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Polymeric assay film for direct colorimetric detection  


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)



Polymeric assay film for direct colorimetric detection  


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)



Direct colorimetric detection of virus by a polymerized bilayer assembly.  

National Technical Information Service (NTIS)

Screening and detecting virus by receptor-ligand interactions presents an important challenge in medical and environmental diagnostics, and in drug development. We have developed a direct calorimetric detection method based on a polymeric bilayer assembly...

D. H. Charych J. O. Nagy W. Spevak J. Ager M. D. Bednarski



Sol-gel matrices for direct colorimetric detection of analytes  


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)



Sol-Gel Matrices For Direct Colorimetric Detection Of Analytes  


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)



Direct detection of ?-agonists by use of gold nanoparticle-based colorimetric assays.  


?-Agonists fed to animals for human consumption pose a serious threat to human health. Fast, broad-spectrum detection methods are needed for on-site screening of various types of ?-agonists from animal feeds, meats, and animal body fluids. We developed a colorimetric assay that uses gold nanoparticle (AuNP) plasmon absorption to realize quick detection of ?-agonists from liquid samples. ?-Agonists showed the capability of directly reducing HAuCl(4) into atomic gold, which involved oxidation of the amine or phenol group on the benzene ring of the ?-agonists. The resulting atomic gold formed AuNPs spontaneously, which had strong plasmon absorption at 528 nm. The linear relationship between the concentrations of ?-agonists and the AuNPs plasmon absorbance granted quantitative determination of ?-agonists in solution. The AuNPs colorimetric assay showed different sensitivities toward ?-agonists with different substituent groups on the aromatic ring. ?-Agonists with phenol groups had a lower limit of quantitation (LOQ) than those with amine groups. High-resolution transmission electron microscopy (TEM) images revealed the sizes of the AuNPs were in the range 15-25 nm, while X-ray energy-dispersive spectroscopic data suggested the smaller particles observed in TEM with lower contrast may be salt particles from the buffer solution. The developed colorimetric assay can potentially be used for the detection of ?-agonists and their analogues from serum, urine, and other liquid samples in the presence of interference from common antibiotics and glucose. PMID:21846151

He, Pingli; Shen, Li; Liu, Rongyuan; Luo, Zhiping; Li, Zhen



Zeta potential based colorimetric immunoassay for the direct detection of diabetic marker HbA1c using gold nanoprobes.  


A one-step homogeneous colorimetric immunoassay format coupled with zeta potential measurements for determination of specific diabetic biomarker glycated hemoglobin (HbA1c) using functionalised gold nanoparticles as bioprobes is reported. The assay exhibited an excellent sensitivity based on absorbance and zeta potential measurements showing the dynamic response range from 0.001-0.004 mg mL(-1) for HbA1c with a detection limit of 0.0015 mg mL(-1). PMID:20571696

Wangoo, Nishima; Kaushal, Jyotsna; Bhasin, K K; Mehta, S K; Suri, C Raman



Emergency First Responders' Experience with Colorimetric Detection Methods  

SciTech Connect

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

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



Tree-shaped paper strip for semiquantitative colorimetric detection of protein with self-calibration  

Microsoft Academic Search

This paper described a convenient semiquantitative method for colorimetric detection of protein with self-calibration integrated on the test strip. Hydrophilic paper was employed as microfluidic device for running colorimetric assay, tree-shaped design was developed to ensure uniform microfluidic flow for multiple branches. The approach was validated with bovine serum albumin (BSA) colorimetric detection, and colorimetric results observed by naked eyes

Wei Wang; Wen-Ya Wu; Jun-Jie Zhu



Optical fiber waveguide sensor for the colorimetric detection of ammonia  

NASA Astrophysics Data System (ADS)

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

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



Preoxidation for colorimetric sensor array detection of VOCs.  


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



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.



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


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

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



Colorimetric detection of human papilloma virus by double isothermal amplification.  


We developed a polymerase reaction free, low-cost and sensitive assay for the colorimetric detection of Human Papilloma Virus (HPV), based on the use of a smart design exploiting magnetic microbeads, chimeric RNA/DNAzyme oligonucleotides, and double signal amplification. This method allows obtaining a fast response with a detection limit of 10 pM, avoiding the amplification of the target via traditional PCR. PMID:24098886

Persano, Stefano; Valentini, Paola; Kim, Joong Hyun; Pompa, Pier Paolo



Colorimetric viral detection based on sialic acid stabilized gold nanoparticles.  


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 (hemagglutination 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. PMID:23208092

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



Beryllium colorimetric detection for high speed monitoring of laboratory environments.  


The health consequences of beryllium (Be2+) exposure can be severe. Beryllium is responsible for a debilitating and potentially fatal lung disease, chronic beryllium disease (CBD) resulting from inhalation of beryllium particles. The US Code of Federal Register (CFR), 10 CFR 850, has established a limit of 0.2 microg beryllium/100 cm(2) as the maximum amount of beryllium allowable on surfaces to be released from beryllium work areas in Department of Energy (DOE) facilities. The analytical technique described herein reduces the time and cost of detecting beryllium on laboratory working surfaces substantially. The technique provides a positive colorimetric response to the presence of beryllium on a 30.5 cm x 30.5 cm (1 ft(2)) surface at a minimum detection of 0.2 microg/100 cm(2). The method has been validated to provide positive results for beryllium in the presence of excess iron, calcium, magnesium, copper, nickel, chromium and lead at concentrations 100 times that of beryllium and aluminum and uranium (UO2(2+)) at lesser concentrations. The colorimetric detection technique has also been validated to effectively detect solid forms of beryllium including Be(OH)2, BeCl2, BeSO4, beryllium metal and BeO. PMID:12137989

Taylor, Tammy P; Sauer, Nancy N



Colorimetric Detection and Identification of Natural and Artificial Sweeteners  

Microsoft Academic Search

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

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



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


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



Tree-shaped paper strip for semiquantitative colorimetric detection of protein with self-calibration.  


This paper described a convenient semiquantitative method for colorimetric detection of protein with self-calibration integrated on the test strip. Hydrophilic paper was employed as microfluidic device for running colorimetric assay, tree-shaped design was developed to ensure uniform microfluidic flow for multiple branches. The approach was validated with bovine serum albumin (BSA) colorimetric detection, and colorimetric results observed by naked eyes were consistent with that from apparatus. The device could be coupled with digital transmission of images for remote monitoring system for diagnosis, food control, and environmental analysis. PMID:20444459

Wang, Wei; Wu, Wen-Ya; Wang, Wei; Zhu, Jun-Jie



Colorimetric detection of glucose and an assay for acetylcholinesterase with amine-terminated polydiacetylene vesicles  

Microsoft Academic Search

The colorimetric response of amine-terminated polydiacetylene (PDA) vesicles was initially demonstrated by varying the pH\\u000a of the solution. Convenient colorimetric methods to detect glucose and acetylcholinesterase (AChE) activity were successfully\\u000a established using amine-terminated PDA vesicles by taking advantage of the following features: (1) the amine-terminated PDA\\u000a vesicles undergo a colorimetric transition as the pH of the solution changes; (2) glucose

WangXin Xue; DeQing Zhang; GuanXin Zhang; DaoBen Zhu



Point-of-care colorimetric detection with a smartphone.  


Paper-based immunoassays are becoming powerful and low-cost diagnostic tools, especially in resource-limited settings. Inexpensive methods for quantifying these assays have been shown using desktop scanners, which lack portability, and cameras, which suffer from the ever changing ambient light conditions. In this work, we introduce a novel approach of quantifying colors of colorimetric diagnostic assays with a smartphone that allows high accuracy measurements in a wide range of ambient conditions, making it a truly portable system. Instead of directly using the red, green, and blue (RGB) intensities of the color images taken by a smartphone camera, we use chromaticity values to construct calibration curves of analyte concentrations. We demonstrate the high accuracy of this approach in pH measurements with linear response ranges of 1-12. These results are comparable to those reported using a desktop scanner or silicon photodetectors. To make the approach adoptable under different lighting conditions, we developed a calibration technique to compensate for measurement errors due to variability in ambient light. This technique is applicable to a number of common light sources, such as sun light, fluorescent light, or smartphone LED light. Ultimately, the entire approach can be integrated in an "app" to enable one-click reading, making our smartphone based approach operable without any professional training or complex instrumentation. PMID:22996728

Shen, Li; Hagen, Joshua A; Papautsky, Ian



Gold nanoparticles-based colorimetric assay for rapid detection of Salmonella species in food samples  

Microsoft Academic Search

A rapid, sensitive and cost-effective method was developed for detection of foodborne pathogens, particularly Salmonella species. The method utilizes single stranded DNA (ssDNA) probes and non-functionalized gold nanoparticles to provide a colorimetric\\u000a assay for the detection of PCR amplified DNA. Different food samples were tested with the PCR-based colorimetric assay parallel\\u000a with the conventional culture method. The sensitivity and specificity

Dinesh Prasad; Shankaracharya; Ambarish Sharan Vidyarthi


Label-free aptamer-based colorimetric detection of mercury ions in aqueous media using unmodified gold nanoparticles as colorimetric probe  

Microsoft Academic Search

We report a simple and sensitive aptamer-based colorimetric detection of mercury ions (Hg2+) using unmodified gold nanoparticles as colorimetric probe. It is based on the fact that bare gold nanoparticles interact\\u000a differently with short single-strand DNA and double-stranded DNA. The anti-Hg2+ aptamer is rich in thymine (T) and readily forms T–Hg2+–T configuration in the presence of Hg2+. By measuring color

Li Li; Baoxin Li; Yingying Qi; Yan Jin



Development of Colorimetric Ozone Detection Papers with High Ultraviolet Resistance Using Ultraviolet Absorbers  

Microsoft Academic Search

Two types of colorimetric ozone detection paper with high resistance to ultraviolet (UV) light have been developed for outdoor ozone detection. These detection papers incorporate indigo carmine and UV absorbers (UVAs). When exposed to ozone, the papers change color from blue to white, and the ozone concentration can be determined by measuring the reflectance of the papers. However, indigo carmine

Takashi Miwa; Yasuko Yamada Maruo; Kunihiko Akaoka; Tatsuya Kunioka; Jiro Nakamura; Remedios ez; Sebastian Caparro´s; Manuel Díaz; Johanna Gietl; Otto Klemm; Xinke Wang; Yinping Zhang; Jace Bauer; Xiao-Ying Yu; Robert Cary; Nels Laulainen; Carl Berkowitz; Juan Goncalves; Rakesh Govind; Chatchawan Vongmahadlek; Pham Thao; Boonsong Satayopas; Narisara Thongboonchoo; H. Frey; Po-Yao Kuo; Mohammad Al-Hamdan; William Crosson; Ashutosh Limaye; Douglas Rickman; Dale Quattrochi; Maurice Estes; Judith Qualters; Amber Sinclair; Dennis Tolsma; Kafayat Adeniyi; Amanda Niskar; Meng Yao; Qiong Zhang; David Hand; David Perram; Roy Taylor



Fluorescent and colorimetric sensors for detection of lead, cadmium, and mercury ions.  


Exposure to even very low levels of lead, cadmium, and mercury ions is known to cause neurological, reproductive, cardiovascular, and developmental disorders, which are more serious problems for children particularly. Accordingly, great efforts have been devoted to the development of fluorescent and colorimetric sensors, which can selectively detect lead, cadmium, and mercury ions. In this critical review, the fluorescent and colorimetric sensors are classified according to their receptors into several categories, including small molecule based sensors, calixarene based chemosensors, BODIPY based chemosensors, polymer based chemosensors, DNA functionalized sensing systems, protein based sensing systems and nanoparticle based sensing systems (197 references). PMID:22184584

Kim, Ha Na; Ren, Wen Xiu; Kim, Jong Seung; Yoon, Juyoung



A colorimetric receptor combined with a microcantilever sensor for explosive vapor detection  

NASA Astrophysics Data System (ADS)

Substantial effort has been devoted to the synthesis of molecular receptors that can function as chemosensors for nitroaromatic explosives. In spite of several advantages, these receptors suffer from low sensitivity and difficulties translating the response into the gas phase. We have combined tetrathiafulvalene-functionalized calix[4]pyrrole, a colorimetric receptor, with a polyimide microcantilever, that includes a mechanical stress sensing element. The resulting system is capable of detecting 10 ppb trinitrobenzene vapor. This represents a 30-fold improvement relative to the receptor in halogenated solvents, suggesting that this approach can provide a solution to translating the chemical response of colorimetric chemosensors into practical devices.

Zhu, Weibin; Park, Jung Su; Sessler, Jonathan L.; Gaitas, Angelo



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


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



Flow injection analysis of nanomolar level orthophosphate in seawater with solid phase enrichment and colorimetric detection  

Microsoft Academic Search

Phosphomolybdenum blue (PMB) paired with cetyltrimethylammonium bromide (CTAB) can be extracted using a solid phase extraction technique on C18 sorbent. Based on this, a novel on-line solid phase extraction method coupled with flow injection (FI) analysis and colorimetric detection has been established to determine nanomolar level orthophosphate in seawater. A stopped flow technique was employed to assure the complete formation

Ying Liang; Dongxing Yuan; Quanlong Li; Qingmei Lin



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

NASA Astrophysics Data System (ADS)

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

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



Two New Colorimetric Methods for Early Detection of Vancomycin and Oxacillin Resistance in Staphylococcus aureus  

PubMed Central

We developed two colorimetric methods for the detection of vancomycin- and oxacillin-resistant Staphylococcus aureus in ?6 h: (i) a nitrate reductase assay and (ii) a resazurin microplate method. MICs agreed with results obtained by CLSI methods for oxacillin. However, detection of vancomycin resistance required a larger inoculum. These methods may be recommended for the detection of vancomycin- and oxacillin-resistant S. aureus.

Coban, Ahmet Y.; Bozdogan, Bulent; Cihan, Cigdem Cekic; Cetinkaya, Ebru; Bilgin, Kemal; Darka, Ozge; Akgunes, Alper; Durupinar, Belma; Appelbaum, Peter C.



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



Detection of K- ras point mutation by enriched PCR–colorimetric plate assay  

Microsoft Academic Search

Point mutations in the K-rasgene are frequently observed in a variety of human malignancies, including colorectal and pancreatic cancers. In this paper, we describe a sensitive procedure for the detection of point mutations of codon 12 of the K-rasgene. The assay employs a single-tube enriched PCR procedure, coupled to colorimetric detection. In the enriched PCR procedure, the first round of

Fernando S Santiago; Alison V Todd; Nicholas J Hawkins; Robyn L Ward



Miniaturized 96-well ELISA chips for staphylococcal enterotoxin B detection using portable colorimetric detector.  


A previously developed fluorescence sensing platform, combining spatial illumination using electroluminescence (EL) semiconductor strips with charge coupled device (CCD)-based detection (EL-CCD), was adapted to a new 96-well chip for colorimetric immunological assays, enhancing the capabilities of the EL-CCD platform. The modified system was demonstrated using a colorimetric-based enzyme linked immunosorbent assay (ELISA) for detection of staphylococcal enterotoxin B (SEB). Limits of detection (LODs) of 3.9 ng/mL (+/-2.4 ng/mL) SEB were determined with the ELISA chip measured using the EL-CCD platform, following a standard 4-h ELISA protocol. The LODs were comparable to those obtained using standard 96-well ELISA plates measured using a standard laboratory 96-well plate reader. The miniature 96-well ELISA chip however required as little as 5-microL samples, representing a tenfold reduction in sample volume compared to a standard 96-well ELISA plates. The ELISA chip also demonstrated detection of SEB spiked into various food matrices (milk, mushrooms, and mayonnaise) using limited-to-no sample preparation, with LODs ranging from 3.9 to 18.5 ng/mL depending on the matrix. The EL-CCD platform is versatile, capable of multi-mode detection (e.g., fluorescent and colorimetric along with solution and solid phase assays), and could readily be applied to other field portable or point-of-care applications. PMID:19290511

Sapsford, Kim E; Francis, Jesse; Sun, Steven; Kostov, Yordan; Rasooly, Avraham



Colorimetric platform for visual detection of cancer biomarker based on intrinsic peroxidase activity of graphene oxide  

Microsoft Academic Search

A new colorimetric immunoassay for the detection of cancer biomarker prostate specific antigen (PSA) was developed based on the intrinsic peroxidase activity of graphene oxide (GO). GO can catalyze the reaction of hydroquinone in the presence of H2O2 to produce a brown color solution. Secondary antibody (Ab2) functionalized GO (GO-Ab2) was used as label for the immunoassay, while magnetic bead

Fengli Qu; Ting Li; Minghui Yang



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

Microsoft Academic Search

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

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



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

Microsoft Academic Search

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

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



Simple colorimetric bacterial detection and high-throughput drug screening based on a graphene-enzyme complex  

NASA Astrophysics Data System (ADS)

A simple, colorimetric, sensitive, cost-effective and high-throughput system based on a positively charged graphene oxide-enzyme complex was developed for bacterial detection and drug screening.A simple, colorimetric, sensitive, cost-effective and high-throughput system based on a positively charged graphene oxide-enzyme complex was developed for bacterial detection and drug screening. Electronic supplementary information (ESI) available: Experimental details and supporting figures and procedures. See DOI: 10.1039/c2nr32704j

Li, Juan; Wu, Ling-Jie; Guo, Shan-Shan; Fu, Hua-E.; Chen, Guo-Nan; Yang, Huang-Hao



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



Efficient colorimetric and fluorescent detection of fluoride in DMSO-water mixtures with arylaldoximes.  


Fluoride detection through hydrogen bonding or deprotonation is most commonly achieved using amide, urea or pyrrole derivatives. The sensor molecules are often complex constructs and several synthetic steps are required for their preparation. Here we report the discovery that simple arylaldoximes have remarkable properties as fluoride anion sensors, providing distinct colorimetric or fluorescent readouts, depending on the structure of the arylaldoxime. The oximes showed exceptional selectivity towards fluoride over other typical anions, and low detection limits for fluoride in both DMSO and DMSO-water mixtures were obtained. PMID:24132123

Rosen, Christian B; Hansen, Dennis J; Gothelf, Kurt V



Detection of Mycoplasma pneumoniae by colorimetric loop-mediated isothermal amplification.  


Mycoplasma pneumoniae (M. pneumoniae) is one of the most important pathogens that cause respiratory tract infection in children and adults. In this study, we describe a rapid and sensitive colorimetric loop mediated isothermal amplification (LAMP) method to detect M. pneumoniae. The specificity and sensitivity of this assay were detected with 21 common respiratory pathogens and 39 M. pneumoniae DNA. The sensitivity of LAMP was 100% among 39 M. pneumoniae isolates and the specificity was 100% among 9 members of other Mycoplasma and 12 common respiratory pathogens. The lowest detectable limit (LDL) of this assay was 102 copies, which detected by a series of standard M. pneumoniae DNA. To evaluate the clinical applicability of the LAMP assay, a total of 80 clinical samples were examined by conventional PCR, real-time PCR and the LAMP assays, respectively. The positive rates were 15.0%, 32.5% and 26.3%, respectively. This colorimetric LAMP assay demonstrated a high level of sensitivity comparable with that of conventional PCR for the detection of M. pneumoniae. It is a valuable method for simple, cost-effective and rapid detection of M. pneumoniae in the rural areas and basic clinical of China. PMID:23529294

Zhao, Fei; Liu, Zhong; Gu, Yixin; Yang, Yuelian; Xiao, Di; Tao, Xiaoxia; Meng, Fanliang; He, Lihua; Zhang, Jianzhong



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


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

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



Recent progress in luminescent and colorimetric chemosensors for detection of thiols.  


In the past few decades, the development of optical probes for thiols has attracted great attention because of the biological importance of the thiol-containing molecules such as cysteine (Cys), homocysteine (Hcy), and glutathione (GSH). This tutorial review focuses on various thiol detection methods based on luminescent or colorimetric spectrophotometry published during the period 2010-2012. The discussion covers a diversity of sensing mechanisms such as Michael addition, cyclization with aldehydes, conjugate addition-cyclization, cleavage of sulfonamide and sulfonate esters, thiol-halogen nucleophilic substitution, disulfide exchange, native chemical ligation (NCL), metal complex-displace coordination, and nanomaterial-related and DNA-based chemosensors. PMID:23689799

Jung, Hyo Sung; Chen, Xiaoqiang; Kim, Jong Seung; Yoon, Juyoung



Nucleic acid-coupled colorimetric analyte detectors  

US Patent & Trademark Office Database

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.



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


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



Colorimetric detection of Co2+ ion using silver nanoparticles with spherical, plate, and rod shapes.  


A highly sensitive colorimetric sensing platform for the selective trace analysis for Co(2+) ions is reported, based on glutathione (GSH)-modified silver nanoparticles (AgNP). The shape of metallic nanoparticles used in colorimetric detection, using the unique optical properties of plasmonic nanoparticles, is almost spherical. Therefore, in this work we attempted to investigate the selective detection of heavy metal ion (Co(2+)), with the shape of AgNPs (nanosphere, nanoplate, and nanorod). GSH-AgNP with spherical shape shows a high sensitivity for all of the metal ions (Ni(2+), Co(2+), Cd(2+), Pb(2+), and As(3+)) but poor selective recognition for target metal ions. Whereas, AgNPs solution containing rod-type GSH-AgNP has a special response to Co(2+), and its selective detection might be based on the cooperative effect of CTAB and GSH. Therefore, Co(2+) ion could be selectively recognized using rod-type GSH-AgNPs. PMID:23795556

Sung, Hwa Kyung; Oh, Seung Yeon; Park, Chulhwan; Kim, Younghun



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


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



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


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 461nm 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 52nM 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



Enzyme-based colorimetric detection of nucleic acids using peptide nucleic acid-immobilized microwell plates.  


The development of label-free or nonlabeling assays for nucleic acids is important in basic biological research and biomedical diagnosis. In this study, we have developed an enzyme-based colorimetric assay for nucleic acids, which combines the robustness of nonlabeling of DNA and RNA samples and the adequate sensitivity of enzymatic reactions. The core of this assay is the use of neutral peptide nucleic acid (PNA) as capture probe and the electrostatic adsorption of horseradish peroxidase (HRP) on hybridized, negatively charged nucleic acids to report the hybridization events, through HRP-catalyzed color reactions of 3,3',5,5'-tetramethylbenzidine and H(2)O(2). The proposed assay has been validated with fully complementary and single base-mismatched DNAs of different chain lengths. The proposed assay has also been validated with total RNA samples extracted from two human cancer cell lines (A 549 lung cancer cell and HeLa cell) for microRNA detection in real samples. Through extensive optimizations of HRP adsorption and nucleic acid hybridization conditions, detection limits of 0.1-0.2 nM for DNA (depending on chain length) and approximately 2 microg of total RNA have been achieved. Surface plasmon resonance spectroscopy has been used to elucidate the HRP adsorption and PNA-nucleic acid hybridizations through real-time measurements and to provide guidance for the development of the colorimetric assay. PMID:17708676

Su, Xiaodi; Teh, Huey Fang; Lieu, Xiaohui; Gao, Zhiqiang



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



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


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



Colorimetric detection and fingerprinting of bacteria by glass-supported lipid/polydiacetylene films.  


Glass-supported films of lipids and polydiacetylene were applied for visual detection and colorimetric fingerprinting of bacteria. The sensor films comprise polydiacetylene domains serving as the chromatic reporter interspersed within lipid monolayers that function as a biomimetic membrane platform. The detection schemes are based on either visible blue-red transitions or fluorescence transformations of polydiacetylene, induced by amphiphilic molecules secreted by proliferating bacteria. An important feature of the new film platform is the feasibility of either naked-eye detection of bacteria or color analysis using conventional scanners. Furthermore, we find that the degrees of bacterially induced color transformations depend both on the bacterial strains examined and the lipid compositions of the films. Accordingly, bacterial fingerprinting can be achieved through pattern recognition obtained by recording the chromatic transformations in an array of lipid/PDA films having different lipid components. PMID:17371063

Scindia, Yogesh; Silbert, Liron; Volinsky, Roman; Kolusheva, Sofiya; Jelinek, Raz



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



On-Chip Colorimetric Detection of Cu(2+) Ions via Density-Controlled Plasmonic Core-Satellites Nanoassembly.  


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



A Colorimetric Chemodosimeter for Pd(II): A Method for Detecting Residual Palladium in Cross-Coupling Reactions  

PubMed Central

A colorimetric chemodosimeter (SQ1) for the detection of trace palladium salts in cross-coupling reactions mediated by palladium is described. Decolorization of SQ1 is affected by nucleophilic attack of ethanethiol in basic DMSO solutions. Thiol addition is determined to have an equilibrium constant (Keq) of 2.9 × 106 M-1, with a large entropic and modest enthalpic driving force. This unusual result is attributed to solvent effects arising from a strong coordinative interaction between DMSO and the parent squaraine. Palladium detection is achieved through thiol scavenging from the SQ1-ethanethiol complex leading to a color “turn-on” of the parent squaraine. It was found that untreated samples obtained directly from Suzuki couplings showed no response to the assay. However, treatment of the samples with aqueous nitric acid generates a uniform Pd(NO3)2 species, which gives an appropriate response. “Naked-eye” detection of Pd(NO3)2 was estimated to be as low as 0.5 ppm in solution, and instrument-based detection was tested as low as 100 ppb. The average error over the working range of the assay was determined to be 7%.

Houk, Ronald J. T.; Wallace, Karl J.; Hewage, Himali S.; Anslyn, Eric V.



Silver nanoparticle based label-free colorimetric immunosensor for rapid detection of neurogenin 1.  


Neurogenin 1 (ngn1), with the functions of controlling the differentiation of neurons, determining specific neuronal subtype, and inhibiting glial differentiation, is quantitatively detected for the first time. By using specifically modified silver nanoparticles (AgNP) as the signaling element, a label-free, rapid and sensitive colorimetric immunoassay for the synthetic peptide fragment of ngn1 (amino acid sequence: AQDDEQERRRRRGRTR) is reported. The detection procedure is based on an anti-aggregation mechanism, by which ngn1 inhibits the aggregation of the probe in the presence of salt (NaClO(4)). The anti-ngn1 antibody conjugated AgNP (denoted as AgNP-Ab) is negatively charged, and mono-binding of the like-charged ngn1 to the probe will increase the surface charge density, hence enhancing the interparticular electrostatic repulsion. Along with the increase of ngn1 concentration, the color of the solution varies from red to yellow, thereby developing a feasible approach for the detection of ngn1. Using a UV/vis spectrophotometer, this assay exhibits a linear response range of two orders of magnitude, from 50 to 800 ng mL(-1), and a detection limit of 30 ng mL(-1). On the basis of these qualities, the antibody-conjugated AgNP may become a useful tool for point-of-care diagnosis of ngn1 and such a method offers a new insight on the detection of the analogous antigen fragment as well. PMID:22114758

Yuan, Yue; Zhang, Jia; Zhang, Hanchang; Yang, Xiurong



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


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

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



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.



Colorimetric detection of cholesterol with G-quadruplex-based DNAzymes and ABTS2-.  


A novel colorimetric method for detection of cholesterol was developed with hemin-G-quadruplex DNAzyme by transducing oxidation of cholesterol into the color change of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS(2-)). Oligonucleotide 5'-GTGGGTAGGGCGGGTTGG-3' (Oligo-1) formed G-quadruplex structure in the presence of K(+), it acted as a horseradish peroxidase (HRP) mimicking DNAzyme when binding hemin and catalyzed the oxidation of colorless ABTS(2-) to green ABTS(·-) by H(2)O(2), which was produced by the reaction of cholesterol and oxygen that catalyzed by cholesterol oxidase. Therefore, the oxidation of cholesterol could be transduced into the color change of ABTS(2-) by combining these two reactions. Under the optimum conditions, the absorbance was proportional to the concentration of cholesterol over the range of 1.0-30 ?M, with a linear regression equation of A=0.362+0.0256C (C: ?M, R=0.998) and a detection limit of 0.10 ?M (3?/slope). Moreover, the practicability of the assay in the detection of cholesterol in human serum was studied as well. PMID:22483213

Li, Ruimin; Xiong, Cen; Xiao, Zhiyou; Ling, Liansheng



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.



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.



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


Based on the selective interaction between Hg(2+) ions and cyanuric acid (CA) and the anti-aggregation of CA stabilized gold nanoparticles (CA-Au NPs), a simple colorimetric method was developed for detecting Hg(2+) ions. In a medium of pH 7.4 tris-HCl buffer containing 8×10(-3) M NaCl, the CA-Au NPs solution was red, which was due to CA adsorbed onto the surface of Au NPs, stabilizing Au NPs against aggregation. When CA-Hg(II)-CA complex was formed in the presence of Hg(2+), the stability of CA-Au NPs reduced, and then aggregation of Au NPs occurred. Consequently, the color of the solution changed from red to blue and could easily be measured with a common spectrophotometer. The aggregation of Au NPs was also validated using transmission electron microscopy (TEM). The controlled experiment showed that other ions including Ba(2+), Ca(2+), Zn(2+), Cd(2+), Co(2+), Mn(2+), Cu(2+), Mg(2+), and Ni(2+) ions did not induce any distinct spectral changes, which constituted a Hg(2+)-selective sensor. A dynamic range of 1.6-16×10(-6)M Hg(2+) ions was observed at the optimized reaction condition. This method provides a potentially useful tool for Hg(2+) detection. PMID:22892371

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



Colorimetric detection of ractopamine and salbutamol using gold nanoparticles functionalized with melamine as a probe.  


A highly selective and sensitive method is developed for colorimetric detection of ractopamine and salbutamol using gold nanoparticles (AuNPs) functionalized with melamine (MA), respectively. The presence of these ?-agonists induces the aggregation of gold nanoparticles through hydrogen-bonding interaction that was accompanied by a distinct change in color and optical properties, which could be monitored by a UV-vis spectrophotometer or even naked eyes. This process caused a significant decrease in the absorbance ratio (A670 nm/A520 nm) of melamine-gold nanoparticles (MA-AuNPs), and the color changed from wine red to blue. The systems exhibited a wide liner range, from 1×10(-10)M to 5×10(-7)mol/L with a correlation coefficient of 0.995 for ractopamine, and 1×10(-10)M to 1×10(-5)mol/L with a correlation coefficient of 0.996 for salbutamol, with measuring the absorbance ratio (A670 nm/A520 nm). The detection limit of these ?-agonists is as low as 1×10(-11)mol/L. Particularly, the developed method has been applied to the analysis of real swine feed samples and has achieved satisfactory results. PMID:23708531

Zhou, Ying; Wang, Peilong; Su, Xiaoou; Zhao, Hong; He, Yujian



Colorimetric detection of DNA damage by using hemin-graphene nanocomposites.  


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. PMID:23376271

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



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


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

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



Direct detection of WIMPs  

NASA Astrophysics Data System (ADS)

To test the hypothesis according to which Weakly Interacting Massive Particles are a major constituent of Dark Matter, direct detection experiments aim at detecting the spectrum of nuclear recoils induced by WIMPs from the Milky Way halo within a target material. While the detection concept is already more than 20 years old, recent experimental developments have allowed fast progress, which up to now have lead to constrain electroweak theories beyond the standard model in a complementary way to collider experiments.

Armengaud, Eric



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



A new perylene diimide-based colorimetric and fluorescent sensor for selective detection of Cu 2+ cation  

Microsoft Academic Search

A new perylene diimide (PDI) ligand (1) functionalized with a dipicolylethylenediamine (DPEN) moiety was synthesized and first\\u000a used as a colorimetric and fluorometric dual-channel sensor to specifically detect the presence of Cu2+ over a wide range of other cations. The solution of 1 (10 ?mol\\/L) upon addition of Cu2+ displayed distinguishing pink color compared with other cations including K+, Ni2+,

LiWei Yan; Li Yang; JingBo Lan; JingSong You



Colorimetric hypochlorite detection using an azobenzene acid in pure aqueous solutions and real application in tap water  

Microsoft Academic Search

Colorimetric azobenzene based chemosensor 1 was designed for the detection of hypochlorite by fully utilizing the oxidation property of hypochlorite and different coordinating properties of Cu+ and Cu2+ in pure aqueous solutions. In the presence of cuprous ions, the red solution of chemosensor 1 changed to yellow, upon the addition of hypochlorite. Other anions, including H2PO42?, H2PO4?, SO42?, Cl?, ClO4?,

Xiaoding Lou; Yi Zhang; Jingui Qin; Zhen Li


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.



A gold nanoparticles-based colorimetric assay for alkaline phosphatase detection with tunable dynamic range.  


In this report, a simple and label-free colorimetric assay was developed for detecting alkaline phosphatase (ALP). Based on the conjugated gold nanoparticle/adenosine triphosphate (AuNP/ATP) sensing system, this assay is highly sensitive and selective. In this system, ATP induces the aggregation of cetyltrimethylammonium bromide (CTAB)-capped AuNPs and ALP stimulates the disaggregation of AuNPs by converting ATP into adenosine through an enzymatic dephosphorylation reaction. Hence, the presence of ALP can be visually observed (gray-to-red color change) and monitored by the shift of the surface plasmon resonance (SPR) absorption band of AuNPs. Furthermore, the dynamic range of the method can be varied by addition of different metal ions (e.g. 100-600unit/L to 5.0-100unit/L and 0.2-20unit/L in the presence of Ca(2+) and Pb(2+), respectively). The feasibility of this sensitive and specific assay with a tunable dynamic range was demonstrated to be consistent even in human serum samples. PMID:23356994

Li, Chun Mei; Zhen, Shu Jun; Wang, Jian; Li, Yuan Fang; Huang, Cheng Zhi



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.



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

SciTech Connect

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)



Low cost, disposable colorimetric sensor for quantitative detection of ammonia gas  

NASA Astrophysics Data System (ADS)

The development of a simple, fast, disposable and low cost method for sensing and differentiating a wide range of concentration of toxic ammonia vapor by using colorimetric sensor is reported. A large dynamic range from 10 ppm to 1,00,000 ppm is successfully classified at ambient temperature with reproducible results. The CSA strip is consists of the dots of chemo-responsive materials, which are environmental friendly and react specifically with ammonia at different thresholds. The pattern of color change of colorimetric sensor array is unique for reported concentration range of ammonia gas.

Srivastava, Ruchi; Verma, Abhishek; Jain, V. K.



