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1

Fluorescent dye-based simple staining for in vivo micronucleus test with flow cytometer.  

PubMed

Flow cytometry (FCM) has become known as a useful tool for examining numerous cells in a micronucleus test in a short time. To successfully count micronuclei, immature erythrocytes and micronuclei need to be specifically stained and CD71-based FCM, with anti-CD71 antibody for immature erythrocytes and propidium iodide (PI) for micronuclei is a widely accepted tool. Because staining with fluorescent dyes may be much simpler compared to immunostaining, attempts are being made to develop a fluorescent dye-based FCM (FD-FCM). The aim of this study was to provide a practical FD-FCM method. Peripheral blood (PB) erythrocytes and bone marrow (BM) erythrocytes were obtained from rats treated with cyclophosphamide at a dose of 20mg/kg for two days. Nucleic cells of BM samples were eliminated using a cellulose column. Then erythrocytes were fixed, stained with Hoechst 33258 and PI and examined with FCM. Mean FD-FCM values of micronucleated immature erythrocytes in PB and BM were respectively 110% and 77% of the values obtained by microscopy. Percentages of mean immature erythrocyte values by FCM to those by microscopy were 74% and 94%. These data suggest that the simple method, composed of column purification of erythrocytes, methanol fixation, fluorescent dye staining and FCM, was useful for automated scoring in micronucleus testing of rat BM and PB. PMID:23291344

Harada, Asako; Matsuzaki, Kaori; Takeiri, Akira; Tanaka, Kenji; Mishima, Masayuki

2013-03-18

2

A simple and effective coumarin-based fluorescent probe for cysteine.  

PubMed

Acrylic acid 3-acetyl-2-oxo-2 H-chromen-7-yl ester (ACA) was rationally designed and synthesized as a simple and effective fluorescent probe for sensing cysteine with high selectivity and naked-eye detection. The probe can detect cysteine by fluorescence spectrometry with a detection limit of 0.657?M and can be used with calf serum and in live cell imaging. The conjugate addition/cyclization sequence mechanism of the reaction between ACA and cysteine was con?rmed by ESI-MS and fluorescence spectra. PMID:24690559

Dai, Xi; Wu, Qing-Hua; Wang, Peng-Chong; Tian, Jie; Xu, Yu; Wang, Sheng-Qing; Miao, Jun-Ying; Zhao, Bao-Xiang

2014-09-15

3

A Simple Levulinate-based Ratiometric Fluorescent Probe for Sulfite with a Large Emission Shift.  

PubMed

A simple 4-hydroxynaphthalimide-derived colorimetric and ratiometric fluorescent probe (1) containing a receptor of levulinate moiety was designed and synthesized to monitor sulfite. Probe 1 could quantificationally detect sulfite by a ratiometric fluorescence spectroscopy method with high selectivity and sensitivity. Specially, probe 1 exhibited a 100 nm red-shifted absorption spectrum along with the color changes from colorless to yellow, and 103 nm red-shifted emission spectra upon the addition of sulfite. Thus, 1 can serve as a "naked-eye" probe for sulfite. Further, the recognition mechanism of probe 1 for sulfite was confirmed using nuclear magnetic resonance and electrospray ionization mass spectrometry. Also, the preliminary practical application demonstrated that our proposed probe provided a promising method for the determination of sulfite. PMID:24813958

Liu, Caiyun; Wu, Huifang; Yang, Wen; Zhang, Xiaoling

2014-01-01

4

A simple and reusable fluorescent sensor for heme proteins based on a conjugated polymer-doped electrospun nanofibrous membrane.  

PubMed

We reported a simple and reusable fluorescent sensor for heme proteins based on the electrospun nanofibrous membrane doped with a fluorescent conjugated polymer P. The sensor showed favorable fluorescence sensing performance towards the heme proteins, including hemoglobin (Hb), myoglobin (Mb) and cytochrome c (Cyt c). The surface wettability and sensing performance of the electrospun nanofibrous membrane were investigated in detail using Hb as the model. The nanofibrous sensor showed satisfactory reversibility with less than 10% signal loss after nine quenching-regeneration cycles, and good batch-to-batch reproducibility with a relative standard deviation of 3.4% (n=3). The linear range of the sensor for Hb determination was 2.0×10(-8) to 3.0×10(-6) M with a detection limit of 1.2×10(-8) M. The quenching process is mainly based on the fluorescence resonance energy transfer mechanism between the fluorescent conjugated polymer P and the heme prosthetic groups, therefore the sensor was selective against most of the common interferents. As an example to evaluate the feasibility of the sensor in practical application, Hb in human blood samples was determined and the results were in good agreement with the data provided by the hospital. To the best of our knowledge, this is the first work using fluorescent electrospun nanofibrous sensor for protein analysis in real biological sample. PMID:22608438

Wang, Huaming; Peng, Zhou; Long, Yuanyuan; Chen, Haibo; Yang, Yufei; Li, Na; Liu, Feng

2012-05-30

5

Simple Adhesive-Tape-Based Sampling of Tomato Surfaces Combined with Rapid Fluorescence In Situ Hybridization for Salmonella Detection?  

PubMed Central

A simple adhesive-tape-based method for sampling of tomato surfaces was combined with fluorescence in situ hybridization for rapid culture-independent detection of Salmonella strains. Tapes could also be placed face-down on selective agar for on-tape enrichment of captured Salmonella cells. Overlay of cell-charged tapes with small volumes of liquid enrichment media enabled subsequent detection of tape-captured Salmonella via flow cytometry.

Bisha, Bledar; Brehm-Stecher, Byron F.

2009-01-01

6

A simple and sensitive surface molecularly imprinted polymers based fluorescence sensor for detection of ?-Cyhalothrin.  

PubMed

In this study, surface molecularly imprinted YVO4:Eu(3+) nanoparticles with molecular recognitive optosensing activity were successfully prepared by precipitation polymerization using ?-Cyhalothrin (LC) as template molecules, methacrylic acid and ethylene glycol dimethacrylate as the polymerization precursors which could complex with template molecules, and the material has been characterized by SEM, TEM, FT-IR, XRD, TGA and so on. Meanwhile, the as-prepared core-shell structured nanocomposite (YVO4:Eu(3+)@MIPs), which was composed of lanthanide doped YVO4:Eu(3+) as fluorescent signal and surface molecular imprinted polymers as molecular selective recognition sites, could selectively and sensitively optosense the template molecules. After the experimental conditions were optimized, two linear relationship were obtained covering the concentration range of 2.0-10.0 ?M and 10.0-90.0 ?M, and the limit of detection (LOD) for LC was found to be 1.76 ?M. Furthermore, a possible mechanism was put forward to explain the fluorescence quenching of YVO4:Eu(3+)@MIPs. More importantly, the obtained sensor was proven to be suitable for the detection of residues of LC in real examples. And the excellent performance of this sensor will facilitate future development of rapid and high-efficiency detection of LC. PMID:24840409

Liu, Chunbo; Song, Zhilong; Pan, Jianming; Yan, Yongsheng; Cao, Zhijing; Wei, Xiao; Gao, Lin; Wang, Juan; Dai, Jiangdong; Meng, Minjia; Yu, Ping

2014-07-01

7

Simple boric acid-based fluorescent focusing for sensing of glucose and glycoprotein via multipath moving supramolecular boundary electrophoresis chip.  

PubMed

Boric acid-based fluorescent complex probe of BBV-HPTS (boronic acid-based benzyl viologen (BBV) and hydroxypyrene trisulfonic acid trisodium salt (HPTS)) was rarely used for sensitive sensing of saccharide (especially glycoprotein) via electrophoresis. We proposed a novel model of moving supramolecular boundary (MSB) formed with monosaccharide or glycoprotein in microcolumn and the complex probe of BBV-HPTS in the cathodic injection tube, developed a method of MSB fluorescent focusing for sensitive recognition of monosaccharide and glycoprotein, and designed a special multipath capillary electrophoresis (CE) chip for relative experiments. As a proof of concept, glucose and hemoglobin A1c (HbA1c) were respectively used as the mode saccharide and glycoprotein for the relevant demonstration. The experiments revealed that (i) the complex of BBV-HPTS could interact with free glucose or bound one in glycoprotein; (ii) the fluorescent signal was a function of glucose or glycoprotein content approximately; and (iii) interestingly the fluorescent band motion was dependent on glucose content. The developed method had the following merits: (i) low cost; (ii) low limit of detection (down to 1.39 pg/mL for glucose and 2.0 pg per capillary HbA1c); and (iii) high throughput (up to 12 runs or more per patch) and speed (less than 5 min). The developed method has potential use for sensitive monitoring of monosaccharide and glycoprotein in biomedical samples. PMID:23687936

Dong, Jingyu; Li, Si; Wang, Houyu; Meng, Qinghua; Fan, Liuyin; Xie, Haiyang; Cao, Chengxi; Zhang, Weibing

2013-06-18

8

Simple and sensitive synchronous- fluorescence method for the determination of trace bisphenol S based on its inhibitory effect on the fluorescence quenching reaction of rhodamine B.  

PubMed

An inhibitory kinetic fluorimetric method is reported for the determination of trace bisphenol S (BPS). The proposed method is based on the inhibitory effect of BPS on the fluorescence quenching of rhodamine B (RhB) caused by potassium bromate in a dilute phosphoric acid medium. Under the optimal conditions of the experiment, the detection limit for BPS was 0.021 mg/L, and the linear range of determination was from 0.035 mg/L to 0.750 mg/L. The relative standard deviations of 11 measurements for 0.20 mg/L and 0.40 mg/L BPS solutions were 2.74 % and 1.87 %, respectively. The method was successfully applied to the determination of bisphenol S derived from commercially available plastic film samples in hot water. A possible reaction mechanism of the inhibitory effect of BPS on the fluorescence quenching of RhB was proposed. PMID:23471627

Cao, Gui-ping; Chen, Ting; Zhuang, Ya-feng

2013-07-01

9

A simple BODIPY-aniline-based fluorescent chemosensor as multiple logic operations for the detection of pH and CO2 gas.  

PubMed

A simple 4-aniline boron-dipyrromethene (BODIPY) dye () was developed as a highly sensitive acidic pH fluorescent probe excitable with visible light based on a photoinduced electron transfer (PeT) mechanism. The pH titration indicates that the fluorescence intensity increases more than 500-fold within the pH range of 4.12-1.42 with a pKa value of 3.24 in methanol-water (1?:?1, v/v) solution, which is valuable for studying strongly acidic conditions. Density functional theory (DFT) calculations reproduce the fluorescence off-on behavior. has also been used as a fluorescent chemosensor for the visual detection of dissolved carbon dioxide (CO2) gas. The underlying mechanism of the sensing process is rationalized. This probe can be recovered by bubbling nitrogen (N2) gas into CO2-treated solutions for over 10 cycles. In addition, two logic gates (OR and INH) have been achieved at the molecular level by changing the initial states of system and chemical inputs. PMID:24756338

Pan, Zhong-Hua; Luo, Geng-Geng; Zhou, Jing-Wei; Xia, Jiu-Xu; Fang, Kai; Wu, Rui-Bo

2014-05-13

10

An eco-friendly, simple, and sensitive fluorescence biosensor for the detection of choline and acetylcholine based on C-dots and the Fenton reaction.  

PubMed

A simple and novel method is proposed for the preparation of Carbon dots (C-dots) with excellent properties. We firstly demonstrated that the fluorescence of C-dots decreased apparently in the presence of H2O2 and Fe(2+). Based on the this finding, C-dots are successfully adopted as probes for the detection of H2O2. After the experimental conditions are optimized, the limit of detection (LOD) for H2O2 is found to be 0.1 ?M. Furthermore, we established an eco-friendly, simple and sensitive biosensor for the detection of choline and acetylcholine (ACh) based on the detection of H2O2 using C-dots as probes. The detection limit for choline is 0.1 ?M and the linear range is 0.1-40 ?M. The detection limit for ACh is found to be 0.5 ?M and the linear range is 0.5-60 ?M. The excellent performance of the proposed biosensor shows that this method possesses the potential for practical application. PMID:24080209

Wei, Jianfei; Ren, Jun; Liu, Jing; Meng, Xianwei; Ren, Xiangling; Chen, Zhenzhen; Tang, Fangqiong

2014-02-15

11

Simple optical modeling of polarized fluorescent liquid crystal cells  

NASA Astrophysics Data System (ADS)

We investigate the fluorescence emission properties of dye-doped nematic liquid crystal (LC) cells with planar and zigzag emissive layers. To explain the measured angular dependence of the emitted light (emission pattern), we introduce a simple optical model, in which both planar and zigzag emissive layers are approximated as a homogeneously oriented flat LC layer with an equivalent anisotropy. It was revealed that all the measured emission patterns under different LC molecular orientation conditions agree well with the optical model, whereas the conventional Lambertian-based distribution function does not coincide with the measured profile in homeotropically aligned LC cells.

Honma, Michinori; Yamamoto, Shigeki; Nose, Toshiaki

2013-07-01

12

A simple fiber optic level sensor using fluorescent fibers  

Microsoft Academic Search

A simple ‘‘proof-of-principle’’ demonstration of the use of fluorescent optical fibers in an optical level sensor has been shown and results obtained over a sensing range of several hundred millimeters to an acceptable degree of accuracy for a low-cost, simple domestic or industrial device.

A. T. Augousti; J. Mason; K. T. V. Grattan

1990-01-01

13

Simple and specific detection of abnormal prion protein by a magnetic bead-based immunoassay coupled with laser-induced fluorescence spectrofluorometry.  

PubMed

Transmissible spongiform encephalopathies (TSEs), also termed prion diseases, are fatal neurodegenerative conditions that affect both humans and animals. The transmissibility and fatal nature of TSEs necessitate their rapid and accurate diagnosis. Laser-induced fluorescence (LIF) spectrofluorometry is useful for obtaining measurements on fluorescence-labeled targets with a high degree of sensitivity. In the present study, we applied this technology to the immunological detection of abnormal prion protein, PrPSc, which is a universal diagnostic marker for TSEs. The assay format consists of a magnetic bead-based sandwich immunoassay utilizing a biotin-conjugated capture antibody and a fluorophore-labeled detector antibody. By using one pair of anti-PrP monoclonal antibodies (MAbs), PrPSc in brain homogenates from various experimental and natural TSEs can be easily detected with high specificity. Furthermore, the assay proved to be applicable for the detection of PrPSc in the lymph nodes from deer with TSE. The sensitivity of the assay was shown to be comparable to standard immunoblotting, but has several advantages over conventional tests, in terms of flexibility, simplicity, specificity, and run time. These results provide an important basis for the development of an early diagnostic test with potential for multi-sample analysis. PMID:15589044

Kim, Jae-Il; Wang, Chuanhua; Kuizon, Salomon; Xu, Jiliu; Barengolts, Denis; Gray, Perry C; Rubenstein, Richard

2005-01-01

14

Simple model for plasmon enhanced fluorescence correlation spectroscopy.  

PubMed

Metallic nano-antennas provide strong field confinement and intensity enhancement in hotspots and thus can ultimately enhance fluorescence detection and provide ultra small detection volumes. In solution-based fluorescence measurements, the diffraction limited focus driving the nano-antenna can outshine the fluorescence originating from the hotspot and thus render the benefits of the hotspot negligible. We introduce a model to calculate the effect of a nano-antenna, or any other object creating a nontrivial intensity distribution, for fluorescence fluctuation measurements. Approximating the local field enhancement of the nano-antenna by a 3D Gaussian profile, we show which hotspot sizes and intensities are the most beneficial for an FCS measurement and compare it to realistic antenna parameters from literature. PMID:24977800

Langguth, Lutz; Femius Koenderink, A

2014-06-30

15

Simple and specific detection of abnormal prion protein by a magnetic bead-based immunoassay coupled with laser-induced fluorescence spectrofluorometry  

Microsoft Academic Search

Transmissible spongiform encephalopathies (TSEs), also termed prion diseases, are fatal neurodegenerative conditions that affect both humans and animals. The transmissibility and fatal nature of TSEs necessitate their rapid and accurate diagnosis. Laser-induced fluorescence (LIF) spectrofluorometry is useful for obtaining measurements on fluorescence-labeled targets with a high degree of sensitivity. In the present study, we applied this technology to the immunological

Jae-Il Kim; Chuanhua Wang; Salomon Kuizon; Jiliu Xu; Denis Barengolts; Perry C. Gray; Richard Rubenstein

2005-01-01

16

A novel functional imidazole fluorescent ionic liquid: simple and efficient fluorescent probes for superoxide anion radicals.  

PubMed

Novel imidazole fluorescent ionic liquids with anthracene groups (ImS-FILA) were synthesized for the first time to act as fluorescent probes. They were developed for the determination of superoxide anion radicals (O2 (•-)) in an aqueous system. O2 (•-) was produced by pyrogallol autoxidation. The fluorescence of ImS-FILA was quenched by superoxide anion radicals. The ?-bond structure of the fluorescent molecules was oxidized and damaged. This method is very simple and sensitive. The linear range of sensitivity was 1-70 ?M ImS-FILA, and the detection limit for reactive oxygen species was 0.1 ?M. This method was used to detect superoxide radicals in papaya and garlic, with satisfactory results. Further work is needed to demonstrate the utility of this method in detecting reactive oxygen species in a biological aqueous system. PMID:24126836

Liu, Haiqing; Zhang, Lina; Chen, Jiangmin; Zhai, Yunyun; Zeng, Yanbo; Li, Lei

2013-11-01

17

Fluorescence-based glucose sensors  

Microsoft Academic Search

There is an urgent need to develop technology for continuous in vivo glucose monitoring in subjects with diabetes mellitus. Problems with existing devices based on electrochemistry have encouraged alternative approaches to glucose sensing in recent years, and those based on fluorescence intensity and lifetime have special advantages, including sensitivity and the potential for non-invasive measurement when near-infrared light is used.

John C. Pickup; Faeiza Hussain; Nicholas D. Evans; Olaf J. Rolinski; David J. S. Birch

2005-01-01

18

Fluorescent polymeric transducer for the rapid, simple, and specific detection of nucleic acids at the zeptomole level.  

PubMed

We report the specific detection of a few hundred molecules of genetic material using a fluorescent polythiophene biosensor. Such recognition is based on simple electrostatic interactions between a cationic polymeric optical transducer and the negatively charged nucleic acid target and can be done in less than 1 h, simply and affordably, and without any chemical reaction. This simple system is versatile enough to detect nucleic acids of various lengths, including a segment from the RNA genome of the Influenza virus. PMID:15053613

Doré, Kim; Dubus, Sébastien; Ho, Hoang-Anh; Lévesque, Isabelle; Brunette, Maryse; Corbeil, Geneviève; Boissinot, Maurice; Boivin, Guy; Bergeron, Michel G; Boudreau, Denis; Leclerc, Mario

2004-04-01

19

Fluorescent photoswitchable nanohybrids based on photochromism  

Microsoft Academic Search

A new type of fluorescent photoswitchable nanohybrids based on photochromism has been assembled, in which hydrophobic diarylethene and matched fluorescent dye are assembled in the nanoscale crosslinked polymeric matrix via a modified miniemulsion polymerization process and a seeded polymerization technique. The nanohybrids exhibited excellent fluorescent photoswitchable action owing to efficient photoinduced energy transfer whether the nanohybrids as nanoparticles dispersed in

Zhenkun Hu; Qing Zhang; Minzhao Xue; Qiaorong Sheng; Yan-gang Liu

2008-01-01

20

Microparticle-based fluorescence immunoassay.  

National Technical Information Service (NTIS)

We have recently shown that it is possible to detect single molecules of highly fluorescent dyes (1). However, there are a large number of compounds of practical interest that are either nonfluorescent or, if fluorescent, the emission spectrum is not suff...

W. B. Whitten J. M. Ramsey B. V. Bronk

1992-01-01

21

Ultra Simple Fluorescent White Organic Light-Emitting Diodes Using Fluorescent Green-Yellow Emitter and Blue Host  

Microsoft Academic Search

The authors have demonstrated ultra simple fluorescent white organic light-emitting diodes using fluorescent green-yellow emitter of 9,10-bis[4-(di-4-tert-butylphenylamino) styryl]anthracene and blue host of 2-methyl-9,10-di(2-naphthyl)anthracene. The optimized device at the extremely low doping concentration (0.2 wt.%) of green-yellow emitter showed a luminous efficiency of 7.18 cd\\/A, a power efficiency of 5.64 lm\\/W at 100 cd\\/m, and a Commission Internationale de I'Eclairage coordinates of (0.35, 0.43) at

Ji Hoon Seo; Jung Sun Park; Jun Ho Kim; Kum Hee Lee; Jung Yeon Kim; Seung Soo Yoon; Young Kwan Kim

2010-01-01

22

a Simple Method for Preparation of Fluorescent Nanostructure Silica with Hexagonal Array  

NASA Astrophysics Data System (ADS)

A nanostructure modified silica with good fluorescence properties was prepared by grafting Al3+ ions on the surface of nanoporous silica and then binding of 8-hydroxyquinoline (8-HQ) to the grafted Al3+ ions. The prepared material, denoted as NS-AlQ2, was characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), nitrogen adsorption-desorption measurements, FT-IR and fluorescence spectra. This compound shows emission spectra approximately in the emission range of AlQ3 complex. This procedure provides a simple method for grafting fluorescent molecules in the channels of nanoporous silica materials.

Badiei, Alireza; Goldooz, Hassan

23

A simple and sensitive approach for ochratoxin a detection using a label-free fluorescent aptasensor.  

PubMed

Ochratoxin A(OTA) is found to be one of the predominant contaminating mycotoxins in a wide variety of food commodities. To avoid the risk of OTA consumption, the detection and quantitation of OTA level are of great significance. Based on the fact that ssDNA aptamer has the ability to form a double-strand structure with its complementary sequence, a simple and rapid aptamer-based label-free approach for highly sensitive and selective fluorescence detection of OTA was developed by using ultra-sensitive double-strand DNA specific dyes PicoGreen. The results showed that as low as 1 ng/mL of OTA could be detected with a dynamic range of more than 5 orders of magnitude which satisfies the requirements for OTA maximum residue limit in various food regulated by European Commission. With the specificity of aptamer, the assay exhibited high selectivity for OTA against two other analogues (N-acetyl-l-phenylalanine and zearalenone). We also tested the aptasensor practicability using real sample of 1% beer spiked with a series of concentration of OTA and the results show good tolerance to matrix effect. All detections could be achieved in less than 30 min, which provides a simple, quick and sensitive detection method for OTA screening in food safety and could be easily extend to other small molecular chemical compounds detection which aptamer has been selected. PMID:24465818

Lv, Zhenzhen; Chen, Ailiang; Liu, Jinchuan; Guan, Zheng; Zhou, Yu; Xu, Siyuan; Yang, Shuming; Li, Cheng

2014-01-01

24

A Simple and Sensitive Approach for Ochratoxin A Detection Using a Label-Free Fluorescent Aptasensor  

PubMed Central

Ochratoxin A(OTA) is found to be one of the predominant contaminating mycotoxins in a wide variety of food commodities. To avoid the risk of OTA consumption, the detection and quantitation of OTA level are of great significance. Based on the fact that ssDNA aptamer has the ability to form a double-strand structure with its complementary sequence, a simple and rapid aptamer-based label-free approach for highly sensitive and selective fluorescence detection of OTA was developed by using ultra-sensitive double-strand DNA specific dyes PicoGreen. The results showed that as low as 1 ng/mL of OTA could be detected with a dynamic range of more than 5 orders of magnitude which satisfies the requirements for OTA maximum residue limit in various food regulated by European Commission. With the specificity of aptamer, the assay exhibited high selectivity for OTA against two other analogues (N-acetyl-l-phenylalanine and zearalenone). We also tested the aptasensor practicability using real sample of 1% beer spiked with a series of concentration of OTA and the results show good tolerance to matrix effect. All detections could be achieved in less than 30 min, which provides a simple, quick and sensitive detection method for OTA screening in food safety and could be easily extend to other small molecular chemical compounds detection which aptamer has been selected.

Lv, Zhenzhen; Chen, Ailiang; Liu, Jinchuan; Guan, Zheng; Zhou, Yu; Xu, Siyuan; Yang, Shuming; Li, Cheng

2014-01-01

25

Carbon Nanoparticle-based Fluorescent Bioimaging Probes  

PubMed Central

Fluorescent nanoparticle-based imaging probes have advanced current labelling technology and are expected to generate new medical diagnostic tools based on their superior brightness and photostability compared with conventional molecular probes. Although significant progress has been made in fluorescent semiconductor nanocrystal-based biological labelling and imaging, the presence of heavy metals and the toxicity issues associated with heavy metals have severely limited the application potential of these nanocrystals. Here, we report a fluorescent carbon nanoparticle-based, alternative, nontoxic imaging probe that is suitable for biological staining and diagnostics. We have developed a chemical method to synthesise highly fluorescent carbon nanoparticles 1–10?nm in size; these particles exhibit size-dependent, tunable visible emission. These carbon nanoparticles have been transformed into various functionalised nanoprobes with hydrodynamic diameters of 5–15?nm and have been used as cell imaging probes.

Bhunia, Susanta Kumar; Saha, Arindam; Maity, Amit Ranjan; Ray, Sekhar C.; Jana, Nikhil R.

2013-01-01

26

Fluorescence spectra shape based dynamic thermometry  

NASA Astrophysics Data System (ADS)

An entirely optical, dynamic thermometry technique based on the temperature dependence of a fluorescence spectrum is presented. Different from conventional intensity-based fluorescence thermometry, in this work, neural network recognition is employed to extract the sample temperature from the magnitude and shape of recorded fluorescence spectra. As a demonstration to determine the depth profile of dynamical temperature variations and of the thermal and optical properties of semitransparent samples, in-depth photothermally induced periodical temperature oscillations of a rhodamine B and copper chloride dyed glycerol sample were measured with an accuracy of 4.2 mK·Hz-1/2 and fitted well by a 1D thermal diffusion model.

Liu, Liwang; Creten, Sebastiaan; Firdaus, Yuliar; Agustin Flores Cuautle, Jose Jesus; Kouyaté, Mansour; Van der Auweraer, Mark; Glorieux, Christ

2014-01-01

27

Detection of arsenical drug resistance in Trypanosoma brucei with a simple fluorescence test.  

PubMed

The resurgence of human African trypanosomiasis (HAT), coupled with an increased incidence of drug resistance, is of concern. We report a quick, simple, and sensitive test for identification of parasites resistant to melarsoprol, the main drug used to treat late stage HAT. Resistant parasites are defective in a plasma membrane transporter responsible for drug uptake. The same transporter carries the fluorescent diamidine DB99 (2,5-bis-(4-amidinophenyl)-3,4-dimethylfuran) into trypanosomes. The two DNA-containing structures in the trypanosome--the nucleus and the kinetoplast--begin to fluoresce within 1 min of introduction of DB99, unless drug resistant. PMID:16084257

Stewart, Mhairi L; Krishna, Sanjeev; Burchmore, Richard J S; Brun, Reto; de Koning, Harry P; Boykin, David W; Tidwell, Richard R; Hall, J Ed; Barrett, Michael P

28

A simple and general route for monofunctionalization of fluorescent and magnetic nanoparticles using peptides  

NASA Astrophysics Data System (ADS)

Nanoparticles are now utilized in many diverse biological and medical applications. Despite this, it remains challenging to tailor their surface for specific molecular targeting while maintaining high biocompatibility. To address this problem, we evaluate a phytochelatin-related peptide surface coating to produce functional and biocompatible nanoparticles (NPs) based on fluorescent InP/ZnS and CdSe/ZnS or superparamagnetic FePt and Fe3O4. Using a combination of transmission electron microscopy, size-exclusion chromatography and gel electrophoresis (GE), we demonstrate the excellent colloidal properties of the peptide-coated NPs (pNPs) and the compact nature of the coating (~4 nm thickness). We develop a simple protocol for the monofunctionalization of the pNPs with targeting biomolecules, by combining covalent conjugation with GE purification. We then employ functionalized InP/ZnS pNPs in a live-cell, single-molecule imaging application to specifically target and detect individual proteins in the cell membrane. These findings showcase the versatility of the peptides for preparing compact NPs of various compositions and sizes, which are easily functionalized, and suitable for a broad range of biomedical applications.

Clarke, Samuel; Tamang, Sudarsan; Reiss, Peter; Dahan, Maxime

2011-04-01

29

Implantable fluorescence-based glucose sensor development  

NASA Astrophysics Data System (ADS)

An implantable sensor is being created that allows measurement of blood glucose through fluorescent detection of an embedded chemical assay. The sensor is based on the competitive binding reaction between the protein Concanavalin A and various saccharide molecules, specifically a glycodendrimer and glucose. Previous studies have shown the ability of an embedded chemical assay using Con A and dextran with shorter wavelength dyes to both sense changes in glucose and generate sufficient fluorescent emission to pass through the dermal tissue. However, due to the chemical constituents of the assay, multivalent binding was evident resulting in poor spectral change due to glucose within the biological range. Use of a glycodendrimer and longer wavelength dyes has improved the sensor"s spectral change due to glucose and the overall signal to noise ratio of the sensor. In this work, a description of this sensor and the results obtained from it will be presented showing a large dynamic range of fluorescence with glucose.

Ibey, Bennett L.; Yadavalli, Vamsi K.; Thomas, Hope R.; Rounds, Rebecca M.; Pishko, Michael V.; Cote, Gerard L.

2005-03-01

30

Sensitive detection of cysteine based on fluorescent silver clusters  

Microsoft Academic Search

In this work, we report the application of novel, water-soluble fluorescent Ag clusters in fluorescent sensors for detecting cysteine, an important biological analyte. The fluorescence of poly(methacrylic acid) (PMAA)-templated Ag clusters was found to be quenched effectively by cysteine, but not when the other ?-amino acids were present. By virtue of the specific response, a new, simple, and sensitive fluorescent

Li Shang; Shaojun Dong

2009-01-01

31

A rapid and simple assay for human blood malignancy engraftment, homing and chemotherapy treatment using fluorescent imaging of avian embryos.  

PubMed

Detection of grafted human cells in mice using fluorescence is a rapid and simple technique whose use is continually expanding. Robust engraftment of human hematological malignancy (HHM) lines and patient cells into the naturally immunodeficient turkey embryo has recently been demonstrated by polymerase chain reaction (PCR), fluorescence activated cell sorting (FACS) and histology. We demonstrate here that fluorescence imaging is a rapid and simple technique for detecting engraftment and homing of cells derived from HHM in turkey embryos. Raji lymphoma cells expressing a far-red fluorescent protein were injected intravascularly into turkey embryos and fluorescence was detected 8 days later in their limbs and skulls. Much stronger signals were obtained after removal of the bones from the limbs. Unlabeled Raji cells did not give a fluorescent signal. Treatment with doxorubicin dramatically reduced the fluorescent signal. Intravenously injected HL-60 leukemia cells labeled with infrared-fluorescing dye were detected in the bone marrow after 16 h. Homing was active, although some non-specific fluorescence was present. Use of fluorescence imaging of HHM in turkey embryos is therefore feasible and reduces the time, effort and expense for detecting engraftment. This technique has potential to become a high-throughput xenograft system for hematological chemotherapy development and testing, and for study of hematological cell homing. PMID:21895546

Grinberg, Igor; Dukhovny, Anna; Goldstein, Ronald S

2012-03-01

32

A Surface-Based DNA Computing for the Simple 0-1 Programming Problem  

Microsoft Academic Search

DNA computing is a novel method of solving a class of intractable computational problem, in which the computing speeds up exponentially with problem size. Up to now, many accomplishments have been made to improve its performance and increase its reliability. In the paper, we solved the simple 0-1 programming problem with fluorescence labeling techniques based on surface chemistry by attempted

Zhi-xiang Yin; Jia-xiu Zhang; Jin Xu

33

Imaging of the fluorescence spectrum of a single fluorescent molecule by prism-based spectroscopy  

Microsoft Academic Search

We have devised a novel method to visualize the fluorescence spectrum of a single fluorescent molecule using prism-based spectroscopy. Equiping a total internal reflection microscope with a newly designed wedge prism, we obtained a spectral image of a single rhodamine red molecule attached to an essential light chain of myosin. We also obtained a spectral image of single-pair fluorescence resonance

Yoshikazu Suzuki; Tomomi Tani; Kazuo Sutoh; Shinji Kamimura

2002-01-01

34

Simple interface of high-performance liquid chromatography-atomic fluorescence spectrometry hyphenated system for speciation of mercury based on photo-induced chemical vapour generation with formic acid in mobile phase as reaction reagent.  

PubMed

Photo-induced chemical vapour generation (CVG) with formic acid in mobile phase as reaction reagent was developed as interface to on-line couple HPLC with atomic fluorescence spectrometry for the separation and determination of inorganic mercury, methylmercury (MeHg), ethylmercury (EtHg) and phenylmercury (PhHg). In the developed procedure, formic acid in mobile phase was used to decompose organomercuries and reduce Hg(2+) to mercury cold vapour under UV irradiation. Therefore, no post-column reagent was used and the flow injection system in traditional procedure is omitted. A number of operating parameters including pH of mobile phase, concentration of formate, flow rate of mobile phase, length of PTFE reaction coil, flow rate of carrier gas and Na(2)S(2)O(3) in sample matrix were optimized. The limits of detection at the optimized conditions were 0.085, 0.033, 0.029 and 0.038 microg L(-1) for inorganic mercury, MeHg, EtHg and PhHg, respectively. The developed method was validated by determination of certified reference material DORM-2 and was further applied in analyses of seafood samples from Yantai port, China. The UV-CVG with formic acid simplifies the instrumentation and reduces the analytical cost significantly. PMID:18184614

Yin, Yongguang; Liu, Jingfu; He, Bin; Shi, Jianbo; Jiang, Guibin

2008-02-15

35

Preparation of a novel fluorescent nanocomposite: CeO2 / ANS by a simple method  

NASA Astrophysics Data System (ADS)

For the first time, a novel fluorescent material, composed of CeO2/ANS nanocomposites was successfully synthesized by a simple ultrasonic method, using CeO2 nanoparticles and 8-anilino-1-naphthalenesulfonic acid (ANS) as the raw materials. The samples were characterized by scanning electron microscope (SEM), photoluminescence spectroscopy and Fourier transformation infrared spectroscopy (FTIR). The results showed that the PL intensity of the CeO2/ANS nanocomposites was higher than that of both CeO2 nanoparticles and ANS powders, and the peak wavelength was also different from the peak wavelength typical of each of the used materials, which suggests that the chemical reaction occurs between CeO2 nanoparticles and ANS molecules. In addition, the effect of the ANS concentrations on the photoluminescence of the nanocomposites was also investigated.

Liu, X.; Lian, X.; Li, Y.; Zhang, N.

2012-03-01

36

Simple micro-column with multi-walled carbon nanotubes for on-line preconcentration and determination of lead in natural water by hydride generation atomic fluorescence spectrometry  

Microsoft Academic Search

A flow injection on-line preconcentration system was developed for the determination of lead by hydride generation atomic\\u000a fluorescence spectrometry (HG-AFS). It is based on a simple micro-column filled with multiwalled carbon nanotubes (MWCNTs).\\u000a The preconcentration of lead on the MWCNTs was carried out based on the adsorptive retention of analyte via on-line introducing\\u000a the sample into the micro-column system. A

Hong Wu; Hongyu Wen; Baoping Han; Baixiang Du; Jusheng Lu; Jiuying Tian

2009-01-01

37

A simple and rapid protocol for measuring neutral lipids in algal cells using fluorescence.  

PubMed

Algae are considered excellent candidates for renewable fuel sources due to their natural lipid storage capabilities. Robust monitoring of algal fermentation processes and screening for new oil-rich strains requires a fast and reliable protocol for determination of intracellular lipid content. Current practices rely largely on gravimetric methods to determine oil content, techniques developed decades ago that are time consuming and require large sample volumes. In this paper, Nile Red, a fluorescent dye that has been used to identify the presence of lipid bodies in numerous types of organisms, is incorporated into a simple, fast, and reliable protocol for measuring the neutral lipid content of Auxenochlorella protothecoides, a green alga. The method uses ethanol, a relatively mild solvent, to permeabilize the cell membrane before staining and a 96 well micro-plate to increase sample capacity during fluorescence intensity measurements. It has been designed with the specific application of monitoring bioprocess performance. Previously dried samples or live samples from a growing culture can be used in the assay. PMID:24961928

Storms, Zachary J; Cameron, Elliot; de la Hoz Siegler, Hector; McCaffrey, William C

2014-01-01

38

Economic and simple system to combine single-spot photolysis and whole-field fluorescence imaging  

PubMed Central

In the recent years, the use of light emitting diodes (LEDs) has become commonplace in fluorescence microscopy. LEDs are economical, easy to couple to commercial microscopes and provide powerful and stable light that can be triggered by TTL pulses in the range of tens of microseconds or shorter. LEDs are usually installed on the epifluorescence port of the microscope to obtain whole field illumination which is ideal for fluorescence imaging. In contrast, photolysis or channelrhodopsin stimulation often requires localised illumination, typically achieved using lasers. Here we show that insertion of a long-pass (>411 nm) filter with appropriately sized pinhole in the epifluorescence pathway, combined with dual UV/visible illumination, can produce efficient whole field visible illumination and spot UV illumination of 15–20 ?m. We tested our system by performing calcium imaging experiments combined with L-glutamate or NMDA photo-release in hippocampal neurons from brain slices or dissociated cultures, demonstrating the ability to obtain local activation of NMDA receptors exclusively in the illuminated spot. The very inexpensive and simple system that we report here will allow many laboratories with limited budget to run similar experiments in a variety of physiological applications.

Jaafari, Nadia; Henson, Mark; Graham, Jeremy; Canepari, Marco

2013-01-01

39

Fluorescent silica nanoparticle-based probe for the detection of ozone via fluorescence resonance energy transfer.  

PubMed

A fluorescence resonance energy transfer (FRET) platform for the detection of ozone was developed by combining the overlap of the fluorescence spectrum of Ru(bpy)3(2+)-doped silica nanoparticles with the absorption spectrum of indigo carmine at around 600 nm. This FRET system can be used to detect ozone simply within 10 min. Simple qualitative ozone detection methods using cotton swabs or paper were also developed. PMID:24049767

Qi, Wenjing; Wu, Di; Zhao, Jianming; Liu, Zhongyuan; Xu, Min; Anjum, Saima; Xu, Guobao

2013-11-01

40

The toolbox of fluorescence standards: flexible calibration tools for the standardization of fluorescence-based measurements  

NASA Astrophysics Data System (ADS)

To improve the reliability of fluorescence data in the life and material sciences and to enable accreditation of fluorescence techniques, standardization concepts are required that guarantee and improve the comparability of fluorescence measurements. At the core of such concepts are simple and evaluated fluorescence standards for the consideration of instrument-specific spectral and intensity distortions of measured signals and for instrument performance validation (IPV). Similarly in need are fluorescence intensity standards for the quantification from measured intensities and for signal referencing, thereby accounting for excitation light-induced intensity fluctuations. These standards should be preferably certified, especially for use in regulated areas like medical diagnostics. This encouraged us to develop liquid and solid standards for different fluorescence parameters and techniques for use under routine measurement conditions in different formates. Special emphasis was dedicated to the determination and control of the spectral responsivity of detection systems, wavelength accuracy, homogeneity of illumination, and intensity referencing for e.g. spectrofluorometers, fluorescence sensors and confocal laser scanning fluorescence microscopes. Here, we will present design concepts and examples for mono- and multifunctional fluorescence standards that provide traceability to radiometric units and present a first step towards a toolbox of standards.

Resch-Genger, Ute; Hoffmann, K.; Würth, C.; Behnke, T.; Hoffmann, A.; Pfeifer, D.; Engel, A.

2010-04-01

41

A duplexed microsphere-based fluorescent immunoassay.  

PubMed

Microsphere-based immunoassays are described for the simultaneous measurement of the clinically important drugs digoxin and theophylline. Competitive immunoassays were performed using haptenized microspheres and antibodies labeled with horseradish peroxidase. Enzyme-catalyzed reporter deposition (CARD) resulted in immunofluorescence signal amplification. Two encoding dyes were used to differentiate analytical signals from microspheres containing assays for the two analytes. An epifluorescence microscope and a CCD camera interfaced with a computer were utilized to measure fluorescence signals of individual microspheres. The microspheres from a duplexed assay were mounted on microscope slides as well as inserted into wells etched into the distal ends of optical imaging fibers. Fluorescence images from both formats were captured. In the experiments using microscope slides, the immunoassays were successfully duplexed and only marginal interferences at high analyte concentrations were observed. Preliminary results suggest that simultaneous determination of the two analytes using a fiber-based sensor-array format is feasible, but requires further development before precise quantitative analyses are possible. PMID:11401295

Szurdoki, F; Michael, K L; Walt, D R

2001-04-15

42

Development of a Novel Efficient Fluorescence-Based Plaque Reduction Microneutralization Assay for Measles Virus Immunity  

Microsoft Academic Search

The measurement of functional measles virus-specific neutralizing antibodies is of considerable interest for vaccine-related research. In this study, we developed and standardized a simple, rapid, highly sensitive, and reproducible fluorescence-based plaque reduction microneutralization (PRMN) assay with visual and auto- mated readout, using a recombinant measles virus engineered to express enhanced green fluorescent protein. The assay is performed in micro format,

Iana H. Haralambieva; Inna G. Ovsyannikova; Robert A. Vierkant; Gregory A. Poland

2008-01-01

43

Rapid human metapneumovirus microneutralization assay based on green fluorescent protein expression  

Microsoft Academic Search

We describe a simple and expedited microneutralization assay for human metapneumovirus virus (HMPV) based on a recombinant HMPV expressing the enhanced green fluorescent protein (rHMPV-GFP). Test serum dilutions were incubated with fixed amounts of rHMPV-GFP and inoculated onto Vero cells, and the growth of non-neutralized rHMPV-GFP was visualized by fluorescent microscopy of living cells. A preliminary titer could be determined

Stéphane Biacchesi; Mario H. Skiadopoulos; Lijuan Yang; Brian R. Murphy; Peter L. Collins; Ursula J. Buchholz

2005-01-01

44

Spirobenzopyran-based photochromic nanohybrids with photoswitchable fluorescence  

Microsoft Academic Search

The preparation and performance characterization of about 40nm spirobenzopyran-based photochromic nanohybrids with photoswitchable fluorescence are presented. The nanohybrids were fabricated by means of a modified miniemulsion polymerization process, in which hydrophobic spirobenzopyran and the matched fluorescent dyes are intermolecularly hybridized and embedded in the nanoscale crosslinked polymeric matrix. The obtained nanohybrids with high relative fluorescence quantum yield (Q) exhibited superior

Zhenkun Hu; Qing Zhang; Minzhao Xue; Qiaorong Sheng; Yan-gang Liu

2008-01-01

45

A Modular Strategy for Development of RNA-Based Fluorescent Sensors  

NASA Astrophysics Data System (ADS)

Fluorescent biosensors that directly transduce binding events of small molecules into optical signals are valuable tools in the areas of therapeutics and diagnostics. However, construction of fluorescent biosensors from macromolecular receptors with desired characteristics, such as detection wavelengths and concentration ranges for ligand detection, is not a straightforward task. A ribonucleopeptide (RNP) receptor was easy to convert to a fluorescent RNP sensor without chemically modifying the nucleotide in the ligand-binding RNA. The strategy of converting the ligand-binding RNP receptor to a fluorescent RNP sensor was applied to generate fluorescent ligandbinding RNP libraries by utilizing a pool of RNA subunits obtained from the in vitro selection of ATP-binding RNPs and various fluorophore-modified peptide subunits. Simple screening of the fluorescent RNP library based on the fluorescence emission intensity changes in the absence and presence of the ligand afforded a wide variety of fluorescent RNP sensors with emission wavelengths ranged from 390 to 670 nm. Screening of the fluorescence emission intensity changes in the presence of increasing concentrations of ligand provided RNP sensors responding at wide concentration ranges of ligand. The combinatorial strategy using the modular RNP receptor enables tailoring of a fluorescent sensor for a specific ligand without knowledge of detailed structural information for the macromolecular receptor.

Fukuda, Masatora; Hasegawa, Tetsuya; Hayashi, Hironori; Morii, Takashi

46

Photoswitch based on remarkably simple naphthopyrans  

Microsoft Academic Search

Photochromic switches built around 5-carbonyl-3,3-diphenyl-3H-naphtho[2,1-b]pyran unit have been synthesized. Their open forms are constituted of a 1:1 ratio of TC and TT-isomers according to 19F and 1H NMR investigations. Electrocyclization of TT isomers back to the closed form is efficiently achieved upon visible irradiation whereas it has been found to be a particularly unfavoured thermal process. These simple 2H-chromenes could

Xavier Sallenave; Stéphanie Delbaere; Gaston Vermeersch; Ahmed Saleh; Jean-Luc Pozzo

2005-01-01

47

Simple, Rapid and Inexpensive Quantitative Fluorescent PCR Method for Detection of Microdeletion and Microduplication Syndromes  

PubMed Central

Because of economic limitations, the cost-effective diagnosis of patients affected with rare microdeletion or microduplication syndromes is a challenge in developing countries. Here we report a sensitive, rapid, and affordable detection method that we have called Microdeletion/Microduplication Quantitative Fluorescent PCR (MQF-PCR). Our procedure is based on the finding of genomic regions with high homology to segments of the critical microdeletion/microduplication region. PCR amplification of both using the same primer pair, establishes competitive kinetics and relative quantification of amplicons, as happens in microsatellite-based Quantitative Fluorescence PCR. We used patients with two common microdeletion syndromes, the Williams-Beuren syndrome (7q11.23 microdeletion) and the 22q11.2 microdeletion syndromes and discovered that MQF-PCR could detect both with 100% sensitivity and 100% specificity. Additionally, we demonstrated that the same principle could be reliably used for detection of microduplication syndromes, by using patients with the Lubs (MECP2 duplication) syndrome and the 17q11.2 microduplication involving the NF1 gene. We propose that MQF-PCR is a useful procedure for laboratory confirmation of the clinical diagnosis of microdeletion/microduplication syndromes, ideally suited for use in developing countries, but having general applicability as well.

Stofanko, Martin; Goncalves-Dornelas, Higgor; Cunha, Pricila Silva; Pena, Heloisa B.; Vianna-Morgante, Angela M.; Pena, Sergio Danilo Junho

2013-01-01

48

A highly selective quinoline-based fluorescent sensor for Zn(II).  

PubMed

A quinoline-based simple receptor (bis(2-quinolinylmethyl)benzylamine = 1) as a Zn(2+) selective fluorescent chemosensor showed a large fluorescent enhancement with a blue shift in the presence of Zn(2+) which is attributed to a chelation enhanced fluorescence (CHEF) effect with inhibition of a photoinduced electron transfer (PET) process of 1. In particular, this receptor could clearly distinguish Zn(2+) from Cd(2+). The binding mode of 1 and Zn(2+) was found to be a 1:1 and confirmed by Job plot, (1)H NMR titration and ESI-mass spectrometry analysis. PMID:24161851

Kim, Hyun; Kang, Juhye; Kim, Kyung Beom; Song, Eun Joo; Kim, Cheal

2014-01-24

49

Simple and sensitive determination of five quinolones in food by liquid chromatography with fluorescence detection.  

PubMed

A simple and sensitive high-performance liquid chromatographic (HPLC) method has been developed for the determination of five different quinolones: enrofloxacin, ciprofloxacin, sarafloxacin, oxolinic acid and flumequine in pork and salmon muscle. The method includes one extraction and clean-up step for the five quinolones together which are detected in two separated HPLC runs by means of their fluorescence. The proposed analytical method involves homogenizing of the tissue sample with 0.05 M phosphate buffer, pH 7.4 and clean-up by Discovery DS-18 cartridges. For chromatographic separation a Symmetry C(18) column is used in two different runs: (1) ciprofloxacin, enrofloxacin and sarafloxacin with acetonitrile-0.02 M phosphate buffer pH 3.0 (18:82) as mobile phase and the detector at excitation wavelength: 280 nm and emission wavelength 450 nm; and (2) oxolinic acid and flumequine with acetonitrile-0.02 M phosphate buffer pH 3.0 (34:66) as mobile phase and excitation wavelength: 312 nm and emission wavelength: 366 nm. Detection limit was as low as 5 ng g(-1), except for sarafloxacin which had a limit of 10 ng g(-1). Standard curves using blank muscle tissues spiked at different levels showed a good linear correlation coefficient, r(2) higher than 0.999 for all quinolones. PMID:12742128

Ramos, Macarena; Aranda, Angela; Garcia, Elena; Reuvers, Thea; Hooghuis, Henny

2003-06-15

50

A FLUORESCENCE BASED ASSAY FOR DNA DAMAGE INDUCED BY STYRENE OXIDE  

EPA Science Inventory

A rapid and simple assay to detect DNA damage to calf thymus DNA caused by styrene oxide (SO) is reported. This assay is based on changes observed in the melting and annealing behavior of the damaged DNA. The melting annealing process was monitored using a fluorescence indicat...

51

A FLUORESCENCE BASED ASSAY FOR DNA DAMAGE INDUCED BY RADIATION, CHEMICAL MUTAGENS AND ENZYMES  

EPA Science Inventory

A simple and rapid assay to detect DNA damage is reported. This novel assay is based on changes in melting/annealing behavior and facilitated using certain dyes that increase their fluorescence upon association with double stranded (ds)DNA. Damage caused by ultraviolet (UV) ra...

52

A FLUORESCENCE BASED ASSAY FOR DNA DAMAGE: INDUCED BY RADIATION, CHEMICALS AND ENZYMES  

EPA Science Inventory

A simple and rapid assay to detect DNA damage is reported. This assay is based on the ability of certain dyes to fluoresce upon intercalation with dsDNA. Damage caused by ultraviolet (UV) radiation, chemicals or restriction enzymes is detected using this assay. UV radiation at...

53

Development of Highly Fluorescent Materials Based on Thiophenylimidazole Dyes  

NASA Technical Reports Server (NTRS)

Organic fluorescent materials are expected to find many potential applications in optical devices and photo-functionalized materials. Although many investigations have been focused on heterocyclic compounds such as coumarins, bipyridines, rhodamines, and pyrrole derivatives, little is known for fluorescent imidazole materials. We discovered that one particular class of imidazole derivatives is highly fluorescent. A series of monomeric and polymeric based fluorescent dyes were prepared containing a thiophene unit at the second position of the imidazole ring. Dependence of fluorescence efficiency on parameters such as solvent polarity and substituent groups has been investigated. It was found that a formyl group at the 2-position of the thiophene ring dramatically enhance fluorescence properties. Ion recognition probes indicated their potential as sensor materials. These fluorophores have flexibility for introduction of versatile substituent groups that could improve the fluorescence efficiency and sensor properties.

Santos, Javier; Bu, Xiu R.; Mintz, Eric A.; Meador, Michael A. (Technical Monitor)

2000-01-01

54

A simple and sensitive UFLC-fluorescence method for endocrine disrupters determination in marine waters.  

