NMR detection of triterpenoids from a Ganoderma lucidum extract in hyphenation mode. The combined advantage of a cryogenically cooled probe, miniaturization, and multiple trapping enabled the first reported application of HPLC-SPE-NMR analysis using direct-detected (13)C NMR spectra. HPLC column loading, accumulative SPE trappings, and the effect of different elution solvents were evaluated and optimized. A column loading of approximately 600 ?g of a prefractionated triterpenoid mixture, six trappings, and an acquisition time of 13 h resulted in spectra with adequate signal-to-noise ratios to detect all C-13 signals. PMID:22515483

Wubshet, Sileshi G; Johansen, Kenneth T; Nyberg, Nils T; Jaroszewski, Jerzy W

2012-05-25

368

A resorufin-based colorimetric and fluorescent probe for live-cell monitoring of hydrazine.  

PubMed

We report a novel colorimetric and red-emitting fluorescent probe for hydrazine detection based on resorufin platform. This OFF-ON fluorescent probe shows a large (117nm) red-shifted absorption spectrum and the color changes from colorless to red upon addition of hydrazine in the aqueous solution, which can serve as a "naked-eye" probe for hydrazine. Moreover, this probe also shows a significant fluorescence increase (~16 folds) and excellent linear relationship at physiological pH. Utilizing this sensitive and selective probe, we have successfully detected hydrazine in living cells. PMID:24662059

Qian, Yong; Lin, Jie; Han, Lujing; Lin, Lin; Zhu, Hailiang

2014-08-15

369

A concise colorimetric and fluorimetric probe for sarin related threats designed via the "covalent-assembly" approach.  

PubMed

A turn-on signal from zero background allows sensitive detection of a weak signal and is highly desired. The "covalent-assembly" probe design principle is powerful in this regard. Herein, we report an embodiment of this principle (NA570) for detection of Sarin related threats, based on a phenylogous Vilsmeier-Haack reaction. NA570 bears a concise molecular construct, exhibits a colorimetric and a fluorimetric signal, and has potential for real applications. PMID:24766398

Lei, Zuhai; Yang, Youjun

2014-05-01

370

Detection of noroviruses in fecal specimens by direct RT-PCR without RNA purification.  

PubMed

Noroviruses are important human pathogens which cause epidemic acute viral gastroenteritis. Current techniques used for detection of noroviruses in fecal specimens involve multi-step viral RNA extraction and purification followed by reverse transcriptase-polymerase chain reaction (RT-PCR). This study demonstrates a method for easy detection of norovirus in fecal specimens, involving one-step RNA release and direct use of the released RNA for RT-PCR (direct RT-PCR). For one-step RNA release, a simple method was adopted based on addition of the sample treatment reagent from a commercialized Norovirus GI and GII RNA Detection Kit to suspended fecal specimens, followed by a brief heat treatment. The released RNA was then added directly to the RT mixture from the same kit. After reverse transcription and PCR, the product was detected by agarose gel electrophoresis. Direct RT-PCR was evaluated with 275 fecal specimens comprising 230 norovirus-positive and 45 norovirus-negative samples as assessed by real-time RT-PCR, considered to be the "gold standard" for norovirus detection. Direct RT-PCR was sufficiently specific and sensitive for norovirus detection, and eliminated the RNA extraction and purification step. Use of this method should facilitate detection of norovirus in fecal specimens and provide valuable information regarding the incidence of the virus. In addition, this method should be applicable for other RNA viruses. PMID:19878699

Nishimura, Naoyuki; Nakayama, Hiroyuki; Yoshizumi, Shima; Miyoshi, Masahiro; Tonoike, Hiroshi; Shirasaki, Yoshinari; Kojima, Kouichi; Ishida, Setsuko

2010-02-01

371

Adaptive Colorimetric Characterization of Digital Camera with White Balance  

Microsoft Academic Search

\\u000a A camera is an effective tool in capturing images for colorimetric use. However, the RGB signals generated by different cameras are not equal for the same scene. Therefore, cameras are characterized based on a\\u000a CIE standard colorimetric observer. This paper proposes a new method for obtaining camera transfer matrices under different\\u000a white balances using a 3×3 camera transfer matrix under

Soo-wook Jang; Eun-su Kim; Sung-hak Lee; Kyu-ik Sohng

2005-01-01

372

High throughput PCR detection of Xylella fastidiosa directly from almond tissues  

Microsoft Academic Search

Xylella fastidiosa, the causal agent of almond leaf scorch disease (ALSD), is currently re-emerging as a serious concern in California. Efficient pathogen detection is critical for ALSD epidemiological studies, particularly when a large sample size is involved. We here report a PCR procedure to detect X. fastidiosa directly from infected almond tissue without the laborious DNA extraction. Plant samples were

Jianchi Chen; Sam Livingston; Russell Groves; Edwin L. Civerolo

2008-01-01

373

Direct detection of Salmonella typhimurium on fresh produce using phage-based magnetoelastic biosensors  

Microsoft Academic Search

Current bacterial detection methods require the collection of samples followed by preparation and analysis in the laboratory, both time and labour consuming steps. More importantly, because of cost, only a limited number of samples can be taken and analyzed. This paper presents the results of an investigation to directly detect Salmonella typhimurium on fresh tomato surfaces using phage-based magnetoelastic (ME)

Suiqiong Li; Yugui Li; Huiqin Chen; Shin Horikawa; Wen Shen; Aleksandr Simonian; Bryan A. Chin

2010-01-01

374

Detection of 511 keV positron annihilation radiation from the galactic center direction  

Microsoft Academic Search

A balloon-borne germanium ..gamma..-ray telescope was flown over Alice Springs, Australia, in an attempt to detect spectral features from the galactic center (GC) direction. A 511 keV positron annihilation line was detected at a flux level of (1.22 +- 0.22) x 10⁻³ photons s⁻¹ cm⁻². Suggestive evidence for the detection of the three-photon positronium (ps) continuum is presented. A brief

M. Leventhal; C. J. MacCallum; P. D. Stang

1978-01-01

375

Improved direct back EMF detection for sensorless brushless DC (BLDC) motor drives  

Microsoft Academic Search

Improved back EMF detection circuits for low voltage\\/low speed and high voltage sensorless BLDC motor drives are presented in this paper. The improvements are based on the direct back EMF sensing method from our previous research work described in reference, which describes a technique for directly extracting phase back EMF information without the need to sense or re-construct the motor