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


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

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



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


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



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

NASA Astrophysics Data System (ADS)

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

Gao, Yang; Ma, Wenzhong



A Colorimetric Sensor Array for the Detection of the Date-Rape Drug ?-Hydroxybutyric Acid (GHB): A Supramolecular Approach.  


?-Hydroxybutyric acid (GHB), a colourless, odourless and tasteless chemical, has become one of the most dangerous illicit drugs of abuse today. At low doses, this drug is a central nervous system depressant that reduces anxiety and produces euphoria and relaxation, sedating the recipient. There is an urgent need for simple, easy-to-use sensors for GHB in solution. Here, we present a colorimetric sensor array based on supramolecular host-guest complexes of fluorescent dyes with organic capsules (cucurbiturils) for the detection of GHB. PMID:20309968

Baumes, Laurent A; Buaki Sogo, Mireia; Montes-Navajas, Pedro; Corma, Avelino; Garcia, Hermenegildo



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


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 Hg(2+), Cu(2+), Pb(2+), As(3+), Ca(2+), Al(3+), etc) and anions (such as NO(2)(-), CN(-), PF(6)(-), 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. PMID:21359318

Liu, Dingbin; Wang, Zhuo; Jiang, Xingyu



Use of colorimetric culture methods for detection of Mycobacterium tuberculosis complex isolates from sputum samples in resource-limited settings.  


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

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



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


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



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.  


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 30min by naked-eyes observation, and lower concentration of iodide down to 8.8nM 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



Development of a RT-PCR test coupled with a microplate colorimetric assay for the detection of a swine Arterivirus (PRRSV) in boar semen  

Microsoft Academic Search

Transmission of porcine reproductive and respiratory syndrome virus (PRRSV) through boar semen has been demonstrated, stressing the need for a reliable semen PRRSV detection test. A diagnostic assay was developed based on amplification of the PRRSV RNA by reverse transcription and polymerase chain reaction (RT-PCR) followed by detection of the amplification products by hybridization and colorimetric assay in microwell plates.

O. Legeay; S. Bounaix; M. Denis; C. Arnauld; E. Hutet; R. Cariolet; E. Albina; A. Jestin



A colorimetric method for detection of K-ras codon 12 point mutations in DNA extracted from tissue and peripheral blood in pancreatic disorders.  


Molecular-based methods to monitor point mutations require special and expensive equipment unavailable in most hospitals. Colorimetric-based analysis is an ideal platform for K-ras codon 12 gene point mutations because it uses commonly found hospital equipment. The colorimetric assay is sensitive and specific, detecting mutated DNA levels as low as 1% in a wild-type background. Paired genomic DNA extracts of fixed tissue and cellular fractions of peripheral blood are more sensitive and accurate than unpaired samplings. This approach has the potential to improve K-ras point mutation scans as well as to detect micrometastases in circulating tumor cells. PMID:20383741

Ollar, Robert A; Cooperman, Avram M; Wayne, Michael E; Barrecchia, James F; Sonpal, Niket; Duddempudi, Sushil; Kasmin, Franklin E



A schiff-based colorimetric fluorescent sensor with the potential for detection of fluoride ions.  


A simple Schiff-based colorimetric fluorescent receptor 1 was prepared. It exhibits a "turn-on-type" mode with high sensitivity in the presence of F(-). The change in color is very easily observed by the naked eye in the presence of F(-), whereas other anions do not induce such a change. Job plot indicated a 1:2 complexation stoichiometry between receptor 1 and F(-). The association constant for 1-F(-) in CH3CN was determined as 1.32*10(5) M(-2) by a Hill plot. PMID:23888325

Huang, Cheng-Yin; Wan, Chin-Feng; Chir, Jiun-Ly; Wu, An-Tai



A colorimetric confirmation method for DNA amplification in PCR and its application to the detection of Giardia lamblia cysts.  


A simple and quick colorimetric method for confirming DNA amplification in polymerase chain reactions (PCR) is described and has been applied to the amplification of Giardia lamblia DNA. This method detects the release of pyrophosphate based on the competition between 1, 10-phenanthroline and pyrophosphate complexing with ferrous ion. When 1, 10-phenanthroline complexed with Fe2+ is added to the finished PCR solution, depending on whether or not the DNA was amplified, the mixture is, respectively, either bleached or red. The color changed optimally for 20-30 min at 60-80 degrees C, and the result could be determined by detecting an absorbancy change at 510 nm or a color change discernible to the naked eye. The extent of change in absorbance was proportional to the amount of pyrophosphate produced. PMID:14626418

Lee, Kisay; Kim, Kyungju



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


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



A FRET ratiometric fluorescence sensing system for mercury detection and intracellular colorimetric imaging in live Hela cells.  


The detection of mercury in biological systems and its imaging is of highly importance. In this work, a ratiometric fluorescence sensor is developed based on fluorescence resonance energy transfer (FRET) with N-acetyl-L-cysteine functionalized quantum dots (NAC-QDs) as donor and Rhodamine 6G derivative-mercury conjugate (R6G-D-Hg) as acceptor. Mercury annihilates the fluorescence of NAC-QDs at 508 nm and meanwhile interacts with R6G derivative to form a fluorescent conjugate giving rise to emission at 554 nm. Resonance energy transfer from NAC-QDs to R6G-D-Hg is triggered by mercury resulting in concentration-dependent variation of fluorescence ratio F508/F554. A linear calibration of F508/F554 versus mercury concentration is obtained within 5-250 ?g L(-1), along with a detection limit of 0.75 ?g L(-1) and a RSD of 3.2% (175 ?g L(-1)). The sensor generates colorimetric images for mercury within 0-250 ?g L(-1), facilitating visual detection of mercury with a distinguishing ability of 50 ?g L(-1). This feature is further demonstrated by colorimetric imaging of intracellular mercury. On the other hand, the NAC-QDs/R6G-D FRET sensing system is characterized by a combination of high sensitivity and selectivity. The present study provides an approach for further development of ratiometric sensors dedicated to selective in vitro or in vivo sensing some species of biologically interest. PMID:23811485

Hu, Bo; Hu, Lin-Lin; Chen, Ming-Li; Wang, Jian-Hua



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


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



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


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

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



Fe3O4 magnetic nanoparticle peroxidase mimetic-based colorimetric assay for the rapid detection of organophosphorus pesticide and nerve agent.  


Rapid and sensitive detection methods are in urgent demand for the screening of extensively used organophosphorus pesticides and highly toxic nerve agents for their neurotoxicity. In this study, we developed a novel Fe(3)O(4) magnetic nanoparticle (MNP) peroxidase mimetic-based colorimetric method for the rapid detection of organophosphorus pesticides and nerve agents. The detection assay is composed of MNPs, acetylcholinesterase (AChE), and choline oxidase (CHO). The enzymes AChE and CHO catalyze the formation of H(2)O(2) in the presence of acetylcholine, which then activates MNPs to catalyze the oxidation of colorimetric substrates to produce a color reaction. After incubation with the organophosphorus neurotoxins, the enzymatic activity of AChE was inhibited and produced less H(2)O(2), resulting in a decreased catalytic oxidation of colorimetric substrates over MNP peroxidase mimetics, accompanied by a drop in color intensity. Three organophosphorus compounds were tested on the assay: acephate and methyl-paraoxon as representative organophosphorus pesticides and the nerve agent Sarin. The novel assay displayed substantial color change after incubation in organophosphorus neurotoxins in a concentration-dependent manner. As low as 1 nM Sarin, 10 nM methyl-paraoxon, and 5 ?M acephate are easily detected by the novel assay. In conclusion, by employing the peroxidase-mimicking activity of MNPs, the developed colorimetric assay has the potential of becoming a screening tool for the rapid and sensitive assessment of the neurotoxicity of an overwhelming number of organophosphate compounds. PMID:23153113

Liang, Minmin; Fan, Kelong; Pan, Yong; Jiang, Hui; Wang, Fei; Yang, Dongling; Lu, Di; Feng, Jing; Zhao, Jianjun; Yang, Liu; Yan, Xiyun



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



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


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



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

NASA Astrophysics Data System (ADS)

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).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). Electronic supplementary information (ESI) available: Experimental section, structure and MALDI-TOF spectrum of MMP-7, TEM images, digestion scheme of peptide, photos of peptide functionalized gold nanoparticles before and after incubation with MMP-7. See DOI: 10.1039/c3nr03006g

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



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



Colorimetric detection of DNA sequences using an organic solvent to induce the aggregation of label-free gold nanoparticles.  


A novel assay based on a solvent for inducing the aggregation of AuNPs colloid was proposed to discriminate ssDNA from dsDNA. Eleven organic solvents with different polarity were investigated, and it was found that DMSO was possible to aggregate AuNPs at the amount of only 0.4 microL in a 50-microL detection system. Further research showed that 0.8 microL of DMSO could discriminate the ssDNA from dsDNA. Colorimetric detection with various conditions, including the ratio of the target to the probe, and the concentration of AuNPs and DNA, was investigated. The proposed method was successfully used for SNP typing, and unambiguous discrimination of a wild type from a mutant was obtained for the templates with the mismatched base at the 5'-end or in the middle of the target sequence. As no requirement of gold modification and detection instrument, we believe that this method will be much low in the cost for DNA detection. PMID:23862411

Jia, Huning; Cao, Xiaomei; Fu, Cong; Wang, Jianping; Chen, Zhiyao; Zou, Bingjie; Jin, Li; Yan, Zhengyu; Zhou, Guohua



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

Microsoft Academic Search

The goal of this study was to develop a field diagnosis system based on isothermal reverse transcription-loop-mediated amplification (RT-LAMP) for shrimp Taura syndrome virus (TSV), placing emphasis on specific and simple detection of the LAMP amplicons. After a single-tube RT-LAMP reaction for TSV was established, colorimetric dot–blot hybridization (DBH) was adopted to detect signals only from the target-derived amplicons. The

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



Directional recoil rates for WIMP direct detection  

SciTech Connect

New techniques for the laboratory direct detection of dark matter weakly interacting massive particles (WIMPs) are sensitive to the recoil direction of the struck nuclei. We compute and compare the directional recoil rates dR/dcos{theta} (where {theta} is the angle measured from a reference direction in the sky) for several WIMP velocity distributions including the standard dark halo and anisotropic models such as Sikivie's late-infall halo model and logarithmic-ellipsoidal models. Since some detectors may be unable to distinguish the beginning of the recoil track from its end (lack of head-tail discrimination), we introduce a folded directional recoil rate dR/d|cos{theta}|, where |cos{theta}| does not distinguish the head from the tail of the track. We compute the CS{sub 2} and CF{sub 4} exposures required to distinguish a signal from an isotropic background noise, and find that dR/d|cos{theta}| is effective for the standard dark halo and some but not all anisotropic models.

Alenazi, Moqbil S.; Gondolo, Paolo [Department of Physics, University of Utah, 115 S 1400 E Rm 201, Salt Lake City, Utah 84112-0830 (United States)



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

SciTech Connect

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

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



p-Dimethylaminocinnamaldehyde Derivatization for Colorimetric Detection and HPLC-UV/Vis-MS/MS Identification of Indoles  

PubMed Central

Cytochrome P450 2A13 is a lung specific enzyme known to activate the potent tobacco procarcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) into two carcinogenic metabolites. CYP2A13 has been crystallized and X-ray diffraction experiments illuminated the structure of this enzyme, but with an unknown ligand present in the enzyme active site. This unknown ligand was suspected to be indole but a selective method had to be developed to differentiate among indole and its metabolites in the protein sample. We successfully modified a microbiological colorimetric assay to spectrophotometrically differentiate between indole and a number of possible indole metabolites in nanomolar concentrations by derivatization with p-dimethylaminocinnamaldehyde (DMACA). Further differentiation of indoles was made by mass spectrometry (HPLC-UV/Vis-MS/MS) utilizing the chromophore generated in the DMACA conjugation as a UV signature for HPLC detection. The ligand in the crystallized protein was identified as unsubstituted indole, which facilitated refinement of two alternate conformations in the CYP2A13 crystal structure active site.

Porubsky, Patrick R.; Scott, Emily E.; Williams, Todd D.



A novel heterogeneous colorimetric and spectrophotometric chemosensor for detection and adsorption of Hg0 and Hg2+.  


Functionalized mesoporous silica with an immobilized azobenzene-coupled receptor 1 (FMS-1) as heterogeneous "naked-eye" colorimetric and spectrophotometric chemosensor was prepared by sol-gel reaction. The optical sensing ability of FMS-1 was studied by addition of metal ions such as K+, Ca2+, Sr2+, Co2+, Cd2+, Pb2+, Zn2+, Fe3+, Cu2+ and Hg2+ in aqueous solution. Interestingly, upon the addition of Hg2+ in aqueous suspension, FMS-1 resulted in a color change from maroon to red within 10 s. On the other hand, no significant color changes were observed with the other metal ions. These findings confirm that FMS-1 can be useful as a chemosensor for selective detection of Hg2+ over a range of metal ions. Furthermore, the adsorption ability of the FMS-1 was also estimated by measuring the amount of Hg2+ and Hg0 adsorbed on the FMS-1, resulting in 95% for Hg2+ and 75% for Hg0, respectively, suggesting that the FMS-1 is potentially useful as the adsorbent for separation of Hg0 and Hg2+ in chromatography. PMID:21125828

Kim, Eunjeong; Cho, Namjun; Vittal, Jagadese J; Lee, Shim Sung; Han, Won Seok; Jung, Jong Hwa



Systematic comparisons of various spectrophotometric and colorimetric methods to measure concentrations of protein, peptide and amino acid: detectable limits, linear dynamic ranges, interferences, practicality and unit costs.  


There is limited and inconclusive information regarding detectable limits and linear dynamic ranges of various quantitative protein assays. We thus performed systematic comparisons of seven commonly used methods, including direct spectrophotometric quantitation at ?205 and ?280 nm (A205 and A280, respectively), bicinchoninic acid (BCA), Biuret, Bradford, Lowry and Ninhydrin methods. Purified BSA, porcine kidney extract, tryptic digested peptides derived from purified BSA, and glycine, were used as representative purified protein, complex protein mixture, peptide and amino acid, respectively. Bradford method was the most sensitive assay (LOD=0.006 mg/ml) and had the widest range of detectability (LOD-UOD=0.006-100mg/ml) for purified protein and complex protein mixture. For peptide, A205, A280, Lowry and Ninhydrin methods had a comparable LOD (0.006 mg/ml), but Ninhydrin method had the widest detectability range (LOD-UOD=0.006-100mg/ml). For amino acid, A205 and Ninhydrin methods had a comparable LOD (0.006 mg/ml), but A205 had a wider detectability range (LOD-UOD=0.006-6.250 mg/ml). Biuret method offered the widest linear dynamic range for purified protein and complex protein mixture (0.391-100mg/ml), A280 offered the widest linear dynamic range for peptide (0.024-6.250 mg/ml), and Ninhydrin method offered the widest linear dynamic range for amino acid (0.024-0.195 mg/ml). Both Laemmli's and 2-D lysis buffers had dramatic interfering effects on all assays. Concerning the practicality and unit costs, A205 and A280 were the most favorable. Among the colorimetric methods, Bradford method consumed the least amount of samples and shortest analytical time with the lowest unit cost. These are the most extensive comparative data of commonly used quantitative protein assays that will be useful for selecting the most suitable method for each study. PMID:22939137

Chutipongtanate, Somchai; Watcharatanyatip, Kamolwan; Homvises, Teerada; Jaturongkakul, Kewalee; Thongboonkerd, Visith




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...


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



Detection of subnanomolar melamine based on electrochemical accumulation coupled with enzyme colorimetric assay.  


Based on the synergetic effect of the electrochemical accumulation process and the signal amplification of enzymes, a new sensitive method has been developed for the detection of subnanomolar melamine. There are two steps involved in the sensor construction process: (1) accumulation of melamine on an electrode by cyclic voltammetric method and (2) chemical coupling of horseradish peroxidase (HRP) with the accumulated melamine through the linkage of glutaraldehyde. The coupled HRP catalyzes the oxidation of guaiacol to generate an amber-colored product. Quantitative analysis of melamine is performed by measuring the absorption intensities of the colored product. Under the optimal conditions, the method showed a wide linearity in the concentration range from 1.0 × 10(-11) to 1.0 × 10(-8) M for melamine detection. Moreover, it has been successfully applied to detect melamine in different infant formula powders and fish feed samples. PMID:23373873

Xu, Qin; Wei, Huan Ping; Du, Shi; Li, Hong Bo; Ji, Zhen Ping; Hu, Xiao Ya



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


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



Colorimetric detection of DNA sequences based on electrostatic interactions with unmodified gold nanoparticles  

PubMed Central

We find that single- and double-stranded oligonucleotides have different propensities to adsorb on gold nanoparticles in colloidal solution. We use this observation to design a hybridization assay based on color changes associated with gold aggregation. Because the underlying adsorption mechanism is electrostatic, no covalent functionalization of the gold, the probe, or the target DNA is required. Hybridization conditions can be optimized because it is completely separated from the detection step. The assay is complete within 5 min, and <100 femtomoles of target produces color changes observable without instrumentation. Single-base-pair mismatches are easily detected.

Li, Huixiang; Rothberg, Lewis




EPA Science Inventory

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


A fluorescence-based colorimetric droplet platform for biosensor application to the detection of ?-fetoprotein.  


Droplet methods have been successfully applied in DNA hybridization analysis and protein-protein interaction. Existing assay methods implemented in droplet platforms are severely limited by expensive and high-maintenance equipment. As a convenient detection method, colorimetry provides a new path for microscale assay since it can enhance assay efficiency and simplify the detection procedure. Here, a microscale immunoassay for ?-fetoprotein (AFP) was developed for the first time by the incorporation of colorimetry and droplet platform. Ru(bpy)(2)(mcbpy-O-Su-ester)(PF(6))(2) complex (Ru) was coupled with the monoclonal antibody (Ab) of AFP to form a stable red Ru-Ab complex both as a quencher for green CdTe quantum dots (QDs) and as a capture probe for AFP. In the absence of AFP, the mixed droplet showed a red color. With the increase of AFP concentration, the color change of the droplet was from red to green as a result of the competition of AFP with QDs for Ru-Ab. The biosensor exhibited not only good sensitivity and specificity for AFP with a detection limit of 0.06 ng ml(-1), but also satisfactory performance in diluted human sera with a detection limit of 0.4 ng ml(-1). Notably, a visual droplet platform for screening cancer biomarkers by the naked eye based on this principle is anticipated. PMID:23059448

Xiang, Xia; Chen, Lu; Zhang, Cuiling; Luo, Ming; Ji, Xinghu; He, Zhike



Direct Detection of Dark Matter  

NASA Astrophysics Data System (ADS)

The principles and some important features of the direct detection of dark matter are introduced, and recent experimental progress is reported. In particular, the XMASS experiment, which is a large-scale dark-matter experiment in Japan, is explained in detail.

Moriyama, S.



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

Microsoft Academic Search

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

G. N. El-Sayed; C. M. Ignoffo; T. D. Leathers; S. C. Gupta



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


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

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



Gold nanoflowers based colorimetric detection of Hg(2+) and Pb(2+) ions.  


An optical detection method based on the interaction of gold nanoflowers with Hg(2+) and Pb(2+) has been described. After interaction, gold nanoflowers change the color from violet to wine red. The nanoflowers are capable of determining Hg(2+) and Pb(2+) 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 Hg(2+) and Pb(2+) 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 Hg(2+) and Pb(2+) 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 Hg(2+) and Pb(2+) 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 3months without observing any major deviation. PMID:23933548

Nalawade, Pradnya; Kapoor, Sudhir



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))



New Aminobenzopyranoxanthene-Based Colorimetric Sensor for Copper(II) Ions with Dual-Color Signal Detection System.  


One molecule, three faces: A new aminobenzopyranoxanthene (ABPX)-based colorimetric sensor allows determination of changes in Cu(2+) concentration by spectrophotometry and the naked eye. This quantitative, colorful, and simple method takes advantage of the unique protolytic reaction of ABPX in response to Cu(2+) . PMID:23843315

Shirasaki, Yoshinao; Kamino, Shinichiro; Tanioka, Masaru; Watanabe, Keiko; Takeuchi, Yasuo; Komeda, Seiji; Enomoto, Shuichi



Colorimetric biosensing using smart materials.  


In recent years, colorimetric biosensing has attracted much attention because of its low cost, simplicity, and practicality. Since color changes can be read out by the naked eye, colorimetric biosensing does not require expensive or sophisticated instrumentation and may be applied to field analysis and point-of-care diagnosis. For transformation of the detection events into color changes, a number of smart materials have been developed, including gold nanoparticles, magnetic nanoparticles, cerium oxide nanoparticles, carbon nanotubes, graphene oxide, and conjugated polymers. Here, we focus on recent developments in colorimetric biosensing using these smart materials. Along with introducing the mechanisms of color changes based on different smart materials, we concentrate on the design of biosensing assays and their potential applications in biomedical diagnosis and environmental monitoring. PMID:21800383

Song, Yujun; Wei, Weili; Qu, Xiaogang



Rapid detection of multidrug-resistant Mycobacterium tuberculosis in Cotonou (Benin) using two low-cost colorimetric methods: resazurin and nitrate reductase assays.  


We have evaluated two simple, rapid and low-cost colorimetric methods for the detection of multidrug-resistant Mycobacterium tuberculosis. A total of 151 M. tuberculosis strains were tested for resistance to rifampicin (RMP) and isoniazid by resazurin microplate assay (REMA) and nitrate reductase assay (NRA) in comparison with the conventional proportion method (PM) on Löwenstein-Jensen medium. A complete agreement was found between NRA and PM, while one false RMP-susceptible result was found by REMA. REMA and NRA tests are rapid and inexpensive, and could be good alternatives to the conventional PM in low-resource countries. PMID:18628506

Affolabi, Dissou; Sanoussi, N'dira; Odoun, Mathieu; Martin, Anandi; Koukpemedji, Louis; Palomino, Juan Carlos; Kestens, Luc; Anagonou, Séverin; Portaels, Françoise



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.



Direct detection polarimetric radiometer (DDPR)  

NASA Astrophysics Data System (ADS)

Polarimetric signatures of terrain features and man-made objects have been measured using unique Direct Detection Polarimetric Radiometers (DDPR). The DDPRs are lightweight inexpensive systems operating at 35 and 94 GHz. Each system consists of a single antenna, amplifier, and a truncated cylindrical waveguide that directly measures Q, U, and V. The highly portable DDPRs are ideal for obtaining the Stokes vectors needed to study the physical characteristics of natural and man-made features. Field evaluations using the DDPR systems include measurements from an airborne platform over different terrain features and water, and ground based measurements of the polarimetric signature of grass, asphalt, buildings, and concealed munitions. The DDPR can function as a bistatic system by using an active source of polarization. Using this configuration and a soil chamber, we have investigated the effect of soil type and soil moisture on linear and circular polarization. This report will describe the DDPR and present the analysis of the airborne and ground based measurements, including the effects of soil type and soil moisture on sources of linear and circular polarization.

Koenig, G.; Koh, G.; Ryerson, C.



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



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


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

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



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


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. PMID:21625041

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



A protocol for stripping and reprobing of Western blots originally developed with colorimetric substrate TMB.  


Western blotting is a widely used analytical technique for detection of specific protein(s) in a given sample of tissue/cell homogenate or extract. Both chemiluminescence (CL) and colorimetric detections can be used for imaging Western blots. Colorimetric substrates offer background free, sensitive, and clean imaging results directly on the blotted membrane and provides more accurate profile with respect to prestained marker. However, blots stained with colorimetric substrates cannot be reused since no stripping protocols have been reported for such blots, thus limiting their reuse for detection of another protein. In the present study, for the first time, we report a novel method of stripping Western blots developed with the colorimetric substrate TMB for detection of a low-abundant protein and reprobing of these blots after stripping for detection of a more abundant protein through CL procedure. The stripping procedure utilizes a stripping buffer consisting of ?-mercaptoethanol, SDS, and Tris-HCl and a washing buffer consisting of PBS added with 0.1% Tween-20 involves a series of steps and facilitates accurate detection of the second protein (i.e., more abundant protein) in the stripped blot through CL. The protocol is reproducible and facilitates saving of precious clinical samples, in addition to saving cost and time as compared to the existing procedures. PMID:23002003

Kar, Parmita; Agnihotri, Saurabh Kumar; Sharma, Archana; Sachan, Rekha; Lal Bhatt, Madan; Sachdev, Monika



Doped colorimetric assay liposomes  


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)



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



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


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



Direct Detection of Electron Backscatter Diffraction Patterns  

NASA Astrophysics Data System (ADS)

We report the first use of direct detection for recording electron backscatter diffraction patterns. We demonstrate the following advantages of direct detection: the resolution in the patterns is such that higher order features are visible; patterns can be recorded at beam energies below those at which conventional detectors usefully operate; high precision in cross-correlation based pattern shift measurements needed for high resolution electron backscatter diffraction strain mapping can be obtained. We also show that the physics underlying direct detection is sufficiently well understood at low primary electron energies such that simulated patterns can be generated to verify our experimental data.

Wilkinson, Angus J.; Moldovan, Grigore; Britton, T. Benjamin; Bewick, Angus; Clough, Robert; Kirkland, Angus I.



Direct detection of electron backscatter diffraction patterns.  


We report the first use of direct detection for recording electron backscatter diffraction patterns. We demonstrate the following advantages of direct detection: the resolution in the patterns is such that higher order features are visible; patterns can be recorded at beam energies below those at which conventional detectors usefully operate; high precision in cross-correlation based pattern shift measurements needed for high resolution electron backscatter diffraction strain mapping can be obtained. We also show that the physics underlying direct detection is sufficiently well understood at low primary electron energies such that simulated patterns can be generated to verify our experimental data. PMID:23971587

Wilkinson, Angus J; Moldovan, Grigore; Britton, T Benjamin; Bewick, Angus; Clough, Robert; Kirkland, Angus I



Ultra-sensitive non-aggregation colorimetric sensor for detection of iron based on the signal amplification effect of Fe(3+) catalyzing H2O2 oxidize gold nanorods.  


Fe(3+) can catalyze H2O2 to oxidize along on the longitudinal axis of gold nanorods (AuNRs), which caused the aspect ratio of AuNRs to decrease, longitudinal plasmon absorption band (LPAB) of AuNRs to blueshift (??) and the color of the solution to change obviously. Thus, a rapid response and highly sensitive non-aggregation colorimetric sensor for the determination of Fe(3+) has been developed based on the signal amplification effect of catalyzing H2O2 to oxidize AuNRs. This simple and selective sensor with a wide linear range of 0.20-30.00?M has been utilized to detect Fe(3+) in blood samples, and the results consisted with those obtained by inductively coupled plasma-mass spectroscopy (ICP-MS). Simultaneously, the mechanism of colorimetric sensor for the detection of Fe(3+) was also discussed. PMID:24148393

Liu, Jia-Ming; Wang, Xin-Xing; Jiao, Li; Cui, Ma-Lin; Lin, Li-Ping; Zhang, Li-Hong; Jiang, Shu-Lian



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



Development of a PCR-based method coupled with a microplate colorimetric assay for the detection of Porcine Parvovirus and application to diagnosis in piglet tissues and human plasma  

Microsoft Academic Search

A new method for Porcine Parvovirus (PPV) diagnosis was developed. The method is based on polymerase chain reaction (PCR) amplification followed by hybridization and colorimetric detection of PCR products in microwell plates. A highly specific and sensitive amplification step was ensured by primers carefully selected in the VP2 structural gene and optimized PCR conditions. Uracyl-DNA-Glycosylase (UDG) in combination with dUTP

C. Arnauld; O. Legeay; Y. Laurian; R. Thiery; M. Denis; P. Blanchard; A. Jestin



Rapid and low-cost colorimetric method using 2,3,5-triphenyltetrazolium chloride for detection of multidrug-resistant Mycobacterium tuberculosis.  


A rapid and inexpensive method for the detection of drug resistance in Mycobacterium tuberculosis is essential for the effective control of tuberculosis. The aim of this study was to evaluate a colorimetric method using 2,3,5-triphenyltetrazolium chloride (TTC) for antibiotic susceptibility testing of M. tuberculosis isolates. Eleven multidrug-resistant (MDR) isolates of M. tuberculosis and 12 isolates which were susceptible to rifampicin (RIF) and isoniazid (INH) were used. The test was performed with a critical concentration of 0.2 microg ml(-1) for INH and 2.0 microg ml(-1) for RIF in 7H9GC broth with 0.625 microg TTC ml(-1). Each isolate was inoculated under these conditions and inspected daily for colour changes; the results were obtained after a mean of 4.9 days. The sensitivity and specificity of this method were 100 % and 92 %, respectively, for both antibiotics. Considering the speed, technical ease and cost-effectiveness of this method, the TTC assay is a good alternative method for drug susceptibility testing of M. tuberculosis isolates. PMID:17108268

Mohammadzadeh, Alireza; Farnia, Parisa; Ghazvini, Kiarash; Behdani, Mahdi; Rashed, Tahereh; Ghanaat, Javad



Median recoil direction as a WIMP directional detection signal  

SciTech Connect

Direct detection experiments have reached the sensitivity to detect dark matter weakly interacting massive particles (WIMPs). Demonstrating that a putative signal is due to WIMPs, and not backgrounds, is a major challenge, however. The direction dependence of the WIMP scattering rate provides a potential WIMP 'smoking gun'. If the WIMP distribution is predominantly smooth, the Galactic recoil distribution is peaked in the direction opposite to the direction of Solar motion. Previous studies have found that, for an ideal detector, of order 10 WIMP events would be sufficient to reject isotropy, and rule out an isotropic background. We examine how the median recoil direction could be used to confirm the WIMP origin of an anisotropic recoil signal. Specifically, we determine the number of events required to confirm the direction of solar motion as the median inverse recoil direction at 95% confidence. We find that for zero background 31 events are required, a factor of {approx}2 more than are required to simply reject isotropy. We also investigate the effect of a nonzero isotropic background. As the background rate is increased the number of events required increases, initially fairly gradually and then more rapidly, once the signal becomes subdominant. We also discuss the effect of features in the speed distribution at large speeds, as found in recent high resolution simulations, on the median recoil direction.

Green, Anne M. [School of Physics and Astronomy, University of Nottingham, University Park, Nottingham, NG7 2RD (United Kingdom); Morgan, Ben [Department of Physics, University of Warwick, Coventry, CV4 7AL (United Kingdom)



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.



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


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



Performance Evaluation of a Colorimetric Hydrazine Dosimeter.  

National Technical Information Service (NTIS)

A dosimeter for real-time, colorimetric detection of hydrazine in air has been developed. The passive badge consists of a dosimeter card containing a vanillin solution coated on a thin paper substrate. The active patch consists of a thick cellulose substr...

K. P. Brenner S. L. Rose-Pehrsson



Novel colorimetric sensor for oral malodour  

Microsoft Academic Search

Volatile sulphur compounds are the primary constituents of oral malodour. Quantitative tools for the detection of oral malodour are beneficial to evaluate the intensity of malodour, analyse its causes and monitor the effectiveness of customized treatments. We have developed an objective, cost effective, do-it-yourself colorimetric sensor for oral malodour quantification. The sensor consisted of a sensing solution, a gas sampling

Nethaji Alagirisamy; Sarita S. Hardas; Sujatha Jayaraman



Simultaneous nucleophilic-substituted and electrostatic interactions for thermal switching of spiropyran: a new approach for rapid and selective colorimetric detection of thiol-containing amino acids.  


Complementary electrostatic interaction between the zwitterionic merocyanine and dipolar molecules has emerged as a common strategy for reversibly structural conversion of spiropyrans. Herein, we report a concept-new approach for thermal switching of a spiropyran that is based on simultaneous nucleophilic-substitution reaction and electrostatic interaction. The nucleophilic-substitution at spiro-carbon atom of a spiropyran is promoted due to electron-deficient interaction induced by 6- and 8-nitro groups, which is responsible for the isomerization of the spiropyran by interacting with thiol-containing amino acids. Further, the electrostatic interaction between the zwitterionic merocyanine and the amino acids would accelerate the structural conversion. As proof-of-principle, we outline the route to glutathione (GSH)-induced ring-opening of 6,8-dinitro-1',3',3'-trimethylspiro [2H-1-benzopyran-2,2'-indoline] (1) and its application for rapid and sensitive colorimetric detection of GSH. In ethanol-water (1:99, v/v) solution at pH 8.0, the free 1 exhibited slight-yellow color, but the color changed clearly from slight-yellow to orange-yellow when GSH was introduced into the solution. Ring-opening rate of 1 upon accession of GSH in the dark is 0.45 s(-1), which is 4 orders of magnitude faster in comparison with the rate of the spontaneous thermal isomerization. The absorbance enhancement of 1 at 480 nm was in proportion to the GSH concentration of 2.5 × 10(-8)-5.0 × 10(-6) M with a detection limit of 1.0 × 10(-8) M. Furthermore, due to the specific chemical reaction between the probe and target, color change of 1 is highly selective for thiol-containing amino acids; interferences from other biologically active amino acids or anions are minimal. PMID:22545785

Li, Yinhui; Duan, Yu; Li, Jishan; Zheng, Jing; Yu, Huan; Yang, Ronghua



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


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

Halliwell, Jennifer; Gwenin, Christopher



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



Disentangling Dark Matter Dynamics with Directional Detection  

SciTech Connect

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

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



Disentangling dark matter dynamics with directional detection  

SciTech Connect

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

Lisanti, Mariangela; Wacker, Jay G. [Theory Group, SLAC, Menlo Park, California 94025 (United States)



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


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

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



Probing light WIMPs with directional detection experiments  

NASA Astrophysics Data System (ADS)

The CoGeNT and CRESST WIMP direct detection experiments have recently observed excesses of nuclear recoil events, while the DAMA/LIBRA experiment has a long-standing annual modulation signal. It has been suggested that these excesses may be due to light masses of m?˜5-10GeV, weakly interacting massive particles (WIMPs). The Earth’s motion with respect to the Galactic rest frame leads to a directional dependence in the WIMP scattering rate, providing a powerful signal of the Galactic origin of any recoil excess. We investigate whether direct detection experiments with directional sensitivity have the potential to observe this anisotropic scattering rate with the elastically scattering light WIMPs proposed to explain the observed excesses. We find that the number of recoils required to detect an anisotropic signal from light WIMPs at 5? significance varies from 7 to more than 190 over the set of target nuclei and energy thresholds expected for directional detectors. Smaller numbers arise from configurations where the detector is only sensitive to recoils from the highest-speed, and hence most anisotropic, WIMPs. However, the event rate above the threshold is very small in these cases, leading to the need for large experimental exposures to accumulate even a small number of events. To account for this sensitivity to the tail of the WIMP velocity distribution, whose shape is not well known, we consider two exemplar halo models spanning the range of possibilities. We also note that for an accurate calculation, the Earth’s orbital speed must be averaged over. We find that the exposures required to detect 10 GeV WIMPs at a WIMP-proton cross section of 10-4pb are of order 103kgday for a 20 keV energy threshold, within reach of planned directional detectors. Lower WIMP masses require higher exposures and/or lower energy thresholds for detection.