PubMed

The present study proposes a fast and simple analytical methodology employing C18 SPE cartridges (for preconcentration and clean-up), and a ultra-fast liquid chromatography coupled to fluorescence detector (UFLC-FLD) for determination of the following endocrine disrupters (ED): bisphenol A (BPA), 4-n-nonylphenol (4NNP), 4-n-octylphenol (4NOP), 4-t-octylphenol (4TOP), estriol (E3), estrone (E1), 17?-estradiol (E2) and 17?-ethynylestradiol (EE2) in seawater. The proposed method was developed, optimized and validated. Separation was done by a total running time of 10 min in a Shim-pack XR-ODS C-18 (2.0 mm ID × 50 mm) chromatographic column, mobile phases were acetonitrile/ultra-pure water under gradient programming; eluent flow rate at 0.120 mL min(-1); column temperature set at 60 °C; emission wavelength of 306 nm and excitation wavelength of 280 nm. The method was validated through assessment of the following parameters: linear range, linearity, selectiveness, precision, recovery test, limit of detection (LOD), and limit of quantification (LOQ). Recoveries ranged from 91% (for EE2) to 104% (for 4NNP) and also was found a suitable repeatability (RSD <4.5%) for all considered compounds. LOD and LOQ ranged from 2.0 ng L(-1) (EE2) to 23 ng L(-1) (E1) and 9.3 ng L(-1) (EE2) to 96 ng L(-1) (E1), respectively. The analytical method using SPE UFLC-FLD was applied to seawater samples collected from Todos os Santos Bay (BTS), Brazil to determine the concentration of eight ED. PMID:24209326

Lisboa, Normando S; Fahning, Cristiane S; Cotrim, Gabriel; dos Anjos, Jeancarlo P; de Andrade, Jailson B; Hatje, Vanessa; da Rocha, Gisele O

2013-12-15

55

A simple fluorescent technique for screening cervical cells prior to nuclear analysis.  

PubMed

Monolayer spreads of cervical cells were prepared and stained with haematoxylin and rhodamine-alpha-N-agmatine, a fluorescent marker for a cell surface protease. Mature epithelial cells from normal cervices lacked this cell surface enzyme and did not fluoresce. The abnormal cells possessed the cell surface enzyme, bound the probe and were quickly detected by fluorescence microscopy. The degree of abnormality of these fluorescent cells was determined by examination of their nuclear details, with the result that mild, moderate and severe dyskaryotic cells could be defined. PMID:1295461

Steven, F S; Johnson, J; Eason, P

1992-01-01

56

Genetically encoded biosensors based on engineered fluorescent proteins†‡  

PubMed Central

Fluorescent proteins have revolutionized cell biology by allowing researchers to non-invasively peer into the inner workings of cells and organisms. While the most common applications of fluorescent proteins are to image expression, localization, and dynamics of protein chimeras, there is a growing interest in using fluorescent proteins to create biosensors for minimally invasive imaging of concentrations of ions and small molecules, the activity of enzymes, and changes in the conformation of proteins in living cells. This tutorial review provides an overview of the progress made in the development of fluorescent protein-based biosensors to date.

Davidson, Michael W.

2010-01-01

57

Fluorescence-based optical sensor design for molecularly imprinted polymers  

Microsoft Academic Search

A Monte Carlo model was developed to analyze the sensitivity and the performance of a fluorescence-based molecularly imprinted polymer (MIP) sensor. The MIP sensor consisted of highly cross-linked polyurethane containing anthracene binding sites coated on a transparent substrate. The optical properties of MIPs, the quantum yields of anthracene within MIPs, and the fluorescence of MIPs were measured. The rebinding capacity

Yin-Chu Chen; Jennifer J. Brazier; Mingdi Yan; Paulo R. Bargo; Scott A. Prahl

2004-01-01

58

A simple model for understanding the fluorescence behavior of Au25 nanoclusters  

NASA Astrophysics Data System (ADS)

In this work, we synthesized Au25 nanoclusters protected by 2-(naphthalen-2-yl)ethanethiolate. Our experiments revealed that the luminescence of this nanocluster consists of two bands, namely, band I centered at 740 nm and band II centered at 680 nm. Compared with 2-phenylethanethiolate protected Au25 nanoclusters, this new nanocluster has a much higher QY (quantum yield) value (6.5 times higher). Fluorescence lifetime measurements showed multiple components, i.e. 0.15 ns, ~20 ns and ~150 ns. With an increase in the electropositivity of the nanocluster, the fluorescence intensity of the nanocluster exhibits a significant enhancement. Since the 2-(naphthalen-2-yl)ethanethiolate protected Au25 nanocluster shares the same Au13/Au12 core-shell structure as the 2-phenylethanethiolate protected nanocluster, the band II fluorescence implies that the surface ligands play a major role in the origin of the fluorescence.

Wang, Shuxin; Zhu, Xiuyi; Cao, Tiantian; Zhu, Manzhou

2014-05-01

59

A simple model for understanding the fluorescence behavior of Au25 nanoclusters.  

PubMed

In this work, we synthesized Au25 nanoclusters protected by 2-(naphthalen-2-yl)ethanethiolate. Our experiments revealed that the luminescence of this nanocluster consists of two bands, namely, band I centered at 740 nm and band II centered at 680 nm. Compared with 2-phenylethanethiolate protected Au25 nanoclusters, this new nanocluster has a much higher QY (quantum yield) value (6.5 times higher). Fluorescence lifetime measurements showed multiple components, i.e. 0.15 ns, ?20 ns and ?150 ns. With an increase in the electropositivity of the nanocluster, the fluorescence intensity of the nanocluster exhibits a significant enhancement. Since the 2-(naphthalen-2-yl)ethanethiolate protected Au25 nanocluster shares the same Au13/Au12 core-shell structure as the 2-phenylethanethiolate protected nanocluster, the band II fluorescence implies that the surface ligands play a major role in the origin of the fluorescence. PMID:24736871

Wang, Shuxin; Zhu, Xiuyi; Cao, Tiantian; Zhu, Manzhou

2014-06-01

60

Spectral properties of a simple azine Schiff base and its sensing ability towards protic environment through hydrogen bonding interaction.  

PubMed

A simple azine linkage containing Schiff base p-N,N-diethylaminobenzaldazine (PDEAB) has been synthesized and its spectroscopic properties have been investigated using steady state absorption and fluorescence measurement. Both the absorption and emission studies indicate that the compound PDEAB forms intermolecular hydrogen bond with protic solvents. The formation of intermolecular hydrogen bond between PDEAB and protic solvents is further verified by Quantum chemical calculation using Density Functional Theory (DFT) (B3LYP/6-31++G(d,p)) and Natural Bond Orbital (NBO) analysis. The non-fluorescent nature (fluorescence off) of PDEAB in aprotic environment can be switched over to a fluorescent system (fluorescence on) in presence of protic solvents and hence this molecule can be used as highly sensitive fluorosensor for protic solvent in aprotic medium like ACN or DOX. PMID:23835054

Ray, Debarati; Dalapati, Sasanka; Guchhait, Nikhil

2013-11-01

61

PAMAM structure-based multifunctional fluorescent conjugates for improved fluorescent labelling of biomacromolecules.  

PubMed

Fluorescent probes are of increasing interest in medicinal and biological applications for the elucidation of the structures and functions of healthy as well as tumour cells. The quality of these investigations is determined by the intensity of the fluorescence signal. High dye/carrier ratios give strong signals. However, these are achieved by the occupation of a high number of derivatisation sites and therefore are accompanied by strong structural alterations of the carrier. Hence, polyvalent substances containing a high number of fluorescent dyes would be favourable because they would allow the introduction of many dyes at one position of the compound to be labelled.A large number of different dyes have been investigated to determine the efficiency of coupling to a dendrimer scaffold and the fluorescence properties of the oligomeric dyes, but compounds that fulfil the requirements of both strong fluorescence signals and reactivities are rare. Herein we describe the synthesis and characterisation of dye oligomers containing dansyl-, 7-nitro-2,1,3-benzoxadiazol-4-yl- (NBD), coumarin-343, 5(6)-carboxyfluorescein and sulforhodamine B2 moieties based on polyamidoamine (PAMAM) dendrimers. The PAMAM dendrimers were synthesised by an improved protocol that yielded highly homogeneous scaffolds with up to 128 conjugation sites. When comparing the fluorescent properties of the dye oligomers it was found that only the dansylated dendrimers met the requirements of enhanced fluorescence signals. The dendrimer containing 16 fluorescent dyes was conjugated to the anti-epidermal-growth-factor receptor (EGFR) antibody hMAb425 as a model compound to show the applicability of the dye multimer compounds. This conjugate revealed a preserved immunoreactivity of 54%.We demonstrate the applicability of the dye oligomers to the efficient and applicable labelling of proteins and other large molecules that enables high dye concentrations and therefore high contrasts in fluorescence applications. PMID:18752247

Wängler, C; Moldenhauer, G; Saffrich, R; Knapp, E-M; Beijer, B; Schnölzer, M; Wängler, B; Eisenhut, M; Haberkorn, U; Mier, W

2008-01-01

62

Exploration of fluorescent protein voltage probes based on circularly permuted fluorescent proteins.  

PubMed

Genetically encoded fluorescent protein (FP) voltage sensors are promising tools for optical monitoring of the electrical activity of cells. Over the last decade, several designs of fusion proteins have been explored and some of them have proven to be sensitive enough to record membrane voltage transients from single mammalian cells. Most prominent are the families of voltage sensitive fluorescent proteins (VSFPs) that utilize the voltage sensor domain (VSD) of Ciona intestinalis voltage sensor-containing phosphatase (Ci-VSP). The voltage sensitivity of the fluorescence readout of these previously reported membrane potential indicators is achieved either via a change in the efficiency of fluorescence resonance energy transfer between two FP spectral variants or via modulation in the fluorescence intensity of a single FP. Here, we report our exploration on a third VSFP design principle based on circularly permuted fluorescent protein (cpFP) variants. Using circularly permuted EGFP derived from GCaMP2 and two newly generated circularly permuted variants of the far-red emitting protein named mKate, we generated and characterized a series of voltage-sensitive probes wherein the cpFPs were fused to the VSD of Ci-VSP. The most promising variants were based on circularly permuted mKate with new N- and C-termini given by residues 180 and 182. Even so their voltage sensitivity was relatively modest, they constitute a proof of principle for this novel protein design. PMID:19862342

Gautam, Sunita Ghimire; Perron, Amelie; Mutoh, Hiroki; Knöpfel, Thomas

2009-01-01

63

Exploration of Fluorescent Protein Voltage Probes Based on Circularly Permuted Fluorescent Proteins  

PubMed Central

Genetically encoded fluorescent protein (FP) voltage sensors are promising tools for optical monitoring of the electrical activity of cells. Over the last decade, several designs of fusion proteins have been explored and some of them have proven to be sensitive enough to record membrane voltage transients from single mammalian cells. Most prominent are the families of voltage sensitive fluorescent proteins (VSFPs) that utilize the voltage sensor domain (VSD) of Ciona intestinalis voltage sensor-containing phosphatase (Ci-VSP). The voltage sensitivity of the fluorescence readout of these previously reported membrane potential indicators is achieved either via a change in the efficiency of fluorescence resonance energy transfer between two FP spectral variants or via modulation in the fluorescence intensity of a single FP. Here, we report our exploration on a third VSFP design principle based on circularly permuted fluorescent protein (cpFP) variants. Using circularly permuted EGFP derived from GCaMP2 and two newly generated circularly permuted variants of the far-red emitting protein named mKate, we generated and characterized a series of voltage-sensitive probes wherein the cpFPs were fused to the VSD of Ci-VSP. The most promising variants were based on circularly permuted mKate with new N- and C-termini given by residues 180 and 182. Even so their voltage sensitivity was relatively modest, they constitute a proof of principle for this novel protein design.

Gautam, Sunita Ghimire; Perron, Amelie; Mutoh, Hiroki; Knopfel, Thomas

2009-01-01

64

Reversible "off-on" fluorescent chemosensor for Hg 2+ based on rhodamine derivative  

NASA Astrophysics Data System (ADS)

A novel and simple fluorescent chemosensor based on rhodamine was designed and synthesized to detect Hg 2+ with high selectivity. The structure of chemosensor 1 was characterized by IR, 1H NMR, and HRMS spectroscopies. Chemosensor 1 exhibited distinct fluorescent and colorimetric changes toward Hg 2+ in an ethanol/water (80/20, v/v) solution, which resulted in the formation of 1/Hg 2+ complex with the Hg 2+-induced ring opening of the spirolactam ring in rhodamine. The reversibility of chemosensor 1 was verified through its spectral response toward Hg 2+ ions and TBAI (tetrabutylammonium iodide) titration experiments.

Liu, Weimin; Chen, Jianhong; Xu, Liwei; Wu, Jiasheng; Xu, Haitao; Zhang, Hongyan; Wang, Pengfei

2012-01-01

65

Highly Fluorescent BF2 Complexes of Hydrazine-Schiff Base Linked Bispyrrole.  

PubMed

A series of BF2 complexes of hydrazine-Schiff base linked bispyrrole have been prepared from a simple two-step reaction from commercially available substances and are highly fluorescent in solution, film, and solid states with larger Stokes shift and excellent photostabilities comparable or even super to those of their BODIPY analogues. These resultant fluorescent dyes are highly susceptible to the postfunctionalization, as demonstrated in this work via the Knoevenagel condensation to introducing functionalities or tether groups to the chromophore. PMID:24850322

Yu, Changjiang; Jiao, Lijuan; Zhang, Ping; Feng, Zeya; Cheng, Chi; Wei, Yun; Mu, Xiaolong; Hao, Erhong

2014-06-01

66

Resolution and enhancement in nanoantenna-based fluorescence microscopy.  

PubMed

Single gold nanoparticles can act as nanoantennas for enhancing the fluorescence of emitters in their near fields. Here we present experimental and theoretical studies of scanning antenna-based fluorescence microscopy as a function of the diameter of the gold nanoparticle. We examine the interplay between fluorescence enhancement and spatial resolution and discuss the requirements for deciphering single molecules in a dense sample. Resolutions better than 20 nm and fluorescence enhancement up to 30 times are demonstrated experimentally. By accounting for the tip shaft and the sample interface in finite-difference time-domain calculations, we explain why the measured fluorescence enhancements are higher in the presence of an interface than the values predicted for a homogeneous environment. PMID:19886647

Eghlidi, Hadi; Lee, Kwang Geol; Chen, Xue-Wen; Götzinger, Stephan; Sandoghdar, Vahid

2009-12-01

67

A rapid, simple measurement of human albumin in whole blood using a fluorescence immunoassay (I)  

Microsoft Academic Search

Background: Human serum albumin (HSA) is the most abundant plasma protein and plays key a role in metabolism. The variation in albumin concentration provides valuable information related to metabolic diseases and diagnostic application. Methods: We constructed two assay systems to quantify the albumin concentration. The immunoassay used a fluorescence (FL) dye to detect albumin in samples and employed the conventional

Sunga Choi; Eui Yul Choi; Dong Joon Kim; Jae Hoon Kim; Tai Sun Kim; Sang Wook Oh

2004-01-01

68

Nonmydriatic fluorescence-based quantitative imaging of human macular pigment distributions.  

PubMed

We have developed a CCD-camera-based nonmydriatic instrument that detects fluorescence from retinal lipofuscin chromophores ("autofluorescence") as a means to indirectly quantify and spatially image the distribution of macular pigment (MP). The lipofuscin fluorescence intensity is reduced at all retinal locations containing MP, since MP has a competing absorption in the blue-green wavelength region. Projecting a large diameter, 488 nm excitation spot onto the retina, centered on the fovea, but extending into the macular periphery, and comparing lipofuscin fluorescence intensities outside and inside the foveal area, it is possible to spatially map out the distribution of MP. Spectrally selective detection of the lipofuscin fluorescence reveals an important wavelength dependence of the obtainable image contrast and deduced MP optical density levels, showing that it is important to block out interfering fluorescence contributions in the detection setup originating from ocular media such as the lens. Measuring 70 healthy human volunteer subjects with no ocular pathologies, we find widely varying spatial extent of MP, distinctly differing distribution patterns of MP, and strongly differing absolute MP levels among individuals. Our population study suggests that MP imaging based on lipofuscin fluorescence is useful as a relatively simple, objective, and quantitative noninvasive optical technique suitable to rapidly screen MP levels and distributions in healthy humans with undilated pupils. PMID:16985523

Sharifzadeh, Mohsen; Bernstein, Paul S; Gellermann, Werner

2006-10-01

69

Nonmydriatic fluorescence-based quantitative imaging of human macular pigment distributions  

PubMed Central

We have developed a CCD-camera-based nonmydriatic instrument that detects fluorescence from retinal lipofuscin chromophores (“autofluorescence”) as a means to indirectly quantify and spatially image the distribution of macular pigment (MP). The lipofuscin fluorescence intensity is reduced at all retinal locations containing MP, since MP has a competing absorption in the blue–green wavelength region. Projecting a large diameter, 488 nm excitation spot onto the retina, centered on the fovea, but extending into the macular periphery, and comparing lipofuscin fluorescence intensities outside and inside the foveal area, it is possible to spatially map out the distribution of MP. Spectrally selective detection of the lipofuscin fluorescence reveals an important wavelength dependence of the obtainable image contrast and deduced MP optical density levels, showing that it is important to block out interfering fluorescence contributions in the detection setup originating from ocular media such as the lens. Measuring 70 healthy human volunteer subjects with no ocular pathologies, we find widely varying spatial extent of MP, distinctly differing distribution patterns of MP, and strongly differing absolute MP levels among individuals. Our population study suggests that MP imaging based on lipofuscin fluorescence is useful as a relatively simple, objective, and quantitative noninvasive optical technique suitable to rapidly screen MP levels and distributions in healthy humans with undilated pupils.

Sharifzadeh, Mohsen; Bernstein, Paul S.; Gellermann, Werner

2011-01-01

70

Nonmydriatic fluorescence-based quantitative imaging of human macular pigment distributions  

NASA Astrophysics Data System (ADS)

We have developed a CCD-camera-based nonmydriatic instrument that detects fluorescence from retinal lipofuscin chromophores ("autofluorescence") as a means to indirectly quantify and spatially image the distribution of macular pigment (MP). The lipofuscin fluorescence intensity is reduced at all retinal locations containing MP, since MP has a competing absorption in the blue-green wavelength region. Projecting a large diameter, 488 nm excitation spot onto the retina, centered on the fovea, but extending into the macular periphery, and comparing lipofuscin fluorescence intensities outside and inside the foveal area, it is possible to spatially map out the distribution of MP. Spectrally selective detection of the lipofuscin fluorescence reveals an important wavelength dependence of the obtainable image contrast and deduced MP optical density levels, showing that it is important to block out interfering fluorescence contributions in the detection setup originating from ocular media such as the lens. Measuring 70 healthy human volunteer subjects with no ocular pathologies, we find widely varying spatial extent of MP, distinctly differing distribution patterns of MP, and strongly differing absolute MP levels among individuals. Our population study suggests that MP imaging based on lipofuscin fluorescence is useful as a relatively simple, objective, and quantitative noninvasive optical technique suitable to rapidly screen MP levels and distributions in healthy humans with undilated pupils.

Sharifzadeh, Mohsen; Bernstein, Paul S.; Gellermann, Werner

2006-10-01

71

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

PubMed

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

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

2014-01-21

72

Fluorescence detection of Pb(2+) based on the DNA sequence functionalized CdS quantum dots.  

PubMed

In this paper, we have developed a simple and rapid method for the detection of Pb(2+) based on the DNA sequence capped CdS quantum dots (QDs). We utilized the designed guanine (G)-rich DNA sequence (PS2.M) as a coating reagent to synthesize the DNA-capped CdS QDs. The designed G-rich DNA sequence PS2.M can bind with hemin to form G-quadruplex/hemin complex with K(+), accompanied by the fluorescence quenching of CdS QDs via the photoinduced electron transfer. Pb(2+) can induce conformational changes in the G-quadruplex/hemin complex to release the hemin molecules, so the quenched fluorescence of CdS QDs could be recovered. Therefore, the new fluorescent analysis system could be applied for the detection of Pb(2+) based on the label-free DNA sequence capped CdS QDs. PMID:24607617

Liu, Siyu; Na, Weidan; Pang, Shu; Su, Xingguang

2014-08-15

73

Fluorescence quenching of Rhodamine B base by two amines  

NASA Astrophysics Data System (ADS)

Fluorescence quenching of Rhodamine B base (RhB) in DMF solution has been studied at different concentrations of the amine Triethyl amine (TEA) and n-butyl amine (NBA) at room temperature. It has been observed that the fluorescence intensity of RhB decrease with increase in the concentration of the TEA and NBA. It has been observed that the quenching due to amines proceeds via dynamic quenching process. The rate constants for the quenching process have been calculated using Stern-Volmer equation. Time resolved fluorescence study and 1H NMR spectral study have also been carried out and discussed.

Bakkialakshmi, S.; Selvarani, P.; Chenthamarai, S.

2013-03-01

74

Fluorescence quenching of Rhodamine B base by two amines.  

PubMed

Fluorescence quenching of Rhodamine B base (RhB) in DMF solution has been studied at different concentrations of the amine Triethyl amine (TEA) and n-butyl amine (NBA) at room temperature. It has been observed that the fluorescence intensity of RhB decrease with increase in the concentration of the TEA and NBA. It has been observed that the quenching due to amines proceeds via dynamic quenching process. The rate constants for the quenching process have been calculated using Stern-Volmer equation. Time resolved fluorescence study and (1)H NMR spectral study have also been carried out and discussed. PMID:23353689

Bakkialakshmi, S; Selvarani, P; Chenthamarai, S

2013-03-15

75

A Simple Rule-Based Part of Speech Tagger  

Microsoft Academic Search

Automatic part of speech tagging is an area of natural language processing where statistical techniques have been more successful than rule-based methods. In this paper, we present a simple rule-based part of speech tagger which automatically acquires its rules and tags with accuracy comparable to stochastic taggers. The rule-based tagger has many advantages over these taggers, including: a vast reduction

Eric Brill

1992-01-01

76

Tryptophan-based chromophore in fluorescent proteins can be anionic  

PubMed Central

Cyan fluorescent proteins (CFP) with tryptophan66-based chromophore are widely used for live cell imaging. In contrast to green and red fluorescent proteins, no charged states of the CFP chromophore have been described. Here, we studied synthetic CFP chromophore and found that its indole group can be deprotonated rather easily (pKa 12.4).We then reproduced this effect in the CFP mCerulean by placing basic amino acids in the chromophore microenvironment. As a result, green-emitting variant with an anionic chromophore and key substitution Val61Lys was obtained. This is the first evidence strongly suggesting that tryptophan-based chromophores in fluorescent proteins can exist in an anionic charged state. Switching between protonated and deprotonated Trp66 in fluorescent proteins represents a new unexplored way to control their spectral properties.

Sarkisyan, Karen S.; Yampolsky, Ilia V.; Solntsev, Kyril M.; Lukyanov, Sergey A.; Lukyanov, Konstantin A.; Mishin, Alexander S.

2012-01-01

77

A quick and simple FISH protocol with hybridization-sensitive fluorescent linear oligodeoxynucleotide probes.  

PubMed

Fluorescence in situ hybridization (FISH) is a powerful tool used in karyotyping, cytogenotyping, cancer diagnosis, species specification, and gene-expression analysis. Although widely used, conventional FISH protocols are cumbersome and time consuming. We have now developed a FISH method using exciton-controlled hybridization-sensitive fluorescent oligodeoxynucleotide (ECHO) probes. ECHO-FISH uses a 25-min protocol from fixation to mounting that includes no stringency washing steps. We use ECHO-FISH to detect both specific DNA and RNA sequences with multicolor probes. ECHO-FISH is highly reproducible, stringent, and compatible with other fluorescent cellular labeling techniques. The resolution allows detection of intranuclear speckles of poly(A) RNA in HeLa cells and dissociated hippocampal primary cultures, and mRNAs in the distal dendrites of hippocampal neurons. We also demonstrate detection of telomeric and centromeric DNA on metaphase mouse chromosomes. The simplicity of the ECHO-FISH method will likely accelerate cytogenetic and gene-expression analysis with high resolution. PMID:22101241

Wang, Dan Ohtan; Matsuno, Hitomi; Ikeda, Shuji; Nakamura, Akiko; Yanagisawa, Hiroyuki; Hayashi, Yasunori; Okamoto, Akimitsu

2012-01-01

78

A novel immunoassay based on the dissociation of immunocomplex and fluorescence quenching by gold nanoparticles  

Microsoft Academic Search

This study reports a novel, simple and sensitive immunoassay using fluorescence quenching caused by gold nanoparticles coated with antibody. The method is based on a non-competitive heterogeneous immunoassay of human IgG conducted by the typical procedure of sandwich immunocomplex formation. Goat anti-human IgG was first adsorbed on polystyrene microwells, and human IgG analyte was captured by the primary antibody and

Zhaofeng Peng; Zhaopeng Chen; Jianhui Jiang; Xiaobing Zhang; Guoli Shen; Ruqin Yu

2007-01-01

79

Unexpected complex formation between coralyne and cyclic diadenosine monophosphate providing a simple fluorescent turn-on assay to detect this bacterial second messenger.  

PubMed

Cyclic diadenosine monophosphate (c-di-AMP) has emerged as an important dinucleotide that is involved in several processes in bacteria, including cell wall remodeling (and therefore resistance to antibiotics that target bacterial cell wall). Small molecules that target c-di-AMP metabolism enzymes have the potential to be used as antibiotics. Coralyne is known to form strong complexes with polyadenine containing eight or more adenine stretches but not with short polyadenine oligonucleotides. Using a panel of techniques (UV, both steady state fluorescence and fluorescence lifetime measurements, circular dichroism (CD), NMR, and Job plots), we demonstrate that c-di-AMP, which contains only two adenine bases is an exception to this rule and that it can form complexes with coralyne, even at low micromolar concentrations. Interestingly, pApA (the linear analog of c-di-AMP that also contains two adenines) or cyclic diguanylate (c-di-GMP, another nucleotide second messenger in bacteria) did not form any complex with coralyne. Unlike polyadenine, which forms a 2:1 complex with coralyne, c-di-AMP forms a higher order complex with coralyne (?6:1). Additionally, whereas polyadenine reduces the fluorescence of coralyne when bound, c-di-AMP enhances the fluorescence of coralyne. We use the quenching property of halides to selectively quench the fluorescence of unbound coralyne but not that of coralyne bound to c-di-AMP. Using this simple selective quenching strategy, the assay could be used to monitor the synthesis of c-di-AMP by DisA or the degradation of c-di-AMP by YybT. Apart from the practical utility of this assay for c-di-AMP research, this work also demonstrates that, when administered to cells, intercalators might not only associate with polynucleotides, such as DNA or RNA, but also could associate with cyclic dinucleotides to disrupt or modulate signal transduction processes mediated by these nucleotides. PMID:24494631

Zhou, Jie; Sayre, David A; Zheng, Yue; Szmacinski, Henryk; Sintim, Herman O

2014-03-01

80

Continuous wave-based multiphoton excitation fluorescence for capillary electrophoresis  

Microsoft Academic Search

It was reported that a novel detection method, continuous wave (CW)-based multiphoton excitation (MPE) fluorescence detection with diode laser (DL), has been firstly proposed for capillary electrophoresis (CE). Special design of end-column detection configuration proved to be superior to on-column type, considering the detection sensitivity. Three different kinds of fluorescent tags that were widely used as molecular label in bio-analysis,

Sheng Chen; Bi-Feng Liu; Ling Fu; Tao Xiong; Tiancai Liu; Zhihong Zhang; Zhen-Li Huang; Qiang Lu; Yuan-Di Zhao; Qingming Luo

2006-01-01

81

Fluorescence Characteristics of Some Dehydroabietic Acid-Based Arylamines  

Microsoft Academic Search

Absorption spectra and fluorescence data in nonpolar solvents are reported for seven novel dehydroabietic acid-based diarylamines,\\u000a which have potential as components of hole transport layers for molecular electronic devices. This bulky group has been found\\u000a to improve the possibilities for film formation of these compounds, and in this study we show that this does not significantly\\u000a affect their fluorescence characteristics,

H. D. Burrows; N. Chattopadhyay; M. A. Esteves; M. Fernandes; B. Gigante

2007-01-01

82

Aliphatic amine responsive organogel system based on a simple naphthalimide derivative.  

PubMed

A new gelator based on a simple naphthalimide derivative was synthesized and fully characterized. It was found that the organogel was formed only in a mixed solvent of methanol and H2O (1/1, v/v). The organogel was thoroughly characterized by using various microscopic techniques including field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and UV-vis, fluorescence and Fourier transform infrared (FTIR) spectroscopy. Hydrogen bonds were the main driving force for the organogel formation. Interestingly, the organogel exhibited the ability to distinguish aliphatic amines from aromatic amines. The gel state and fluorescence emission intensity were both changed after two minutes after the addition of aliphatic amines. This organogel system could be applied in the detection of aliphatic amine pollutants. PMID:25008147

Cao, Xinhua; Zhang, Tingting; Gao, Aiping; Li, Keli; Cheng, Qiuli; Song, Lijuan; Zhang, Min

2014-07-30

83

A simple fluorescence quenching method for berberine determination using water-soluble CdTe quantum dots as probes  

NASA Astrophysics Data System (ADS)

A novel method for the determination of berberine has been developed based on quenching of the fluorescence of thioglycolic acid-capped CdTe quantum dots (TGA-CdTe QDs) by berberine in aqueous solutions. Under optimum conditions, the relative fluorescence intensity was linearly proportional to the concentration of berberine between 2.5 × 10 -8 and 8.0 × 10 -6 mol L -1 with a detection limit of 6.0 × 10 -9 mol L -1. The method has been applied to the determination of berberine in real samples, and satisfactory results were obtained. The mechanism of the proposed reaction was also discussed.

Cao, Ming; Liu, Meigui; Cao, Chun; Xia, Yunsheng; Bao, Linjun; Jin, Yingqiong; Yang, Song; Zhu, Changqing

2010-03-01

84

Radioiodine detector based on laser induced fluorescence  

DOEpatents

The invention involves the measurement of the concentration of the radioisotope .sup.129 I.sub.2 in the presence of a gas. The invention uses a laser to excite a sample of the .sup.129 I.sub.2 in a sample gas chamber and a reference sample of a known concentration of .sup.129 I.sub.2 in a reference gas chamber. The .sup.129 I.sub.2 in the sample and reference gas chamber each gives off fluorescence emissions which are received by photomultipliers which provide signals to a detector. The detector uses a ratioing technique to determine the concentration of .sup.129 I.sub.2 in the sample gas chamber.

McDonald, Jimmie R. (Upper Marlboro, MD) [Upper Marlboro, MD; Baronavski, Andrew P. (Alexandria, VA) [Alexandria, VA

1980-01-01

85

A label-free amplified fluorescence DNA detection based on isothermal circular strand-displacement polymerization reaction and graphene oxide.  

PubMed

A label-free fluorescent DNA biosensor has been presented based on isothermal circular strand-displacement polymerization reaction (ICSDPR) combined with graphene oxide (GO) binding. The proposed method is simple and cost-effective with a low detection limit of 4 pM, which compares favorably with other GO-based homogenous DNA detection methods. PMID:23671905

Li, Zhen; Zhu, Wenping; Zhang, Jinwen; Jiang, Jianhui; Shen, Guoli; Yu, Ruqin

2013-07-01

86

Two simple designs for surface-plasmon-resonance-based sensing  

Microsoft Academic Search

Surface plasmon resonance spectroscopy is becoming an increasingly important technique in biotechnology and chemical sensing. We present two simple, low cost, high sensitivity devices. The first is laser based mechanical implementation of a Kretschmann setup. Angle sweep is realized in two stages: step motor is used for coarse angle setting, and continuous angle sweep is achieved with a mirror on

Andrea Kobe; Janez I. Mozina

1999-01-01

87

Wide field-of-view Talbot grid-based microscopy for multicolor fluorescence imaging  

PubMed Central

The capability to perform multicolor, wide field-of-view (FOV) fluorescence microscopy imaging is important in screening and pathology applications. We developed a microscopic slide-imaging system that can achieve multicolor, wide FOV, fluorescence imaging based on the Talbot effect. In this system, a light-spot grid generated by the Talbot effect illuminates the sample. By tilting the excitation beam, the Talbot-focused spot scans across the sample. The images are reconstructed by collecting the fluorescence emissions that correspond to each focused spot with a relay optics arrangement. The prototype system achieved an FOV of 12 × 10 mm2 at an acquisition time as fast as 23 s for one fluorescence channel. The resolution is fundamentally limited by spot size, with a demonstrated full-width at half-maximum spot diameter of 1.2 ?m. The prototype was used to image green fluorescent beads, double-stained human breast cancer SK-BR-3 cells, Giardia lamblia cysts, and the Cryptosporidium parvum oocysts. This imaging method is scalable and simple for implementation of high-speed wide FOV fluorescence microscopy.

Pang, Shuo; Han, Chao; Erath, Jessey; Rodriguez, Ana; Yang, Changhuei

2013-01-01

88

A simple and pH-independent and ultrasensitive fluorescent probe for the rapid detection of Hg2+.  

PubMed

Development of fluorescent probes for Hg(2+) has become a hot topic in modern chemical research due to its high toxicity. In this paper, we for the first time report the synthesis and application of a thioether spirocyclic rhodamine B derivative (TR) as an efficient fluorescent probe for Hg(2+). TR was synthesized using a simple procedure under mild condition. By employing a thioether spirocycle instead of classic spirolactam as recognition unit, our proposed probe TR is acidity-insensitive, and exhibits a pH-independent and ultrasensitive response to Hg(2+). The probe works well within a wide pH range from 3.5 to 11.5, and exhibits a 350-fold fluorescence enhancement upon 0.5 equiv of Hg(2+) triggered, with a detection limit of 2.5 nM estimated for Hg(2+). In virtue of the strong thiophilic characteristic of Hg(2+), the response of the probe to Hg(2+) is instantaneous and highly selective, which make it favorable for cellular Hg(2+) imaging applications. It has been preliminarily used for highly sensitive monitoring of Hg(2+) level in living cells with satisfying resolution, demonstrating its value of the practical applications in biological systems. PMID:24209348

Luo, Ai-Li; Gong, Yi-Jun; Yuan, Yuan; Zhang, Jing; Zhang, Cui-Cui; Zhang, Xiao-Bing; Tan, Weihong

2013-12-15

89

Selective Fluorescence Detection of Monosaccharides Using a Material Composite Formed between Graphene Oxide and Boronate-Based Receptors.  

PubMed

We have developed a novel class of simple materials for sensing monosaccharides by the functionalization of graphene oxide (GO) with boronate-based fluorescence probes (BA1 and BA2). The composite materials were characterized by atomic force microscopy, Raman spectroscopy, and UV-vis/fluorescence spectroscopy. The strong fluorescence of the BA probes is quenched in the presence of GO through fluorescence resonance energy transfer. The BA@GO composite sensors formed provide a useful platform for fluorogenic detection of monosaccharides based on the strong affinity between the boronic acid receptor and monosaccharides. The BA@GO composite sensor displayed a "turn-on" fluorescence response with a good linear relationship toward fructose over a range of other saccharides. PMID:24918717

Sun, Xiaolong; Zhu, Bin; Ji, Ding-Kun; Chen, Qibin; He, Xiao-Peng; Chen, Guo-Rong; James, Tony D

2014-07-01

90

Fluorescence immunoassay based on long time correlations of number fluctuations.  

PubMed Central

We report the development of a fluorescence-based immunoassay technique relying on the physical phenomena of random number fluctuations and diffusion, which we review. By determining the autocorrelation of the fluctuations in the fluorescent intensity, this methid is able to measure the amount of labeled antigen or antibody that is bound to micrometer-sized carrier particles in solution. The principal advantage of this technique is its insensitivity to small, fast-diffusing sources. It also discriminates against weakly fluorescent contaminants of size comparable to the carrier particles. We demonstrate these attributes by using two model systems: a human IgG assay and an idealized system consisting of polystyrene fluorescent spheres and rhodamine dye.

Nicoli, D F; Briggs, J; Elings, V B

1980-01-01

91

Motor Oil Classification Based on Time-Resolved Fluorescence  

PubMed Central

A time-resolved fluorescence (TRF) technique is presented for classifying motor oils. The system is constructed with a third harmonic Nd:YAG laser, a spectrometer, and an intensified charge coupled device (ICCD) camera. Steady-state and time-resolved fluorescence (TRF) measurements are reported for several motor oils. It is found that steady-state fluorescence is insufficient to distinguish the motor oil samples. Then contour diagrams of TRF intensities (CDTRFIs) are acquired to serve as unique fingerprints to identify motor oils by using the distinct TRF of motor oils. CDTRFIs are preferable to steady-state fluorescence spectra for classifying different motor oils, making CDTRFIs a particularly choice for the development of fluorescence-based methods for the discrimination and characterization of motor oils. The two-dimensional fluorescence contour diagrams contain more information, not only the changing shapes of the LIF spectra but also the relative intensity. The results indicate that motor oils can be differentiated based on the new proposed method, which provides reliable methods for analyzing and classifying motor oils.

Mu, Taotao; Chen, Siying; Zhang, Yinchao; Guo, Pan; Chen, He; Meng, Fandong

2014-01-01

92

Fluorescence-based temperature control for polymerase chain reaction.  

PubMed

The ability to accurately monitor solution temperature is important for the polymerase chain reaction (PCR). Robust amplification during PCR is contingent on the solution reaching denaturation and annealing temperatures. By correlating temperature to the fluorescence of a passive dye, noninvasive monitoring of solution temperatures is possible. The temperature sensitivity of 22 fluorescent dyes was assessed. Emission spectra were monitored and the change in fluorescence between 45 and 95°C was quantified. Seven dyes decreased in intensity as the temperature increased, and 15 were variable depending on the excitation wavelength. Sulforhodamine B (monosodium salt) exhibited a fold change in fluorescence of 2.85. Faster PCR minimizes cycling times and improves turnaround time, throughput, and specificity. If temperature measurements are accurate, no holding period is required even at rapid speeds. A custom instrument using fluorescence-based temperature monitoring with dynamic feedback control for temperature cycling amplified a fragment surrounding rs917118 from genomic DNA in 3min and 45s using 35 cycles, allowing subsequent genotyping by high-resolution melting analysis. Gold-standard thermocouple readings and fluorescence-based temperature differences were 0.29±0.17 and 0.96±0.26°C at annealing and denaturation, respectively. This new method for temperature cycling may allow faster speeds for PCR than currently considered possible. PMID:24291705

Sanford, Lindsay N; Wittwer, Carl T

2014-03-01

93

mb-FLIM: model-based fluorescence lifetime imaging  

NASA Astrophysics Data System (ADS)

We have developed a model-based, parallel procedure to estimate fluorescence lifetimes. Multiple frequencies are present in the excitation signal. Modeling the entire fluorescence and measurement process produces an analytical ratio of polynomials in the lifetime variable ?. A non-linear model-fitting procedure is then used to estimate ?. We have analyzed this model-based approach by simulating a 10 ?M fluorescein solution (? = 4 ns) and all relevant noise sources. We have used real LED data to drive the simulation. Using 240 ?s of data, we estimate ? = 3.99 ns. Preliminary experiments on real fluorescent images taken from fluorescein solutions (measured ? = 4.1 ns), green plastic test slides (measured ? = 3.0 ns), and GFP in U2OS (osteosarcoma) cells (measured ? = 2.1 ns) demonstrate that this model-based measurement technique works.

Zhao, Qiaole; Young, Ian Ted; Schouten, Raymond; Stallinga, Sjoerd; Jalink, Kees; de Jong, Sander

2012-02-01

94

An adenovirus-based fluorescent reporter vector to identify and isolate HIV-infected cells.  

PubMed

A procedure is described that allows the simple identification and sorting of live human cells that transcribe actively the HIV virus, based on the detection of GFP fluorescence in cells. Using adenoviral vectors for gene transfer, an expression cassette including the HIV-1 LTR driving the reporter gene GFP was introduced into cells that expressed stably either the Tat transcriptional activator, or an inactive mutant of Tat. Both northern and fluorescence-activated cell sorting (FACS) analysis indicate that cells containing the functional Tat protein presented levels of GFP mRNA and GFP fluorescence several orders of magnitude higher than control cells. Correspondingly, cells infected with HIV-1 showed similar enhanced reporter gene activation. HIV-1-infected cells of the lymphocytic line Jurkat were easily identified by fluorescence-activated cell sorting (FACS) as they displayed a much higher green fluorescence after transduction with the reporter adenoviral vector. This procedure could also be applied on primary human cells as blood monocyte-derived macrophages exposed to the adenoviral LTR-GFP reporter presented a much higher fluorescence when infected with HIV-1 compared with HIV-uninfected cells. The vector described has the advantages of labelling cells independently of their proliferation status and that analysis can be carried on intact cells which can be isolated subsequently by fluorescence-activated cell sorting (FACS) for further culture. This work suggests that adenoviral vectors carrying a virus-specific transcriptional control element controlling the expressions of a fluorescent protein will be useful in the identification and isolation of cells transcribing actively the viral template, and to be of use for drug screening and susceptibility assays. PMID:11684299

Richman, Larry; Meylan, Pascal R A; Munoz, Miguel; Pinaud, Stéphane; Mirkovitch, Jovan

2002-01-01

95

A fluorescence-based assay for nanogram quantification of proteins using a protein binding ligand.  

PubMed

Fluorescence emission has been investigated in the context of estimation of proteins at nanogram levels. A Schiff base ligand with donor-acceptor substituents has been utilized as a fluorescent probe. The potency of this ligand is that it possesses the binding sites for both hydrophobic as well as hydrophilic groups in the proteins. The fluorescence emission of the probe was enhanced in the presence of nanogram levels of protein, which clearly signifies that even the least concentration of the protein is sufficient to perturb the environment around the probe. We demonstrate here that the fluorescence characteristic of the probe can be utilized to estimate even nanogram levels (66 ng-1 microgram mL(-1)) of protein. The major limitation of the currently available standard methods is the range of protein estimation, which terminates at microgram level and the interference due to the specificity of the amino acids, which vary from proteins to proteins. This fluorescence emission-based method is free from interference from any type of buffers, ionic strength of the medium and any specific amino acid residue and is a simple, rapid, single-step, sensitive method of estimation which can be applied to different classes of proteins. PMID:12520454

Shrivastava, H Yamini; Nair, Balachandran Unni

2003-01-01

96

Continuous wave-based multiphoton excitation fluorescence for capillary electrophoresis.  

PubMed

It was reported that a novel detection method, continuous wave (CW)-based multiphoton excitation (MPE) fluorescence detection with diode laser (DL), has been firstly proposed for capillary electrophoresis (CE). Special design of end-column detection configuration proved to be superior to on-column type, considering the detection sensitivity. Three different kinds of fluorescent tags that were widely used as molecular label in bio-analysis, such as small-molecule dye, fluorescent protein and nano particle or also referred to as quantum dot (QD), have been evaluated as samples for the constructed detection scheme. Quantitative analyses were also performed using rhodamine species as tests, which revealed dynamic linear range over two orders of magnitude, with detection limit down to zeptomole-level. Simultaneous detection of fluorescent dyestuffs with divergent excitation and emission wavelengths in a broad range showed advantage of this scheme over conventional laser-induced fluorescence (LIF) detection. Further investigations on CW-MPE fluorescence detection with diode laser for capillary zone electrophoresis (CZE) and micellar electrokinetic chromatography (MEKC) separations of fluorescein isothiocyanate (FITC) labeled amino acids indicated good prospect of this detection approach in various micro or nano-column liquid phase separation technologies. PMID:16325835

Chen, Sheng; Liu, Bi-Feng; Fu, Ling; Xiong, Tao; Liu, Tiancai; Zhang, Zhihong; Huang, Zhen-Li; Lu, Qiang; Zhao, Yuan-Di; Luo, Qingming

2006-03-24

97

Fluorescence lifetime-based glucose sensor using NADH  

NASA Astrophysics Data System (ADS)

Fluorescence lifetime-based glucose sensing does not depend on fluctuations of the intensity of the light source, light scattering, or changes in the transmission of optical components. Here we demonstrate the sensing of glucose based on the fluorescence lifetime properties of dihydro nicotinamide adenine dinucleotide (NADH), which is reduced from NAD in the presence of glucose and glucose dehydrogenase. In particular we use the difference in the fluorescence properties of free and protein-bound NADH and calculate an average fluorescence lifetime, which arises from the two short lifetimes ?1=0.28ns and ?2=0.60ns (representing free NADH) and the longer lifetime of ?3=2.9ns (for the protein-bound NADH). While initial results were derived from measurements in aqueous solution, we also demonstrate the suitability of this method for determining the concentration of glucose in blood using test strips. We find that the average fluorescence lifetime changes linearly by a factor of 0.17 per 100mg/dl change in glucose concentration. As an alternative the ratio between free and protein-bound components Rs/l may also be used for quantification. Rs/l increases by a factor of 0.74 per 100mg/dl change in glucose concentration.

von Ketteler, A.; Siegberg, D.; Herten, D. P.; Horn, C.; Petrich, W.

2012-02-01

98

Wireless implantable electronic platform for chronic fluorescent-based biosensors.  

PubMed

The development of a long-term wireless implantable biosensor based on fluorescence intensity measurement poses a number of technical challenges, ranging from biocompatibility to sensor stability over time. One of these challenges is the design of a power efficient and miniaturized electronics, enabling the biosensor to move from bench testing to long term validation, up to its final application in human beings. In this spirit, we present a wireless programmable electronic platform for implantable chronic monitoring of fluorescent-based autonomous biosensors. This system is able to achieve extremely low power operation with bidirectional telemetry, based on the IEEE802.15.4-2003 protocol, thus enabling over three-year battery lifetime and wireless networking of multiple sensors. During the performance of single fluorescent-based sensor measurements, the circuit drives a laser diode, for sensor excitation, and acquires the amplified signals from four different photodetectors. In vitro functionality was preliminarily tested for both glucose and calcium monitoring, simply by changing the analyte-binding protein of the biosensor. Electronics performance was assessed in terms of timing, power consumption, tissue exposure to electromagnetic fields, and in vivo wireless connectivity. The final goal of the presented platform is to be integrated in a complete system for blood glucose level monitoring that may be implanted for at least one year under the skin of diabetic patients. Results reported in this paper may be applied to a wide variety of biosensors based on fluorescence intensity measurement. PMID:21385666

Valdastri, Pietro; Susilo, Ekawahyu; Förster, Thilo; Strohhöfer, Christof; Menciassi, Arianna; Dario, Paolo

2011-06-01

99

A selective fluorescence probe for mercury ion based on the fluorescence quenching of terbium(III)-doped cadmium sulfide composite nanoparticles.  

PubMed

A fluorescent probe for mercury(II) ions, based on the quenching of fluorescence of terbium(III) ions doped in CdS nanoparticles, has been developed. The terbium(III)-doped cadmium sulfide composite nanoparticles were successfully synthesized through a straightforward one-pot process, with the biomolecule glutathione (GSH) as a capping ligand. In addition, the terbium(III) ions were observed an enhancement of emission intensity, owing to fluorescence energy transfer from the excited CdS particles to the emitting terbium(III). Because of a specific interaction, the fluorescence intensity of terbium(III)-doped CdS particles is obviously reduced in the presence of mercury(II) ions. The fluorescence quenching phenomenon of terbium(III) can be attributed to the fact that the energy transfer system was destroyed by combining with mercury(II). Under the optimal conditions, the fluorescent intensity of terbium(III) ions at 491nm decreased linearly with the concentration of mercury(II) ions ranging from 4.5nmolL(-1) to 550nmolL(-1). The limit of detection for mercury(II) was 0.1nmolL(-1). This method is simple, practical, relatively free of interference from coexisting substances and can be successfully applied to the determination of mercury(II) ions in real water samples. In addition, the probable mechanism of reaction between terbium(III)-doped CdS composite nanoparticles and mercury(II) was also discussed. PMID:20663708

Fu, Jie; Wang, Lun; Chen, Hongqi; Bo, Ling; Zhou, Cailing; Chen, Jingguo

2010-10-15

100

Algorithm for an implantable fluorescence based glucose sensor.  

PubMed

This article describes the algorithm for a continuous glucose monitor (CGM). The CGM system consists of an external reader and an insertable fluorescence based sensor. The sensor consists of a miniaturized optical sensor that incorporates a biocompatible macromolecular indicator that selectively binds glucose. It is designed to be subcutaneously inserted and allows for the direct measurement of interstitial fluid (ISF) glucose. PMID:23366679

Wang, Xiaolin; Mdingi, Colleen; DeHennis, Andrew; Colvin, Arthur E

2012-01-01

101

Wireless Implantable Electronic Platform for Chronic Fluorescent-Based Biosensors  

Microsoft Academic Search

The development of a long-term wireless implantable biosensor based on fluorescence intensity measurement poses a number of technical challenges, ranging from biocompatibility to sensor stability over time. One of these challenges is the design of a power efficient and miniaturized electronics, enabling the biosen- sor to move from bench testing to long term validation, up to its final application in

Pietro Valdastri; Ekawahyu Susilo; Thilo Forster; Christof Strohhofer; Arianna Menciassi; Paolo Dario

2011-01-01

102

Simple method of DNA stretching on glass substrate for fluorescence imaging and spectroscopy  

NASA Astrophysics Data System (ADS)

We demonstrate a simple method of stretching DNA to its full length, suitable for optical imaging and atomic force microscopy (AFM). Two competing forces on the DNA molecules, which are the electrostatic attraction between positively charged dye molecules (YOYO-1) intercalated into DNA and the negatively charged surface of glass substrate, and the centrifugal force of the rotating substrate, are mainly responsible for the effective stretching and the dispersion of single strands of DNA. The density of stretched DNA molecules could be controlled by the concentration of the dye-stained DNA solution. Stretching of single DNA molecules was confirmed by AFM imaging and the photoluminescence spectra of single DNA molecule stained with YOYO-1 were obtained, suggesting that our method is useful for spectroscopic analysis of DNA at the single molecule level.

Neupane, Guru P.; Dhakal, Krishna P.; Kim, Min Su; Lee, Hyunsoo; Guthold, Martin; Joseph, Vincent S.; Hong, Jong-Dal; Kim, Jeongyong

2014-01-01

103

Sapphire fiber thermometer based on fluorescence lifetime measurement  

NASA Astrophysics Data System (ADS)

A sapphire fiber thermometer probe with Cr3+ ion doped tip end was grown from the laser heated pedestal growth method. The fiber probe offers advantages of compact construct, high performance and ability to withstand high temperature. The temperature dependence of fluorescence of the probe was investigated, and a sapphire fiber thermometer based on its fluorescent decay was presented. Among the detection rang from the room temperature to 450 degrees C, the thermometer has an average temperature resolution of 1 degree C. The thermometer may be used in microwave treatment and thermal monitoring of Medium Voltage substations.

Ye, Linhua; Zhang, Yuefang; Zhao, Weizhong; Shen, Yonghang

2002-09-01

104

Magnetite nanoparticles for biosensor model based on bacteria fluorescence  

NASA Astrophysics Data System (ADS)

Fluorescence emission of pyoverdine - the siderophore synthesized by iron scavenger bacteria - was studied using in vitro cultures of Pseudomonas aeruginosa with the aim to design a biosensor system for liquid sample iron loading. Diluted suspensions of colloidal magnetite nanoparticles were supplied in the culture medium (10 microl/l and 100 microl/l) to simulate magnetic loading with iron oxides of either environmental waters or human body fluids. The electromagnetic exposure to radiofrequency waves of bacterial samples grown in the presence of magnetic nanoparticles was also carried out. Cell density diminution but fluorescence stimulation following 10 microl/l ferrofluid addition and simultaneous exposure to radiofrequency waves was evidenced. The inhibitory influence of 100 microl/l ferrofluid combined with RF exposure was evidenced by fluorescence data. Mathematical model was proposed to approach quantitatively the dynamics of cell density and fluorescence emission in relation with the consumption of magnetite nanoparticle supplied medium. The biosensor scheme was shaped based on the response to iron loading of bacterial sample fluorescence.

Poita, A.; Creanga, D.-E.; Airinei, A.; Tupu, P.; Goiceanu, C.; Avadanei, O.