Jianwen Shao; Dennis Nolan; Thomas Hopkins

2003-01-01

376

PREFACE: CYGNUS 2013: 4th Workshop on Directional Detection of Dark Matter  

NASA Astrophysics Data System (ADS)

It is a great pleasure to publish the proceedings of the 4th Workshop on Directional Detection of Dark Matter held in Toyama, Japan on 10-12 June 2013 (CYGNUS 2013). These proceedings contain written versions of the presentations made at CYGNUS 2013 as scientific outputs of the directional detection of dark matter. The GYGNUS workshop started in 2007 at Boulby Underground Laboratory (UK), followed by CYGNUS 2009 (MIT in Cambridge, Massachusetts, USA) and CYGNUS 2011 (AUSSOIS, France). CYGNUS 2013 was held by the combination of a two and a half days of scientific program and a half day visit to the underground laboratory (Kamioka Observatory) as a 'tradition' of CYGNUS workshops. The name 'CYGNUS' came from the fact that the 'dark matter wind' is expected to come from the direction of the constellation Cygnus due to the motion of the Solar system in the galaxy. A general aim of these CYGNUS workshops is to bring together the theoretical and experimental studies on the directional dark matter detection. Directional detection of dark matter is a promising approach to a 'clear detection' and also to 'further investigations' of galactic dark matter, or Weakly Interacting Massive Particles (WIMPs). Directional detection requires the simultaneous detection of the energy and track of low energy recoils. Among many technological challenges for the requirement above, three of them, namely size, background, and directionality (angular resolution and head-tail detection), are most important to demonstrate and improve the quality as a dark matter detector. In the workshop, up-to-date activities by the international reserchers are discussed. The workshop was a great success thanks to the oral contributions and fruitful discussions held throughout the workshop period. We hope that readers will remember and share the great enthusiasm shown during the CYGNUS 2013 workshop. The Editors Tatsuhiro Naka and Kentaro Miuchi

Naka, Tatsuhiro; Miuchi, Kentaro

2013-12-01

377

Highly sensitive and selective colorimetric sensing of antibiotics in milk.  

PubMed

Antibiotics residues in foods are very harmful to human beings. Determination of antibiotics residues relies largely on the availability of adequate analytical techniques. Currently, there is an urgent need for on site and real time detection of antibiotics in food. In this work, a novel one step synthesis of gold nanoparticles (AuNPs) was proposed using pyrocatechol violet (PCV) as a reducer agent. Highly sensitive and selective colorimetric detection of four antibiotics kanamycin mono sulfate (KA), neomycin sulfate (NE), streptomycin sulfate (ST) and bleomycin sulfate (BL) was realized during the formation of AuNPs. PCV has -OH groups and these antibiotics have -OH, -NH2, -NH- groups, so there may be some special hydrogen-bonding interactions between PCV and these antibiotics. Therefore, the presence of KA, NE, ST and BL would influence the synthesis of AuNPs, then the color and state of AuNPs would change, which could be observed with the naked eye or a UV-vis spectrophotometer. Results showed that A670 was linear with the logarithm of KA concentration in the range from 1.0×10(-8) to 5.0×10(-7)M and 5.0×10(-7) to 5.5×10(-5)M. The detection limit of KA was 1.0×10(-9)M (S/N=3). The coexisting substances including 1.0×10(-5)M phenylalanine, alanine, glycerol, glucose, Mg(2+), Ca(2+), Na(+), K(+), CO3(2-), SO4(2-), NO3(-), Cl(-) and Br(-) did not affect the determination of 1.0×10(-7)M antibiotics. In particular, the proposed method could be applied successfully to the detection of antibiotics in the pretreated liquid milk products. PMID:23639400

Zhang, Xiaofang; Zhang, Yang; Zhao, Hong; He, Yujian; Li, Xiangjun; Yuan, Zhuobin

2013-05-17

378

Prospects for detecting dark matter with neutrino telescopes in light of recent results from direct detection experiments  

SciTech Connect

Direct detection dark matter experiments, lead by the CDMS collaboration, have placed increasingly stronger constraints on the cross sections for elastic scattering of WIMPs on nucleons. These results impact the prospects for the indirect detection of dark matter using neutrino telescopes. With this in mind, we revisit the prospects for detecting neutrinos produced by the annihilation of WIMPs in the Sun. We find that the latest bounds do not seriously limit the models most accessible to next generation kilometer-scale neutrino telescopes such as IceCube. This is largely due to the fact that models with significant spin-dependent couplings to protons are the least constrained and, at the same time, the most promising because of the efficient capture of WIMPs in the Sun. We identify models where dark matter particles are beyond the reach of any planned direct detection experiments while within reach of neutrino telescopes. In summary, we find that, even when contemplating recent direct detection results, neutrino telescopes still have the opportunity to play an important as well as complementary role in the search for particle dark matter.

Halzen, Francis; /Wisconsin U., Madison; Hooper, Dan; /Fermilab

2005-10-01

379

Network community structure detection for directional neural networks inferred from multichannel multisubject EEG data.  

PubMed

In many neuroscience applications, one is interested in identifying the functional brain modules from multichannel, multiple subject neuroimaging data. However, most of the existing network community structure detection algorithms are limited to single undirected networks and cannot reveal the common community structure for a collection of directed networks. In this paper, we propose a community detection algorithm for weighted asymmetric (directed) networks representing the effective connectivity in the brain. Moreover, the issue of finding a common community structure across subjects is addressed by maximizing the total modularity of the group. Finally, the proposed community detection algorithm is applied to multichannel multisubject electroencephalogram data. PMID:24956610

Liu, Ying; Moser, Jason; Aviyente, Selin

2014-07-01

380

Signal averaging limitations in heterodyne- and direct-detection laser remote sensing measurements  

NASA Technical Reports Server (NTRS)

The improvement in measurement uncertainty brought about by the averaging of increasing numbers of pulse return signals in both heterodyne- and direct-detection lidar systems is investigated. A theoretical analysis is presented which shows the standard deviation of the mean measurement to decrease as the inverse square root of the number of measurements, except in the presence of temporal correlation. Experimental measurements based on a dual-hybrid-TEA CO2 laser differential absorption lidar system are reported which demonstrate that the actual reduction in the standard deviation of the mean in both heterodyne- and direct-detection systems is much slower than the inverse square-root dependence predicted for uncorrelated signals, but is in agreement with predictions in the event of temporal correlation. Results thus favor the use of direct detection at relatively short range where the lower limit of the standard deviation of the mean is about 2 percent, but advantages of heterodyne detection at longer ranges are noted.