Morgan, Ben; Green, Anne M.



Control of metal nanoparticles aggregation and dispersion by PNA and PNA-DNA complexes, and its application for colorimetric DNA detection.  


We have demonstrated that mixed-base PNA oligomers are effective coagulants of citrate ion-coated gold and silver nanoparticles (AuNPs and AgNPs), and PNA-induced particle aggregation can be disrupted by hybridization of PNA with a specific DNA. Using particles' aggregation/dispersion as a measure, we have investigated how PNA and PNA-DNA complexes bind to AuNPs and AgNPs and modulate particles' stability differently relative to their DNA counterparts. We have made the following original discoveries: (1) mix-base PNA oligomers can induce immediate particle aggregation in a concentration- and chain-length-dependent manner; (2) PNA oligomers have a higher affinity to AuNPs and AgNPs than its ssDNA counterpart; (3) PNA-DNA complexes, although having a stable double helix structure similar to dsDNA, can effectively protect the particles from salt induced aggregation, and the protection effect of different nucleic acids are in the order of PNA-DNA complex > ssDNA > dsDNA; (4) all the characteristics are identical for AuNPs and AgNPs; and (5) AgNPs is more sensitive in response to destabilization effect and is proven a more sensitive platform for colorimetric assays. The control of particle aggregation and dispersion by PNA and PNA-DNA complexes has been used to detect a specific DNA sequence with single-base-mismatch resolution. zeta potential measurements have been conducted to reveal how distinct backbone properties of PNA and PNA-DNA complexes relative to their DNA counterparts contribute to the distinct binding characteristics. PMID:19708641

Su, Xiaodi; Kanjanawarut, Roejarek



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


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



Chitosan-capped silver nanoparticles as a highly selective colorimetric probe for visual detection of aromatic ortho-trihydroxy phenols.  


We reported a new application of silver nanoparticles (NPs) for the visual sensing of aromatic polyphenols, such as gallic acid, pyrogallol and tannic acid, which is based on the intensified plasmon absorbance signals and visual changes from yellow to orange due to hydrogen-bonding recognition and subsequent catalytic oxidation of the target phenols by chitosan-capped Ag NPs (Ch-Ag NPs). The Ch-Ag NPs are generated by the well-known reaction of AgNO3 with NaBH4 and stabilized with chitosan which is a polysaccharide biopolymer with excellent dispersive properties and stability in aqueous media. After optimizing some experimental conditions, a very simple and facile sensing system has been developed for the detection of gallic acid, pyrogallol and tannic acid in water samples. The proposed system promises high selectivity toward gallic acid, pyrogallol and tannic acid, and other phenolic compounds including p-aminobenzoic acid, pentachlorophenol, 2,4,6-trinitrophenol, 2,4-dinitrophenol, p-nitrophenol, 1-naphthol, ?-naphthol, p-aminophenol, catechol, hydroquinone, m-dihydroxybenzene, phloroglucin and phenol could not induce a color change even at 0.1 mM. The outstanding selectivity property of the proposed method for gallic acid, pyrogallol and tannic acid resulted from the Ch-Ag NPs-mediated reduction of Ag(+) by the target phenols. Also, a wide linear response range was obtained for the three targets. The linear response ranges for gallic acid, pyrogallol, and tannic acid were from 1 × 10(-5) to 1 × 10(-3) M, 1 × 10(-5) to 1 × 10(-2) M and 1 × 10(-6) to 1 × 10(-4) M with a respective detection limit (DL) of 1 × 10(-5), 1 × 10(-5), and 1 × 10(-6) M. The proposed method was successfully applied to detect target phenols in environmental water samples. Furthermore, because the color change from yellow to orange is observable by the naked eye, it is easy to realize visual detection of the target phenols without any instrumentation or complicated design. The experimental results reported here open up an innovative application of the catalytic reactivity of Ag NPs. PMID:23457709

Chen, Zhaohui; Zhang, Xiaodan; Cao, Haiyan; Huang, Yuming



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



[Determination of trace mercury in wastewater by a flow injection analysis composed of immobilized ionic liquid enrichment and colorimetric detection].  


Amberlite XAD-7 resin was modified by room temperature ionic liquid (1-hexyl-3-methylimidazolium hexafluorophosphate, [C6 mim]PF6) coating through a maceration method, gaining a new sort of hydrophobic adsorbent for the solid phase extraction mini-column. Trace inorganic mercury in wastewater samples was preconcentrated and determined by flow injection online mini-column sampling coupled with spectrophotometric determination. In acid medium, dithizone was employed as chelator with cetyltrimethylammonium bromide (CTMAB) to form a red neutral mercury-dithizone complex, which could be extracted quantificationally by solid phase extraction technique on the mini-column. Under the optimized conditions, the linearity and the detection limit of the proposed method were found to be 0.35 to 50.0 microg x L(-1) Hg2+ and 0.067 microg x L(-1) Hg2+, respectively. The enrichment factor of 25 times could be achieved with a 50 mL sampling volume and the developed procedure was successfully applied for the determination of mercury in the certified reference material (GSBZ50016-90) and the spiked dock wastewater samples with the recovery of 99%-103%. PMID:20828014

Zhang, Jun; Mao, Li-li; Yang, Gui-peng; Gao, Xian-chi; Tang, Xu-li



Colorimetric enantioselective recognition of chiral secondary alcohols via hydrogen bonding to a chiral metallocene containing chemosensor.  


An operationally simple colorimetric method for enantioselective detection of chiral secondary alcohols via hydrogen bonding interactions using a chiral ferrocene derivative is reported. PMID:23814789

Xu, Su-Ying; Hu, Bin; Flower, Stephen E; Jiang, Yun-Bao; Fossey, John S; Deng, Wei-Ping; James, Tony D




SciTech Connect

Conventional neutron detectors consisting of {sup 3}He tubes surrounded by a plastic moderator can be quite efficient in detecting fission spectrum neutrons, but do not indicate the direction of the incident radiation. We have developed a new directional detector based on double proton recoil in two separated planes of plastic scintillators. This method allows the spectrum of the neutrons to be measured by a combination of peak amplitude in the first plane and time of flight to the second plane. It also allows the determination of the angle of scattering in the first plane. If the planes are position-sensitive detectors, then the direction of the scattered neutron is known, and the direction of the incident neutron can be determined to lie on a cone of s fixed angle. The superposition of many such cones generates an image that indicates the presence of a localized source. Typical background neutron fluences from the interaction of cosmic rays with the atmosphere are low and fairly uniformly distributed in angle. Directional detection helps to locate a manmade source in the presence of natural background. Monte Carlo simulations are compared with experimental results.




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.



Novel colorimetric sensor for oral malodour.  


Volatile sulphur compounds are the primary constituents of oral malodour. Quantitative tools for the detection of oral malodour are beneficial to evaluate the intensity of malodour, analyse its causes and monitor the effectiveness of customized treatments. We have developed an objective, cost effective, do-it-yourself colorimetric sensor for oral malodour quantification. The sensor consisted of a sensing solution, a gas sampling unit for collecting a known volume of mouth air and a photometric detector. The sensing solution was iodine and the depletion of iodine on reaction with hydrogen sulphide was detected colorimetrically using starch. The detection limit of the sensor is 0.05 microg L(-1) of hydrogen sulphide, which is fit-for-purpose for oral malodour detection in healthy subjects as well as halitosis patients. Volatile sulphur compounds in mouth air were quantified in healthy human volunteers using this portable sensor and the detected levels were in the range of 0.2-0.4 microg L(-1). There was a good correlation between the VSC levels detected by the colorimetric sensor and halimeter (R(2)=0.934). The developed sensor can be easily fabricated in the laboratory, and it shows high potential to be used as a clinical evaluation tool for oral malodour assessments. PMID:20113721

Alagirisamy, Nethaji; Hardas, Sarita S; Jayaraman, Sujatha



Field evaluation of the direct detection of multidrug resistant Mycobacterium tuberculosis by nitrate reductase assay on 7H11 agar.  


In this study we evaluated the performance of colorimetric nitrate reductase assay (NRA) on Middlebrook 7H11 agar instead of Lowenstein-Jensen medium for detection of isoniazid (INH) and rifampin (RIF) resistance directly on 114 smear positive sputum specimens and compared the results with direct proportion method on LJ medium. The results of both methods were in 100% agreement for detection of RIF resistance while agreement for INH was 96.4%. The average turnaround time for NRA was 18.6 days and majority of the specimens gave positive results within 21 days. Thus direct NRA testing on smear positive sputum specimens by using 7H11 agar could be used as a fast, reliable and inexpensive method in resource starved settings. PMID:23507185

Satti, Luqman; Ikram, Aamer; Palomino, Juan Carlos; Martin, Anandi; Khan, Farooq Ahmad



Discriminating dark matter candidates using direct detection  

SciTech Connect

We examine the predictions for both the spin-dependent and spin-independent direct detection rates in a variety of new particle physics models with dark matter candidates. We show that a determination of both spin-independent and spin-dependent amplitudes on protons and neutrons can in principle discriminate different candidates of dark matter up to a few ambiguities. We emphasize the importance of making measurements with different spin-dependent sensitive detector materials and the need for significant improvement of the detector sensitivities. Scenarios where exchange of new colored particles contributes significantly to the elastic scattering cross sections are often the most difficult to identify, the LHC should give an indication whether such scenarios are relevant for direct detection.

Belanger, G. [LAPTH, Universite de Savoie, CNRS, B.P.110, F-74941 Annecy-le-Vieux (France); Nezri, E. [LAM, CNRS, Universite Aix-Marseille I, 2 place le Verrier, 13248 Marseille (France); Pukhov, A. [Skobeltsyn Inst. of Nuclear Physics, Moscow State Univ., Moscow 119992 (Russian Federation)



Direct Detection of Exoplanets with Polarimetry  

NASA Astrophysics Data System (ADS)

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

Wiktorowicz, Sloane; Laughlin, G.



Direct Detection of Exoplanets with Polarimetry  

NASA Astrophysics Data System (ADS)

The detection of scattered light from exoplanets gives direct access to physical conditions and composition of their atmospheres. Currently, most scattered light experiments focus on nearly edge-on, transiting systems. The temporal changes that occur during planetary occultations are used to suppress systematic errors, which would otherwise overwhelm the planetary signal. Linear polarimetry also has the potential to detect scattered light from exoplanets, because the polarization state of light scattered from a planetary atmosphere distinguishes it from both the direct light from the host star and thermal re-radiation from the planet. This scattered flux should be identifiable even in face-on systems, because both degree and position angle of polarization are modulated continuously throughout the orbit. We report on searches for exoplanetary scattered light using the POLISH2 polarimeter on the Lick 3-m telescope. This instrument has recently been upgraded with new detectors and a high-speed data acquisition system, which give a factor of ten improvement in precision with respect to the previous POLISH system (Wiktorowicz 2009). This polarimeter has achieved precision better than one part per million on V < 9 stars, and it is ideally suited for direct detection of close-in exoplanets. This work was supported by a UC Lab Fees Research Grant and UCO/Lick Observatory.

Wiktorowicz, Sloane; Graham, J. R.



Direct detection of methylation in genomic DNA  

PubMed Central

The identification of methylated sites on bacterial genomic DNA would be a useful tool to study the major roles of DNA methylation in prokaryotes: distinction of self and nonself DNA, direction of post-replicative mismatch repair, control of DNA replication and cell cycle, and regulation of gene expression. Three types of methylated nucleobases are known: N6-methyladenine, 5-methylcytosine and N4-methylcytosine. The aim of this study was to develop a method to detect all three types of DNA methylation in complete genomic DNA. It was previously shown that N6-methyladenine and 5-methylcytosine in plasmid and viral DNA can be detected by intersequence trace comparison of methylated and unmethylated DNA. We extended this method to include N4-methylcytosine detection in both in vitro and in vivo methylated DNA. Furthermore, application of intersequence trace comparison was extended to bacterial genomic DNA. Finally, we present evidence that intrasequence comparison suffices to detect methylated sites in genomic DNA. In conclusion, we present a method to detect all three natural types of DNA methylation in bacterial genomic DNA. This provides the possibility to define the complete methylome of any prokaryote.

Bart, A.; van Passel, M. W. J.; van Amsterdam, K.; van der Ende, A.



Facile detection of photogenerated reactive oxygen species in TiO2 nanoparticles suspension using colorimetric probe-assisted spectrometric method.  


This present study reports that reactive oxygen species (ROS), which mainly consist of hydroxyl (OH) and superoxide (O2(-)) radicals generated by the photocatalysis of TiO2 nanoparticles (TiO2 NPs) in suspension, can be quantitatively measured by the colorimetric probe-assisted spectrometric method without any interference by the TiO2 NPs. The interference effect of the TiO2 NPs with UV-vis spectroscopy was excluded by the selective separation of p-nitrosodimethylaniline (RNO) and tetrazolium salt (XTT) (probe compounds for OH and O2(-), respectively) from the TiO2 NPs in the suspension by centrifugation at a specified ionic strength adjusted with phosphate buffer (KH2PO4/NaOH, PB) solution. This colorimetric probe-assisted spectrometric method was also successfully applied to measure the steady-state production of photogenerated ROS in a TiO2 NPs suspension. PMID:23953250

Kim, Choonsoo; Park, Hee-Jin; Cha, Seoeun; Yoon, Jeyong



Aberration features in directional dark matter detection  

NASA Astrophysics Data System (ADS)

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

Bozorgnia, Nassim; Gelmini, Graciela B.; Gondolo, Paolo



Validation of colorimetric assay to detect complement-mediated antibody-dependent bactericidal activity against serogroups B and C Neisseria meningitidis  

Microsoft Academic Search

Colorimetric serum bactericidal assay (cSBA), based on the addition of glucose and a pH indicator to the culture medium after the bactericidal reaction, was validated. The precision measured as repeatability, intermediated precision, and reproducibility was determined as a percentage in titer coincidence between replicas ?50. Moreover the use of the freeze-dried complement was evaluated in comparison to the traditionally stored

Tamara Rodr??guez; Miriam Lastre; Bárbara Cedré; Esther Mar??a Fajardo; Judith del Campo; Ileana Delgado; Gustavo Sierra; Oliver Pérez



Colorimetric redox-indicator methods for the rapid detection of multidrug resistance in Mycobacterium tuberculosis: a systematic review and meta-analysis  

Microsoft Academic Search

Objectives: With the spread of multidrug-resistant tuberculosis (MDR-TB) there is increasing demand for new accurate and cost-effective tools for rapid drug susceptibility testing (DST), particularly for developing countries. The reference standard method used today for DST is very slow and cumbersome. Colorimetric assays using redox indicators have been proposed to be used in low-resource countries as rapid alternative culture methods

Anandi Martin; Francoise Portaels; Juan Carlos Palomino



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

Microsoft Academic Search

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

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



Direct detection of galactic halo dark matter.  


The Milky Way galaxy contains a large, spherical component which is believed to harbor a substantial amount of unseen matter. Recent observations indirectly suggest that as much as half of this "dark matter" may be in the form of old, very cool white dwarfs, the remnants of an ancient population of stars as old as the galaxy itself. We conducted a survey to find faint, cool white dwarfs with large space velocities, indicative of their membership in the galaxy's spherical halo component. The survey reveals a substantial, directly observed population of old white dwarfs, too faint to be seen in previous surveys. This newly discovered population accounts for at least 2 percent of the halo dark matter. It provides a natural explanation for the indirect observations, and represents a direct detection of galactic halo dark matter. PMID:11264524

Oppenheimer, B R; Hambly, N C; Digby, A P; Hodgkin, S T; Saumon, D



Direct dark matter detection: The next decade  

NASA Astrophysics Data System (ADS)

Direct dark matter searches are promising techniques to identify the nature of dark matter particles. I describe the future of this field of research, focussing on the question of what can be achieved in the next decade. I will present the main techniques and R&D projects that will allow to build so-called ultimate WIMP detectors, capable of probing spin-independent interactions down to the unimaginably low cross section of 10-48 cm2, before the irreducible neutrino background takes over. If a discovery is within the reach of a near-future dark matter experiment, these detectors will be able to constrain WIMP properties such as its mass, scattering cross section and possibly spin. With input from the LHC and from indirect searches, direct detection experiments will hopefully allow to determine the local density and to constrain the local phase-space structure of our dark matter halo.

Baudis, Laura



Miniature laser direct-detection radar  

NASA Astrophysics Data System (ADS)

A miniature laser with a total volume less than 15 cu cm and weight less than 100 g has been designed, fabricated, and assembled. The laser uses a composite rod consisting of Nd:Cr:GSGG material rod cladded with an Er:Cr:YSGG tube. The laser provides output at 1 and 3 micron wavelengths. The size and weight reduction is obtained by chemical pumping which eliminates the prime power and the power supply. The laser is used as an illuminator in a direct detection radar.

Acharekar, Madhu; Lebeau, Robert



Complementarity of dark matter direct detection targets  

SciTech Connect

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

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



Direct detection of dark matter debris flows  

NASA Astrophysics Data System (ADS)

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

Kuhlen, Michael; Lisanti, Mariangela; Spergel, David N.



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

Technology Transfer Automated Retrieval System (TEKTRAN)

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


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)




SciTech Connect

We present Hubble Space Telescope observations in the far UV of the ultraluminous X-ray source in NGC 6946 associated with the optical nebula MF 16. Both a point-like source coincident with the X-ray source and the surrounding nebula are detected in the FUV. The point source has a flux of 5 x 10{sup -16} erg s{sup -1} cm{sup -2} A{sup -1}, and the nebula has a flux of 1.6 x 10{sup -15} erg s{sup -1} cm{sup -2} A{sup -1}, quoted at 1533 A and assuming an extinction of A{sub V} = 1.54. Thus, MF 16 appears to host the first directly detected ultraluminous UV source. The flux of the point-like source is consistent with a blackbody with T{approx} 30,000 K, possibly from a massive companion star, but this spectrum does not create sufficient ionizing radiation to produce the nebular He II flux, and a second, hotter emission component would be required. A multicolor disk blackbody spectrum truncated with an outer disk temperature of {approx}16,000 K provides an adequate fit to the FUV, B, V, I, and He II fluxes and can produce the needed ionizing radiation. Additional observations are required to determine the physical nature of the source.

Kaaret, Philip; Feng Hua; Wong, Diane S. [Department of Physics and Astronomy, Van Allen Hall, University of Iowa, Iowa City, IA 52242 (United States); Tao Lian [Department of Engineering Physics and Center for Astrophysics, Tsinghua University, Beijing 100084 (China)



Ion Channeling in Direct Dark Matter Detection  

NASA Astrophysics Data System (ADS)

The channeling of the ion recoiling after a collision with a WIMP changes the ionization signal in direct detection experiments, producing a larger signal than otherwise expected. We give estimates of the fraction of channeled recoiling ions in NaI (Tl), Si, Ge, CsI, and solid Xe, Ar and Ne crystals using analytic models produced since the 1960's and 70's to describe channeling and blocking effects. We find that the channeling fraction of recoiling lattice nuclei is smaller than that of ions that are injected into the crystal and that it is strongly temperature dependent. Channeling is a directional effect which depends on the velocity distribution of WIMPs in the dark halo of our Galaxy and could lead to a daily modulation of the signal. We compute upper bounds to the expected amplitude of daily modulation due to channeling using our estimates of the channeling fractions. After developing the general formalism, we examine the possibility of finding a daily modulation due to channeling in the data already collected by the DAMA experiment. We find that even the largest daily modulation amplitudes would not be observable for WIMPs in the standard halo in the 13 years of data taken by the DAMA collaboration. For these to be observable the DAMA total rate should be 1/40 of what it is or the total DAMA exposure should be 40 times larger. The daily modulation due to channeling will be difficult to measure in future experiments.

Bozorgnia, Nassim


Semi-automated direct colorimetric measurement of creatine kinase isoenzyme MB activity after extraction from serum by use of a CK-MB-specific monoclonal antibody.  


This semi-automated colorimetric assay for the MB isoenzyme of creatine kinase (EC is based on a monoclonal antibody ("Conan-MB") specific for this isoenzyme and is a modification of a previously published method (Vaidya et al., Clin Chem 1986;32:657-63). A 0.64-cm bead coated with 2 to 3 micrograms of antibody is incubated with 100 microL of serum and 10 microL of 0.2 mol/L beta-mercaptoethanol for 1 h at room temperature, to extract CK-MB. The beads are washed with de-ionized water and incubated with CK substrate for 45 min at 37 degrees C. A solution containing trans-1,2-diaminocyclohexane-N,N,N', N'-tetraacetic acid, p-iodonitrotetrazolium violet, and diaphorase is added and the resulting colored product is measured at 492 nm. The standard curve is linear to 200 U of CK-MB per liter, and analytical recovery is 97-113%. Total assay CV for low (9.7 U/L) and high (50.7 U/L) quality-control materials was 14.1% (n = 1878) and 11.6% (n = 1842), respectively. CK-MB activity correlated well (r = 0.978, n = 226) with CK-MB measured by a two-site mass immunoassay, and 99.4% of samples with CK-MB greater than or equal to 12 U/L (n = 347) were verified by electrophoresis on agarose. PMID:3349610

Landt, Y; Vaidya, H C; Porter, S E; Whalen, K; McClellan, A; Amyx, C; Parvin, C A; Kessler, G; Nahm, M H; Dietzler, D N



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



Selective colorimetric and fluorescent detection of HSO4- with sodium(I), magnesium(II) and aluminium(III) xanthone-crown ether complexes.  


Xanthone-crown ether (1) reacts with NaClO(4), Mg(ClO(4))(2) and Al(ClO(4))(3) forming the one-dimensional chain dinuclear polymer [Na(2).1.(ClO(4))(2)] (2), the mononuclear complex [Mg.1.(H(2)O)(2)](ClO(4))(2) (3) and an interesting sandwich complex [Al.(1)(2).(H(2)O)(6)](ClO(4))(3) (4) with different ratios of metal-to-ligand, respectively. The anion recognition experiment results show that the magnesium complex (3) is a good colorimetric and fluorescent detector for HSO(4)(-) with high sensitivity and selectivity. PMID:18594706

Shen, Rui; Pan, Xiaobo; Wang, Huifang; Yao, Lihui; Wu, Jincai; Tang, Ning



Data representation and feature selection for colorimetric sensor arrays used as explosives detectors  

Microsoft Academic Search

Within the framework of the strategic research project Xsense at the Technical University of Denmark, we are developing a colorimetric sensor array which can be useful for detection of explosives like DNT, TNT, HMX, RDX and TATP and identification of volatile organic compounds in the presence of water vapor in air. In order to analyze colorimetric sensors with statistical methods,

Tommy S. Alstrom; Jan Larsen; Natalie V. Kostesha; Mogens H. Jakobsen; Anja Boisen



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




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



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


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



Colorimetric protein assay techniques.  


There has been an increase in the number of colorimetric assay techniques for the determination of protein concentration over the past 20 years. This has resulted in a perceived increase in sensitivity and accuracy with the advent of new techniques. The present review considers these advances with emphasis on the potential use of such technologies in the assay of biopharmaceuticals. The techniques reviewed include Coomassie Blue G-250 dye binding (the Bradford assay), the Lowry assay, the bicinchoninic acid assay and the biuret assay. It is shown that each assay has advantages and disadvantages relative to sensitivity, ease of performance, acceptance in the literature, accuracy and reproducibility/coefficient of variation/laboratory-to-laboratory variation. A comparison of the use of several assays with the same sample population is presented. It is suggested that the most critical issue in the use of a chromogenic protein assay for the characterization of a biopharmaceutical is the selection of a standard for the calibration of the assay; it is crucial that the standard be representative of the sample. If it is not possible to match the standard with the sample from the perspective of protein composition, then it is preferable to use an assay that is not sensitive to the composition of the protein such as a micro-Kjeldahl technique, quantitative amino acid analysis or the biuret assay. In a complex mixture it might be inappropriate to focus on a general method of protein determination and much more informative to use specific methods relating to the protein(s) of particular interest, using either specific assays or antibody-based methods. The key point is that whatever method is adopted as the 'gold standard' for a given protein, this method needs to be used routinely for calibration. PMID:10075906

Sapan, C V; Lundblad, R L; Price, N C



A novel and efficient colorimetric chemosensor for detection and determination of biologically important ions in DMSO/H2O media using bromo pyrogallol red chemosensors with analytical applications.  


An efficient colorimetric chemosensor with bromo pyrogallol red (BPR) as an easily available dye demonstrated a high chromogenic selectivity for Fe(3+) over other cations with detection limit of 5.1 ?mol L(-1). The complex of Fe(3+) with BPR displayed ability to detect of up to 4.4 and 25.6 ?mol L(-1) for acetate (AcO(-)) and benzoate ions (BzO(-)) in DMSO/H(2)O (9:1 v/v) media respectively over a large number of other anions. Both processes proceeded with distinct visual color changes in DMSO/H(2)O (9:1 v/v). The linear dynamic ranges for the determinations of Fe(3+), AcO(-) and BzO(-) were 2.5-24.0, 2.5-20.5 and 28.0-42.0 ?g mL(-1) respectively. This chemosensor was successfully applied for the determination of Fe(3+) and of carboxylate anions in environmental samples. This is the first article of a chemosensor capable of detecting both Fe(3+) and anions (AcO(-) and BzO(-)) using single detection method in a single cell. PMID:22847073

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




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.




Colorimetric Sensor Arrays System Based on FPGA for Image Recognition  

Microsoft Academic Search

A FPGA-based image recognition system is designed for colorimetric sensor array in order to recognize a wide range of volatile organic compounds. The gas molecule is detected by the responsive sensor array and the responsive image is obtained. The image is decomposed to RGB color components using CMOS image sensor. An embedded image recognition archi- tecture based on Xilinx Spartan-3

Rui Chen; Jian-Hua Xu; Ya-Dong Jiang


Avalanche photodiode detection statistics for direct detection laser radar  

NASA Astrophysics Data System (ADS)

The detection statistics of avalanche photodiode detectors when used in laser radar systems are examined. In the laser radar systems considered here, a diffuse hard target is illuminated by a transmitted laser beam and the photons subtended by the receiving aperture and focused onto the detector obey negative-binomial statistics. The specific negative-binomial distribution is determined by the coherence length of the laser and the angular subtense of the target. These received photons are converted into photoelectrons and amplified by the avalanche photodiode which is an imperfect device. Dark current, amplifier, and background-produced noise electrons must be exceeded by the avalanche photodiode output electron pulse for a detection to occur. The required mean number of signal photons from a given negative-binomial target as a function of probability of detection and probability of false alarm is calculated. For perfect photon counters, the probability of detection at high discrete false alarm probabilities is also calculated. It is shown that for probabilities of detection of 0.9, three to five times more laser power may be required than for the generally assumed Poisson signal photons case. At probabilities of detection of 0.3, corresponding to multipulse waveforms, the statistics are independent of the target photon distribution.

Youmans, Douglas G.



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.



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.




Microsoft Academic Search

A method of the colorimetric determination of zirconium with ; phenylfluron (2,3,7-trioxide-9-phenylcompound with its maximum light absorption ; at 535 m mu . The compound is soluble in ethanol, butanol, methyl ethyl ketone, ; isoamyl alcohol, butyl formate, and cyclohexanol. The ions which interfere with ; the determination are listed. The method can be adapted for the determination of ;

F. G. Zharovskiy; A. T. Philipenko



A direct detection of Escherichia coli genomic DNA using gold nanoprobes  

PubMed Central

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



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



Photonic Crystal Structures with Tunable Structure Color as Colorimetric Sensors  

PubMed Central

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

Wang, Hui; Zhang, Ke-Qin



Photonic crystal structures with tunable structure color as colorimetric sensors.  


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

Wang, Hui; Zhang, Ke-Qin



Direct Electrochemical Sensor for Fast Reagent-Free DNA Detection.  

National Technical Information Service (NTIS)

A novel reagentless direct electrochemical DNA sensor has been developed using ultrathin films of the conducting polymer polypyrrole doped with an oligonucleotide probe. Our goal was to develop a prototype electrochemical DNA sensor for detection of a bio...

E. Komarova A. Bogomolova M. Aldissi



Colorimetric determination of indolic drugs.  


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



An Improved Colorimetric Transaminase Assay  

Microsoft Academic Search

The chromogenic reaction between a diazonium salt and oxalacetic acid produced by glutamic-oxalacetic transaminase has been completely stabilized by the addition of acid and a surface-active agent instead of water. This improvement markedlysimplifiesthe procedure byallowing the samples to be read at any time. W\\/E RECENTLY reported a new colorimetric assay for glutamic-oxal- acetic transaminase which involves coupling the oxalacetate formed

Arthur L. Babson; George E. Philips


Brief Report: Eye Direction Detection Improves with Development in Autism  

Microsoft Academic Search

Eye direction detection has been claimed to be intact in autism, but the development of this skill has not been investigated.\\u000a Eleven children with autism and 11 typically developing children performed a demanding face-to-face eye direction detection\\u000a task. Younger children with autism demonstrated a deficit in this skill, relative to younger control participants. Older children\\u000a with autism were as accurate

Simon Webster; Douglas D. Potter



Direct electrochemical sensor for fast reagent-free DNA detection  

Microsoft Academic Search

A novel reagentless direct electrochemical DNA sensor has been developed using ultrathin films of the conducting polymer polypyrrole doped with an oligonucleotide probe. Our goal was to develop a prototype electrochemical DNA sensor for detection of a biowarfare pathogen, variola major virus. The sensor has been optimized for higher specificity and sensitivity. It was possible to detect 1.6fmol of complementary

Elena Komarova; Matt Aldissi; Anastasia Bogomolova



Lightning Direction-Finding Systems for Forest Fire Detection  

Microsoft Academic Search

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

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



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


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

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



Colorimetric Hg2+ sensing in water: from molecules toward low-cost solid devices.  


A new colorimetric molecular sensor allowing for cheap, fast, sensitive, and highly selective naked-eye detection of Hg(2+) in water is described. This molecule combines a 1,8-diaminoanthraquinone signaling subunit and phosphonic acid esters that confer the water solubility to the dye (R = H). A ready-to-use colorimetric solid sensor was obtained by incorporating an amphiphilic analog (R = OC(12)H(25)) exhibiting similar binding properties and optical responses in an agarose film. PMID:23343003

Ermakova, Elizaveta; Michalak, Julien; Meyer, Michel; Arslanov, Vladimir; Tsivadze, Aslan; Guilard, Roger; Bessmertnykh-Lemeune, Alla



High sensitive, colorimetric, isothermal nucleic acids amplification: A versatile platform for protein biosensors  

Microsoft Academic Search

Colorimetric, in situ, isothermal rolling circle amplification (RCA)-based biosensor was developed as a novel, versatile nucleic acid-based amplification machine for platelet-derived growth factor (PDGF) detection. This antibody-free biosensor utilized nucleic acids immobilized on the plate and DNA aptamers to capture the target protein. As compared to the conventional fluorescence measurement [1], the reported colorimetric method can facilitate the development of

Ming-Yu Lin; Yu-Wei Chang; Yu-Ting Tai; Yuh-Shyong Yang; Yang-Tung Huang



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


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



Can the Existence of Dark Energy be Directly Detected?  

SciTech Connect

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

Perl, Martin L.; /SLAC /KIPAC, Menlo Park



Direct Detection of Extrasolar Planets with the Thirty Meter Telescope  

Microsoft Academic Search

20-40m Extremely Large Telescopes (ELTs) may become operational in the next decade, with revolutionary scientific capabilities in several areas, including direct detection of extrasolar planets. One such project is the massively-segmented Thirty Meter Telescope. I will briefly discuss planet detection phase space and the potential TMT roles and present a possible TMT Extreme AO\\/coronagraph instrument architecture, the Planet Formation Imager.

B. Macintosh



Accurate colorimetric calibration of CRT monitors  

Microsoft Academic Search

Several models have been proposed for the colorimetric calibration of CRT monitors. These models use different mathematical functions to approximate the relationship between the digital frame buffer values driving a color channel and the phosphor emission of that channel. Here we present an evaluation of colorimetric errors in terms of CIELAB lightness, hue, and chroma deviations caused by insufficient fit

P. Bodrogi; K. Muray


Colorimetric phosphorescence measurements with a color camera for oxygen determination  

NASA Astrophysics Data System (ADS)

We developed a simple oxygen imaging platform with phosphorescent oxygen sensor films to demonstrate a quantitative oxygen determination method utilizing a color CCD camera. Phosphorescence quenching of a luminophore Pt(II) meso-tetrakis (pentafluorophenyl) porphyrin complex (PtTFPP) immobilized in poly (dimethylsiloxane) (PDMS) matrix, is the principal detection mechanism. This sensor material was cast to form a film on the bottom surface of a transparent Petri dish. As levels of dissolved oxygen increased, phosphorescence of the complex decreased, allowing for measurement of oxygen levels which developed in the sensor film. A camera with a charge-coupled device (CCD) was used in conjunction with processing software to quantify oxygen levels colorimetrically. Microscopic images were collected using a CCD camera and stored as a set of red/green/blue (RGB) images. Phosphorescence excitation (390 nm peak) is limited to the blue (B) pixels of the CCD chip, and these values were discarded; while retaining the oxygen-responsive phosphorescence emission (645 nm peak) almost identical with the response range of the red (R) pixels. Red pixel intensity analysis effectively extracts color intensity information, which can be in turn directly related to oxygen contents. Color CCD cameras allow simultaneous acquisition of many types of chemical information by combining the merits of digital imaging with the attributes of spectroscopic measurement. Therefore, use of color CCD cameras is considered as an inexpensive alternative to time-resolved imaging for relatively short-term monitoring.