2009-06-01

105

Polyacrylamide based ICG nanocarriers for enhanced fluorescence and photoacoustic imaging  

NASA Astrophysics Data System (ADS)

Indocyanine green (ICG) is an FDA approved tricarbocyanine dye. This dye, with a strong absorbance in the near infrared (NIR) region, has been extensively used for fluorescence and photoacoustic imaging in vivo. ICG in its free form, however, has a few drawbacks that limit its in vivo applications, such as non-targetability, tendency to form aggregates which changes its optical properties, fast degradation, short plasma lifetime and reduced fluorescence at body temperature. In order to bypass these inherent drawbacks, we demonstrate a polyacrylamide based nanocarrier that was particularly designed to carry the negatively charged ICG molecules. These nanocarriers are biodegradable, biocompatible and can be specifically targeted to any cell or tissue. Using these nanocarriers we avoid all the problems associated with free ICG, such as degradation, aggregation and short plasma lifetime, and also enhance demonstrate its ability towards photoacoustics and fluorescence imaging.

Ray, Aniruddha; Yoon, Hyung Ki; Ryu, HeeJu; Koo Lee, Yong-Eun; Kim, Gwangseong; Wang, Xueding; Kopelman, Raoul

2013-02-01

106

Performance validation of EMCCD and ICCD based near-infrared fluorescence imaging systems on a fluorescence solid phantom  

NASA Astrophysics Data System (ADS)

Near infrared (NIR) fluorescence imaging has been successfully applied for non-invasive assessment of both lymphatic architecture and function as well as potential disease markers of lymphatic dysfunction in clinical studies with intradermal injection of indocyanine green (ICG). For new "first-in-humans" NIR fluorescence imaging agents that need to be employed at far lower quantities, NIR fluorescence imaging devices with high measurement sensitivity are most favorable. However, the measurement sensitivity of NIR fluorescence imaging devices is limited by various parameters, including quantum efficiency of CCD chip, noise sources in the CCD camera, and the leakage of excitation light through optical filters. In this contribution, we present a quantum dot-based fluorescence solid phantom and its use for characterization of excitation light leakage and measurement sensitivity in both the intensified CCD (ICCD) and Electron Multiplying CCD (EMCCD) based NIR fluorescence imaging devices. The stability of the constructed quantum dot-based fluorescence solid phantom was first demonstrated and used to demonstrate higher measurement sensitivity compared of the ICCD as opposed to the EMCCD based NIR fluorescence imaging device when integration time were maintained less than 1.0 s. The phantom was used to assess the calculated transmission ratio, R, to minimize noise owing to excitation light leakage and show optimized filtering capabilities. The constructed quantum dot based solid phantom and the methodology for measuring parameters of transmission ratio and SNR can be used as a standard and quantifiable metric for installation and operational qualification of all NIR fluorescence imaging devices.

Zhu, Banghe; Sevick-Muraca, Eva M.

2012-02-01

107

Simple super-resolution live-cell imaging based on diffusion-assisted F?rster resonance energy transfer  

PubMed Central

Despite the recent development of several super-resolution fluorescence microscopic techniques, there are still few techniques that can be readily employed in conventional imaging systems. We present a very simple, rapid, general and cost-efficient super-resolution imaging method, which can be directly employed in a simple fluorescent imaging system with general fluorophores. Based on diffusion-assisted Förster resonance energy transfer (FRET), fluorescent donor molecules that label specific target structures can be stochastically quenched by diffusing acceptor molecules, thereby temporally separating otherwise spatially overlapped fluorescence signals and allowing super-resolution imaging. The proposed method provides two- to three-fold-enhancement in spatial resolution, a significant optical sectioning property, and favorable temporal resolution in live-cell imaging. We demonstrate super-resolution live-cell dynamic imaging using general fluorophores in a standard epi-fluorescence microscope with light-emitting diode (LED) illumination. Due to the simplicity of this approach, we expect that the proposed method will prove an attractive option for super-resolution imaging.

Cho, Sangyeon; Jang, Jaeduck; Song, Chaeyeon; Lee, Heeyoung; Ganesan, Prabhakar; Yoon, Tae-Young; Kim, Mahn Won; Choi, Myung Chul; Ihee, Hyotcherl; Heo, Won Do; Park, YongKeun

2013-01-01

108

Simple method of DNA stretching on glass substrate for fluorescence image and spectroscopy  

NASA Astrophysics Data System (ADS)

Study of biological molecule DNA has contributed to developing many breaking thoughts and wide applications in multidisciplinary fields, such as genomic, medical, sensing and forensic fields. Stretching of DNA molecules is an important supportive tool for AFM or spectroscopic studies of DNA in a single molecular level. In this article, we established a simple method of DNA stretching (to its full length) that occurred on a rotating negatively-charged surface of glass substrate. The isolation of a single DNA molecule was attained by the two competitive forces on DNA molecules, that is, the electrostatic attraction developed between the positively charged YOYO-1 stained DNA and the negatively charged substrate, and the centrifugal force of the rotating substrate, which separates the DNA aggregates into the single molecule. Density of stretched DNA molecules was controlled by selecting the specific parameters such as spinning time and rates, loading volume of DNA-dye complex solution etc. The atomic force microscopy image exhibited a single DNA molecule on the negatively-charged substrate in an isolated state. Further, the photoluminescence spectra of a single DNA molecule stained with YOYO-1 were achieved using the method developed in the present study, which is strongly believed to effectively support the spectroscopic analysis of DNA in a single molecular level.

Neupane, Guru P.; Dhakal, Krishna P.; Lee, Hyunsoo; Guthold, Martin; Joseph, Vincent S.; Hong, Jong-Dal; Kim, Jeongyong

2013-05-01

109

Rapid and simple detection of food poisoning bacteria by bead assay with a microfluidic chip-based system  

Microsoft Academic Search

A rapid bead assay for detecting pathogenic bacteria with a simple microfluidic chip-based system was developed. Five oligonucleotide probes corresponding to the 16S rRNA of the targeted bacteria were coupled covalently to fluorescent beads. Four species of bacteria (Escherichia coli, Salmonella enterica subsp. enterica serovar Enteritidis, Yersinia enterocolitica, and Bacillus cereus) were used as representative food-borne pathogenic bacteria. The RNAs

Masafumi Ikeda; Nobuyasu Yamaguchi; Katsuji Tani; Masao Nasu

2006-01-01

110

Fluorescence sensing of adenosine deaminase based on adenosine induced self-assembly of aptamer structures.  

PubMed

A new approach is proposed for simple detection of adenosine deaminase (ADA) based on adenosine induced self-assembly of two pieces of single-stranded DNA (ssDNA). These ssDNA are two fragments of the aptamer that has a strong affinity for adenosine and are labeled with carboxyfluorescein and black hole quencher-1, respectively. The complementarities of the bases in the two pieces of ssDNA are insufficient to form a stable structure. In the presence of adenosine, however, the ssDNA can be assembled into the intact aptamer tertiary structure, which results in fluorescence quenching of the carboxyfluorescein-labeled aptamer fragment. As a result, the adenosine-ssDNA complex shows a low background signal, which is rather desired for achieving sensitive detection. Reaction of the complex with ADA causes a great fluorescence enhancement by converting adenosine into inosine that has no affinity for the aptamer. This behaviour leads to the development of a simple and sensitive fluorescent method for assaying ADA activity, with a detection limit of 0.05 U mL(-1), which is more sensitive than most of the existing approaches. Furthermore, the applicability of the method has been demonstrated by detecting ADA in mouse serum samples. PMID:23462984

Feng, Tingting; Ma, Huimin

2013-04-21

111

Rapid human metapneumovirus microneutralization assay based on green fluorescent protein expression.  

PubMed

We describe a simple and expedited microneutralization assay for human metapneumovirus virus (HMPV) based on a recombinant HMPV expressing the enhanced green fluorescent protein (rHMPV-GFP). Test serum dilutions were incubated with fixed amounts of rHMPV-GFP and inoculated onto Vero cells, and the growth of non-neutralized rHMPV-GFP was visualized by fluorescent microscopy of living cells. A preliminary titer could be determined following 3 days of incubation. GFP expression was sufficient to be read by an automated scanner after 4-5 days of incubation, which also provided a permanent record. In comparison, the conventional serum neutralization assay requires a longer incubation time plus the additional steps of fixation and staining or immunostaining. rHMPV-GFP-based titers could be determined by the 50% infectivity endpoint method of Reed and Muench [Reed, L.J., Muench, H., 1938. A simple method of estimating fifty per cent endpoint. Am. J. Hyg. 27, 493-497], or by automated scanning and non-linear regression to determine the 50% endpoint of GFP fluorescence. The latter method was two- to three-fold more sensitive. This assay also permits automation and up-scaling, making it suitable for broad HMPV seroepidemiology studies and experiments that require large scale serology, such as vaccine studies. PMID:15955576

Biacchesi, Stéphane; Skiadopoulos, Mario H; Yang, Lijuan; Murphy, Brian R; Collins, Peter L; Buchholz, Ursula J

2005-09-01

112

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

PubMed Central

An approach for colorimetric and fluorescent sensing of thiocyanate (SCN-) has been proposed based on the competitive-displacement strategy between meso-tetraphenylporphyrin (TPP) and meso-tetraphenylporphyrin cobalt(II) (CoTPP). In THF-water solution, TPP emits strong fluorescence at 651 nm; however, the fluorescence was quenched stepwise by CoTPP, and then restored by SCN-, the detection limit is 6.0 × 10-4 M. The recognition of SCN- could also be easily achieved by visual way since the assembly system showed significant color change by the anion. Both the fluorescence and the color change of the system exhibits remarkably high selectivity to SCN- over a large series of anions. The interaction mechanisms among TPP, CoTPP and SCN- were primarily investigated by fluorescence lifetime. The quenching of TPP fluorescence is attributed to the formation of TPP/CoTPP aggregates, and the fluorescence restoration is due to the binding of CoTPP with SCN-, releasing the free TPP. This simple system has the potential to be used as a latent fluorescent sensing approach for SCN- for environmental analysis.

Zhang, Ying; Wang, Hua; Yang, Rong H.

2007-01-01

113

Synthesis and fluorescence characteristics of ATP-based FRET probes.  

PubMed

Adenosine triphosphate (ATP) analogues labelled with two dyes suitable for undergoing Förster Resonance Energy Transfer (FRET) have the potential to be valuable tools to continuously study the enzymatic activity of ATP consuming enzymes. Here, we present a synthesis strategy that allows obtaining these ATP analogues in a straight-forward manner. Earlier studies indicate that modifying ATP at the O2'- and the ?-position is a very promising starting point for the design of these probes. We synthesized probes modified with five different combinations of dyes attached to these positions and investigated their fluorescence characteristics in the non-cleaved state as well as after enzymatic hydrolysis. All presented probes largely change their fluorescence characteristics upon cleavage. They include ratiometric FRET probes as well as dark quenched analogues. For typical in vitro applications a combination of the sulfonated polymethine dyes Sulfo-Cy3 and Sulfo-Cy5 seems to be most promising due to their excellent solubility in aqueous buffer and a large change of fluorescence characteristics upon cleavage. For this combination of dyes we also synthesized analogues modified at the ?- and the C2- or the O3'-position, respectively, as these attachment sites are also well accepted by certain ATP consuming enzymes. These analogues show comparably large changes in fluorescence characteristics. Overall, we present new ATP-based FRET probes that have the potential to enable monitoring the enzymatic activity of ATP consuming enzymes. PMID:24173528

Hardt, Norman; Hacker, Stephan M; Marx, Andreas

2013-12-28

114

Dextran-based fluorescent nanoprobes for sentinel lymph node mapping.  

PubMed

Biopsy of sentinel lymph node (SLN) has become a common practice to predict whether tumor metastasis has occurred, so proper SLN positioning tracers are highly required. Due to many drawbacks of SLN tracers currently used, developing ideal, biosafe SLN imaging agents is always an urgent issue. The current study designed a novel fluorescent nanoprobe for accurate SLN mapping. Dextran-based nanogel (DNG) was prepared through a highly efficient self-assembly assisted approach and serves as a multi-functional platform for conjugating wide spectra emitting fluorescent agents. The newly fabricated fluorescent DNG (FDNG) could be designed with optimum size and stable fluorescent intensity for specific SLN imaging. Furthermore, a long-term dynamic course in vivo (from 1 min to 72 h) revealed the satisfactory specificity, sensitivity, and stability for SLN mapping. Most importantly, both in vitro and in vivo evaluations indicated that FDNG had fine biosafety and biocompatibility with lymphatic endothelial cells. All these results supported that FDNG could be used as highly efficient molecular imaging probes for specific, sensitive, stable, non-invasive, and safe SLN mapping, which provides efficient and accurate location for SLN biopsy and thus predicts tumor metastasis as well as directs therapies. Besides, our recent studies further demonstrated that DNG could also serve as a specific and controllable drug carrier, indicating a potential application for specific therapies of various lymph-associated diseases. PMID:24957293

Dai, Tingting; Zhou, Shuyan; Yin, Chuyang; Li, Shengli; Cao, Weigang; Liu, Wei; Sun, Kang; Dou, Hongjing; Cao, Yilin; Zhou, Guangdong

2014-09-01

115

Immunosensor systems with the Langmuir-film-based fluorescence detection  

SciTech Connect

A method is developed for detecting protein antigens for fluorescent immunoassay using a model system based on the technique for preparation of Langmuir films. Fluorescein isothiocyanate and donor-acceptor energy-transfer pairs of markers (the Yb complex of tetraphenyl porphyrin - benzoyl trifluoroacetoneisothiocyanate and derivatives of tetra(carboxyphenyl) porphyrin - cyanine dye containing a five-membered polyene chain), which were nor studied earlier, were used as markers for detecting the binding of an antigen on the surface of Langmuir films of antibodies. Fluorescence was detected in the near-IR region (for the first pair) and in the visible spectral range (for the second pair). To reduce the nonspecific sorption of a protein (antigen), a method was proposed for the preparation of a nonpolar surface by applying an even number of layers of stearic acid as a substrate for the Langmuir - Blodgett film. A high sensitivity of model systems to a protein antigen in solution was achieved ({approx}10{sup -11} M), the assay time being 6 - 8 min. The model system with the first donor - acceptor pair was tested in analysis of the blood plasma. The fluorescence of the Dy{sup 3+}, Tm{sup 3+}, and Yb{sup 3+} complexes of tetraphenyl porphyrin sensitised by diketonate complexes of lanthanides was studied for the first time and the enhancement of the IR fluorescence of these complexes in a Langmuir film was demonstrated. (papers devoted to the memory of academician a m prokhorov)

Chudinova, G K; Nagovitsyn, I A; Savranskii, V V [Natural Science Center, A.M. Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Karpov, R E [Photochemistry Center, Russian Academy of Sciences, Moscow (Russian Federation)

2003-09-30

116

Fluorescence molecular tomography with optimal radon transform based surface reconstruction.  

PubMed

Full angle non-contact fluorescence molecular tomography allows acquiring large data sets from complete angles, and simplifies the experimental setups. Accurately extracting animal surface is important for this kind of imaging systems. However, in in-vivo experiments, mouse breath movements and mechanical errors will influence the surface reconstruction. An optimal radon transform based surface reconstruction method is proposed to handle these two factors. The proposed method uses a line searching method to minimize the mismatch between the reconstructed 3D surface and the projected silhouettes at different angles. Therefore, the proposed method generates the optimal 3D surface compared to other methods based on radon transform. Results show that the mean mismatch of 3D surface generated is less than two CCD pixels (0.154 mm) in in-vivo experiments. In-vivo fluorescence molecular tomography is also performed to demonstrate the efficiency of the proposed method. PMID:19964524

Liu, Xin; Wang, Daifa; Bai, Jing

2009-01-01

117

Simple, Scalable, Script-Based Science Processor (S4P)  

NASA Technical Reports Server (NTRS)

The development and deployment of data processing systems to process Earth Observing System (EOS) data has proven to be costly and prone to technical and schedule risk. Integration of science algorithms into a robust operational system has been difficult. The core processing system, based on commercial tools, has demonstrated limitations at the rates needed to produce the several terabytes per day for EOS, primarily due to job management overhead. This has motivated an evolution in the EOS Data Information System toward a more distributed one incorporating Science Investigator-led Processing Systems (SIPS). As part of this evolution, the Goddard Earth Sciences Distributed Active Archive Center (GES DAAC) has developed a simplified processing system to accommodate the increased load expected with the advent of reprocessing and launch of a second satellite. This system, the Simple, Scalable, Script-based Science Processor (S42) may also serve as a resource for future SIPS. The current EOSDIS Core System was designed to be general, resulting in a large, complex mix of commercial and custom software. In contrast, many simpler systems, such as the EROS Data Center AVHRR IKM system, rely on a simple directory structure to drive processing, with directories representing different stages of production. The system passes input data to a directory, and the output data is placed in a "downstream" directory. The GES DAAC's Simple Scalable Script-based Science Processing System is based on the latter concept, but with modifications to allow varied science algorithms and improve portability. It uses a factory assembly-line paradigm: when work orders arrive at a station, an executable is run, and output work orders are sent to downstream stations. The stations are implemented as UNIX directories, while work orders are simple ASCII files. The core S4P infrastructure consists of a Perl program called stationmaster, which detects newly arrived work orders and forks a job to run the appropriate executable (registered in a configuration file for that station). Although S4P is written in Perl, the executables associated with a station can be any program that can be run from the command line, i.e., non-interactively. An S4P instance is typically monitored using a simple Graphical User Interface. However, the reliance of S4P on UNIX files and directories also allows visibility into the state of stations and jobs using standard operating system commands, permitting remote monitor/control over low-bandwidth connections. S4P is being used as the foundation for several small- to medium-size systems for data mining, on-demand subsetting, processing of direct broadcast Moderate Resolution Imaging Spectroradiometer (MODIS) data, and Quick-Response MODIS processing. It has also been used to implement a large-scale system to process MODIS Level 1 and Level 2 Standard Products, which will ultimately process close to 2 TB/day.

Lynnes, Christopher; Vollmer, Bruce; Berrick, Stephen; Mack, Robert; Pham, Long; Zhou, Bryan; Wharton, Stephen W. (Technical Monitor)

2001-01-01

118

A reliable and sensitive bead-based fluorescence assay for identification of nucleic acid sequences  

NASA Astrophysics Data System (ADS)

The sensitive and rapid detection of pathogenic DNA is of tremendous importance in the field of diagnostics. We demonstrate the ability of detecting and quantifying single- and double-stranded pathogenic DNA with picomolar sensitivity in a bead-based fluorescence assay. Selecting appropriate capturing and detection sequences enables rapid (2 h) and reliable DNA quantification. We show that synthetic sequences of S. pneumoniae and M. luteus can be quantified in very small sample volumes (20 ?L) across a linear detection range over four orders of magnitude from 1 nM to 1 pM, using a miniaturized wide-field fluorescence microscope without amplification steps. The method offers single molecule detection sensitivity without using complex setups and thus volunteers as simple, robust, and reliable method for the sensitive detection of DNA and RNA sequences.

Klamp, Tobias; Yahiatène, Idir; Lampe, André; Schüttpelz, Mark; Sauer, Markus

2011-02-01

119

Fluorescence-based biosensing of zinc using carbonic anhydrase  

Microsoft Academic Search

Measurement of free zinc levels and imaging of zinc fluxes remains technically difficult due to low levels and the presence of interfering cations such as Mg and Ca. We have developed a series of fluorescent zinc indicators based on the superb sensitivity and selectivity of a protein, human apo-carbonic anhydrase II, for Zn(II). These indicators transduce the level of free zinc

Carol A. Fierke; Richard B. Thompson

2001-01-01

120

Development of fluorescence-based LIDAR technology for biological sensing  

Microsoft Academic Search

Results of our on-going development of biological warfare agents (BWA) detection systems based on spectral detection of ultraviolet (UV) laser induced fluorescence (LIF) are presented. A compact optical parametric oscillator (OPO) with intracavity sum-frequency mixing (SFM) to generate 293 nm UV laser irradiation was developed. The OPO\\/SFM device was pumped by a diode-pumped Nd:YAG laser (1064 nm), including subsequent second-harmonic

Per Jonsson; Fredrik Kullander; Mikael Tiihonen; Melker Nordstrand; Gøran Olofsson; Mikael Lindgren

121

Synthesis of Ethynylated Phenothiazine Based Fluorescent Boronic Acid Probes  

Microsoft Academic Search

Ethynylated phenothiazine based fluorescent boronic acid probes were prepared. Sonogashira coupling reaction was used to introduce\\u000a substituted phenylethynylene fragments to the phenothiazine fluorophore to extend the ?-conjugation and to enhance the emission\\u000a property. The photophysical properties and the binding properties of these probes with hydroxyl acids were investigated. We\\u000a found that the probes with significant ICT effect show emissions which

Yubo Wu; Huimin Guo; Jingyin Shao; Xin Zhang; Shaomin Ji; Jianzhang Zhao

2011-01-01

122

In situ building of a nanoprobe based on fluorescent carbon dots for methylmercury detection.  

PubMed

A new fluorescent assay based on in situ ultrasound-assisted synthesis of carbon dots (CDs) as optical nanoprobes for the detection of methylmercury has been developed. Application of high-intensity sonication allows simultaneous performance of the synthesis of fluorescent CDs within the analytical time scale and the selective recognition of the target analyte. Microvolume fluorospectrometry is applied for measurement of the fluorescence quenching caused by methylmercury. The assay uses low amounts of organic precursors (fructose, poly(ethylene glycol), and ethanol) and can be accomplished within 1 min. A detection limit of 5.9 nM methylmercury and a repeatability expressed as a relative standard deviation of 2.2% (N = 7) were obtained. CDs displayed a narrow size distribution with an average size of 2.5 nm as determined by electron transmission microscopy. To study the quenching mechanism, fluorescence, atomic absorption spectrometry, and Fourier transform infrared spectrometry were applied. Hydrophobicity of methylmercury and its ability to facilitate a nonradiative electron/hole recombination are suggested as the basis of the recognition event. A simple and green assay is achieved for quick detection of methylmercury without the use of tedious sample preparation procedures or complex and expensive instrumentation. PMID:24678836

Costas-Mora, Isabel; Romero, Vanesa; Lavilla, Isela; Bendicho, Carlos

2014-05-01

123

Nanoparticle-based energy transfer for rapid and simple detection of protein glycosylation  

SciTech Connect

Glycan moiety of glycoproteins plays an essential role in its biological activity in vivo, and the analysis of glycosylation is of great importance in the development of protein therapeutics. In this study, we report a rapid and simple detection of protein glycosylation based on the fluorescence resonance energy transfer (FRET) between concanavalin A-conjugated gold nanoparticles (ConA-AuNPs) and dextran-conjugated quantum dots (Dex-QDs). The increased photoluminescence (PL) signals of Dex-QDs due to the competitive inhibition of glycoproteins were well correlated with the glycosylation chain length of glucose oxidases as well as the mannosylation degree of bovine serum albumin (BSA). The parallel analysis of the diversely mannosylated BSAs using an image analyzer further demonstrated the potential of this new technique in high-throughput screening of glycoprotein and carbohydrate therapeutics.

Oh, Eunkeu; Lee, Dohoon; Kim, Young-Pil; Cha, Seung YOUP; Oh, Doo BEYONG; Kim, Jungbae; Kang, Hyun AH; Kim, Hak SUNG

2006-12-04

124

Identification of resilin in the leg of cockroach, Periplaneta americana: confirmation by a simple method using pH dependence of UV fluorescence  

Microsoft Academic Search

We have examined the tarsus (foot) and tibial segments of the cockroach leg to identify structures that contain the elastic protein resilin. The presence of resilin was tested using the conventional criteria of fluorescent emission at 420 nm under UV illumination and histological staining of wholemount tissues by toluidine blue. We have also developed a simple method of confirming identification of

David Neff; S. Faith Frazier; Laura Quimby; Ruu-Tong Wang; Sasha Zill

2000-01-01

125

Fluorescent switch for fast and selective detection of mercury (II) ions in vitro and in living cells and a simple device for its removal.  

PubMed

A water-soluble, biocompatible, and fluorescent chemosensor (1) for label-free, simple, and fast detection of mercury ions (Hg(2+)) in aqueous solutions and in HepG2 cells with high selectivity is reported herein. Chelation of 1 with Hg(2+) results in the disappearance of its fluorescence emission at 350nm and the appearance of a new emission at 405nm. Selectivity and interference studies indicated that 1 could be selectively chelated by Hg(2+) without interference from other metal ions. Insight into the mechanisms responsible for its fluorescence effect was gained from ultrafast transient absorption spectroscopy. With these properties, 1 was successfully applied for imaging Hg(2+) in living cells and for removing Hg(2+) from river water. Moreover, we also constructed a simple device for fast and effective removal of Hg(2+) from contaminated liquid samples. PMID:24840434

Yuan, Yue; Jiang, Shenlong; Miao, Qingqing; Zhang, Jia; Wang, Mengjing; An, Linna; Cao, Qinjingwen; Guan, Yafeng; Zhang, Qun; Liang, Gaolin

2014-07-01

126

Simple and Rapid Quality Control of Sulfated Glycans by a Fluorescence Sensor Assay--Exemplarily Developed for the Sulfated Polysaccharides from Red Algae Delesseria sanguinea  

PubMed Central

Sulfated polysaccharides (SP) from algae are of great interest due to their manifold biological activities. Obstacles to commercial (especially medical) application include considerable variability and complex chemical composition making the analysis and the quality control challenging. The aim of this study was to evaluate a simple microplate assay for screening the quality of SP. It is based on the fluorescence intensity (FI) increase of the sensor molecule Polymer-H by SP and was originally developed for direct quantification of SP. Exemplarily, 65 SP batches isolated from the red alga Delesseria sanguinea (D.s.-SP) and several other algae polysaccharides were investigated. Their FI increase in the Polymer-H assay was compared with other analytical parameters. By testing just one concentration of a D.s.-SP sample, quality deviations from the reference D.s.-SP and thus both batch-to-batch variability and stability can be detected. Further, structurally distinct SP showed to differ in their concentration-dependent FI profiles. By using corresponding reference compounds, the Polymer-H assay is therefore applicable as identification assay with high negative predictability. In conclusion, the Polymer-H assay showed to represent not only a simple method for quantification, but also for characterization identification and differentiation of SP of marine origin.

Luhn, Susanne; Grimm, Juliane C.; Alban, Susanne

2014-01-01

127

A simple parallel tandem organic solar cell based on metallophthalocyanines  

NASA Astrophysics Data System (ADS)

A simple parallel tandem solar cell based on a combination of Zn-phthalocyanine (Pc) and ClInPc has been fabricated and characterized. Compared to a traditional series tandem cell, parallel tandem cells eliminate the need for a semitransparent recombination layer, reducing the complexity of device fabrication while still providing an excellent increase in device performance. Results show a realized broadening of the spectral response and enhancement of the external quantum efficiency as a result of the complementary absorption profiles of ZnPc and ClInPc in the near infrared region. Introduction of a blended ClInPc:C60 layer is shown to more than double the power conversion efficiency of a standard ZnPc/C60 bilayer device (PCE=0.86%). The enhanced performance of the parallel tandem (PCE=1.81%) arises from an increase in both the open circuit voltage and the short circuit current.

Yuen, Avery P.; Hor, Ah-Mee; Preston, John S.; Klenkler, Richard; Bamsey, Nathan M.; Loutfy, Rafik O.

2011-04-01

128

Simple-Random-Sampling-Based Multiclass Text Classification Algorithm  

PubMed Central

Multiclass text classification (MTC) is a challenging issue and the corresponding MTC algorithms can be used in many applications. The space-time overhead of the algorithms must be concerned about the era of big data. Through the investigation of the token frequency distribution in a Chinese web document collection, this paper reexamines the power law and proposes a simple-random-sampling-based MTC (SRSMTC) algorithm. Supported by a token level memory to store labeled documents, the SRSMTC algorithm uses a text retrieval approach to solve text classification problems. The experimental results on the TanCorp data set show that SRSMTC algorithm can achieve the state-of-the-art performance at greatly reduced space-time requirements.

Liu, Wuying; Wang, Lin; Yi, Mianzhu

2014-01-01

129

Phthalocyanine dimerization-based molecular beacons using near-IR fluorescence  

PubMed Central

Herein we demonstrate the use of a novel dimerization-based molecular beacon (MB) probe consisting of two metallo-phthalocyanine (Pc) fluorophores that use near-IR fluorescence, appropriate for highly specific and sensitive in-vivo and/or in-vitro DNA/RNA detection. Pc’s possess a propensity to form non-fluorescent H-dimers that is utilized as the molecular “off” switch in the closed MB conformation. The “on” switch, which is generated when the solution target binds to the loop of the MB forming the open form, also provides two fluorophores for transduction resulting in a doubling of the extinction coefficient and improving the resulting fluorescence yield compared to a classical single-fluorophore/quencher MB system. In addition, the Pc-based MBs possess high thermal, photo and chemical stabilities that are essential for many highly sensitive applications, such as molecular imaging. The dimer-based MBs were obtained using a simple single-step synthesis procedure and demonstrated excellent quenching efficiencies (98%) as well as a high signal-to-background ratio (~60) exceeding the performance characteristics of many conventionally-available MB probes.

Nesterova, Irina V.; Erdem, S. Sibel; Pakhomov, Serhii; Hammer, Robert P.; Soper, Steven A.

2009-01-01

130

A colorimetric and turn-on fluorescent chemosensor for Al(III) based on a chromone Schiff-base.  

PubMed

A simple Schiff-base receptor 7-methoxychromone-3-carbaldehyde-(pyridylformyl) hydrazone (MCNH) was prepared. It exhibits an "off-on-type" mode with high sensitivity in the presence of Al(3+). This compound could be used as Al(3+) probe in ethanol and it features visible light excitation (433 nm) and emission (503 nm) profiles. Upon binding of Al(3+), a significant fluorescence enhancement with a turn-on ratio over 800-fold was triggered. However, other metal ions had no such significant effect on the fluorescence. MCNH can also be used as a colorimetric chemosensor for Al(3+), which is easily observed from colorless to yellow-green by the naked-eye. The detection limit of MCNH for Al(3+) was as low as 1.9×10(-7) M. PMID:24140792

Fan, Long; Li, Tian-rong; Wang, Bao-dui; Yang, Zheng-yin; Liu, Chun-jiao

2014-01-24

131

Fluorescence resonance energy transfer from sulfonated graphene to riboflavin: a simple way to detect vitamin B2.  

PubMed

We have prepared sulfonated graphene (SG) by diazonium coupling technique and it has been characterized by UV-vis absorption spectroscopy, Raman spectroscopy, electron microscopy, energy-dispersive spectroscopy (EDS), EDS elemental mapping, X-ray photoelectron spectroscopy (XPS), and FTIR spectroscopy. The photoluminescence (PL) property of SG at different pH (pH 4, 7, and 9.2) has been investigated and SG shows highest PL-intensity and quantum yield at pH 4 compared to those at higher pH and that of GO at pH 4. Due to the strong overlap between the emission spectrum of SG and absorption spectrum of riboflavin (RF, vitamin B2) at pH 4, it has been tactfully used as donor for the fluorescence resonance energy transfer (FRET) process. However, graphene oxide (GO) does not exhibit any FRET with RF at an identical condition due to its much lower quantum yield. We have demonstrated a selective detection of vitamin B2 in presence of nucleic acid (DNA, RNA), protein (BSA), amino acid (Lysine) and other water-soluble vitamins (Becosules, Zevit capsules) based on the spontaneous FRET from PL-active SG (donor) to RF (acceptor). The calibration curve indicates excellent affirmation to detect vitamin B2 using FRET and it is superior to the ordinary fluorescence method of detecting RF in presence of different biomolecules. PMID:23838272

Kundu, Aniruddha; Nandi, Sudipta; Layek, Rama K; Nandi, Arun K

2013-08-14

132

Data storage based on photochromic and photoconvertible fluorescent proteins.  

PubMed

The recent discovery of photoconvertible and photoswitchable fluorescent proteins (PCFPs and RSFPs, respectively) that can undergo photoinduced changes of their absorption/emission spectra opened new research possibilities in subdiffraction microscopy and optical data storage. Here we demonstrate the proof-of-principle for read only and rewritable data storage both in 2D and 3D, using PCFPs and RSFPs. The irreversible burning of information was achieved by photoconverting from green to red defined areas in a layer of the PCFP Kaede. Data were also written and erased several times in layers of the photochromic fluorescent protein Dronpa. Using IrisFP, which combines the properties of PCFPs and RSFPs, we performed the first encoding of data in four colours using only one type of fluorescent protein. Finally, three-dimensional optical data storage was demonstrated using three mutants of EosFP (d1EosFP, mEosFP and IrisFP) in their crystalline form. Two-photon excitation allowed the precise addressing of regions of interest (ROIs) within the three-dimensional crystalline matrix without excitation of out-of-focus optical planes. Hence, this contribution highlights several data storage schemes based on the remarkable properties of PCFPs/RSFPs. PMID:20416344

Adam, Virgile; Mizuno, Hideaki; Grichine, Alexei; Hotta, Jun-ichi; Yamagata, Yutaka; Moeyaert, Benjamien; Nienhaus, G Ulrich; Miyawaki, Atsushi; Bourgeois, Dominique; Hofkens, Johan

2010-09-15

133

A Simple, Scalable, Script-based Science Processor  

NASA Technical Reports Server (NTRS)

The production of Earth Science data from orbiting spacecraft is an activity that takes place 24 hours a day, 7 days a week. At the Goddard Earth Sciences Distributed Active Archive Center (GES DAAC), this results in as many as 16,000 program executions each day, far too many to be run by human operators. In fact, when the Moderate Resolution Imaging Spectroradiometer (MODIS) was launched aboard the Terra spacecraft in 1999, the automated commercial system for running science processing was able to manage no more than 4,000 executions per day. Consequently, the GES DAAC developed a lightweight system based on the popular Per1 scripting language, named the Simple, Scalable, Script-based Science Processor (S4P). S4P automates science processing, allowing operators to focus on the rare problems occurring from anomalies in data or algorithms. S4P has been reused in several systems ranging from routine processing of MODIS data to data mining and is publicly available from NASA.

Lynnes, Christopher

2004-01-01

134

Photon upconversion in homogeneous fluorescence-based bioanalytical assays.  

PubMed

Upconverting phosphors (UCPs) are very attractive reporters for fluorescence resonance energy transfer (FRET)-based bioanalytical assays. The large anti-Stokes shift and capability to convert near-infrared to visible light via sequential absorption of multiple photons enable complete elimination of autofluorescence, which commonly impairs the performance of fluorescence-based assays. UCPs are ideal donors for FRET, because their very narrow-banded emission allows measurement of the sensitized acceptor emission, in principle, without any crosstalk from the donor emission at a wavelength just tens of nanometers from the emission peak of the donor. In addition, acceptor dyes emitting at visible wavelengths are essentially not excited by near-infrared, which further emphasizes the unique potential of upconversion FRET (UC-FRET). These characteristics result in favorable assay performance using detection instrumentation based on epifluorometer configuration and laser diode excitation. Although UC-FRET is a recently emerged technology, it has already been applied in both immunoassays and nucleic acid hybridization assays. The technology is also compatible with optically difficult biological samples, such as whole blood. Significant advances in assay performance are expected using upconverting lanthanide-doped nanocrystals, which are currently under extensive research. UC-FRET, similarly to other fluorescence techniques based on resonance energy transfer, is strongly distance dependent and may have limited applicability, for example in sandwich-type assays for large biomolecules, such as viruses. In this article, we summarize the essentials of UC-FRET, describe its current applications, and outline the expectations for its future potential. PMID:18596348

Soukka, Tero; Rantanen, Terhi; Kuningas, Katri

2008-01-01

135

Fluorescent properties of DNA base analogue tC upon incorporation into DNA -- negligible influence of neighbouring bases on fluorescence quantum yield  

Microsoft Academic Search

The quantum yield of the fluorescent tricyclic cyto- sine analogue, 1,3-diaza-2-oxophenothiazine, tC, is high and virtually unaffected by incorporation into both single- and double-stranded DNA irrespective of neighbouring bases (0.17-0.24 and 0.16-0.21, respectively) and the corresponding fluorescence decay curves are all mono-exponential, properties that are unmatched by any base analogue so far. The fluorescence lifetimes increase when going from tC

Peter Sandin; L. Marcus Wilhelmsson; Per Lincoln; Vicki E. C. Powers; Tom Brown; Bo Albinsson

2005-01-01

136

A ratiometric fluorescent probe for sensitive, selective and reversible detection of copper (II) based on riboflavin-stabilized gold nanoclusters.  

PubMed

Most of the copper (II) fluorescent probes are based on the measurement of fluorescence at a single wavelength, which may be influenced by variations in the sample environment. To the end, the ratiometric fluorescent measurement, which involves the simultaneous measurement of two fluorescence signals at different wavelengths followed by calculation of their intensity ratio, can effectively eliminate the adverse effects on fluorescence signals and give greater precision to the data analysis relative to single-channel detection. In this work, we prepared novel luminescent gold nanoclusters (AuNCs) utilizing vitamin B2 (riboflavin) as stabilizer by a simple, rapid and one-pot green (low-toxicity materials use) procedure. The as-prepared riboflavin-AuNCs (Ri-AuNCs) solution can be luminescent exhibiting two fluorescence emission peaks at 530 nm and around 840 nm with excitation at 375 nm, however, in the presence of Cu(2+), the fluorescence of the Ri-AuNCs was found to be quenched at around 840 nm and enhanced at 530 nm by Cu(2+). The resultant ratiometric fluorescent response can provide a novel sensory probe for the determination of Cu(2+). The present probe had excellent selectivity in the presence of several cations. The probe revealed a detection limit of 0.9 ?M of Cu(2+). Moreover, our proposed probe can reversibly switch between the "on" and "off" states through the addition of Cu(2+) and EDTA, which is reusable in practical application. Results and method reported here provide a unique strategy for performance of ratiometric assays demonstrated with a AuNCs-based fluorescent probe, which expands the application of AuNCs. PMID:24209359

Zhang, Min; Le, Huynh-Nhu; Jiang, Xiao-Qin; Guo, Su-Miao; Yu, Hai-Jun; Ye, Bang-Ce

2013-12-15

137

Effects of Mechanical Constraint on the Performance of Fluorescent Hydrogel-based Fiber Optic Sensors  

NASA Astrophysics Data System (ADS)

Although biosensor technology is a broad and well-studied field, the progress of many novel sensor technologies faces challenges. These challenges range from simple design considerations to fundamental issues with the concept or approach. One of the most active fields of sensor research integrates fiber optics with specially engineered fluorescent molecules. This type of sensor typically utilizes a porous polymer or porous glass substrate to entrap the fluorescent (or fluorescently-tagged) molecule. Porous polymer hydrogels are generally favored due to their ease of fabrication, low cost, adaptability, and biocompatibility. While hydrogels are ideal for both functional molecule suspension and fluid diffusion, their porosity and hydrophilicity are not always advantageous. The largest drawback of these properties is the hydrogel swelling they produce and the resulting geometric changes. This project investigated the limitations of fluorescent hydrogel-based sensors and the effects of unpredictable structural changes hydrogels undergo during typical, unrestrained swelling. The significance of covalent incorporation of the sensing fluorophore into the hydrogel matrix is also explored. Leaching tests were conducted using polyacrylamide (PAm) hydrogels which were impregnated with one of two pH sensitive fluorophores, one which bonded covalently with the hydrogel matrix during polymerization (fluorescein o-acrylate), and one which did not (fluorescein sodium). Once determined to be effective, the covalently bonding fluorophore was used to create constrained-dimension fluorescent pH sensors. These sensors were tested for effectiveness and reproducibility. All data was collected using a laboratory grade optical fibers, a USB spectrometer, and SpectraSuite software (Ocean Optics, 2010) unless otherwise specified.

Jukl, Jennifer Marie

138

Cyanine-based probe\\tag-peptide pair fluorescence protein imaging and fluorescence protein imaging methods  

DOEpatents

A molecular probe comprises two arsenic atoms and at least one cyanine based moiety. A method of producing a molecular probe includes providing a molecule having a first formula, treating the molecule with HgOAc, and subsequently transmetallizing with AsCl.sub.3. The As is liganded to ethanedithiol to produce a probe having a second formula. A method of labeling a peptide includes providing a peptide comprising a tag sequence and contacting the peptide with a biarsenical molecular probe. A complex is formed comprising the tag sequence and the molecular probe. A method of studying a peptide includes providing a mixture containing a peptide comprising a peptide tag sequence, adding a biarsenical probe to the mixture, and monitoring the fluorescence of the mixture.

Mayer-Cumblidge, M. Uljana; Cao, Haishi

2013-01-15

139

Fluorescent detection of protein kinase based on positively charged gold nanoparticles.  

PubMed

Herein, we report a fluorometric method for monitoring the activity and inhibition of protein kinase based on positively charged gold nanoparticles, (+)AuNPs. In this assay, when the cationic substrate peptide (S-peptide) is phosphorylated by protein kinase, the resulting negatively charged product peptide (P-peptide) will be adsorbed onto (+)AuNPs through electrostatic interaction, and the fluorescence of fluorescein isothiocyanate (FITC) on the peptide will be quenched by (+)AuNPs. Thus, the fluorescence of solution can respond to the activity of protein kinase. The feasibility of this (+)AuNPs-based method has been demonstrated by sensitive measurement of the activity of cAMP-dependent protein kinase (PKA) with a low detection limit (0.5mU?L(-1)). Furthermore, the system is successfully applied to estimate the IC50 value of PKA inhibitor H-89. The fast mix-and-readout detection process as well as the simple synthesis of the unmodified (+)AuNPs makes this proposed method a promising candidate for simple and cost-effective kinase activity detection and a good potential in high-throughput screening of kinase-related drugs. PMID:25059172

Lu, Guoyan; Tan, Penglong; Lei, Chunyang; Nie, Zhou; Huang, Yan; Yao, Shouzhou

2014-10-01

140

Determination of four lignans in Phyllanthus niruri L. by a simple high-performance liquid chromatography method with fluorescence detection.  

PubMed

A new and simple analytical method using HPLC with fluorescence detection was developed for the simultaneous determination of four lignans (phyllanthin, hypophyllanthin, phyltetralin and niranthin) in Phyllanthus niruri L. plant samples. Optimal separation was achieved with an isocratic mobile phase consisting of acetonitrile-water (55:45 v/v). The method recorded limits of detection (S/N=5) for phyllanthin at 0.61 ng/mL, hypophyllanthin at 6.02 ng/mL, phyltetralin at 0.61 ng/mL and niranthin at 1.22 ng/mL, being 80, 8, 80 and 40 times, respectively, lower when compared with those derived using HPLC-UV detection. The limits of quantification (S/N=12) were 4.88 ng/mL for phyllanthin and phyltetralin, 9.76 ng/mL for niranthin and 24.4 ng/mL for hypophyllanthin showing 40, 8 and 20 times, respectively, lower than those from the UV detection method. The within-day and between-day accuracy for the four lignans were between 98.1% and 102.9% while their precision values were below 2.2%. The mean recovery was between 92.5% and 110.1%. The method was then successfully applied for the quantification of lignans in P. niruri plant samples. The highest amount of lignans was found in the leaves followed by fruits, branches and stem, whilst the roots have the least amount of lignans. PMID:17418855

Murugaiyah, Vikneswaran; Chan, Kit-Lam

2007-06-22

141

A simple enzyme based biosensor on flexible plastic substrate  

NASA Astrophysics Data System (ADS)

An enzyme based biosensor was fabricated by employing a simple, inexpensive and rapid xurography fabrication process. The electrodes and channel were made from the conducting polymer poly(3,4-ethyelenedioxythiphene) poly(styrene sulfonate) (PEDOT:PSS). PEDOT:PSS was selectively deposited using a polyimide tape mask. The tape mask was peeled off from the substrate after annealing the polymer in vacuum. Polymer wells of defined dimensions were made and were attached to the device to accommodate the solutions. This sensor utilizes the change in current as a parameter to measure different analyte concentrations. Initial experiments were done by using the sensor for glucose detection. The sensor is able to detect the glucose concentrations approximately from 1 ?M to 10 mM range covering glucose in human saliva (8-210 ?M). The glucose oxidase activity was independently measured using colorimetric method and the results indicate that the sensor retains the enzyme activity and can be used as a biosensor to detect various analytes. The analyte of interest can be measured by preloading the corresponding enzyme into the wells.

Kanakamedala, Senaka K.; Alshakhouri, Haidar T.; Agarwal, Mangilal; Fang, Ji; Decoster, Mark A.

2010-08-01

142

Differential fluorescence quenching of fluorescent nucleic acid base analogues by native nucleic acid monophosphates.  

PubMed

Fluorescent nucleic acid base analogues (FBAs) are used widely as probes of DNA and RNA structure and dynamics. Of increasing utility are the pteridone adenosine analogues (6MAP, DMAP) and pteridine guanosine analogues (3MI, 6MI). These FBAs (collectively referred to as PTERs) are useful, in part, because their fluorescence quantum yields, Phi(f), are modulated by base stacking with native bases (NBs), making them sensitive reporters of DNA structure. The quenching mechanism has been hypothesized to be photoinduced electron transfer following selective excitation of the FBA, but hard evidence for this has been lacking. The degree of quenching shows some dependence on the neighboring bases, but there has been no real determination as to whether FBA*:NB complexes satisfy the basic thermodynamic requirement for spontaneous PET: a negative free energy for the electron transfer reaction. Indeed, quenching may result from entirely different mechanisms. To address these questions, Stern-Volmer (S-V) experiments were performed using the native-base monophosphate nucleotides (NMPs) GMP, AMP, CMP, and dTMP in aqueous solutions as quenchers to obtain quenching rate constants, k(q). Cyclic voltammetry (CV) and optical absorption and emission data of the PTERS were obtained in aprotic organic solvents. These data were used to obtain excited-state redox potentials from which electron transfer free energies were derived using the Rehm-Weller equation. The reorganization energies for PET were obtained using the Scandola-Balzani equation, taking into account the free energy contribution due to water. 6MAP*, DMAP*, and 3MI* gave negative free energies between -0.1 and -0.2 eV and reorganization energies of about 0.13 eV. They all displayed ET activation energies below the accessible thermal energy (0.038 eV = 3/2k(B)T, where k(B) is Boltzmann's constant) for all NMPs with the exception of CMP, whose activation barrier was only about 35% higher (approximately 0.05 eV). Thus, we conclude that these PTERs act as electron acceptors and promote NMP oxidation. However, 6MI* had positive ET free energies for all NMPs with the exception of GMP (and then only for nucleobase oxidation). The magnitudes of these free energies (> or = 0.45 eV for AMP, CMP, and dTMP) suggest that 6MI* may not quenched by PET. PMID:20387838

Narayanan, Madhavan; Kodali, Goutham; Singh, Vijay; Xing, Yangjun; Hawkins, Mary E; Stanley, Robert J

2010-05-01

143

A CTRW-based model of time-resolved fluorescence lifetime imaging in a turbid medium.  

PubMed

We develop an analytic model of time-resolved fluorescent imaging of photons migrating through a semi-infinite turbid medium bounded by an infinite plane in the presence of a single stationary point fluorophore embedded in the medium. In contrast to earlier models of fluorescent imaging in which photon motion is assumed to be some form of continuous diffusion process, the present analysis is based on a continuous-time random walk (CTRW) on a simple cubic lattice, the object being to estimate the position and lifetime of the fluorophore. Such information can provide information related to local variations in pH and temperature with potential medical significance. Aspects of the theory were tested using time-resolved measurements of the fluorescence from small inclusions inside tissue-like phantoms. The experimental results were found to be in good agreement with theoretical predictions provided that the fluorophore was not located too close to the planar boundary, a common problem in many diffusive systems. PMID:21057657

Chernomordik, Victor; Gandjbakhche, Amir H; Hassan, Moinuddin; Pajevic, Sinisa; Weiss, George H

2010-12-01

144

A CTRW-based model of time-resolved fluorescence lifetime imaging in a turbid medium  

NASA Astrophysics Data System (ADS)

We develop an analytic model of time-resolved fluorescent imaging of photons migrating through a semi-infinite turbid medium bounded by an infinite plane in the presence of a single stationary point fluorophore embedded in the medium. In contrast to earlier models of fluorescent imaging in which photon motion is assumed to be some form of continuous diffusion process, the present analysis is based on a continuous-time random walk (CTRW) on a simple cubic lattice, the objective being to estimate the position and lifetime of the fluorophore. This can provide information related to local variations in pH and temperature with potential medical significance. Aspects of the theory were tested using time-resolved measurements of the fluorescence from small inclusions inside tissue-like phantoms. The experimental results were found to be in good agreement with theoretical predictions provided that the fluorophore was not located too close to the planar boundary, a common problem in many diffusive systems.

Chernomordik, Victor; Gandjbakhche, Amir H.; Hassan, Moinuddin; Pajevic, Sinisa; Weiss, George H.

2010-12-01

145

Sensitive and selective detection of nitrite ion based on fluorescence superquenching of conjugated polyelectrolyte.  

PubMed

In recent years, conjugated polyelectrolytes (CPEs) that feature good water-solubility have drawn great attention as optical transducers in high sensitive bio- and chemo-sensors due to their predominant optical/electronic properties and remarkable signal amplification. Herein, a sensitive and selective assay for nitrite ion has successfully been developed based on the fluorescence superquenching of an anionic CPE, PPESO(3). With the sensor format composed of PPESO(3) and H(+), Fe(2+) can easily be oxidized into Fe(3+) in the presence of NO(2)(-), and the later dramatically quenches the fluorescence of PPESO(3). Indeed, the inclusion of conjugated polyelectrolyte into the sensory scheme can give rise to a notable enhancement of fluorescence response, which endows the newly proposed NO(2)(-) probe with high sensitivity. Thus, nitrite ion within a relatively wide concentration range (0-70 microM) can be determined in a rather simple and sensitive manner with a detection limit of 0.62 microM (approximately 28 ppb). Additionally, most other anions such as halogen ions, acetate, sulfate, carbonate, phosphate and even nitrate, show minor interference on the NO(2)(-) detection. PMID:20188893

Zhang, Tao; Fan, Hongliang; Jin, Qinhan

2010-04-15

146

A VBA-based Simulation for Teaching Simple Linear Regression  

ERIC Educational Resources Information Center

In spite of the name, simple linear regression presents a number of conceptual difficulties, particularly for introductory students. This article describes a simulation tool that provides a hands-on method for illuminating the relationship between parameters and sample statistics.

Jones, Gregory Todd; Hagtvedt, Reidar; Jones, Kari

2004-01-01

147

Fluorescent indicators for Ca2+based on green fluorescent proteins and calmodulin  

Microsoft Academic Search

Important Ca2+ signals in the cytosol and organelles are often extremely localized and hard to measure. To overcome this problem we have constructed new fluorescent indicators for Ca2+ that are genetically encoded without cofactors and are targetable to specific intracellular locations. We have dubbed these fluorescent indicators `cameleons'. They consist of tandem fusions of a blue- or cyan-emitting mutant of

Atsushi Miyawaki; Juan Llopis; Roger Heim; J. Michael McCaffery; Joseph A. Adams; Mitsuhiko Ikura; Roger Y. Tsien

1997-01-01

148

The photophysics of LOV-based fluorescent proteins--new tools for cell biology.  

PubMed

LOV-based fluorescent proteins (FPs) are an alternative class of fluorescent reporters with unique properties which complement the well-established proteins of the GFP family. One of the most important features of LOV-based FPs is the independence of molecular oxygen for the development of their specific fluorescence. Furthermore, they are characterized by small size and rapid signal development. Over the last few years, a number of different bacterial and plant LOV-based fluorescent proteins such as FbFP, iLOV and miniSOG have been developed and optimized. In this report, we comparatively have characterized the photophysical properties of nine different LOV-based fluorescent proteins including the excitation and emission maxima, the extinction coefficient, the fluorescence quantum yield, the average fluorescence lifetime and the photostability. The unified characterization of the LOV-based FPs provides a useful guide to apply them as in vivo tools for quantitative analyses and biological imaging. PMID:24500379

Wingen, Marcus; Potzkei, Janko; Endres, Stephan; Casini, Giorgia; Rupprecht, Christian; Fahlke, Christoph; Krauss, Ulrich; Jaeger, Karl-Erich; Drepper, Thomas; Gensch, Thomas

2014-06-01

149

Solar Energy Conversion Based on the Principle of Fluorescent Collectors.  