Menyuk, N.; Killinger, D. K.; Menyuk, C. R.

1983-01-01

381

Improved Hough transform for curve detection based on directional control of connected regions  

NASA Astrophysics Data System (ADS)

Accurate and fast curve detection in images is a challenging computer vision problem. HT(Hough transform) is one of the most widely used techniques for curve detection. Existing HT-based methods have disadvantages of low accuracy and low speed. In this paper, a new and efficient Hough Transform for curve detection is presented. In view of kinematics, a curve can be regarded as movement trajectory of a given point, and point's velocity direction is the tangential direction of point on the smooth curve. Thus the main contributions are threefold. 1) We formulate the problem of curve detection as robustly fit curve in the connected region. 2) We propose the direction elements and directional control scheme to quickly discover the smooth curve. 3) We use a coarse-to-fine strategy to efficiently detect the final curve. We have tested our algorithm on simulated and natural image. Compared to other classical curve detection methods, experimental results indicated that our algorithm reduces the time cost and improves the detection accuracy greatly.

Shi, Yu; Yuan, Jie; Wang, Guoyou; Li, XiuHua

2012-09-01

382

Colorimetric characterisation of flatbed scanners for rock/sediment imaging  

NASA Astrophysics Data System (ADS)

Colour is a physical property of rocks and sediments that has the potential to provide key insights into composition, and by extension the physical and chemical processes governing deposition. The rapid, non-destructive measurement of colour using spectrophotometers is an increasingly popular way of generating long datasets (i.e. >1000 data points) suitable for high-resolution palaeoclimate analysis. Digital image analysis of core photographs is another commonly applied method of extracting colour information, but the application of flatbed scanners for direct rock and sediment colour measurement has not received widespread attention. Here, a simple calibration methodology is presented that demonstrates how scanners can be colorimetrically characterised. The technique offers a quantitative approach to colour analysis that is superior to the subjective comparison of rocks/sediments to Munsell colour charts. Moreover, the accuracy of the method makes rock and sediment scanning a viable alternative to colour analysis using spectrophotometers. The technique is applied to Late Pleistocene sediment samples from the Canterbury Basin, New Zealand (IODP 317, Site U1352B) to emphasise the utility and precision of the method and the tight relationship between sediment colour and composition.

Kemp, David B.

2014-06-01

383

Directly measuring the concurrence of atomic two-qubit states through the detection of cavity decay  

NASA Astrophysics Data System (ADS)

We present a scheme for directly measuring the concurrence of atomic two-qubit states (including pure states and mixed states) by detecting the photons leaking from the cavities where the atoms are located. We found that it is possible to encode the concurrence of two-atom entangled states in the photon detection results on the cavities. Cavity decay usually plays a passive role in quantum information processing, but in our scheme the decay of cavity mode plays a constructive role, and the state detection for trapped atoms were replaced by the photon detection. Our scheme is more implementable and may be feasible within the current technology.

Zhang, Li-Hua; Yang, Ming; Cao, Zhuo-Liang

2014-05-01

384

Basic design principles of colorimetric vision systems  

NASA Astrophysics Data System (ADS)

Color measurement is an important part of overall production quality control in textile, coating, plastics, food, paper and other industries. The color measurement instruments such as colorimeters and spectrophotometers, used for production quality control have many limitations. In many applications they cannot be used for a variety of reasons and have to be replaced with human operators. Machine vision has great potential for color measurement. The components for color machine vision systems, such as broadcast quality 3-CCD cameras, fast and inexpensive PCI frame grabbers, and sophisticated image processing software packages are available. However the machine vision industry has only started to approach the color domain. The few color machine vision systems on the market, produced by the largest machine vision manufacturers have very limited capabilities. A lack of understanding that a vision based color measurement system could fail if it ignores the basic principles of colorimetry is the main reason for the slow progress of color vision systems. the purpose of this paper is to clarify how color measurement principles have to be applied to vision systems and how the electro-optical design features of colorimeters have to be modified in order to implement them for vision systems. The subject of this presentation far exceeds the limitations of a journal paper so only the most important aspects will be discussed. An overview of the major areas of applications for colorimetric vision system will be discussed. Finally, the reasons why some customers are happy with their vision systems and some are not will be analyzed.

Mumzhiu, Alex M.

1998-10-01

385

Colorimetric determination of gabapentin in pharmaceutical formulation.  

PubMed

Three accurate, simple and precise colorimetric methods for the determination of gabapentin in capsules are developed. The first method is based on the reaction of gabapentin with vanillin (Duquenois reagent) in the presence of McIlvain buffer pH 7.5 and the color developed was measured at 376 nm. The linearity range was found to be 80-360 microg ml(-1). The second is based on the reaction of the primary amino group of gabapentin with ninhydrin reagent in N,N'-dimethylformamide (DMF) medium producing a colored product which absorbs maximally at 569 nm. Beer's law is obeyed in the concentration range 40-280 microg ml(-1) of gabapentin. The third method is based on the reaction of gabapentin with p-benzoquinone (PBQ) to form a colored product with lambda(max) at 369 nm. The products of the reaction were stable for 2 h at 30 degrees C, shifts of the wavelength of maximum absorbance were not observed for up to 24 h after starting the reaction. The absorbance is proportional to gabapentin concentration in the range 80-320 microg ml(-1). The optimum experimental parameters for the reactions have been studied. The validity of the described procedures was assessed. Statistical analysis of the results has been carried out revealing high accuracy and good precision. The suggested procedures could be used for the determination of gabapentin in capsules. The procedures were rapid, simple and suitable for quality control application. PMID:12560067

Abdellatef, Hisham E; Khalil, Hawa M

2003-02-01

386

Aspartic acid-promoted highly selective and sensitive colorimetric sensing of cysteine in rat brain.  