Bhagwat, Prajakta; Achanta, Gowthami Satya; Henthorn, David; Kim, Chang-Soo



In-field determination of nanomolar nitrite in seawater using a sequential injection technique combined with solid phase enrichment and colorimetric detection.  


A novel sequential injection method for the determination of nitrite at nanomolar level in seawater samples has been developed. The pink azo compound was formed based on the Griess reaction and quantitatively adsorbed onto a Sep-Pak C18 cartridge. The enriched azo compound was rinsed with water and ethanol (28%, v/v) in turn, and then eluted with an eluent containing 26.6% (v/v) ethanol and 0.108 mol L(-1) H(2)SO(4). Finally the azo compound was measured using a spectrophotometer at 543 nm. Under the optimized conditions, the linear calibration ranges were 0.71-42.9 nmol L(-1) for a 150-mL sample and 35.7-429 nmol L(-1) for a 15-mL sample. The relative standard deviation of 8 measurements was 1.44% for 14.3 nmol L(-1) nitrite. For the 150 mL sample, the detection limit was estimated to be 0.1 nmol L(-1). The throughput of the method was about 4 samples per hour. The proposed method has been successfully applied to the in-field determination of nanomolar concentrations of nitrite in seawater. PMID:18558127

Chen, Guohe; Yuan, Dongxing; Huang, Yongming; Zhang, Min; Bergman, Maria



Generalized halo independent comparison of direct dark matter detection data  

NASA Astrophysics Data System (ADS)

We extend the halo-independent method to compare direct dark matter detection data, so far used only for spin-independent WIMP-nucleon interactions, to any type of interaction. As an example we apply the method to magnetic moment interactions.

Del Nobile, Eugenio; Gelmini, Graciela; Gondolo, Paolo; Huh, Ji-Haeng



Silicon avalanche diodes for direct detection of nuclear particles  

Microsoft Academic Search

The junction termination extension (JTE) avalanche diode (AD) for direct detection of nuclear particles was built with the use of planar technology processing. The active area of the detector with JTE structure have been processed simultaneously, by one implantation of boron step followed by the diffusion up to the depth of 14 mum. The contact layer (p+ region) had the

I. B. Chistokhin; O. P. Pchelyakov; E. G. Tishkovsky; V. I. Obodnikov; V. V. Maksimov; A. A. Ivanov; E. I. Pinzhenin; E. Gramsch



Impact of laser frequency offset on DQPSK direct detection  

Microsoft Academic Search

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

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



Development of sensors for direct detection of organophosphates  

Microsoft Academic Search

pH-sensitive field effect transistors (FET) were modified with organophosphate hydrolase (OPH) and used for direct detection of organophosphate compounds. OPH is the organophosphate degrading gene product isolated from Pseudomonas diminuta. OPH was selected as an alternative to acetylcholinesterase, which requires inhibition mode sensor operation, enzyme regeneration before reuse, long sample incubation times, and a constant source of acetylcholine substrate. OPH

A. W. Flounders; A. K. Singh; J. V. Volponi; S. C. Carichner; K. Wally; A. S. Simonian; J. R. Wild; J. S. Schoeniger



Direct seismic detection of methane hydrate on the Blake Ridge  

Microsoft Academic Search

Seismic detection of methane hydrate often relies on indirect or equivocal methods. New multichannel seis- mic reflection data from the Blake Ridge, located ap- proximately 450 km east of Savannah, Georgia, show three direct seismic indicators of methane hydrate: (1) a paleo bottom-simulating reflector (BSR) formed when methane gas froze into methane hydrate on the eroding eastern flank of the

Matthew J. Hornbach; W. Steven Holbrook; Andrew R. Gorman; Kara L. Hackwith; Daniel Lizarraldez; Ingo Pecher



Some implications of TCM for optical direct-detection channels  

Microsoft Academic Search

Consideration is given to the optical direct-detection channel, and it is shown how simple trellis-coded modulation (TCM) can be used to improve performance or increase throughput (in bits per second) without bandwidth expansion or performance loss. In fact, a modest performance gain can be achieved. Although the approach can be used with other signal constellations, the authors concentrate on signals

C. N. Georghiades



Directional statistics for realistic weakly interacting massive particle direct detection experiments. II. 2D readout  

NASA Astrophysics Data System (ADS)

The direction dependence of the WIMP direct detection rate provides a powerful tool for distinguishing a WIMP signal from possible backgrounds. We study the number of events required to discriminate a WIMP signal from an isotropic background for a detector with 2-d readout using nonparametric circular statistics. We also examine the number of events needed to (i) detect a deviation from rotational symmetry, due to flattening of the Milky Way halo and (ii) detect a deviation in the mean direction due to a tidal stream. If the senses of the recoils are measured then of order 20--70 events (depending on the plane of the 2-d readout and the detector location) will be sufficient to reject isotropy of the raw recoil angles at 90% confidence. If the senses can not be measured these number increase by roughly 2 orders of magnitude (compared with an increase of 1 order of magnitude for the case of full 3-d readout). The distributions of the reduced angles, with the (time-dependent) direction of solar motion subtracted, are far more anisotropic, however, and if the isotropy tests are applied to these angles then the numbers of events required are similar to the case of 3-d readout. A deviation from rotational symmetry will only be detectable if the Milky Way halo is significantly flattened. The deviation in the mean direction due to a tidal stream is potentially detectable, however, depending on the density and direction of the stream. The meridian plane (which contains the Earth’s spin axis) is, for all detector locations, the optimum readout plane for rejecting isotropy. However readout in this plane can not be used for detecting flattening of the Milky Way halo or a stream with direction perpendicular to the galactic plane. In these cases the optimum readout plane depends on the detector location.

Morgan, Ben; Green, Anne M.



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



Closing supersymmetric resonance regions with direct detection experiments  

NASA Astrophysics Data System (ADS)

In order for neutralino dark matter to avoid being overproduced in the early Universe, these particles must annihilate (or coannihilate) rather efficiently. Neutralinos with sufficiently large couplings to annihilate at such high a rate (such as those resulting from gaugino-Higgsino mixing, as in “well-tempered” or “focus point” scenarios), however, have become increasingly disfavored by the null results of XENON100 and other direct detection experiments. One of the few remaining ways that neutralinos could potentially evade such constraints is if they annihilate through a resonance, as can occur if 2m?0 falls within about ˜10% of either mA/H, mh, or mZ. If no signal is observed from upcoming direct detection experiments, the degree to which such a resonance must be tuned will increase significantly. In this paper, we quantify the degree to which such a resonance must be tuned in order to evade current and projected constraints from direct detection experiments. Assuming a future rate of progress among direct detection experiments that is similar to that obtained over the past decade, we project that within 7 years the light Higgs and Z pole regions will be entirely closed, while the remaining parameter space near the A/H resonance will require that 2m?0 be matched to the central value (near mA) to within less than 4%. At this rate of progress, it will be a little over a decade before multiton direct detection experiments will be able to close the remaining, highly tuned, regions of the A/H resonance parameter space.

Hooper, Dan; Kelso, Chris; Sandick, Pearl; Xue, Wei



Colorimetric, high-throughput assay for screening Angiotensin I-converting enzyme inhibitors.  


Angiotensin I-converting enzyme (ACE) plays a pivotal role in blood pressure regulation. A colorimetric assay to measure hippuric acid (HA) was transformed into a rapid ACE assay wherein the released HA from the substrate hippuryl-histidyl-leucine (HHL) is mixed with pyridine and benzene sulfonyl chloride. The resulting yellow color with a lambda(max) at 410 nm is directly proportional to the released HA. The limit of detection and limit of quantitation were 1.46 x 10(-7) and 4.43 x 10(-7) M HA. ACE activities of different tissues using this method were comparable to the standard high-performance liquid chromatography (HPLC) method. Kinetic studies showed a K(m) of 30.8 +/- 0.1 x 10(-6) M for HHL and V(max) of 1.3 +/- 0.01 x 10(-6) mol/min for porcine lung ACE. This assay coupled with captopril and lisinopril showed IC(50) values of 1.1 +/- 0.05 x 10(-9) and 2.5 +/- 0.03 x 10(-9) M, respectively. A 96-well microplate format of this method was used to screen the ACE inhibitory potential of peptides fractionated from an enzymatic hydrolysate of arachin. The precision, accuracy, reproducibility, and excellent correlation demonstrated between the colorimetric and the often-used HPLC method renders this extraction-free method a powerful tool for high-throughput screening of ACE inhibitors. PMID:19839596

Jimsheena, V K; Gowda, Lalitha R



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



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



Direct detection of expanded trinucleotide repeats using DNA hybridization techniques  

SciTech Connect

Recently, unstable trinucleotide repeats have been shown to be the etiologic factor in several neuropsychiatric diseases, and they may play a similar role in other disorders. To our knowledge, a method that detects expanded trinucleotide sequences with the opportunity for direct localization and cloning has not been achieved. We have developed a set of hybridization-based methods for direct detection of unstable DNA expansion. Our analysis of myotonic dystrophy patients that possess different degrees of (CTG){sub n} expansion, versus unaffected controls, has demonstrated the identification of the trinucleotide instability site without any prior information regarding genetic map location. High stringency modified Southern blot hybridization with a PCR-generated trinucleotide repeat probe allowed us to detect the DNA fragment containing the expansion in myotonic dystrophy patients. The same probe was used for fluorescent in situ hybridization and several regions of (CTG){sub n}/(CAG){sub n} repeats in the human genome were detected, including the myotonic dystrophy locus on chromosome 19q. These strategies can be applied to directly clone genes involved in disorders caused by unstable DNA.

Petronis, A.; Tatuch, Y.; Kennedy, J.L. [Univ. of Toronto (Canada)] [and others



Enzyme-free colorimetric bioassay based on gold nanoparticle-catalyzed dye decolorization.  


A novel, enzyme-free and aptamer-based colorimetric platform for protein detection has been developed, which takes advantage of aptamer-functionalized magnetic beads (MBs) for target capture, concentration and separation, and aptamer-conjugated gold nanoparticle (AuNP)-catalyzed color bleaching reaction of methyl orange (MO) to generate the colorimetric signals. It was demonstrated that the proposed colorimetric sensing strategy enables simple, cost-effective, sensitive and specific thrombin detection without the use of any enhancing solutions and enzymes. Herein, by naked eye observation, we can detect the human thrombin with a detection limit of approximately 320 pM, which can be further decreased to 30 pM with the help of a UV-vis instrument. In addition, this method also works for targets with two or more binding sites. PMID:23223492

Li, Wei; Li, Jie; Qiang, Weibing; Xu, Jingjuan; Xu, Danke



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


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



Improved determination of the WIMP mass from direct detection data  

NASA Astrophysics Data System (ADS)

Direct detection experiments searching for weakly interacting massive particle (WIMP) dark matter typically use a simplified model of the Galactic halo to derive parameter constraints. However, there is strong evidence that this Standard Halo Model is not a good approximation to our Galaxy. We discuss previous attempts to extract the WIMP mass, cross section and speed distribution from direct detection data and show that these lead to significant biases in the reconstructed parameter values. We develop and test an alternative model-independent method based on parametrizing the momentum distribution of the WIMPs. This allows us to limit the analysis only to those regions of momentum space to which the experiments are sensitive. The method can be applied to a single experiment to extract information about the distribution function, as well as information on the degenerate WIMP mass and interaction cross section combined in a single parameter. This degeneracy can be broken by including data from additional experiments, meaning that the WIMP mass and speed distribution can be recovered. We test the momentum parametrization method using mock data sets from proposed ton-scale direct detection experiments, showing that it exhibits improved coverage properties over previous methods, as well as significantly reduced bias. We are also able to accurately reconstruct the shape of the WIMP speed distribution but distinguishing between different underlying distributions remains difficult.

Kavanagh, Bradley J.; Green, Anne M.



Direct detection method of oligosaccharides by high-performance liquid chromatography with charged aerosol detection.  


A simple and rapid detection method of oligosaccharides using high-performance liquid chromatography with a charged aerosol detection (HPLC-CAD) was studied. The direct detection of a sialylglycopeptide (SGP) derived from egg yolk was accomplished by HPLC-CAD using an amido-silica column, and its limit of detection was 0.40 pmol [signal-to-noise ratio (S/N) = 3]. The sensitivity of this method was lower than that of the fluorescence detection; however, the method showed approximately 5 times higher sensitivity than that using the conventional UV absorbance detection. Furthermore, this method was used for the analysis of the acid hydrolysis products of SGP. Monosialo- and asialo-oligosaccharides as well as free sialic acid were detected without using fluorescent derivatization. These results indicate that the present method is a new tool for the analysis of oligosaccharides. PMID:17236241

Inagaki, Shinsuke; Min, Jun Zhe; Toyo'oka, Toshimasa



Laboratory Evaluation of a Colorimetric Hydrazine Dosimeter.  

National Technical Information Service (NTIS)

A passive, colorimetric dosimeter badge was manufactured for NASA by GMD Systems. The badge consisted of two indicators: para-dimethylaminobenzaldehyde (PDAB) and vanillin. When exposed to hydrazine or monomethylhydrazine (MMH), the PDAB turns orange and ...

A. Thurow J. R. Wyatt K. P. Crossman P. T. Carver S. L. Rose-Pehrsson



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



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.



An easy colorimetric assay for glycosyltransferases.  


Glycosyltransferases are involved in biosynthesis of both protein-bound and non-bound glycans that have multiple and important biological functions in all species. A variety of methods for assaying glycosyltransferase activity have been developed driven by the specific interests and type of information required by researchers. In this work, a novel colorimetric assay for the glycosyltransferase-catalyzed reaction was established. Compared with measuring the newly formed product, which might not exhibit visible absorption, the unreacted acceptor could be readily detected by measuring the visible absorption of the hydrolysis product. In the assay, 4-nitrophenyl-beta-D-glycoside (glycosyl-beta-pNP) is used as the glycosyl acceptor, which can be hydrolyzed by a special exoglycosidase to release the p-nitrophenol before glycosylation reactions. Absorbance change of the p-nitrophenolate corresponds to unreacted glycosyl acceptor that accompanied the glycosyl transfer. The assay is demonstrated to be useful in the initial characterization of recombinant glycosyltransferases for their kinetic parameters, optimal metal cofactor, and pH value. It provides a simple, sensitive, and quantitative method for assessing glycosyltransferase activity and is thus expected to have broad applications including automated high-throughput screening. PMID:20673220

Shen, Rui; Wang, Shuai; Ma, Xiaofeng; Xian, Junyang; Li, Jing; Zhang, Lianwen; Wang, Peng



Colorimetric Assays for Quantitative Analysis and Screening of Epoxide Hydrolase Activity  

Microsoft Academic Search

Focusing on directed evolution to tailor enzymes as usable biocatalysts for fine chemistry, we have studied in detail several colorimetric assays for quantitative analysis of epoxide hydrolase (EH) activity. In particular, two assays have been optimized to characterize variants issued from the directed evolution of the EH from Aspergillus niger. Assays described in this paper are sufficiently reliable for quantitative

F. Cedrone; T. Bhatnagar; Jacques C. Baratti



Detecting tubular structures via direct vector field singularity characterization.  


The initial step of vessel segmentation in 3D is the detection of vessel centerlines. The proposed methods in literature are either dependent on vessel radius and/or have low response at vessel bifurcations. In this paper we propose a 3D tubular structure detection method that removes these two drawbacks. The proposed method exploits the observations on the eigenvalues of the Hessian matrix as is done in literature, yet it employs a direct 3D vector field singularity characterization. The Gradient Vector Flow vector field is used and the eigenvalues of its Jacobian are exploited in computing a parameter free vesselness map. Results on phantom and real patient data exhibit robustness to scale, high response at vessel bifurcations, and good noise/non-vessel structure suppression. PMID:21097293

Cabuk, Aytekin D; Alpay, Erdenay; Acar, Burak



Problem detection during tripping operations in horizontal and directional wells  

SciTech Connect

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

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



Direct Detection and Sequencing of Damaged DNA Bases  

PubMed Central

Products of various forms of DNA damage have been implicated in a variety of important biological processes, such as aging, neurodegenerative diseases, and cancer. Therefore, there exists great interest to develop methods for interrogating damaged DNA in the context of sequencing. Here, we demonstrate that single-molecule, real-time (SMRT®) DNA sequencing can directly detect damaged DNA bases in the DNA template - as a by-product of the sequencing method - through an analysis of the DNA polymerase kinetics that are altered by the presence of a modified base. We demonstrate the sequencing of several DNA templates containing products of DNA damage, including 8-oxoguanine, 8-oxoadenine, O6-methylguanine, 1-methyladenine, O4-methylthymine, 5-hydroxycytosine, 5-hydroxyuracil, 5-hydroxymethyluracil, or thymine dimers, and show that these base modifications can be readily detected with single-modification resolution and DNA strand specificity. We characterize the distinct kinetic signatures generated by these DNA base modifications.



Direct optical detection in fragment-based screening.  


Label-free biosensors based on direct optical detection principles are widely used in many different fields of research. Currently the higher level of automation and the increasing throughput of this technology are stimulating the interest of pharmaceutical companies. The information gained with label-free biosensors can be extremely valuable during the drug design process, particularly in combination with complementary techniques, including NMR, mass spectrometry and X-ray crystallography. In this article we focus on the advantages of direct optical biosensors especially in the field of fragment-based drug design, which is a widely used and extremely promising concept. Furthermore, we present optical biosensors as versatile tools for fragment-based screening and the future drug design process. PMID:18979089

Pröll, Florian; Fechner, Peter; Proll, Günther



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


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



Some implications of TCM for optical direct-detection channels  

NASA Astrophysics Data System (ADS)

Consideration is given to the optical direct-detection channel, and it is shown how simple trellis-coded modulation (TCM) can be used to improve performance or increase throughput (in bits per second) without bandwidth expansion or performance loss. In fact, a modest performance gain can be achieved. Although the approach can be used with other signal constellations, the authors concentrate on signals derived from the pulse-position modulation (PPM) format by allowing overlap. Theoretical motivation for using this signal set, known as overlapping PPM (OPPM), was recently given by David and Kaplan (1984), who showed a capacity gain when overlap is introduced.

Georghiades, Costas N.



The Deuterium Test for Exo-Planet Candidates Detected Directly  

NASA Astrophysics Data System (ADS)

In the near future, direct images will be obtained for massive planets orbiting around other stars. Most likely, the first such objects detected directly will have masses near the proposed limit between brown dwarfs and planets, i.e., around 13 Jupiter masses, because the more massive planets are the brightest. Hence, it may be dubious in these first few cases, whether the detected object is a brown dwarf or a real planet. To solve this problem, one can perform the deuterium test, i.e., one can distinguish between a brown dwarf (defined as an object able to fuse all deuterium) and an real planet (defined as an object not being able to fuse any deuterium) by whether or not deuterium can be identified in a spectrum. Any such object, brown dwarf or planet, would have spectral type T, defined as those with strong methane lines in the infrared. We present a model spectrum with the CH3D line at ~ 4.5 ?m which can be obtained for such objects with CRIRES at the VLT.

Neuhäuser, Ralph; Seifahrt, Andreas; Hauschildt, Peter; Alves, Joao; Guenther, Eike


Direct and dynamic detection of HIV-1 in living cells.  


In basic and applied HIV research, reliable detection of viral components is crucial to monitor progression of infection. While it is routine to detect structural viral proteins in vitro for diagnostic purposes, it previously remained impossible to directly and dynamically visualize HIV in living cells without genetic modification of the virus. Here, we describe a novel fluorescent biosensor to dynamically trace HIV-1 morphogenesis in living cells. We generated a camelid single domain antibody that specifically binds the HIV-1 capsid protein (CA) at subnanomolar affinity and fused it to fluorescent proteins. The resulting fluorescent chromobody specifically recognizes the CA-harbouring HIV-1 Gag precursor protein in living cells and is applicable in various advanced light microscopy systems. Confocal live cell microscopy and super-resolution microscopy allowed detection and dynamic tracing of individual virion assemblies at the plasma membrane. The analysis of subcellular binding kinetics showed cytoplasmic antigen recognition and incorporation into virion assembly sites. Finally, we demonstrate the use of this new reporter in automated image analysis, providing a robust tool for cell-based HIV research. PMID:23209635

Helma, Jonas; Schmidthals, Katrin; Lux, Vanda; Nüske, Stefan; Scholz, Armin M; Kräusslich, Hans-Georg; Rothbauer, Ulrich; Leonhardt, Heinrich



A method to auto-estimate edge detection direction  

NASA Astrophysics Data System (ADS)

In machine vision measurement, the edge is a key point for fitting geometric parameter. There are two problems in the edge detection process. First, there is redundant information for the object with complex shape in the field of the view. Second, the surface of the object is full of texture which is misidentified as the edge. The texture processes similar feature to the edge and cannot be removed by filter. To solve the above problems, vision sight is proposed to get an interesting region and remove redundant information. A new algorithm based on fuzzy entropy is used to auto-estimate the edge detection direction from the pure region to mixed region in order to avoid the textures which misidentified as the edge. Comparing the algorithm with Canny, the former gets less texture points than the latter. A mask film is used as a standard to weight the validity of the algorithm. The experimental result shows that the algorithm proposed by this paper is robust and accuracy in detecting edge.

Yin, Z.; Liu, B. G.; Chen, F. D.; Liu, G. D.; Wan, F.



Detecting Tsunami Genesis and Scales Directly from Coastal GPS Stations  

NASA Astrophysics Data System (ADS)

Different from the conventional approach to tsunami warnings that rely on earthquake magnitude estimates, we have found that coastal GPS stations are able to detect continental slope displacements of faulting due to big earthquakes, and that the detected seafloor displacements are able to determine tsunami source energy and scales instantaneously. This method has successfully replicated several historical tsunamis caused by the 2004 Sumatra earthquake, the 2005 Nias earthquake, the 2010 Chilean earthquake, and the 2011 Tohoku-Oki earthquake, respectively, and has been compared favorably with the conventional seismic solutions that usually take hours or days to get through inverting seismographs (reference listed). Because many coastal GPS stations are already in operation for measuring ground motions in real time as often as once every few seconds, this study suggests a practical way of identifying tsunamigenic earthquakes for early warnings and reducing false alarms. Reference Song, Y. T., 2007: Detecting tsunami genesis and scales directly from coastal GPS stations, Geophys. Res. Lett., 34, L19602, doi:10.1029/2007GL031681. Song, Y. T., L.-L. Fu, V. Zlotnicki, C. Ji, V. Hjorleifsdottir, C.K. Shum, and Y. Yi, 2008: The role of horizontal impulses of the faulting continental slope in generating the 26 December 2004 Tsunami, Ocean Modelling, doi:10.1016/j.ocemod.2007.10.007. Song, Y. T. and S.C. Han, 2011: Satellite observations defying the long-held tsunami genesis theory, D.L. Tang (ed.), Remote Sensing of the Changing Oceans, DOI 10.1007/978-3-642-16541-2, Springer-Verlag Berlin Heidelberg. Song, Y. T., I. Fukumori, C. K. Shum, and Y. Yi, 2012: Merging tsunamis of the 2011 Tohoku-Oki earthquake detected over the open ocean, Geophys. Res. Lett., doi:10.1029/2011GL050767 (Nature Highlights, March 8, 2012).

Song, Y. Tony



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.



Direct detection of self-interacting dark matter  

NASA Astrophysics Data System (ADS)

Self-interacting dark matter offers an interesting alternative to collisionless dark matter because of its ability to preserve the large-scale success of the cold dark matter model, while seemingly solving its challenges on small scales. We present here the first study of the expected dark matter detection signal in a fully cosmological context taking into account different self-scattering models for dark matter. We demonstrate that models with constant and velocity-dependent cross-sections, which are consistent with observational constraints, lead to distinct signatures in the velocity distribution, because non-thermalized features found in the cold dark matter distribution are thermalized through particle scattering. Depending on the model, self-interaction can lead to a 10 per cent reduction of the recoil rates at high energies, corresponding to a minimum speed that can cause recoil larger than 300 km s-1, compared to the cold dark matter case. At lower energies these differences are smaller than 5 per cent for all models. The amplitude of the annual modulation signal can increase by up to 25 per cent, and the day of maximum amplitude can shift by about two weeks with respect to the cold dark matter expectation. Furthermore, the exact day of phase reversal of the modulation signal can also differ by about a week between the different models. In general, models with velocity-dependent cross-sections peaking at the typical velocities of dwarf galaxies lead only to minor changes in the detection signals, whereas allowed constant cross-section models lead to significant changes. We conclude that different self-interacting dark matter scenarios might be distinguished from each other through the details of direct detection signals. Furthermore, detailed constraints on the intrinsic properties of dark matter based on null detections should take into account the possibility of self-scattering and the resulting effects on the detector signal.

Vogelsberger, Mark; Zavala, Jesus



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.



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


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). PMID:22750343

Madhupriya, Selvaraj; Elango, Kuppanagounder P



Spectrophotometric and colorimetric determination of protein concentration.  


This unit describes spectrophotometric and colorimetric methods for measuring the concentration of a sample protein in solution. Absorbance measurement at 280 nm is used to calculate protein concentration by comparison with a standard curve or published absorptivity values for that protein. An alternate protocol uses absorbance at 205 nm to calculate the protein concentration. Both methods can be used to quantitate total protein in crude lysates and purified or partially purified protein. Use of a spectrofluorometer or a filter fluorometer to measure the intrinsic fluorescence emission of a sample solution is also described. The measurement is compared with the emissions from standard solutions to determine the concentration of purified protein. The Bradford colorimetric method, based upon binding of the dye Coomassie brilliant blue to an unknown protein, is also presented, as is the Lowry method, which measures colorimetric reaction of tyrosyl residues in an unknown. PMID:18265371

Simonian, Michael H; Smith, John A



Comparison of colorimetric and membrane introduction mass spectrometry techniques for chloramine analysis.  


Three methods for the determination of chloramines in water were compared using pH-buffered nanopure water and natural organic matter (NOM) solutions. We investigated whether the N,N-diethyl-p-phenylenediamine (DPD) colorimetric method and/or an adapted indophenol method (Hach MonochlorF) are suitable for determining the concentration of monochloramine in drinking water. Membrane introduction mass spectrometry (MIMS) was used as a reference analysis method to determine the different chloramine species in water. All methods measured monochloramine accurately in Nanopure water, but the DPD colorimetric method measured higher residuals (inorganic and organic chloramines) than MonochlorF or MIMS when in the presence of NOM due to organic chloramines. The indophenol method (MonochlorF) accurately detected only monochloramine and not other chloramine forms. Overall, the monochloramine concentration measured by MonochlorF was comparable with the MIMS results. A combined chlorine residual approach by the DPD colorimetric method does not differentiate between monochloramine and organic chloramines. Therefore, DPD colorimetric methods can overestimate disinfection efficacy in chloraminated water systems because of interference from organic chloramines that have no or poor bactericidal ability. Compared with the DPD colorimetric method, MonochlorF is a better choice for chloraminated water systems. PMID:17544050

Lee, Wontae; Westerhoff, Paul; Yang, Xin; Shang, Chii



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


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



Astrophysical uncertainties of dark matter direct detection experiments  

SciTech Connect

The effects of astrophysical uncertainties on the exclusion limits at dark matter direct detection experiments are investigated for three scenarios: elastic, momentum dependent, and inelastically scattering dark matter. We find that varying the dark matter galactic escape velocity and the Sun's circular velocity can lead to significant variations in the exclusion limits for light (< or approx. 10 GeV) elastic and inelastic scattering dark matter. We also calculate the limits using 100 velocity distributions extracted from the Via Lactea II and GHALO N-body simulations and find that a Maxwell-Boltzmann distribution with the same astrophysical parameters generally sets less constraining limits. The elastic and momentum dependent limits remain robust for masses > or approx. 50 GeV under variations of the astrophysical parameters and the form of the velocity distribution.

McCabe, Christopher [Rudolf Peierls Centre for Theoretical Physics, University of Oxford, 1 Keble Road, Oxford OX1 3NP (United Kingdom)



Halo independent comparison of direct dark matter detection data  

NASA Astrophysics Data System (ADS)

We extend the halo-independent method of Fox, Liu, and Weiner to include energy resolution and efficiency with arbitrary energy dependence, making it more suitable for experiments to use in presenting their results. Then we compare measurements and upper limits on the direct detection of low mass ( ~ 10 GeV) weakly interacting massive particles with spin-independent interactions, including the upper limit on the annual modulation amplitude from the CDMS collaboration. We find that isospin-symmetric couplings are severely constrained both by XENON100 and CDMS bounds, and that isospin-violating couplings are still possible at the lowest energies, while the tension of the higher energy CoGeNT bins with the CDMS modulation constraint remains. We find the CRESST-II signal is not compatible with the modulation signals of DAMA and CoGeNT.

Gondolo, Paolo; Gelmini, Graciela B.



Quantifying astrophysical uncertainties on dark matter direct detection results  

NASA Astrophysics Data System (ADS)

We attempt to estimate the uncertainty in the constraints on the spin independent dark matter-nucleon cross section due to our lack of knowledge of the dark matter phase space in the galaxy. We fit the density of dark matter before investigating the possible solutions of the Jeans equation compatible with those fits in order to understand what velocity dispersions we might expect at the solar radius. We take into account the possibility of non-Maxwellian velocity distributions and the possible presence of a dark disk. Combining all these effects, we still find that the uncertainty in the interpretation of direct detection experiments for high (>100 GeV) mass dark matter candidates is less than an order of magnitude in cross section.

Fairbairn, Malcolm; Douce, Tom; Swift, Jace



Regenerating WIMPs in the light of direct and indirect detection  

NASA Astrophysics Data System (ADS)

There are several ways to explain the dark matter relic density other than by the ordinary freeze-out scenario. For example, the freeze-in mechanism may constitute an alternative for generating the correct relic density for dark matter candidates whose predicted freeze-out abundance is too low due to a large total annihilation cross section. Here we show that although such a mechanism could explain why a dark matter candidate has the correct relic density, some candidates may still be ruled out because they would lead to a large gamma-ray flux in dwarf spheroidal galaxies or a large elastic scattering rate in direct detection experiments. To investigate this scenario we examine neutralino dark matter in the MSSM. However, our conclusions can be generalized to other types of annihilating DM candidates with a low relic density in the freeze-out scenario, but which have their relic densities generated by some other mechanism.

Williams, A. J.; Bœhm, C.; West, S. M.; Albornoz Vásquez, D.



Consequences of statistical sense determination for WIMP directional detection  

SciTech Connect

We study the consequences of limited recoil sense reconstruction on the number of events required to reject isotropy and detect a WIMP signal using a directional detector. For a constant probability of determining the sense correctly, 3-d readout and zero background, we find that as the probability is decreased from 1.0 to 0.75 the number of events required increases by a factor of a few. As the probability is decreased further the number of events increases sharply, and isotropy can be rejected more easily by discarding the sense information and using axial statistics. This however requires an order of magnitude more events than vectorial data with perfect sense determination. We also consider energy dependent probabilities of correctly measuring the sense. Our main finding is that correctly determining the sense of the abundant, but less anisotropic, low energy recoils is most important.

Green, Anne M.; Morgan, Ben [School of Physics and Astronomy, University of Nottingham, University Park, Nottingham, NG7 2RD (United Kingdom); Department of Physics, University of Warwick, Coventry, CV4 7AL (United Kingdom)



Colorimetric and fluorometric dual-readout sensor for lysozyme.  


A novel, highly sensitive and selective dual-readout sensor (colorimetric and fluorometric) for the detection of lysozyme was proposed. The fluorescence of triazolylcoumarin molecules was quenched by Au nanoparticles (AuNPs) initially through the fluorescence resonance energy transfer (FRET), after the addition of lysozyme, the stronger binding of lysozyme onto the surfaces of AuNPs made triazolylcoumarin molecules remove from the AuNPs surface and led to the recovery of the fluorescence of triazolylcoumarin molecules, and accompanied by the discernable color change of the solution from red to purple. The lowest detectable concentration for lysozyme was 50 ng mL(-1) by the naked eye, and the limit of detection (LOD) was 23 ng mL(-1) by fluorescence measurements. In addition, satisfactory results for lysozyme detection in hen egg white were confirmed in the study. Moreover, the presented sensor provides a reliable option to determine lysozyme with high sensitivity and selectivity. PMID:23978821

Zheng, Hanye; Qiu, Suyan; Xu, Kefeng; Luo, Linguang; Song, Yibiao; Lin, Zhenyu; Guo, Longhua; Qiu, Bin; Chen, Guonan



13C Direct detected experiments: Optimization for paramagnetic signals  

NASA Astrophysics Data System (ADS)

To optimize 13C direct detected experiments for the observation of signals close to a paramagnetic center, we have assessed the sensitivity of different sequences based on CO Cali coherence transfer. Features of CACO experiments were tested for Calbindin D9k, in which one of the two native Ca2+ ions is replaced by the paramagnetic Ce3+ ion. We have studied the comparison of single vs multiple quantum coherence transfer evolution as well as the influence of in-phase vs anti-phase detection of 13CO signals and finally the comparison of a coherence transfer step based on a CyO in plane with respect to a Cyali in plane. The acquisition of the anti-phase component of the signal, accomplished by the removal of the last refocusing steps, allowed the identification of some signals unobserved with other pathways. The structural dependency of paramagnetism-induced nuclear relaxation is such that the identification of the most suitable coherence transfer pathway is not known “a priori” but it is driven by the relative proximity of Cali and CO to the paramagnetic center.

Bertini, Ivano; Jiménez, Beatriz; Piccioli, Mario



Subcarrier multiplexing with dispersion reduction and direct detection  


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)



Direct Detection of Bacterial Protein Secretion Using Whole Colony Proteomics*  

PubMed Central

Bacteria use a variety of secretion systems to transport proteins beyond their cell membrane to interact with their environment. For bacterial pathogens, these systems are key virulence determinants that transport bacterial proteins into host cells. Genetic screens to identify bacterial genes required for export have relied on enzymatic or fluorescent reporters fused to known substrates to monitor secretion. However, they cannot be used in analysis of all secretion systems, limiting the implementation across bacteria. Here, we introduce the first application of a modified form of whole colony MALDI-TOF MS to directly detect protein secretion from intact bacterial colonies. We show that this method is able to specifically monitor the ESX-1 system protein secretion system, a major virulence determinant in both mycobacterial and Gram-positive pathogens that is refractory to reporter analysis. We validate the use of this technology as a high throughput screening tool by identifying an ESAT-6 system 1-deficient mutant from a Mycobacterium marinum transposon insertion library. Furthermore, we also demonstrate detection of secreted proteins of the prevalent type III secretion system from the Gram-negative pathogen, Pseudomonas aeruginosa. This method will be broadly applicable to study other bacterial protein export systems and for the identification of compounds that inhibit bacterial protein secretion.