National Technical Information Service (NTIS)

The development of fluorescent collectors for solar energy conversion is described. Spectra, fluorescent quantum yields, stability, and absorption properties of dyes were studied. The synthesis of dyes and the manufacture of collector plates are discussed...

A. Goetzberger K. Heidler W. Stahl H. R. Wilson V. Wittwer

1984-01-01

150

Fluorescence Resonance Energy Transfer-Based Stoichiometry in Living Cells  

Microsoft Academic Search

Imaging of fluorescence resonance energy transfer (FRET) between fluorescently labeled molecules can measure the timing and location of intermolecular interactions inside living cells. Present microscopic methods measure FRET in arbitrary units, and cannot discriminate FRET efficiency and the fractions of donor and acceptor in complex. Here we describe a stoichiometric method that uses three microscopic fluorescence images to measure FRET

Adam Hoppe; Kenneth Christensen; Joel A. Swanson

2002-01-01

151

Rhodamine-based 'turn-on' fluorescent probe for Cu(II) and its fluorescence imaging in living cells.  

PubMed

A novel rhodamine spirolactam derivative 3',6'-Bis(diethylamino)-2-(2-hydroxyethylamino) spiro[isoindoline-1,9'-xanthen]-3-one (RO1) was synthesized, and characterized by high-resolution mass spectrometry (HRMS), X-ray crystallography, Infrared spectroscopy (IR), and (1)H NMR and (13)C NMR spectroscopy. RO1 exhibited highly sensitive and exclusively selective fluorescence response toward Cu(2+) over other metal ions with a detection limit of 0.56ppb in mixed aqueous solution. The fluorescence was pH-independent in the wide range pH 3.1-11.6. The turn-on fluorescence enhancement of the probe is based on Cu(2+) induced ring-opening mechanism of the rhodamine spirolactam. Moreover, by means of fluorescence microscopy experiments, it was demonstrated that RO1 could monitor trace Cu(2+) changes by live cell imaging. PMID:23570786

Tian, Mao-Zhong; Hu, Ming-Ming; Fan, Jiang-Li; Peng, Xiao-Jun; Wang, Jing-Yun; Sun, Shi-Guo; Zhang, Rong

2013-05-15

152

Simple method of determination of copper, mercury and lead in potable water with preliminary pre-concentration by total reflection X-ray fluorescence spectrometry  

Microsoft Academic Search

Total reflection X-ray fluorescence spectrometry and chemical pre-concentration procedures have been applied for the analysis of trace concentrations of copper, mercury, and lead in drinking water samples. A simple total reflection module has been used in X-ray measurements. The elements under investigation were pre-concentrated by complexation using a mixture of carbamates followed by solvent extraction with methyl isobutyl ketone. The

B. Ho?y?ska; B. Ostachowicz; D. W?grzynek

1996-01-01

153

Fluorescence turn-on sensing of protein based on mannose functionalized perylene bisimides and its fluorescence imaging.  

PubMed

A new water-soluble glycocluster based on perylene bisimides PBI-12-Man has been designed and synthesized, and its specific and selective binding property with Concanavalin A (Con A) has been investigated by fluorescence spectroscopy and circular dichroism (CD) spectroscopy, which showed strong binding affinity for Con A with the binding constant of 8.2×10(5)M(-1) for monomeric mannose unit, two orders of magnitude higher than the corresponding monosaccharide ligand. Most interestingly, a fluorescence enhancement of PBI-12-Man was observed upon binding with Con A because of deaggregation of the self-assembly of PBI-12-Man induced by carbohydrate-protein interaction, and the further study of the fluorescence enhancement with macrophage cells showed that PBI-12-Man as a biocompatible agent had fluorescence imaging of the surface mannose receptor of the cells. Such fluorescence turn-on sensing of protein based on carbohydrate-protein interactions would facilitate the development of new protein-specific fluorescent probe for diagnosis and molecular imaging under live cell conditions. PMID:24607619

Wang, Ke-Rang; An, Hong-Wei; Rong, Rui-Xue; Cao, Zhi-Ran; Li, Xiao-Liu

2014-08-15

154

A carbon nanotubes based fluorescent aptasensor for highly sensitive detection of adenosine deaminase activity and inhibitor screening in natural extracts.  

PubMed

A carbon nanotubes (CNTs) based fluorescent aptasensor was developed for adenosine deaminase (ADA) activity detection and inhibitor screening by using adenosine (AD) as the substrate. This sensing system consists of CNTs, AD, split anti-AD aptamer fragment and dye-labeled aptamer fragment. In the absence of ADA, two aptamer fragments bind simultaneously with AD to form an AD-aptamer complex. This AD-aptamer complex cannot adsorb onto CNTs, and has high fluorescence intensity. When ADA is introduced into this system, ADA can convert AD into inosine, which has not affinity to the split anti-AD aptamer fragment. Thus, the split anti-AD aptamer fragments were adsorbed onto CNTs via strong ?-? stacking interactions, resulting in the quenching of the fluorescence of the dye-labeled aptamer fragment. The proposed aptasensor can detect ADA activity from 0.005 to 0.2U/mL with a low detection limit of 0.002U/mL. Moreover, it has been also demonstrated that this CNTs-based fluorescence aptasensor is suitable for ADA inhibitor screening from traditional Chinese medicine (TCM). Considering the superior sensitivity and specificity, the proposed CNTs-based fluorescent aptasensor can be expected to provide a simple, cost-effective and sensitive platform for the detection of ADA activity and screening of potential drugs. PMID:24682016

Hu, Kun; Huang, Yong; Wang, Sheng'e; Zhao, Shulin

2014-07-01

155

Organic Liquids-Responsive ?-Cyclodextrin-Functionalized Graphene-Based Fluorescence Probe: Label-Free Selective Detection of Tetrahydrofuran.  

PubMed

In this study, a label-free graphene-based fluorescence probe used for detection of volatile organic liquids was fabricated by a simple, efficient and low-cost method. To fabricate the probe, a bio-based ?-cyclodextrin (?-CD) was firstly grafted on reduced graphene surfaces effectively and uniformly, as evidenced by various characterization techniques such as Ultraviolet/Visible spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, scanning electron microscopy and transmission electron microscopy. The subsequent inclusion of Rhodamine B (RhB) into the inner cavities of the ?-CD grafted on the graphene surfaces was achieved easily by a solution mixing method, which yielded the graphene-based fluorescent switch-on probe. In addition, the gradual and controllable quenching of RhB by Fluorescence Resonance Energy Transfer from RhB to graphene during the process of stepwise accommodation of the RhB molecules into the ?-CD-functionalized graphene was investigated in depth. A wide range of organic solvents was examined using the as-fabricated fluorescence probe, which revealed the highest sensitivity to tetrahydrofuran with the detection limit of about 1.7 ?g/mL. Some insight into the mechanism of the different responsive behaviors of the fluorescence sensor to the examined targets was also described. PMID:24914894

Hu, Huawen; Xin, John H; Hu, Hong; Wang, Xiaowen; Lu, Xinkun

2014-01-01

156

Synthesis of fluorescent carbon dots via simple acid hydrolysis of bovine serum albumin and its potential as sensitive sensing probe for lead (II) ions.  

PubMed

Carbon dots have great potential to be utilised as an optical sensing probe due to its unique photoluminescence and less toxic properties. This work reports a simple and novel synthesis method of carbon dots via direct acid hydrolysis of bovine serum albumin protein in a one-pot approach. Optimisation of the important synthetic parameters has been performed which consists of temperature effect, acid to protein ratio and kinetics of reaction. Higher temperature has promoted better yield with shorter reaction time. The carbon dots obtained shows a strong emission at the wavelength of 400 nm with an optimum excitation of 305 nm. The potential of the carbon dots as optical sensing probe has been investigated on with different cations that are of environmental and health concern. The fluorescence of the carbon dots was significantly quenched particularly by lead (II) ions in a selective manner. Further analytical study has been performed to leverage the performance of the carbon dots for lead (II) ions sensing using the standard Stern-Volmer relationship. The sensing probe has a dynamic linear range up to 6.0 mM with a Stern-Volmer constant of 605.99 M(-1) and a limit of detection (LOD) of 5.05 ?M. The probe performance was highly repeatable with a standard deviation below 3.0%. The probe suggested in this study demonstrates the potential of a more economical and greener approach that uses protein based carbon dots for sensing of heavy metal ions. PMID:24148375

Wee, Shui Shui; Ng, Yann Huey; Ng, Sing Muk

2013-11-15

157

Measurement of plasma volume using fluorescent silica-based nanoparticles  

PubMed Central

Plasma volume (PV) is an important determinant of cardiovascular function and organ perfusion, and it is the target of infusion and diuretic therapies in daily clinical practice. Despite its fundamental importance PV is not commonly measured because available methods of tracer dilution are reliant on dye substances that suffer from numerous drawbacks including binding plasma proteins, spectral changes, and clearance kinetics that complicate analysis and interpretation. To address these issues, we have tested the utility of fluorescent nanoparticles comprised of a dye-rich silica core and polyethylene glycol-coated shell. Photophysical and visual analysis showed discrete size-gradated nanoparticle populations could be synthesized within a distribution tolerance of ±4 nm, which were optically unaffected in the presence of plasma/albumin. In normal mice, the cutoff for renal filtration of nanoparticles from blood into urine was ?11 nm. A linear relationship between body weight and PV was readily determined in mice administered far red fluorescent nanoparticles sized either 20 or 30 nm. PV measurements using nanoparticles were correlated to values obtained with Evans blue dye. Induced expansion or contraction of PV was demonstrated with albumin or furosemide administration, respectively, in mice. Longitudinal experiments >30 min required matched untreated control mice to correct for nanoparticle loss (?30%) putatively to the reticuloendothelial/phagocyte system. Collectively, the findings support a nanotechnology-based solution to methodological problems in measure of PV, notably in clinical settings where information on hemodynamic changes may improve treatment of injury and disease.

Eisner, Christoph; Ow, Hooisweng; Yang, Tianxin; Jia, Zhanjun; Dimitriadis, Emilios; Li, Lingli; Wang, Kenneth; Briggs, Josephine; Levine, Mark; Schnermann, Jurgen

2012-01-01

158

Optical biopsy fiber-based fluorescence spectroscopy instrumentation  

NASA Astrophysics Data System (ADS)

Native fluorescence spectroscopy of biomolecules has emerged as a new modality to the medical community in characterizing the various physiological conditions of tissues. In the past several years, many groups have been working to introduce the spectroscopic methods to diagnose cancer. Researchers have successfully used native fluorescence to distinguish cancerous from normal tissue samples in rat and human tissue. We have developed three generations of instruments, called the CD-scan, CD-ratiometer and CD-map, to allow the medical community to use optics for diagnosing tissue. Using ultraviolet excitation and emission spectral measurements on both normal and cancerous tissue of the breast, gynecology, colon, and aerodigestive tract can be separated. For example, from emission intensities at 340 nm to 440 nm (300 nm excitation), a statistically consistent difference between malignant tissue and normal or benign tissue is observed. In order to utilize optical biopsy techniques in a clinical setting, the CD-scan instrument was developed, which allows for rapid and reliable in-vitro and in-vivo florescence measurements of the aerodigestive tract with high accuracy. The instrumentation employs high sensitivity detection techniques which allows for lamp excitation, small diameter optical fiber probes; the higher spatial resolution afforded by the small diameter probes can increase the ability to detect smaller tumors. The fiber optic probes allow for usage in the aerodigestive tract, cervix and colon. Needle based fiber probes have been developed for in-vivo detection of breast cancer.

Katz, Al; Ganesan, S.; Yang, Yuan-Long; Tang, Gui C.; Budansky, Y.; Celmer, Edward J.; Savage, Howard E.; Schantz, Stimson P.; Alfano, Robert R.

1996-04-01

159

Coordination polymer based on cyano: Synthesis, crystal structure, and fluorescence  

SciTech Connect

One novel 2-D polythreading framework named as [Cu{sub 3}(CN){sub 3}(NH{sub 3})] (1), was obtained through the self-assembling of CuCN under hydrothermal reaction. It is remarkable that there is a 26-membered [Cu{sub 10}(CN){sub 8}] decanuclear metallamacrocycle with the effective size of ca. 16.8x6.83 A{sup 2} along the a-axis. These 2-D layers stack in an ..ABAB...staggered fashion, with the lateral {l_brace}(CN)Cu{sub 3}(NH{sub 3}){r_brace} moieties of each layer inserting into the voids of the decanuclear metallamacrocycles from two adjacent layers. Optical diffuse reflectance spectrum and the result of DFT calculation reveal that 1 is potential direct semiconducting material. In the solid state at room temperature, 1 shows bright yellow fluorescence under ultraviolet light illumination. Its emissive excited state is primarily attributed to the LMCT, LLCT and {sup 3}[MMLCT] excited state, based on the result of DFPT calculation. - Graphical abstract: One novel 2-D polythreading framework [Cu{sub 3}(CN){sub 3}(NH{sub 3})] (1) obtained through the self-assembling of CuCN under hydrothermal reaction shows bright yellow fluorescence at room temperature.

Fang Zhenlan; He Jiangang; Ju Qiang; Wu Xiaoyuan [State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China); Lu Canzhong, E-mail: czlu@fjirsm.ac.c [State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China)

2010-07-15

160

Beer's-Law-Based, Simple Spectral Model for Direct Normal and Diffuse Horizontal Irradiance.  

National Technical Information Service (NTIS)

A spectral model for cloudless days that uses simple mathematical expressions and tabulated look-up tables to generate direct normal and diffuse horizontal irradiance is presented. The model is based on modifications to previously published simple models ...

R. E. Bird

1982-01-01

161

A Simple Sensitive ESIPT On-Off Fluorescent Sensor for Selective Detection of Al3+ in Water  

PubMed Central

A highly selective and sensitive fluorescent sensor for Al3+ has been developed. The sensor shows great fluorescence turn-on upon binding Al3+ in complete water, giving strong blue emission. In addition, the sensor’s turn-on exhibits excellent selectivity to Al3+ cation, with only a slight interference from Zn2+. These findings suggest that the developed Al3+ sensor could be a useful molecular probe for practical applications.

Wang, Junfeng

2014-01-01

162

Highly Selective Fluorescent Sensing of Proteins Based on a Fluorescent Molecularly Imprinted Nanosensor  

PubMed Central

A fluorescent molecularly imprinted nanosensor was obtained by grafting imprinted polymer onto the surface of multi-wall carbon nanotubes and post-imprinting treatment with fluorescein isothiocyanate (FITC). The fluorescence of lysozyme-imprinted polymer (Lys-MIP) was quenched more strongly by Lys than that of nonimprinted polymer (NIP), which indicated that the Lys-MIP could recognize Lys. The resulted imprinted material has the ability to selectively sense a target protein, and an imprinting factor of 3.34 was achieved. The Lys-MIP also showed selective detection for Lys among other proteins such as cytochrome C (Cyt C), hemoglobin (HB) and bovine serum albumin (BSA) due to the imprinted sites in the Lys-MIP. This approach combines the high selectivity of surface molecular imprinting technology and fluorescence, and converts binding events into detectable signals by monitoring fluorescence spectra. Therefore, it will have further applications for Lys sensing.

Deng, Qiliang; Wu, Jianhua; Zhai, Xiaorui; Fang, Guozhen; Wang, Shuo

2013-01-01

163

Frequency-domain flow cytometry: fluorescence-lifetime-based sensing technology for analyzing cells and chromosomes labeled with fluorescent probes  

NASA Astrophysics Data System (ADS)

A flow cytometer has been developed that combines flow cytometry (FCM) and fluorescence lifetime spectroscopy measurement principles to provide unique capabilities for making frequency-domain, excited-state lifetime measurements on cells/chromosomes labeled with fluorescent probes, while preserving conventional FCM capabilities. Cells are analyzed as they intersect a high-frequency, intensity-modulated (sine-wave) laser excitation beam. Fluorescence signals are processed by (1) low-pass filtering to obtain conventional FCM dc-excited signals and (2) phase-sensitive detection electronics to resolve heterogeneous fluorescence based on differences in lifetimes expressed as phase-shifts and to quantify fluorescence lifetimes in real time. Processed signals are displayed as frequency distribution histograms and bivariate contour diagrams. Recent examples of biological applications include: (1) lifetime histograms recorded on autofluorescent human lung fibroblasts, murine thymus cells labeled with antibodies conjugated to fluorophores for studying fluorescence quenching as a function of antibody dilution and F/P ratio, and on cultured cells, nuclei, and chromosomes stained with DNA-binding fluorochromes and (2) phase-resolved, fluorescence signal- intensity histograms recorded on autofluorescent HLFs labeled with immunofluorescence markers and on murine thymus cells labeled with Red 613-antiThy 1.2 and propidium iodide (PI positive `dead' cells) to demonstrate the resolution of signals from highly overlapping emission spectra. This technology will increase the number of fluorescent markers usable in multilabeling studies and lifetimes can be used as spectroscopic probes to study the interaction of markers with their targets, each other, and the surrounding microenvironment.

Steinkamp, John A.; Crissman, Harry A.; Lehnert, Bruce E.; Lehnert, Nancy M.; Deka, Chiranjit

1997-05-01

164

Coordination polymer based on cyano: Synthesis, crystal structure, and fluorescence  

NASA Astrophysics Data System (ADS)

One novel 2-D polythreading framework named as [Cu 3(CN) 3(NH 3)] ( 1), was obtained through the self-assembling of CuCN under hydrothermal reaction. It is remarkable that there is a 26-membered [Cu 10(CN) 8] decanuclear metallamacrocycle with the effective size of ca. 16.8×6.83 Å 2 along the a-axis. These 2-D layers stack in an ··ABAB···staggered fashion, with the lateral {(CN)Cu 3(NH 3)} moieties of each layer inserting into the voids of the decanuclear metallamacrocycles from two adjacent layers. Optical diffuse reflectance spectrum and the result of DFT calculation reveal that 1 is potential direct semiconducting material. In the solid state at room temperature, 1 shows bright yellow fluorescence under ultraviolet light illumination. Its emissive excited state is primarily attributed to the LMCT, LLCT and 3[MMLCT] excited state, based on the result of DFPT calculation.

Fang, Zhen-Lan; He, Jian-Gang; Ju, Qiang; Wu, Xiao-Yuan; Lu, Can-Zhong

2010-07-01

165

CuInS2 quantum dots-based fluorescence turn off/on probe for detection of melamine.  

PubMed

In this paper, a sensitive and simple method for the determination of melamine (MA) was developed based on the fluorescence changes of the water-soluble CuInS(2) quantum dots (QDs). The water-soluble CuInS(2) QDs capped by mercaptopropionic acid (MPA) was directly synthesized by hydrothermal method based on our previous report. The fluorescence emission of CuInS(2) QDs was quenched by the oxidation of the surface of the QDs with H(2)O(2), and the quenched fluorescence of CuInS(2) QDs could be recovered upon the addition of small amounts of MA, which might be due to the surface passivation of the CuInS(2) QDs by MA. The other amino acids such as glycine and lysine had no effect on the quenched fluorescence of CuInS(2) QDs. Under optimum conditions, there was a good linear relationship between the fluorescence intensity of CuInS(2) QDs and the concentration range of MA from 1.0×10(-8) to 1.0×10(-5) mol/L with a detection limit as low as 5 nM. The proposed method was successfully applied to detect trace MA in raw milk with satisfactory results. Compared with previous reports, the proposed method manifested several advantages such as high sensitivity, short analysis time, low cost and ease of operation. PMID:23158336

Liu, Siyu; Hu, Junjie; Zhang, Hao; Su, Xingguang

2012-11-15

166

Fluorescence "turn on" detection of mercuric ion based on bis(dithiocarbamato)copper(II) complex functionalized carbon nanodots.  

PubMed

A new "turn on" fluorescence nanosensor for selective Hg(2+) determination is reported based on bis(dithiocarbamato)copper(II) functionalized carbon nanodots (CuDTC2-CDs). The CuDTC2 complex was conjugated to the prepared amine-coated CDs by the condensation of carbon disulfide onto the nitrogen atoms in the surface amine groups, followed by the coordination of copper(II) to the resulting dithiocarbamate groups (DTC) and finally by the additional coordination of ammonium N-(dithicarbaxy) sarcosine (DTCS) to form the CuDTC2-complexing CDs. The CuDTC2 complex at surface strongly quenched the bright-blue fluorescence of the CDs by a combination of electron transfer and energy transfer mechanism. Hg(2+) could immediately switch on the fluorescence of the CuDTC2-CDs by promptly displacing the Cu(2+) in the CuDTC2 complex and thus shutting down the energy transfer pathway, in which the sensitive limit for Hg(2+) as low as 4 ppb was reached. Moreover, a paper-based sensor has been fabricated by printing the CuDTC2-CDs probe ink on a piece of cellulose acetate paper using a commercial inkjet printer. The fluorescence "turn on" on the paper provided the most conveniently visual detection of aqueous Hg(2+) ions by the observation with naked eye. The very simple and effective strategy reported here facilitates the development of portable and reliable fluorescence nanosensors for the determination of Hg(2+) in real samples. PMID:24377316

Yuan, Chao; Liu, Bianhua; Liu, Fei; Han, Ming-Yong; Zhang, Zhongping

2014-01-21

167

Fluorescent detection of an anthrax biomarker based on PVA film.  

PubMed

Due to the dangerous nature of anthrax, the development of a cost-effective, sensitive and field-portable sensor for the anthrax biomarker--calcium dipicolinate (CaDPA)--is of exceptional significance for both military and civilian use. Herein, a flexible polymer-film-based ratiometric sensor for detecting CaDPA was demonstrated. A reference dye and a probe ligand were covalently immobilized onto the film surface through a highly selective and efficient "click chemistry" reaction. The reference dye, whose fluorescence intensity does not change with varying amounts of CaDPA, offers a non-interfering internal calibration. The ethylenediaminetetraacetic acid (EDTA)-based ligand binds with Eu(III) and serves as the probe. In the absence of CaDPA, the film sensor exhibited almost no red fluorescence because the Eu(III) ions themselves give no emission without sensitization by CaDPA owing to the small molar absorption coefficients of Eu(III) ions. The presence of CaDPA induces a significantly enhanced emission intensity of the sensor, and thereby enables the film as a ratiometric sensor for CaDPA. This sensor can selectively detect CaDPA in water with a detection limit of 100 nM. Moreover, this sensor exhibited strong anti-interfering capability, it can not only be used in milieus that contain various amino acids and some biologically-abundant cations, but can also be usable in some biological fluids such as urine and serum. This test-paper-like film sensor is suitable for portable field analysis and needs no extra protective measures during transport due to its flexibility, and it can easily be separated from the analyte solution after the detection. PMID:21796290

Ma, Boling; Zeng, Fang; Zheng, Fangyuan; Wu, Shuizhu

2011-09-21

168

Anthracene based base-discriminating fluorescent oligonucleotide probes for SNPs typing: synthesis and photophysical properties.  

PubMed

2- and 9-Anthracenecarboxamide labeled 2'-deoxyuridines were synthesized and their photophysical properties were examined. These oligonucleonucleotide probes are capable of detecting adenine base on a target DNA sequence. It was also found that 2-anthracene based oligonucleotide probe is more efficient than the corresponding 9-anthracene based oligonucleotide in the application for DNA chip based SNP detection, due to its longer emission wavelength and high fluorescence intensity. PMID:16890446

Saito, Yoshio; Motegi, Kaori; Bag, Subhendu Sekhar; Saito, Isao

2008-01-01

169

A SIMPLE based discontinuous Galerkin solver for steady incompressible flows  

NASA Astrophysics Data System (ADS)

In this paper we present how the well-known SIMPLE algorithm can be extended to solve the steady incompressible Navier-Stokes equations discretized by the discontinuous Galerkin method. The convective part is discretized by the local Lax-Friedrichs fluxes and the viscous part by the symmetric interior penalty method. Within the SIMPLE algorithm, the equations are solved in an iterative process. The discretized equations are linearized and an equation for the pressure is derived on the discrete level. The equations obtained for each velocity component and the pressure are decoupled and therefore can be solved sequentially, leading to an efficient solution procedure. The extension of the proposed scheme to the unsteady case is straightforward, where fully implicit time schemes can be used. Various test cases are carried out: the Poiseuille flow, the channel flow with constant transpiration, the Kovasznay flow, the flow into a corner and the backward-facing step flow. Using a mixed-order formulation, i.e. order k for the velocity and order k-1 for the pressure, the scheme is numerically stable for all test cases. Convergence rates of k+1 and k in the L2-norm are observed for velocity and pressure, respectively. A study of the convergence behavior of the SIMPLE algorithm shows that no under-relaxation for the pressure is needed, which is in strong contrast to the application of the SIMPLE algorithm in the context of the finite volume method or the continuous finite element method. We conclude that the proposed scheme is efficient to solve the steady incompressible Navier-Stokes equations in the context of the discontinuous Galerkin method comprising hp-accuracy.

Klein, Benedikt; Kummer, Florian; Oberlack, Martin

2013-03-01

170

Simple and inexpensive immunoassay-based diagnostic tests  

Microsoft Academic Search

Simple and inexpensive yet sensitive and robust diagnostic tests are critically needed for resource-poor settings to enable\\u000a timely diagnosis and effective use of limited health care resources. Current tests are often too expensive, too slow, or have\\u000a compromised clinical performance, and they often require health care professional to perform the test. In addition, most assays\\u000a are not intended to be

Henna Päkkilä; Tero Soukka

2011-01-01

171

Sensitive fluorescent detection of melamine in raw milk based on the inner filter effect of Au nanoparticles on the fluorescence of CdTe quantum dots.  

PubMed

A simple, rapid and sensitive fluorescent assay for determination of melamine has been developed based on inner filter effect (IFE) of gold nanoparticles (AuNPs) on the fluorescence of CdTe quantum dots (QDs). When thioglycolic acid-capped CdTe QDs was mixed with citrate-stabilized AuNPs, the fluorescence of CdTe QDs was significantly quenched via the IFE of AuNPs. With the presence of melamine, melamine could induce the aggregation and corresponding absorbance change of AuNPs, which then resulted in the recovery of IFE-decreased emission of CdTe QDs. Under the optimum conditions, the detection limit for melamine in raw milk was 0.02mgL(-1). The application of this method in samples of melamine-spiked raw milk suggested a recovery between 103% and 104%. Therefore, the obvious merits provided by the present assay, such as simplicity, rapidity, low cost, and high sensitivity, would make it promising for on-site screening of melamine adulterant in raw milk. PMID:22953938

Zhang, Minwei; Cao, Xianyi; Li, Hongkun; Guan, Fengrui; Guo, Jiajia; Shen, Fei; Luo, Yeli; Sun, Chunyan; Zhang, Ligong

2012-12-01

172

Synthesis and fluorescence study of 7-azaindole in DNA oligonucleotides replacing a purine base  

PubMed Central

The fluorescence spectroscopy of 7-azaindole (7aIn) incorporated in DNA oligonucleotides is investigated. Incorporation of 7aIn into DNA oligonucleotides is accomplished through standard solid-phase phosphoramidite chemistry. Fluorescence emission of the 7aIn chromophore shifts slightly to the red (from 386 nm to 388 nm) upon glycosylation at the N ? 1 position, but its relative fluorescence quantum yield increases 23 times, from 0.023 to 0.53. Upon incorporation into DNA, the fluorescence emission of 7aIn is greatly quenched with fluorescence quantum yields of 0.020 and 0.016 in single and double strand DNA, respectively. The fluorescence emission for 7aIn in DNA oligonucleotides shifts to the blue with an emission maximum at 379 nm. Both the strong fluorescence quenching and the blue shift of the emission spectrum signify that 7aIn is stacked with neighboring DNA bases in both single and double strand DNA. As the duplex DNA melts due to temperature increase, the fluorescence of the 7aIn chromophore increases, indicating the transition from the less fluorescent duplex DNA to the more fluorescent single strand DNA. Since this fluorescent 7aIn is a structural analog of purine, its fluorescence property may be utilized as a probe for studying nucleic acid structure and dynamics.

Wang, Ke; Stringfellow, Sandra; Dong, Shiming; Yu, Hongtao

2013-01-01

173

Fluorescence guided diffusion optical tomography based on wavelet transform and singular value decomposition  

NASA Astrophysics Data System (ADS)

A novel method for optical breast imaging was presented based on fluorescence guided diffusion optical tomography (DOT). In this paper, the time-domain fluorescence parameters (yield and lifetime) were reconstructed based on discrete wavelet transform at first, then the fluorescence images were used to guide and constrain the diffusion optical tomography reconstruction, and the image segmentation strategy based on wavelet coefficient was applied to improve the image quality in DOT. To validate the proposed method, the numerical simulation was performed to demonstrate its computational efficacy. The results showed the feasibility of this method, and the spatial resolution, quantification and computational efficiency in fluorescence diffusion optical tomography and DOT were enhanced evidently.

Zhang, Limin; Zhang, Wei; Gao, Feng; Li, Jiao; Zhao, Huijuan

2012-02-01

174

Fluorescence-based test of fiber-optic continuity  

Microsoft Academic Search

There is considerable interest in the use of lasers and optical fibers for the initiation of pyrotechnics. In this application the need develops for a means of testing the continuity of the initiation fiber before initiation of the pyrotechnic. We present proof of the feasibility of an unambiguous continuity test using the fluorescence returned by the fiber from a fluorescent

D. P. Norwood; C. Vinches; J. F. Anderson; W. F. Reed

1997-01-01

175

Coupling evaporation-based, microfluidic concentration and confocal fluorescence spectroscopy  

Microsoft Academic Search

Detection limits in confocal fluorescence spectroscopy (CFS) have traditionally been restrained by the low molecular detection efficiencies associated with femtoliter probe volumes. In this report, we address this issue by designing a microfluidic evaporator capable of accepting large sample volumes and concentrating biomolecules to a nanoliter-sized, interrogation chamber. Single molecule fluorescence detection within this chamber is enhanced through microfluidic recirculation,

C. M. Puleo; H. C. Yeh; K. J. Liu; T. Rane; T. H. Wang

2008-01-01

176

Visible-near-infrared and fluorescent copper sensors based on julolidine conjugates: selective detection and fluorescence imaging in living cells.  

PubMed

We present novel Schiff base ligands julolidine-carbonohydrazone 1 and julolidine-thiocarbonohydrazone 2 for selective detection of Cu(2+) in aqueous medium. The planar julolidine-based ligands can sense Cu(2+) colorimetrically with characteristic absorbance in the near-infrared (NIR, 700-1000 nm) region. Employing molecular probes 1 and 2 for detection of Cu(2+) not only allowed detection by the naked eye, but also detection of varying micromolar concentrations of Cu(2+) due to the appearance of distinct coloration. Moreover, Cu(2+) selectively quenches the fluorescence of julolidine-thiocarbonohydrazone 2 among all other metal ions, which increases the sensitivity of the probe. Furthermore, quenched fluorescence of the ligand 2 in the presence of Cu(2+) was restored by adjusting the complexation ability of the ligand. Hence, by treatment with ethylenediaminetetraacetic acid (EDTA), thus enabling reversibility and dual-check signaling, julolidine-thiocarbonohydrazone (2) can be used as a fluorescent molecular probe for the sensitive detection of Cu(2+) in biological systems. The ligands 1 and 2 can be utilized to monitor Cu(2+) in aqueous solution over a wide pH range. We have investigated the structural, electronic, and optical properties of the ligands using ab initio density functional theory (DFT) combined with time-dependent density functional theory (TDDFT) calculations. The observed absorption band in the NIR region is attributed to the formation of a charge-transfer complex between Cu(2+) and the ligand. The fluorescence-quenching behavior can be accounted for primarily due to the excited-state ligand 2 to metal (Cu(2+)) charge-transfer (LMCT) processes. Thus, experimentally observed characteristic NIR and fluorescence optical responses of the ligands upon binding to Cu(2+) are well supported by the theoretical calculations. Subsequently, we have employed julolidine-thiocarbonohydrazone 2 for reversible fluorescence sensing of intracellular Cu(2+) in cultured HEK293T cells. PMID:21882277

Maity, Debabrata; Manna, Arun K; Karthigeyan, D; Kundu, Tapas K; Pati, Swapan K; Govindaraju, T

2011-09-26

177

Fluorescence Rise Time Measurements for High Temperature Fluorescence-Based Thermometry  

Microsoft Academic Search

Certain ceramic-like phosphor materials exhibit bright fluorescence with a pronounced temperature dependence over a range which spans the cryogenic to 1700 C, depending on the specific phosphor. To measure temperature, a surface, for instance a turbine blade, is coated with the material. An optical system, sometimes including optical fibers, conveys stimulating light and collects the emission for analysis. Either emission

S. W. Allison; S. M. Goedeke; M. R. Cates; W. A. Hollerman; J. I. Eldridge; T. J. Bencic

2005-01-01

178

Microfluidic cell sorter-aided directed evolution of a protein-based calcium ion indicator with an inverted fluorescent response.  

PubMed

We demonstrate a simple, low cost and disposable microfluidic fluorescence activated cell sorting system (?FACS) for directed evolution of fluorescent proteins (FP) and FP-based calcium ion (Ca(2+)) indicators. The system was employed to pre-screen libraries of up to 10(6) variants of a yellow FP-based Ca(2+) indicator (Y-GECO) with throughput up to 300 cells per s. Compared to traditional manual screening of FP libraries, this system accelerated the discovery of improved variants and saved considerable time and effort during the directed evolution of Y-GECO. Y-GECO1, the final product of the ?FACS-aided directed evolution, has a unique fluorescence hue that places it in the middle of the spectral gap that separates the currently available green and orange FP-based Ca(2+) indicators, exhibits bright fluorescence in the resting (Ca(2+) free) state, and gives a large response to intracellular Ca(2+) fluctuations in live cells. PMID:24840546

Zhao, Yongxin; Abdelfattah, Ahmed S; Zhao, Yufeng; Ruangkittisakul, Araya; Ballanyi, Klaus; Campbell, Robert E; Harrison, D Jed

2014-07-24

179

Novel Chalcone-Based Fluorescent Human Histamine H3 Receptor Ligands as Pharmacological Tools  

PubMed Central

Novel fluorescent chalcone-based ligands at human histamine H3 receptors (hH3R) have been designed, synthesized, and characterized. Compounds described are non-imidazole analogs of ciproxifan with a tetralone motif. Tetralones as chemical precursors and related fluorescent chalcones exhibit affinities at hH3R in the same concentration range like the reference antagonist ciproxifan (hH3R pKi value of 7.2). Fluorescence characterization of our novel ligands shows emission maxima about 570?nm for yellow fluorescent chalcones and ?600?nm for the red fluorescent derivatives. Interferences to cellular autofluorescence could be excluded. All synthesized chalcone compounds could be used to visualize hH3R proteins in stably transfected HEK-293 cells using confocal laser scanning fluorescence microscopy. These novel fluorescent ligands possess high potential to be used as pharmacological tools for hH3R visualization in different tissues.

Tomasch, Miriam; Schwed, J. Stephan; Weizel, Lilia; Stark, Holger

2012-01-01

180

Heats of sublimation of nitramines based on simple parameters.  

PubMed

In this work, a simple procedure is introduced to determine heats of sublimation of nitramines as an important class of explosives. Molecular weight and one structural parameter of nitramines would be needed in the new method. Calculated heats of sublimation for well-known explosives such as HMX [1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane], RDX [1,3,5-trinitro-1,3,5-triazacyclohexane] and TETRYL [1-(methylnitramino)-2,4,6-trinitrobenzene] as well as new nitramines CL-20 [2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane] and TNAZ [1,3,3-trinitroazatidine] show good agreement with experimental data. R-squared value or the coefficient of determination of new correlation is 0.945. The root-mean-square deviation (RMS) from experiment for the predicted heats of sublimation by new method is 10.10 kJ/mol. PMID:17765395

Keshavarz, Mohammad Hossein; Yousefi, Mohammad Hassan

2008-04-15

181

Patch-based nonlocal functional for denoising fluorescence microscopy image sequences.  

PubMed

We present a nonparametric regression method for denoising 3-D image sequences acquired via fluorescence microscopy. The proposed method exploits the redundancy of the 3-D+time information to improve the signal-to-noise ratio of images corrupted by Poisson-Gaussian noise. A variance stabilization transform is first applied to the image-data to remove the dependence between the mean and variance of intensity values. This preprocessing requires the knowledge of parameters related to the acquisition system, also estimated in our approach. In a second step, we propose an original statistical patch-based framework for noise reduction and preservation of space-time discontinuities. In our study, discontinuities are related to small moving spots with high velocity observed in fluorescence video-microscopy. The idea is to minimize an objective nonlocal energy functional involving spatio-temporal image patches. The minimizer has a simple form and is defined as the weighted average of input data taken in spatially-varying neighborhoods. The size of each neighborhood is optimized to improve the performance of the pointwise estimator. The performance of the algorithm (which requires no motion estimation) is then evaluated on both synthetic and real image sequences using qualitative and quantitative criteria. PMID:19900849

Boulanger, Jérôme; Kervrann, Charles; Bouthemy, Patrick; Elbau, Peter; Sibarita, Jean-Baptiste; Salamero, Jean

2010-02-01

182

Ultrasensitive detection of lead (II) based on fluorescent aptamer-functionalized carbon nanotubes.  

PubMed

Lead contamination is a serious environmental problem with toxic effects in human. Here, we developed a simple and sensitive sensing method employing ATTO 647N/aptamer-SWNT ensemble for detection of Pb(2+). This method is based on the super quenching capability of single-walled carbon nanotubes (SWNTs), high affinity of the aptamer toward Pb(2+) and different propensities of ATTO 647N-aptamer and ATTO 647N-aptamer/Pb(2+) complex for adsorption on SWNTs. In the absence of Pb(2+), the fluorescence of ATTO 647N-aptamer is efficiently quenched by SWNTs. Upon addition of Pb(2+), the aptamer binds to its target, leading to the formation of a G-quadruplex/Pb(2+) complex and does not interact with SWNTs and ATTO 647N-aptamer starts fluorescing. This sensor exhibited a high selectivity toward Pb(2+) and a limit of detection (LOD) as low as 0.42nM was obtained. Also this sensor could be applied for detection of Pb(2+) ions in tap water and biological sample like serum with high sensitivity. PMID:24835552

Taghdisi, Seyed Mohammad; Emrani, Somayeh Sarreshtehdar; Tabrizian, Kaveh; Ramezani, Mohammad; Abnous, Khalil; Emrani, Ahmad Sarreshtehdar

2014-05-01

183

Synthesis, fluorescence study and biological evaluation of three Zn(II) complexes with Paeonol Schiff base  

Microsoft Academic Search

The synthesis of three Paeonol Schiff base ligand and their Zn(II) complexes are reported. The complexes were fully characterized by IR, 1H NMR, elemental analysis and molar conductivity. The experiment results show the three Zn(II) complexes can emit bright fluorescence at room temperature in DMF solution and solid state. The fluorescence quantum yields (?) of three Schiff base ligands and

Dong-Dong Qin; Zheng-Yin Yang; Gao-Fei Qi

2009-01-01

184

Neoplasm diagnostics based on fluorescence of polymethine dyes  

NASA Astrophysics Data System (ADS)

Investigated polymethine dye TICS has near IR bands of fluorescence and absorption within the transparency region of biological tissues. It can be detected up to 1.5 cm from the surface of the skin. The intensity of a fluorescence signal of TICS is linear for doses up to 2 mg/kg in both tumor and muscle tissue. The ratio of an intensity of light induced fluorescence in tumor tissue to one in muscle tissue is up to 3.6 for rapidly growing tumors. The retention time of TICS is 7 days in all tissues. TICS can be used in the detection of tumor boundaries and tumor internal structure.

Samtsov, Michael P.; Voropay, Eugene S.; Chalov, Vadim N.; Zhavrid, Edvard A.

2002-05-01

185

Photosystem II Does Not Possess a Simple Excitation Energy Funnel: Time-Resolved Fluorescence Spectroscopy Meets Theory  

PubMed Central

The experimentally obtained time-resolved fluorescence spectra of photosystem II (PS II) core complexes, purified from a thermophilic cyanobacterium Thermosynechococcus vulcanus, at 5–180 K are compared with simulations. Dynamic localization effects of excitons are treated implicitly by introducing exciton domains of strongly coupled pigments. Exciton relaxations within a domain and exciton transfers between domains are treated on the basis of Redfield theory and generalized Förster theory, respectively. The excitonic couplings between the pigments are calculated by a quantum chemical/electrostatic method (Poisson-TrEsp). Starting with previously published values, a refined set of site energies of the pigments is obtained through optimization cycles of the fits of stationary optical spectra of PS II. Satisfactorily agreement between the experimental and simulated spectra is obtained for the absorption spectrum including its temperature dependence and the linear dichroism spectrum of PS II core complexes (PS II-CC). Furthermore, the refined site energies well reproduce the temperature dependence of the time-resolved fluorescence spectrum of PS II-CC, which is characterized by the emergence of a 695 nm fluorescence peak upon cooling down to 77 K and the decrease of its relative intensity upon further cooling below 77 K. The blue shift of the fluorescence band upon cooling below 77 K is explained by the existence of two red-shifted chlorophyll pools emitting at around 685 and 695 nm. The former pool is assigned to Chl45 or Chl43 in CP43 (Chl numbering according to the nomenclature of Loll et al. Nature2005, 438, 1040) while the latter is assigned to Chl29 in CP47. The 695 nm emitting chlorophyll is suggested to attract excitations from the peripheral light-harvesting complexes and might also be involved in photoprotection.

2013-01-01

186

ALA-based fluorescent diagnosis of malignant oral lesions in the presence of bacterial porphyrin formation  

NASA Astrophysics Data System (ADS)

The aminolevulinic acid (5-ALA) -based fluorescence diagnosis has been found to be promising for an early detection and demarcation of superficial oral squamous cell carcinomas (OSCC). This method has previously demonstrated high sensitivity, however this clinical trial showed a specificity of approximately 62 %. This specificity was mainly restricted by tumor detection in the oral cavity in the presence of bacteria. After topical ALA application in the mouth of patients with previously diagnosed OSSC, red fluorescent areas were observed which did not correlate to confirm histological findings. Swabs and plaque samples were taken from 44 patients and cultivated microbiologically. Fluorescence was investigated (OMA-system) from 32 different bacteria strains found naturally in the oral cavity. After ALA incubation, 30 of 32 strains were found to synthesize fluorescent porphyrins, mainly Protoporphyrin IX. Also multiple fluorescent spectra were obtained having peak wavelengths of 636 nm and around 618 nm - 620 nm indicating synthesis of different porphyrins, such as the lipophylic Protoporphyrin IX (PpIX) and hydrophylic porphyrins (water soluble porphyrins, wsp). Of the 32 fluorescent bacterial strains, 18 produced wsp, often in combination with PpIX, and 5 produced solely wsp. These results clarify that ALA-based fluorescence diagnosis without consideration or suppression of bacteria fluorescence may lead to false-positive findings. It is necessary to suppress bacteria fluorescence with suitable antiseptics before starting the procedure. In this study, when specific antiseptic pre-treatment was performed bacterial associated fluorescence was significantly reduced.

Schleier, P.; Berndt, A.; Zinner, K.; Zenk, W.; Dietel, W.; Pfister, W.

2006-03-01

187

Determination of flumioxazin residue in food samples through a sensitive fluorescent sensor based on click chemistry.  

PubMed

A sensitive and selective fluorescent sensor for flumioxazin was designed based on the formation of strong fluorescence compound (1,2,3-triazole compounds) via the reaction of the alkynyl group in flumioxazin with 3-azido-7-hydroxycoumarin, a weak-fluorescent compound, through the Cu(+)-catalysed azide-alkyne cycloaddition (CuAAC) reaction. The fluorescence increase factor (represented by F/F0) of the system exhibited a good linear relationship with the concentrations of flumioxazin in the range of 0.25-6.0 ?g/L with a detection limit of 0.18 ?g/L (S/N=3). Also, the proposed fluorescent sensor demonstrated good selectivity for flumioxazin assay even in the presence of high concentration of other pesticides. Based on such high sensitivity and selectivity, the proposed fluorescent sensor has been applied to test the flumioxazin residue in some vegetable and water samples with satisfied results. PMID:24874382

Lu, Lijun; Yang, Linlin; Cai, Huijian; Zhang, Lan; Lin, Zhenyu; Guo, Longhua; Qiu, Bin; Chen, Guonan

2014-11-01

188

Translation on demand by a simple RNA-based thermosensor  

PubMed Central

Structured RNA regions are important gene control elements in prokaryotes and eukaryotes. Here, we show that the mRNA of a cyanobacterial heat shock gene contains a built-in thermosensor critical for photosynthetic activity under stress conditions. The exceptionally short 5?-untranslated region is comprised of a single hairpin with an internal asymmetric loop. It inhibits translation of the Synechocystis hsp17 transcript at normal growth conditions, permits translation initiation under stress conditions and shuts down Hsp17 production in the recovery phase. Point mutations that stabilized or destabilized the RNA structure deregulated reporter gene expression in vivo and ribosome binding in vitro. Introduction of such point mutations into the Synechocystis genome produced severe phenotypic defects. Reversible formation of the open and closed structure was beneficial for viability, integrity of the photosystem and oxygen evolution. Continuous production of Hsp17 was detrimental when the stress declined indicating that shutting-off heat shock protein production is an important, previously unrecognized function of RNA thermometers. We discovered a simple biosensor that strictly adjusts the cellular level of a molecular chaperone to the physiological need.

Kortmann, Jens; Sczodrok, Simon; Rinnenthal, Jorg; Schwalbe, Harald; Narberhaus, Franz

2011-01-01

189

Synthesis and properties of novel base-discriminating fluorescent (BDF) nucleosides.  

PubMed

We designed a new type of pyrene-labeled base-discrimination fluorescent (BDF) nucleosides (Py)U, (Py)C, (8Py)A and (MePy)dA, which emitted strong fluorescence only when the bases opposite the BDF base are A, G, T and C, respectively. The DNA probes containing four different BDF bases enable us to distinguish single base alterations by simply mixing with a sample solution of target DNA. PMID:17150679

Saito, Yoshio; Hanawa, Kazuo; Hayashi, Keigo; Motegi, Kaori; Okaoto, Akimitsu; Saito, Isao

2005-01-01

190

A conjugated polyelectrolyte-based fluorescence sensor for pyrophosphate.  

PubMed

A new fluorescence turn-on sensor consisting of PPE-CO(2)(-)/Cu(2+) shows high selectivity for pyrophosphate over other anions and is used to develop a real-time assay for alkaline phosphatase. PMID:17622429

Zhao, Xiaoyong; Liu, Yan; Schanze, Kirk S

2007-07-28

191

Fluorescence-based test of fiber-optic continuity  

NASA Astrophysics Data System (ADS)

There is considerable interest in the use of lasers and optical fibers for the initiation of pyrotechnics. In this application the need develops for a means of testing the continuity of the initiation fiber before initiation of the pyrotechnic. We present proof of the feasibility of an unambiguous continuity test using the fluorescence returned by the fiber from a fluorescent material in or near the pyrotechnic.

Norwood, D. P.; Vinches, C.; Anderson, J. F.; Reed, W. F.

1997-04-01

192

Fluorescence-based test of fiber-optic continuity.  

PubMed

There is considerable interest in the use of lasers and optical fibers for the initiation of pyrotechnics. In this application the need develops for a means of testing the continuity of the initiation fiber before initiation of the pyrotechnic. We present proof of the feasibility of an unambiguous continuity test using the fluorescence returned by the fiber from a fluorescent material in or near the pyrotechnic. PMID:18253241

Norwood, D P; Vinches, C; Anderson, J F; Reed, W F

1997-04-20

193

A highly selective fluorescent probe for Hg 2+ based on a rhodamine–coumarin conjugate  

Microsoft Academic Search

A fluorescent probe 1 for Hg2+ based on a rhodamine–coumarin conjugate was designed and synthesized. Probe 1 exhibits high sensitivity and selectivity for sensing Hg2+, and about a 24-fold increase in fluorescence emission intensity is observed upon binding excess Hg2+ in 50% water\\/ethanol buffered at pH 7.24. The fluorescence response to Hg2+ is attributed to the 1:1 complex formation between

Qiu-Juan Ma; Xiao-Bing Zhang; Xu-Hua Zhao; Zhen Jin; Guo-Jiang Mao; Guo-Li Shen; Ru-Qin Yu

2010-01-01

194

Fluorescence-based temperature measurement in laser-induced vapor bubbles  

Microsoft Academic Search

A fluorescence-based temperature probe (optrode) was designed to measure temperature within laser-induced vapor bubbles. The optrode consisted of a 400-micrometer optical fiber with a rhodamine B-doped polyurethane film attached to the fiber tip. The film exhibited a fluorescence decay time of 4 ns, and the measured fluorescence yield was temperature dependent in the range from 20 to 110 degrees Celsius.

Kin Foong Chan; T. Joshua Pfefer; Daniel X. Hammer; E. Duco Jansen; Martin Frenz; Ashley J. Welch

1998-01-01

195

A Colorimetric and Ratiometric Fluorescent Chemosensor for Fluoride Based on Proton Transfer  

Microsoft Academic Search

N-Phenyl-N’-(3-quinolinyl)urea (1) has been developed as a highly selective colorimetric and ratiometric fluorescent chemosensor for fluoride ion based on a\\u000a proton transfer mechanism. Evidences for the mechanism were provided by UV-vis and fluorescence titration and especially 1H and 19F NMR experiments. The sensor gave the largest ratiometric fluorescent response reported so far (Rmax\\/Rmin?=?2620) to fluoride. Taking H+ as the “recovering

Chuandong Jia; Biao Wu; Jianjun Liang; Xiaojuan Huang; Xiao-Juan Yang

2010-01-01

196

Two-color far-field fluorescence nanoscopy based on photoswitchable emitters  

Microsoft Academic Search

We demonstrate two-color far-field fluorescence microscopy with nanoscale spatial resolution based on the photoswitching of\\u000a individual fluorescent markers. By enabling, recording, and disabling the emission of the reversibly switchable fluorescent\\u000a protein rsFastLime and of the organic fluorophore cyanine5, we recorded two-color nanoscale images inside whole cells. The\\u000a position of individual emitters was determined with a typical accuracy of 20 nm, which

H. Bock; C. Geisler; C. A. Wurm; C. von Middendorff; S. Jakobs; A. Schönle; A. Egner; S. W. Hell; C. Eggeling

2007-01-01

197

A sensitive quantum dots-based "OFF-ON" fluorescent sensor for ruthenium anticancer drugs and ctDNA.  