PubMed

Direct selective determination of cysteine in the cerebral system is of great importance because of the crucial roles of cysteine in physiological and pathological processes. In this study, we report a sensitive and selective colorimetric assay for cysteine in the rat brain with gold nanoparticles (Au-NPs) as the signal readout. Initially, Au-NPs synthesized with citrate as the stabilizer are red in color and exhibit absorption at 520 nm. The addition of an aqueous solution (20 ?L) of cysteine or aspartic acid alone to a 200 ?L Au-NP dispersion causes no aggregation, while the addition of an aqueous solution of cysteine into a Au-NP dispersion containing aspartic acid (1.8 mM) causes the aggregation of Au-NPs and thus results in the color change of the colloid from wine red to blue. These changes are ascribed to the ion pair interaction between aspartic acid and cysteine on the interface between Au-NPs and solution. The concentration of cysteine can be visualized with the naked eye and determined by UV-vis spectroscopy. The signal output shows a linear relationship for cysteine within the concentration range from 0.166 to 1.67 ?M with a detection limit of 100 nM. The assay demonstrated here is highly selective and is free from the interference of other natural amino acids and other thiol-containing species as well as the species commonly existing in the brain such as lactate, ascorbic acid, and glucose. The basal dialysate level of cysteine in the microdialysate from the striatum of adult male Sprague-Dawley rats is determined to be around 9.6 ± 2.1 ?M. The method demonstrated here is facile but reliable and durable and is envisaged to be applicable to understanding the chemical essence involved in physiological and pathological events associated with cysteine. PMID:23025476

Qian, Qin; Deng, Jingjing; Wang, Dalei; Yang, Lifen; Yu, Ping; Mao, Lanqun

2012-11-01

387

Edge-directed inference for microaneurysms detection in digital fundus images  

NASA Astrophysics Data System (ADS)

Microaneurysms (MAs) detection is a critical step in diabetic retinopathy screening, since MAs are the earliest visible warning of potential future problems. A variety of algorithms have been proposed for MAs detection in mass screening. Different methods have been proposed for MAs detection. The core technology for most of existing methods is based on a directional mathematical morphological operation called "Top-Hat" filter that requires multiple filtering operations at each pixel. Background structure, uneven illumination and noise often cause confusion between MAs and some non-MA structures and limits the applicability of the filter. In this paper, a novel detection framework based on edge directed inference is proposed for MAs detection. The candidate MA regions are first delineated from the edge map of a fundus image. Features measuring shape, brightness and contrast are extracted for each candidate MA region to better exclude false detection from true MAs. Algorithmic analysis and empirical evaluation reveal that the proposed edge directed inference outperforms the "Top-Hat" based algorithm in both detection accuracy and computational speed.

Huang, Ke; Yan, Michelle; Aviyente, Selin

2007-03-01

388

Improving sensitivity of gold nanoparticle based fluorescence quenching and colorimetric aptasensor by using water resuspended gold nanoparticle.  

PubMed

Gold nanoparticles (AuNPs) based fluorescence quenching or colorimetric aptasensor have been developed for many analytes recently largely because of the ease of detection, high sensitivity, and potential for high-throughput analysis. However, the effects of remnant non-AuNPs components in the colloid gold solution on these assays performance remain unclear. For the first time, we demonstrated that the remnant sodium citrate and the reaction products of three acids play counteractive roles in AuNPs based fluorescence quenching and colorimetric aptasensor in three ways in this study. First, the remnant sodium citrate in the colloid gold solution could increase the fluorescence intensity of FAM labeled on the aptamer that reduce the efficiency of AuNPs fluorescent quenching. Second, the reaction products of citric acid, HCl and ketoglutaric acid reduce the fluorescence recovery by quenching the fluorescence of FAM labeled on the aptamer dissociated from the surface of AuNPs upon addition of target. Lastly, the reaction products of three acids reduce the pH value of the colloid gold solution that reduce the sensitivity of AuNPs based colorimetric aptasensor by increasing the adsorption of aptamer to surface of AuNPs. With sulfadimethoxine and thrombin as model analytes, we found that water resuspended AuNPs can significantly increase the sensitivity by more than 10-fold for AuNPs based fluorescence quenching aptasensor. In the AuNPs based colorimetric aptasensor for sulfadimethoxine using the water resuspended AuNPs, the sensitivity also was increased by 10-fold compared with that of original AuNPs. The findings in this study provide theoretical guidance for further improving AuNPs based fluorescent quenching and colorimetric aptasensor by adjusting the composition of AuNPs solution. PMID:24064475

Liu, Jinchuan; Guan, Zheng; Lv, Zhenzhen; Jiang, Xiaoling; Yang, Shuming; Chen, Ailiang

2014-02-15

389

Colorimetric recognition of acetate anions in aqueous solution using charge neutral azo derivatives  

NASA Astrophysics Data System (ADS)

Two novel highly sensitive colorimetric acetate anion receptors: 4-phenylazo-2-hydroxy-benzaldehyde 4-nitrophenylhydrazone ( 1) and 4-phenylazo-2-hydroxy-benzaldehyde 2,4-dinitrophenylhydrazone ( 2) based on azo derivative have been designed and synthesized. UV-vis experiments show that receptor 1 and receptor 2 can selectively recognize acetate in DMSO and even in 9/1 DMSO/H 2O (v/v) mixtures. Meanwhile the color changes induced by anions can provide a way of detection by 'naked-eye'. The further insights to the nature of interactions between receptor 1, 2 and AcO - have been investigated by 1H NMR titration experiments.

Huang, Weiwei; Li, Yaping; Lin, Hai; Lin, Huakuan

2012-02-01

390

A novel colorimetric and fluorescent sensor based on calix[4]arene possessing triphenylamine units  

NASA Astrophysics Data System (ADS)

A novel colorimetric and fluorometric calix[4]arene probe (CTP) bearing triphenylamine units was synthesized in good yield and characterized by combination of 1H, 13C, APT, COSY, FTIR, HRMS, and UV-vis spectral data. Ion-binding studies of CTP were investigated in acetonitrile with a wide range of cations and anions and the recognition process was monitored by luminescence, UV-vis and 1H NMR spectral changes. CTP exhibited naked eye detection for Hg2+ ion. Also it showed a significant fluorescence quenching towards F- ion.

Erdemir, Serkan; Malkondu, Sait; Kocyigit, Ozcan; Al?c?, Onder

2013-10-01

391

A novel colorimetric and fluorescent sensor based on calix[4]arene possessing triphenylamine units.  