Champion, Matthew M.; Williams, Emily A.; Kennedy, George M.; DiGiuseppe Champion, Patricia A.



Analysis of the standard colorimetric observer  

NASA Astrophysics Data System (ADS)

It is known that there are tow color matching functions that defined to the two standard colorimetric observers standard colorimetric observer. The fundamental different between these standard observers is due to the visual field, because in each color matching experiment was used a different size of visual field. The purpose of this work is to realize a documental analysis about latest results in this topics. Most of the recent publications explain some differences among the color perception properties by investigating the influence of: size of visual field, peripheral visual field and the macular pigment.

Ibanez-Porras, Maritza; Carranza-G., J.



The intermediate size direct detection detector for electron microscopy  

NASA Astrophysics Data System (ADS)

In a longstanding effort to overcome limits of film and the charge coupled device (CCD) systems in electron microscopy, we have developed a radiation-tolerant system that can withstand direct electron bombardment. A prototype Direct Detection Device (DDD) detector based on an Active Pixel Sensor (APS) has delivered unprecedented performance with an excellent signal-to-noise ratio (approximately 5/1 for a single incident electron in the range of 200-400 keV) and a very high spatial resolution. This intermediate size prototype features a 512×550 pixel format of 5?m pitch. The detector response to uniform beam illumination and to single electron hits is reported. Radiation tolerance with high-energy electron exposure is also impressive, especially with cooling to -15 °C. Stable performance has been demonstrated, even after a total dose of 3.3×106 electrons/pixel. The characteristics of this new detector have exciting implications for transmission electron microscopy, especially for cryo-EM as applied to biological macromolecules.

Jin, Liang; Milazzo, Anna-Clare; Kleinfelder, Stuart; Li, Shengdong; Leblanc, Philippe; Duttweiler, Fred; Bouwer, James C.; Peltier, Steve T.; Ellisman, Mark; Xuong, Nguyen-Huu



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



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



A Colorimetric Assay for Quantification of Defective Interfering Particles of Respiratory Syncytial Virus  

Microsoft Academic Search

SUMMARY A colorimetric assay for defective interfering (DI) particles of respiratory syncytial (RS) virus was developed. This quantitative biological assay is based on neutral red dye uptake by DI particle-protected cells that survive standard virus challenge. This assay was more sensitive than the reduction of infectious yield (RIY) assay and was capable of detecting 1 x 104 to 2 x




Colorimetric coupled enzyme assay for ?-glutamyltransferase activity using glutathione as substrate  

Microsoft Academic Search

A colorimetric coupled enzyme assay for the determination of ?-glutamyltransferase (GGT) activity using glutathione as substrate is described. The cysteine released from glutathione upon sequential action of GGT and leucine aminopeptidase is spectrophotometrically detected through its reaction with ninhydrin at 100 °C in acidic conditions. The method was applied to the determination of the activity of both bovine kidney and

Antonella Del Corso; Mario Cappiello; Francesca Buono; Roberta Moschini; Aldo Paolicchi; Umberto Mura



A Colorimetric Assay for Estimation of Polyethylene Glycol and Polyethylene Glycolated Protein Using Ammonium Ferrothiocyanate  

Microsoft Academic Search

A colorimetric method for quantitative assay of polyethylene glycol (PEG) described here is based on partitioning of a chromophore present in ammonium ferrothiocyanate reagent from an aqueous to a chloroform phase in the presence of PEG. The method is simple, reproducible, and can detect PEG in amounts as low as 5 ?g. It gives a linear response over a range

Alo Nag; Gargi Mitra; Prahlad C. Ghosh



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




Complementarity of direct dark matter detection and indirect detection through gamma rays  

SciTech Connect

We show, by using an extensive sample of viable supersymmetric models as templates, that indirect detection of dark matter through gamma rays may have a large potential for identifying the nature of dark matter. This is, in particular, true also for models that give too weak dark matter-nucleon scattering cross sections to be probed by present and planned direct detection experiments. Also models with a mass scale too high to be accessible at CERN's LHC accelerator may show up in next-generation imaging Cherenkov telescope arrays. Based on our findings, we therefore suggest to view indirect searches as genuine particle physics experiments, complementing other strategies to probe so far unknown regions in the parameter space of e.g. supersymmetric models, and propose a new approach that would make use of telescopes dedicated for dark matter searches. As a concrete example for the potential of such an approach, we consider an array of imaging air Cherenkov telescopes, the Dark Matter Array (DMA), and show that such an experiment could extend present-day limits by several orders of magnitude, reaching a large class of models that would remain undetected in both direct detection experiments and searches at the LHC. In addition, in a sizable part of the parameter space, signals from more than one type of dark matter detection experiment would be possible, something that may eventually be necessary in order to identify the dark matter candidate.

Bergstroem, Lars; Bringmann, Torsten; Edsjoe, Joakim [Oskar Klein Centre for Cosmoparticle Physics, Department of Physics, Stockholm University, AlbaNova, SE-106 91 Stockholm (Sweden); II. Institute for Theoretical Physics, University of Hamburg, Luruper Chausse 149, D-22761 Hamburg (Germany); Oskar Klein Centre for Cosmoparticle Physics, Department of Physics, Stockholm University, AlbaNova, SE-106 91 Stockholm (Sweden)



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.



Colorimetric Determination of Phenols in Water Samples  

Microsoft Academic Search

A colorimetric method for determination of phenols in water has been developed. The method, which is a modification of Liebermann's reaction, uses resorcinol as a chromogenic agent. The developed method is more sensitive, and the difficulties encountered in the widely used 4-aminoantipyrine method have been avoided. Application of both the proposed and 4-aminoantipyrine methods to the analysis of natural and

Sayed M. Hassan; Fatma B. Salem; Nagat Abd El-salam



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.



Rapid Colorimetric Assay of 5-Aminosalicylate  

Microsoft Academic Search

The drug 5-aminosalicylate is an anti-inflammatory agent used in the treatment of ulcerative colitis. Recent studies have suggested that the amino substituent plays an important role in both the toxicity and the therapeutic effect of the drug. In view of these findings, a rapid and convenient method of analysis would be useful for monitoring selected patients receiving 5-aminosalicylate. A colorimetric

Timothy J. Smith; Mark A. Tucker



Colorimetric determination of tobramycin in parenteral solutions.  


A colorimetric method based on a reaction between tobramycin and alkaline copper sulphate solution has been proposed to quantify tobramycin in injections. The excipients present and normal saline did not interfere with the assay procedure. A tobramycin sample which was decomposed using either sulphuric acid or sodium hydroxide solution indicated fairly good stability on both sides of the pH scale. PMID:3209627

Das Gupta, V



A Gait Based Approach to Detect Directional Bias of Four-Legged Robots' Direct Walking Utilizing Acceleration Sensors  

Microsoft Academic Search

In this paper, we propose an effective approach to detect the directional bias of walking four-legged robots. We found that\\u000a light weight four-legged robots tend to have unstable directional bias even when walking on flat ground, thus this approach\\u000a is designed to be able to dynamically and continuously detect the directional bias. By observing and analyzing data from acceleration\\u000a sensors

Ding-jie Huang; Wei-chung Teng



Direct detection of supersymmetric particles in neutrino telescopes  

SciTech Connect

In supersymmetric theories where the lightest supersymmetric particle is the gravitino the next to lightest supersymmetric particle is typically a long-lived charged slepton. In this paper, following our earlier proposal [I. Albuquerque, G. Burdman, and Z. Chacko, Phys. Rev. Lett. 92, 221802 (2004).], we perform a detailed study of the production of pairs of these particles induced by the interactions of high energy cosmic neutrinos with nucleons in the Earth, their propagation through the Earth, and finally their detection in neutrino telescopes. We investigate the charged slepton energy loss in detail and establish that the relatively small cross section for the production of supersymmetric particles is partially compensated for by the very long range of these heavy particles. The signal, consisting of two parallel charged tracks emerging from the Earth, is characterized by a track separation of a few hundred meters. We perform a careful analysis of the main background, coming from direct di-muon production, and show that it can be separated from the signal due to its characteristically smaller track separation. We conclude that neutrino telescopes will complement collider searches in the determination of the supersymmetry breaking scale, and may even provide the first evidence for supersymmetry at the weak scale.

Albuquerque, Ivone F. M.; Burdman, Gustavo; Chacko, Z. [Instituto de Fisica, Universidade de Sao Paulo, Sao Paulo (Brazil); Department of Physics, University of Arizona, Tucson, Arizona 85721 (United States)



Detection of biological threats. A challenge for directed molecular evolution.  


The probe technique originated from early attempts of Anton van Leeuwenhoek to contrast microorganisms under the microscope using plant juices, successful staining of tubercle bacilli with synthetic dyes by Paul Ehrlich and discovery of a stain for differentiation of gram-positive and gram-negative bacteria by Hans Christian Gram. The technique relies on the principle that pathogens have unique structural features, which can be recognized by specifically labeled organic molecules. A hundred years of extensive screening efforts led to discovery of a limited assortment of organic probes that are used for identification and differentiation of bacteria. A new challenge--continuous monitoring of biological threats--requires long lasting molecular probes capable of tight specific binding of pathogens in unfavorable conditions. To respond to the challenge, probe technology is being revolutionized by utilizing methods of combinatorial chemistry, phage display and directed molecular evolution. This review describes how molecular evolution methods are applied for development of peptide, antibody and phage probes, and summarizes the author's own data on development of landscape phage probes against Salmonella typhimurium. The performance of the probes in detection of Salmonella is illustrated by a precipitation test, enzyme-linked immunosorbent assay (ELISA), fluorescence-activated cell sorting (FACS) and fluorescent, optical and electron microscopy. PMID:15234514

Petrenko, Valery A; Sorokulova, Iryna B



Applications of Direct Detection Device in Transmission Electron Microscopy  

PubMed Central

A prototype Direct Detection Device (DDD) camera system has shown great promise in improving both the spatial resolution and the signal to noise ratio for electron microscopy at 120–400 keV beam energies (Xuong, et al., 2007. Methods in Cell Biology, 79, 721–739). Without the need for a resolution-limiting scintillation screen as in the charge coupled device (CCD), the DDD camera can outperform CCD based systems in terms of spatial resolution, due to its small pixel size (5 ?m). In this paper, the modulation transfer function (MTF) of the DDD prototype is measured and compared with the specifications of commercial scientific CCD camera systems. Combining the fast speed of the DDD with image mosaic techniques, fast wide-area imaging is now possible. In this paper, the first large area mosaic image and the first tomography dataset from the DDD camera are presented, along with an image processing algorithm to correct the specimen drift utilizing the fast readout of the DDD system.

Jin, Liang; Milazzo, Anna-Clare; Kleinfelder, Stuart; Li, Shengdong; Leblanc, Philippe; Duttweiler, Fred; Bouwer, James C.; Peltier, Steven T.; Ellisman, Mark H.; Xuong, Nguyen-Huu



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



Using the Griess colorimetric nitrite assay for measuring aliphatic ?-nitroalcohols  

PubMed Central

Our recent studies suggest that aliphatic ?-nitroalcohols (BNAs) may represent a useful class of compounds for topical therapeutic corneoscleral cross-linking agents. Thus, this study was undertaken in order to standardize a simple method for nitroalcohol quantitation based on a denitration step followed by colorimetric Griess nitrite assay. Conditions necessary for denitration included a pH of 7-9 and heating for 1 hour at 100°C. Standard curves for two mono-nitroalcohols (2-nitroethanol and 2-nitro-1-propanol), a nitro-diol (2-methyl-2-nitro-1,3-propanediol), and a nitro-triol (2-hydroxymethyl-2-nitro-1,3-propanediol) showed excellent linearity in the 100-500 M range with absorbance values <1.0 and R2 values >0.98. The lower limit of detection was ~20 M. Recovery from tissue homogenates (10mg/mL wet weight) of rabbit cornea and sclera as well as solutions of gelatin B (1mg/mL) ranged from 89-103% for scleral tissue, 68-106% for corneal tissue, and 90-99% for gelatin B. The Griess colorimetric nitrite assay can be successfully used for the quantitative determination of BNAs and is simpler to use than conventional chromatographic techniques.

Wen, Quan; Paik, David C.



Interface engineering catalytic graphene for smart colorimetric biosensing.  


Herein a hybrid catalyst consisting of "naked" Au-NPs in situ grown on graphene sheets is engineered, which exhibits a synergetic effect in mimicking peroxidase at its interface, although free Au-NPs or graphene alone has very little activity. What is more, one of the unique features of our synergetic catalyst is that its interface can be reversibly switched from "inactive" to "active" upon treatment with different ssDNA species in solution, thus providing a powerful and versatile basis for designing graphene/DNA-based label-free colorimetric biosensors. Compared with other signal transduction modes in traditional graphene/aptamer-based systems, our novel signaling strategy not only avoids any labeling or modification procedures but also reduces the background signal due to the "off-on" switching mode during the sensing. Furthermore, this facile and general approach can be applicable to the other extended graphene/aptamer-based systems for colorimetric detection of a wide range of analytes. We envision that the tunable graphene-based smart interface could find potential applications in the development of biocatalysis, bioassays, and smart material devices in the future. PMID:22443302

Liu, Meng; Zhao, Huimin; Chen, Shuo; Yu, Hongtao; Quan, Xie



Solvent colorimetric paper-based polydiacetylene sensors from diacetylene lipids.  


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



A novel colorimetric immunoassay utilizing the peroxidase mimicking activity of magnetic nanoparticles.  


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. PMID:23665902

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



Colorimetric sensor array for soft drink analysis.  


Fourteen commercial soft drinks have been analyzed using colorimetric sensor arrays made from a set of 25 chemically responsive dyes printed on a hydrophobic membrane. Digital imaging of the dye array before and after immersion provides a color change profile as a unique fingerprint for each specific analyte. The digital data library generated was analyzed with statistical and chemometric methods, including principal component analysis (PCA) and hierarchical clustering analysis (HCA). Facile identification of all of the soft drinks was readily achieved using comparison of the color change profiles or a PCA score plot. Using a HCA dendrogram, the misclassification rate was <2%, and even very similar sodas were easily differentiated. In addition, the monitoring of soft drinks as they degas or upon dilution also proved to be possible. This work demonstrates the potential of our colorimetric sensor array technology for quality assurance/control applications of sodas and perhaps other beverages as well. PMID:17227048

Zhang, Chen; Suslick, Kenneth S



Direct carbon detection in paramagnetic metalloproteins to further exploit pseudocontact shift restraints.  


Direct detection heteronuclear NMR allows us to drastically reduce paramagnetic contributions to the line width as compared to 1H detection. As an example, a calcium binding protein (human oncomodulin), in which one of the calcium ions was selectively substituted with Tb3+, is used. Through a variety of 13C direct detection NMR experiments, resonances were detected as close as 5.5 A from the metal ion. Pseudocontact shifts measured through 13C direct detection experiments provide structural constraints in regions of the protein where 1H resonances are broadened beyond detection through Curie relaxation (up to 16 A from the paramagnetic center). PMID:15327280

Babini, Elena; Bertini, Ivano; Capozzi, Francesco; Felli, Isabella C; Lelli, Moreno; Luchinat, Claudio



Colorimetric determination of phenols in water samples  

SciTech Connect

A colorimetric method for determination of phenols in water has been developed. The method, which is a modification of Liebermann's reaction, uses resorcinol as a chromogenic agent. The developed method is more sensitive, and the difficulties encountered in the widely used 4-aminoantipyrine method have been avoided. Application of both the proposed and 4-aminoantipyrine methods to the analysis of natural and tap water samples are presented.

Hassan, S.M.; Salem, F.B.; El-Salam, N.A.



Improving colorimetric assays through protein enzyme-assisted gold nanoparticle amplification.  


The discovery of the DNA-mediated assembly of gold nanoparticles was a great moment in the history of science; this understanding and chemical control enabled the rational design of functional nanomaterials as novel probes in biodetection. In contrast with conventional probes such as organic dyes, gold nanoparticles exhibit high photostability and unique size-dependent optical properties. Because of their high extinction coefficients and strong distance dependent optical properties, these nanoparticles have emerged over the past decade as a promising platform for rapid, highly sensitive colorimetric assays that allow for the visual detection of low concentrations of metal ions, small molecules, and biomacromolecules. These discoveries have deepened our knowledge of biological phenomena and facilitated the development of many new diagnostic and therapeutic tools. Despite these many advances and continued research efforts, current nanoparticle-based colorimetric detection systems still suffer from several drawbacks, such as limited sensitivity and selectivity. This Account describes the recent development of colorimetric assays based on protein enzyme-assisted gold nanoparticle amplification. The benefits of such detection systems include significantly improved detection sensitivity and selectivity. First, we discuss the general design of enzyme-modified nanoparticle systems in colorimetric assays. We show that a quantitative understanding of the unique properties of different enzymes is paramount for effective biological assays. We then examine the assays for nucleic acid detection based on different types of enzymes, including endonucleases, ligases, and polymerases. For each of these assays, we identify the underlying principles that contribute to the enhanced detection capability of nanoparticle systems and illustrate them with selected examples. Furthermore, we demonstrate that the combination of gold nanoparticles and specific enzymes can probe enzyme dynamics and function with high specificity, offering substantial advantages in both sensitivity and specificity over conventional detection methods. The screening of nuclease, methyltransferase, protease, and kinase activities can be colorimetrically performed in a straightforward manner. Finally, we discuss examples of colorimetric assays for metal ions and small molecules that constitute important advances toward visual monitoring of enzyme catalytic functions and gene expression. Although these enzyme-assisted assay methods hold great promise for myriad applications in biomedicine and bioimaging, the application of the described techniques in vivo faces formidable challenges. In addition, researchers do not fully understand the interactions of gold nanoparticles with enzyme molecules. This understanding will require the development of new techniques to probe enzyme substrate dynamics at the particle interface with higher spatial resolution and chemical specificity. PMID:22786666

Xie, Xiaoji; Xu, Wei; Liu, Xiaogang



Transoceanic bird migration: Evidence for detection of wind direction  

Microsoft Academic Search

Further analysis of radar tracks of migrating birds over the Atlantic Ocean (Larkin et al., 1979) indicates that birds sometimes fly at lower air speeds when winds are in the direction of flight than in crosswinds or head winds. The birds are able to estimate wind direction over open ocean by a mechanism which is presently open to speculation.

Ronald P. Larkin



Bed bug detection: current technologies and future directions.  


Technologies to detect bed bugs have not kept pace with their global resurgence. Early detection is critical to prevent infestations from spreading. Detection based exclusively on bites is inadequate, because reactions to insect bites are non-specific and often misdiagnosed. Visual inspections are commonly used and depend on identifying live bugs, exuviae, or fecal droplets. Visual inspections are inexpensive, but they are time-consuming and unreliable when only a few bugs are present. Use of a dog to detect bed bugs is gaining in popularity, but it can be expensive, may unintentionally advertise a bed bug problem, and is not foolproof. Passive monitors mimic natural harborages; they are discreet and typically use an adhesive to trap bugs. Active monitors generate carbon dioxide, heat, a pheromone, or a combination to attract bed bugs to a trap. New technologies using DNA analysis, mass spectrometry, and electronic noses are innovative but impractical and expensive for widespread use. PMID:23553226

Vaidyanathan, Rajeev; Feldlaufer, Mark F



A System for Multiplexed Direct Electrical Detection of DNA Synthesis.  


An electronic system for the multiplexed detection of DNA polymerization is designed and characterized. DNA polymerization is detected by the measurement of small transient currents arising from ion diffusion during polymerization. A transimpedance amplifier is used to detect these small currents; we implemented a twenty-four channel recording system on a single printed circuit board. Various contributions to the input-referred current noise are analyzed and characterized, as it limits the minimum detectable current and thus the biological limit of detection. We obtained 8.5 pA RMS mean noise current (averaged over all 24 channels) over the recording bandwidth (DC to 2 kHz). With digital filtering, the input-referred current noise of the acquisition system is reduced to 2.4 pA, which is much lower than the biological noise. Electrical crosstalk between channels is measured, and a model for the crosstalk is presented. Minimizing the crosstalk is critical because it can lead to erroneous microarray data. With proper precautions, crosstalk is reduced to a negligible value (less than 1.4%). Using a micro-fabricated array of 24 gold electrodes, we demonstrated system functionality by detecting the presence of a target DNA oligonucleotide which hybridized onto its corresponding target. PMID:19183700

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



Detecting and comparing the direction of gene-frequency gradients  

Microsoft Academic Search

Directional gene flow between genetically differentiated populations leads to parallel gene-frequency gradients at various\\u000a loci; processes of differential selection are not expected to result in equally oriented patterns of gene frequencies. Therefore,\\u000a inferences on the mechanisms maintaining genetic diversity can be drawn by comparing the directions of clines at different\\u000a loci. An approach to quantifying the orientation of a cline

Guido Barbujani; L. Borsari



Passive colorimetric dosimeter tubes for ammonia, carbon monoxide, carbon dioxide, hydrogen sulfide, nitrogen dioxide, and sulfur dioxide  

SciTech Connect

Colorimetric, stain length, personal dosimeters operating by gas diffusion have been developed to determine worker exposure for up to an 8-h period for several inorganic airborne contaminants in the range of their threshold limit values. Length of stain, colorimetric dosimeters have been made for the detection of ammonia (NH/sub 3/), carbon monoxide (CO), carbon dioxide (CO/sub 2/), hydrogen sulfide (H/sub 2/S), nitrogen dioxide (NO/sub 2/), and sulfur dioxide (SO/sub 2/) in air. For each gas detection system, the sampler depends on the transfer of the gas by diffusion into a glass tube containing a colorimetric length of stain indicator. The stain length developed in a given period of time is compared to a calibration chart to determine, on the spot, the average gas concentration to which the dosimeter has been exposed. These dosimeters are known by the trade name Vapor Gard.

McKee, E.S.; Pritts, I.M.



Passive colorimetric dosimeter tubes for ammonia, carbon monoxide, carbon dioxide, hydrogen sulfide, nitrogen dioxide and sulfur dioxide  

SciTech Connect

Colorimetric, stain length, personal dosimeters operating by gas diffusion have been developed to determine worker exposure for up to an eight-hour period for several inorganic airborne contaminants in the range of their Threshold Limit Values. Length of stain, colorimetric dosimeters have been made for the detection of ammonia (NH/sub 3/), carbon monoxide (CO), carbon dioxide (CO/sub 2/), hydrogen sulfide (H/sub 2/S), nitrogen dioxide (NO/sub 2/), and sulfur dioxide (SO/sub 2/) in air. For each gas detection system, the sampler depends on the transfer of the gas by diffusion into a glass tube containing a colorimetric length of stain indicator. The stain length developed in a given period of time is compared to a calibration chart to determine, on the spot, the average gas concentration to which the dosimeter has been exposed. These dosimeters are known by the trade name Vapor Gard.

McConnaughey, P.W.; McKee, E.S.; Pritts, I.M.



Colorimetric and ultrasensitive bioassay based on a dual-amplification system using aptamer and DNAzyme.  


Rapid detection of ultralow amount of biomarkers in a biologically complex mixture remains a major challenge. Herein, we report a novel aptamer-based protein detection assay that integrates two signal amplification processes, namely, polymerase-mediated rolling-circle amplification (RCA) and DNA enzyme-catalyzed colorimetric reaction. The target biomarker is captured in a sandwich assay by primary aptamer-functionalized microbeads (MBs) and a secondary aptamer that is connected to a RCA primer/circular template complex. RCA reaction, which amplifies the single biomarker binding events by a factor of hundreds to thousands (the first amplification) produces a long DNA molecule containing multiple DNAzyme units. The peroxidase-like DNAzyme catalyzes the oxidation of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (the second amplification), which generates a blue-green colorimetric signal. This new biosensing platform permits the ultrasensitive, label-free, colorimetric detection of biomarker in real time. Using platelet-derived growth factor B-chain (PDGF-BB) as a model system, we demonstrated that our assay can detect a protein marker specifically in a serum-containing medium, at a concentration as low as 0.2 pg/mL in ?2 h, which rivals traditional assays such as ELISA. We anticipate this simple methodology for biomarker detection can find utility in point-of-care applications. PMID:22533853

Tang, Longhua; Liu, Yang; Ali, Md Monsur; Kang, Dong Ku; Zhao, Weian; Li, Jinghong



Storage arthropod pest detection - current status and future directions  

Microsoft Academic Search

A key element of a grain storage integrated pest management (IPM) system is the ability to monitor for the presence of arthropod pests and to reliably detect these, as early as possible, at low population densities. There has been considerable progress in the development of traps for monitoring storage insects and mites and progress has also been made in the

M. E. Wakefield


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



Detection of viruses in avian faeces by direct electron microscopy  

Microsoft Academic Search

A total of 151 specimens of turkey and chicken faeces and intestinal contents were examined for the presence of viruses by electron microscopy. Viruses were detected in 48 of these specimens (32%). The most frequently observed viruses were rotaviruses and enterovirus?like particles. Rotavirus infection was associated with outbreaks of diarrhoea in turkeys, but symptomless rotavirus infection was seen in broiler

M. S. McNulty; W. L. Curran; D. Todd; J. B. McFerran



Calibration-Free Eye Gaze Direction Detection with Gaussian Processes  

Microsoft Academic Search

In this paper we present a solution for eye gaze detection from a wireless head mounted camera designed for children aged between 6 months and 18 months. Due to the constraints of working with very young children, the system does not seek to be as accurate as other state-of-the-art eye trackers, however it requires no calibration process from the wearer.

Basilio Noris; Karim Benmachiche; Aude Billard



Direct Detection of RDX Vapor Using a Conjugated Polymer Network.  


1,3,5-Trinitroperhydro-1,3,5-triazine (RDX) is a principal component of plastic explosives used in acts of terrorism and within improvised explosive devices, among others. Approaches to detect RDX compatible with remote, "stand-off" sampling that do not require preconcentration strategies, such as the swabs commonly employed in airports, will benefit military and civilian security. Such detection remains a significant challenge because RDX is 10(3) less volatile than 1,3,5-trinitrotoluene (TNT), corresponding to a parts-per-trillion vapor pressure under ambient conditions. Therefore, while fluorescence quenching of conjugated polymers is sufficiently sensitive to detect TNT vapors, RDX vapor detection is undemonstrated. Here we report a cross-linked phenylene vinylene polymer network whose fluorescence is quenched by trace amounts of RDX introduced from solution or the vapor phase. Fluorescence quenching is reduced, but remains significant, when partially degraded RDX is employed, suggesting that the polymer responds to RDX itself. The polymer network also responds to TNT and PETN similarly introduced from solution or the vapor phase. Pure solvents, volatile amines, and the outgassed vapors from lipstick or sunscreen do not quench polymer fluorescence. The established success of TNT sensors based on fluorescence quenching makes this a material of interest for real-world explosive sensors and will motivate further interest in cross-linked polymers and framework materials for sensing applications. PMID:23641956

Gopalakrishnan, Deepti; Dichtel, William R



Direct Gray-Scale Minutiae Detection In Fingerprints  

Microsoft Academic Search

Most automatic systems for fingerprint comparison are based on minutiae matching. Minutiae are essentially terminations and bifurcations of the ridge lines that constitute a fingerprint pattern. Automatic minutiae detection is an extremely critical process, especially in low-quality fingerprints where noise and contrast deficiency can originate pixel configurations similar to minutiae or hide real minutiae. Several approaches have been proposed in

Dario Maio; Davide Maltoni



Future Direct Spectroscopic Detection of Hot Jupiters with IGRINS  

NASA Astrophysics Data System (ADS)

With about 700 confirmed extrasolar planets, it is time to move beyond discovery and towards characterization. Perhaps the most basic parameter of an extrasolar planet is its mass; however, this is very difficult to determine if the planet does not transit the star. The radial velocity technique, still the most fruitful method of discovering planets in the solar neighborhood, can only determine a minimum planet mass. We investigate a method using the near-future IGRINS near infrared spectrograph to detect the orbital motion of the planet itself. We simulate several observations of a star with an orbiting planet, and search for the spectral signature of the planet by cross-correlating against planet model spectra. A detection appears as a strong peak in the cross-correlation function, and gives the radial velocity of the planet at the time of observation. This, combined with the motion of the star from traditional radial velocity planet search programs, can determine the actual planet mass. We find that the IGRINS instrument can detect the spectral signature from large planets on very close orbits (so-called Hot Jupiters), and that the detections can provide tight constraints on the true planet mass.

Gullikson, Kevin; Endl, Mike



Direct PCR detection of Escherichia coli O157:H7  

Microsoft Academic Search

K. A. F O D E - V A U G H A N , J. S. M A K I , J. A. B E N S O N A N D M. L. P. C O L L I N S. 2003. Aims: This paper reports a simple, rapid approach for the detection of Shiga toxin (Stx)-producing Escherichia

K. A. Fode-Vaughan; J. S. Maki; J. A. Benson; M. L. P. Collins



New Completeness Methods for Estimating Exoplanet Discoveries by Direct Detection  

Microsoft Academic Search

We report on new methods for evaluating realistic observing programs that search stars for planets by direct imaging, where observations are selected from an optimized star list and stars can be observed multiple times. We show how these methods bring critical insight into the design of the mission and its instruments. These methods provide an estimate of the outcome of

Robert A. Brown; Rémi Soummer



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



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


Rapid Detection and Identification of Respiratory Viruses by Direct Immunofluorescence  

PubMed Central

The use of fluorescein-conjugated antiserum against respiratory syncytial (RS) and parainfluenza 1 and 3 viruses was compared with conventional techniques in the rapid detection of virus in tissue cultures inoculated with pharyngeal specimens known to contain these viruses. Twenty-three specimens were tested: 9 RS, 8 parainfluenza 1, and 6 parainfluenza 3. The fluorescent-antibody technique (FA) detected virus in 52% of the tissue cultures in 24 hr, and, by 72 hr, 22 of the 23 cultures were FA-positive whereas only 5 were positive by conventional techniques. Additionally, conjugated antisera were prepared against herpes simplex, influenza A2, and adenovirus type 5. All conjugates stained only the homologous virus and were 100- to 10,000-fold more sensitive than conventional techniques in detecting descending dilutions of virus inocula by 24 hr. With the procedures described, several antisera could be conjugated and ready for use within 24 hr. Serum fractionation was by ammonium sulfate precipitation, and with the procedure outlined virtually complete recovery of the globulin fraction and elimination of all of the albumin were accomplished. Images

D'Alessio, Donn; Williams, Stanley; Dick, Elliot C.



Initial attempts at directly detecting alpha wave activity in the brain using MRI  

Microsoft Academic Search

The “direct detection” of neuronal activity by MRI could offer improved spatial and temporal resolution compared to the blood oxygenation level-dependent (BOLD) effect. Here we describe initial attempts to use MRI to detect directly the neuronal currents resulting from spontaneous alpha wave activity, which have previously been shown to generate the largest extracranial magnetic fields. Experiments were successfully carried out

Daniel Konn; Sean Leach; Penny Gowland; Richard Bowtell



Detection of Trichomonas vaginalis in vaginal specimens by direct immunofluorescence assay.  

PubMed Central

Vaginal discharge specimens from 105 women were examined by wet mount, culture, and a new direct immunofluorescence assay to detect Trichomonas vaginalis. The organism was detected by culture in 31 patients, by direct immunofluorescence in 26 patients, and by wet mount in 21 patients.

Smith, R F



Enhancing spectral efficiency and receiving sensitivity in a direct-detected OFDM system  

Microsoft Academic Search

In this paper, we will review our latest developments in improving the spectral efficiency and receiving sensitivity in a direct-detected OFDM transmission system. An RF-tone assisted virtual single sideband (VSSB) OFDM modulation format is proposed to enhance the spectral efficiency in both electrical and optical domains for direct detected OFDM applications. The receiving sensitivity can be improved by using an

Kai-Ming Feng; Wei-Ren Peng



Study of direct detection technique for zero cross correlation code in OCDMA  

Microsoft Academic Search

This paper investigates the performance of direct detection technique for zero cross correlation code in Optical Code Division Multiple Access (OCDMA) which is a better technique to reduce Multi Access Interference (MAI). MAI is the main reason for performance degradation in optical CDMA especially when large numbers of users are involved. The implementation of direct detection whereby only a pair

C. B. M. Rashidi; M. S. Anuar; S. A. Aljunid



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



Colorimetric \\/ fluorescent bacterial sensing by agarose-embedded lipid \\/ polydiacetylene films  

Microsoft Academic Search

Aim: Development of a new chromatic (colorimetric ?fluorescence) bacterial sensor, for rapid, sensitive and versatile detection of bacterial proliferation. Methods and Results: We constructed agarose-embedded chromatic films which produce dramatic colour changes and fluorescence transformations in response to bacterial growth. The sensing constructs comprise glass-supported Langmuir-Schaeffer phospholipid ?polydiacetylene films that undergo both blue-red transformations and induction of intense fluorescence following

D. Meir; L. Silbert; R. Volinsky; S. Kolusheva; I. Weiser; R. Jelinek



Detection of nucleic acid sequences by invader-directed cleavage  

SciTech Connect

The present invention relates to means for the detection and characterization of nucleic acid sequences, as well as variations in nucleic acid sequences. The present invention also relates to methods for forming a nucleic acid cleavage structure on a target sequence and cleaving the nucleic acid cleavage structure in a site-specific manner. The 5' 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)



An Illumination-Adaptive Colorimetric Measurement Using Color Image Sensor  

Microsoft Academic Search

An image sensor for a use of colorimeter is characterized based on the CIE standard colorimetric observer. We use the method of least squares to derive a colorimetric characterization matrix between RGB output signals and CIE XYZ tristimulus values. This paper proposes an adaptive measuring method to obtain the chromaticity of colored scenes and illumination through a 3×3 camera transfer

Sung-Hak Lee; Jong-Hyub Lee; Kyu-Ik Sohng



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



Comparison of HPLC and colorimetric methods for measuring cellulolytic activity  

Microsoft Academic Search

The sugars released during a standard filter paper assay were quantified by colorimetric (Dinitrosalicylic acid and Nelson and Somogyi) and HPLC methods. It was found that the composition of the sugars present in the hydrolysates greatly influenced the final filter paper units of activity obtained. In a ß-glucosidase deficient cellulase system the filter paper activity reported using colorimetric methods could

W. Schwald; M. Chart; C. Breuil; J. N. Saddler



Directed module detection in a large-scale expression compendium.  