PubMed

In this contribution, a simple and sensitive fluorescent sensor for the determination of both the three ruthenium anticancer drugs (1 to 3) and calf thymus DNA (ctDNA) was established based on the CdTe quantum dots (QDs) fluorescence "OFF-ON" mode. Under the experimental conditions, the fluorescence of CdTe QDs can be effectively quenched by ruthenium anticancer drugs because of the surface binding of these drugs on CdTe QDs and the subsequent photoinduced electron transfer (PET) process from CdTe QDs to ruthenium anticancer drugs, which render the system into fluorescence "OFF" status. The system can then be "ON" after the addition of ctDNA which brought the restoration of CdTe QDs fluorescence intensity, since ruthenium anticancer drugs broke away from the surface of CdTe QDs and inserted into double helix structure of ctDNA. The fluorescence quenching effect of the CdTe QDs-ruthenium anticancer drugs systems was mainly concentration dependent, which could be used to detect three ruthenium anticancer drugs. The limits of detection were 5.5 × 10(-8) M for ruthenium anticancer drug 1, 7.0 × 10(-8) M for ruthenium anticancer drug 2, and 7.9× 10(-8) M for ruthenium anticancer drug 3, respectively. The relative restored fluorescence intensity was directly proportional to the concentration of ctDNA in the range of 1.0 × 10(-8) M ? 3.0 × 10(-7) M, with a correlation coefficient (R) of 0.9983 and a limit of detection of 1.1 × 10(-9) M. The relative standard deviation (RSD) for 1.5 × 10(-7) M ctDNA was 1.5% (n = 5). There was almost no interference to some common chemical compounds, nucleotides, amino acids, and proteins. The proposed method was applied to the determination of ctDNA in three synthetic samples with satisfactory results. The possible reaction mechanism of CdTe QDs fluorescence "OFF-ON" was further investigated. This simple and sensitive approach possessed some potential applications in the investigation of interaction between drug molecules and DNA. PMID:24657609

Huang, Shan; Zhu, Fawei; Qiu, Hangna; Xiao, Qi; Zhou, Quan; Su, Wei; Hu, Baoqing

2014-05-01

198

Potential fluorescent chemosensor based on L-tryptophan derivative: DFT based ESIPT process.  

PubMed

The spectroscopic properties of (E)-2-(2-hydroxybenzylideneamino)-3-(1H-indol-3-yl) propanoic acid (HBDIPPA) has been studied in a series of different solvents. An excited state intramolecular proton transfer (ESIPT) process in hydroxy Schiff base has been studied using emission spectroscopy. DFT calculations on energy, HOMO-LUMO energies, MEP, dipole moment, charge distribution of the Schiff base derivative have been performed and discussed. The energy barrier for the interconversion of two rotamers is too high in the excited state than the ground state is shown by PES calculation. Positive values of laplacian ?(2)?((rc)) (2.81) and electron density ?((rc)) (0.22) are indicative of hydrogen bonds interactions. Absorption as well as fluorescence wavenumbers are correlated with Marcus and Reichardt-Dimroth solvent functions and also with Taft and Catalan solvent parameters. Schiff base HBDIPPA can be used as a new fluorescent sensor. PMID:22580140

Jayabharathi, Jayaraman; Thanikachalam, Venugopal; Vennila, Munusamy; Jayamoorthy, Karunamoorthy

2012-09-01

199

Potential fluorescent chemosensor based on L-tryptophan derivative: DFT based ESIPT process  

NASA Astrophysics Data System (ADS)

The spectroscopic properties of (E)-2-(2-hydroxybenzylideneamino)-3-(1H-indol-3-yl) propanoic acid (HBDIPPA) has been studied in a series of different solvents. An excited state intramolecular proton transfer (ESIPT) process in hydroxy Schiff base has been studied using emission spectroscopy. DFT calculations on energy, HOMO-LUMO energies, MEP, dipole moment, charge distribution of the Schiff base derivative have been performed and discussed. The energy barrier for the interconversion of two rotamers is too high in the excited state than the ground state is shown by PES calculation. Positive values of laplacian ?2?(rc) (2.81) and electron density ?(rc) (0.22) are indicative of hydrogen bonds interactions. Absorption as well as fluorescence wavenumbers are correlated with Marcus and Reichardt-Dimroth solvent functions and also with Taft and Catalan solvent parameters. Schiff base HBDIPPA can be used as a new fluorescent sensor.

Jayabharathi, Jayaraman; Thanikachalam, Venugopal; Vennila, Munusamy; Jayamoorthy, Karunamoorthy

200

Fluorescent nanodiamonds for ultrasensitive detection  

NASA Astrophysics Data System (ADS)

Fluorescent nanodiamonds (NDs) are new and emerging nanomaterials that have potential to be used as fluorescence imaging agents and also as a highly versatile platform for the controlled functionalization and delivery of a wide spectrum of therapeutic agents. We will utilize two experimental methods, TIRF, a relatively simple method based on total internal reflection fluorescence and SPRF, fluorescence enhanced by resonance coupling with surface plasmons. We estimate that the SPRF method will be 100 times sensitive than currently available similar detectors based on detectors. The ultimate goal of this research is to develop microarray platforms that could be used for sensitive, fast and inexpensive gene sequencing and protein detection.

Kimball, Joseph; Shumilov, Dmytro; Maliwa, Badri; Zerda, T. W.; Rout, Bibhu; Fudala, Rafal; Raut, Sangram; Gryczynski, Ignacy; Simanek, Eric; Borejdo, Julian; Rich, Ryan; Akopova, Irina; Gryczynski, Zygmunt

2014-03-01

201

Simple and sensitive detection method for Cobalt(II) in water using CePO4:Tb3+ nanocrystals as fluorescent probes.  

PubMed

A simple and sensitive method for detecting cobalt by synchronous fluorescence spectrometry technique with a novel fluorescence probe CePO4:Tb(3+) has been developed. CePO4:Tb(3+) nanocrystals were synthesized in aqueous solutions and characterized by transmission electron microscopy, electron diffraction pattern spectroscopy and spectrofluorometry. When ??=210 nm, the selected synchronous fluorescence is produced at 284 nm. CePO4:Tb(3+) nanocrystals were negatively charged under weakly basic conditions (pH=8.2), which can interact with Co(2+) via electrostatic interaction. Moreover, there is the spectrum overlap between the emission wavelength of CePO4:Tb(3+) NCs and the absorbance of Co(2+). So the energy transfer would occur, leading to the quenching phenomenon. The quenching equation of the system was agreed with the Stern-Volmer equation. The linear range and detection limit of Co(2+) were 5-1.8 ?M and 3.5 nM, respectively. The method is successfully applied to the quantification of Co(2+) in water samples. PMID:23416919

Chen, Hongqi; Yuan, Fei; Xu, Juan; Zhang, Yiyang; Wu, Yong; Wang, Lun

2013-04-15

202

A simple raster-based model for flood inundation simulation  

Microsoft Academic Search

In this paper the development of a new model for simulating flood inundation is outlined. The model is designed to operate with high-resolution raster Digital Elevation Models, which are becoming increasingly available for many lowland floodplain rivers and is based on what we hypothesise to be the simplest possible process representation capable of simulating dynamic flood inundation. This consists of

P. D Bates; A. P. J De Roo

2000-01-01

203

Label-free detection of adenosine based on fluorescence resonance energy transfer between fluorescent silica nanoparticles and unmodified gold nanoparticles.  

PubMed

A sensitive and convenient strategy was developed for label-free assay of adenosine. The strategy adapted the fluorescence resonance energy transfer property between Rhodamine B doped fluorescent silica nanoparticles (SiNPs) and gold nanoparticles (AuNPs) to generate signal. The different affinities of AuNPs toward the unfolded and folded aptamers were employed for the signal transfer in the system. In the presence of adenosine, the split aptamer fragments react with adenosine to form a structured complex. The folded aptamer cannot be adsorbed on the surface of AuNPs, which induces the aggregation of AuNPs under high ionic concentration conditions, and the aggregation of AuNPs leads to the decrease of the quenching ability. Therefore, the fluorescence intensity of Rhodamine B doped fluorescent SiNPs increased along with the concentration of adenosine. Because of the highly specific recognition ability of the aptamer toward adenosine and the strong quenching ability of AuNPs, the proposed strategy demonstrated good selectivity and high sensitivity for the detection of adenosine. Under the optimum conditions in the experiments, a linear range from 98nM to 100?M was obtained with a detection limit of 45nM. As this strategy is convenient, practical and sensitive, it will provide a promising potential for label-free aptamer-based protein detection. PMID:24845820

Qiang, Weibing; Liu, Haiping; Li, Wei; Chen, Xiang; Xu, Danke

2014-05-30

204

Two-color far-field fluorescence nanoscopy based on photoswitchable emitters  

NASA Astrophysics Data System (ADS)

We demonstrate two-color far-field fluorescence microscopy with nanoscale spatial resolution based on the photoswitching of individual fluorescent markers. By enabling, recording, and disabling the emission of the reversibly switchable fluorescent protein rsFastLime and of the organic fluorophore cyanine5, we recorded two-color nanoscale images inside whole cells. The position of individual emitters was determined with a typical accuracy of 20 nm, which largely constitutes the lateral resolution of the system. Photoswitching in two-color colocalization experiments represents a major step towards the application of far-field fluorescence nanoscopy to the study of (biological) samples on the macromolecular level.

Bock, H.; Geisler, C.; Wurm, C. A.; von Middendorff, C.; Jakobs, S.; Schönle, A.; Egner, A.; Hell, S. W.; Eggeling, C.

2007-07-01

205

Cytometric sorting based on the fluorescence lifetime of spectrally overlapping signals  

PubMed Central

Flow cytometry is a well-established and powerful high-throughput fluorescence measurement tool that also allows for the sorting and enrichment of subpopulations of cells expressing unique fluorescence signatures. Owing to the reliance on intensity-only signals, flow cytometry sorters cannot easily discriminate between fluorophores that spectrally overlap. In this paper we demonstrate a new method of cell sorting using a fluorescence lifetime-dependent methodology. This approach, referred to herein as phase-filtered cell sorting (PFCS), permits sorting based on the average fluorescence lifetime of a fluorophore by separating fluorescence signals from species that emit differing average fluorescence lifetimes. Using lifetime-dependent hardware, cells and microspheres labeled with fluorophores were sorted with purities up to 90%. PFCS is a practical approach for separating populations of cells that are stained with spectrally overlapping fluorophores or that have interfering autofluorescence signals.

Cao, Ruofan; Pankayatselvan, Varayini; Houston, Jessica P.

2013-01-01

206

Water-soluble conjugated polymer as a platform for adenosine deaminase sensing based on fluorescence resonance energy transfer technique.  

PubMed

We report a new biosensor for adenosine deaminase (ADA) sensing based on water-soluble conjugated poly(9,9-bis(6'-N,N,N-trimethylammonium)hexyl)fluorine phenylene (PFP) and fluorescence resonance energy transfer technique. In this biosensor, PFP, DNAc-FI labeled with fluorescein (FAM), and ethidium bromide (EB) were used as the fluorescence energy donor, resonance gate, and the final fluorescence energy acceptor, respectively. In the absence of ADA, the adenosine aptamer forms a hairpin-like conformation with adenosine, which is far from its complementary single-stranded DNA (DNAc-FI). When PFP is excited at 380 nm, fluorescein emits strong green fluorescence via one-step FRET while EB has no fluorescence. After addition of ADA, adenosine is hydrolyzed to inosine and then double-stranded DNA (dsDNA) is formed between the aptamer and DNAc-FI, followed by EB intercalating into dsDNA. Once PFP is excited, EB will emit strong yellow fluorescence after two-step FRET from PFP to fluorescein and from fluorescein to EB. The sensitive ADA detection then is realized with a low detection limit of 0.5 U/L by measuring the FRET ratio of EB to fluorescein. Most importantly, the assay is accomplished homogeneously in 25 min without further treatments, which is much more simple and rapid than that reported in literature. Hence, this method demonstrates the sensitive, cost-effective, and rapid detection of ADA activity. It also opens an opportunity for designing promising sensors for other enzymes. PMID:24893272

Wang, Chun; Tang, Yanli; Liu, Yue; Guo, Yang

2014-07-01

207

An improved respiratory syncytial virus neutralization assay based on the detection of green fluorescent protein expression and automated plaque counting  

PubMed Central

Background Virus neutralizing antibodies against respiratory syncytial virus (RSV) are considered important correlates of protection for vaccine evaluation. The established plaque reduction assay is time consuming, labor intensive and highly variable. Methods Here, a neutralization assay based on a modified RSV strain expressing the green fluorescent protein in combination with automated detection and quantification of plaques is described. Results The fluorescence plaque reduction assay in microplate format requires only two days to complete and is simple and reproducible. A good correlation between visual and automated counting methods to determine RSV neutralizing serum antibody titers was observed. Conclusions The developed virus neutralization assay is suitable for high-throughput testing and can be used for both animal studies and (large scale) vaccine clinical trials.

2012-01-01

208

Iron complex-based fluorescent probes for intracellular hydrogen peroxide detection.  

PubMed

A metal-based fluorescent probe for H2O2, named MBFh2, releases a highly fluorescent resorufin in the seconds time scale even in the presence of 5 ?M H2O2. The use of MBFh2 enabled the visualization of intracellular H2O2 that was generated after stimulation of the epidermal growth factor. PMID:24000350

Hitomi, Yutaka; Takeyasu, Toshiyuki; Kodera, Masahito

2013-11-01

209

A novel fiber optic biosensor for nitric oxide determination based on vicinal diaminobenzozcridine fluorescent probe  

Microsoft Academic Search

A novel fiber optic biosensor for the determination of nitric oxide based on vicinal diaminobenzozcridine (VDABA) fluorescent probe was designed and fabricated. The reaction conditions between VDABA and NO, which include concentration of VDABA, temperature and pH, were studied in-depth. The sensitivity of VDABA for NO detection under the optimum conditions and its optical properties were also investigated. The fluorescence

Liyun Ding; Lanfen Huang; Jun Huang; Yunming Zhong; Dian Fan

2010-01-01

210

Polyoxometalate-based inorganic-organic hybrid film structure with reversible electroswitchable fluorescence property.  

PubMed

A novel inorganic-organic hybrid film structure based on polyoxometalate and conventional organic dye has been fabricated, whose fluorescence can be reversibly switched using the electrochromic component to activate or suppress the related fluorescence quenching mechanism upon applying reduction or oxidation potentials of polyoxometalates. PMID:22245959

Jin, Lihua; Fang, Youxing; Hu, Peng; Zhai, Yanling; Wang, Erkang; Dong, Shaojun

2012-02-18

211

Micro-fluidic-based optical detection platform for characterizing fluorescing objects with integrated wavelength detection  

Microsoft Academic Search

This presentation will give a brief overview on on-the-flow analyte detection based on native fluorescence spectroscopy. This is a very promising approach that does not require specific binding or tagging of the analyte. However, the variety of cells is large compared to the number of basic molecular building blocks. Therefore, the fluorescence spectra of different species are often very similar,

Peter Kiesel; Markus Beck; Michael Bassler; Noble Johnson

2008-01-01

212

Fluorescence photoswitching based on a photochromic pKa change in an aqueous solution.  

PubMed

Reversible fluorescence photoswitching of RSA-AZO dyad 1 was clearly demonstrated in an acidic aqueous solution. The fluorescence photoswitching mechanism is based on the reversible ring opening/closing reactions of the RSA unit induced by a photochromic pK(a) change along with the photoisomerization of the AZO unit. PMID:23023587

Fukaminato, Tuyoshi; Tateyama, Emi; Tamaoki, Nobuyuki

2012-11-14

213

Fluorescent enantioselective receptor for S-mandelate anion based on cholic acid  

Microsoft Academic Search

A chiral fluorescent receptor 1 based on cholic acid was designed and synthesized. The enantioselective recognition ability of 1 to mandelate anion was studied by the fluorescence in CH3CN and a 1H NMR spectroscopic method. The results indicate that 1 exhibited a good enantioselectivity to the enantiomer of the mandelate anion in CH3CN.

Shun Ying Liu; Kin Yu Law; Yong Bing He; Wing Hong Chan

2006-01-01

214

A chromenoquinoline-based fluorescent off-on thiol probe for bioimaging.  

PubMed

A new chromenoquinoline-based fluorescent off-on thiol probe 2 is reported. In aqueous buffer solutions at physiological pH, the probe exhibited 223-fold enhancement in fluorescence intensity by a Michael addition of cysteine to the maleimide appended to a chromenoquinoline. Cell permeability and live cell imaging of thiols are also demonstrated. PMID:22301487

Kand, Dnyaneshwar; Kalle, Arunasree Marasanapalli; Varma, Sreejith Jayasree; Talukdar, Pinaki

2012-03-11

215

A boronate-based fluorescent probe for the selective detection of cellular peroxynitrite.  

PubMed

A boronate-based fluorescent probe for the selective monitoring of intracellular peroxynitrite has been developed. The probe takes advantage of the fast reaction of an arylboronate group with peroxynitrite, yielding a corresponding phenol that undergoes spontaneous subsequent reactions to produce a strongly fluorescent product associated with a large turn-on signal. PMID:25002151

Kim, Jiyoung; Park, Jeesook; Lee, Hawon; Choi, Yongdoo; Kim, Youngmi

2014-07-22

216

Simple laser-based pipeline corrosion assessment system  

SciTech Connect

The article focuses on development and use of a simpler laser-based system for accurately and efficiently measuring and assessing corrosion damage on the external surface of an exposed pipeline. The system uses a laser-based range sensor, which relies on optical spray, sensor movement, and the principal of triangulation to construct a three-dimensional measurement. Baseline subtraction, where a polynomial curve-fit is used to approximate the ideal pipe profile above the corroded area, is used. Future profiles are subtracted from the ideal profile, and when differences are significant, corrosion depth measurements are made by constructing normal vectors at points along the ideal profile. The use of such a system for accurately mapping corrosion damage allows more accurate assessments, thereby reducing the number of unnecessary repairs and cut outs, and reduces the risk of non-conservative assessments. The use of this system also results in reduced labor costs associated with mapping corrosion damage and allows the assessment process to be carried out over a much shorter period of time. The system can also be used to develop an accurate correlation between inline inspection (ILI) results and corrosion geometry during the first few excavations following ILI, resulting in the need to excavate fewer areas.

Bruce, W.A.; Yapp, D.; Barborak, D.M. [Edison Welding Inst., Columbus, OH (United States); Fingerhut, M.P.; Kania, R. [RTD Quality Services, Inc., Edmonton, Alberta (Canada)

1997-03-01

217

Generation of circularly permuted fluorescent-protein-based indicators for in vitro and in vivo detection of citrate.  

PubMed

Indicators for citrate, particularly those applicable to its in vivo detection and quantitation, have attracted much interest in both biochemical studies and industrial applications since citrate is a key metabolic intermediate playing important roles in living cells. We generated novel fluorescence indicators for citrate by fusing the circularly permuted fluorescent protein (cpFP) and the periplasmic domain of the bacterial histidine kinase CitA, which can bind to citrate with high specificity. The ratiometric fluorescent signal change was observed with one of these cpFP-based indicators, named CF98: upon addition of citrate, the excitation peak at 504 nm increased proportionally to the decrease in the peak at 413 nm, suitable for build-in quantitative estimation of the binding compound. We confirmed that CF98 can be used for detecting citrate in vitro at millimolar levels in the range of 0.1 to 50 mM with high selectivity; even in the presence of other organic acids such as isocitrate and malate, the fluorescence intensity of CF98 remains unaffected. We finally demonstrated the in vivo applicability of CF98 to estimation of the intracellular citrate concentration in Escherichia coli co-expressing the genes encoding CF98 and the citrate carrier CitT. The novel indicator CF98 can be a specific and simple detection tool for citrate in vitro and a non-invasive tool for real-time estimation of intracellular concentrations of the compound in vivo. PMID:23717638

Honda, Yuki; Kirimura, Kohtaro

2013-01-01

218

Generation of Circularly Permuted Fluorescent-Protein-Based Indicators for In Vitro and In Vivo Detection of Citrate  

PubMed Central

Indicators for citrate, particularly those applicable to its in vivo detection and quantitation, have attracted much interest in both biochemical studies and industrial applications since citrate is a key metabolic intermediate playing important roles in living cells. We generated novel fluorescence indicators for citrate by fusing the circularly permuted fluorescent protein (cpFP) and the periplasmic domain of the bacterial histidine kinase CitA, which can bind to citrate with high specificity. The ratiometric fluorescent signal change was observed with one of these cpFP-based indicators, named CF98: upon addition of citrate, the excitation peak at 504 nm increased proportionally to the decrease in the peak at 413 nm, suitable for build-in quantitative estimation of the binding compound. We confirmed that CF98 can be used for detecting citrate in vitro at millimolar levels in the range of 0.1 to 50 mM with high selectivity; even in the presence of other organic acids such as isocitrate and malate, the fluorescence intensity of CF98 remains unaffected. We finally demonstrated the in vivo applicability of CF98 to estimation of the intracellular citrate concentration in Escherichia coli co-expressing the genes encoding CF98 and the citrate carrier CitT. The novel indicator CF98 can be a specific and simple detection tool for citrate in vitro and a non-invasive tool for real-time estimation of intracellular concentrations of the compound in vivo.

Honda, Yuki; Kirimura, Kohtaro

2013-01-01

219

Simple communication using a SSVEP-based BCI  

NASA Astrophysics Data System (ADS)

Majority of Brain-Computer Interface (BCI) for communication purposes are speller, i.e., the user has to select letter by letter. In this work, is proposed a different approach where the user can select words from a word set designed in order to answer a wide range of questions. The word selection process is commanded by a Steady-state visual evoked potential (SSVEP) based-BCI that allows selecting a word in an average time of 26 s with accuracies of 92% on average. This BCI is focus in the first stages on rehabilitation or even in first moments of some diseases (such as stroke), when the person is eager to communicate with family and doctors.

Sanchez, Guillermo; Diez, Pablo F.; Avila, Enrique; Laciar Leber, Eric

2011-12-01

220

Fluorescence-Based Sensor for Monitoring Activation of Lunar Dust  

NASA Technical Reports Server (NTRS)

This sensor unit is designed to determine the level of activation of lunar dust or simulant particles using a fluorescent technique. Activation of the surface of a lunar soil sample (for instance, through grinding) should produce a freshly fractured surface. When these reactive surfaces interact with oxygen and water, they produce hydroxyl radicals. These radicals will react with a terephthalate diluted in the aqueous medium to form 2-hydroxyterephthalate. The fluorescence produced by 2-hydroxyterephthalate provides qualitative proof of the activation of the sample. Using a calibration curve produced by synthesized 2-hydroxyterephthalate, the amount of hydroxyl radicals produced as a function of sample concentration can also be determined.

Wallace, William T.; Jeevarajan, Antony S.

2012-01-01

221

SIL-based confocal fluorescence microscope for investigating individual nanostructures  

NASA Astrophysics Data System (ADS)

We developed a fluorescence confocal microscope equipped with a hemispherical solid immersion lens (SIL) and apply it to study the optical properties of light-harvesting complexes. We demonstrate that the collection efficiency of the SIL-equipped microscope is significantly improved, as is the spatial resolution, which reaches 600 nm. This experimental setup is suitable for detailed studies of physical phenomena in hybrid nanostructures. In particular, we compare the results of fluorescence intensity measurements for a light-harvesting peridinin-chlorophyll-protein (PCP) complex with and without the SIL.

Krajnik, Bartosz; Schulte, Tim; Pi?tkowski, Dawid; Czechowski, Nikodem; Hofmann, Eckhard; Mackowski, Sebastian

2011-04-01

222

Ruthenium(II) complex-based fluorescent sensor for peroxynitrite  

NASA Astrophysics Data System (ADS)

We have developed a new ruthenium complex, Ru(bpy)2[4-(2,2'-bipyridin-4-yloxy)phenol]Cl2 (RuL), as a fluorescent sensor to detect peroxynitrite (ONOO-). The results showed that the addition of ONOO- to the aqueous solution of RuL would result in distinct fluorescence quenching at 600 nm. RuL exhibits a good selectivity for ONOO- over other reactive oxygen species (ROS) and reactive nitrite species (RNS), and the reaction time is less than 1.5 s. The sensing mechanism is proposed as the oxidative O-dealkylation reaction.

Ma, Jingjin; Wu, Jiasheng; Liu, Weimin; Wang, Pengfei; Fan, Zhiyuan

223

A fluorescence polarization based assay for glucose sensing  

NASA Astrophysics Data System (ADS)

A fluorescence polarization (FP) assay was developed to determine concentrations of glucose using concanavalin A (ConA) and fluorescently-labeled dextran. Predictive FP responses to glucose were elicited for different assay configurations using mathematical modeling and displayed herein. Using 4 kDa FITC-dextran, we predicted a change of 0.120 P units from 0 mg/dL glucose to 500 mg/dL. This shows the potential that a homogenous, reproducible FP assay can be engineered to measure glucose concentrations using tetrameric ConA and 4k kDa FITC-dextran.

Cummins, Brian M.; Coté, Gerard L.

2012-02-01

224

A ratiometric fluorescent chemosensor for Al(3+) in aqueous solution based on aggregation-induced emission and its application in live-cell imaging.  

PubMed

A ratiometric fluorescent chemosensor 1 was developed for the detection of Al(3+) in aqueous solution based on aggregation-induced emmision (AIE). The chemosensor showed the fluorescence of its aggregated state and Al(3+)-chelated soluble state in the absence and in the presence of Al(3+), respectively, and resulted in a fluorescence ratio (I461/I537) response to Al(3+) in neutral aqueous solution at a detection limit as low as 0.29?molL(-1). The method was also highly selective to Al(3+) over other physiological relevant metal ions investigated in this study. Taking advantage of its AIE characteristics, the chemosensor was successfully applied on test papers for simple and rapid detection of Al(3+). Moreover, the application of 1 for the imaging of Al(3+) in living cells by ratiometric fluorescence changes was also achieved. PMID:24856403

Peng, Lu; Zhou, Zhaojuan; Wang, Xiaoyan; Wei, Ruirui; Li, Kai; Xiang, Yu; Tong, Aijun

2014-06-01

225

A fluorescent sensor to detect sodium dodecyl sulfate based on the glutathione-stabilized gold nanoclusters/poly diallyldimethylammonium chloride system.  

PubMed

A simple method for the detection of sodium dodecyl sulfate (SDS) was developed based on glutathione-stabilized gold nanoclusters (GSH-AuNCs) and poly(diallyldimethylammonium)chloride (PDDA) enhanced fluorescent system. Fluorescent Au NCs were synthesized by a one-step approach employing GSH as reducing/protecting reagent. The electrostatic group repulsions between GSH-Au NCs and PDDA resulted in strong fluorescence enhancement from the GSH-Au NCs. Moreover, the addition of SDS was able to cause a significant fluorescence recovery due to the strong affinity of PDDA and SDS. Thus the SDS can be detected. Under optimized conditions, the linear response to detect SDS ranges from 0.2 to 12 µg mL(-1) with a detection limit of 0.02 µg mL(-1). PMID:24862984

Zheng, Chun-Lan; Ji, Zhong-Xiang; Zhang, Jian; Ding, Shou-Nian

2014-07-01

226

A simple raster-based model for flood inundation simulation  

NASA Astrophysics Data System (ADS)

In this paper the development of a new model for simulating flood inundation is outlined. The model is designed to operate with high-resolution raster Digital Elevation Models, which are becoming increasingly available for many lowland floodplain rivers and is based on what we hypothesise to be the simplest possible process representation capable of simulating dynamic flood inundation. This consists of a one-dimensional kinematic wave approximation for channel flow solved using an explicit finite difference scheme and a two-dimensional diffusion wave representation of floodplain flow. The model is applied to a 35 km reach of the River Meuse in The Netherlands using only published data sources and used to simulate a large flood event that occurred in January 1995. This event was chosen as air photo and Synthetic Aperture Radar (SAR) data for flood inundation extent are available to enable rigorous validation of the developed model. 100, 50 and 25 m resolution models were constructed and compared to two other inundation prediction techniques: a planar approximation to the free surface and a relatively coarse resolution two-dimensional finite element scheme. The model developed in this paper outperforms both the simpler and more complex process representations, with the best fit simulation correctly predicting 81.9% of inundated and non-inundated areas. This compares with 69.5% for the best fit planar surface and 63.8% for the best fit finite element code. However, when applied solely to the 7 km of river below the upstream gauging station at Borgharen the planar model performs almost as well (83.7% correct) as the raster model (85.5% correct). This is due to the proximity of the gauge, which acts as a control point for construction of the planar surface and the fact that here low-lying areas of the floodplain are hydraulically connected to the channel. Importantly though it is impossible to generalise such application rules and thus we cannot specify a priori where the planar approximation will work. Simulations also indicate that, for this event at least, dynamic effects are relatively unimportant for prediction of peak inundation. Lastly, consideration of errors in typically available gauging station and inundation extent data shows the raster-based model to be close to the current prediction limit for this class of problem.

Bates, P. D.; De Roo, A. P. J.

2000-09-01

227

Application of fluorescence-based semi-automated allelotyping to the molecular characterization of tumors  

SciTech Connect

In cancer genetics, identifying loss of heterozygosity (LOH) defines candidate regions which warrant further analyses to determine the presence of tumor suppressor genes. In addition, demonstrating LOH has potential utility for improving the pathologic classification of tumors. Molecular methods that improve the efficiency and accuracy of LOH studies will be helpful in both clinical and research applications. Here we demonstrate a fluorescence-based semi-automated alleotyping method for studies of LOH in cancer, using gliomas as an example. Gliomas are tumors arising from neuroglia, the supporting tissue intermingled with essential elements of the brain and spinal cord. Since this method utilizes PCR-based highly polymorphic simple sequence repeat markers, it is suitable for small and archival tumor specimens. We collected tumor tissue from a variety of gliomas, and DNA was extracted. White blood cells from the same individuals served as a source of {open_quotes}control{close_quotes} DNA. We PCR amplified markers from tumor and genomic DNA to detect molecular alterations in six people. Simultaneous analysis of 14 loci near gene candidates on chromosomes 5, 7, 9, 10, 11, and 22, were evaluated. Strikingly, in most cases there was allelic loss in brain tumor compared to genomic DNA for at least one of these loci. In addition, alleles of lesser intensity were also shown at a few loci of the tumor DNA, suggesting possible genetic instability. We conclude from these data that fluorescent semi-automated allelotyping is a quantitative and efficient process for determining and analyzing LOH in gliomas, and possibly other tumors. These methods will facilitate the identification of candidate loci critical in the development and progression of tumors.

Jedlicka, A.E.; DiSilvestre, D.; Holroyd, K.J. [Johns Hopkins Medical Institutions, Baltimore, MD (United States)] [and others

1994-09-01

228

Beer's-law-based, simple spectral model for direct normal and diffuse horizontal irradiance  

Microsoft Academic Search

A spectral model for cloudless days that uses simple mathematical expressions and tabulated lock up tables to generate direct normal and diffuse horizontal irradiance is presented. The model is based on modifications to previously published simple models and comparisons with rigorous radiative transfer codes. This model is expected to be more accurate and to be applicable to a broader range

R. E. Bird

1982-01-01

229

A simple model for thermal conductivity of carbon nanotube-based composites  

Microsoft Academic Search

A quite simple formula for the thermal conductivity enhancement in carbon nanotube composites is presented based on a conventional model. This simple formula predicts much higher thermal conductivity enhancement even in the dilute case of the carbon nanotubes, due to ultrahigh thermal conductivity and aspect ratio of the carbon nanotubes. By applying this model to nanotube suspensions recently reported in

C.-W. Nan; Z. Shi; Y. Lin

2003-01-01

230

A new Schiff base fluorescent probe for imaging Cu2+ in living cells  

NASA Astrophysics Data System (ADS)

A novel probe based on ferrocenyl-1,3,4-thiadiazol-containing Schiff base was synthesized by the reaction of 5-ferrocenyl-1,3,4-thiadiazol-2-amine and 4-(diethylamino)salicylaldehyde, and characterized by IR, NMR, HRMS and X-ray analysis. UV-vis spectral and fluorescence property of the probe were investigated. The probe can be used to colorimetric sensitive and selective fluorescent recognition of Cu2+ in buffer solution. Moreover, the probe can detect Cu2+ by electrochemical method. Additionally, the Schiff base was successfully used as a selective and sensitive fluorescent probe for monitoring Cu2+ ions in living cells.

Ye, Hui; Ge, Fei; Zhou, Yi-Ming; Liu, Jin-Ting; Zhao, Bao-Xiang

2013-08-01

231

Fluorescence thermometer based on photoluminescence imaging of Ti doped sapphire  

Microsoft Academic Search

Photoluminescence (PL) images from Ti doped sapphire (Ti doped Al2O3) crystals are observed for 2-dimensional fluorescence thermometer applications. Red colored bright PL images can be observed clearly from Ti doped sapphire sensor using a CCD camera under blue LED illumination. Intensity of red signal of the PL image decreases linearly with temperature of the sensor. Ti doped sapphire sensor is

Toru Katsumata; Takashi Honda; Megumi Watabiki; Hiroaki Aizawa; Koichi Otsubo; Shuji Komuro

2008-01-01

232

Fluorescence Thermometer Based on 2Dimensional Photoluminescence Imaging  

Microsoft Academic Search

Two-dimensional photoluminescence (PL) image from sensor material is evaluated for fluorescence thermometer application. Two dimensional PL image is observed using CCD video camera under blue and\\/or UV LED illuminations. Red colored PL image can be observed from ruby sensor under illumination of blue LED. Brightness of red signal of PL image from ruby sensor varies linearly with temperature from 20

T. Katsumata; Y. Kano; C. Nakayama; S. Harako; H. Aizawa; S. Komuro

2008-01-01

233

Magnetite nanoparticles for biosensor model based on bacteria fluorescence  

Microsoft Academic Search

Fluorescence emission of pyoverdine - the siderophore synthesized by iron scavenger bacteria - was studied using in vitro cultures of Pseudomonas aeruginosa with the aim to design a biosensor system for liquid sample iron loading. Diluted suspensions of colloidal magnetite nanoparticles were supplied in the culture medium (10 microl\\/l and 100 microl\\/l) to simulate magnetic loading with iron oxides of

A. Poita; D.-E. Creanga; A. Airinei; P. Tupu; C. Goiceanu; O. Avadanei

2009-01-01

234

DNA origami-based standards for quantitative fluorescence microscopy.  

PubMed

Validating and testing a fluorescence microscope or a microscopy method requires defined samples that can be used as standards. DNA origami is a new tool that provides a framework to place defined numbers of small molecules such as fluorescent dyes or proteins in a programmed geometry with nanometer precision. The flexibility and versatility in the design of DNA origami microscopy standards makes them ideally suited for the broad variety of emerging super-resolution microscopy methods. As DNA origami structures are durable and portable, they can become a universally available specimen to check the everyday functionality of a microscope. The standards are immobilized on a glass slide, and they can be imaged without further preparation and can be stored for up to 6 months. We describe a detailed protocol for the design, production and use of DNA origami microscopy standards, and we introduce a DNA origami rectangle, bundles and a nanopillar as fluorescent nanoscopic rulers. The protocol provides procedures for the design and realization of fluorescent marks on DNA origami structures, their production and purification, quality control, handling, immobilization, measurement and data analysis. The procedure can be completed in 1-2 d. PMID:24833175

Schmied, Jürgen J; Raab, Mario; Forthmann, Carsten; Pibiri, Enrico; Wünsch, Bettina; Dammeyer, Thorben; Tinnefeld, Philip

2014-06-01

235

Fluorescence switch of dye-infiltrated SiO2 inverse opal based on acid-base vapors or light  

NASA Astrophysics Data System (ADS)

The acid-base vapors/light double responsive dye-infiltrated SiO2 inverse opal photonic crystals (PCs) were fabricated by sacrificial template method and a subsequent infiltration of spiropyran derivative dye molecules. The fluorescence of ring-open dye molecules infiltrated in PCs can be switched on/off based on different fluorescence properties of spiropyran dye under stimuli of acid-base vapors or light, when PCs with suitable stopband were selected. The fluorescence switch behavior based on PCs has potential applications in data storage, color displays, chemical and biological sensors.

Zhang, Y. Q.; Wang, J. X.; Shang, Y. L.; Song, Y. L.; Jiang, L.

2011-03-01

236

Simple fiber-optic-based interface to facilitate spectroscopic measurements in supercritical solvents  

SciTech Connect

A new fiber-optic-based interface is described to facilitate fluorescence measurements in supercritical solvents. Steady-state and time-resolved measurements are possible, and assembly/disassembly is significantly easier compared to that required for traditional high-pressure optical cell designs. 9 refs., 6 figs., 1 tab.

Zagrobelny, J.; Ming Li; Run Wang; Betts, T.A.; Bright, F.V. (State Univ. of New York, Buffalo (United States))

1992-12-01

237

Phenothiazine-based oligomers as novel fluorescence probes for detecting vapor-phase nitro compounds.  

PubMed

To meet the need for rapid and low-cost chemical sensing of explosive, new fluorescence chemosensors based on oligophenothiazines for probing vapor-phase nitro compounds have been developed. The phenothiazine-based trimer P3 and pentamer P5 have been synthesized via Heck and Wittig reactions by convergent approach. It was found that they can detect the vapors of nitro compounds, including p-nitrotoluene (p-NT), 2,4-dinitrotoluene (DNT), 2,4,6-trinitrotoluene (TNT) with good sensitivity and reversibility. And the sensor of P3 film gave a linear fluorescence quenching response to 7-800 ppb TNT with the detection limit of 4 ppb. For DNT vapor, a linear working range of the sensor was 2-24 ppm with the detection limit of 40 ppb. Meanwhile, the interferents, including common organic solvents, p-nitrophenol and 2,4-dinitrophenylhydrazine cannot lead to obvious fluorescence quenching, meaning that the film based on oligophenothiazines exhibited good specificity of fluorescence response to explosive. Based on the fluorescence lifetime and UV-vis absorption measurements, we suggested that the fluorescence quenching of oligophenothiazine-based films exposed to the vapors of nitro compounds was due to the formation of non-fluorescent charge-transfer complex between oligophenothiazine and nitro compounds. PMID:20875600

Zhang, Xiaofei; Qiu, Xianping; Lu, Ran; Zhou, Huipeng; Xue, Pengchong; Liu, Xingliang

2010-10-15

238

Rapid and sensitive detection of ?-agonists using a portable fluorescence biosensor based on fluorescent nanosilica and a lateral flow test strip.  

PubMed

A portable fluorescence biosensor with rapid and ultrasensitive response for Clenbuterol (CL) has been built up with fluorescent nanosilica and a lateral flow test strip. Quantitative detection of CL was realized by recording the fluorescence intensity of fluorescent nanosilica captured on the test line. The sensing results indicated that the sensitivity of the fluorescent nanosilica-based strip was better than that of conventional colloidal gold-based strips. The visual limit of detection of the strip for qualitative detection was 0.1 ng/mL while the LOD for quantitative detection could down to 0.037 ng/mL by using fluorescence biosensor. The recoveries of test samples were from 89.3% to 97.7%. The assay time for CL detection was less than 8 min, suitable for rapid testing on-site. PMID:23835218

Song, Chunmei; Zhi, Aimin; Liu, Qingtang; Yang, Jifei; Jia, Guochao; Shervin, Jahanian; Tang, Liang; Hu, Xiaofei; Deng, Ruiguang; Xu, Chuanlai; Zhang, Gaiping

2013-12-15

239

Convenient and selective “off-on” detection nitric oxide in solution and thin film with quinoline based fluorescence sensor  

NASA Astrophysics Data System (ADS)

Quinoline based fluorescence sensor (1) was synthesized and characterized with mass spectra (MS), 1H nuclear magnetic resonance (1H NMR) spectrometer, elemental analyses, and infrared (IR) spectra. Following fluorescence experiments demonstrate 1 can coordinate with copper ions, and lead to fluorescence completely quenched. The 1-copper complex was used as a “turn-on” fluorescence biosensor to convenient and highly effective detect nitric oxide (NO) over other radicals in solution and PCL-based thin film. The finding would enable the quinoline based fluorescence probe to be an “off-on” convenient NO fluorescence probe.

Yu, Miao; Wang, Wei; Zhang, Ning

240

Design strategy for photoinduced electron transfer-based small-molecule fluorescent probes of biomacromolecules.  

PubMed

As the cardinal support of innumerable biological processes, biomacromolecules such as proteins, nucleic acids and polysaccharides are of importance to living systems. The key to understanding biological processes is to realize the role of these biomacromolecules in thte localization, distribution, conformation and interaction with other molecules. With the current development and adaptation of fluorescent technologies in biomedical and pharmaceutical fields, the fluorescence imaging (FLI) approach of using small-molecule fluorescent probes is becoming an up-to-the-minute method for the detection and monitoring of these imperative biomolecules in life sciences. However, conventional small-molecule fluorescent probes may provide undesirable results because of their intrinsic deficiencies such as low signal-to-noise ratio (SNR) and false-positive errors. Recently, small-molecule fluorescent probes with a photoinduced electron transfer (PET) "on/off" switch for biomacromolecules have been thoroughly considered. When recognized by the biomacromolecules, these probes turn on/off the PET switch and change the fluorescence intensity to present a high SNR result. It should be emphasized that these PET-based fluorescent probes could be advantageous for understanding the pathogenesis of various diseases caused by abnormal expression of biomacromolecules. The discussion of this successful strategy involved in this review will be a valuable guide for the further development of new PET-based small-molecule fluorescent probes for biomacromolecules. PMID:24755654

Zhang, Wei; Ma, Zhao; Du, Lupei; Li, Minyong

2014-05-01

241

Fluorescence resonance energy transfer-based molecular logic circuit using a DNA scaffold  

NASA Astrophysics Data System (ADS)

This paper presents a method of information processing using biomolecular input signals and fluorescence resonance energy transfer (FRET) signaling constructed on a DNA scaffold. Logic operations are achieved by encoding molecular inputs into an arrangement of fluorescence dyes using simple DNA reactions and by evaluating a logic expression using local photonic signaling that is much faster than DNA reactions. Experimental results verify the operation of a complete set of Boolean logic functions (AND, OR, NOT) and combinational logic operations using a FRET-signal cascade.

Nishimura, Takahiro; Ogura, Yusuke; Tanida, Jun

2012-12-01

242

Time-domain imaging with quench-based fluorescent contrast agents  

NASA Astrophysics Data System (ADS)

Quench-based probes utilize unique characteristics of fluorescence resonance energy transfer (FRET) to enhance contrast upon de-quenching. This mechanism has been used in a variety of molecular probes for imaging of cancer related enzyme activity such as matrix metalloproteinases, cathepsins and caspases. While non-fluorescent upon administration, fluorescence can be restored by separation of donor and acceptor, resulting in higher intensity in the presence of activator. Along with decreased quantum yield, FRET also results in altered fluorescence lifetime. Time-domain imaging can further enhance contrast and information yield from quench-based probes. We present in vivo time-domain imaging for detecting activation of quench-based probes. Quench-based probes utilize unique characteristics of fluorescence resonance energy transfer (FRET) to enhance contrast upon de-quenching. This mechanism has been used in a variety of molecular probes for imaging of cancer related enzyme activity such as matrix metalloproteinases, cathepsins and caspases. While non-fluorescent upon administration, fluorescence can be restored by separation of donor and acceptor, resulting in higher intensity in the presence of activator. Along with decreased quantum yield, FRET also results in altered fluorescence lifetime. Time-domain imaging can further enhance contrast and information yield from quench-based probes. We present in vivo time-domain imaging for detecting activation of quench-based probes. Time-domain diffuse optical imaging was performed to assess the FRET and quenching in living mice with orthotopic breast cancer. Tumor contrast enhancement was accompanied by increased fluorescence lifetime after administration of quenched probes selective for matrix metalloproteinases while no significant change was observed for non-quenched probes for integrin receptors. These results demonstrate the utility of timedomain imaging for detection of cancer-related enzyme activity in vivo.

Akers, Walter J.; Solomon, Metasebya; Sudlow, Gail P.; Berezin, Mikhail; Achilefu, Samuel

2012-02-01

243

Development of a new detection technique for fluorescence lifetime-based chemical/biological sensor arrays monitoring: dual closed-loop optoelectronic auto-oscillatory detection circuit  

NASA Astrophysics Data System (ADS)

We present a new detection instrument for chemical/biological fluorescence lifetime-based sensors. The instrument comprises a primary, closed loop with a secondary loop controlling a variable phase delay within the primary loop. The primary loop consists of a fluorescence excitation light source, a fiber-optic delay line (with a gap for placement of a fluorescent sensor), an electronic phase shifter, a photo-detector, and a resonance-type RF amplifier. The secondary loop consists of a long-wavelength-pass optical filter, multimode fiber, a PMT, and an electronic phase detector (which is connected to the phase shifter of the primary loop). The system exhibits self-oscillations in the form of RF sinusoidal intensity modulation with frequency dependent on the fluorescence lifetime. Since the primary loop does not contain an optical filter, it is easier to obtain self-oscillations (compared to single loop systems). The feedback also improves the stability of the detection platform. The detection system is simple, inexpensive, and scalable for sensor array purposes. We demonstrate the use of a cost-effective, multi-channel, computer-algorithm-based frequency counter with this new system. We illustrate the detection capabilities of this detection system with the pH-sensitive, fluorescent probe carboxy seminaphthofluorescein (SNAFL-2) and an immunosensor based on fluorescence resonance energy transfer.

Rabinovich, Emmanuil M.; Svimonishvili, Tengiz; O'Brien, Michael J.; Brueck, Steven R.; Buranda, Tione; Sklar, Larry A.; Lopez, Gabriel P.

2002-05-01

244

A seminaphthofluorescein-based fluorescent chemodosimeter for the highly selective detection of cysteine†  

PubMed Central

A fluorescent chemodosimeter for cysteine detection was developed based on a tandem conjugate addition and intramolecular cyclization reaction. The method exhibited an excellent selectivity for cysteine over other biothiols such as homocysteine and glutathione.

Guo, Yixing

2012-01-01

245

Novel highly emissive H-aggregates with aggregate fluorescence change in a phenylbenzoxazole-based system.  

PubMed

Fibrous nanoaggregates of a new benzoxazole-based derivative have been reported. This derivative exhibits not only H-aggregates but also strong yellow fluorescence, which is different from the traditional understanding of H-aggregates. PMID:24963609

Wang, Lianke; Shen, Yanfang; Yang, Mingdi; Zhang, Xiuzhen; Xu, Weinan; Zhu, Qiuju; Wu, Jieying; Tian, Yupeng; Zhou, Hongping

2014-08-14

246

A sensitivity tuneable tetraphenylethene-based fluorescent probe for directly indicating the concentration of hydrogen sulfide.  

PubMed

A novel tetraphenylethene-based fluorescent H2S probe was designed and synthesized, which exhibited high selectivity and tuneable sensitivity, making direct indication of H2S concentration in blood and unknown samples possible. PMID:24969540

Cai, Yunbo; Li, Lingzhi; Wang, Zongtan; Sun, Jing Zhi; Qin, Anjun; Tang, Ben Zhong

2014-07-15

247

Investigation of Fluorescence Based Systems for Detection of Morphine in Urine.  

National Technical Information Service (NTIS)

Conditions for extraction of morphine free base from urine were optimized. Procedures for derivatization of the morphine extracted from urine with dansyl chloride and also with isatoic anhydride were developed. Methods for separation of the fluorescent mo...

D. A. Knowlton M. B. Neher

1974-01-01

248

Quantum dots (QDs) based fluorescent sensor for the selective determination of nimesulide.  

PubMed

Fluorescent PET (Photoinduced Electron Transfer) has been of particular growth in recent times. A novel PET based fluorescent sensor using unmodified CdSe quantum dots (QDs) has been developed for the trace determination of Nimesulide (NIM). The sensor is based on the selective fluorescence quenching of quantum dots by NIM in presence of other NSAIDs and is found that intensity of quenching is linearly related to NIM concentration in the range 8.2 × 10(-7) - 4.01 × 10(-5) M. The mechanism of interaction is discussed. Finally, the potential application of the proposed method for the trace determination of NIM in pharmaceutical formulation is demonstrated. PMID:23397489

Thomas, Divya; Lonappan, Laina; Rajith, Leena; Cyriac, Soumya T; Kumar, Krishnapillai Girish

2013-05-01

249

Antipyrine based arsenate selective fluorescent probe for living cell imaging.  

PubMed

Condensation of salicylaldehyde and 4-aminoantipyrine has yielded a new fluorescent probe (APSAL) capable of detecting intracellular arsenate at the micromolar level for the first time. The structure of the probe has been established by different spectroscopic techniques and confirmed from X-ray crystallography. Common anions, viz., F(-), Cl(-), Br(-), I(-), N(3)(-), NCO(-), NO(2)(-), NO(3)(-), SCN(-), CN(-), CH(3)COO(-), SO(4)(2-), ClO(4)(-), and HPO(4)(2-) do not interfere. The binding constant of APSAL for H(2)AsO(4)(-) has been determined using the Benesi-Hildebrand equation as 8.9 × 10(3) M(-1). Fluorescence quantum yield of APSAL (0.016) increases more than 12 times upon binding arsenate ion. PMID:23298301

Lohar, Sisir; Sahana, Animesh; Banerjee, Arnab; Banik, Avishek; Mukhopadhyay, Subhra Kanti; Matalobos, Jesús Sanmartín; Das, Debasis

2013-02-01

250

Organic fluorescent thermometers based on borylated arylisoquinoline dyes.  

PubMed

Borylated arylisoquinolines with redshifted internal charge-transfer (ICT) emission were prepared and characterized. Upon heating, significant fluorescence quenching was observed, which forms the basis for a molecular thermometer. In the investigated temperature range (283-323?K) an average sensitivity of -1.2 to -1.8?%?K(-1) was found for the variations in fluorescence quantum yield and lifetime. In the physiological temperature window (298-318?K) the average sensitivity even reaches values of up to -2.4?%?K(-1) . The thermometer function is interpreted as the interplay between excited ICT states of different geometry. In addition, the formation of an intramolecular Lewis pair can be followed by (11) B?NMR spectroscopy. This provides a handle to monitor temperature-dependent ground-state geometry changes of the dyes. The role of steric hindrance is addressed by the inclusion of a derivative that lacks the Lewis pair formation. PMID:24861774

Pais, Vânia F; Lassaletta, José M; Fernández, Rosario; El-Sheshtawy, Hamdy S; Ros, Abel; Pischel, Uwe

2014-06-16

251

Fluorescence-based video profile beam diagnostics: Theory and experience  

SciTech Connect

Inelastic collisions between accelerated particles and residual gas in the accelerator vessel can cause the residual gas to fluoresce. The gas fluorescence intensity is proportional to the current density of the particle beam. This process provides the foundation for a video diagnostic system to measure the profile and position of accelerated particle beams. This, in fact, has proven to be a useful diagnostic at several installations. This paper describes the light production process resulting from beam -- residual gas interactions and gives formulas for estimating the beam radiance for various conditions. Ground Test Accelerator (GTA) radiance calculations will be used as an example. In addition, measurement experiences with the GTA video diagnostics system will be discussed.

Sandoval, D.; Gilpatrick, D.; Shinas, M.; Garcia, R.; Yuan, V.; Zander, M.

1994-05-01

252

Novel fluorescence method for detection of ?-L-fucosidase based on CdTe quantum dots.  