PubMed

A novel colorimetric and fluorometric calix[4]arene probe (CTP) bearing triphenylamine units was synthesized in good yield and characterized by combination of (1)H, (13)C, APT, COSY, FTIR, HRMS, and UV-vis spectral data. Ion-binding studies of CTP were investigated in acetonitrile with a wide range of cations and anions and the recognition process was monitored by luminescence, UV-vis and (1)H NMR spectral changes. CTP exhibited naked eye detection for Hg(2+) ion. Also it showed a significant fluorescence quenching towards F(-) ion. PMID:23770508

Erdemir, Serkan; Malkondu, Sait; Kocyigit, Ozcan; Al?c?, Onder

2013-10-01

392

A C3-symmetric colorimetric anion sensor bearing hydrazone groups as binding sites  

NASA Astrophysics Data System (ADS)

Tris-hydrazone ( 1) functioned as a colorimetric chemosensor for a variety of anions such as F -, AcO - and H 2PO 4-. The anion binding could be easily detected by naked-eye according to color changes. The high binding ability of the receptor 1 to anions was further investigated by UV-vis absorption spectroscopy in DMSO. The results of job plot of the receptor 1 with different anions demonstrated that the stoichiometry of the complex between 1 and F - was 1:1 ( 1:anion) and the stoichiometry of the other complexes studied was 1:3 ( 1:anion).

Shao, Jie; Qiao, Yanhong; Lin, Hai; Lin, Huakuan

2009-01-01

393

Spectroscopic and computational study of a naphthalene derivative as colorimetric and fluorescent sensor for bioactive anions.  

PubMed

The anion recognition property of a naphthalene based receptor (L) was investigated by naked-eye, UV-Vis, fluorescence, (1)H NMR and computational methods. The receptor L showed fluoride selective naked-eye detectable colorimetric and UV-Vis spectral changes over other tested anions due to the formation of hydrogen bonding complex in 1:1 stoichiometry and/or deprotonation between fluoride and the receptor. Interestingly, the fluorescence of L was quenched by fluoride but enhanced by acetate. PMID:23456416

Sharma, Darshna; Sahoo, Suban K; Bera, Rati Kanta; Kamal, Raj

2013-05-01

394

The Direct Detection Effect in the Hot-Electron Bolometer Mixer Sensitivity Calibration  

NASA Astrophysics Data System (ADS)

We investigate an error in the noise temperature measurements of the hot-electron bolometer mixers caused by the so-called "direct detection effect". The effect originates in the changing of the mixer parameters when the mixer is loaded on calibration black body sources at different temperatures (300 and 77 K). A correction factor was obtained from the mixer output power versus the bias current dependence, measured by: 1) the local oscillator (LO) power tuning: 2) mixer heating: and 3) application of an external RF source. Furthermore, the direct detection effect was assessed by elimination of the heterodyne response using a LO frequency, which is far off the mixer RF band. We show that the direct detection effect can be mitigated by using an isolator between the mixer and the IF amplifier.

Cherednichenko, Sergey; Drakinskiy, Vladimir; Berg, Therese; Kollberg, Erik L.; Angelov, Iltcho

2007-03-01

395

Doubling direct-detection data rate by polarization multiplexing of 16-QAM without active polarization control.  

PubMed

We introduce and simulate a technique enabling to utilize the polarization dimension in direct-detection optical transmission, supporting polarization multiplexing (POL-MUX) over direct-detection (DD) methods previously demonstrated for a single polarization such as direct-detection OFDM. POL-MUX is currently precluded in self-coherent DD with remotely transmitted pilot, as signal x pilot components may randomly fade out. We propose POL-MUX transmission of advanced modulation formats, such as 16-QAM and higher, by means of a novel low-complexity photonic integrated optical front-end and adaptive 3x2 MIMO DSP. The principle of operation is as follows: an additional X x Y cross-polarizations signal is generated, providing three projections onto an over-complete frame of three dependent vectors. This enables to resiliently reconstruct the received state of polarization even when the remotely transmitted pilot fades along one of the received polarization axes. PMID:24514795

Nazarathy, Moshe; Agmon, Amos

2013-12-30

396

Validation of direct plating of a stool sample as a method for Listeria monocytogenes detection.  

PubMed

The aim of current studies was to validate the direct plating of a stool sample for Listeria monocytogenes detection, using selective medium Palcam agar with Palcam selective supplement. Validation was performed using stool samples collected from healthy humans inoculated with Listeria sp. strains. Stool samples were frozen to determine the influence of freezing on method robustness. The presented research defines the Listeria monocytogenes limit of detection (LOD) as 10(3) cfu/g of stools for fresh and frozen samples. Repeatability and reproducibility of the method has been confirmed using statistical methods. We show the effectiveness of direct plating of stool samples on Palcam agar with Palcam selective supplement collected for Listeria monocytogenes detection. This method could be useful for this pathogen detection in stool samples collected from patients with diarrhoea. PMID:22462448

Madajczak, Grzegorz; Szych, Jolanta; Wójcik, Bo?ena; M?ka, ?ukasz; Formi?ska, Kamila

2012-03-23

397

A colorimetric assay method for Co2+ based on thioglycolic acid functionalized hexadecyl trimethyl ammonium bromide modified Au nanoparticles (NPs)  

NASA Astrophysics Data System (ADS)

A simple, rapid and sensitive colorimetric assay method for detection of Co2+ through thioglycollic acid (TGA) functionalized hexadecyl trimethyl ammonium bromide (CTAB) modified Au NPs has been discovered in our work. TGA functionalized CTAB modified Au NPs can be aggregated quickly in the presence of Co2+ through a cooperative metal-ligand interaction. Transmission electron microscope (TEM), energy dispersive X-ray spectroscopy (EDS), and UV-vis spectra were used to characterize the Au NPs aggregation. The presence of Co2+ is monitored by a colorimetric response of functionalized Au NPs, and had a detection limit of 3.0 × 10-7 M. Moreover, the selectivity of this method has been investigated by comparing with other metal ions (Hg2+, Na+, Cu2+, Cd2+, Ba2+, Pb2+, Mn2+, Ni2+, Zn2+, Fe2+ and Fe3+).

Zhang, Fuqiang; Zeng, Leyong; Zhang, Yingxin; Wang, Haiyan; Wu, Aiguo

2011-05-01

398

A one-tube multiplexed colorimetric strategy based on plasmonic nanoparticles combined with non-negative matrix factorization.  