Public online microarray databases contain tremendous amounts of expression data. Mining these data sources can provide a wealth of information on the underlying transcriptional networks. In this chapter, we illustrate how the web services COLOMBOS and DISTILLER can be used to identify condition-dependent coexpression modules by exploring compendia of public expression data. COLOMBOS is designed for user-specified query-driven analysis, whereas DISTILLER generates a global regulatory network overview. The user is guided through both web services by means of a case study in which condition-dependent coexpression modules comprising a gene of interest (i.e., "directed") are identified. PMID:22144152

Fu, Qiang; Lemmens, Karen; Sanchez-Rodriguez, Aminael; Thijs, Inge M; Meysman, Pieter; Sun, Hong; Fierro, Ana Carolina; Engelen, Kristof; Marchal, Kathleen



Introducing Hyperpolarized Xenon-131 Directly Detected by NMR Spectroscopy  

NASA Astrophysics Data System (ADS)

Previously, high-field NMR and MRI applications of hyperpolarized (hp) noble gasses focused on the isotopes helium-3 (spin I = 1/2), xenon-129 (spin I = 1/2) [1], and more recently krypton-83 (spin I = 9/2) [2]. In this contribution, hp xenon-131 (spin I = 3/2) was generated by spin-exchange optical pumping and separated from the rubidium vapor for high field NMR detection at 14.1 T field strength. Xenon-131 is of particular interest because of its quadrupolar nature that can be utilized for the study of surfaces [3] and for the investigation of high magnetic field effects on the electronic structure of the noble gas atom [4]. In addition, this isotope is a useful probe for quadrupolar processes during gas transfer and during NMR/MRI detection. Experiments with xenon-131, including multiple quantum filtered NMR spectroscopy [3], provides insights into similar processes present in krypton-83 and its more complicated spin system [5]. [1] D. Raftery Ann. Rep. NMR Spec., 57, 208 (2006). [2] G. Pavlovskaya, et al., Pro. Natl. Acad. Sci. U.S.A. 102, 18275 (2005). [3] T. Meersmann et al., Phys. Rev. Lett. 80, 1398 (1998). [4] T. Meersmann and M. Haake, Phys. Rev. Lett. 81, 1211 (1998). [5] Z. Cleveland, et al., J. Chem. Phys.124, 044312 (2006).

Stupic, Karl; Cleveland, Zackary; Pavlovskaya, Galina; Meersmann, Thomas



Integrated Optical Displacement Detection and Electrostatic Actuation for Directional Optical Microphones With Micromachined Biomimetic Diaphragms  

Microsoft Academic Search

In this paper, integration and packaging of directional biomimetic microphones using a diffraction-based optical displacement detection method is described. The optical detection method senses the displacement of the microphone diaphragm by monitoring the change in the intensity of a diffracted laser beam. A detailed optical model of the integrated optical detection scheme is developed and used to guide the package

Baris Bicen; Sunny Jolly; Kamran Jeelani; Caesar T. Garcia; Neal A. Hall; F. Levent Degertekin; Quang Su; Weili Cui; Ronald N. Miles



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



Direct detection of residual cyanide in cassava using spectroscopic techniques.  


Fluorescence, infrared, scanning electron microscopy (SEM), UV-visible, and X-ray diffraction (XRD) techniques have been applied to monitor the effect of processing mode on the residual cyanogens in cassava roots. The processed samples' infrared spectra have shown that only the boiled sample contains residual cyanide. SEM micrographs have revealed that irregularly shaped granules of about 100-microm size contain cyanide, while spherical granules of about 10-microm size do not. X-ray diffraction patterns have shown that the intensities of peaks are not affected by the presence of cyanide in the cassava samples. Fluorescence and UV-visible studies have detected the presence of cyanide converted to cyanate in water used for soaking processes. The thermal behavior of cassava samples with respect to the cyanide content and the role of oxygen and different ions present in water used for soaking processes are also discussed. PMID:17973447

Phambu, Nsoki; Meya, Anderson Sunda; Djantou, Elie Beaudelaire; Phambu, Esther Nzuzi; Kita-Phambu, Pambu; Anovitz, Lawrence M



Direct Detection and Spectra of Exoplanets with SPICA  

NASA Astrophysics Data System (ADS)

SPICA coronagraph instrument (SCI) provides a high-contrast imaging and a high resolution spectroscopy (R¡1000) in the wavelength range of 3.5 to 25 micrometers.SCI will search for gas giant planets around nearby stars and young stars to reveal nature of planetary formation and evolution. Thanks to the high sensitivity and high contrast in the wavelengths longer than 10 micrometers, SCI also allows us to directly reach Jupiter-mass planets around very old stars (5Gyr) at 10pc, and also characterize the planets by the spectroscopy observations. SCI will be complementary to JWST and ground-based telescopes with extreme AO. In this poster, we summarize the SCI's capabilities and present our strategy.

Matsuo, Taro; Fukagawa, Misato; Kotani, Takayuki; Itoh, Yoichi; Tamura, Motohide; Nakagawa, Takao; Enya, Keigo


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  

Microsoft Academic Search

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 t o2ht operform. Both a Legionella genus PCR assay and Legionella pneumophila species-specific PCR assay were designed. A total of 43 archived specimens

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



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.



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.



Comparison of Chemicon SimulFluor Direct Fluorescent Antibody Staining with Cell Culture and Shell Vial Direct Immunoperoxidase Staining for Detection of Herpes Simplex Virus and with Cytospin Direct Immunofluorescence Staining for Detection of Varicella-Zoster Virus  

Microsoft Academic Search

A new rapid direct immunofluorescence assay, the SimulFluor direct fluorescent-antibody (DFA) assay, which can simultaneously detect herpes simplex virus types 1 and 2 (HSV-1 and -2) and varicella-zoster virus (VZV), was evaluated in comparison with our current standard procedures of (i) shell vial direct immuno- peroxidase (shell vial IP) staining and cell culture for detection of HSV and (ii) cytospin




Improved Eavesdropping Detection Strategy in Quantum Direct Communication Protocol Based on Five-Particle Cluster State  

NASA Astrophysics Data System (ADS)

In order to improve the eavesdropping detection efficiency in a two-step quantum direct communication protocol, an improved eavesdropping detection strategy using the five-particle cluster state is proposed in which the five-particle cluster state is used to detect eavesdroppers. During the security analysis, the method of the entropy theory is introduced, and two detection strategies are compared quantitatively by using the constraint between the information that the eavesdropper can obtain and the interference that has been introduced. If the eavesdroppers intend to obtain all information, the eavesdropping detection rate of the original two-step quantum direct communication protocol by using EPR pair block as detection particles will be 50 %; while the proposed strategy's detection rate will be 88 %. In the end, the security of the proposed protocol is discussed. The analysis results show that the eavesdropping detection strategy presented is more secure.

Li, Jian; Jin, Hai-Fei; Jing, Bo



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.



Direct Detection of Trivelpiece-Gould Modes in Helicon Discharges  

NASA Astrophysics Data System (ADS)

It has been suggested^1 that Trivelpiece-Gould (TG) modes near the plasma surface are essential for the absorption of rf energy in helicon (H) discharges. At high fields B_0, TG modes are damped in a thin layer and are difficult to resolve with probes. At low B_0, however, TG modes have longer radial wavelengths and interfere with the H waves, changing the radial wave amplitude profiles. This change was barely detectable when the wave Bz was measured with B-dot probes. However, theory suggests that the current Jz would emphasize the TG mode over the H mode by a factor ? _TG/? _H. We have constructed and carefully calibrated an rf J-dot probe to measure the Jz profiles. Measurements were made in a narrow window of n-B0 space where the coupled H-TG wave has a distinctive profile AND have ? _TG/? H > 2. The Jz profiles clearly show the secondary amplitude peaks due to the TG mode, in agreement with numerical calculations. ^1 D. Arnush, Phys. Plasmas 7, 3042 (2000).

Blackwell, D. D.; Madziwa, T. G.; Arnush, D.; Chen, F. F.



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.  


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



Colorimetric method for determining Pb2+ ions in water enhanced with non-precious-metal nanoparticles.  


Sulfur anions and their derivatives have long been recognized for their high selectivity and reactivity toward Pb(2+) ions and formation of highly absorptive yet water-insoluble compounds with both acid and base media. This phenomenon has been used for qualitative analysis of lead ions in water. We demonstrate a new method to quantitatively determine the Pb(2+) concentration in the range of 0.5-500 ppm in water using colorimetric measurement, based on forming "soluble" lead sulfide in water enhanced with non-precious-metal nanoparticles. This method has inherent high selectivity for lead over other alkali-metal and alkaline-earth-metal ions. The colorimetric measurements of the absorptive solutions provide accurate determination of the lead concentration in water comparable to that measured using inductively coupled plasma mass spectrometry. To our knowledge, this is the simplest, lowest cost, and easiest-to-use method for detecting and determining the lead concentration in water. PMID:22686469

Yan, Jeffrey; Indra, Erik M



High-throughput colorimetric assays for nucleotide sugar formation and glycosyl transfer.  


Glycosyltransferases are ubiquitous in nature, catalyzing glycosidic bond formation in the context of an enormous range of substrates, which include all major classes of biological molecules. Because this wide range of substrates lacks a shared, distinguishable feature that can be altered by glycosyl transfer, general assays for detection of glycosyltransferase activity have long been largely limited to low-throughput methods. Of those high-throughput assays reported in the literature, many are confined to specific glycosyl transfer reactions with modified aglycon acceptors selected for their unique analytical properties. Herein are described a series of protocols centered on the use of 2-chloro-4-nitrophenyl glycoside donors and the reversibility of glycosyltransferase-catalyzed reactions to enable a colorimetric assay for the formation of sugar nucleotides, coupled reaction systems for the glycodiversification of small molecules, and a general colorimetric assay for glycosyltransfer, applicable to drug discovery, protein engineering, and other fundamental sugar nucleotide-dependent investigations. PMID:23034237

Gantt, Richard W; Thorson, Jon S



Direct-detection optical CDMA receiver with interference estimation and double optical hardlimiters  

Microsoft Academic Search

This paper proposes a new channel interference cancellation technique using interference estimation and double optical hardlimiters (DHLs) for direct-detection optical code-division multiple-access systems. In the proposed system, when the output of the DHL is \\

Kenji Wakafuji; Tomoaki Ohtsuki



Assessing the Performance of Omni-Directional Receivers for Passive Acoustic Detection of Vocalizing Odontocetes.  

National Technical Information Service (NTIS)

Acoustic detection and localization of marine mammals will assist mitigation efforts for various Naval and scientific missions that may impact protected species. This study sought to experimentally quantify the sonar performance of omni-directional receiv...

J. M. Daziens



Two Highly Sensitive and Selective Colorimetric "Off-On" Rhodamine-Based Fluorescent Chemosensor for Hg(II) in Aqueous Media.  


Two novel rhodamine derivatives were designed and synthesized. They were successfully characterized by HR-MS, (1)H NMR and (13)C NMR. They were found to exhibit a reversible colorimetric response and exhibit high selectivity and sensitivity for Hg(II) ion over other commonly coexistent metal ions. Their selectivity is excellent, and the detection of Hg(II) at ppb level is possible. The colorimetric and fluorescent response to Hg(II) can be conveniently detected even by the naked eye, which provides a facile method for visual detection of Hg(II). PMID:23653127

Zhang, Di; Wang, Min; Wang, Cuicui; Li, Man; Ye, Yong; Zhao, Yufen



Ultrasensitive detection of coliforms by means of direct asymmetric PCR combined with disposable magnetic amperometric genosensors.  


An extremely sensitive procedure for the isolation and detection of DNA from bacterial cell cultures is described. Direct asymmetric PCR amplified products from E. coli cultures are specifically detected, at a concentration level as low as 0.01 cfu mL(-1) (cfu, colony forming unit), using disposable magnetic DNA hybridization amperometric sensors with no need for culture preconcentration steps. PMID:19082171

Loaiza, Oscar A; Campuzano, Susana; Pedrero, María; García, Pedro; Pingarrón, José M



Challenges of Detecting Directional Selection After a Bottleneck: Lessons From Sorghum bicolor  

Microsoft Academic Search

Multilocus surveys of sequence variation can be used to identify targets of directional selection, which are expected to have reduced levels of variation. Following a population bottleneck, the signal of directional selection may be hard to detect because many loci may have low variation by chance and the frequency spectrum of variation may be perturbed in ways that resemble the

Martha T. Hamblin; Alexandra M. Casa; Hong Sun; Seth C. Murray; Andrew H. Paterson; Charles F. Aquadro; Stephen Kresovich



Title detection algorithm for OCR credentials image based on directional projection and divergence  

Microsoft Academic Search

According to the OCR character region in OCR credentials image, a new skew detection method was presented by using Bresenham's integer only line drawing algorithm and within-group measure of dispersion. Several directional projection are calculated in the algorithm by using Bresenham's integer line drawing algorithm. At the same time calculating minimal within-group measure of dispersion of the directional projection. After

Zhiwen Wang; Guoqing Xie; Shaozi Li; Zhi LIUI



Label-free microarray imaging for direct detection of DNA hybridization and single-nucleotide mismatches  

Microsoft Academic Search

A novel method is proposed for direct detection of DNA hybridization on microarrays. Optical interferometry is used for label-free sensing of biomolecular accumulation on glass surfaces, enabling dynamic detection of interactions. Capabilities of the presented method are demonstrated by high-throughput sensing of solid-phase hybridization of oligonucleotides. Hybridization of surface immobilized probes with 20 base pair-long target oligonucleotides was detected by

Emre Özkumur; Sunmin Ahn; Ayça Yalç?n; Carlos A. Lopez; Elif Çevik; Rostem J. Irani; Charles DeLisi; Marcella Chiari; M. Selim Ünlü



Evaluation of 15 Motility Media and a Direct Microscopic Method for Detection of Motility in Enterococci  

Microsoft Academic Search

Isolation of motile, vanC enterococci has yet to be a major infection control concern; however, rapid detection still is important. We evaluated 15 motility media from three manufacturers and a 2-h direct microscopic method for accurate detection of 89 enterococcal strains, including 72 vanC enterococcal strains. Resistance genes were confirmed by a multiplex PCR method with the vanC gene detected

Kenneth Van Horn; Clara Toth; Reiko Kariyama; Ritsuko Mitsuhata; Hiromi Kumon



Real-time luminescence-based colorimetric determination of double-strand DNA in droplet on demand.  


We have developed a new luminescence-based colorimetric droplet platform for the determination of double-stranded DNAs (dsDNA). This colorimetric sensor was realized via choosing a fluorescent ensemble probe comprising water-soluble N-acetylcysteine-capped CdTe quantum dots (QDs) and Ru(bpy)(2)(dppx)(2+) (Ru). To provide a convenient and low cost droplet platform for colorimetry, the microvalve technique was adapted to adjust droplet size precisely, achieve the desired fusion of multiple droplets and trap droplets on demand, as well as implement concentration gradients of DNA on a single chip. In the colorimetric sensor, Ru served as both an effective quencher for QDs and a reporter for dsDNA. With increasing concentration of dsDNA, a gradually enhanced color response was observed because of the competition of dsDNA with QDs for Ru. Under the optimum conditions, this biosensing system exhibited not only good sensitivity and specificity for calf thymus DNA with the detection limit of 1.0 pg, but also coincident performances in diluted human serum with the detection limit of 0.9 pg. The droplet biosensor provides a highly efficient, rapid and visual method for dsDNA analysis. The colorimetric droplet platform could be useful as a simple research tool for the study of limited and precious regents such as protein and virus samples, etc. PMID:22196878

Xiang, Xia; Chen, Lu; Zhuang, Qinggeng; Ji, Xinghu; He, Zhike



Direct Detection of 16S rRNA in Soil Extracts by Using Oligonucleotide Microarrays  

PubMed Central

We report on the development and validation of a simple microarray method for the direct detection of intact 16S rRNA from unpurified soil extracts. Total RNAs from Geobacter chapellei and Desulfovibrio desulfuricans were hybridized to an oligonucleotide array consisting of universal and species-specific 16S rRNA probes. PCR-amplified products from Geobacter and Desulfovibrio were easily and specifically detected under a range of hybridization times, temperatures, and buffers. However, reproducible, specific hybridization and detection of intact rRNA could be accomplished only by using a chaperone-detector probe strategy. With this knowledge, assay conditions were developed for rRNA detection using a 2-h hybridization time at room temperature. Hybridization specificity and signal intensity were enhanced using fragmented RNA. Formamide was required in the hybridization buffer in order to achieve species-specific detection of intact rRNA. With the chaperone detection strategy, we were able to specifically hybridize and detect G. chapellei 16S rRNA directly from a total-RNA soil extract, without further purification or removal of soluble soil constituents. The detection sensitivity for G. chapellei 16S rRNA in soil extracts was at least 0.5 ?g of total RNA, representing approximately 7.5 × 106 Geobacter cell equivalents of RNA. These results suggest that it is now possible to apply microarray technology to the direct detection of microorganisms in environmental samples, without using PCR.

Small, Jack; Call, Douglas R.; Brockman, Fred J.; Straub, Timothy M.; Chandler, Darrell P.



The use of colorimetric sensor arrays to discriminate between pathogenic bacteria.  


A colorimetric sensor array is a high-dimensional chemical sensor that is cheap, compact, disposable, robust, and easy to operate, making it a good candidate technology to detect pathogenic bacteria, especially potential bioterrorism agents like Yersinia pestis and Bacillus anthracis which feature on the Center for Disease Control and Prevention's list of potential biothreats. Here, a colorimetric sensor array was used to continuously monitor the volatile metabolites released by bacteria in solid media culture in an Advisory Committee on Dangerous Pathogen Containment Level 3 laboratory. At inoculum concentrations as low as 8 colony-forming units per plate, 4 different bacterial species were identified with 100% accuracy using logistic regression to classify the kinetic profile of sensor responses to culture headspace gas. The sensor array was able to further discriminate between different strains of the same species, including 5 strains of Yersinia pestis and Bacillus anthracis. These preliminary results suggest that disposable colorimetric sensor arrays can be an effective, low-cost tool to identify pathogenic bacteria. PMID:23671629

Lonsdale, Claire L; Taba, Brian; Queralto, Nuria; Lukaszewski, Roman A; Martino, Raymond A; Rhodes, Paul A; Lim, Sung H



Evaluation of Colorimetric Methods for Measuring Reduced (Ferrous) Iron.  

National Technical Information Service (NTIS)

This technical note describes a comparative study of colorimetric methods for real-time measurements of ferrous iron in reservoir tailwaters. Two methods were evaluated: the 1,10 phenanthroline method for the Hach DR/2000 spectrophotometer (Hach Company, ...

S. P. Faulkner P. E. Hintze S. L. Ashby



Development of an isoenzyme-specific colorimetric assay for tissue transglutaminase 2 cross-linking activity.  


Tissue transglutaminase (TGase 2) belongs to the multigene transglutaminase family of Ca2+-dependent protein cross-linking enzymes. Based on the transamidation activity of TGase 2, a novel colorimetric assay has been developed using covalently coupled spermine to carboxy-substituted polystyrene plates and biotinylated pepT26, an excellent acyl-donor substrate, highly specific for TGase 2. The assay is based on the incorporation of the gamma-carboxamide of glutamine of pepT26 into the immobilized spermine. The amount of biotinylated pepT26 bound to the plate, as measured by the activity of streptavidin-peroxidase, is directly proportional to the TGase activity. The colorimetric procedure showed a good correlation (r=0.995) with the commonly used radiometric filter paper method for TGase2, and provides linear dose-response curves over a wide range of hrTGase2 concentrations (2.5-40 microU/ml). In addition, the assay shows higher sensitivity when compared with our previous TG-colorimetric test (more than 50-fold increase) and other existing assays. PepT26 displays strong reactivity with TGase 2, and no reactivity with TGases 1, 3, and FXIII. The procedure constitutes a rapid, TG2-specific, sensitive, and nonisotopic method for the measurement of TGase 2 activity in as low as 4ng of hrTGase 2 and purified guinea pig liver transglutaminase, and 1.25mug of guinea pig liver extracts. PMID:19318081

Perez Alea, Mileidys; Kitamura, Miyako; Martin, Guillaume; Thomas, Vincent; Hitomi, Kiyotaka; El Alaoui, Saïd



Direct surface plasmon resonance immunosensor for in situ detection of benzoylecgonine, the major cocaine metabolite.  


In this paper the development of the first direct surface plasmon resonance (SPR) immunoassay for the detection of benzoylecgonine (BZE) is described. Immunosensor chips consisting of a high affinity monoclonal anti-BZE-antibody (anti-BZE-Ab) immobilized at high density to a sensor chip were prepared. First, BZE detection in Hepes buffer was achieved by direct, real time monitoring of the binding between BZE in solution and the surface bound antibody. The detection protocol was based on calibration curves obtained from reaction rate data and end point data analysis of sensorgrams registered after injection of a series of known BZE concentrations over the chips. Moreover, immunosensor accuracy, reproducibility, stability and robustness were tested to demonstrate their good performance as reusable devices. The immunosensor was used for BZE detection in oral fluid (OF) showing that, within 180 s, our immunoassay detects BZE concentrations as low as 4 ?g/L in filtered OF-buffer (1:4) samples. This value is remarkably lower than current cut off levels established by the Substance Abuse and Mental Health Services Administration. These results manifest the potential use of this direct SPR immunoassay for the in situ sensitive detection of recent cocaine abuse, of utility in roadside drug OF testing. Moreover, it exemplifies the high potential of direct SPR immunoassays for the rapid, sensitive detection of small molecules in contrast with the more established indirect methods. PMID:21664118

Munoz, Eva M; Lorenzo-Abalde, Silvia; González-Fernández, Africa; Quintela, Oscar; Lopez-Rivadulla, Manuel; Riguera, Ricardo



Deciphering inflation with gravitational waves: Cosmic microwave background polarization vs direct detection with laser interferometers  

SciTech Connect

A detection of the primordial gravitational wave background is considered to be the 'smoking-gun' evidence for inflation. While superhorizon waves are probed with cosmic microwave background (CMB) polarization, the relic background will be studied with laser interferometers. The long lever arm spanned by the two techniques improves constraints on the inflationary potential and validation of consistency relations expected under inflation. If gravitational waves with a tensor-to-scalar amplitude ratio greater than 0.01 are detected by the CMB, then a direct-detection experiment with a sensitivity consistent with current concept studies should be pursued vigorously. If no primordial tensors are detected by the CMB, a direct-detection experiment to understand the simplest form of inflation must have a sensitivity improved by two to 3 orders of magnitude over current plans.

Smith, Tristan L. [California Institute of Technology, Mail Code 130-33, Pasadena, California 91125 (United States); Peiris, Hiranya V. [Kavli Institute for Cosmological Physics and Enrico Fermi Institute, University of Chicago, Chicago Illinois 60637 (United States); Cooray, Asantha [Center for Cosmology, Department of Physics and Astronomy, University of California, Irvine, California 92697 (United States)



Infrared adaptive spectral imagers for direct detection of spectral signatures and hyperspectral imagery  

NASA Astrophysics Data System (ADS)

Field test results are presented for a prototype long-wave adaptive imager that provides both hyperspectral imagery and contrast imagery based on the direct application of hyperspectral detection algorithms in hardware. Programmable spatial light modulators are used to provide both spectral and spatial resolution using a single element detector. Programmable spectral and spatial detection filters can be used to superimpose any possible analog spectral detection filter on the image. In this work, we demonstrate three modes of operation, including hyperspectral imagery, and one and two-dimensional imagery using a generalized matched filter for detection of a specific target gas within the scene.

Goldstein, Neil; Fox, Marsha; Adler-Golden, Steven; Gregor, Brian



A label-free and colorimetric turn-on assay for coralyne based on coralyne-induced formation of peroxidase-mimicking split DNAzyme.  


A simple, label-free and colorimetric method for coralyne detection was successfully established based on the coralyne-induced formation of split G-quadruplex-hemin DNAzyme. It can achieve a detection limit of 31 nM toward coralyne with excellent selectivity. PMID:23869385

Hou, Ting; Wang, Xiuzhong; Liu, Xiaojuan; Liu, Shufeng; Du, Zongfeng; Li, Feng



Magnetically trigged direct electrochemical detection of DNA hybridization using Au67 quantum dot as electrical tracer.  


A novel gold nanoparticle-based protocol for detection of DNA hybridization based on a magnetically trigged direct electrochemical detection of gold quantum dot tracers is described. It relies on binding target DNA (here called DNA1) with Au(67) quantum dot in a ratio 1:1, followed by a genomagnetic hybridization assay between Au(67)-DNA1 and complementary probe DNA (here called DNA2) marked paramagnetic beads. Differential pulse voltammetry is used for a direct voltammetric detection of resulting Au(67) quantum dot-DNA1/DNA2-paramagnetic bead conjugate on magnetic graphite-epoxy composite electrode. The characterization, optimization, and advantages of the direct electrochemical detection assay for target DNA are demonstrated. The two main highlights of presented assay are (1) the direct voltammetric detection of metal quantum dots obviates their chemical dissolution and (2) the Au(67) quantum dot-DNA1/DNA2-paramagnetic bead conjugate does not create the interconnected three-dimensional network of Au-DNA duplex-paramagnetic beads as previously developed nanoparticle DNA assays, pushing down the achievable detection limits. PMID:16207045

Pumera, Martin; Castañeda, Maria Teresa; Pividori, Maria Isabel; Eritja, Ramon; Merkoçi, Arben; Alegret, Salvador



Colorimetric determination of beta-blockers in pharmaceutical formulations.  


A simple, accurate, precise and sensitive colorimetric method for the determination of some beta-blockers as atenolol (Ateno), metoprolol (Metop), sotalol (Sot) and nadolol (Nad) is described. This method is based on the formation of charge transfer complex with 4-chloro-7-nitro-2,1,3-benzoxadiazole (NBD-Cl) in methanolic-aqueous (for Ateno and Metop) or acetone-aqueous (for Sot and Nad) medium [30% (v/v)]. The orange color products are measured at 485, 470, 465 and 462 nm for Ateno, Metop, Sot and Nad, respectively. The optimization of various experimental conditions is described. Beer's law is obeyed in the range 0.4-60 microgram ml(-1) while that obtained applying Ringbom is 0.8-56 microgram ml(-1). The molar absorptivity, Sandell sensitivity, detection and quantification limits are calculated. The results obtained showed good recoveries of 99.5+/-1.1, 100.3+/-1.2, 100.5+/-1.0 and 99.3+/-1.1% with relative standard deviations of 0.74, 0.98, 1.15 and 0.87% for Ateno, Metop, Sot and Nad, respectively. Applications of the proposed method to representative pharmaceutical formulations are successfully presented. PMID:12408925

Amin, A S; Ragab, G H; Saleh, H



Colorimetric determination of reducing normality in the Purex process  

SciTech Connect

Adjustment of the valence state of plutonium from extractable Pu(IV) to nonextractable Pu(III) in the Purex process is accomplished by addition of reductants such as Fe(II), hydroxylamine nitrate (HAN), or U(IV). To implement on-line monitoring of this reduction step for improved process control at the Savannah River Plant, a simple colorimetric method for determining excess reductant (reducing normality) was developed. The method is based on formation of a colored complex of Fe(II) with FerroZine (Hach Chemical Company). The concentration of Fe(II) is determined directly. The concentration of HAN or U(IV), in addition to Fe(II), is determined indirectly as Fe(II), produced through reduction of Fe(III). Experimental conditions for a HAN-Fe(III) reaction of known stoichiometry were established. The effect of hydrazine, which stabilizes U(IV), was also determined. Real-time measurements of color development were made that simulated on-line performance. A laboratory analytical procedure is included. 5 references, 8 figures.

Baumann, E.W.



Detection of Mycobacterium avium subsp. paratuberculosis by a Direct In Situ PCR Method  

PubMed Central

In situ detection of Mycobacterium avium subsp. paratuberculosis is useful for diagnosis and research of paratuberculosis. The aim of this paper was to detect this agent in formalin-fixed, paraffin-embedded tissue samples by a direct in situ PCR. The technique was performed on ileum or ileocaecal lymph node samples from 8 naturally infected cattle and 1 healthy calf, by using p89 and p92 primers for amplification of IS900 sequence. Moderate positive signal was detected in all positive samples and not in negative control, but tissues resulted were affected in many cases due to the enzymatic treatment and the high temperature exposition. Although the technique was useful for Map detection, the signal was lower than immunohistochemistry probably because of the fixation process. In one case, signal was higher, which might be due to the detection of spheroplasts. Thus, the described method should be recommended when others resulted negative or for spheroplasts detection.

Delgado, Fernando; Aguilar, Diana; Garbaccio, Sergio; Francinelli, Gladys; Hernandez-Pando, R.; Romano, Maria Isabel



Detection of Mycobacterium avium subsp. paratuberculosis by a Direct In Situ PCR Method.  


In situ detection of Mycobacterium avium subsp. paratuberculosis is useful for diagnosis and research of paratuberculosis. The aim of this paper was to detect this agent in formalin-fixed, paraffin-embedded tissue samples by a direct in situ PCR. The technique was performed on ileum or ileocaecal lymph node samples from 8 naturally infected cattle and 1 healthy calf, by using p89 and p92 primers for amplification of IS900 sequence. Moderate positive signal was detected in all positive samples and not in negative control, but tissues resulted were affected in many cases due to the enzymatic treatment and the high temperature exposition. Although the technique was useful for Map detection, the signal was lower than immunohistochemistry probably because of the fixation process. In one case, signal was higher, which might be due to the detection of spheroplasts. Thus, the described method should be recommended when others resulted negative or for spheroplasts detection. PMID:21772965

Delgado, Fernando; Aguilar, Diana; Garbaccio, Sergio; Francinelli, Gladys; Hernández-Pando, R; Romano, María Isabel



Loop-induced dark matter direct detection signals from ?-ray lines  

NASA Astrophysics Data System (ADS)

Improved limits as well as tentative claims for dark matter annihilation into ?-ray lines have been presented recently. We study the direct detection cross section induced from dark matter annihilation into two photons in a model-independent fashion, assuming no additional couplings between dark matter and nuclei. We find a striking non-standard recoil spectrum due to different destructively interfering contributions to the dark matter nucleus scattering cross section. While in the case of s-wave annihilation the current sensitivity of direct detection experiments is insufficient to compete with indirect detection searches, for p-wave annihilation the constraints from direct searches are comparable. This will allow to test dark matter scenarios with p-wave annihilation that predict a large di-photon annihilation cross section in the next generation of experiments.

Frandsen, Mads T.; Haisch, Ulrich; Kahlhoefer, Felix; Mertsch, Philipp; Schmidt-Hoberg, Kai



Direct detection of optical radiation through a sampling orifice for inductively coupled plasma atomic emission spectroscopy  

SciTech Connect

The direct optical viewing of an argon inductively coupled plasma (ICP) through a sampling orifice inserted directly into the plasma has been accomplished. A copper cone with a sampling orifice is attached to the entrance slit chamber of a monochromator and inserted directly into an ICP to obtain optical spectra in the vacuum ultraviolet (VUV). With solar-blind photomultiplier tube (PMT) detection, detection limits are 50 ng mL/sup -1/ for the resonance lines of Br and Cl during injection into the plasma of aerosols of aqueous solutions generated by pneumatic nebulization. With ultrasonic nebulization, the detection limits improve to 8 ng mL/sup -1/ for Br and 15 ng mL/sup -1/ for Cl. Detection limits for Br and Cl in the form of an aqueous sample were superior to the best reported values in the Ar and He ICP, and in the microwave-induced plasma atomic emission spectroscopy (MIP-AES) literature. Another significant breakthrough in the present work includes the determination of nonmetals in gases by their direct injection into the ICP by a device called a direct injection probe (DIP). This low dead volume interface (<40 is used for the introduction of gaseous samples directly into the axial channel of the ICP. Injection of a gaseous mixture of compounds containing the elements Br, Cl, S, and C results in detection limits of 0.1, 0.3, 0.05, and 1 ng, respectively. These detection limits are by far the best obtained for these elements in a gaseous form by ICP-AES. The extension of ICP-AES analysis to the determination of nonmetals, metalloids, and/or selected metals in aqueous and gaseous samples illustrates the value of this optical sampling approach in the VUV. 174 refs., 50 figs.

LaFreniere, B.R.



Migratory birds use head scans to detect the direction of the earth's magnetic field.  