PubMed

The enzyme ?-L-fucosidase (AFu) plays an important role in the diagnosis of hepatocellular carcinoma (HCC) and fucosidosis. In this paper, a simple, sensitive and precise method based upon measuring the fluorescence quenching of CdTe semiconductor quantum dots (QDs) was developed for detecting the enzymatic activity of AFu. The detection limit of AFu was 0.01 U/L (n = 3) and the linear relationship was 0.01-4 U/L. The selectivity experiment indicated excellent selectivity for AFu over a number of interfering species. We have also studied the detection mechanism of AFu by X-ray photoelectron spectroscopy (XPS) and found that the quenching effect was caused by the oxidation of tellurium by 2-chloro-4-nitrophenol (2-CNP) which produced in AFu catalytic reaction. Moreover, the AFu sensor based on QDs was used satisfactorily for the assessment of AFu activity in serum samples. It will most probably be applicable in assembling diagnostic microdevice to realize the rapid clinic analysis of AFu. PMID:22486298

Chen, Zhenzhen; Ren, Xiangling; Meng, Xianwei; Zhang, Yanqi; Chen, Dong; Tang, Fangqiong

2012-05-01

253

X-ray fluorescence analysis based on Kumakhov optics  

Microsoft Academic Search

The use of Kumakhov optics in x-ray fluorescence analysis is considered. Thanks to high efficiency of a polycapillary lens the concentration of x-ray detector in a close proximity to the sample decreases sufficiently the time of exposure. It is shown experimentally that in the case of use of a small x-ray source with power of 2W the minimal detection limit

Svetlana V. Nikitina; Nariman S. Ibraimov; Alexander S. Stcherbakov

1998-01-01

254

Computed tomography based spectral imaging for fluorescence microscopy  

NASA Astrophysics Data System (ADS)

Multispectral imaging has been used for decades in remote sensing to enhance the classification, discrimination and characterization of materials. Only recently has this same technology been similarly applied to fixed biological samples in cytogenetics, pathology and medicine. A further extension to in vivo studies is often limited by the low levels of associated fluorescence as well as the increased temporal resolution required to analyze physiological changes. In addition, the cellular response to a specific agonist is often heterogeneous across the cellular field requiring a combination of sufficient spatial and temporal resolutions. A computed tomography imaging spectrometer (CTIS) has been developed which overcomes these limitations by simultaneously collecting extended range spectral information (470--740 nm, 5 nm sampling) across a 2-D field of view (200 mum x 200 mum, 0.96 mum sampling). The CTIS uses a computer generated hologram to produce a 5 x 5 array of images with differing amounts and directions of dispersion. This set of images allows the 3-D signal (x, y, lambda) from a fluorescent sample to be mapped onto a 2-D detector array. In this way, the full spectral and spatial information is acquired for a 2-D cellular field during a single integration time (presently 2 sec for biological specimens). The CTIS's design, calibration, and underlying theory are described in detail. In addition, the capability of the CTIS to simultaneously collect the fluorescence emission of multiple fluorophores across a 2-D cellular field is demonstrated. Specifically, the combined spectral variations of seminapthorhodafluor-I and enhanced green fluorescent protein were followed in rat insulinoma cells in order to extend the linear range of intracellular pH detection.

Ford, Bridget Kathleen

255

Immunoanalytical techniques for pesticide monitoring based on fluorescence detection  

Microsoft Academic Search

In the field of environmental analysis there is still great potential for development and application of immunoanalytical\\u000a techniques (IT). Heterogeneous and homogeneous immunoassays (IA), flow-injection immunoanalysis (FIIA) and immunosensors (IS)\\u000a with different detection principles have been developed. In this review we focus on fluorescence methods for pesticide monitoring\\u000a published since 1992. These techniques offer a high degree of selectivity and,

Uwe Schobel; Claudia Barzen; Günter Gauglitz

2000-01-01

256

Simple method of determination of copper, mercury and lead in potable water with preliminary pre-concentration by total reflection X-ray fluorescence spectrometry  

NASA Astrophysics Data System (ADS)

Total reflection X-ray fluorescence spectrometry and chemical pre-concentration procedures have been applied for the analysis of trace concentrations of copper, mercury, and lead in drinking water samples. A simple total reflection module has been used in X-ray measurements. The elements under investigation were pre-concentrated by complexation using a mixture of carbamates followed by solvent extraction with methyl isobutyl ketone. The preconcentration procedure was tested with the use of twice-distilled water samples and samples of mineral and tap water spiked with known additions of copper, mercury, and lead. The obtained recovery and precision values are presented. The minimum detection limits for the determination of these elements in mineral and tap water samples were found to be 40 ng l -1, 60 ng l -1, and 60 ng l -1, respectively.

Ho?y?ska, B.; Ostachowicz, B.; W?grzynek, D.

1996-06-01

257

Achieving Highly Efficient Simple-Emission Layer Fluorescence/Phosphorescence Hybrid White Organic Light-Emitting Devices via Effective Confinement of Triplets.  

PubMed

Achieving high efficiencies in simple device configurations is a long-standing and meaningful target for organic light-emitting devices (OLEDs). Herein, by utilizing an efficient blue-violet fluorophor (CzS1) that has a high triplet energy of 2.62 eV, the significance of effective confinement of the green triplets in fluorescence/phosphorescence hybrid white devices (F/P-WOLEDs) that have highly simplified emission layers (EMLs) containing only RGB emitters was demonstrated. The non-p-i-n warm-white device exhibited excellent performance with a maximum forward power efficiency high up to 42.1 lm W(-1), and maintaining at 26.3 lm W(1-) at a practical luminance of 1000 cd m(-2). PMID:24877610

Ye, Jun; Chen, Zhan; An, Feifei; Sun, Mingliang; Mo, Hin-Wai; Zhang, Xiaohong; Lee, Chun-Sing

2014-06-25

258

An Evaluation of Commercial Fluorescent Bead-Based Luminex Cytokine Assays  

Microsoft Academic Search

The recent introduction of fluorescent bead-based technology, allowing the measurement of multiples analytes in a single 25-50 ml sample has revolutionized the study of cytokine responses. However, such multiplex approaches may compromise the ability of these assays to accurately measure actual cytokine levels. This study evaluates the performance of three commercially available multiplex cytokine fluorescent bead-based immunoassays (Bio-Rad's Cytokine 17-plex

Joel Fleury Djoba Siawaya; Teri Roberts; Chantal Babb; Gillian Black; Hawa Jande Golakai; Kim Stanley; Nchinya Bennedict Bapela; Eileen Hoal; Shreemanta Parida; Paul van Helden; Gerhard Walzl

2008-01-01

259

A highly enantioselective chiral Schiff-base fluorescent sensor for mandelic acid  

Microsoft Academic Search

A chiral Schiff-base compound, 4-methyl-2,6-bis-[(2-hydroxy-1-phenylethylimino)methyl]phenol, is found to act as highly enantioselective fluorescent agent for ?-hydroxycarboxylic acid, e.g., mandelic acid. It is observed that, within a certain concentration range, one enantiomer of the chiral acid can increase the fluorescence intensity of the Schiff-base compound 122-fold while the other enantiomer enhances the intensity only 42-fold. Such highly enantioselective responses towards the

Koushik Dhara; Krishanu Sarkar; Partha Roy; Mahasweta Nandi; Asim Bhaumik; Pradyot Banerjee

2008-01-01

260

Analysis of total aerobic viable counts in samples of raw meat using fluorescence-based probe and oxygen consumption assay  

Microsoft Academic Search

A simple test for determining total aerobic viable counts in raw meat is presented. Homogenates of meat samples are prepared in full PBW medium, dispensed in the wells of 96-well plate together with the oxygen-sensing probe, Redlight, covered with oil and monitored on a fluorescent reader at 30°C. The probe produces characteristic sigmoidal profiles of fluorescence reflecting depletion of sample

Fiach O’Mahony; Rebecca A. Green; Chris Baylis; Richard Fernandes; Dmitri B. Papkovsky

2009-01-01

261

Fluorescence-based transient state monitoring for biomolecular spectroscopy and imaging  

PubMed Central

To increase read-out speed, sensitivity or specificity, an often applied strategy in fluorescence-based biomolecular spectroscopy and imaging is to simultaneously record two or more of the fluorescence parameters: intensity, lifetime, polarization or wavelength. This review highlights how additional, to-date largely unexploited, information can be extracted by monitoring long-lived, photo-induced transient states of organic dyes and their dynamics. Two major approaches are presented, where the transient state information is obtained either from fluorescence fluctuation analysis or by recording the time-averaged fluorescence response to a time-modulated excitation. The two approaches combine the detection sensitivity of the fluorescence signal with the environmental sensitivity of the long-lived transient states. For both techniques, proof-of-principle experiments are reviewed, and advantages, limitations and possible applications for biomolecular cellular biology studies are discussed.

Widengren, Jerker

2010-01-01

262

DNA/ligand/ion-based ensemble for fluorescence turn on detection of cysteine and histidine with tunable dynamic range.  

PubMed

A new type of rapid, highly sensitive, and selective fluorescence turn-on assay for detection of cysteine and histidine using a DNA/ligand/ion ensemble is developed. This assay is based on the highly specific interaction between the amino acids and the metal ions and the strong fluorescence thiazole orange (TO)/DNA probe in a competition assay format. The resulting high sensitivity and selectivity for cysteine and histidine was achieved by changing the metal ions. The system is simple in design and fast in operation and is more convenient and promising than other methods. The novel strategy eliminated the need of organic cosolvents, enzymatic reactions, separation processes, chemical modifications, and sophisticated instrumentations. The detection and discrimination process can be seen with the naked eye under a hand-held UV lamp and can be easily adapted to automated high-throughput screening. The detection limit of this method is lower than or at least comparable to previous fluorescence-based methods. The dynamic range of the sensor can be tuned simply by adjusting the concentration of metal ions. Importantly, the protocol offers high selectivity for the determination of cysteine among amino acids found in proteins and in serum samples. The assay shows great potential for practical application as a disease-associated biomarker and will be needed to satisfy the great demand of amino acid determination in fields such as food processing, biochemistry, pharmaceuticals, and clinical analysis. PMID:20806886

Pu, Fang; Huang, Zhenzhen; Ren, Jinsong; Qu, Xiaogang

2010-10-01

263

Soft nanomaterial-based targeting polymersomes for near-infrared fluorescence multispectral in vivo imaging.  

PubMed

We report here the soft nanomaterial-based targeting polymersomes for near-infrared (NIR) fluorescence imaging to carry out in vivo tumor detection. Two polymersome-based NIR fluorescent probes were prepared through the self-assembly of amphiphilic block copolymers, poly(butadiene-b-ethylene oxide) (PEO-b-PBD). Each of them was encapsulated with distinct hydrophobic near-infrared dyes (DiD and DiR) and modified with different targeting ligands (anti-CEA antibody and anti-EGFR antibody), respectively. After simultaneous injection of these two probes into the tumor-bearing mice via tail vein, multispectral near-infrared fluorescence images were obtained. The results indicate that both probes are successfully directed to the tumor foci, where two distinguishable fluorescent signals were detected through the unmixed fluorescence images. By taking advantage of two targeting polymersome-based probes with distinct fluorescent features, the proposed multispectral near-infrared fluorescence imaging method can greatly improve the specificity and accuracy for in vivo tumor detection. PMID:23069779

Li, Zuhong; Wu, Liyuan; Hu, Peiran; Han, Sihai; Zhang, Tao; Fan, Hongliang; Jin, Wei; Jin, Qinhan; Mu, Ying

2012-11-21

264

Detection of enzyme activity in orthotopic murine breast cancer by fluorescence lifetime imaging using a fluorescence resonance energy transfer-based molecular probe  

PubMed Central

Cancer-related enzyme activity can be detected noninvasively using activatable fluorescent molecular probes. In contrast to “always-on” fluorescent molecular probes, activatable probes are relatively nonfluorescent at the time of administration due to intramolecular fluorescence resonance energy transfer (FRET). Enzyme-mediated hydrolysis of peptide linkers results in reduced FRET and increase of fluorescence yield. Separation of signal from active and inactive probe can be difficult with conventional intensity-based fluorescence imaging. Fluorescence lifetime (FLT) measurement is an alternative method to detect changes in FRET. Thus, we investigate FLT imaging for in vivo detection of FRET-based molecular probe activation in an orthotopic breast cancer model. Indeed, the measured FLT of the enzyme-activatable molecular probe increases from 0.62 ns just after injection to 0.78 ns in tumor tissue after 4 h. A significant increase in FLT is not observed for an always-on targeted molecular probe with the same fluorescent reporter. These results show that FLT contrast is a powerful addition to preclinical imaging because it can report molecular activity in vivo due to changes in FRET. Fluorescence lifetime imaging exploits unique characteristics of fluorescent molecular probes that can be further translated into clinical applications, including noninvasive detection of cancer-related enzyme activity.

Solomon, Metasebya; Guo, Kevin; Sudlow, Gail P.; Berezin, Mikhail Y.; Edwards, W. Barry; Achilefu, Samuel; Akers, Walter J.

2011-01-01

265

Detection of enzyme activity in orthotopic murine breast cancer by fluorescence lifetime imaging using a fluorescence resonance energy transfer-based molecular probe  

NASA Astrophysics Data System (ADS)

Cancer-related enzyme activity can be detected noninvasively using activatable fluorescent molecular probes. In contrast to ``always-on'' fluorescent molecular probes, activatable probes are relatively nonfluorescent at the time of administration due to intramolecular fluorescence resonance energy transfer (FRET). Enzyme-mediated hydrolysis of peptide linkers results in reduced FRET and increase of fluorescence yield. Separation of signal from active and inactive probe can be difficult with conventional intensity-based fluorescence imaging. Fluorescence lifetime (FLT) measurement is an alternative method to detect changes in FRET. Thus, we investigate FLT imaging for in vivo detection of FRET-based molecular probe activation in an orthotopic breast cancer model. Indeed, the measured FLT of the enzyme-activatable molecular probe increases from 0.62 ns just after injection to 0.78 ns in tumor tissue after 4 h. A significant increase in FLT is not observed for an always-on targeted molecular probe with the same fluorescent reporter. These results show that FLT contrast is a powerful addition to preclinical imaging because it can report molecular activity in vivo due to changes in FRET. Fluorescence lifetime imaging exploits unique characteristics of fluorescent molecular probes that can be further translated into clinical applications, including noninvasive detection of cancer-related enzyme activity.

Solomon, Metasebya; Guo, Kevin; Sudlow, Gail P.; Berezin, Mikhail Y.; Edwards, W. Barry; Achilefu, Samuel; Akers, Walter J.

2011-06-01

266

Autoregressive-model-based fluorescence-lifetime measurements by phase-modulation fluorometry using a pulsed-excitation light source and a high-gain photomultiplier tube.  

PubMed

We propose a novel method for measuring fluorescence lifetimes by use of a pulsed-excitation light source and an ordinary or a high-gain photomultiplier tube (PMT) with a high-load resistor. In order to obtain the values of fluorescence lifetimes, we adopt a normal data-processing procedure used in phase-modulation fluorometry. We apply an autoregressive (AR)-model-based data-analysis technique to fluorescence- and reference-response time-series data obtained from the PMT in order to derive plural values of phase differences at a repetition frequency of the pulsed-excitation light source and its harmonic ones. The connection of the high-load resistor enhances sensitivity in signal detection in a certain condition. Introduction of the AR-model-based data-analysis technique improves precision in estimating the values of fluorescence lifetimes. Depending on the value of the load resistor and that of the repetition frequency, plural values of fluorescence lifetimes are obtained at one time by utilizing the phase information of harmonic frequencies. Because the proposed measurement system is simple to construct, it might be effective when we need to know approximate values of fluorescence lifetimes readily, such as in the field of biochemistry for a screening purpose. PMID:19891834

Iwata, Tetsuo; Ito, Ritsuki; Mizutani, Yasuhiro; Araki, Tsutomu

2009-11-01

267

Enhancing stimulated emission-based fluorescence detection with interferometric setup  

NASA Astrophysics Data System (ADS)

Fluorescence lifetime imaging microscopy (FLIM) can reveal important biological information and recently stimulated emission (SE) has been applied in FLIM to improve the spatial resolution of micrographs and detect fluorophore over a long working distance. An issue with SE is that the SE signal is much weaker than the probe laser beam that is used to generate the SE, therefore the signal to background ratio is low. Here we demonstrate using interferometric setup to decrease this background laser intensity, thus achieving higher S/N ratio and dye concentration detection sensitivity in SE microscopy.

Chung, Shen-Shou Max; Deng, Jia-Hui; Lin, Po-Lin; Kao, Fu-Jen

2014-02-01

268

Novel and remarkable enhanced-fluorescence system based on gold nanoclusters for detection of tetracycline.  

PubMed

Tetracycline and Eu(3+), while coexisting, usually appear as a complex by chelating. This complex shows low fluorescence intensity, leading to its limitation of analytical goals. Gold nanoclusters (AuNCs), emerging as novel nano-material, are attracting increasing attentions in multiple fields. Herein, gold nanoclusters first function as a fluorescence-enhanced reagent rather than a conventional fluorescent-probe, and a dramatic enhanced-fluorescence system was built based on Eu(3+)-Tetracycline complex (EuTC) by introducing gold nanoclusters. Simultaneously, three types of gold nanoclusters were employed for exploring various conditions likely affecting the system, which demonstrate that no other gold nanoclusters than DNA-templated gold nanoclusters enormously caused fluorescence-enhancement of EuTC. Moreover, this enhanced-fluorescence system permitted available detection of tetracycline (TC) in a linear range of 0.01-5?M, with a detection limit of 4nM at a signal-to-noise ratio of 3. Significantly, the practicality of this method for detection of TC in human urine and milk samples was validated, demonstrating its advantages of simplicity, sensitivity and low cost. Interestingly, this system described here is probably promising for kinds of applications based on its dramatically enhanced-fluorescence. PMID:24720959

Yang, Xiaoming; Zhu, Shanshan; Dou, Yao; Zhuo, Yan; Luo, Yawen; Feng, Yuanjiao

2014-05-01

269

Enantioselective Fluorescent Recognition of Chiral Acids by Cyclohexane-1,2-diamine-Based Bisbinaphthyl Molecules  

PubMed Central

The cyclohexane-1,2-diamine-based bisbinaphthyl macrocycles (S)-/(R)-5 and their cyclic and acyclic analogs are synthesized. The interactions of these compounds with various chiral acids are studied. Compounds (S)-/(R)-5 exhibit highly enantioselective fluorescent responses and high fluorescent sensitivity toward ?-hydroxycarboxylic acids and N-protected amino acids. Among these interactions, (S)-mandelic acid (10?3 M) led to over 20 fold fluorescence enhancement of (S)-5 (1.0 × 10?5 M in benzene/0.05% DME) at the monomer emission and (S)-hexahydromandelic acid (10?3 M) led to over 80 fold fluorescence enhancement. These results demonstrate that (S)-5 is useful as an enantioselective fluorescent sensor for the recognition of the chiral acids. On the basis of the study of the structures of (S)-5 and the previously reported 1,2-diphenylethylenediamine-based bisbinaphthyl macrocycle (S)-4, the large fluorescence enhancement of (S)-5 with achirality-matched ?-hydroxycarboxylic acid is attributed to the formation of a structurally rigidified host-guest complex and the further interaction of this complex with the acid to suppress the photo-induced electron transfer fluorescent quenching caused by the nitrogens in (S)-5.

Li, Zi-Bo; Lin, Jing; Sabat, Michal; Hyacinth, Marilise; Pu, Lin

2008-01-01

270

Enantioselective fluorescent recognition of chiral acids by cyclohexane-1,2-diamine-based bisbinaphthyl molecules.  

PubMed

The cyclohexane-1,2-diamine-based bisbinaphthyl macrocycles (S)-/(R)-5 and their cyclic and acyclic analogues are synthesized. The interactions of these compounds with various chiral acids are studied. Compounds (S)-/(R)-5 exhibit highly enantioselective fluorescent responses and high fluorescent sensitivity toward alpha-hydroxycarboxylic acids and N-protected amino acids. Among these interactions, (S)-mandelic acid (10(-3) M) led to over 20-fold fluorescence enhancement of (S)-5 (1.0 x 10(-5) M in benzene/0.05% DME) at the monomer emission, and (S)-hexahydromandelic acid (10(-3) M) led to over 80-fold fluorescence enhancement. These results demonstrate that (S)-5 is useful as an enantioselective fluorescent sensor for the recognition of the chiral acids. On the basis of the study of the structures of (S)-5 and the previously reported 1,2-diphenylethylenediamine-based bisbinaphthyl macrocycle (S)-4, the large fluorescence enhancement of (S)-5 with a chirality-matched alpha-hydroxycarboxylic acid is attributed to the formation of a structurally rigidified host-guest complex and the further interaction of this complex with the acid to suppress the photoinduced electron-transfer fluorescent quenching caused by the nitrogens in (S)-5. PMID:17530897

Li, Zi-Bo; Lin, Jing; Sabat, Michal; Hyacinth, Marilise; Pu, Lin

2007-06-22

271

Selective detection of iodide and cyanide anions using gold-nanoparticle-based fluorescent probes.  

PubMed

We developed two simple, rapid, and cost-effective fluorescent nanosensors, both featuring bovine serum albumin labeled with fluorescein isothiocyanate (FITC))-capped gold nanoparticles (FITC-BSA-Au NPs), for the selective sensing of cyanide (CN(-)) and iodine (I(-)) ions in high-salinity solutions and edible salt samples. During the preparation of FITC-BSA-Au NP probes, when AuNPs were introduced to the mixture containing FITC and BSA, the unconjugated FITC and FITC-labeled BSA (FITC-BSA) adsorbed to the particles' surfaces. These probes operated on a basic principle that I(-) and CN(-) deposited on the surfaces of the Au NPs or the etching of Au NPs induced the release of FITC molecules or FITC-BSA into the solution, and thus restored the florescence of FITC. We employed FITC-BSA to protect the Au NPs from significant aggregation in high-salinity solutions. In the presence of masking agents such as S(2)O(8)(2-)/Pb(2+), FITC-BSA-Au NPs facilitated the selective detection of CN(-) (by at least 150-fold in comparison with other anions). We also demonstrated that the FITC-BSA-Au NPs in the presence of H(2)O(2) could selectively detect I(-) down to 50 nM. Taking advantages of their high stability and selectivity, we employed our FITC-BSA-Au NP-based probes for the detection of CN(-) and I(-) in water samples (pond water, tap water, and seawater) and detection of I(-) in edible salt samples, respectively. This simple, rapid, and cost-effective sensing system appears to demonstrate immense practical potential for the detection of anions in real samples. PMID:22524233

Wei, Shih-Chun; Hsu, Pang-Hung; Lee, Yen-Fei; Lin, Yang-Wei; Huang, Chih-Ching

2012-05-01

272

Temperature-modulated fluorescence tomography based on both concentration and lifetime contrast  

NASA Astrophysics Data System (ADS)

It is challenging to image fluorescence objects with high spatial resolution in a highly scattering medium. Recently reported temperature-sensitive indocyanine green-loaded pluronic nanocapsules can potentially alleviate this problem. Here we demonstrate a frequency-domain temperature-modulated fluorescence tomography system that could acquire images at high intensity-focused ultrasound resolution with use of these nanocapsules. The system is experimentally verified with a phantom study, where a 3-mm fluorescence object embedded 2 cm deep in a turbid medium is successfully recovered based on both intensity and lifetime contrast.

Lin, Yuting; Kwong, Tiffany C.; Bolisay, Linden; Gulsen, Gultekin

2012-05-01

273

Thermoresponsive fluorescence of a graphene-polymer composite based on a local surface plasmon resonance effect.  

PubMed

A water-processable blue fluorescent silver nanoparticle@graphene-polymer composite (Ag@G-pNIPAM) consisting of graphene coated with a thermally responsive poly-(N-isopropylacrylamide) (pNIPAM) shell is prepared. The pNIPAM shell swells or collapses as a function of temperature, serving as a means to trap silver nanoparticles in solution and get them sufficiently close to the graphene core to provide fluorescence enhancement based on the local surface plasmon resonance (LSPR) effect. The unique thermoresponsive properties and high enhancement ratio of the material should find application in solution fluorescence enhancers and a variety of biomedical applications, such as cellular uptake, sensing and imaging. PMID:24806411

Huang, Yunyun; Lin, Wensheng; Chen, Kan; Zhang, Wenkai; Chen, Xudong; Zhang, Ming Qiu

2014-06-21

274

Triazole based ratiometric fluorescent probe for Zn2+ and its application in bioimaging.  

PubMed

An efficient fluorescent chemosensor 4-((2-hydroxynaphthalen-1-yl)methyleneamino)-3-phenyl-1H-1,2,4-triazole-5(4H)-thione, based on triazole has been designed by condensing 2-hydroxy-1-napthaldehyde with amine, appended to 1,2,4-triazole unit. The probe displays excellent selectivity and sensitivity in both absorbance and fluorescence detection of Zn2+ over other essential metal ions. The nature of fluorescence behavior of receptor upon addition of Zn2+ has been obtained from Density Functional Theory calculations. Imaging experiment indicates that probe works effectively for intracellular Zn2+ imaging with good cell permeability and biocompatibility. PMID:24177867

Iniya, Murugan; Jeyanthi, Dharmaraj; Krishnaveni, Karuppiah; Mahesh, Ayyavu; Chellappa, Duraisamy

2014-02-24

275

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

PubMed

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

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

2014-08-15

276

Novel fluorescent biosensor for ?-glucosidase inhibitor screening based on cationic conjugated polymers.  

PubMed

A new fluorescent biosensor has been designed to screen ?-glucosidase inhibitors (AGIs) sensitively by utilizing signal amplification effect of conjugated polymers. The fluorescence of cationic poly(fluorenylene phenylene) (PFP) was quenched in the presence of para-nitrophenyl-?-d-glucopyranoside and ?-glucosidase, and turned on upon addition of AGIs. Thus, a new method was developed for AGIs screening based on the fluorescence turn-off/turn-on. The IC(50) values obtained for inhibitors were compared with that reported using absorption spectroscopy. All results present the new method is more sensitive and promising in screening AGIs and inhibitors of other enzymes whose hydrolysis product is 4-nitrophenol. PMID:22823570

Cao, Ali; Tang, Yanli; Liu, Yue

2012-08-01

277

A multivariate multianalyte screening method for sulfonamides in milk based on front-face fluorescence spectroscopy.  

PubMed

Screening methods are used to detect the presence of a substance or class of substances at the level of interest and are specifically designed to avoid false compliant results. They should allow the running of a high number of samples per day at a low cost under routine conditions. In this work, a rapid and simple method for the screening of six sulfonamides (sulfadiazine, SD; sulfamerazine, SMR; sulfamethazine, SMT; sulfachloropyridazine, SCP; sulfathiazole, STZ and sulfamethoxazole, SMO) in milk samples is proposed and assessed according to the criteria required by the European Regulation, Decision 2002/657/EC. The method is based on modelling front-face fluorescence emission spectra by means of partial least squares class modelling (PLS-CM). The milk samples are pre-treated with a single easy step of derivatization with fluorescamine. After confirming that the method has equal analytical sensitivity for all the six sulfonamides, it is established that the multivariate analytical sensitivity at 100 microg L(-1) is 37.5 microg L(-1) when analysing a mixture of six sulfonamides added to different brands of milk and measured in different days. In addition, the method is applied to samples from 11 commercial brands of milk. For beta=0.05, threshold value established by the Decision 2002/657/EC for this method, the probability of false non-compliance, alpha, is equal to 0.17, allowing the suitable screening of these six sulfonamides. PMID:20005325

Rodríguez, N; Ortiz, M C; Sarabia, L A; Herrero, A

2010-01-11

278

Boronate-Based Fluorescent Probes for Imaging Cellular Hydrogen Peroxide  

PubMed Central

The syntheses, properties, and biological applications of the Peroxysensor family, a new class of fluorescent probes for hydrogen peroxide, are presented. These reagents utilize a boronate deprotection mechanism to provide high selectivity and optical dynamic range for detecting H2O2 in aqueous solution over similar reactive oxygen species (ROS) including superoxide, nitric oxide, tert-butyl hydroperoxide, hypochlorite, singlet oxygen, ozone, and hydroxyl radical. Peroxyresorufin-1 (PR1), Peroxyfluor-1 (PF1), and Peroxyxanthone-1 (PX1) are first-generation probes that respond to H2O2 by an increase in red, green, and blue fluorescence, respectively. The boronate dyes are cell-permeable and can detect micromolar changes in H2O2 concentrations in living cells, including hippocampal neurons, using confocal microscopy and two-photon microscopy. The unique combination of ROS selectivity, membrane permeability, and a range of available excitation/emission colors establishes the potential value of PR1, PF1, PX1, and related probes for interrogating the physiology and pathology of cellular H2O2.

Miller, Evan W.; Albers, Aaron E.; Chang, Christopher J.; Pralle, Arnd; Isacoff, Ehud Y.

2006-01-01

279

Tissue viability assessment via laser-based fluorescence monitor  

NASA Astrophysics Data System (ADS)

A preliminary study of the degree to which recently introduced inhalation anesthetics influence the intracellular energetic metabolism of isolated perfused rat livers is undertaken via NADH fluorometry. During liver transplantation, anesthesiologists desire to maintain a high level of metabolic energy status in newly transplanted liver tissue. Ischemic storage of donor liver tissue prior to transplantation is known to inhibit mitochondrial electron transfer, which results in decreased levels of ATP and increased levels of NADH in the stored tissue. The ability of transplanted liver tissue to regenerate ATP at normal levels is desirable for early post- operative recovery of liver function. Previous studies have examined the differential effects inhalation anesthetics have on the energetic metabolism of tissue at the cellular level; the trend of such agents is to induce a dose-dependent increase in NADH fluorescence in accordance with their strengths as general anesthetics. The present study evaluates the differential effects exhibited by new inhalation anesthetics on the return of function of energetic metabolism in liver tissue. The third-harmonic (355 nm) output of a Nd:YAG laser is spatially filtered and used as the excitation source for surface fluorometric measurements of isolated buffer-perfused rat livers. Lastly, maximum fluorescence emission versus spot-size are measured.

Curtis, Craig H.; Peyghambarian, Nasser; Dereniak, Eustace L.; Frink, Edward

1996-04-01

280

Screening method for organic aciduria by spectrofluorometric measurement of total dicarboxylic acids in human urine based on intramolecular excimer-forming fluorescence derivatization  

Microsoft Academic Search

A simple screening method of organic aciduria by spectrofluorometric measurement of total dicarboxylic acids in human urine is described. This method is based on an intramolecular excimer-forming fluorescence derivatization with a pyrene reagent, 4-(1-pyrene)butanoic acid hydrazide (PBH). Dicarboxylic acids in urine were converted to the corresponding dipyrene-labeled derivatives by reaction with PBH in the presence of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and pyridine, and

Hideyuki Yoshida; Junya Araki; Junichiro Sonoda; Hitoshi Nohta; Junichi Ishida; Shinichi Hirose; Masatoshi Yamaguchi

2005-01-01

281

A coumarin-quinolinium-based fluorescent probe for ratiometric sensing of sulfite in living cells.  

PubMed

Based on a novel coumarin-quinolinium platform, probe was rationally designed and synthesized as a novel ratiometric fluorescent sensor for sulfite anions. The probe exhibited a wide dynamic concentration range for sulfite anions in a PBS buffer (containing 1 mg mL(-1) BSA). More importantly, the probe was suitable for ratiometric fluorescence imaging in living cells with high sensitivity, favorable selectivity, and minimal cytotoxicity. PMID:24849005

Tan, Li; Lin, Weiying; Zhu, Sasa; Yuan, Lin; Zheng, Kaibo

2014-06-11

282

Read-out concepts for multiplexed bead-based fluorescence immunoassays on centrifugal microfluidic platforms  

Microsoft Academic Search

We present novel concepts to process and read out multiplexed, bead-based fluorescence immunoassays. At the start of the read-out process, a statistically arranged monolayer of color-encoded beads is aggregated in a detection chamber. Each bead is first identified by incorporated color tags which are either dyes or luminescing quantum dots (QDs). Subsequently, the reaction-specific fluorescence signal is quantified. The read-out

L. Riegger; M. Grumann; T. Nann; J. Riegler; O. Ehlert; W. Bessler; K. Mittenbuehler; G. Urban; L. Pastewka; T. Brenner; R. Zengerle; J. Ducrée

2006-01-01

283

A clinical trial for therapeutic drug monitoring using microchip-based fluorescence polarization immunoassay  

Microsoft Academic Search

Microchip analysis is a promising method for therapeutic drug monitoring. This led us to evaluate a microchip-based fluorescence\\u000a polarization immunoassay (FPIA) system for point-of-care testing on patients being treated with theophylline. The sera were\\u000a collected from 20 patients being treated with theophylline. Fluorescence polarization was measured on the microchip and theophylline\\u000a concentrations in serum were obtained. Regression analysis of the

Tomoya Tachi; Tetsunari Hase; Yukihiro Okamoto; Noritada Kaji; Takeshi Arima; Hiroyuki Matsumoto; Masashi Kondo; Manabu Tokeshi; Yoshinori Hasegawa; Yoshinobu Baba

284

Whole-body Fluorescent Optical Imaging Based on Power Light Emitting Diode  

Microsoft Academic Search

With complex configuration, the general whole-body fluorescence optical imaging system is power-consuming for it is mainly composed of laser or mercury lamp, filter and fiber-optic cable. In this paper we aimed at setting up a compact imaging system based on power light emitting diode (LED). We first discussed fluorescence excitation efficiency of mercury lamp and LED. Then we developed a

Yanping Chen; Tao Xiong; Li Yu; Shaoqun Zeng; Qingming Luo

2005-01-01

285

A fluorescent glucose biosensor based on immobilized glucose oxidase on bamboo inner shell membrane  

Microsoft Academic Search

A fluorescent glucose biosensor was constructed by immobilizing glucose oxidase on a bamboo inner shell membrane with glutaraldehyde as a cross-linker. The detection scheme was based on the depletion of dissolved oxygen content upon exposure to glucose solution with a concomitant increase in the fluorescence intensity of an oxygen transducer, tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(?) ditetrakis(4-chlorophenyl)borate. The enzyme immobilization, effect of pH, temperature and

Xiaofeng Yang; Zaide Zhou; Dan Xiao; Martin M. F. Choi

2006-01-01

286

A fluorescence-based imaging-fiber electrode chemical sensor for hydrogen peroxide  

Microsoft Academic Search

The fabrication and characterization of imaging fiber electrodes (IFEs) is presented, and the concept of an electrochemically-modulated, fluorescence-based, imaging-fiber electrode chemical sensor (IFECS) is demonstrated. In brief, an imaging fiber distal tip was sputter-coated with a semi-transparent gold layer to create an IFE, and a fluorescent redox dye was immobilized across the IFE face to create an IFECS. An electroactive

Samina S Khan; Eunsook S Jin; Neso Sojic; Paul Pantano

2000-01-01

287

A dissolved oxygen sensor based on ruthenium fluorescence and u-shaped plastic optical fiber  

Microsoft Academic Search

A dissolved oxygen sensor based on ruthenium(Ru) fluorescence and U-shape plastic optical fiber (POF) was described. Dichlorotris (1, 10-phenanthroline) ruthenium (II) was used as an oxygen indicator, which was coated on to the surface of a 1mm diameter U-shaped POF. Phase modulation technique is used to measure fluorescence lifetime. The phase difference between 100% and 0% dissolved oxygen is 1.78

Fenghong Chu; Haiwen Cai; Ronghui Qu; Zujie Fang

2007-01-01

288

A fluorescence ratiometric chemosensor for Fe(3+) based on TBET and its application in living cells.  

PubMed

Based on a through bond energy transfer (TBET) between rhodamine and naphthalimide fluorophores, a fluorescent ratiometric chemosensor L was designed and prepared for highly selective detection of Fe(3+) in aqueous solution and in living EC109 cells. These significant changes in the fluorescence color could be used for naked-eye detection. The reversibility established the potential of the probe as chemosensor for Fe(3+) detection. PMID:25059132

Wang, Cuicui; Zhang, Di; Huang, Xiaoyan; Ding, Peigang; Wang, Zhenji; Zhao, Yufen; Ye, Yong

2014-10-01

289

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

PubMed

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

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

2012-09-01

290

Fabry-Perot-based Fourier-transform hyperspectral imaging allows multi-labeled fluorescence analysis.  

PubMed

We demonstrate the ability of our hyperspectral imaging device, based on a scanning Fabry-Perot interferometer, to obtain a single hyper-image of a sample marked with different fluorescent molecules, and to unambiguously discriminate them by observing their spectral fingerprints. An experiment carried out with cyanines, fluorescein, and quantum dots emitting in the yellow-orange region, demonstrates the feasibility of multi-labeled fluorescence microscopy without the use of multiple filter sets or dispersive means. PMID:24922016

Pisani, Marco; Zucco, Massimo

2014-05-10

291

Effects of alcohols on fluorescence intensity and color of a discharged-obelin-based biomarker.  

PubMed

Photoproteins are responsible for bioluminescence of marine coelenterates; bioluminescent and fluorescent biomarkers based on photoproteins are useful for monitoring of calcium-dependent processes in medical investigations. Here, we present the analysis of intensity and color of light-induced fluorescence of Ca(2+)-discharged photoprotein obelin in the presence of alcohols (ethanol and glycerol). Complex obelin spectra obtained at different concentrations of the alcohols at 350- and 280-nm excitation (corresponding to polypeptide-bound coelenteramide and tryptophan absorption regions) were deconvoluted into Gaussian components; fluorescent intensity and contributions of the components to experimental spectra were analyzed. Five Gaussian components were found in different spectral regions-ultraviolet (tryptophan emission), blue-green (coelenteramide emission), and red (hypothetical indole-coelenteramide exciplex emission). Inhibition coefficients and contributions of the components to experimental fluorescent spectra showed that presence of alcohols increased contributions of ultraviolet, violet, and red components, but decreased contributions of components in the blue-green region. The effects were related to (1) changes of proton transfer efficiency in fluorescent S*1 state of coelenteramide in the obelin active center and (2) formation of indole-coelenteramide exciplex at 280-nm photoexcitation. The data show that variation of fluorescence color and intensity in the presence of alcohols and dependence of emission spectra on excitation wavelength should be considered while applying the discharged obelin as a fluorescence biomarker. PMID:24618986

Alieva, Roza R; Belogurova, Nadezhda V; Petrova, Alena S; Kudryasheva, Nadezhda S

2014-05-01

292

Rapid, Photoactivatable Turn-On Fluorescent Probes Based On an Intramolecular Photoclick Reaction  

PubMed Central

Photoactivatable fluorescent probes are invaluable tools for the study of biological processes with high resolution in space and time. Numerous strategies have been developed in generating photoactivatable fluorescent probes, most of which rely on the photo-“uncaging” and photoisomerization reactions. To broaden photoactivation modalities, here we report a new strategy in which the fluorophore is generated in situ through an intramolecular tetrazole-alkene cycloaddition reaction (“photoclick chemistry”). By conjugating a specific microtubule-binding taxoid core to the tetrazole/alkene pre-fluorophores, robust photoactivatable fluorescent probes were obtained with fast photoactivation (~1 min) and high fluorescence turn-on ratio (up to 112-fold) in acetonitrile/PBS (1:1). Highly efficient photoactivation of the taxoid-tetrazoles inside the mammalian cells was also observed under a confocal fluorescent microscope when the treated cells were exposed to either a mercury lamp light passing through a 300/395 filter or a 405 nm laser beam. Furthermore, a spatially controlled fluorescent labeling of microtubules in live CHO cells was demonstrated with a long-wavelength photoactivatable taxoid-tetrazole probe. Because of its modular design and tunability of the photoactivation efficiency and photophysical properties, this intramolecular photoclick reaction based approach should provide a versatile platform for designing photoactivatable fluorescent probes for various biological processes.

Yu, Zhipeng; Ho, Lok Yin; Lin, Qing

2011-01-01

293

Fluorescent sensor based on a novel conjugated polyfluorene derivative.  

PubMed

A novel water-soluble polyfluorene derivative, poly[(9,9-bis(3'-((N,N-dimethylamino)N-ethylammonium)propyl)-2,7-fluorene)-alt-2,7-(9,9-p-divinylbenzene)]dibromide (P-2) was synthesized by the palladium-catalyzed Suzuki coupling reaction and it's quaternized ammonium polyelectrolyte derivatives was obtained through a postpolymerization treatment on the terminal amino groups. The electrochemical and optical properties of the copolymers was fully investigated. The results showed that the new polyfluorene derivative had high electronic conductivity and strong fluorescence, therefore it had good potential to be used in chemical and biological sensors, as shown in optical sensing of bovine albumin (BSA) in this study. PMID:22634413

Gao, Weiqiang; Yan, Mei; Ge, Shenguang; Liu, Xiaoxia; Yu, Jinghua

2012-09-01

294

Fluorescent sensor based on a novel conjugated polyfluorene derivative  

NASA Astrophysics Data System (ADS)

A novel water-soluble polyfluorene derivative, poly[(9,9-bis(3'-((N,N-dimethylamino)N-ethylammonium)propyl)-2,7-fluorene)-alt-2,7-(9,9-p-divinylbenzene)]dibromide (P-2) was synthesized by the palladium-catalyzed Suzuki coupling reaction and it's quaternized ammonium polyelectrolyte derivatives was obtained through a postpolymerization treatment on the terminal amino groups. The electrochemical and optical properties of the copolymers was fully investigated. The results showed that the new polyfluorene derivative had high electronic conductivity and strong fluorescence, therefore it had good potential to be used in chemical and biological sensors, as shown in optical sensing of bovine albumin (BSA) in this study.

Gao, Weiqiang; Yan, Mei; Ge, Shenguang; Liu, Xiaoxia; Yu, Jinghua

2012-09-01

295

A fluorescence-based screen for ribosome binding antibiotics  

PubMed Central

The development of new antibacterial agents has become necessary to treat the large number of emerging bacterial strains resistant to current antibiotics. Despite the different methods of resistance developed by these new strains, the A-site of the bacterial ribosome remains an attractive target for new antibiotics. To develop new drugs that target the ribosomal A-site, a high-throughput screen is necessary to identify compounds that bind to the target with high affinity. To this end, we present an assay that uses a novel fluorescein-conjugated neomycin (F-neo) molecule as a binding probe to determine the relative binding affinity of a drug library. We show here that the binding of F-neo to a model Escherichia coli ribosomal A-site results in a large decrease in the fluorescence of the molecule. Furthermore, we have determined that the change in fluorescence is due to the relative change in the pKa of the probe resulting from the change in the electrostatic environment that occurs when the probe is taken from the solvent and localized into the negative potential of the A-site major groove. Finally, we demonstrate that F-neo can be used in a robust, highly reproducible assay, determined by a Z?-factor greater than 0.80 for 3 consecutive days. The assay is capable of rapidly determining the relative binding affinity of a compound library in a 96-well plate format using a single channel electronic pipette. The current assay format will be easily adaptable to a high-throughput format with the use of a liquid handling robot for large drug libraries currently available and under development.

Watkins, Derrick; Norris, F.A.; Kumar, Sunil; Arya, Dev P.

2014-01-01

296

Simple, rapid, and sensitive determination of beta-blockers in environmental water using dispersive liquid-liquid microextraction followed by liquid chromatography with fluorescence detection.  

PubMed

A novel method, dispersive liquid-liquid microextraction combined with liquid chromatography-fluorescence detection is proposed for the determination of three beta-blockers (metoprolol, bisoprolol, and betaxolol) in ground water, river water, and bottled mineral water. Some important parameters, such as the kind and volume of extraction and dispersive solvents, extraction time, pH, and salt effect were investigated and optimized. In the method, a suitable mixture of extraction solvent (60 ?L carbon tetrachloride) and dispersive solvent (1 mL acetonitrile) were injected into the aqueous samples (5.00 mL) and the cloudy solution was observed. After centrifugation, the enriched analytes in the bottom CCl(4) phase were determined by liquid chromatography with fluorescence detection. Under the optimum conditions, the enrichment factors (EFs) for metoprolol, bisoprolol, and betaxolol were 180, 190, and 182, and the limits of detection (LODs) were 1.8, 1.4, and 1.0 ng L(-1) , respectively. A good linear relationship between the peak area and the concentration of analytes was obtained in the range of 3-150 ng L(-1) . The relative standard deviations (RSDs) for the extraction of 10 ng L(-1) of beta-blockers were in the range of 4.6-5.7% (n = 5). Compared with other methods, dispersive liquid-liquid microextraction is a very simple, rapid, sensitive (low limit of detection), and economical (only 1.06 mL volume of organic solvent) method, which is in compliance with the requirements of green analytical methodologies. PMID:22887596

Parrilla Vázquez, María del Mar; Parrilla Vázquez, Piedad; Martínez Galera, Maria; Molina Sánchez, Luis

2012-09-01

297

A novel fluorescent assay for oxytetracycline hydrochloride based on fluorescence quenching of water-soluble CdTe nanocrystals.  

PubMed

A novel assay for oxytetracycline hydrochloride (OTC) based on fluorescence quenching was developed from the interaction between functionalized cadmium telluride quantum dots (CdTe QDs) and OTC. Optimum conditions for the detection of OTC were found after investigating all factors. Under optimum conditions, luminescence of CdTe nanocrystals (? ex = 365 nm, ? em = 562 nm) was quenched by OTC in a concentration-dependent manner best described by a modified Stern-Volmer type equation. Good linearity was obtained with a regression coefficient of 0.9999 in the range of 1.34 ~ 13.4 x 10(-5) mol/L and a limit of detection of 3.08 x 10(-7) mol/L. In addition, the quenching mechanism was also established. The results imply that the close proximity of OTC-CdTe was driven by electrostatic attraction and the resulting effective electron transfer from OTC to QDs could be responsible for fluorescence quenching of CdTe-QDs. PMID:22715152

Gao, Chao; Liu, Zhen; Chen, Jianqiu; Yan, Zhengyu

2013-01-01

298

Characterization of photophysical and base-mimicking properties of a novel fluorescent adenine analogue in DNA  

PubMed Central

To increase the diversity of fluorescent base analogues with improved properties, we here present the straightforward click-chemistry-based synthesis of a novel fluorescent adenine-analogue triazole adenine (AT) and its photophysical characterization inside DNA. AT shows promising properties compared to the widely used adenine analogue 2-aminopurine. Quantum yields reach >20% and >5% in single- and double-stranded DNA, respectively, and show dependence on neighbouring bases. Moreover, AT shows only a minor destabilization of DNA duplexes, comparable to 2-aminopurine, and circular dichroism investigations suggest that AT only causes minimal structural perturbations to normal B-DNA. Furthermore, we find that AT shows favourable base-pairing properties with thymine and more surprisingly also with normal adenine. In conclusion, AT shows strong potential as a new fluorescent adenine analogue for monitoring changes within its microenvironment in DNA.

Dierckx, Anke; Diner, Peter; El-Sagheer, Afaf H.; Kumar, Joshi Dhruval; Brown, Tom; Gr?tli, Morten; Wilhelmsson, L. Marcus

2011-01-01

299

Characterization and use of an unprecedentedly bright and structurally non-perturbing fluorescent DNA base analogue.  

PubMed

This article presents the first evidence that the DNA base analogue 1,3-diaza-2-oxophenoxazine, tC(O), is highly fluorescent, both as free nucleoside and incorporated in an arbitrary DNA structure. tC(O) is thoroughly characterized with respect to its photophysical properties and structural performance in single- and double-stranded oligonucleotides. The lowest energy absorption band at 360 nm (epsilon = 9000 M(-1) cm(-1)) is dominated by a single in-plane polarized electronic transition and the fluorescence, centred at 465 nm, has a quantum yield of 0.3. When incorporated into double-stranded DNA, tC(O) shows only minor variations in fluorescence intensity and lifetime with neighbouring bases, and the average quantum yield is 0.22. These features make tC(O), on average, the brightest DNA-incorporated base analogue so far reported. Furthermore, it base pairs exclusively with guanine and causes minimal perturbations to the native structure of DNA. These properties make tC(O) a promising base analogue that is perfectly suited for e.g. photophysical studies of DNA interacting with macromolecules (proteins) or for determining size and shape of DNA tertiary structures using techniques such as fluorescence anisotropy and fluorescence resonance energy transfer (FRET). PMID:18003656

Sandin, Peter; Börjesson, Karl; Li, Hong; Mårtensson, Jerker; Brown, Tom; Wilhelmsson, L Marcus; Albinsson, Bo

2008-01-01

300

Development of optical phantoms for use in fluorescence-based imaging  

NASA Astrophysics Data System (ADS)

We fabricated permanent solid polyurethane-based phantoms in which fluorophores were homogeneously incorporated. For this study, fluorophores of three different families were used: Cyanines, Alexa Fluor and Quantum Dots. The goal of this study was to evaluate the impact of casting the fluorophores in a polyurethane matrix on their optical properties, more specifically the absorbance, molecular extinction coefficient, emission of fluorescence and the resultant fluorescence intensity. All measurements were carried out with 5 concentrations of each fluorophores embedded in polyurethane and in solution. Stability over time was also monitored for a three months period. The casting of fluorophores affects the optical properties of the three dyes under study. The max absorbance, the fluorescence emission and intensity along with the molar extinction coefficient were all affected. Quantum dots behave differently to the cyanine and Alexa Fluor dyes. It was also observed that the incorporation of dyes enables long-term stability of the fluorescence signal.

Noiseux, Isabelle; Fortin, Michel; Leclair, Sébastien; Osouf, Jocelyne; Mermut, Ozzy

2010-02-01

301

Rosamine-based fluorescent chemosensor for selective detection of silver(I) in an aqueous solution.  

PubMed

The synthesis and photophysical properties of a rosamine-based fluorescent chemosensor, RosAg, for detecting Ag ion in an aqueous solution are described. This fluorescent sensor has a negligible quantum yield (<0.005) in the absence of Ag(+), whereas a significant increase in fluorescence is observed upon complexation with Ag(+) under physiological conditions. The crystal structure of the silver complex with the chelator moiety of RosAg reveals a trigonal-planar coordination geometry in which three S atoms occupy the metal center. Although a strong coordinative interaction of Ag-N is not observed in the crystal structure, the (1)H NMR experiments suggest that aniline nitrogen is likely to be associated with the Ag(+) center in the solution state. This may inhibit the photoinduced electron transfer process and result in the enhancement of fluorescence. PMID:18433117

Iyoshi, Shohei; Taki, Masayasu; Yamamoto, Yukio

2008-05-19

302

Visualizing Hg2+ ions in living cells using a FRET-based fluorescent sensor  

NASA Astrophysics Data System (ADS)

A novel FRET fluorescent sensor for Hg2+ imaging in living cells is rationally designed based on a coumarin-rhodamine platform. RBC1 exhibit high selectivity and excellent sensitivity in both absorbance and fluorescence detection of Hg2+ in aqueous solution. After addition of increasing concentrations of Hg2+, it result in the decrease of coumarin emission at 467 nm and a new emission profile of rhodamine at 590 nm gradually increased. The response time to Hg2+ is less than 2 min, and other metal ions including Fe2+, Mn2+, Ni2+, Co2+, Cu2+, Zn2+, Cd2+, Pb2+, and Cr3+ had no interference. In addition, fluorescent imaging of Hg2+ in A375 cells is also successfully demonstrated. The design strategy of two fluorophores switching in this work would help to extend the development of FRET fluorescent sensors.

Zhou, Yi; Chu, Kaihui; Zhen, Haifu; Fang, Yuan; Yao, Cheng

2013-04-01

303

Long wavelength fluorescence based biosensors for in vivo continuous monitoring of metabolites  

NASA Astrophysics Data System (ADS)

The early stage development studies of novel implantable continuous metabolite sensor systems for glucose, lactate and fatty acids are discussed. These sensors utilize non-enzymatic "reagentless" sensor systems based on NIR fluorophore-labeled binding proteins. For in vivo applications, NIR fluorescence based systems (beyond 600 nm) have the added benefit of reduced interference from background scattering, tissue and serum absorption and cell auto-fluorescence. The long wavelength emission facilitates implanted sensor disks to transmit fluorescence to an external reader through wireless connections and the resulting fluorescence signals can be correlated to metabolite concentrations. We have developed a prototype optical system that uses a bifurcated optical fiber to transmit excitation and read emission at the surface of the skin. With this system, fluorescence signals were read over time through animal skin. The changes in glucose concentration were studied using immobilized sensor proteins and were compared to non-immobilized sensors in solution. For sensors in solution, no response delay was observed. For immobilized systems, the fluorescence response showed a delay corresponding to the diffusion time for the metabolite to equilibrate within the sensor.

Thomas, Joseph; Ambroise, Arounaguiry; Birchfield, Kara; Cai, Wensheng; Sandmann, Christian; Singh, Sarabjit; Weidemaier, Kristin; Pitner, J. Bruce

2006-03-01

304

Detection of membrane biointeractions based on fluorescence superquenching.  