PubMed

Herein, a one-tube colorimetric platform has been developed for the simultaneous determination of two analytes (DNA as model object) in one tube with picomolar sensitivity. SPR-active nanoparticles are used to encode reporter probes sensitive to oligonucleotides associated with hepatitis A virus Vall7 polyprotein gene (HVA) and hepatitis B virus surface-antigen gene (HVB) respectively and magnetic beads (MBs) serve as the removal tool. In this mixed nanoparticles based biosensor, the addition of target analytes could change the concentration of each nanoparticle, leading to different colors of the supernatant. The influence of spectral overlap has been eliminated by a non-negative matrix factorization (NMF). With the assistance of NMF, the limit of detection (LOD) can be determinated as pM level without amplification. On the whole, this nanosensor boasts the advantages of high sensitivity and low sample consumption. Simultaneous colorimetric detection and quantification of two molecules in one tube are demonstrated. PMID:25059165

Liu, Yizhen; Fang, Wei; Wu, Zitong; Zhou, Guohua; Yi, Wen; Zhou, Xiaodong; Shen, Aiguo; Hu, Jiming

2014-10-01

399

Direct immunofluorescence assay for rapid environmental detection of Vibrio cholerae O1  

Microsoft Academic Search

An immunofluorescence assay for direct detection ofV. cholerae O1 was developed using polyclonal antibodies raised against outer membrane proteins (OMPs) ofV. chloerae O1. Production of OMPs varied with growth media used; maximum production was found in tryptic soy broth. The detection system\\u000a was specific because no cross-reactivity was observed with other bacteria includingV. cholerae O139,E. coli, S. dysenteriae andSalmonella enterica

A. K. Goel; A. K. Tamrakar; D. V. Kamboj; L. Singh

2005-01-01

400

Direct detection of ultralow trace amounts of isocyanates in air using a fluorescent conjugated polymer.  

PubMed

A fluorescence sensory polymer containing the pentiptycene and tetraphenylethylene units linked by acetylene was synthesized for direct detection of isocyanates in air. Eight industrially available aliphatic and aromatic isocyanates were tested. The polymer film shows a rapid fluorescence quenching response to any type of isocyanates with a ppt level of detection limit, which is much lower than the permissible exposure limit of 5 ppb. PMID:24288055

Ghosh, Khama Rani; Saha, Sukanta Kumar; Gao, Jian Ping; Wang, Zhi Yuan

2014-01-21

401

A simple and direct electrochemical detection of interferon-? using its RNA and DNA aptamers  

Microsoft Academic Search

Tuberculosis is the most frequent cause of infection-related death worldwide. We constructed a simple and direct electrochemical sensor to detect interferon (IFN)-?, a selective marker for tuberculosis pleurisy, using its RNA and DNA aptamers. IFN-? was detected by its 5?-thiol-modified aptamer probe immobilized on the gold electrode. Interaction between IFN-? and the aptamer was recorded using electrochemical impedance spectroscopy and

Kyoungin Min; Minseon Cho; Se-Young Han; Yoon-Bo Shim; Jakang Ku; Changill Ban

2008-01-01

402

Development of a Direct In Situ PCR Method for Detection of Specific Bacteria in Natural Environments  

Microsoft Academic Search

We applied HNPP (2-hydroxy-3-naphthoic acid-2*-phenylanilide phosphate) to direct in situ PCR for the routine detection of specific bacterial cells at the single-cell level. PCR was performed on glass slides with digoxigenin-labeled dUTP. The digoxigenin-labeled PCR products were detected with alkaline phosphatase- labeled antidigoxigenin antibody and HNPP which was combined with Fast Red TR. A bright red fluorescent signal was produced

KATSUJI TANI; KEN KUROKAWA; MASAO NASU

1998-01-01

403

Advances and new directions in plant-wide disturbance detection and diagnosis  

Microsoft Academic Search

This article reviews advances in detection and diagnosis of plant-wide control system disturbances in chemical processes and discusses new directions that look promising for the future. Causes of plant-wide disturbances include non-linear limit cycles in control loops, controller interactions and tuning problems. The diagnosis of non-linearity, especially when due to valve stiction, has been an active area. Detection of controller

Nina F. Thornhill; Alexander Horch

2007-01-01

404

Application of IS900 PCR for Detection of Mycobacterium avium subsp. paratuberculosis Directly from Raw Milk  

Microsoft Academic Search

A polymerase chain reaction (PCR)-based assay was developed for detection of insertion sequence 900 (IS900 )o fMycobacterium avium subsp. paratuberculo- sis in raw milk. This IS900 PCR assay included DNA extraction and PCR assay using commercially available kits. The DNA extraction and PCR assay were opti- mized to detect the IS900 sequence directly from raw milk. The IS900 PCR assay

S. R. Pillai; B. M. Jayarao

2002-01-01

405

Directed Design of Experiments (DOE) for Determining Probability of Detection (POD) Capability of NDE Systems (DOEPOD)  

NASA Technical Reports Server (NTRS)

This viewgraph presentation reviews some of the issues that people who specialize in Non destructive evaluation (NDE) have with determining the statistics of the probability of detection. There is discussion of the use of the binominal distribution, and the probability of hit. The presentation then reviews the concepts of Directed Design of Experiments for Validating Probability of Detection of Inspection Systems (DOEPOD). Several cases are reviewed, and discussed. The concept of false calls is also reviewed.

Generazio, Ed

2007-01-01

406

A phase-modulated direct-detection fiber optical CATV transport system  

NASA Astrophysics Data System (ADS)

A fiber optical CATV transport system based on phase modulation (PM) and direct-detection schemes to reduce noise and distortion induced by systems is proposed and experimentally demonstrated. The architecture of the proposed systems is simplified by the fiber-dispersion-induced PM-to-intensity modulation (IM) conversion technique. As a result, the optical signal is detected directly by a photodiode (PD), without using the sophisticated and expensive delay interferometer (DI). Impressive performances of carrier-to-noise ratio (CNR), composite second-order (CSO), and composite triple beat (CTB) were obtained in our proposed systems over a 100-km single-mode fiber (SMF) transport.