Night-migratory songbirds are known to use a magnetic compass , but how do they detect the reference direction provided by the geomagnetic field, and where is the sensory organ located? The most prominent characteristic of geomagnetic sensory input, whether based on visual patterns or magnetite-mediated forces , is the predicted symmetry around the north-south or east-west magnetic axis. Here, we show that caged migratory garden warblers perform head-scanning behavior well suited to detect this magnetic symmetry plane. In the natural geomagnetic field, birds move toward their migratory direction after head scanning. In a zero-magnetic field , where no symmetry plane exists, the birds almost triple their head-scanning frequency, and the movement direction after a head scan becomes random. Thus, the magnetic sensory organ is located in the bird's head, and head scans are used to locate the reference direction provided by the geomagnetic field. PMID:15530397

Mouritsen, Henrik; Feenders, Gesa; Liedvogel, Miriam; Kropp, Wiebke



Development of a routine laboratory direct detection system of staphylococcal enterotoxin genes  

Microsoft Academic Search

A novel direct detection system has been developed for eight staphylococcal enterotoxin (SE)-encoding genes (sea, seb, sec, sed, see, seg, seh and sei) in milk. Specific detection by real-time PCR was successful for all SE-encoding genes in the reference strains. Furthermore, a novel DNA-preparation method with good reproducibility (coefficients of variation 0?31, 0?99 and 1?21% at 106 ,1 04 and

Akifumi Nakayama; Akiko Okayama; Misao Hashida; Yasuzumi Yamamoto; Hisakatsu Takebe; Takashi Ohnaka; Tomoyuki Tanaka; Shunsuke Imai



FET-Based Biosensors for The Direct Detection of Organophosphate Neurotoxins  

Microsoft Academic Search

Recent world-wide terrorist events associated with the threat of hazardous chemical agent proliferation, and outbreaks of chemical contamination in the food supply has demonstrated an urgent need for sensors that can directly detect the presence of dangerous chemical toxins.Such sensors must enable real-time detection and accurate identification of different classes of pesticides (e.g., carbamates and organophosphates) but must especially discriminate

J. R. Wildc



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




Detection of mRNA by non-radioactive direct primed in situ reverse transcription  

Microsoft Academic Search

There are various techniques to detect mRNA in tissue specimens. Among these in situ hybridization is widely applied, and for the detection of small quantities of RNA in situ reverse transcriptase polymerase chain reaction (in situ RT-PCR) has been applied. Furthermore in situ transcription, where signal is produced by direct incorporation of labeled nucleotides during production of a cDNA by

Jörg Kriegsmann; Ulf Müller-Ladner; Haiko Sprott; Rolf Bräuer; Peter K. Petrow; Mike Otto; Torsten Hansen; Renate E. Gay; Steffen Gay



RadSensor: Xray Detection by Direct Modulation of an Optical Probe Beam  

Microsoft Academic Search

We present a new x-ray detection technique based on optical measurement of the effects of x-ray absorption and electron hole pair creation in a direct band-gap semiconductor. The electron-hole pairs create a frequency dependent shift in optical refractive index and absorption. This is sensed by simultaneously directing an optical carrier beam through the same volume of semiconducting medium that has

M E Lowry; C V Bennett; S P Vernon; T Bond; R Welty; E Behymer; H Petersen; A Krey; R Stewart; N P Kobayashi; V Sperry; P Stephan; C Reinhardt; S Simpson; P Stratton; R Bionta; M McKernan; E Ables; L Ott; S Bond; J. Ayers; O L Landen; P M Bell



Poker face of inelastic dark matter: Prospects at upcoming direct detection experiments  

SciTech Connect

The XENON100 and CRESST experiments will directly test the inelastic dark matter explanation for DAMA's 8.9{sigma} anomaly. This article discusses how predictions for direct detection experiments depend on uncertainties in quenching factor measurements, the dark matter interaction with the standard model, and the halo velocity distribution. When these uncertainties are accounted for, an order of magnitude variation is found in the number of expected events at CRESST and XENON100.

Alves, Daniele S. M.; Lisanti, Mariangela [Theory Group, SLAC, Menlo Park, California 94025 (United States); Physics Department, Stanford University, Stanford, California 94305 (United States); Wacker, Jay G. [Theory Group, SLAC, Menlo Park, California 94025 (United States)



A SETI metapolicy: New directions towards comprehensive policies concerning the detection of extraterrestrial intelligence  

NASA Astrophysics Data System (ADS)

At present we have only one agreed public policy for handling the detection of an extraterrestrial intelligence (ETI), the ‘First SETI Protocol’ of 1989, which guides action in the immediate aftermath of detection, even though SETI (the Search for Extraterrestrial Intelligence) constitutes an active search for such a detection. The purpose of this paper is to set out areas in which policies might fruitfully be developed, including reviewing the rationale and investment in SETI, handling ETI artefacts, and approaches to direct contact. ‘Negative’ possibilities will be examined, for example, whether an ETI artefact or data should be purposefully destroyed.

Baxter, Stephen; Elliott, John



A simple and rapid colorimetric method for determination of phytate in urine.  


Phytate is a natural product present in urine and biological fluids that is associated with health benefits, such as the prevention of calcium renal stone formation. The available methods for phytate analysis in urine all require elaborate instrumentation and cannot be routinely applied in clinical laboratories. Here, we describe a simple procedure for urinary phytate determination, employing colorimetric detection. Our method requires purification and preconcentration of phytate via solid-phase extraction prior to colorimetric detection employing Fe(III)-thiocyanate. The working linear range of the assay is 0-5 ?M phytate. The limit of detection is 0.055 ?M. The relative standard deviation obtained upon assay of samples containing 2 ?M phytate was 3.5 %. Several urine samples were analyzed using an alternative method based on the detection of phosphorus; the results of the two assays were comparable. Our novel method of phytate analysis in human urine is simple, rapid (3 h for 10 samples), accurate, precise, reliable, and highly sensitive. The assay can be run in most analytical laboratories and does not require sophisticated instrumentation. PMID:22476541

Costa-Bauza, Antonia; Grases, F; Gomila, I; Rodriguez, A; Prieto, R M; Tur, F



Highly selective in situ metal ion determination by hybrid electrochemical "adsorption-desorption" and colorimetric methods.  


A novel and facile hybrid analytical method coupling electrochemical "adsorption-desorption" and colorimetric analyses was developed to detect heavy metal ions in turbid water samples. The target metal ions were deposited onto an electrode inserted into the original sample, which was referred to as the "adsorption" process. After changing the medium, the concentrated target metal ions were dissolved in a new, clean buffer (blank buffer), which was referred to as the "desorption" process. The concentrations of the target metal ions were measured by colorimetric analyses after the addition of specific indicator amounts. We demonstrated the applicability of this method by detecting Cd(2+), Pb(2+) and Cu(2+) with co-depositing Bi(3+) on portable screen-printed electrodes (SPEs). A good correlation (correlation coefficient of R=0.997) was observed between concentrations ranging from 1 to 200 ?M and absorbance values. After the multiple "desorption" process, the even better detection limits as low as 10, 10 and 100 nM were achieved for Cd(2+), Pb(2+) and Cu(2+), respectively. The practicality of this hybrid method was confirmed by the detection of Cd(2+), Pb(2+) and Cu(2+) in wastewater samples, and these results were in agreement with inductively coupled plasma atomic emission spectroscopy (ICP-AES). Overall, this hybrid method provides a simple, selective and effective technique for environmental pollutant analyses. PMID:21801882

Li, Meng; Li, Da-Wei; Li, Yuan-Ting; Xu, Dan-Ke; Long, Yi-Tao



A dual fluorometric and colorimetric sensor for dopamine based on BSA-stabilized Au nanoclusters.  


An easy prepared fluorometric and colorimetric dual channel probe is developed for dopamine (DA) detection with high sensitivity and selectivity by use of BSA-stabilized Au nanoclusters (BSA-AuNCs). The BSA-AuNCs exhibit strong fluorescence emission, while upon addition of DA, the AuNCs show a dramatic decrease of the fluorescence intensity as a result of the photo-induced electron transfer process from the electrostatically attached DA to the BSA-AuNCs. The detection limit of DA can be as low as 10 nM. In addition, the assay for DA can also be easy to implement for visual detection due to the observed inhibition of the peroxidase-like activity of AuNCs in the presence of DA, with a detection limit of 10 nM. Both fluorometric and colorimetric methods exhibit excellent selectivity toward DA over interfering substances. Furthermore, we demonstrate the application of the present approach in hydrochloride injection sample, human serum sample and PC12 cells, which suggests its great potential for diagnostic purposes. PMID:23202328

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



Colorimetric determination of pyrethroids based on core–shell Ag@SiO 2 nanoparticles  

Microsoft Academic Search

A highly sensitive colorimetric probe for pyrethroids based on surface amine-modified silver–silica core–shell nanoparticles (Ag@SiO2-NH2 NPs) was described here. The Ag@SiO2-NH2 NPs were characterized by transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) and ultraviolet–visible spectroscopy (UV–vis). The Ag@SiO2-NH2 NPs provided a simple and rapid strategy to detect pyrethroids and allowed a rapid quantitative assay of lambda-cyhalothrin (LC) down to

Yuling Li; Zhimin Cui; Dapeng Li; Haibing Li



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



Reliable Drosophila body fat quantification by a coupled colorimetric assay.  


Factors and mechanisms controlling lipometabolism homeostasis share a remarkable evolutionary conservation between humans and Drosophila flies. Accordingly, the Drosophila model has been successfully used to understand the pathophysiology of human metabolic diseases such as obesity. Body fat stores in species as different as humans and flies consist of neutral lipids, mainly triacylglycerols. Changes in body fat storage are a diagnostic phenotype of lipometabolism imbalances of genetic or environmental origin. Various methods have been developed to quantify Drosophila body fat storage. The most widely used method adopts a commercial coupled colorimetric assay designed for human serum triacylglycerol quantification, which is based on glycerol content determination after enzymatic conversion of glycerides into glycerol. The coupled colorimetric assay is compatible with large-scale genetic screen approaches and has been successfully applied to characterize central regulators of Drosophila lipometabolism. Recently, the applicability of the coupled colorimetric assay for Drosophila storage fat quantification has been questioned in principle. Here we compare the performance of the coupled colorimetric assay on Drosophila samples with thin layer chromatography, the "gold standard" in storage lipid analysis. Our data show that the presented variant of the coupled colorimetric assay reliably discriminates between lean and fat flies and allows robust, quick and cost-effective quantification of Drosophila body fat stores. PMID:21931614

Hildebrandt, Anja; Bickmeyer, Iris; Kühnlein, Ronald P



Direct-detection optical CDMA receiver with interference estimation and double optical hardlimiters  

Microsoft Academic Search

This paper proposes a new channel interference cancellation technique using interference estimation and double optical hardlimiters (DHL) for direct-detection optical code-division multiple-access (CDMA) systems. In the proposed system, when the output of the DHL is \\

Kenji Wakafuji; Tomoaki Ohtsuki



Respiratory Syncytial Virus Detection by Remel Xpect, Binax Now RSV, Direct Immunofluorescent Staining, and Tissue Culture  

Microsoft Academic Search

The performance characteristics of Xpect RSV (XP) and Binax Now RSV (BN) were compared to those of direct fluorescent-antibody staining and\\/or tissue culture for detection of respiratory syncytial virus (RSV) in nasopharyngeal aspirate and wash samples from children (n 110) and adults (n 66). The sensitivity, specificity, positive predictive value, and negative predictive value of XP were 75%, 98%, 95%,

Anita P. Borek; Susan H. Clemens; Valerie K. Gaskins; Deborah Z. Aird; Alexandra Valsamakis



Study of Super-resolution Direction Detection with Spatially Nonstationary Noise  

Microsoft Academic Search

This paper studied super-resolution direction detection of arbitrary spatial sensors array, with nonstationary spatial noise, i.e. a noise has a diagonal covariance matrix whose diagonal elements have unequal noise power. An improvement of covariance matrix difference approach was made. The proposed algorithm conducts the difference between the averaging covariance matrix and its transform matrix to eliminate the noise effects which

Xiumin Shi; Liang Chen



Direct and long-term detection of gene doping in conventional blood samples  

Microsoft Academic Search

The misuse of somatic gene therapy for the purpose of enhancing athletic performance is perceived as a coming threat to the world of sports and categorized as ‘gene doping’. This article describes a direct detection approach for gene doping that gives a clear yes-or-no answer based on the presence or absence of transgenic DNA in peripheral blood samples. By exploiting

T Beiter; M Zimmermann; A Fragasso; J Hudemann; A M Niess; M Bitzer; U M Lauer; P Simon



Direct Detection of Nocardia spp. in Clinical Samples by a Rapid Molecular Method  

PubMed Central

We developed a 16S PCR-based assay for the rapid detection of Nocardia spp. directly from human clinical samples. The applicability of the assay was confirmed by using 18 samples from patients with nocardiosis as diagnosed by conventional cultures and 20 clinical samples from patients with confirmed tuberculosis used as negative controls.

Couble, Andree; Rodriguez-Nava, Veronica; de Montclos, Michele Perouse; Boiron, Patrick; Laurent, Frederic



Digital radiography system using a new direct-detection flat panel detector and its system performance  

Microsoft Academic Search

We developed a digital radiography (DR) system using a new amorphous selenium (a-Se) based direct-detection flatpanel detector which has a pixel pitch of 0.168mm, a fill factor of 83%, and a total active imaging area is 17\\

Jong-Hwan Park; Won-Suk Kang; Byung-Su Shin; Hyun-Seung Kang



Direct-detection WiMax orthogonal frequency division multiplexing over fiber access networks  

NASA Astrophysics Data System (ADS)

We have investigated novel optical-wireless architecture to provide WiMax orthogonal frequency division multiplexing (OFDM) signals over fiber access network by simulation. The proposed architecture utilizes direct detection for WiMax OFDM. The simulation results show that it can transmit a high capacity WiMax OFDM signal over 250km SMF successfully.

He, Jing; Su, Jinshu; Huang, Yuan; Liu, Hao



Apparatus for detecting rate and direction of rotation of tethered bacterial cells  

Microsoft Academic Search

A simple apparatus was constructed for detecting the rate and the direction of rotation of tethered bacterial cells. Images of the tethered cells from a dark-field optical microscope were recorded by a TV camera and VTR. The playback image of a rotating cell was passed through an optical system consisting of an image splitter and two graded filters and then

Syoyu Kobayasi; Kayo Maeda; Yasuo Imae



Detectability of experimental peri-implant cancellous bone lesions using conventional and direct digital radiography  

Microsoft Academic Search

Background: The aim of this study was to compare the diagnostic performance obtained from direct digital radiographic images (in their original form and after applying a grey-scale inversion) and conventional film in the detection of artificial peri- implant cancellous bone lesions. Methods: Four titanium implants were placed into the cancellous bone of a dry mandible and increasingly larger bone defects

A. Kavadella; A. Karayiannis; K. Nicopoulou-Karayianni



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



Direct Detection of 16S rRNA in Soil Extracts by Using Oligonucleotide Microarrays  

SciTech Connect

ABSTRACT-We report on the development and validation of simple microarray method for the direct detection of intact 16S rRNA from un-purified soil extracts. Total RNA from Geobacter chapellei and Desulfovibrio desulfuricans was hybridized to an oligonculeotide array consisting of universal and species-specific 16S rRNA probes...

Small, Jack A.; Call, Douglas R.; Brockman, Fred J.; Straub, Tim M.; Chandler, Darrell P.



16-level differential phase shift keying (D16PSK) in direct detection optical communication systems.  


Optical 16-level differential phase shift keying (D16PSK) carrying four bits for every symbol is proposed for direct detection optical communication systems. Transmitter and receiver schematics are presented, and the receiver sensitivity is discussed. We numerically investigate the impact of chromatic dispersion and nonlinear transmission degradations. PMID:19529420

Sambaraju, Rakesh; Tokle, Torger; Bevensee Jensen, Jesper; Jeppesen, Palle



Channeling in direct dark matter detection III: channeling fraction in CsI crystals  

NASA Astrophysics Data System (ADS)

The channeling of the ion recoiling after a collision with a WIMP changes the ionization signal in direct detection experiments, producing a larger signal scintillation or ionization than otherwise expected. We give estimates of the fraction of channeled recoiling ions in CsI crystals using analytic models produced since the 1960's and 70's to describe channeling and blocking effects.

Bozorgnia, Nassim; Gelmini, Graciela B.; Gondolo, Paolo



In-line interferometer for direction-sensitive displacement measurements by optical feedback detection  

Microsoft Academic Search

We demonstrate a compact in-line interferometer for direction-sensitive displacement measurement by optical feedback detection with a semiconductor laser (SL) light source. Two reflected beams from a semitransparent reference mirror and a reflecting test object interfere in the SL medium, causing a variation in its output power. The reference mirror is located between the SL output facet and the test object.

Alvarado Tarun; Julius Jecong; Caesar Saloma



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


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



Forecast constraints on inflation from combined CMB and gravitational wave direct detection experiments  

SciTech Connect

We study how direct detection of the inflationary gravitational wave background constrains inflationary parameters and complements CMB polarization measurements. The error ellipsoids calculated using the Fisher information matrix approach with Planck and the direct detection experiment, Big Bang Observer (BBO), show different directions of parameter degeneracy, and the degeneracy is broken when they are combined. For a slow-roll parametrization, we show that BBO could significantly improve the constraints on the tensor-to-scalar ratio compared with Planck alone. We also look at a quadratic and a natural inflation model. In both cases, if the temperature of reheating is also treated as a free parameter, then the addition of BBO can significantly improve the error bars. In the case of natural inflation, we find that the addition of BBO could even partially improve the error bars of a cosmic variance-limited CMB experiment.

Kuroyanagi, Sachiko [Department of Physics, Nagoya University, Chikusa, Nagoya 464-8602 (Japan); Gordon, Christopher [Astrophysics Department, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom); Silk, Joseph [Astrophysics Department, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom); Institut d'Astrophysique, 98bis Boulevard Arago, Paris 75014 (France); Sugiyama, Naoshi [Department of Physics, Nagoya University, Chikusa, Nagoya 464-8602 (Japan); Institute for Physics and Mathematics of the Universe, University of Tokyo, 5-1-5 Kashiwa-no-ha, Kashiwa City, Chiba 277-8582 (Japan)



Energy dependence of direct detection cross section for asymmetric mirror dark matter  

SciTech Connect

In a recent paper, four of the present authors proposed a class of dark matter models where generalized parity symmetry leads to equality of dark matter abundance with baryon asymmetry of the Universe and predicts dark matter mass to be around 5 GeV. In this paper, we explore how this model can be tested in direct search experiments. In particular, we point out that if the dark matter happens to be the mirror neutron, the direct detection cross section has the unique feature that it increases at low recoil energy unlike the case of conventional weakly interacting massive particles. It is also interesting to note that the predicted spin-dependent scattering could make significant contribution to the total direct detection rate, especially for light nucleus. With this scenario, one could explain recent DAMA and CoGeNT results.

An Haipeng; Chen Shaolong; Mohapatra, Rabindra N. [Maryland Center for Fundamental Physics and Department of Physics, University of Maryland, College Park, Maryland 20742 (United States); Nussinov, Shmuel [Tel Aviv University, Tel Aviv (Israel) and Chapman Schmid College of Science, Orange, California 92866 (United States); Zhang Yue [Abdus Salam International Center for Theoretical Physics, Strada Costiera 11, I-34014 Trieste (Italy)



The AMIDAS Website: An Online Tool for Direct Dark Matter Detection Experiments  

SciTech Connect

Following our long-erm work on development of model-independent data analysis methods for reconstructing the one-dimensional velocity distribution function of halo WIMPs as well as for determining their mass and couplings on nucleons by using data from direct Dark Matter detection experiments directly, we combined the simulation programs to a compact system: AMIDAS (A Model-Independent Data Analysis System). For users' convenience an online system has also been established at the same time. AMIDAS has the ability to do full Monte Carlo simulations, faster theoretical estimations, as well as to analyze (real) data sets recorded in direct detection experiments without modifying the source code. In this article, I give an overview of functions of the AMIDAS code based on the use of its website.

Shan, Chung-Lin [School of Physics and Astronomy, Seoul National University, Seoul 151-747 (Korea, Republic of)



Optic disc detection from normalized digital fundus images by means of a vessels' direction matched filter.  


Optic disc (OD) detection is a main step while developing automated screening systems for diabetic retinopathy. We present in this paper a method to automatically detect the position of the OD in digital retinal fundus images. The method starts by normalizing luminosity and contrast through out the image using illumination equalization and adaptive histogram equalization methods respectively. The OD detection algorithm is based on matching the expected directional pattern of the retinal blood vessels. Hence, a simple matched filter is proposed to roughly match the direction of the vessels at the OD vicinity. The retinal vessels are segmented using a simple and standard 2-D Gaussian matched filter. Consequently, a vessels direction map of the segmented retinal vessels is obtained using the same segmentation algorithm. The segmented vessels are then thinned, and filtered using local intensity, to represent finally the OD-center candidates. The difference between the proposed matched filter resized into four different sizes, and the vessels' directions at the surrounding area of each of the OD-center candidates is measured. The minimum difference provides an estimate of the OD-center coordinates. The proposed method was evaluated using a subset of the STARE project's dataset, containing 81 fundus images of both normal and diseased retinas, and initially used by literature OD detection methods. The OD-center was detected correctly in 80 out of the 81 images (98.77%). In addition, the OD-center was detected correctly in all of the 40 images (100%) using the publicly available DRIVE dataset. PMID:18270057

Youssif, A R; Ghalwash, A Z; Ghoneim, A R



Direct detection of unamplified spring viraemia of carp virus RNA using unmodified gold nanoparticles.  


Spring viraemia of carp (SVC) is a viral disease that mainly affects carp Cyprinus carpio and other cyprinid fish, causing severe economic losses. Rapid detection and identification of spring viraemia of carp virus (SVCV) is crucial for effective disease management. Recent advances in nanoscience are having a significant impact on many scientific fields, especially biodiagnostics, where a number of nanoparticle-based assays have been introduced for biomolecular detection. Single- and double-stranded oligonucleotides can be adsorbed on gold nanoparticles (AuNPs) in colloidal solution under certain conditions. We exploited this phenomenon to develop a specific hybridization assay for direct detection of SVCV-RNA without prior amplification. The result of the hybridization process could be detected visually within 1 min when the colour of the reaction mixture changed from red to blue (positive reaction) or remains red (negative). The lower detection limit of the assay was estimated to be 10-3 TCID50 ml-1 SVCV-RNA, and it has the feasibility to detect the target virus-RNA in clinical specimens without previous amplification. In order to obtain an indication of the assay's performance on clinical samples we compared the optimized assay with nested RT-PCR in detection of SVCV-RNA in infected fish samples. The concordance of the 2 methods was defined as 100% when compared to nested RT-PCR positive and negative samples. The SVC-AuNPs assay requires only 15 min, eliminates the need for thermal cycling or detection instruments and is a specific and rapid tool for detection of SVCV-RNA directly from clinical samples. PMID:22885508

Saleh, Mona; Soliman, Hatem; Schachner, Oskar; El-Matbouli, Mansour



Impedimetric immunosensor for human serum albumin detection on a direct aldehyde-functionalized silicon nitride surface.  


In this work we report the fabrication and characterization of a label-free impedimetric immunosensor based on a silicon nitride (Si(3)N(4)) surface for the specific detection of human serum albumin (HSA) proteins. Silicon nitride provides several advantages compared with other materials commonly used, such as gold, and in particular in solid-state physics for electronic-based biosensors. However, few Si(3)N(4)-based biosensors have been developed; the lack of an efficient and direct protocol for the integration of biological elements with silicon-based substrates is still one of its the main drawbacks. Here, we use a direct functionalization method for the direct covalent binding of monoclonal anti-HSA antibodies on an aldehyde-functionalized Si-p/SiO(2)/Si(3)N(4) structure. This methodology, in contrast with most of the protocols reported in literature, requires less chemical reagents, it is less time-consuming and it does not need any chemical activation. The detection capability of the immunosensor was tested by performing non-faradaic electrochemical impedance spectroscopy (EIS) measurements for the specific detection of HSA proteins. Protein concentrations within the linear range of 10(-13)-10(-7) M were detected, showing a sensitivity of 0.128 ? ?M(-1) and a limit of detection of 10(-14) M. The specificity of the sensor was also addressed by studying the interferences with a similar protein, bovine serum albumin. The results obtained show that the antibodies were efficiently immobilized and the proteins detected specifically, thus, establishing the basis and the potential applicability of the developed silicon nitride-based immunosensor for the detection of proteins in real and more complex samples. PMID:22365119

Caballero, David; Martinez, Elena; Bausells, Joan; Errachid, Abdelhamid; Samitier, Josep



Diurnal and Annual Variations of Directional Detection Rates of Dark Matter  

NASA Astrophysics Data System (ADS)

Direction-sensitive direct detection of weakly interacting massive particles (WIMPs) as dark matter would provide an unambiguous non-gravitational signature of dark matter. The diurnal variation of dark matter signal due to Earth's rotation around its own axis can be a significant signature for Galactic WIMPs. Because of a particular orientation of Earth's axis of rotation with respect to the WIMP wind direction, the apparent direction of WIMP wind as observed at a detector can alter widely in a day. In this work, we calculate the directional detection rates with their daily and yearly modulations in Earth-bound dark matter experiments considering detailed features of the geometry and dynamics of the Earth-Sun system along with the solar motion in a Galactic frame. A separate halo model, namely the dark disk model other than the usual standard halo model for dark matter halo, is also considered and the results for two models are compared. We demonstrate the results for two types of gas detectors, namely DRIFT (target material CS2) and NEWAGE (target material CF4), which use Time Projection Chamber techniques for measuring directionality of the recoil nucleus. The WIMP mass and recoil energy dependence of the daily variation of event rates are computed for a specific detector, and the sensitive ranges of mass and recoil energies for the considered detector are probed.

Bandyopadhyay, Abhijit; Majumdar, Debasish



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



MIL-53(Fe): A Metal-Organic Framework with Intrinsic Peroxidase-Like Catalytic Activity for Colorimetric Biosensing.  


Showing MOFs' true colors: An iron-based metal-organic framework, MIL-53(Fe), is explored as an enzyme mimic with intrinsic peroxidase-like activity. MIL-53(Fe) can catalyze the oxidation of different peroxidase substrates in the presence of H2 O2 (see graphic; TMB=3,3',5,5'-tetramethylbenzidine, OPD=o-phenylenediamine), providing a new and simple colorimetric detection of hydrogen peroxide and ascorbic acid. PMID:24150880

Ai, Lunhong; Li, Lili; Zhang, Caihong; Fu, Jian; Jiang, Jing



Characterization of Methyltransferase Properties of Escherichia coli YabC Protein with an Enzyme-Coupled Colorimetric Assay  

Microsoft Academic Search

An enzyme-coupled colorimetric assay for S-adenosylmethionine-dependent methyltransferase (MT) was established to characterize the enzymatic identity of YabC protein from Escherichia coli. Results showed that the MT activity of YabC is able to be effectively detected with this coupling assay system when filamentous cell lysates from an S-adenosylmethionine synthetase mutant, MEW402metK84, were employed as the source of methylation target, whereas no

Jingsong Gu; Chunjiang Ye



Rapid Determination of Methicillin Resistance among Staphylococcus aureus Clinical Isolates by Colorimetric Methods  

PubMed Central

In the present study, the effectiveness of a rapid and colorimetric nitrate reductase analysis (NRA) method and resazurin microplate assay (REMA) for rapid determination of methicillin resistance among Staphylococcus aureus was investigated. A total of 275 clinical isolates of S. aureus were included in the present study. Among these isolates, 151 had the mecA gene and were resistant to methicillin. The remaining 124 isolates were methicillin susceptible and did not have the mecA gene. Cefoxitin MICs of all isolates were detected by NRA, REMA, and reference broth microdilution methods. Category and essential agreement were determined as 100% and 99.6%, respectively, comparing both NRA and REMA with the reference method. No minor, major, or very major discrepancy was observed for either of the methods. The time necessary to have the MIC results was 5 h for NRA, whereas it was 6 h for REMA. Early detection of MRSA is an important public health concern, and the results of this study showed that both of the colorimetric methods are easy to perform and save time in the determination of MRSA. These methods have a potential use for early detection of MRSA for laboratories unable to use molecular techniques.



Rapid determination of methicillin resistance among Staphylococcus aureus clinical isolates by colorimetric methods.  


In the present study, the effectiveness of a rapid and colorimetric nitrate reductase analysis (NRA) method and resazurin microplate assay (REMA) for rapid determination of methicillin resistance among Staphylococcus aureus was investigated. A total of 275 clinical isolates of S. aureus were included in the present study. Among these isolates, 151 had the mecA gene and were resistant to methicillin. The remaining 124 isolates were methicillin susceptible and did not have the mecA gene. Cefoxitin MICs of all isolates were detected by NRA, REMA, and reference broth microdilution methods. Category and essential agreement were determined as 100% and 99.6%, respectively, comparing both NRA and REMA with the reference method. No minor, major, or very major discrepancy was observed for either of the methods. The time necessary to have the MIC results was 5 h for NRA, whereas it was 6 h for REMA. Early detection of MRSA is an important public health concern, and the results of this study showed that both of the colorimetric methods are easy to perform and save time in the determination of MRSA. These methods have a potential use for early detection of MRSA for laboratories unable to use molecular techniques. PMID:22518854

Coban, Ahmet Yilmaz



Direct detection of Salmonella spp. in estuaries by using a DNA probe.  

PubMed Central

A method for direct detection of Salmonella spp. in water was developed by using a commercially available DNA probe. Particulate DNA was extracted from 500- to 1,500-ml water samples collected from New York Harbor and Chesapeake Bay and used as a substrate for a salmonella-specific DNA probe in dot blot assays. The method detected salmonellae in water samples from 12 of 16 sites, including 6 sites where salmonellae could not be cultured. The specificity of the probe was evaluated, and cross-hybridization, although negligible, was used to set detection limits for the assay. Salmonella DNA bound the probe quantitatively, and from these results Salmonella DNA in the total particulate DNA in environmental samples could be estimated. The data obtained in this study indicate that Salmonella spp. often are not detected in water samples by culture methods, even when they are present in significant numbers. Images

Knight, I T; Shults, S; Kaspar, C W; Colwell, R R



Impact of dark matter microhalos on signatures for direct and indirect detection  

SciTech Connect

Detecting dark matter as it streams through detectors on Earth relies on knowledge of its phase space density on a scale comparable to the size of our Solar System. Numerical simulations predict that our galactic halo contains an enormous hierarchy of substructures, streams and caustics, the remnants of the merging hierarchy that began with tiny Earth-mass microhalos. If these bound or coherent structures persist until the present time, they could dramatically alter signatures for the detection of weakly interacting elementary particle dark matter. Using numerical simulations that follow the coarse grained tidal disruption within the Galactic potential and fine grained heating from stellar encounters, we find that microhalos, streams, and caustics have a negligible likelihood of impacting direct detection signatures implying that dark matter constraints derived using simple smooth halo models are relatively robust. We also find that many dense central cusps survive, yielding a small enhancement in the signal for indirect detection experiments.

Schneider, Aurel; Moore, Ben [Institute for Theoretical Physics, University of Zurich, Zurich (Switzerland); Krauss, Lawrence [Institute for Theoretical Physics, University of Zurich, Zurich (Switzerland); School of Earth and Space Exploration and Department of Physics, Arizona State University, PO Box 871404, Tempe, Arizona 85287 (United States)



Directional filter banks for detecting un-patterned TFT-LCD defect  

NASA Astrophysics Data System (ADS)

The thin film transistor liquid crystal display (TFT-LCD) has become an actively used front of panel display technology with an increasing market. Intrinsically there is a region of non uniformity with low contrast that to human eye is perceived as a defect. Because the grey-level difference between the defect and the background is small, the conventional edge detection techniques are hardly applicable to detect these low contrast defects. Although several effort were dedicated in classifying the patterned TFT-LCD defects, only few researches were conducted on detecting the unpatterned TFT-LCD defects that accounts for approximately 15% of all defects produced during the manufacturing stages. This paper proposes a detection method for the un-patterned TFT-LCD defects by using the directional filter bank (DFB), Shen-Castan filter and maximum Feret's diameter. The effectiveness of the proposed method is tested through the experiment using real TFT-LCD panel images.

Park, No Kap; Kim, Hye Won; Yoo, Suk In



Using a large area CMOS APS for direct chemiluminescence detection in Western blotting electrophoresis  

NASA Astrophysics Data System (ADS)

Western blotting electrophoretic sequencing is an analytical technique widely used in Functional Proteomics to detect, recognize and quantify specific labelled proteins in biological samples. A commonly used label for western blotting is Enhanced ChemiLuminescence (ECL) reagents based on fluorescent light emission of Luminol at 425nm. Film emulsion is the conventional detection medium, but is characterized by non-linear response and limited dynamic range. Several western blotting digital imaging systems have being developed, mainly based on the use of cooled Charge Coupled Devices (CCDs) and single avalanche diodes that address these issues. Even so these systems present key drawbacks, such as a low frame rate and require operation at low temperature. Direct optical detection using Complementary Metal Oxide Semiconductor (CMOS) Active Pixel Sensors (APS)could represent a suitable digital alternative for this application. In this paper the authors demonstrate the viability of direct chemiluminescent light detection in western blotting electrophoresis using a CMOS APS at room temperature. Furthermore, in recent years, improvements in fabrication techniques have made available reliable processes for very large imagers, which can be now scaled up to wafer size, allowing direct contact imaging of full size western blotting samples. We propose using a novel wafer scale APS (12.8 cm×13.2 cm), with an array architecture using two different pixel geometries that can deliver an inherently low noise and high dynamic range image at the same time representing a dramatic improvement with respect to the current western blotting imaging systems.

Esposito, Michela; Newcombe, Jane; Anaxagoras, Thalis; Allinson, Nigel M.; Wells, Kevin



Pyrrole-Based Anion Sensors, Part I: Colorimetric Sensors  

NASA Astrophysics Data System (ADS)

This chapter focuses on chemo-sensing aspects of pyrrole and oligopyrrole-based colorimetric receptors for anions. Since pyrroles can play the role of a receptor as well as a signal transducer very efficiently and because of the focus on anion sensing, they can be organized following the modes of signal transduction such as colorimetry, fluorescence, and electrochemistry rather than structural features of the receptors. This chapter focuses on colorimetric sensors and in particular those based on pyrrole, polypyrrole, and pyrrole benzo-analogs, i.e., indole and carbazole-based sensors for anions.

Anzenbacher, Pavel


Colorimetric Determination of Pure Mg2+-dependent Phosphatidate Phosphatase Activity  

PubMed Central

The malachite green-molybdate reagent was used for a colorimetric assay of pure Mg2+-dependent phosphatidate phosphatase activity. This enzyme plays a major role in fat metabolism. Enzyme activity was linear with time and protein concentration, and with the concentration of water-soluble dioctanoyl phosphatidate. The colorimetric assay was used to examine enzyme inhibition by phenylglyoxal, propranolol, and dimethyl sulfoxide. Pure enzyme and a water-soluble phosphatidate substrate were required for the assay, which should be applicable to a well-defined large-scale screen of Mg2+-dependent phosphatidate phosphatase inhibitors (or activators).

Havriluk, Tara; Lozy, Fred; Siniossoglou, Symeon; Carman, George M.



Colorimetric Quantification and in Situ Detection of Collagen  

ERIC Educational Resources Information Center

|A simple multidisciplinary and inexpensive laboratory exercise is proposed, in which the undergraduate student may correlate biochemical and anatomical findings. The entire practical session can be completed in one 2.5-3 hour laboratory period, and consists of the quantification of collagen and total protein content from tissue sections--without…

Esteban, Francisco J.; del Moral, Maria L.; Sanchez-Lopez, Ana M.; Blanco, Santos; Jimenez, Ana; Hernandez, Raquel; Pedrosa, Juan A.; Peinado, Maria A.