PubMed

Assays for biointeractions of molecules with supported lipid bilayers using fluorescence superquenching are described. A conjugated cationic polymer was adsorbed on to silica microspheres, which were then coated with an anionic lipid bilayer. The lipid bilayer attenuated superquenching by acting as a barrier between the conjugated polymer and its quencher. Biointeractions of the lipid bilayer with a membrane lytic peptide, melittin, were detected and quantitated by superquenching of the conjugated polyelectrolyte in flow cytometric and microfluidic bioassays. A higher sensitivity for detecting melittin lysis of the lipid bilayer at lower concentrations and shorter times for melittin action was found using flow cytometry in this study in comparison to other existing methods. This study combined the sensitivity of superquenching and flow cytometry to detect biointeractions with a lipid bilayer, which serves as a platform for developing functional assays for sensor applications, lipid enzymology, and investigations of molecular interactions. In addition, this study demonstrated proof-of-concept for using superquenching detected as a result of lipid bilayer disruption in a microfluidic format. PMID:18302435

Zeineldin, Reema; Piyasena, Menake E; Sklar, Larry A; Whitten, David; Lopez, Gabriel P

2008-04-15

305

A fast reconstruction method for fluorescence molecular tomography based on improved iterated shrinkage  

NASA Astrophysics Data System (ADS)

Fluorescence molecular tomography (FMT) has become a promising imaging modality for in vivo small animal molecular imaging, and has many successful applications. This is partly due to the wealth of the fluorescent probes. By labeling the regions of interest with fluorescent probes, FMT can achieve non-invasive investigation of the biological process by localizing the targeted probes based on certain inverse mathematical models. However, FMT is usually an illposed problem, and some form of regularization should be included to stabilize the problem, which can be considered as the a priori information of the fluorescent probe bio-distribution. When FMT is used for the early detection of tumors, an important characteristic is the sparsity of the fluorescent sources. This is because tumors are usually very small and sparse at this stage. Considering this, general sparsity-promoting Lp-norm regularization is utilized in this paper. The iterated shrinkage based reconstruction method is adopted to solve the general Lp regularization problem. However, the original iterated shrinkage method is proved to have a linear convergence rate, and a large number of iterations are needed to obtain satisfactory results. In this paper, an improved iterated shrinkage based FMT reconstruction algorithm is proposed. By using the solutions from two previous iterations to determine the current solution, the convergence rate can be greatly increased. Heterogeneous simulation experiment shows that the proposed method can obtain comparable results with greatly reduced number of iterations compared with the original iterated shrinkage based method, which makes it a practical reconstruction algorithm.

Han, Dong; Tian, Jie; Qin, Chenghu; Zhang, Bo; Liu, Kai; Ma, Xibo

2011-03-01

306

Optical detection of DNA hybridization based on fluorescence quenching of tagged oligonucleotide probes by gold nanoparticles  

Microsoft Academic Search

A novel system for the detection of DNA hybridization in a homogeneous format is developed. This method is based on fluorescence quenching by gold nanoparticles used as both nanoscaffolds for the immobilization of capture sequences and nanoquenchers of fluorophores attached to detection sequences. The oligonucleotide-functionalized gold nanoparticles are synthesized by derivatizing the colloidal gold solution with 5?-thiolated 12-base oligonucleotides. Introduction

Zai-Sheng Wu; Jian-Hui Jiang; Li Fu; Guo-Li Shen; Ru-Qin Yu

2006-01-01

307

A novel synchronous fluorescence spectroscopic approach for the rapid determination of three polycyclic aromatic hydrocarbons in tea with simple microwave-assisted pretreatment of sample.  

PubMed

Many polycyclic aromatic hydrocarbons (PAHs) are carcinogenic, and some have been reported to be present in tea. People can be exposed to PAHs through tea consumption. Therefore, there is real importance for the determination of PAHs in tea. Because of the complex matrix of tea, it is hard to detect PAHs in tea without cleanup and chromatographic separation procedures. In this research, for the first time, a novel synchronous fluorescence spectroscopic approach coupling nonlinear variable-angle synchronous and matrix-isopotential synchronous scanning modes has been developed for the rapid determination of benzo(a)pyrene (BaP), benzo(k)fluoranthene (BkF), and anthracene (AN) in tea with simple microwave-assisted pretreatment of samples. This novel technique is able to resolve the spectra of the three PAHs well, even with interference from other EPA PAHs. The detection limits for BaP, BkF, and AN in tea were 0.18-0.28, 0.55-0.89, and 0.64-3.58 ?g/kg, respectively, depending on various teas, with satisfactory recoveries ranging from 77.1 to 116%. The relative standard deviations achieved for BaP, BkF, and AN were 1.5, 6.6, and 8.5% for green tea; 2.9, 7.4, and 2.1% for oolong tea; and 5.6, 5.4, and 5.8% for black tea, respectively. Our results showed good correlation with those of gas chromatography-mass spectrometry. The approach developed is simple, reliable, and cost-efficient, providing an attractive alternative for the rapid selective screening of PAHs in tea. PMID:21520950

Li, Xiu-Ying; Li, Na; Luo, He-Dong; Lin, Li-Rong; Zou, Zhe-Xiang; Jia, Yu-Zhu; Li, Yao-Qun

2011-06-01

308

A unique fluorescent base analogue for the expansion of the genetic alphabet.  

PubMed

Fluorescent nucleobase analogues are useful in a wide variety of biology and biotechnology tools as molecular probes and reporters for nucleic acids. Here we present a novel fluorescent purine analogue, 7-(2,2'-bithien-5-yl)-imidazo[4,5-b]pyridine (denoted as Dss). The nucleoside triphosphates of Dss can be site-specifically incorporated into DNA and RNA by polymerases, opposite its pairing partner, pyrrole-2-carbaldehyde (Pa), in DNA templates. Despite its high specificity in replication and transcription, Dss in oligonucleotides functions as a universal base that pairs with all four natural bases with nearly equal thermal stabilities. Thus, Dss would be a powerful tool for fluorescent base replacements at specific positions in functional DNA and RNA molecules. PMID:20334374

Kimoto, Michiko; Mitsui, Tsuneo; Yokoyama, Shigeyuki; Hirao, Ichiro

2010-04-14

309

Simple Measurement of 4,4’-bis(2-sulfostyryl)-biphenyl in River Water by Fluorescence Analysis and Its Application as an Indicator of Domestic Wastewater Contamination  

Microsoft Academic Search

A characteristic peak of fluorescent whitening agents (FWAs) was detected by fluorescence excitation spectrum (FES) measurement\\u000a of river water samples. The main causative chemical was 4,4’-bis(2-sulfostyryl)-biphenyl (DSBP), which is commonly added to\\u000a household detergents in Japan. As the fluorescence of DSBP overlaps with that of fulvic-like organic matter in the spectral\\u000a fluorescent signatures, DSBP concentration was determined by the newly

Motoyuki Takahashi; Kiyoshi Kawamura

2007-01-01

310

A colormetric and fluorescent chemosensor for adenosine-5'-triphosphate based on rhodamine derivative.  

PubMed

A rhodamine spirolactam derivative (1) was developed as a colormetric and fluorescent chemosensor for adenosine-5'-triphosphate (ATP) via hydrogen bonds interaction. As far as we know, this is the first case to explore ATP-induced ring-opening of spirolactam in rhodamine derivatives. It exhibited a highly sensitive "turn-on" fluorescent response toward ATP with a 47-fold fluorescence intensity enhancement under 20 equiv. of ATP added. The chemosensor can be applied to the quantification of ATP with a linear range covering from 1.0×10(-7) to 2.0×10(-4) M and a detection limit of 2.5×10(-8) M. The experiment results show that the response behavior of 1 toward ATP is pH independent in medium condition (pH 6.0-8.0). Most importantly, the novel chemosensor has well solved the problem of serious interferences from other nucleoside polyphosphates such as ADP and AMP generally met by previously reported typical fluorescent chemosensors for ATP. Moreover, the response of the chemosensor toward ATP is fast (response time less than 3 min). In addition, the chemosensor can be used for the fluorescence assay for protein kinase activity with satisfactory results. The chemosensor for ATP based on hydrogen bonds interaction provided a novel strategy for the design of colormetric and ratiometric fluorescent probes for other target anions with high sensitivity and selectivity. PMID:23998539

Li, Chun-Yan; Zou, Chun-Xiang; Li, Yong-Fei; Kong, Xue-Fei; Zhou, Yu; Wu, Yin-Shuang; Zhu, Wei-Guo

2013-09-17

311

Mast-cell-based fluorescence biosensor for rapid detection of major fish allergen parvalbumin.  

PubMed

In this study, we developed a rat basophilic leukemia cell (RBL-2H3) fluorescence sensor to detect and identify the major fish allergen parvalbumin (PV). We constructed and transfected a CD63-enhanced green fluorescent protein (EGFP) plasmid into RBL cells through a highly efficient, lipid-mediated, DNA-transfection procedure. Stable transfectant RBL cells were then obtained for a cell fluorescence assay with confocal laser scanning microscopy. Results show that the cell surface expression of CD63 reflects degranulation, indicating that a fluorescence assay with these cells could efficiently measure the activation of antigen-stimulated transfectant cells and detect antigens with a nanogram level. Therefore, this cell-based fluorescence biosensor technique for detecting fish PV exhibits promise for quantifying fish PV after anti-PV immunoglobulin E (IgE) stimulation. Results show that fluorescence intensities increased with purified PV concentrations from 1 to 100 ng/mL, with a detection limit of 0.35 ng/mL [relative standard deviation (RSD) of 4.5%], confirmed by ?-hexosaminidase assays. These rat basophilic leukemia (RBL) mast cells transfected with the CD63-EGFP gene and responded to PV only when they were sensitized with the specific IgE antibody. This demonstrates the utility of this highly sensitive biosensor for food allergen detection and prediction. PMID:24901676

Jiang, Donglei; Jiang, Hui; Ji, Jian; Sun, Xiulan; Qian, He; Zhang, Genyi; Tang, Lili

2014-07-01

312

Modulation of a solid-state reversible fluorescent photoswitching based on a controllable photochromic pyrazolones  

NASA Astrophysics Data System (ADS)

A novel solid-state reversible fluorescence photoswitching system (FPS) based on photochromism of photochromic pyrazolones has been developed by employing phosphor Sr2P2O7 co-doped with europium ion and chlorine ion (Sr2P2O7-EC) and 1,3-diphenyl-4-(3-chlorobenzal)-5-hydroxypyrazole-4-phenylsemicarbazone (1a) as the fluorescence dye and the photochromic compound, respectively. With carefully selected components, the absorption band of the keto-form photochromic pyrazolones well overlaps with the emission peak of Sr2P2O7-EC. The fluorescence emission intensity of Sr2P2O7-EC is efficiently modulated by the photoisomerization of 1a with controlling the exposure time in the solid state. The fluorescence photoswitching system displayed high fluorescence quenching efficiency and remarkable fatigue resistance. It can be repeated 7 cycles without observable the changes of emission intensity. A fluorescence quenching efficiency can be achieved with a reversible colour change from white to yellow.

Liu, Hu; Guo, Jixi; Jia, Dianzeng; Guo, Mingxi; Le, Fuhe; Liu, Lang; Wu, Dongling; Li, Feng

2014-08-01

313

AlGaN-based deep-UV LEDs for fluorescence sensing  

NASA Astrophysics Data System (ADS)

Recent progress in wide-bandgap semiconductor optoelectronics resulted in an appearance of deep-UV light-emitting diodes (LEDs), which can be used for fluorescence excitation in a variety of chemical and biological compounds. We used two generations of AlGaN-based UVTOP series deep ultraviolet LEDs developed by Sensor Electronic Technology, Inc. The peak wavelength of these fully packaged devices is 340 nm and 280 nm, line width at half maximum approximately 10 nm, wall-plug efficiency up to 0.9% and output power in the milliwatt range. The second-generation emitters are shown to have an extremely low level of unwanted long-wavelength emission what is important for fluorescence measurements. The UV LEDs were tested for fluorescence excitation in standard fluorophores (organic dyes), autofluorescent biological compounds (riboflavin, NADH, tryptophan, and tyrosine) and medical specimens (fluid secreted by prostate gland). Fluorescence lifetime measurements in the frequency domain were demonstrated using UVTOP-340 and -280 devices. The output of the LEDs was modulated at frequencies up to 200 MHz by high-frequency current drivers and the phase angle of the fluorescence signal was resolved using a radio-frequency lock-in amplifier. Nanosecond-scaled measurements of fluorescence lifetimes, which are the "fingerprints" of chemical and biological compounds, were demonstrated.

Vitta, Pranciskus; Kurilcik, Natalija; Novickovas, Algirdas; Jursenas, Saulius; Calkauskas, Henrikas; Zukauskas, Arturas; Gaska, Remis

2004-12-01

314

Fluorescence detection system for mineral oil based on charge-coupled devices  

NASA Astrophysics Data System (ADS)

Mineral oil can emit fluorescent when it is initiated by ultraviolet (UV) rays. The mineral oil concentration determination device is designed based on fiber transducer technology and fluorescence analyzing technology. It adopts a pulsed-xenon lamp as an excitation light source, uses a sphere fiber-optics probe to detect fluorescence, implemented optoelectronic conversion of the fluorescence signal and the high speed data acquisition with high-sensitivity array charge-coupled devices(CCD), designes corresponding weak signal process circuits and applies a computer to store and display the signal collected by the CCD. The system realizes the detection of fluorescence character of mineral oil. Experiment indicates that the system has good linear relationship in the range of 0.0-5.1mg/L for the density of mineral oil and a minimum detecting limit of the density is 0.18mg/L. The linear correlation coefficient r is 0.9981 when an excitation wavelength is 330nm and an emission wavelength is 512nm. It can realize the detection of fluorescence of mineral oil effectively.

Lv, Jiangtao; Wang, Yutian; Pan, Zhao

2009-05-01

315

A simple high-throughput method for determination of antiepileptic analogues of ?-aminobutyric acid in pharmaceutical dosage forms using microplate fluorescence reader.  

PubMed

Pregabalin (PGB), gabapentin (GBP), and vigabatrin (VGB) are structural analogues of ?-aminobutyric acid used for the treatment of different forms of epilepsy. Their analytical determination is challenging since these molecules have no significant UV or visible absorption. Several derivatization methods have been developed and used for their determination in bulk or pharmaceutical dosage forms. We aimed to develop a high- throughput method using a microplate reader with fluorescence detection and simple derivatization with fluorescamine. Obtained method involves derivatization step of only 5 min at room temperature and simultaneous measurements of 96 samples (?ex 395, ?em 476 nm) thus rendering excellent high-throughput analysis. The method was found to be linear with r²>0.998 across investigated analytical ranges of 0.75 to 30.0 µg/mL for PGB, 2.00 to 80.0 µg/mL for GBP, and 1.50 to 60.0 µg/mL for VGB. Intraday and interday precision values did not exceed 4.93%. The accuracy was ranging between 96.6 to 103.5%. The method was also found to be specific since used excipients did not interfere with the method. The robustness study showed that derivatization procedure is more robust than spectrofluorimetric conditions. The developed high-throughput method was successfully applied for determination of drug content and dissolution profiles in pharmaceutical dosage forms of studied antiepileptic drugs. PMID:23856517

Martinc, Boštjan; Vovk, Tomaž

2013-01-01

316

A simple modification of near-infrared photon-to-electron response with fluorescence resonance energy transfer for dye-sensitized solar cells  

NASA Astrophysics Data System (ADS)

Upconversion (UC) Er, Yb-YF3 is introduced into dye-sensitized solar cells (DSSC) through a simple method to investigate the effect of UC particles in photoanode. The utilization of UC phosphor can significantly improve the photocurrent of the cells under both infrared irradiation and sunlight. Fluorescence resonance energy transfer (FRET) and luminescence-mediated energy transfer between UC-YF3 and N719 dye are explored as the main contribution that UC-YF3 made to DSSC. With the multi-efforts of UC-YF3, power conversion efficiency (PCE) of DSSC is improved from 5.18% to 6.22%. Besides, Electron transfer between UC-YF3 and TiO2 is found after sintered at 450 °C, and the PCE value of DSSC is improved further (5.34% ? 6.76%). In addition, we explore that UC-YF3 can serve as a scattering material to increase the light absorption capability of the cells and increase the photocurrent of the cells under simulated sunlight irradiation.

Li, Liang; Yang, Yulin; Fan, Ruiqing; Jiang, Yanxia; Wei, Liguo; Shi, Yan; Yu, Jia; Chen, Shuo; Wang, Ping; Yang, Bin; Cao, Wenwu

2014-10-01

317

A PDMS-Based Cylindrical Hybrid Lens for Enhanced Fluorescence Detection in Microfluidic Systems  

PubMed Central

Microfluidic systems based on fluorescence detection have been developed and applied for many biological and chemical applications. Because of the tiny amount of sample in the system; the induced fluorescence can be weak. Therefore, most microfluidic systems deploy multiple optical components or sophisticated equipment to enhance the efficiency of fluorescence detection. However, these strategies encounter common issues of complex manufacturing processes and high costs. In this study; a miniature, cylindrical and hybrid lens made of polydimethylsiloxane (PDMS) to improve the fluorescence detection in microfluidic systems is proposed. The hybrid lens integrates a laser focusing lens and a fluorescence collecting lens to achieve dual functions and simplify optical setup. Moreover, PDMS has advantages of low-cost and straightforward fabrication compared with conventional optical components. The performance of the proposed lens is first examined with two fluorescent dyes and the results show that the lens provides satisfactory enhancement for fluorescence detection of Rhodamine 6G and Nile Red. The overall increments in collected fluorescence signal and detection sensitivity are more than 220% of those without lens, and the detection limits of Rhodamine 6G and Nile red are lowered to 0.01 ?g/mL and 0.05 ?g/mL, respectively. The hybrid lens is further applied to the detection of Nile red-labeled Chlorella vulgaris cells and it increases both signal intensity and detection sensitivity by more than 520%. The proposed hybrid lens also dramatically reduces the variation in detected signal caused by the deviation in incident angle of excitation light.

Lin, Bor-Shyh; Yang, Yu-Ching; Ho, Chong-Yi; Yang, Han-Yu; Wang, Hsiang-Yu

2014-01-01

318

A PDMS-based cylindrical hybrid lens for enhanced fluorescence detection in microfluidic systems.  

PubMed

Microfluidic systems based on fluorescence detection have been developed and applied for many biological and chemical applications. Because of the tiny amount of sample in the system; the induced fluorescence can be weak. Therefore, most microfluidic systems deploy multiple optical components or sophisticated equipment to enhance the efficiency of fluorescence detection. However, these strategies encounter common issues of complex manufacturing processes and high costs. In this study; a miniature, cylindrical and hybrid lens made of polydimethylsiloxane (PDMS) to improve the fluorescence detection in microfluidic systems is proposed. The hybrid lens integrates a laser focusing lens and a fluorescence collecting lens to achieve dual functions and simplify optical setup. Moreover, PDMS has advantages of low-cost and straightforward fabrication compared with conventional optical components. The performance of the proposed lens is first examined with two fluorescent dyes and the results show that the lens provides satisfactory enhancement for fluorescence detection of Rhodamine 6G and Nile Red. The overall increments in collected fluorescence signal and detection sensitivity are more than 220% of those without lens, and the detection limits of Rhodamine 6G and Nile red are lowered to 0.01 ?g/mL and 0.05 ?g/mL, respectively. The hybrid lens is further applied to the detection of Nile red-labeled Chlorella vulgaris cells and it increases both signal intensity and detection sensitivity by more than 520%. The proposed hybrid lens also dramatically reduces the variation in detected signal caused by the deviation in incident angle of excitation light. PMID:24531300

Lin, Bor-Shyh; Yang, Yu-Ching; Ho, Chong-Yi; Yang, Han-Yu; Wang, Hsiang-Yu

2014-01-01

319

Recognition of carboxylate anions and carboxylic acids by selenium-based new chromogenic fluorescent sensor: a remarkable fluorescence enhancement of hindered carboxylates.  

PubMed

A selenium metal-based new fluorescence sensor 5-pivaloylamino-1,2,5-selenodiazolo[3,4-d]pyrimidin-7-(6H)-one (receptor 1) has been reported for the recognition of monocarboxylic acids and carboxylate anions both by UV-vis and fluorescence methods. Receptor 1 recognizes carboxylate anions more than monocarboxylic acids and it is a selective sensor for carboxylates with specially hindered carboxylate anions. The changes of fluorescence intensity are remarkably enhanced with red shift in presence of bulky carboxylate anions. The X-ray crystal structure of receptor 1 with pivalic acid has been reported. PMID:19728733

Goswami, Shyamaprosad; Hazra, Anita; Chakrabarty, Rinku; Fun, Hoong-Kun

2009-10-01

320

A Simple System for Observing Dynamic Phase Equilibrium via an Inquiry-Based Laboratory or Demonstration  

ERIC Educational Resources Information Center

This article describes an activity that can be used as an inquiry-based laboratory or demonstration for either high school or undergraduate chemistry students to provide a basis for understanding both vapor pressure and the concept of dynamic phase equilibrium. The activity includes a simple setup to create a closed system of only water liquid and…

Cloonan, Carrie A.; Andrew, Julie A.; Nichol, Carolyn A.; Hutchinson, John S.

2011-01-01

321

A phosphomolybdic acid anion probe-based label-free, stable and simple electrochemical biosensing platform.  

PubMed

A versatile label-free, stable, low-cost and simple electrochemical biosensing platform has been developed based on a phosphomolybdic acid anion probe by jointly taking advantages of its native electronegativity, electrochemical activity and chemisorption with graphene oxide. PMID:25002408

Wei, Tianxiang; Chen, Yuyun; Tu, Wenwen; Lan, Yaqian; Dai, Zhihui

2014-07-22

322

A simple scheme for delay-tolerant decode-and-forward based cooperative communication  

Microsoft Academic Search

In this paper, we study how to improve the performance of a decode-and-forward protocol based cooperative system over the delay constrained channels. We propose a simple transmission scheme, which makes the cooperative system tolerant of the delays caused by the poor synchronization of the relaying nodes. The proposed scheme is able to provide an improved coding gain in unsynchronized cooperative

Manav R. Bhatnagar; M. Debbah; A. Hjorungnes

2009-01-01

323

Sprite: A Simple, Cheat-Proof, Credit-Based System for Mobile Ad-Hoc Networks  

Microsoft Academic Search

Mobile ad hoc networking has been an active research area for several years. How to stimulate cooperation among selfish mobile nodes, however, is not well addressed yet. In this paper, we propose Sprite, a simple, cheat-proof, credit- based system for stimulating cooperation among selfish nodes in mobile ad hoc networks. Our system provides incentive for mobile nodes to cooperate and

Sheng Zhong; Jiang Chen; Yang Richard Yang

2002-01-01

324

Sprite: A Simple, Cheat-Proof, Credit-Based System for Mobile Ad-Hoc Networks  

Microsoft Academic Search

Abstract— Mobile ad hoc networking has been an active research area for several years. How to stimulate cooperation among selfish mobile nodes, however, is not well addressed yet. In this paper, we propose Sprite, a simple, cheat-proof, credit- based system for stimulating cooperation among selfish nodes in mobile ad hoc networks. Our system provides incentive for mobile nodes to cooperate

Sheng Zhong; Jiang Chen; Yang Richard Yang

2003-01-01

325

A low power topology derived from flyback with active clamp based on a very simple transformer  

Microsoft Academic Search

This paper presents and analyzes a low power (10W) topology derived from flyback with active clamp based on very simple and low cost transformers. The main feature of this flyback topology is that the ratio between magnetizing inductance and the series inductance (leakage or integrated inductor) is very low (around 10\\/1). Operation of the topology is analyzed and several transformer

P. Alou; A. Bakkali; I. Barbero; J. A. Cobos; M. Rascon

2006-01-01

326

A simple scheme to make passwords based on one-way functions much harder to crack  

Microsoft Academic Search

We present a simple scheme that makes guessing passwords based on one-way functions 100 to 1000 times harder. The scheme is easy to program and easy to incrementally add to existing schemes. In particular, there is no need to switch to it all at the same time. Old passwords will still work and have the same security as before (one

Udi Manber

1996-01-01

327

Quantify single nucleotide polymorphism (SNP) ratio in pooled DNA based on normalized fluorescence real-time PCR  

PubMed Central

Background Conventional real-time PCR to quantify the allele ratio in pooled DNA mainly depends on PCR amplification efficiency determination and Ct value, which is defined as the PCR cycle number at which the fluorescence emission exceeds the fixed threshold. Because of the nature of exponential calculation, slight errors are multiplied and the variations of the results seem too large. We have developed a new PCR data point analysis strategy for allele ratio quantification based on normalized fluorescence ratio. Results In our method, initial reaction background fluorescence was determined based upon fitting of raw fluorescence data to four-parametric sigmoid function. After that, each fluorescence data point was first subtracted by respective background fluorescence and then each subtracted fluorescence data point was divided by the specific background fluorescence to get normalized fluorescence. By relating the normalized fluorescence ratio to the premixed known allele ratio of two alleles in standard samples, standard linear regression equation was generated, from which unknown specimens allele ratios were extrapolated using the measured normalized fluorescence ratio. In this article, we have compared the results of the proposed method with those of baseline subtracted fluorescence ratio method and conventional Ct method. Conclusion Results demonstrated that the proposed method could improve the reliability, precision, and repeatability for quantifying allele ratios. At the same time, it has the potential of fully automatic allelic ratio quantification.

Yu, Airong; Geng, Haifeng; Zhou, Xuerui

2006-01-01

328

Facile one-pot synthesis of a polyvinylpyrrolidone-based self-crosslinked fluorescent film.  

PubMed

A polyvinylpyrrolidone (PVP)-based fluorescent film with stable optical properties is successfully prepared in one pot without any additive. The reaction mechanism of ring-opening and self-crosslinking of linear PVP is proposed and demonstrated. The morphologies and the nanostructures of the fluorescent film as well as the unmodified film are investigated. The dye is incorporated into the film networks via covalent linkages, thus leading to the highly stable optical properties. The facile and effective synthesis approach opens a new way for the design of other multi-functional composite materials based on linear PVP. PMID:23401022

Yin, Meizhen; Ye, Yong; Sun, Mengmeng; Kang, Naiwen; Yang, Wantai

2013-04-12

329

Fluorescent probes for Al(III) and Cr(III) based on a photochromic diarylethene bearing a fluorescent rhodamine unit  

Microsoft Academic Search

A sensitive and selective “turn-on” fluorescent probe (compound 1O) was prepared by combining a photochromic diarylethene with a fluorescent rhodamine unit. This compound displays a favorable\\u000a photochromism on alternating irradiation with UV\\/Vis light. Upon addition of Al(III) or Cr(III) to the probe, its color changes\\u000a from colorless to pink, and its fluorescence is markedly enhanced. The probe displays excellent sensitivity

Weijun Liu; Shouzhi Pu; Duohua Jiang; Shiqiang Cui; Gang Liu; Congbin Fan

330

Evaluation of a fluorescence-based method for antibabesial drug screening.  

PubMed

In vitro evaluation of chemotherapeutic agents against Babesia and Theileria parasites has become routine, and the effectiveness of these chemicals is usually determined by comparing the parasitemia dynamics of untreated and treated parasites. Although microscopy is widely used to calculate parasitemia, several disadvantages are associated with this technique. The present study evaluated a fluorescence-based method using SYBR green I stain (SG I) to screen antibabesial agents in in vitro cultures of Babesia bovis. The linearity between relative fluorescence units (RFU) and parasitemia was found to be well correlated with a 0.9944 goodness-of-fit (r(2)) value. Subsequently, 50% inhibitory concentration (IC50) values were calculated for 3 antiprotozoan agents, diminazene aceturate, nimbolide, and gedunin, by this method. For diminazene aceturate and nimbolide, the IC50s determined by the fluorescence-based method (408 nM and 8.13 ?M, respectively) and microscopy (400.3 nM and 9.4 ?M, respectively) were in agreement. Furthermore, the IC50 of gedunin determined by the fluorescence-based method (19 ?M) was similar to the recently described microscopy-based value (21.7 ?M) for B. bovis. Additionally, the Z' factor (0.80 to 0.90), signal-to-noise (S/N) ratio (44.15 to 87.64), coefficient of variation at the maximum signal (%CVmax) (0.50 to 2.85), and coefficient of variation at the minimum signal (%CVmin) (1.23 to 2.21) calculated for the fluorescence method using diminazene aceturate were comparable to those previously determined in malaria research for this assay. These findings suggest that the fluorescence-based method might be useful for antibabesial drug screening and may have potential to be developed into a high-throughput screening (HTS) assay. PMID:24914124

Guswanto, Azirwan; Sivakumar, Thillaiampalam; Rizk, Mohamed Abdo; Elsayed, Shimaa Abd Elsalam; Youssef, Mohamed Ahmed; ElSaid, ElSaid El Shirbini; Yokoyama, Naoaki; Igarashi, Ikuo

2014-08-01

331

Ultrasensitive detection of microRNAs based on hairpin fluorescence probe assisted isothermal amplification.  

PubMed

A hairpin fluorescence probe assisted isothermal amplification strategy was used for microRNAs (miRNAs) detection. The fluorescence hairpin probe was rationally designed by software NUPACK to reduce background signal. This isothermal amplification method consisted of two circuits. The amplification strategy not only could detect miRNA, but also amplified and reversely transcribed miRNA into DNA to enhance the stability of the target. The approach was ultrasensitive and as low as 8.5×10(-15)mol/L miR-Let-7a, corresponding to 8.5×10(-20)mol miR-Let-7a in 10µL, was able to be detected within 20min at 37°C. Moreover, successful detection of miR-Let-7a in a total RNA sample was also achieved. Thus, the rapid, simple, isothermal, and highly sensitive approach should be a promising tool for on-the-spot detection. PMID:24613970

Ma, Cuiping; Liu, Sen; Shi, Chao

2014-08-15

332

A Waveform Distortion Evaluation Method Based on a Simple Half-Cycle RMS Calculation  

Microsoft Academic Search

This paper presents a simple and efficient power-quality (PQ) evaluation method based on the half-cycle root-mean-square (H-RMS) calculation, which can be easily applied to waveform distortions processed from instantaneous values. PQ disturbances, especially related to voltage magnitude variations, can be generally divided into two categories by the measuring method: One is the rms-based PQ events, which include voltage sag, swell,

Soo-Hwan Cho; Chang-Hyun Park; Jonghoon Han; Gilsoo Jang

2012-01-01

333

A simple, powerful 4??\\/? coincidence system based on the pulse-mixing method  

Microsoft Academic Search

An improved version of a simple and powerful 4??\\/? coincidence system based on the pulse-mixing method is described. It is based on the use of extendable dead-times measured by the live-time technique. The coincidence channel is replaced by a “virtual” common channel where pulses coming from both beta and gamma detectors are mixed and counted together. The basic property of

Jacques Bouchard; Bruno Chauvenet

1999-01-01

334

Effect of the Electron Donor\\/Acceptor Orientation on the Fluorescence Transduction Efficiency of the d-PET Effect of Carbazole-Based Fluorescent Boronic Acid Sensors  

Microsoft Academic Search

We have synthesized three new carbazole-based fluorescent boronic acid sensors to investigate the fluorescence transduction efficiency of the novel d-PET effect, in which the fluorophore acts as the electron donor and the protonated amine\\/boronic acid group as the electron acceptor of the photoinduced electron transfer process (PET). Aryl ethynyl groups are attached at the 3,6-position of carbazole (aryl = 4-dimethylaminophenyl

J. Z. Zhao; X. Zhang; Y. B. Wu; S. M. Ji; H. M. Guo; P. Song; K. L. Han; Wanhua Wu; T. D. James

2010-01-01

335

Identification Technology for Three-Dimensional Fluorescence Spectrum of Mineral Oil Based on Lifting Wavelet - Multi-Resolution Orthogonal Multi-Wavelet Network  

Microsoft Academic Search

The fluorescence characteristic spectrums of samples obtained from the parameterization for three-dimensional fluorescence spectrum of mineral oil are diverse, and therefore, the species identification of mineral oil is difficult to be realized through simple formulas when the species identification of mineral oil is conducted by means of three-dimensional fluorescence spectrum technology. In this paper, lifting wavelet is adopted to conduct

Huang Tao; Qin Lele; Chen Shuwang

2009-01-01

336

Beer's-law-based, simple spectral model for direct normal and diffuse horizontal irradiance  

SciTech Connect

A spectral model for cloudless days that uses simple mathematical expressions and tabulated look-up tables to generate direct normal and diffuse horizontal irradiance is presented. The model is based on modifications to previously published simple models and comparisons with rigorous radiative transfer codes. This model is expected to be more accurate and to be applicable to a broader range of atmospheric conditions than previous simple models. The prime significance of this model is its simplicity, which allows it to be used on small desk-top computers. The spctrum produced by this model is limited to 0.3 to 4.0 ..mu..m wavelength with an approximate resolution of 10 nm.

Bird, R.E.

1982-12-01

337

Comparison of classification algorithms based on fluorescence data for the diagnosis of atherosclerosis  

NASA Astrophysics Data System (ADS)

Fluorescence spectroscopy has been reported as a very promising approach for the discrimination between healthy and atherosclerotic arteries, as far as both, the spectral shape and the intensity of the corresponding spectra seem to be useful parameters for the diagnosis, at specific wavelengths. Nevertheless there are some difficulties in the precise diagnosis, mainly between the different categories of atherosclerotic arteries (fibrous, calcified, heavy calcified). These difficulties are based on the one hand on biophysical factors, such as the necessity for the preknowledge of tissue fluorophores or the complexity of tissue optics. On the other hand, different spectral classification algorithms have been used, such as multivariate linear regression, decision plane analysis and Bayesian decision analysis, each one with certain disadvantages. In this work, two different classification algorithms were developed and evaluated. During the first procedure, simple dimensionless functions were formed by the ratio of the intensities at selected wavelengths and the logistic model was used for statistical analysis. Decision surfaces were drawn and it was estimated that the probability of correct classification is 88%. The algorithm correctly discriminates 97% of healthy from diseased samples and 80% of fibrous from calcified coronary arteries. During the second procedure, a proper ratio was selected in the sense that the ratio groups of the populations P1 and P2 might be separated with an essential considerable veracity probability. The separability was confirmed by testing the validity of specific statistical hypotheses. The demonstration has been made by means of the Kolmogorov-Smirnov goodness of fit method. Therefore by applying statistical methods on proper parameters obtained from the specimens spectra, it has been able to automatically classify the arterial specimens into healthy (normal), fibrous, calcified and heavily calcified, with more than 99.9% probability (less than 0.1% confidence interval). The different classifications algorithms are thoroughly discussed and evaluated.

Yova, Dido; Gonis, Helen; Loukas, Spyros; Kassis, Kyriakos A.; Koukoutsis, Elias; Papaodysseus, Constantinos N.

1996-01-01

338

Time resolved laser induced fluorescence measurements: Considerations when using Nd:YAG based system  

NASA Astrophysics Data System (ADS)

Time-resolved laser-induced fluorescence (TR-LIF) and the laser induced breakdown spectroscopy (LIBS) have been shown to be methods which are fast and sensitive to provide information about the constituents in analyzed samples. TR-LIF and LIBS have similar hardware requirements. In this paper, we analyze some characteristics of TR-LIF/LIBS system implemented in our laboratory, considering the fact that the excitation part of the system is based on Nd:YAG laser and Optical Parametric Oscillator (OPO). The laser is more than powerful enough (365 mJ at 1064 nm, variable OPO output >5 mJ) for LIBS, but somehow slow (the length of fundamental laser harmonic output pulse is about 5 ns) for fluorescence measurements in our present area of interest, namely plants and food products. Fortunately, the pulse length of tunable OPO output (320-475 nm) is less then 1 ns, so by means of a correct deconvolution procedure it is possible to measure the fluorescence lifetimes in the range as small as a few nanoseconds. The fluorescence detection part of our system is based on picosecond streak camera. Using the fluorescent dyes (Rhodamine B and Fluorescein) ethanol solutions we verified the analyzing capabilities of our TR-LIF system.

Rabasovic, Maja S.; Sevic, Dragutin; Terzic, Mira; Marinkovic, Bratislav P.

2012-05-01

339

Salen-based chiral fluorescence polymer sensor for enantioselective recognition of ?-hydroxyl carboxylic acids.  

PubMed

(R,R)-Salen-based chiral polymer P-1 was synthesized by the polymerization of 5,5'-((2,5-dibutoxy-1,4-phenylene)bis(ethyne-2,1-diyl))bis(2-hydroxy-3-(piperidin-1-ylmethyl) benzaldehyde (M-1) with (1R,2R)-cyclohexane-1,2-diamine (M-2) via nucleophilic addition- elimination reaction, and (R,R)-salan-based polymer P-2 could be obtained by the reduction reaction of P-1 with NaBH(4). (R,R)-Salen-based chiral polymer P-1 can exhibit greater fluorescence enhancement response toward (l)-?-hydroxyl carboxylic acids, and the value of enantiomeric fluorescence difference ratio (ef) can reach as high as 8.41 for mandelic acid and 6.55 for lactic acid. On the contrary, (R,R)-salan-based chiral polymer P-2 shows obvious fluorescence quenching response toward ?-hydroxyl carboxylic acids. Most importantly, (R,R)-salen-based polymer P-1 can display bright blue fluorescence color change in the presence of (l)-?-hydroxyl carboxylic acids under a commercially available UV lamp, which can be clearly observed by the naked eyes. PMID:22554263

Song, Fengyan; Wei, Guo; Wang, Lu; Jiao, Jiemin; Cheng, Yixiang; Zhu, Chengjian

2012-05-18

340

Simultaneous detection and removal of mercury ions in aqueous solution with fluorescent conjugated polymer-based sensor ensemble.  

PubMed

A water-soluble, sulfur-containing fluorescent conjugated polymer exhibits a visible fluorescence color change for detection of mercury in the presence of thymine. A new concept provides the design of a sensor ensemble using a simple combination method. This strategy avoids the need for complicated design and synthesis of a recognition group, eliminating the tedious synthetic efforts for the preparation of a sensor material. PMID:21661074

Kwon, Na Young; Kim, Daigeun; Son, Ji Hye; Jang, Geun Seok; Lee, Jung Hyo; Lee, Taek Seung

2011-07-15

341

Synthesis of porphyrin-appended terpyridine as a chemosensor for cadmium based on fluorescent enhancement  

Microsoft Academic Search

The design and synthesis of a porphyrin-appended terpyridine, 5-(4-([2,2?:6?,2?]-terpyridin-4-yl-carboxyamidyl)phenyl)-10,15,20-triphenylporphyrin (H2TPPTPy) and its application as potential fluoroionophore for recognition of metal ions are reported. For preparation of the fluoroionophore, a novel simple strategy with improved total yield has been applied for the synthesis of 2,2?:6?,2?-terpyridine-4?-carboxylic acid as a ligand. H2TPPTPy shows chelation-enhanced fluorescence effect with cadmium ion via the interruption of

Hong-Yuan Luo; Jian-Hui Jiang; Xiao-Bing Zhang; Chun-Yan Li; Guo-Li Shen; Ru-Qin Yu

2007-01-01

342

Ratiometric fluorescent nanosensor based on water soluble carbon nanodots with multiple sensing capacities  

NASA Astrophysics Data System (ADS)

A construction strategy for ratiometric fluorescent nanosensors based on water soluble C-dots was developed, which could sense temperature (10-82 °C), pH values (lower than 6.0 or higher than 8.6) and Fe3+ ions (>0.04 ?M) by monitoring the intensity ratios of dual fluorescence bands (Ib/Ig) under 380 nm excitation. Ib/Ig decreased nearly linearly with increasing temperature from 10 to 82 °C. In the pH range from 8.6 to 6.0, the Ib/Ig was nearly constant at 0.75. Ib/Ig gradually decreased from 0.75 to 0.52 in the pH range from 6.0 to 1.9, and increased nearly linearly from 0.52 to 0.75 in the pH range from 1.9 to 1.0. The dual fluorescence behavior was reversible in the pH range from 1.0 to 8.6. As pH increased from 10.6 to 13.0, the green fluorescence band decreased continuously and blue shifted with a nearly linear increase in Ib/Ig from 0.75 to 2.15, while the green fluorescence band cannot be recovered by decreasing the pH value. Ib/Ig was ultrasensitive and selective in presence of Fe3+ (>0.04 ?M) in neutral aqueous environments. The two fluorescence bands of the C-dots were attributed to different surface states that may produce different fluorescent signal responses to external physical or chemical stimuli.A construction strategy for ratiometric fluorescent nanosensors based on water soluble C-dots was developed, which could sense temperature (10-82 °C), pH values (lower than 6.0 or higher than 8.6) and Fe3+ ions (>0.04 ?M) by monitoring the intensity ratios of dual fluorescence bands (Ib/Ig) under 380 nm excitation. Ib/Ig decreased nearly linearly with increasing temperature from 10 to 82 °C. In the pH range from 8.6 to 6.0, the Ib/Ig was nearly constant at 0.75. Ib/Ig gradually decreased from 0.75 to 0.52 in the pH range from 6.0 to 1.9, and increased nearly linearly from 0.52 to 0.75 in the pH range from 1.9 to 1.0. The dual fluorescence behavior was reversible in the pH range from 1.0 to 8.6. As pH increased from 10.6 to 13.0, the green fluorescence band decreased continuously and blue shifted with a nearly linear increase in Ib/Ig from 0.75 to 2.15, while the green fluorescence band cannot be recovered by decreasing the pH value. Ib/Ig was ultrasensitive and selective in presence of Fe3+ (>0.04 ?M) in neutral aqueous environments. The two fluorescence bands of the C-dots were attributed to different surface states that may produce different fluorescent signal responses to external physical or chemical stimuli. Electronic supplementary information (ESI) available: Experimental details, PL spectra of the C-dots in different media and conditions. See DOI: 10.1039/c3nr00619k

Qu, Songnan; Chen, Hong; Zheng, Xuanming; Cao, Junsheng; Liu, Xingyuan

2013-05-01

343

Development of a fluorescence-based microplate method for the determination of volatile fatty acids in anaerobically digested and sewage sludges.  

PubMed

This paper presents a simple, accurate and multi-sample method for the determination of volatile fatty acids (VFAs) thanks to a 96-well microplate technique. A procedure using an activating reagent of the carboxylic function (water-soluble carbodiimide EDC) and a fluorescent amino labeling reagent (N-(1-naphthyl)ethylenediamine, EDAN) allows the formation of an isoindole derivative that needs to be separated from initial fluorescent amine for efficient VFAs determination. Isolation of these fluorescent VFA-derivatives was carried out by use of the fluorescent quenching of EDAN with o-phthaldialdehyde (OPA). Quenching was most efficient at pH around 7 and by heating at 40°C within the microplate reader. This optimized procedure has been applied to various carboxylic acids and other organic compounds, demonstrating that VFA exhibit the highest fluorescence responses with homogeneous results for the main ones (acetic, propionic and butyric acid, all mass concentration expressed as acetic acid equivalents). This protocol was calibrated against acetic acid and determination of VFA was thus possible in the range 3.9-2,000 mg L(-1) (acetic acid equivalents). Subsequent application to real samples (sewage sludges or anaerobically digested samples) and comparison to gas chromatography analyses gave accurate results, proving the great potential of our high-throughput microplate-based technique for the analysis of VFA. PMID:22265492

Robert-Peillard, F; Palacio-Barco, E; Coulomb, B; Boudenne, J L

2012-01-15

344

A Study of Boronic Acid Based Fluorescent Glucose Sensors  

Microsoft Academic Search

Boronic acid based anthracene dyes were designed, synthesized, and immobilized to solid phase, creating a continuous glucose sensor. Glucose sensitivities of dyes can decrease drastically after immobilization, therefore how to immobilize a dye to solid phase without changing the dye property is a key issue in developing the sensor. The glucose sensitivity of the simplest 1st generation sensor, which is

T. Kawanishi; M. A. Romey; P. C. Zhu; M. Z. Holody; S. Shinkai

2004-01-01

345

Anion recognition by simple chromogenic and chromo-fluorogenic salicylidene Schiff base or reduced-Schiff base receptors.  

PubMed

This review contains extensive application of anion sensing ability of salicylidene type Schiff bases and their reduced forms having various substituents with respect to phenolic OH group. Some of these molecular systems behave as receptor for recognition or sensing of various anions in organic or aqueous-organic binary solvent mixture as well as in the solid supported test kits. Development of Schiff base or reduced Schiff base receptors for anion recognition event is commonly based on the theory of hydrogen bonding interaction or deprotonation of phenolic -OH group. The process of charge transfer (CT) or inhibition of excited proton transfer (ESIPT) or followed by photo-induced electron transfer (PET) lead to naked-eye color change, UV-vis spectral change, chemical shift in the NMR spectra and fluorescence spectral modifications. In this review we have tried to discuss about the anion sensing properties of Schiff base or reduced Schiff base receptors. PMID:24759755

Dalapati, Sasanka; Jana, Sankar; Guchhait, Nikhil

2014-08-14

346

Depth resolution and multiexponential lifetime analyses of reflectance-based time-domain fluorescence data  

NASA Astrophysics Data System (ADS)

Time-domain fluorescence imaging is a powerful new technique that adds a rich amount of information to conventional fluorescence imaging. Specifically, time-domain fluorescence can be used to remove autofluorescence from signals, resolve multiple fluorophore concentrations, provide information about tissue microenvironments, and, for reflectance-based imaging systems, resolve inclusion depth. The present study provides the theory behind an improved method of analyzing reflectance-based time-domain data that is capable of accurately recovering mixed concentration ratios of multiple fluorescent agents while also recovering the depth of the inclusion. The utility of the approach was demonstrated in a number of simulations and in tissuelike phantom experiments using a short source--detector separation system. The major findings of this study were (1) both depth of an inclusion and accurate ratios of two-fluorophore concentrations can be recovered accurately up to depths of approximately 1cm with only the optical properties of the medium as prior knowledge, (2) resolving the depth and accounting for the dispersion effects on fluorescent lifetimes is crucial to the accuracy of recovered ratios, and (3) ratios of three-fluorophore concentrations can be resolved at depth but only if the lifetimes of the three fluorophores are used as prior knowledge. By accurately resolving the concentration ratios of two to three fluorophores, it may be possible to remove autofluorescence or carry out quantitative techniques, such as reference tracer kinetic modeling or ratiometric approaches, to determine receptor binding or microenvironment parameters in point-based time-domain fluorescence applications.

Tichauer, Kenneth M.; Migueis, Mark; Leblond, Frederic; Elliott, Jonathan T.; Diop, Mamadou; St. Lawrence, Keith; Lee, Ting-Yim

2011-07-01

347

Ratiometric fluorescent nanosensor based on water soluble carbon nanodots with multiple sensing capacities.  

PubMed

A construction strategy for ratiometric fluorescent nanosensors based on water soluble C-dots was developed, which could sense temperature (10-82 °C), pH values (lower than 6.0 or higher than 8.6) and Fe(3+) ions (>0.04 ?M) by monitoring the intensity ratios of dual fluorescence bands (Ib/Ig) under 380 nm excitation. Ib/Ig decreased nearly linearly with increasing temperature from 10 to 82 °C. In the pH range from 8.6 to 6.0, the Ib/Ig was nearly constant at 0.75. Ib/Ig gradually decreased from 0.75 to 0.52 in the pH range from 6.0 to 1.9, and increased nearly linearly from 0.52 to 0.75 in the pH range from 1.9 to 1.0. The dual fluorescence behavior was reversible in the pH range from 1.0 to 8.6. As pH increased from 10.6 to 13.0, the green fluorescence band decreased continuously and blue shifted with a nearly linear increase in Ib/Ig from 0.75 to 2.15, while the green fluorescence band cannot be recovered by decreasing the pH value. Ib/Ig was ultrasensitive and selective in presence of Fe(3+) (>0.04 ?M) in neutral aqueous environments. The two fluorescence bands of the C-dots were attributed to different surface states that may produce different fluorescent signal responses to external physical or chemical stimuli. PMID:23673389

Qu, Songnan; Chen, Hong; Zheng, Xuanming; Cao, Junsheng; Liu, Xingyuan

2013-06-21

348

Fluorescence Assay Based on Aptamer-Quantum Dot Binding to Bacillus thuringiensis Spores.  

National Technical Information Service (NTIS)

A novel assay was developed for the detection of Bacillus thuringiensis (BT) spores. The assay is based on the fluorescence observed after binding an aptamer-quantum dot conjugate to BT spores. The in vitro selection and amplification technique called SEL...

A. Allman J. G. Bruno M. Ikanovic M. P. Carrillo W. E. Rudzinski

2007-01-01

349

A ratiometric fluorescent probe for determining Pd2+ ions based on coordination.  

PubMed

An aniline-rhodamine-based ratiometric fluorescent probe (RI) was designed and synthesized. , the metal coordinating chromophoric ligand, exhibited high selectivity and sensitivity for Pd(2+) ions with a detection limit of 73.8 nM. This method of Pd(2+) detection had a 10 min response time. PMID:24500515

Qiao, Bo; Sun, Shiguo; Jiang, Na; Zhang, Si; Peng, Xiaojun

2014-03-28

350

A microfluidic chip for measurement of biomolecules using a microbead-based quantum dot fluorescence assay  

Microsoft Academic Search

This paper describes a custom-designed microfluidic chip for sensitive detection of antibody using quantum dot fluorescence in a microbead-based assay. The microfluidic chip is designed to isolate a single microbead where the binding reaction of antibodies happens on the surface. The microfluidic chip is fabricated on a glass substrate using transparent silicone elastomer, PDMS, for easy access to monitoring and

Kwang-Seok Yun; Dohoon Lee; Hak-Sung Kim; Euisik Yoon

2006-01-01

351

Microfluidic Chips Designed for Measuring Biomolecules Through a Microbead-Based Quantum Dot Fluorescence Assay  

Microsoft Academic Search

This chapter introduces the demonstration of specific antibody detection by using a microbead-based assay with quantum dot (QD) fluorescence on a polydimethylsiloxane (PDMS) microfluidic chip. The microfluidic chip is designed to isolate a single microbead where the binding reaction of antibodies occurs on the surface. The microfluidic chip is fabricated on a glass substrate using a transparent silicone elastomer, PDMS,

Kwang-Seok Yun; Dohoon Lee; Hak-Sung Kim; Euisik Yoon

2009-01-01

352

Highly sensitive fluorescence resonance energy transfer (FRET)-based nanosensor for rapid detection of clenbuterol  

Microsoft Academic Search

In this study we investigate the fabrication of a fluorescence resonance energy transfer (FRET)-based nanosensor for the detection of clenbuterol. The nanosensor consists of CdTe quantum dots coated by clenbuterol recognizable agent naphthol and diazotized clenbuterol. Changes in maximal photoluminescent intensities of the nanosensor were utilized to measure clenbuterol concentrations. The maximal photoluminescent intensities of the nanosensor were found to

Duc Nghia Nguyen; Trinh Tung Ngo; Quang Liem Nguyen

2012-01-01

353

Optimization of oxygen sensitive optical dye membrane polymers for fluorescent-lifetime-based physiological biosensing  

Microsoft Academic Search

Fiber optic based sensor technologies have many significant advantages over electrochemical sensors, and as a result have broad application for sensing in biology, agriculture and medicine. An important component of fiber optic biosensor is the sensing element. Usually, a polymer matrix containing the analyte specific fluorescent dye is immobilized on one end of the fiber optic probe. The polymer matrix

M. R. Chatni; D. E. Maier; D. M. Porterfield

2007-01-01

354

Background Fluorescence in an Aerosol Biodetector Based on 266-nm Excitation.  

National Technical Information Service (NTIS)

Background fluorescence in an aerosol biodetector based on 266-nm excitation has been investigated, using a gas cell which could be evacuated and then filled with a gas (of interest) at a known pressure. A frequency- quadrupled, Q-switched Nd:YAG microchi...