Chen, Chia-Yi; Lu, Hai-Han; Lin, Chun-Yu; Wu, Kuan-Hung; Jhang, Tai-Wei; Ying, Cheng-Ling

2014-05-01

407

Young Infants Detect the Direction of Biological Motion in Point-Light Displays  

Microsoft Academic Search

pIn the present study, we examined if young infants can extract information regarding the directionality of biological motion. We report that 6-month-old infants can differentiate leftward and rightward motion from a movie depicting the sagittal view of an upright human point-light walker, walking as if on a treadmill. Inversion of the stimuli resulted in no detection of directionality. These findings

Valerie A. Kuhlmeier; Nikolaus F. Troje; Vivian Lee

2010-01-01

408

A directionally sensitive hot-wire probe for detection of flow reversal in highly unsteady flows  

Microsoft Academic Search

A three-element, directionally-sensitive hot-wire probe is described, which gives a definitive indication of both the direction and magnitude of the instantaneous velocity in highly unsteady, boundary-layer flows. Data are presented showing its performance on a dynamically stalling airfoil. A discussion of alternative approaches to flow-reversal detection is presented. The probe is recommended for use in any highly unsteady flow when

L. W. Carr; W. J. McCroskey

1979-01-01

409

Colorimetric and Fluorescent Sensing of SCN Based on meso-Tetraphenylporphyrin\\/meso-Tetraphenylporphyrin Cobalt(II) System  

Microsoft Academic Search

An approach for colorimetric and fluorescent sensing of thiocyanate (SCN - ) has been proposed based on the competitive-displacement strategy between meso -tetraphenylporphyrin (TPP) and meso -tetraphenylporphyrin cobalt(II) (CoTPP). In THF-water solution, TPP emits strong fluorescence at 651 nm; however, the fluorescence was quenched stepwise by CoTPP, and then restored by SCN - , the detection limit is 6.0 ×

Ying Zhang; Hua Wang; Rong H. Yang

2007-01-01

410

Selective colorimetric sensing of histidine in aqueous solutions using cysteine modified silver nanoparticles in the presence of Hg2+  

Microsoft Academic Search

Cysteine modified Ag nanoparticles were prepared in aqueous solution, via one-pot protocol, which were characterized by transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) and ultraviolet-visible spectroscopy (UV-vis). The nanoparticles provided a simple and rapid strategy to detect histidine (His) visually with the help of Hg2+ ions in solution. The colorimetric sensor allows a rapidly quantitative assay of histidine down

Haibing Li; Yinghui Bian

2009-01-01

411

Selective colorimetric sensing of cysteine in aqueous solutions using silver nanoparticles in the presence of Cr 3+  

Microsoft Academic Search

We here in report an extensive study on the development of a highly facile, selective and sensitive colorimetric probe for cysteine detection using silver nanoparticles (Ag NPs). The efficacy of the process relies upon the surface plasmon resonance properties of Ag NPs and the interaction of Ag–cysteine complex with chromium ions (Cr3+) in a ratio of 2:1. In the presence

Aswathy Ravindran; Vinayak Mani; N. Chandrasekaran; Amitava Mukherjee

2011-01-01

412

Direct isolation of DNA from patient stools for polymerase chain reaction detection of Cryptosporidium parvum.  

PubMed

Although polymerase chain reaction (PCR) can sensitively detect parasitic or other infections, its use with fecal samples is extremely limited, primarily because of the presence of substances that inhibit DNA extension. Here an improved protocol is reported for directly isolating DNA from aged or fresh formalin-fixed stools, which can then be used to detect Cryptosporidium parvum by nested PCR. This method is highly reproducible, sensitive, and specific. It detects <1 pg of C. parvum DNA in human stool, and there are no cross-reactions with other parasites commonly found there. PMID:9593044

Zhu, G; Marchewka, M J; Ennis, J G; Keithly, J S

1998-05-01

413

Signal-carrier interleaved optical OFDM for direct detection optical communication.  

PubMed

We propose signal-carrier interleaved (SCI) optical OFDM for direct detected transmission systems. Such a scheme can be considered as a variation of self-coherent detection where the carrier and signal are supplied at the transmitter and extracted at the receiver for coherent-like detection. This provides high OSNR sensitivity while maintaining very low carrier-to-signal power ratio (CSR). Our experiment results show that with 0 dB CSR, 43.2 Gb/s 16 QAM OFDM signal can be successfully delivered over 80 km standard single mode fiber (SSMF) with 24 dB OSNR requirements at 7% FEC limit. PMID:24514843

Chen, Xi; Che, Di; Li, An; He, Jiayuan; Shieh, William

2013-12-30

414

The ArDM, a ton-scale liquid argon experiment for direct dark matter detection  

NASA Astrophysics Data System (ADS)

The ArDM project aims at developing and operating large noble liquid detectors to search for direct evidence of Weakly Interacting Massive Particles (WIMP) as Dark Matter in the Universe. The initial goal is to design, assemble and operate an approximately 1 ton liquid argon prototype based on the double-phase detection principle to demonstrate the feasibility of a ton-scale experiment with the required performance to efficiently detect and sufficiently discriminate backgrounds for a successful WIMP detection. The detector will independently measure the primary scintillation light and the ionization charge. This paper will mainly describe the concept, R&D results and status of the charge read out system.

Otyugova, P.; Ar DM Collaboration

2008-07-01

415

Microneedle Biosensor: A Method for Direct Label-free Real Time Protein Detection  

PubMed Central

Here we present the development of an array of electrical micro-biosensors in a microfluidic channel, called microneedle biosensors. A microneedle biosensor is a real-time, label-free, direct electrical detection platform, which is capable of high sensitivity detection, measuring the change in ionic current and impedance modulation, due to the presence or reaction of biomolecules such as proteins and nucleic acids. In this study, we successfully fabricated and electrically characterized the sensors and demonstrated successful detection of target protein. In this study, we used biotinylated bovine serum albumin as the receptor and streptavidin as the target analyte

Esfandyarpour, Rahim; Esfandyarpour, Hesaam; Javanmard, Mehdi; Harris, James S.; Davis, Ronald W.

2012-01-01

416

Label-free colorimetric aptasensor for IgE using DNA pseudoknot probe.  