Colorimetric blood-gas monitoring sensors  

NASA Astrophysics Data System (ADS)

Colorimetric fiber optic sensors have been developed for measuring the pH and pCO2 of blood. These sensors are fabricated using a single 125 micrometers diameter optical fiber. Located at the distal end of the fiber is a capsule that contains a pH sensitive dye. The pCO2 sensor is fabricated from a pH sensor with the addition of a salt, bicarbonate, and the encapsulation with an ion impermeable gas permeable membrane. The distal end of the capsule is terminated with a reflective surface. The reflective surface can either be a polished metallic surface or, in this case, a TiO2 impregnated epoxy. The disposable sensor mates with an optical connector that contains two optical fibers of the same size as the disposable sensor. The two fibers within the optical cable provide a light path for both the antegrade and retrograde optical signals. These fibers are terminated at either the LED source or the detector. A prototype sensor assembly that incorporates the measurement of three physiological parameters (pH, pCO2, and sO2) has been demonstrated to fit within a standard 20 gauge arterial catheter, typically used for radial artery blood pressure monitoring, without significant damping of the blood pressure waveform. The pH sensor has a range of 6.9 - 7.8 with a precision of 0.01 pH units and the pCO2 sensor has a range of 15 - 95 mm Hg with a precision of 3 mm Hg. The long term drift pH drift is less than 0.01 pH unit per 8 hours and the pCO2 drift is less than 1 mm Hg per 8 hours. Sensor performance in the canine has demonstrated that the pH sensor is accurate to within +/- 0.03 pH units and the pCO2 sensor is accurate to within +/- 3 mm Hg when compared to a typical blood gas analyzer.

Proctor, Keith J.; Seifert, George P.



Direct SUSY dark matter detection-theoretical rates due to the spin  

NASA Astrophysics Data System (ADS)

The recent WMAP data have confirmed that exotic dark matter together with the vacuum energy (cosmological constant) dominate in the flat Universe. Thus direct dark matter detection, consisting of detecting the recoiling nucleus, is central to particle physics and cosmology. Supersymmetry provides a natural dark matter candidate, the lightest supersymmetric particle (LSP). The relevant cross sections arise out of two mechanisms: (i) the coherent mode, due to the scalar interaction and (ii) the spin contribution arising from the axial current. In this paper we will focus on the spin contribution, which is expected to dominate for light targets. For both modes it is possible to obtain detectable rates, but in most models the expected rates are much lower than the present experimental goals. So one should exploit two characteristic signatures of the reaction, namely the modulation effect and in directional experiments the correlation of the event rates with the sun's motion. In standard non-directional experiments the modulation is small, less than 2 per cent. In the case of the directional event rates we would like to suggest that the experiments exploit two features of the process, which are essentially independent of the SUSY model employed, namely: (1) the forward backward asymmetry, with respect to the sun's direction of motion, is very large and (2) the modulation is much larger, especially if the observation is made in a plane perpendicular to the sun's velocity. In this case the difference between maximum and minimum can be larger than 40 per cent and the phase of the earth at the maximum is direction dependent.

Vergados, J. D.



Direct detection and isolation of plasmid-bearing virulent serotypes of Yersinia enterocolitica from various foods.  

PubMed Central

A procedure was developed for direct detection, isolation, and maintenance of plasmid-bearing virulent serotypes of Yersinia enterocolitica from different food sources. Plasmid-bearing virulent strains of Y. enterocolitica representing five serotypes were simultaneously detected and isolated from enriched swab samples of artificially contaminated pork chops, ground pork, cheese, and zucchini, using Congo red binding and low-calcium-response tests. The method was also effective in isolating plasmid-bearing virulent strains of Y. enterocolitica from naturally contaminated porcine tongues. Virulence of the strains isolated from these foods was confirmed by PCR, the expression of plasmid-associated phenotypes, and mouse pathogenicity.

Bhaduri, S; Cottrell, B



Image Covariance and Lesion Detectability in Direct Fan-Beam X-Ray Computed Tomography  

PubMed Central

We consider noise in computed tomography images that are reconstructed using the classical direct fan-beam filtered backprojection algorithm, from both full and short-scan data. A new, accurate method for computing image covariance is presented. The utility of the new covariance method is demonstrated by its application to the implementation of a channelized Hotelling observer for a lesion detection task. Results from the new covariance method and its application to the channelized Hotelling observer are compared with results from Monte Carlo Simulations. In addition, the impact of a bowtie filter and x-ray tube current modulation on reconstruction noise and lesion detectability are explored for full-scan reconstruction.

Wunderlich, Adam; Noo, Frederic



Rapid and unbiased colorimetric quantification of nitrite and ammonium ions released from 2,4,6-trinitrotoluene during biodegradation studies: Eliminating interferences  

Microsoft Academic Search

Worldwide contamination of soils and groundwater by 2,4,6-trinitrotoluene (TNT) has drawn considerable attention to bioremediation solutions. To evaluate the environmental relevance of a biodegradation process or to discover new TNT degrader microorganisms, effective and reliable monitoring strategies are essential, including the sensitive detection of inorganic nitrogen species released from TNT. In this study we describe improved colorimetric methods for a

Ben Stenuit; Spiros N. Agathos



Detection of event-related potentials for development of a direct brain interface.  


The study presented here is part of an ongoing effort to develop a direct brain interface based on detection of event-related potentials (ERPs). In a study presented in a companion article, averaged ERP templates were identified from electrocorticograms recorded during repetition of voluntary motor actions. Here the authors report on the detection of individual motor ERPs within the electrocorticogram using cross-correlation. An averaged ERP template was created from the first half of each electrocorticogram and then cross-correlated with the continuous electrocorticogram from the second half. Points where the cross-correlation value exceeded an experimentally determined detection threshold were considered to be detection points. A detection point was considered to be a valid "hit" if it occurred between 1 second before and 0.25 second after the recorded time of a voluntary action. The difference between the hit and false-positive percentages (HF-difference) was used as a metric of detection accuracy. HF-differences greater than 90 were found for 5 of 15 subjects, HF-differences greater than 75 were found for 8 of 15 subjects, and HF-differences greater than 50 were found for 12 of 15 subjects. The three other subjects with HF-differences less than 50 had electrode locations not well suited for recording movement-related ERPs. Recordings from sensorimotor and supplementary motor areas produced the highest yield of channels with HF-difference greater than 50; however, a number of channels with good performance were found in other areas as well. The results demonstrate the likely prospect of using ERP detection as the basis of a single-switch direct brain interface and that furthermore, there is a good possibility of obtaining multiple control channels using this approach. PMID:10576227

Huggins, J E; Levine, S P; BeMent, S L; Kushwaha, R K; Schuh, L A; Passaro, E A; Rohde, M M; Ross, D A; Elisevich, K V; Smith, B J



Direct detection of DNA methylation during single-molecule, real-time sequencing  

PubMed Central

We describe the direct detection of DNA methylation, without bisulfite conversion, through single-molecule real-time (SMRT) sequencing. In SMRT sequencing, DNA polymerases catalyze the incorporation of fluorescently labeled nucleotides into complementary nucleic acid strands. The arrival times and durations of the resulting fluorescence pulses yield information about polymerase kinetics and allow direct detection of modified nucleotides in the DNA template, including N6-methyladenosine, 5-methylcytosine, and 5-hydroxymethylcytosine. Measurement of polymerase kinetics is an intrinsic part of SMRT sequencing and does not adversely affect determination of the primary DNA sequence. The various modifications affect polymerase kinetics differently, allowing discrimination between them. We utilize these kinetic signatures to identify adenosine methylation in genomic samples and show that, in combination with circular consensus sequencing, they can enable single-molecule identification of epigenetic modifications with base-pair resolution. This method is amenable to long read lengths and will likely enable mapping of methylation patterns within even highly repetitive genomic regions.

Flusberg, Benjamin A.; Webster, Dale; Lee, Jessa; Travers, Kevin; Olivares, Eric; Clark, Tyson A.; Korlach, Jonas; Turner, Stephen W.



Performance of random diagonal code for OCDMA systems using new spectral direct detection technique  

NASA Astrophysics Data System (ADS)

This paper studies the performance of random diagonal (RD) code for spectral-amplitude coding OCDMA (SAC-OCDMA) system using a newly proposed spectral direct detection technique. RD code is constructed using code segment and data segment. One of the important properties of this code is that the cross correlation at data segment is always zero, which means that phase intensity induced noise (PIIN) is reduced. The weight for the RD code can be any number greater than three. By comparing the theoretical and simulation results taken from the commercial optical systems simulator “OptSim,” we show that the proposed new spectral direct detection technique utilizing RD code considerably improves the performance compared with the conventional SAC complementary subtraction technique.

Fadhil, Hilal Adnan; Aljunid, S. A.; Ahmad, R. B.



A DEAP & CLEAN Program for the Direct Detection of Dark Matter  

Microsoft Academic Search

On behalf of the DEAP\\/CLEAN Collaboration, I will discuss our efforts to exploit liquid argon (LAr) and liquid neon (LNe) in a single-phase, scintillation detector for the direct detection of dark matter and low-energy solar neutrinos. The unique properties of LAr and LNe allow for a conceptually simple, economic, and scalable detector when operated in the single phase. Target exchange

Andrew Hime



Direct detection of the interaction of tiny analytes with receptors using an advanced plasmonic biosensor  

Microsoft Academic Search

The interaction between tiny-molecular-weight analytes and receptors can be detected directly using advanced plasmonic biosensors. This paper proposes a plasmonic biosensor with Au nanoclusters embedded in a dielectric film. The sensor uses the attenuated total reflection (ATR) method to excite both the surface plasmons (SPs) and the particle plasmons (PPs). The local electro-magnetic (EM) field is enhanced by controlling the

Fan-Ching Chien; K.-T. Huang; C.-Y. Lin; Shean-Jen Chen



Direct detection of primordial gravitational waves in a BSI inflationary model  

NASA Astrophysics Data System (ADS)

We investigate the possibility for a direct detection by future space interferometers of the stochastic gravitational wave (GW) background generated during the inflationary stage in a class of viable ?CDM BSI models. At frequencies around 10-3 Hz, maximal values ?gw(?)~3x10-15 are found, an improvement of about one order of magnitude compared to single-field, slow-roll inflationary models. This is presumably not sufficient in order to be probed in the near future.

Polarski, David



Direct-detection polarization division multiplexed orthogonal frequency-division multiplexing transmission systems without polarization tracking.  


We experimentally demonstrate a direct-detection polarization division multiplexed (PDM) orthogonal frequency-division multiplexing (OFDM) scheme without dynamic polarization tracking. Simply using a polarization-diverse receiver, the proposed multiple-input multiple-output assisted system can achieve bit-error rate of 10(-) over all possible received states of polarization. Moreover, 50 Gbps PDM-OFDM transmission over 100 km single-mode fiber is successfully demonstrated without dispersion-induced penalty. PMID:23258008

Wang, Chih-Yun; Wei, Chia-Chien; Lin, Chun-Ting; Chi, Sien



Block-wise phase switching for double-sideband direct detected optical OFDM signals.  


We propose phase switching for either main-carrier or subcarriers of two consecutive signal blocks to achieve fading-free double-sideband direct-detection (DD). The proposed approach has twice of the electrical spectral efficiency (SE) of offset OFDM, and the same electrical SE as single-side band (SSB) OFDM. With this scheme, 40-Gb/s DD-OOFDM is successfully received over 80-km SSMF with single polarization and single detector. PMID:23736596

Chen, Xi; Li, An; Che, Di; Hu, Qian; Wang, Yifei; He, Jiayuan; Shieh, William



Multilevel coding in Mary DPSK\\/differential QAM high-speed optical transmission with direct detection  

Microsoft Academic Search

A bandwidth- and power-efficient modulation scheme using M-ary differential phase-shift keying (DPSK)\\/differential quadrature amplitude modulation (DQAM) and low-density parity-check (LDPC) codes as component codes in a multilevel coding (MLC) is proposed for optical transmission systems with direct detection. An MLC scheme with 2 b\\/s\\/Hz spectral efficiency based on block-circulant component codes provides the coding gain of 12.3 dB when compared

Ivan B. Djordjevic; Bane Vasic



Evaluation of the AMPLICOR CMV test for direct detection of cytomegalovirus in plasma specimens.  

PubMed Central

We evaluated the AMPLICOR CMV test (PCR) for the direct detection of cytomegalovirus in plasma. Sixty-eight specimens were involved for the comparison between the AMPLICOR test and the antigenemia assay. The sensitivities, specificities, and positive and negative predictive values were 97.1, 100, 100, and 97.1%, respectively, for the AMPLICOR test and 79.4, 100, 100, and 82.9%, respectively, for the antigenemia assay.

Hiyoshi, M; Tagawa, S; Takubo, T; Tanaka, K; Nakao, T; Higeno, Y; Tamura, K; Shimaoka, M; Fujii, A; Higashihata, M; Yasui, Y; Kim, T; Hiraoka, A; Tatsumi, N



An improved ELISA for the detection of serum antibodies directed against classical swine fever virus  

Microsoft Academic Search

The complex-trapping-blocking (CTB) ELISA for detection of antibodies against classical swine fever virus (CSFV) using two monoclonal antibodies (mAbs) directed against envelope glycoprotein E2, has been improved using recombinant CSFV E2-antigen. The newly developed Ceditest ELISA for CSFV-Ab is a modification of the CTB-ELISA as described by Wensvoort et al. (1988) and Bloemraad et al. (1993). The old CTB-ELISA format

E. O. Colijn; M. Bloemraad; G. Wensvoort



Zooming in on light relic neutralinos by direct detection and measurements of galactic antimatter  

Microsoft Academic Search

The DAMA Collaboration has recently analyzed its data of the extensive WIMP direct search (DAMA\\/NaI) which detected an annual modulation, by taking into account the channeling effect which occurs when an ion traverses a detector with a crystalline structure. Among possible implications, this Collaboration has considered the case of a coherent weakly interacting massive particle (WIMP)-nucleus interaction and then derived

A. Bottino; F. Donato; N. Fornengo; S. Scopel



Direct detection of x-rays for protein crystallography employing a thick, large area CCD  

Microsoft Academic Search

This invention relates to an apparatus and method for directly determining the crystalline structure of a protein crystal. The crystal is irradiated by a finely collimated x-ray beam. The interaction of the x-ray beam with the crystal produces scattered x-rays. These scattered x-rays are detected by means of a large area, thick CCD which is capable of measuring a significant

M. Atac; T. McKay




Microsoft Academic Search

A major challenge with single-nucleotide polymorphism (SNP) fingerprinting of bacteria and higher organisms is the combination of genome-wide screenings with the potential of multiplexing and accurate SNP detection. Single-nucleotide extension by the minisequencing principle represents a technology that both is highly accurate and enables multiplexing. A current bottleneck for direct genome analyses by minisequencing, however, is the sensitivity, since minisequencing

Hugo Grønlund; Birgitte Moen; Jeffrey Hoorfar; Peter Radstrøm; Burkhard Malorny; Knut Rudi



A multi-bit multiplying digital-to-analog converter with bi-directional overflow detection  

Microsoft Academic Search

A design of a 3.5 + 1-bit multiplying digital-to-analog converter (MDAC) which can be used in the first stage of a 14-bit 100MS\\/s pipelined analog-to-digital converter (ADC) is presented in this paper. Two decision levels are added in the MDAC so that bi-directional overflow of the input signal can be detected. Bootstrap structure with a buffer is proposed to prevent

Rui Zhang; Yong-Sheng Yin; Shang-Quan Liang; Ming-Lun Gao



Improvement of Detection Limit in 14MeV Neutron Direct Interrogation Method by Decreasing Background  

Microsoft Academic Search

For the improvement of the detection limit in the 14MeV neutron direct interrogation method, the simulation calculation using the continuous-energy Monte Carlo transportation code (MVP) was carried out. From the results, it was clarified that the background neutrons appearing in the nuclear-fission neutron counting area can be greatly decreased by adopting a stainless steel SUS-304 (an iron-based alloy) reflector in




Do We Really Need OSTBCs for Free-Space Optical Communication with Direct Detection?  

Microsoft Academic Search

In this letter, the authors investigate spatial diversity techniques for free-space optical (FSO) links with intensity modulation and direct detection (IM\\/DD) over log-normal atmospheric turbulence-induced fading channels. We restrict our attention to the deployment of orthogonal space-time block codes (OSTBCs) and repetition codes both of which have been recently proposed for FSO links. Our performance analysis demonstrates that, although both

Majid Safari; Murat Uysal



Rapid and selective lead (II) colorimetric sensor based on azacrown ether-functionalized gold nanoparticles  

NASA Astrophysics Data System (ADS)

A gold nanoparticle (AuNPs)-based simple and fast colorimetric sensor for selective detecting of Pb(II) in aqueous solution has been developed. Monodisperse AuNPs (approx. 2.0 nm diameter) has been prepared facilely and further modified with an alkanethiol-bearing monoazacrown ether terminus. These AuNPs are shown to selectively sense Pb2 + through color change, which is visually discernible by an appearance of the surface plasmon band (SPB) at 520 nm. The recognition mechanism is attributed to the unique structure of the monoazacrown ether attached to AuNPs and metal sandwich coordination between two azacrown ether moieties that are attached to separate nanoparticles. This inter-particle cross-linking results in an aggregation and apparent color change from brown to purple. Additionally, TEM experiments support the optical absorption data proving the aggregation between azacrown ether-capped gold nanoparticles. This AuNP-based colorimetric assay is a facile and robust method and allows fast detection of Pb2 + at ambient temperatures. More importantly, the developed technique does not utilize enzymatic reactions, light-sensitive dye molecules, lengthy protocols or sophisticated instrumentation.

Alizadeh, A.; Khodaei, M. M.; Karami, Ch; Workentin, M. S.; Shamsipur, M.; Sadeghi, M.



Peptide-capped gold nanoparticle for colorimetric immunoassay of conjugated abscisic acid.  


The pentapeptide Cys-Ala-Leu-Asn-Asn (CALNN) has been proved to be a powerful tool to stabilize the AuNPs. These CALNN-capped AuNPs have been used to develop various bioanalysis platforms. In this paper, the CALNN-capped AuNPs are proved to be a robust tool for aggregation-based colorimetric immunoassays as well. A colorimetric immunoassay strategy based upon the antibody-induced assembly of functionalized AuNPs for Abscisic Acid glucose ester (ABA-GE) determination has been developed. The ABA-functionalized AuNPs aggregate in the presence of specific antibody, accompanied by a color change of the solution. The color change is competitively inhibited by ABA-GE. The interparticle distance in aggregates is small due to the thin peptide layer on the AuNPs surface, and it is determined by the "Y" shape antibody linker as well. As a result of that, an obvious color change in the immunoassays is observed. Under the optimized conditions, a linear response range from 5 nM to 10 ?M for ABA-GE determination is obtained, and the limit of detection (LOD) is evaluated to be 2.2 nM. This method is simple, homogeneous, and has potential for visual detection of ABA-GE. PMID:22906007

Zhou, Guohua; Liu, Yizhen; Luo, Ming; Xu, Qinfeng; Ji, Xinghu; He, Zhike



Fetal head detection and measurement in ultrasound images by a direct inverse randomized Hough transform  

NASA Astrophysics Data System (ADS)

Object detection in ultrasound fetal images is a challenging task for the relatively low resolution and low signal-to-noise ratio. A direct inverse randomized Hough transform (DIRHT) is developed for filtering and detecting incomplete curves in images with strong noise. The DIRHT combines the advantages of both the inverse and the randomized Hough transforms. In the reverse image, curves are highlighted while a large number of unrelated pixels are removed, demonstrating a "curve-pass filtering" effect. Curves are detected by iteratively applying the DIRHT to the filtered image. The DIRHT was applied to head detection and measurement of the biparietal diameter (BPD) and head circumference (HC). No user input or geometric properties of the head were required for the detection. The detection and measurement took 2 seconds for each image on a PC. The inter-run variations and the differences between the automatic measurements and sonographers" manual measurements were small compared with published inter-observer variations. The results demonstrated that the automatic measurements were consistent and accurate. This method provides a valuable tool for fetal examinations.

Lu, Wei; Tan, Jinglu; Floyd, Randall C.



Direct detection of bovine leukemia virus infection: practical applicability of a double polymerase chain reaction.  


A double polymerase chain reaction (PCR) assay has been devised for the direct detection of bovine leukemia virus (BLV). The assay was directly performed on blood leukocytes, avoiding the DNA-purification procedures. The PCR products were identified by gel-electrophoresis and the specificity of the test was confirmed by hybridization with a biotinylated oligonucleotide probe. When testing the sensitivity of PCR, less than eight genome copies of the provirus were detected in the background of two million negative lymphocytes. In a BLV infected herd 22 animals of various age groups were examined by the indirect (serological) diagnostic tests of agar-gel immunodiffusion and indirect ELISA as well as by the direct detection method of PCR. The tests were repeated at monthly intervals on five occasions. When examining the specimens from cows and heifers, a close agreement was found between the results of the various methods. The newborn calves, which were the offspring of BLV infected mothers, were consequently negative in PCR throughout the experimental period. However, in the indirect tests the calves were positive during the first samplings and became negative only around four months of age. Since the indirect tests can not discriminate infection from colostral immunity, PCR proved to be a useful complementary assay for the safe diagnosis of BLV infection in young calves. PMID:1316025

Ballagi-Pordány, A; Klintevall, K; Merza, M; Klingeborn, B; Belák, S



DNA: directional neighborhood analysis for detection of breast masses in screening mammograms  

NASA Astrophysics Data System (ADS)

We introduce a computer-assisted detection (CAD) system for the automated detection of breast masses in screening mammograms. The system targets the directional behavior of the neighborhood pixels surrounding a reference image pixel. The underlying hypothesis is that in the presence of a mass the directional properties of the breast tissue surrounding the mass should be altered. The hypothesis was tested using a database of 1,337 mammographic regions of interest (ROIs) extracted from DDSM mammograms. There were 681 ROIs containing a biopsy-proven mass centered in the ROI (340 malignant, 341 benign) and 656 ROIs depicting normal breast parenchyma. Initially, eight main directional propagations were identified and modeled given the center of the ROI as the reference pixel. Subsequently, eight novel morphological features were extracted for each direction. The features were designed to characterize the disturbance occurring in normal breast parenchyma due to the presence of a mass. Finally, the extracted features were merged using a back propagation neural network (BPANN). The network served as a non linear classifier trained to determine the presence of a mass centered at the reference image pixel. The BPANN was trained and tested using a leave-one-out sampling scheme. Its performance was evaluated with Receiver Operating Characteristics (ROC) analysis. Our CAD system showed an ROC area index of Az=0.88+/-0.01 for discriminating mass vs. normal ROIs. Detection performance was robust for both malignant (Az=0.88+/-0.01) and benign masses (Az=0.87+/-0.01). Thus, the proposed directional neighborhood analysis (DNA) can be applied effectively to identify suspicious masses in screening mammograms.

Eltonsy, Nevine H.; Tourassi, Georgia D.; Habas, Piotr A.; Elmaghraby, Adel S.



Ultrafast resonant polarization interferometry: Towards the first direct detection of vacuum polarization  

SciTech Connect

Vacuum polarization, an effect originally predicted nearly 70 years ago, is still yet to be directly detected despite significant experimental effort. Previous attempts have made use of large liquid-helium cooled electromagnets which inadvertently generate spurious signals that mask the desired signal. We present an approach for the ultrasensitive detection of optical birefringence that can be usefully applied to a laboratory detection of vacuum polarization. The technique has a predicted birefringence measurement sensitivity of {delta}n{approx}10{sup -20} in a 1 s measurement. When combined with the extreme polarizing fields achievable in this design we predict that a vacuum polarization signal will be seen in a measurement of just a few days in duration.

Luiten, Andre N.; Petersen, Jesse C. [School of Physics, University of Western Australia Nedlands, Western Australia 6907 (Australia)



A theoretical look at the direct detection of giant planets outside the Solar System.  


Astronomy is at times a science of unexpected discovery. When it is, and if we are lucky, new intellectual territories emerge to challenge our views of the cosmos. The recent indirect detections using high-precision Doppler spectroscopy of more than 100 giant planets orbiting more than 100 nearby stars is an example of such rare serendipity. What has been learned has shaken out preconceptions, for none of the planetary systems discovered so far is like our own. The key to unlocking a planet's chemical, structural, and evolutionary secrets, however, is the direct detection of the planet's light. Because there have been as yet no confirmed detections, a theoretical analysis of such a planet's atmosphere is necessary for guiding our search. PMID:15662414

Burrows, Adam



Chemical Methods for the Direct Detection and Labeling of S-Nitrosothiols  

PubMed Central

Abstract Significance: Posttranslational modification of proteins through phosphorylation, glycosylation, and oxidation adds complexity to the proteome by reversibly altering the structure and function of target proteins in a highly controlled fashion. Recent Advances: The study of reversible cysteine oxidation highlights a role for this oxidative modification in complex signal transduction pathways. Nitric oxide (NO), and its respective metabolites (including reactive nitrogen species), participates in a variety of these cellular redox processes, including the reversible oxidation of cysteine to S-nitrosothiols (RSNOs). RSNOs act as endogenous transporters of NO, but also possess beneficial effects independent of NO-related signaling, which suggests a complex and versatile biological role. In this review, we highlight the importance of RSNOs as a required posttranslational modification and summarize the current methods available for detecting S-nitrosation. Critical Issues: Given the limitations of these indirect detection methods, the review covers recent developments toward the direct detection of RSNOs by phosphine-based chemical probes. The intrinsic properties that dictate this phosphine/RSNO reactivity are summarized. In general, RSNOs (both small molecule and protein) react with phosphines to yield reactive S-substituted aza-ylides that undergo further reactions leading to stable RSNO-based adducts. Future Directions: This newly explored chemical reactivity forms the basis of a number of exciting potential chemical methods for protein RSNO detection in biological systems. Antioxid. Redox Signal. 17, 981–991.

Bechtold, Erika



Development of a routine laboratory direct detection system of staphylococcal enterotoxin genes.  


A novel direct detection system has been developed for eight staphylococcal enterotoxin (SE)-encoding genes (sea, seb, sec, sed, see, seg, seh and sei) in milk. Specific detection by real-time PCR was successful for all SE-encoding genes in the reference strains. Furthermore, a novel DNA-preparation method with good reproducibility [coefficients of variation 0.31, 0.99 and 1.21 % at 10(6), 10(4) and 10(2) c.f.u. (ml milk sample)(-1), respectively] was developed to overcome PCR inhibition in the milk samples. The combination of this DNA-preparation method and real-time PCR resulted in high sensitivity [between 1.1 x 10(2) and 1.0 x 10(4) c.f.u. (ml milk sample)(-1)] and allowed the completion of the entire procedure within 4 h. Results of an evaluation of this method for the detection of SE-encoding genes using known outbreak milk samples produced results showing good correspondence with the reversed passive latex agglutination assay. In addition, this newly developed system can be applied to clinical samples such as faeces and vomit. Consequently, the system should be useful in the routine direct detection of SE-encoding genes in food-borne-poisoning samples. PMID:16476790

Nakayama, Akifumi; Okayama, Akiko; Hashida, Misao; Yamamoto, Yasuzumi; Takebe, Hisakatsu; Ohnaka, Takashi; Tanaka, Tomoyuki; Imai, Shunsuke



Direction sensitive fall detection using a triaxial accelerometer and a barometric pressure sensor.  


Falling is one of the leading causes of serious health decline or injury-related deaths in the elderly. For survivors of a fall, the resulting health expenses can be a devastating burden, largely because of the long recovery time and potential comorbidities that ensue. The detection of a fall is, therefore, important in care of the elderly for decreasing the reaction time by the care-givers especially for those in care who are particularly frail or living alone. Recent advances in motion-sensor technology have enabled wearable sensors to be used efficiently for pervasive care of the elderly. In addition to fall detection, it is also important to determine the direction of a fall, which could help in the location of joint weakness or post-fall fracture. This work uses a waist-worn sensor, encompassing a 3D accelerometer and a barometric pressure sensor, for reliable fall detection and the determination of the direction of a fall. Also assessed is an efficient analysis framework suitable for on-node implementation using a low-power micro-controller that involves both feature extraction and fall detection. A detailed laboratory analysis is presented validating the practical application of the system. PMID:22254325

Tolkiehn, Marie; Atallah, Louis; Lo, Benny; Yang, Guang-Zhong



Colorimetric assay for urinary track infection disease diagnostic on flexible substrate  

NASA Astrophysics Data System (ADS)

We are presenting cassette as a novel point of care diagnostic device. This device is easy to use, low cost to prepare, high throughput and can analyze several samples at the same time. We first, demonstrate the preparation method of the device. Then, fabrication of the flexible substrate has been presented. The device has been used for detection of the real sample of E.coli bacteria following by colorimetric detection. We have shown that we could detect 30 cfu/ml bacteria and 100 fg/?l of Staphylococous aureus DNA in 1 hr using LAMP amplification technique. This device will be helpful in hospitals and doctor's office for analysis of several patients' samples at the same time.

Safavieh, Mohammadali; Ahmed, Minhaz Uddin; Zourob, Mohammed



Three colorimetric and off-on fluorescent chemosensors for Fe3+ in aqueous media.  


Three Rhodamine B derivatives were synthesized and characterized by ESI-MS, NMR, HR-MS and IR. The probes exhibit high selectivity and sensitivity towards Fe(3+) over other metal ions in CH3CN-water. Upon the addition of Fe(3+), the spirocyclic ring of the probe was opened and a significant enhancement of visible color and fluorescence within the range of 540-700 nm was observed. The colorimetric and fluorescent response to Fe(3+) can be conveniently detected even by the naked eye, which provides a facile method for the visual detection of Fe(3+). Job's plot, fluorescence titration and MS indicated the formation of 1:2 complexes between the probes and Fe(3+). The reversibility of the reaction establishes the potential of these probes as chemosensors for Fe(3+) detection. PMID:23460525

Chai, Meimei; Li, Man; Zhang, Di; Wang, Cui-cui; Ye, Yong; Zhao, Yufen



Gold-nanoparticle-based colorimetric discrimination of cancer-related point mutations with picomolar sensitivity.  


Point mutations in the Kirsten rat sarcoma viral oncogene homologue (KRAS) gene are being increasingly recognized as important diagnostic and prognostic markers in cancer. In this work, we describe a rapid and low-cost method for the naked-eye detection of cancer-related point mutations in KRAS based on gold nanoparticles. This simple colorimetric assay is sensitive (limit of detection in the low picomolar range), instrument-free, and employs nonstringent room temperature conditions due to a combination of DNA-conjugated gold nanoparticles, a probe design which exploits cooperative hybridization for increased binding affinity, and signal enhancement on the surface of magnetic beads. Additionally, the scheme is suitable for point-of-care applications, as it combines naked-eye detection, small sample volumes, and isothermal (PCR-free) amplification. PMID:23697628

Valentini, Paola; Fiammengo, Roberto; Sabella, Stefania; Gariboldi, Manuela; Maiorano, Gabriele; Cingolani, Roberto; Pompa, Pier Paolo



A Modified Colorimetric Method for Phytic Acid Analysis in Soybean  

Microsoft Academic Search

A quantitative, reproducible, and effi cient phytic acid assay procedure is needed to screen breed- ing populations and support genetic studies in soybeans (Glycine max (L.) Merr.). The objective of this study was to modify the colorimetric Wade reagent method and compare the accuracy and applicability of this new method in determining seed phytic acid content in soybean with three

Y. Gao; C. Shang; M. A. Saghai Maroof; R. M. Biyashev; E. A. Grabau; P. Kwanyuen; J. W. Burton; G. R. Buss



A Colorimetric Method for the Determination of Sugars  

Microsoft Academic Search

VOLUMETRIC procedures have been used for the quantitative determination of sugars after separation by partition chromatography1,2. It has been our experience that these methods not only require considerable skill, but also they are lengthy and sensitive to slight variation of the conditions. We have therefore attempted to develop a simple quantitative colorimetric procedure. Preliminary experiments showed that the anthrone3 and

M. Dubois; K. Gilles; J. K. Hamilton; P. A. Rebers; F. Smith



Changes in perception of colorimetric differences caused by different backgrounds  

Microsoft Academic Search

The aim of this research was to improve student's knowledge of colors and different parameters that influence its perception. Through research they were introduced to the different characteristics of the display that result in different gamut. The aim was to investigate the effect of background on perception of colorimetric differences.

Lidija Mandic; Maja Strgar Kurecic; Ante Poljicak; Darko Agic



A modified colorimetric method for phytic acid analysis in soybean  

Technology Transfer Automated Retrieval System (TEKTRAN)

A quantitative, reproducible, and efficient phytic acid assay procedure is needed to screen breeding populations and support genetic studies in soybeans. The objective of this study was to modify the colorimetric Wade reagent method and compare the accuracy and applicability of this new method in de...


Gold nanoparticle-based colorimetric assay for cancer diagnosis  

Microsoft Academic Search

A novel gold nanoparticle (GNP)-based colorimetric assay was developed for cancer diagnosis. This system is based on the noncrosslinking aggregation mechanism with a cationic protein kinase C (PKC) ?-specific peptide substrate, which is used as a coagulant of citrate-coated GNP with anionic surface charges. The phosphorylation of peptide substrates by PKC? suppressed GNP aggregation, resulting in a red color, but

Jeong-Hun Kang; Yoji Asami; Masaharu Murata; Hirotaro Kitazaki; Noriaki Sadanaga; Eriko Tokunaga; Satoko Shiotani; Satoko Okada; Yoshihiko Maehara; Takuro Niidome; Makoto Hashizume; Takeshi Mori; Yoshiki Katayama



A Colorimetric Process to Visualize Erythrocyte Exovesicles Aggregates  

ERIC Educational Resources Information Center

A biochemistry laboratory class protocol is described in order to create an opportunity for students to apply by doing the theoretical concepts underlying biomolecules and vesicles properties, together with the principles of centrifugation and colorimetric methodologies. Through simple procedures the students will i) observe the segregation of the…

Saldanha, Carlota; Santos, Nuno C.; Martins-Silva, J.



A Colorimetric Process to Visualize Erythrocyte Exovesicles Aggregates  

ERIC Educational Resources Information Center

|A biochemistry laboratory class protocol is described in order to create an opportunity for students to apply by doing the theoretical conc