PubMed

The development of simple and low-cost approaches to the detection of immunoglobulin E (IgE) would provide a method for the early diagnosis and prevention of atopic diseases. The current methods of detection are generally tedious, multi-step processes and are limited by the high cost of the labeled proteins. We describe here a label-free structure-switching colorimetric method for the simple measurement of IgE using DNA pseudoknot probes and gold nanoparticles. In the absence of a target the IgE aptamer probe adopts a pseudoknot conformation that dissociates a capture probe from the unmodified gold nanoparticles. However, when IgE binds to the aptamer probe, the pseudoknot is resolved, leading to a favorable hybridization between the 3' terminal loop of the aptamer probe and the capture probe; this induces the aggregation of the gold nanoparticles. As a result, the colorimetric IgE sensor using this structure-switching mechanism is sensitive, specific and convenient, and the assay works even when challenged with complicated biological matrixes such as vaginal fluids. The proposed method is expected to be of great clinical value for IgE detection and could be used, after appropriate design, for sensing applications of other structured aptamers. PMID:24821053

Chang, Chia-Chen; Chen, Chen-Yu; Zhao, Xihong; Wu, Tzu-Heng; Wei, Shih-Chung; Lin, Chii-Wann

2014-06-01

417

Colorimetric sensor based on two optical fiber couplers  

NASA Astrophysics Data System (ADS)

The aim of the paper is to present an idea of a low-cost optical fiber colorimetric pH sensor (with disposable probe). Most of colorimetric sensors consist of two fibers: the illuminating one and one for collecting reflected light. Only one optical fiber is used as a sensing probe in our pH sensor. The end of the fiber is covered by a pH-sensing membrane, which is made of polyvinyl chloride. The colorimetric indicator (bromothymol blue) was immobilized on an ion- exchange resin. The sensing fiber is connected with two optical fiber couplers (type Y). The first coupler guides analytical and reference wavelengths from the light emitting diodes (LED) and the second one transmits light to the photodetector. Only one photodetector is used. Optical signals are filtered electronically because the LEDs are modulated at different frequencies. The results of the measuring tests of the sensor are presented.

Dybko, Artur; Maciejewski, Janusz; Romaniuk, Ryszard S.; Wroblewski, Wojciech

1994-02-01

418

Colorimetric determination of ferrous-ferric ratio in glass  

SciTech Connect

This memorandum describes a simple, rapid colorimetric procedure that can be used for analysis of vitrified melter feed. This method can replace the Moessbauer spectroscopy method for routine DWPF process control analysis. A colorimetric method has been developed that is recommended as a replacement for Moessbauer spectroscopy for process control measurements of the Fe(II)/Fe(III) ratio of melter feed for the DWPF analytical laboratory. The results agree satisfactorily with Moessbauer values. The method is suitable for remote operation and has several advantages. The total time involved is less than 30 minutes. Quantitative measurements of samples, reagents, and dilutions are unnecessary because only the ratio value is required and both Fe(II) and total Fe are measured on the same solution. Small samples (<3 mg total Fe) are required, minimizing radiation exposure, because of the high sensitivity of the colorimetric method. Relative precision and relative accuracy are about {plus minus}5%.

Baumann, E W

1987-02-20

419

Gene doping detection: evaluation of approach for direct detection of gene transfer using erythropoietin as a model system.  

PubMed

As clinical gene therapy has progressed toward realizing its potential, concern over misuse of the technology to enhance performance in athletes is growing. Although 'gene doping' is banned by the World Anti-Doping Agency, its detection remains a major challenge. In this study, we developed a methodology for direct detection of the transferred genetic material and evaluated its feasibility for gene doping detection in blood samples from athletes. Using erythropoietin (EPO) as a model gene and a simple in vitro system, we developed real-time PCR assays that target sequences within the transgene complementary DNA corresponding to exon/exon junctions. As these junctions are absent in the endogenous gene due to their interruption by introns, the approach allows detection of trace amounts of a transgene in a large background of the endogenous gene. Two developed assays and one commercial gene expression assay for EPO were validated. On the basis of ability of these assays to selectively amplify transgenic DNA and analysis of literature on testing of gene transfer in preclinical and clinical gene therapy, it is concluded that the developed approach would potentially be suitable to detect gene doping through gene transfer by analysis of small volumes of blood using regular out-of-competition testing. PMID:20463760

Baoutina, A; Coldham, T; Bains, G S; Emslie, K R

2010-08-01

420

FRET based tri-color emissive rhodamine-pyrene conjugate as an Al3+ selective colorimetric and fluorescence sensor for living cell imaging.  

PubMed

A rhodamine-pyrene hybrid molecule acts as a colorimetric and fluorimetric sensor for Al(3+) through time dependent PET-CHEF and FRET processes associated with tri-color emission. Intracellular Al(3+) has been visualized through time dependent blue-green-red emission. The lowest limit of detection for Al(3+) is 0.02 ?M. PMID:23925436

Sahana, Animesh; Banerjee, Arnab; Lohar, Sisir; Banik, Avishek; Mukhopadhyay, Subhra Kanti; Safin, Damir A; Babashkina, Maria G; Bolte, Michael; Garcia, Yann; Das, Debasis

2013-10-01

421

Zn(II) based colorimetric sensor for ATP and its use as a viable staining agent in pure aqueous media of pH 7.2.  

PubMed

Selective colorimetric detection of ATP in physiological conditions by a Zn(II)-based receptor is reported. This reagent was found to be non-toxic to the living cells and could be used for studying the growth of the yeast cells. PMID:21049131

Mahato, Prasenjit; Ghosh, Amrita; Mishra, Sanjiv K; Shrivastav, Anupama; Mishra, Sandhya; Das, Amitava

2010-12-28

422

Detection of intracytoplasmic cytokine using flow cytometry and directly conjugated anti-cytokine antibodies  

Microsoft Academic Search

Recently, there have been several reports demonstrating improvements in the flow cytometric detection of intracellular cytokines. These advances, although significant, have not yielded techniques that have easily been translated into broad use. To address this issue, we have coupled a fixation and permeabilization method with the use of directly labelled monoclonal anti-cytokine antibodies, providing both improved signal and simpler staining.

Calman Prussin; Dean D. Metcalfe

1995-01-01

423

Experimental data of a directional borehole radar system for UXO detection  

Microsoft Academic Search

Ground penetrating radar (GPR) is a well-known method for exploring the subsurface. Typically, the antenna system is located at the surface. This approach is not feasible if the target of interest i