R. L. Aggarwal

1999-01-01

355

Nucleotide sensing with a perylene-based molecular receptor via amplified fluorescence quenching.  

PubMed

A competitive fluorescence assay of perylene-based molecular receptors has been established, and selective detection of UTP is achieved through improved aggregation arising from the specific interaction of perylene-tethered guanidinium with uridine and phosphate groups in UTP. PMID:24306265

Roy, Bappaditya; Noguchi, Takao; Yoshihara, Daisuke; Tsuchiya, Youichi; Dawn, Arnab; Shinkai, Seiji

2014-01-28

356

Determination of various alcohols based on a new immobilized enzyme fluorescence capillary analysis  

Microsoft Academic Search

A novel method for the determination of ethanol in tequila based on the immobilized enzyme fluorescence capillary analysis (IE-EFCA) has been proposed. Alcohol dehydrogenase (ADH) was immobilized in inner surface of a capillary and an immobilized enzyme capillary bioreactor (IE-ECBR) was formed. After nicotinamide adenine dinucleotide (NAD+) as an oxidizer is mixed with alcohol sample solution, it was sucked into

Yong-Sheng Li; Xiu-Feng Gao

2007-01-01

357

Improved efficiency for white organic light-emitting devices based on phosphor sensitized fluorescence  

Microsoft Academic Search

Efficiency of white organic light-emitting devices (WOLEDs) based on phosphor sensitized fluorescence is improved by using an unusual device structure, in which an undoped blue emissive layer is sandwiched between two phosphorescent doped ones. This blue emissive layer blocks a triplet-triplet energy transfer between the two phosphorescent emissive layers, leading to balanced emissions of blue, green, yellow, and red. Thus,

Gang Cheng; Yingfang Zhang; Yi Zhao; Shiyong Liu; Yuguang Ma

2006-01-01

358

Enhanced fluorescent assignment of protein aggregates by an oligothiophene-porphyrin-based amyloid ligand.  

PubMed

Fluorescent probes identifying protein aggregates are of great interest, as deposition of aggregated proteins is associated with many devastating diseases. Here, we report that a fluorescent amyloid ligand composed of two distinct molecular moieties, an amyloidophilic pentameric oligothiophene and a porphyrin, can be utilized for spectral and lifetime imaging assessment of recombinant A? 1-42 amyloid fibrils and A? deposits in brain tissue sections from a transgenic mouse model with Alzheimer's disease pathology. The enhanced spectral range and distinct lifetime diversity of this novel oligothiophene-porphyrin-based ligand allow a more precise assessment of heterogeneous amyloid morphology compared with the corresponding oligothiophene dye. PMID:23468206

Arja, Katriann; Sjölander, Daniel; Åslund, Alma; Prokop, Stefan; Heppner, Frank L; Konradsson, Peter; Lindgren, Mikael; Hammarström, Per; Åslund, K O Andreas; Nilsson, K Peter R

2013-05-14

359

A design of fluorescent probes for superoxide based on a nonredox mechanism.  

PubMed

Fluorometric detection of O2-* is performed based on desulfonylation of 3 to the corresponding fluoresceins 4 through nucleophilic substitution, and this fluorescing process is quite specific toward O2-* over H2O2, t-BuOOH, NaOCl, 1O2, HO*, NO*, and ONOO-. Furthermore, effects of glutathione, cytochrome P450 reductase/NADPH, and diaphorase/NADH are relatively small on the fluorescing process of probe 3 with X = Y = F, which is useful to detect O2-* released from neutrophils stimulated by phorbol myristate acetate with satisfactory sensitivity. PMID:15631452

Maeda, Hatsuo; Yamamoto, Kayoko; Nomura, Yoko; Kohno, Iho; Hafsi, Leila; Ueda, Noritsugu; Yoshida, Shoko; Fukuda, Masako; Fukuyasu, Yuka; Yamauchi, Yuji; Itoh, Norio

2005-01-12

360

New approach to breast tumor detection based on fluorescence x-ray analysis  

PubMed Central

A new technical approach to breast-tumor detection is proposed. The technique is based on fluorescence x-ray analysis, and can identify a miniature malignant tumor within the breast. The primary beam intensity needed in fluorescence x-ray analysis is on a lower order of magnitude than that used in mammography. Thus, the newly-proposed technique would enable detection of a still tiny breast cancer while dramatically lowering the radiation dose. Field-emission x-ray sources might be a key for translating this concept into a medical technique.

Hayashi, Yasuhiko; Okuyama, Fumio

2010-01-01

361

Selective fluorescence detection of histamine based on ligand exchange mechanism and its application to biomonitoring.  

PubMed

We report on a novel histamine monitoring method by using a fluorescent probe, a complex between Ni(2+) and calcein, based on a ligand exchange mechanism. The fluorescence intensity of this probe, which has been reduced due to effective quenching by Ni(2+) ion, increases drastically by an addition of histamine. Furthermore, the probe shows high selectivity toward histamine among the various neurotransmitters in 0.1M phosphate buffer solution (pH 7.4). Biomonitoring studies to detect histamine released from RAW264 cells are successfully represented. PMID:20450876

Seto, Daisuke; Soh, Nobuaki; Nakano, Koji; Imato, Toshihiko

2010-09-15

362

Molecular distribution sensing in a fluorescence resonance energy transfer based affinity assay for glucose  

NASA Astrophysics Data System (ADS)

A newly developed method for determining molecular distribution functions is applied to a widely researched glucose affinity sensor. The reduction in fluorescence resonance energy transfer (FRET) to a malachite green (MG)-dextran complex from allophycocyanin (APC) bound to concanavalin A (ConA) due to displacement of the complex by glucose from ConA provides the basis of the assay. The higher sensitivity and specificity of a new approach to fluorescence decay analysis, over the methods based on conventional Förster-type models, is demonstrated and critical parameters in competitive binding FRET sensing derived.

Rolinski, O. J.; Birch, D. J. S.; McCartney, L.; Pickup, J. C.

2001-09-01

363

Fluorescent cell-based sensing approaches for toxicity testing  

Microsoft Academic Search

Fluorimetric cell-based sensing methods have attracted increasing interest in toxicity testing of pharmaceuticals, pathogens,\\u000a environmental pollutants, and other chemicals. The objective of this review is to summarise the variety of approaches reported\\u000a up to now and to present recent developments in this area. The different approaches are described in relation to their underlying\\u000a mechanism and, especially, to the role of

Michael Fritzsche; Carl-Fredrik Mandenius

2010-01-01

364

Analysis of lignans from Phyllanthus niruri L. in plasma using a simple HPLC method with fluorescence detection and its application in a pharmacokinetic study.  

PubMed

A simple analytical method using HPLC with fluorescence detection was developed for the simultaneous determination of four lignans, phyllanthin (1), hypophyllanthin (2), phyltetralin (3) and niranthin (4) from Phyllanthus niruri L. in plasma. The method recorded limits of detection for 1, 2, 3 and 4 as 1.22, 6.02, 0.61 and 1.22 ng/ml, respectively, at a signal-to-noise ratio of 5:1 whereas their limits of quantification were 4.88, 24.41, 4.88 and 9.76 ng/ml, respectively, at a signal-to-noise ratio of 12:1. These values were comparable to those of other sensitive methods such as gas chromatography-mass spectrometry (GC-MS), high-performance liquid chromatography-MS (HPLC-MS) and HPLC-electrochemical detection (HPLC-ECD) for the analysis of plasma lignans. A further advantage over known methods was its simple protocol for sample preparation. The within-day and between-day accuracies for the analysis of the four lignans were between 87.69 and 110.07% with precision values below 10.51%. Their mean recoveries from extraction were between 91.39 and 114.67%. The method was successfully applied in the pharmacokinetic study of lignans in rats. Following intravenous administration, the lignans were eliminated slowly from the body with a mean clearance of 0.04, 0.01, 0.03 and 0.02 l/kg h and a mean half-life of 3.56, 3.87, 3.35 and 4.40 h for 1, 2, 3 and 4, respectively. Their peak plasma concentration upon oral administration was 0.18, 0.56, 0.12 and 0.62 microg/ml, respectively, after 1h. However, their absorption was incomplete with a calculated absolute oral bioavailability of 0.62, 1.52, 4.01 and 2.66% for 1, 2, 3 and 4, respectively. PMID:17261384

Murugaiyah, Vikneswaran; Chan, Kit Lam

2007-06-01

365

Thiol reactive probe based on fluorescence resonance energy transfer between fluorescein and Au nanoparticles.  

PubMed

Sensitive and selective fluorescent probe of thiols with lower limit of detection based on fluorescence resonance energy transfer (FRET) between fluorescein and Au nanoparticles (AuNPs) is presented. The fluorescein-AuNPs complex emits weak fluorescence. Upon chemically binding to organosulfur compound that contains a carbon-bonded sulfhydryl (-C-SH or R-SH) thiols, a stable enhancement of fluorescence is observed due to the competitive binding on AuNPs between thiols and fluorescein. The magnitude of fluorescence enhancement is linearly proportional to the logarithm of the thiols concentration. We use cysteine as an example to show how this useful analytical assay works selectively, which is closely nonresponsive to 20 other amino acids even though they are in solution at a concentration 10 times greater than the thiols. The detection limit for cysteine is 7.27 × 10-9 mol L-1. The possible mechanism of this assay is discussed in details. The proposed method was successfully applied for the determination of Cys in urine. PMID:24664329

Qi, Li; Song, Juan; Wu, Fang-Ying; Wan, Yi-Qun

2014-01-01

366

Specific detection of Vibrio parahaemolyticus by fluorescence quenching immunoassay based on quantum dots.  

PubMed

In this study, anti-Vibrio parahaemolyticus polyclonal and monoclonal antibodies were prepared through intradermal injection immune and lymphocyte hybridoma technique respectively. CdTe quantum dots (QDs) were synthesized at pH 9.3, 98 °C for 1 h with stabilizer of 2.7:1. The fluorescence intensity was 586.499, and the yield was 62.43 %. QD probes were successfully prepared under the optimized conditions of pH 7.4, 37 °C for 1 h, 250 ?L of 50 mg/mL EDC?·?HCl, 150 ?L of 4 mg/mL NHS, buffer system of Na2HPO4-citric acid, and 8 ?L of 2.48 mg/mL polyclonal antibodies. As gold nanoparticles could quench fluorescence of quantum dots, the concentration of V. parahaemolyticus could be detected through measuring the reduction of fluorescence intensity in immune sandwich reaction composed of quantum dot probe, gold-labeled antibody, and the sample. For pure culture, fluorescence intensity of the system was proportional with logarithm concentration of antigen, and the correlation coefficient was 99.764 %. The fluorescence quenching immunoassay based on quantum dots is established for the first time to detect Vibrio parahaemolyticus. This method may be used as rapid testing procedure due to its high simplicity and sensitivity. PMID:24756606

Wang, Ling; Zhang, Junxian; Bai, Haili; Li, Xuan; Lv, Pintian; Guo, Ailing

2014-07-01

367

Development of fluorescence based handheld imaging devices for food safety inspection  

NASA Astrophysics Data System (ADS)

For sanitation inspection in food processing environment, fluorescence imaging can be a very useful method because many organic materials reveal unique fluorescence emissions when excited by UV or violet radiation. Although some fluorescence-based automated inspection instrumentation has been developed for food products, there remains a need for devices that can assist on-site inspectors performing visual sanitation inspection of the surfaces of food processing/handling equipment. This paper reports the development of an inexpensive handheld imaging device designed to visualize fluorescence emissions and intended to help detect the presence of fecal contaminants, organic residues, and bacterial biofilms at multispectral fluorescence emission bands. The device consists of a miniature camera, multispectral (interference) filters, and high power LED illumination. With WiFi communication, live inspection images from the device can be displayed on smartphone or tablet devices. This imaging device could be a useful tool for assessing the effectiveness of sanitation procedures and for helping processors to minimize food safety risks or determine potential problem areas. This paper presents the design and development including evaluation and optimization of the hardware components of the imaging devices.

Lee, Hoyoung; Kim, Moon S.; Chao, Kuanglin; Lefcourt, Alan M.; Chan, Diane E.

2013-05-01

368

Enzymatic cascade based fluorescent DNAzyme machines for the ultrasensitive detection of Cu(II) ions.  

PubMed

A novel enzymatic cascade based fluorescent DNAzyme machine has been developed for the amplified detection of copper (Cu(2+)) ions. This is the first attempt to carry out the combination of the self-cleaving DNAzyme and the polymerase/endonuclease reaction cycles involving cleaved substrate extension. In the presence of Cu(2+) ions, the enzyme strand carries out catalytic reactions to hydrolytic cleavage of the substrate strand. The cleaved DNAzyme substrates act as primers and trigger the Klenow Fragment polymerization. Nb.BbvCI endonuclease cuts the double-stranded niking site and thus opens a new site for a new replication. The replication regenerates the complete dsDNA to initiate another cycle of nicking, polymerization and displacement. Finally the fluorescence dye, SG, inserts into the DNA double helix to generate a distinguishable fluorescence enhancement. The Cu(2+) ions act as the activator for enzymatic cascade amplification generating multiple duplex structures in the nascent product. An increasing fluorescence is observed with increasing Cu(2+) ions concentration. A good nonlinear correlation (R=0.9997) was obtained between fluorescence intensity and the cubic logarithm of the Cu(2+) ions concentration over the range 0.50-200nM. This nonlinear response phenomenon results in an efficient improvement of the sensitivity of our current proposed assay. The activation of such enzymatic cascades through analyte-DNAzyme interactions is not only valuable to activate the cooperation of enzyme networks, but also has a substantial impact on the development of amplified DNAzyme sensors. PMID:24787125

He, Jing-Lin; Zhu, Shuang-Li; Wu, Ping; Li, Pan-Pan; Li, Ting; Cao, Zhong

2014-10-15

369

Light sheet-based fluorescence microscopy: more dimensions, more photons, and less photodamage.  

PubMed

Light-sheet-based fluorescence microscopy (LSFM) is a fluorescence technique that combines optical sectioning, the key capability of confocal and two-photon fluorescence microscopes with multiple-view imaging, which is used in optical tomography. In contrast to conventional wide-field and confocal fluorescence microscopes, a light sheet illuminates only the focal plane of the detection objective lens from the side. Excitation is, thus, restricted to the fluorophores in the volume near the focal plane. This provides optical sectioning and allows the use of regular cameras in the detection process. Compared to confocal fluorescence microscopy, LSFM reduces photo bleaching and photo toxicity by up to three orders of magnitude. In LSFM, the specimen is embedded in a transparent block of hydrogel and positioned relative to the stationary light sheet using precise motorized translation and rotation stages. This feature is used to image any plane in a specimen. Additionally, multiple views obtained along different angles can be combined into a single data set with an improved resolution. LSFMs are very well suited for imaging large live specimens over long periods of time. However, they also perform well with very small specimens such as single yeast cells. This perspective introduces the principles of LSFM, explains the challenges of specimen preparation, and introduces the basics of a microscopy that takes advantage of multiple views. PMID:19404438

Reynaud, Emmanuel G; Krzic, Uros; Greger, Klaus; Stelzer, Ernst H K

2008-10-01

370

Light sheet-based fluorescence microscopy: more dimensions, more photons, and less photodamage  

PubMed Central

Light-sheet-based fluorescence microscopy (LSFM) is a fluorescence technique that combines optical sectioning, the key capability of confocal and two-photon fluorescence microscopes with multiple-view imaging, which is used in optical tomography. In contrast to conventional wide-field and confocal fluorescence microscopes, a light sheet illuminates only the focal plane of the detection objective lens from the side. Excitation is, thus, restricted to the fluorophores in the volume near the focal plane. This provides optical sectioning and allows the use of regular cameras in the detection process. Compared to confocal fluorescence microscopy, LSFM reduces photo bleaching and photo toxicity by up to three orders of magnitude. In LSFM, the specimen is embedded in a transparent block of hydrogel and positioned relative to the stationary light sheet using precise motorized translation and rotation stages. This feature is used to image any plane in a specimen. Additionally, multiple views obtained along different angles can be combined into a single data set with an improved resolution. LSFMs are very well suited for imaging large live specimens over long periods of time. However, they also perform well with very small specimens such as single yeast cells. This perspective introduces the principles of LSFM, explains the challenges of specimen preparation, and introduces the basics of a microscopy that takes advantage of multiple views.

Reynaud, Emmanuel G.; Krzic, Uros; Greger, Klaus; Stelzer, Ernst H.K.

2008-01-01

371

Conjugated polyelectrolyte based real-time fluorescence assay for phospholipase C.  

PubMed

A fluorescence turnoff assay for phospholipase C (PLC) from Clostridium perfringens is developed based on the reversible interaction between the natural substrate, phosphatidylcholine, and a fluorescent, water-soluble conjugated polyelectrolyte (CPE). The fluorescence intensity of the CPE in water is increased substantially by the addition of the phospholipid due to the formation of a CPE-lipid complex. Incubation of the CPE-lipid complex with the enzyme PLC causes the fluorescence intensity to decrease (turnoff sensor); the response arises due to PLC-catalyzed hydrolysis of the phosphatidylcholine, which effectively disrupts the CPE-lipid complex. The PLC assay operates with phospholipid substrate concentrations in the micromolar range, and the analytical detection limit for PLC is <1 nM. The optimized assay provides a convenient, rapid, and real-time sensor for PLC activity. The real-time fluorescence intensity from the CPE can be converted to substrate concentration by using an ex situ calibration curve, allowing PLC-catalyzed reaction rates and kinetic parameters to be determined. PLC activation by Ca2+ and inhibition by EDTA and fluoride ion are demonstrated using the optimized sensor. PMID:18044959

Liu, Yan; Ogawa, Katsu; Schanze, Kirk S

2008-01-01

372

Fluorescence suppression using wavelength modulated Raman spectroscopy in fiber-probe-based tissue analysis.  

PubMed

In the field of biomedical optics, Raman spectroscopy is a powerful tool for probing the chemical composition of biological samples. In particular, fiber Raman probes play a crucial role for in vivo and ex vivo tissue analysis. However, the high-fluorescence background typically contributed by the auto fluorescence from both a tissue sample and the fiber-probe interferes strongly with the relatively weak Raman signal. Here we demonstrate the implementation of wavelength-modulated Raman spectroscopy (WMRS) to suppress the fluorescence background while analyzing tissues using fiber Raman probes. We have observed a significant signal-to-noise ratio enhancement in the Raman bands of bone tissue, which have a relatively high fluorescence background. Implementation of WMRS in fiber-probe-based bone tissue study yielded usable Raman spectra in a relatively short acquisition time (?30??s), notably without any special sample preparation stage. Finally, we have validated its capability to suppress fluorescence on other tissue samples such as adipose tissue derived from four different species. PMID:22894519

Praveen, Bavishna B; Ashok, Praveen C; Mazilu, Michael; Riches, Andrew; Herrington, Simon; Dholakia, Kishan

2012-07-01

373

A novel fiber optic biosensor for nitric oxide determination based on vicinal diaminobenzozcridine fluorescent probe  

NASA Astrophysics Data System (ADS)

A novel fiber optic biosensor for the determination of nitric oxide based on vicinal diaminobenzozcridine (VDABA) fluorescent probe was designed and fabricated. The reaction conditions between VDABA and NO, which include concentration of VDABA, temperature and pH, were studied in-depth. The sensitivity of VDABA for NO detection under the optimum conditions and its optical properties were also investigated. The fluorescence responses were concentration-dependent and a good linear relationship (R2=0.9863) was observed over the range 1.8×10-6 to 9×10-6 mol/L NO, the regression equation was F = 3.8889[NO] (mol/L)+217.2. Besides, a complex sensitive film embedding VDABA in cellulose acetate (CA) was prepared, and a fiber optic NO biosensor was fabricated using this film. Then the change of fluorescence phase shift of this biosensor was studied preliminarily by means of the lock-in technology.

Ding, Liyun; Huang, Lanfen; Huang, Jun; Zhong, Yunming; Fan, Dian

2010-04-01

374

A Fluorescent Thermometer Based on a Pyrene-Labeled Thermoresponsive Polymer  

PubMed Central

Thermoresponsive polymers that undergo a solubility transition by variation of the temperature are important materials for the development of ‘smart’ materials. In this contribution we exploit the solubility phase transition of poly(methoxy diethylene glycol methacrylate), which is accompanied by a transition from hydrophilic to hydrophobic, for the development of a fluorescent thermometer. To translate the polymer phase transition into a fluorescent response, the polymer was functionalized with pyrene resulting in a change of the emission based on the microenvironment. This approach led to a soluble polymeric fluorescent thermometer with a temperature range from 11 °C to 21 °C. The polymer phase transition that occurs during sensing is studied in detail by dynamic light scattering.

Pietsch, Christian; Vollrath, Antje; Hoogenboom, Richard; Schubert, Ulrich S.

2010-01-01

375

[The method of phytoplankton photosynthesis activity in-situ measurement based on light induced fluorescence].  

PubMed

According to the phytoplankton fluorescence induction characteristics under different light conditions, chlorophyll fluorescence as a probe for analysis of phytoplankton photosynthesis was studied. The present paper proposed a in-situ measurement method based on the chlorophyll fluorescence values Ft and Fm to get phytoplankton photosynthesis activity, Chlorella vulgaris, microcystis aeruginosa and Cyclotella meneghiniana Kiits were selected as experimental subjects, a comparison test was done between self-developed in-situ measurement system and Water PAM in lab, and the results showed that coefficients between the two methods were 0.9778, 0.8786 and 0.7953. This work provides a rapid and in-situ measurement method for phytoplankton photosynthesis activity. PMID:24369649

Liu, Jing; Liu, Wen-qing; Zhao, Nan-jing; Zhang, Yu-jun; Ma, Ming-jun; Yin, Gao-fang; Dai, Pang-da; Wang, Zhi-gang; Wang, Chun-long; Duan, Jing-bo; Yu, Xiao-ya; Fang, Li

2013-09-01

376

Assessment of fluorescein-based fluorescent dyes for tracing Neotyphodium endophytes in planta.  

PubMed

Fluorescent dyes were assessed for their ability to stain viable hyphae of the fungi Neotyphodium lolii and N. coenophialum, symbiotic endophytes of the Pooideae grasses Lolium perenne and Festuca arundinacea, respectively. The fluorescein-based fluorophores; fluorescein diacetate (FDA), 5(6)-carboxy-fluorescein diacetate (CFDA), 5-chloromethylfluorescein diacetate (CMFDA) and the chitin-binding stain, Calcofluor while M2R, were assessed for staining of endophyte hyphae in vitro from axenic fungal cultures and in planta, including epidermal leaf sheath peels, nodes, ovaries, embryos and meristems. CMFDA produced the greatest intensity of staining of fungal hyphae and gave excellent contrast in planta compared to the plant cells. Compared to the other dyes, CMFDA was also the least affected by photo bleaching and continued to fluoresce up to 2 h after initial excitation. None of the fluorescent dyes stained fungal hyphae in seed. PMID:22802389

Card, Stuart D; Tapper, Brian A; Lloyd-West, Catherine; Wright, Kathryn M

2013-01-01

377

DNA-length-dependent fluorescent sensing based on energy transfer in self-assembled multilayers.  

PubMed

In this paper, a novel DNA-length-dependent fluorescent sensor was constructed based on the fluorescence resonance energy transfer. In the self-assembled multilayers (Quartz/GO/PDDA/Tx-DNA/PDDA/ZnO@CdS), ZnO@CdS and graphene oxide(GO) were employed as an energy donor and an energy acceptor, respectively. Single-stranded Tx-DNA (x represents different chain length of DNA) and poly(diallydimethylammonium) chloride (PDDA) were used as a linker. In the presence of complementary Px-DNA, the formation of double-stranded DNA leads to a change in chain length and achieves the purpose of changing the distance between ZnO@CdS and GO. Thereby, it enhances the efficiency of energy transfer between ZnO@CdS and GO resulting in the quench of fluorescence of ZnO@CdS, and thus different length DNA sequence was detected. PMID:24934748

Sun, Xiang-Ying; Liu, Bin; Sun, Yan-Feng; Yu, Yaming

2014-11-15

378

Fluorescence-based intracavity laser spectroscopy and the electronic structure of NiH  

SciTech Connect

We describe a fluorescence-based continuous-wave (cw) laser intracavity spectrometer which provides tunable cw laser light of high intensity (greater than 200 W/cm{sup 2}) over a large spatial region (greater than 3{times}10{sup {minus}2}cm{sup 3}), greatly increasing the amount of observable side fluorescence and facilitating saturation of weak optical transitions as compared to extracavity spectroscopy. Using examples (saturation dip spectra of the hyperfine structure of the rare isotopomer {sup 61}NiH and dispersed fluorescence spectra terminating in previously unobserved low-lying states of {sup 58}NiH), we illustrate the capability of this spectrometer to rapidly and efficiently gather information crucial to the verification of electronic structure models.

Hill, E.J.; Field, R.W. (George R. Harrison Spectroscopy Laboratory, Massachusetts Institute of Technology, Cambridge, MA (USA) Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA (USA))

1990-07-01

379

Determination of multiple analytes using a fiber optic biosensor based on fluorescence energy transfer  

NASA Astrophysics Data System (ADS)

Recently, we have developed a biosensor for zinc based on the very tight binding of this metal by the enzyme carbonic anhydrase, which requires Zn(II) for catalysis. We were able to transduce the binding of the metal as a change in fluorescence intensity or lifetime by use of a colored inhibitor whose metal-dependent binding permits fluorescence resonance energy transfer (Forster transfer) to occur. We have extended this concept to include other metals and other analytes which may be bound in the native (or mutant) enzyme active site with a concomitant color change; the color change is transduced as a change in energy transfer efficiency. We have also recently demonstrated a similar approach, wherein the presence of a metal ion in the binding site is transduced as a change in fluorescence anisotropy. Results in cuvettes and with fiber optic sensors are shown.

Thompson, Richard B.; Ge, Zhengfang; Patchan, Marcia W.; Fierke, Carol A.; McCall, Keith A.; Elbaum, Daniel; Christianson, David W.

1996-04-01

380

Dendrimer-Based Fluorescent Indicators: In Vitro and In Vivo Applications  

PubMed Central

Background The development of fluorescent proteins and synthetic molecules whose fluorescence properties are controlled by the environment makes it possible to monitor physiological and pathological events in living systems with minimal perturbation. A large number of small organic dyes are available and routinely used to measure biologically relevant parameters. Unfortunately their application is hindered by a number of limitations stemming from the use of these small molecules in the biological environment. Principal Findings We present a novel dendrimer-based architecture leading to multifunctional sensing elements that can overcome many of these problems. Applications in vitro, in living cells and in vivo are reported. In particular, we image for the first time extracellular pH in the brain in a mouse epilepsy model. Conclusion We believe that the proposed architecture can represent a useful and novel tool in fluorescence imaging that can be widely applied in conjunction with a broad range of sensing dyes and experimental setups.

Albertazzi, Lorenzo; Brondi, Marco; Pavan, Giovanni M.; Sato, Sebastian Sulis; Signore, Giovanni; Storti, Barbara; Ratto, Gian Michele; Beltram, Fabio

2011-01-01

381

Glass-based fluorescence reference materials used for optical and biophotonic applications  

NASA Astrophysics Data System (ADS)

Fluorescence techniques are known for their high sensitivity and are widely used as analytical tools and detection methods for product and process control, material sciences, environmental and biotechnical analysis, molecular genetics, cell biology, medical diagnostics, and drug screening. For routine measurements by fluorescence techniques the existence of an improved quality assurance is one of the basic needs. According to DIN/ISO 17025 certified standards are used for fluorescence diagnostics having the drawback of giving relative values only. Typical requirements onto fluorescence reference materials or standards deal with the verification of the instrument performance as well as the improvement of the data comparability. Especially for biomedical applications fluorescence labels are used for the detection of proteins. In particular these labels consist of nano crystalline materials like CdS and CdSe. The field of Non-Cadmium containing materials is under investigation. In order to evaluate whether glass based materials can be used as standards it is necessary to calculate absolute values like absorption/excitation cross sections or relative quantum yields. This can be done using different quantities of dopands in glass, glass ceramics or crystals. The investigated materials are based on different types of glass, silicate, phosphate and boron glass, which play a dominant role for the absorption and emission mechanism. Additional to the so-called elementary fluorescence properties induced by raw earth elements the formation of defects lead to higher cross sections additionally. The main investigations deal with wavelength accuracy and lifetime of doped glasses, glass ceramics and crystalline samples. Moreover intensity patterns, homogeneity aspects and photo stability will be discussed.

Engel, A.; Ottermann, C.; Resch-Genger, U.; Hoffmann, K.; Schweizer, S.; Selling, J.; Spaeth, J.-M.; Rupertus, V.

2006-05-01

382

Rapid High-Throughput Assessment of Aerobic Bacteria in Complex Samples by Fluorescence-Based Oxygen Respirometry  

PubMed Central

A simple method has been developed for the analysis of aerobic bacteria in complex samples such as broth and food homogenates. It employs commercial phosphorescent oxygen-sensitive probes to monitor oxygen consumption of samples containing bacteria using standard microtiter plates and fluorescence plate readers. As bacteria grow in aqueous medium, at certain points they begin to deplete dissolved oxygen, which is seen as an increase in probe fluorescence above baseline signal. The time required to reach threshold signal is used to either enumerate bacteria based on a predetermined calibration or to assess the effects of various effectors on the growth of test bacteria by comparison with an untreated control. This method allows for the sensitive (down to a single cell), rapid (0.5 to 12 h) enumeration of aerobic bacteria without the need to conduct lengthy (48 to 72 h) and tedious colony counts on agar plates. It also allows for screening a wide range of chemical and environmental samples for their toxicity. These assays have been validated with different bacteria, including Escherichia coli, Micrococcus luteus, and Pseudomonas fluorescens, with the enumeration of total viable counts in broth and industrial food samples (packaged ham, chicken, and mince meat), and comparison with established agar plating and optical-density-at-600-nm assays has been given.

O'Mahony, Fiach C.; Papkovsky, Dmitri B.

2006-01-01

383

XI: A Simple Prolog-based Language for Cross-Classification and Inheritance  

Microsoft Academic Search

This paper describes a simple Prolog-based knowledge representation language called XI - X for cross-classification and I for inheritance - which is designed to repre- sent knowledge about individuals, about classes of individuals, and about inclusion relations between classes of individuals. XI allows for straightforward definitions of cross-classification hierarchies and for the association of arbitrary attribute-value information with classes or

R. Gaizauskas; K. Humphreys

1996-01-01

384

Simple sequence repeat-based consensus linkage map of Bombyx mori  

Microsoft Academic Search

We established a genetic linkage map employing 518 simple sequence repeat (SSR, or microsatellite) markers for Bombyx mori (silkworm), the economically and culturally important lepidopteran insect, as part of an international genomics program. A survey of six representative silkworm strains using 2,500 (CA)n- and (CT)n-based SSR markers revealed 17-24% polymorphism, indicating a high degree of homozygosity resulting from a long

Xue-Xia Miao; Shi-Jie Xub; Ming-Hui Li; Mu-Wang Li; Jian-Hua Huang; Fang-Yin Dai; Susan W. Marino; David R. Mills; Peiyu Zeng; Kazuei Mita; Shi-Hai Jia; Yong Zhang; Wen-Bin Liu; Hui Xiang; Qiu-Hong Guo; An-Ying Xu; Xiang-Yin Kong; Hong-Xuan Lin; Yao-Zhou Shi; Gang Lu; Xianglin Zhang; Wei Huang; Yuji Yasukochi; Toshiyuki Sugasaki; Toru Shimada; Javaregowda Nagaraju; Zhong-Huai Xiang; Sheng-Yue Wang; Marian R. Goldsmith; Cheng Lu; Guo-Ping Zhao; Yong-Ping Huang

2005-01-01

385

Propeller design - a simple system based on model propeller test data III  

NASA Technical Reports Server (NTRS)

This report, the third of a series of four, describes a simple system for designing propellers of a standard form. In this report, the system is based on tests of a family of model propellers of standard Navy form, the data from which have been extended by means of calculations to cover the complete range likely to be found in practice. However, it can be worked out for any family having propellers of one general form.

Wieck, Fred E

1926-01-01

386

Multiscale simulations in simple metals: A density-functional-based methodology  

Microsoft Academic Search

We present a formalism for coupling a density-functional-theory-based quantum simulation to a classical simulation for the treatment of simple metallic systems. The formalism is applicable to multiscale simulations in which the part of the system requiring quantum-mechanical treatment is spatially confined to a small region. Such situations often arise in physical systems where chemical interactions in a small region can

Nicholas Choly; Gang Lu; Weinan E; Efthimios Kaxiras

2005-01-01

387

A Simple Antibody-Based Test for Dough Strength. II. Genotype and Environmental Effects  

Microsoft Academic Search

Cereal Chem. 68(5):475-481 The ability of simple antibody-based tests to assess and predict specific and antibody binding were obtained with sets of varieties grown at different aspects of dough quality was evaluated using flours from several sets levels of nitrogen fertilization at the same site or in a range of environments. of wheat lines and varieties. Highest correlations between the

JOHN H. SKERRITT

388

Simple, phage-based (FASTPlaque) technology to determine rifampicin resistance of Mycobacterium tuberculosis directly from sputum  

Microsoft Academic Search

OBJECTIVE: To evaluate the performance of a simple, manual, phage-based test for determining rifampicin (RMP) resistance of Mycobacterium tuberculosis di- rectly from smear-positive sputum specimens. DESIGN: A comparative study of the performance of the FASTPlaque (phage amplification) technology to deter- mine RMP resistance directly from smear-positive spu- tum compared with isolation and the conventional in- direct Middlebrook 7H11 agar proportion

H. Albert; A. Trollip; T. Seaman; R. J. Mole

389

Webcam camera as a detector for a simple lab-on-chip time based approach  

Microsoft Academic Search

A modification of a webcam camera for use as a small and low cost detector was demonstrated with a simple lab-on-chip reactor. Real time continuous monitoring of the reaction zone could be done. Acid–base neutralization with phenolphthalein indicator was used as a model reaction. The fading of pink color of the indicator when the acidic solution diffused into the basic

Wasin Wongwilai; Somchai Lapanantnoppakhun; Supara Grudpan; Kate Grudpan

2010-01-01

390

Simple, fast and accurate eight points amplitude estimation method of sinusoidal signals for DSP based instrumentation  

NASA Astrophysics Data System (ADS)

A simple, fast and accurate amplitude estimation algorithm of sinusoidal signals for DSP based instrumentation is proposed. It is shown that eight samples, used in two steps, are sufficient. A practical analytical formula for amplitude estimation is obtained. Numerical results are presented. Simulations have been performed when the sampled signal is affected by white Gaussian noise and when the samples are quantized on a given number of bits.

Vizireanu, D. N.; Halunga, S. V.

2012-04-01

391

Simple-Design Low-Noise NLTL-Based Frequency Synthesizers for a CPT Cs Clock  

Microsoft Academic Search

This paper presents simple-architecture low-noise frequency synthesis chains generating a 9-GHz signal. These devices are based on the use of a nonlinear transmission line (NLTL) used as a comb generator. The residual phase noise spectra of the key components are reported. The residual phase noise performance of the chains at 9 GHz is measured to be less than -80 dBrad2\\/Hz

Rodolphe Boudot; Stéphane Guérandel; Emeric de Clercq

2009-01-01

392

A "turn-on" and label-free fluorescent assay for the rapid detection of exonuclease III activity based on Tb(3+)-induced G-quadruplex conjugates.  

PubMed

A "turn-on" and label-free fluorescent assay for the specific, rapid, and sensitive detection of 3'???5' exonuclease III activity is reported in this study. The assay is based on the Tb(3+)-promoted G-quadruplex, which lead to the enhancement of Tb(3+) fluorescence due to the energy transfer from guanines. The proposed assay is highly simple, rapid, and cost-effective, and does not require sophisticated experimental techniques such as gel-based equipment or radioactive labels. It can be used for the rapid detection of exonuclease III activity with a detection limit of 0.8 U and a RSD (n?=?6) <5 %. Notably, no dye was covalently conjugated to the DNA strands, which offers the advantages of low-cost and being interference-free. PMID:24770805

Yang, WeiJuan; Ruan, YaJuan; Wu, WeiHua; Chen, PingPing; Xu, LiangJun; Fu, FengFu

2014-07-01

393

A simple PCR-based strategy for estimating species-specific contributions in chimeras and xenografts.  

PubMed

Many tissue-engineering approaches for repair and regeneration involve transplants between species. Yet a challenge is distinguishing donor versus host effects on gene expression. This study provides a simple molecular strategy to quantify species-specific contributions in chimeras and xenografts. Species-specific primers for reverse transcription quantitative real-time PCR (RT-qPCR) were designed by identifying silent mutations in quail, duck, chicken, mouse and human ribosomal protein L19 (RPL19). cDNA from different pairs of species was mixed in a dilution series and species-specific RPL19 primers were used to generate standard curves. Then quail cells were transplanted into transgenic-GFP chick and resulting chimeras were analyzed with species-specific primers. Fluorescence-activated cell sorting (FACS) confirmed that donor- and host-specific levels of RPL19 expression represent actual proportions of cells. To apply the RPL19 strategy, we measured Runx2 expression in quail-duck chimeras. Elevated Runx2 levels correlated with higher percentages of donor cells. Finally, RPL19 primers also discriminated mouse from human and chick. Thus, this strategy enables chimeras and/or xenografts to be screened rapidly at the molecular level. PMID:23785056

Ealba, Erin L; Schneider, Richard A

2013-07-01

394

A simple PCR-based strategy for estimating species-specific contributions in chimeras and xenografts  

PubMed Central

Many tissue-engineering approaches for repair and regeneration involve transplants between species. Yet a challenge is distinguishing donor versus host effects on gene expression. This study provides a simple molecular strategy to quantify species-specific contributions in chimeras and xenografts. Species-specific primers for reverse transcription quantitative real-time PCR (RT-qPCR) were designed by identifying silent mutations in quail, duck, chicken, mouse and human ribosomal protein L19 (RPL19). cDNA from different pairs of species was mixed in a dilution series and species-specific RPL19 primers were used to generate standard curves. Then quail cells were transplanted into transgenic-GFP chick and resulting chimeras were analyzed with species-specific primers. Fluorescence-activated cell sorting (FACS) confirmed that donor- and host-specific levels of RPL19 expression represent actual proportions of cells. To apply the RPL19 strategy, we measured Runx2 expression in quail-duck chimeras. Elevated Runx2 levels correlated with higher percentages of donor cells. Finally, RPL19 primers also discriminated mouse from human and chick. Thus, this strategy enables chimeras and/or xenografts to be screened rapidly at the molecular level.

Ealba, Erin L.; Schneider, Richard A.

2013-01-01

395

Dual excitation fluorescence-based sensors for pH and dissolved carbon dioxide monitoring  

Microsoft Academic Search

We report on high performance ratiometric fluorescence-based pH and dissolved carbon dioxide (dCO2) sensors for use in bioprocess and environmental monitoring applications, respectively. Novel hybrid sol-gel-based sensor materials have been developed and successfully used as host matrices in pH and dCO2 sensing. These sensors are easy to prepare and miniaturise, low-cost in terms of fabrication, are mass-producible and when the

Dorota Wencel; John P. Moore; Niall Stevenson; Colette McDonagh

2011-01-01

396

X-ray fluorescence microtomography- and polycapillary-based confocal imaging using synchrotron radiation  

Microsoft Academic Search

This work illustrates the development of X-ray fluorescence tomography and polycapillary based confocal imaging towards a three-dimensional (3D), quantitative analytical method with lateral resolution levels down to the 2-20 mum scale. Detailed analytical characterization is given for polycapillary based confocal XRF imaging, which is a new variant of the 3D micro-XRF technique. Applications for 2D\\/3D micro-XRF are illustrated for the

Laszlo Vincze; Bart Vekemans; Imre Szaloki; Frank E. Brenker; Gerald Falkenberg; Karen Rickers; Katrien Aerts; Rene Van Grieken; Freddy Adams

2004-01-01

397

Fluorescent Aptamer Sensors  

NASA Astrophysics Data System (ADS)

Aptamers are single-stranded nucleic acid probes that can be evolved to have high specificity and affinity for different targets. These targets include biomar-ker proteins, small molecules, and even whole live cells that express a variety of surface proteins of interest. Aptamers offer several advantages over protein-based molecular probes such as low immunogenic activity, flexible modification, and in vitro synthesis. In addition, aptamers used as molecular probes can be made with easy signaling for binding with their corresponding targets. There are a few different fluorescence-based signal transduction mechanisms, such as direct fluorophore labeling, fluorescence resonance energy transfer (FRET), fluorescence quenching, fluorescence anisotropy, and light-switching excimers. These signaling processes in combination with various labeling strategies of nucleic acid aptamers contribute to simple, rapid, sensitive, and selective biological assays. In this chapter, we discuss the optical signaling of aptamers for single proteins such as ?-thrombin and platelet-derived growth factor (PDGF). We also present detailed discussion about fluorescent aptamers developed from cell-based systematic evolution of ligands by exponential enrichment (SELEX) for the recognition of different target tumor cells.

Chen, Hui William; Kim, Youngmi; Meng, Ling; Mallikaratchy, Prabodhika; Martin, Jennifer; Tang, Zhiwen; Shangguan, Dihua; O'Donoghue, Meghan; Tan, Weihong

398

Fluorescent probe for copper(II) ion based on a rhodamine spirolactame derivative, and its application to fluorescent imaging in living cells  

Microsoft Academic Search

A fluorescent probe for Cu(II) ion is presented. It is based on the rhodamine fluorophore and exhibits high selectivity and\\u000a sensitivity for Cu(II) ion in aqueous methanol (2:8, v\\/v) at pH 7.0. The response is based on a ring opening reaction and formation of a strongly fluorescent 1:1 complex. The response\\u000a is reversible and linear in the range between 50 nM

Chunwei Yu; Jun Zhang; Jinhua Li; Ping Liu; Peihai Wei; Lingxin Chen

399

Fluorescence-based determination of the copper concentration in drinking water  

NASA Astrophysics Data System (ADS)

Copper is a heavy metal, which is used in heat and electrical conductors and in a multitude of alloys in the technical context. Moreover, it is a trace element that is essential for the life of organisms but can cause toxic effects in elevated concentrations. Maximum limits in water and beverages exist. Here, the decrease of the fluorescence lifetime of green fluorescent protein (GFP) by Förster resonance energy transfer is used to measure the copper ion concentration in drinking water. Therefore, a system is developed that is based on a GFP sample in a predefined concentration. The GFP mutant can be excited with blue light. For binding of copper ions, a His-tag is included in the GFP. After measuring the fluorescence lifetime of pure GFP, the copper determination of the sample is performed by lifetime measurement. Therefore, the lifetime can be assigned to the copper concentration of the GFP-doped drinking water sample. In summary, a method for the quantification of copper ions based on changes of the fluorescence lifetime of GFP is developed, and the measurement of the copper concentration in water samples is performed.

Hötzer, Benjamin; Scheu, Timo; Jung, Gregor; Castritius, Stefan

2013-05-01

400

Fluorescence-based directed termination PCR: direct mutation characterization without sequencing.  

PubMed

We describe a fluorescence-based directed termination PCR (fluorescent DT-PCR) that allows accurate determination of actual sequence changes without dideoxy DNA sequencing. This is achieved using near infrared dye-labeled primers and performing two PCR reactions under low and unbalanced dNTP concentrations. Visualization of resulting termination fragments is accomplished with a dual dye Li-cor DNA sequencer. As each DT-PCR reaction generates two sets of terminating fragments, a pair of complementary reactions with limiting dATP and dCTP collectively provide information on the entire sequence of a target DNA, allowing an accurate determination of any base change. Blind analysis of 78 mutants of the supF reporter gene using fluorescent DT-PCR not only correctly determined the nature and position of all types of substitution mutations in the supF gene, but also allowed rapid scanning of the signature sequences among identical mutations. The method provides simplicity in the generation of terminating fragments and 100% accuracy in mutation characterization. Fluorescent DT-PCR was successfully used to generate a UV-induced spectrum of mutations in the supF gene following replication on a single plate of human DNA repair-deficient cells. We anticipate that the automated DT-PCR method will serve as a cost-effective alternative to dideoxy sequencing in studies involving large-scale analysis for nucleotide sequence changes. PMID:11160937

Chen, J Z; Smith, L; Pfeifer, G P; Holmquist, G P

2001-02-15

401

A new chiral binaphthalene-based fluorescence polymer sensor for the highly enantioselective recognition of phenylalaninol.  

PubMed

A new (S)-binaphthalene-based polymer (P-1) was synthesized by the polymerization of 5,5'-((2,5-dibutoxy-1,4-phenylene)bis(ethyne-2,1-diyl))bis(2-hydroxy-3-(piperidin-1-ylmethyl) benzaldehyde (M-1) with (S)-2,2'-dimethoxy-(1,1'-binaphthalene)-3,3'-diamine (M-2) through the formation of a Schiff base; the corresponding chiral polymer (P-2) could be obtained by the reduction of polymer P-1 with NaBH4 . Chiral polymer P-1 exhibited a remarkable "turn-on" fluorescence-enhancement response towards (D)-phenylalaninol and excellent enantioselective recognition behavior with enantiomeric fluorescence difference ratios (ef) as high as 8.99. More importantly, chiral polymer P-1 displays a bright blue fluorescence color change upon the addition of (D)-phenylalaninol under a commercially available UV lamp, which can be clearly observed by the naked eye. On the contrary, chiral polymer P-2 showed weaker enantioselective fluorescence ability towards the enantiomers of phenylalaninol. PMID:24123510

Wei, Guo; Zhang, Shuwei; Dai, Chunhui; Quan, Yiwu; Cheng, Yixiang; Zhu, Chengjian

2013-11-18

402

Compact flashlamp-based fluorescence imager for use under ambient-light conditions  

NASA Astrophysics Data System (ADS)

A low-power, lightweight, multiwavelength fluorescence imager based on the use of a compact xenon flashlamp, bandpass filters, gated charge-coupled device camera, and digital image processing was developed for use on an autonomous rover vehicle. The imager discriminates against ambient light by use of microsecond excitation pulses along with synchronized camera operation to limit the time period in which ambient-light photocounts are accumulated, and digital image subtraction to remove background counts. In a 10 cm square field of view, weak fluorescence, equivalent to 0.05 pmol fluorescein/mm2, can be quantified against a white-light background equivalent to shaded sunlight. For application in autonomous search for organisms in extreme environments such as in situ desert rock or soil, the instrument was equipped with a set of fluorescence excitation filters (380, 450, 545, and 600 nm) and emission filters (460, 510, 620, and 740 nm) suitable for detection of chlorophyll, applied stains for protein, DNA, lipid and carbohydrate, and autofluorescence. True-color images were obtained through red-green-blue imaging filters (630, 535, and 470 nm) used with white-light flashes. Automated focusing on ground features was based on the R-band image and was carried out prior to fluorescence image acquisition.

Lanni, Frederick; Pane, David A.; Weinstein, Shmuel J.; Waggoner, Alan S.

2007-03-01

403

A new fluorescent chemosensor for Al3+ ion based on schiff base naphthalene derivatives  

NASA Astrophysics Data System (ADS)

A new naphthalene derivative receptor (H2L) was synthesized. The chemosensor (H2L) exhibited a strong fluorescence enhancement in the presence of trace amounts of Al3+, attributable to chelation-enhanced fluorescence (CHEF) effect, which also displayed high selectivity over a series of other metal cations (Na+, K+, Cs+, Mg2+, Ba2+, Pb2+, Cr3+, Mn2+, Fe3+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+ and Ag+) in ethanol.

Azadbakht, Reza; Rashidi, Somaye

2014-06-01

404

A Multifunctional Fluorescence Probe for the Detection of Cations in Aqueous Solution: the Versatility of Probes Based on Peptides  

Microsoft Academic Search

We synthesized a tetra-functional fluorescence probe based on dansyl and peptide motif, dansyl-Gly-Trp (DGT, 1), that efficiently bound several metal ions and showed distinguishing optical properties. The probe 1 could respond to Hg2+ with enhanced and blue-shifted fluorescence emission but to Cu2+ with obvious fluorescence quenching. In addition, 1 was sensitive to pH ranging from 2.0 to 5.0 and precipitated

Bin Wang; Hong-Wei Li; Yang Gao; Houyu Zhang; Yuqing Wu

405

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

Microsoft Academic Search

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

Ying Zhang; Hua Wang; Rong H. Yang

2007-01-01

406

Site-specific fluorescent probing of RNA molecules by unnatural base-pair transcription for local structural conformation analysis  

Microsoft Academic Search

Methods for fluorescent probing at a defined position of RNA provide powerful tools for analyzing the local structural conformation of functional RNA molecules by tracking fluorescence changes. In this article, we describe the site-specific fluorescent probing of RNA by transcription with an expanded genetic alphabet, using an extra, unnatural base pair between 2-amino-6-(2-thienyl)purine (s) and pyrrole-2-carbaldehyde (Pa). The protocol comprises

Yasushi Hikida; Michiko Kimoto; Shigeyuki Yokoyama; Ichiro Hirao

2010-01-01

407

Naphthalimide-based fluorescent Zn 2+ chemosensors showing PET effect according to their linker length in water  

Microsoft Academic Search

We have developed naphthalimide-based fluorescent chemosensors that exhibit fluorescence enhancement upon binding Zn2+ ion in 10mM HEPES buffer (pH 7.4) at 25°C. The fluorescence enhancement was induced by a PET inhibition process in which electron transfer from the nitrogen lone pair electrons of the Dpa unit to naphthalimide was blocked upon the binding of the sensor to Zn2+. The longer

Soon Young Kim; Jong-In Hong

2009-01-01

408

Development of a Fluorescence-Based Imaging System for Colon Cancer Diagnosis Using Two Novel Rhodamine Derivatives  

Microsoft Academic Search

. Tissue characterisation by endoscopic fluorescence imaging of exogenous fluorophores appears to be a promising method for\\u000a cancer detection. Cationic and lipophilic fluorescence compounds of the aminoxanthene chemical family, have been found to\\u000a exhibit selective accumulation in various carcinoma cells.\\u000a \\u000a In this paper the development of an endoscopic fluorescence-based imaging system with the additional capability of collecting\\u000a emission spectra is

D. Yova; V. Atlamazoglou; N. Kavantzas; S. Loukas

2000-01-01

409

Fifth Graders' Learning About Simple Machines Through Engineering Design-Based Instruction Using LEGO™ Materials  

NASA Astrophysics Data System (ADS)

This study is part of a 5-year National Science Foundation-funded project, Transforming Elementary Science Learning Through LEGO™ Engineering Design. In this study, we report on the successes and challenges of implementing an engineering design-based and LEGO™-oriented unit in an urban classroom setting and we focus on the impact of the unit on students' content understanding of simple machines. The LEGO™ engineering-based simple machines module, which was developed for fifth graders by our research team, was implemented in an urban school in a large city in the Northeastern region of the USA. Thirty-three fifth grade students participated in the study, and they showed significant growth in content understanding. We measured students' content knowledge by using identical paper tests and semistructured interviews before and after instruction. Our paired t test analysis results showed that students significantly improved their test and interview scores (t = -3.62, p < 0.001 for multiple-choice items and t = -9.06, p < 0.000 for the open-ended items in the test and t = -12.11, p < 0.000 for the items in interviews). We also identified several alternative conceptions that are held by students on simple machines.

Marulcu, Ismail; Barnett, Mike

2012-12-01

410

Simple ORAM.  

National Technical Information Service (NTIS)

In this short note, we demonstrate a simple and practical ORAM that enjoys an extremely simple proof of security. Our construction is based on a recent ORAM due to Shi, Chan, Stefanov and Li SCSL11, but with some crucial modifications, which significantly...

K. Chung R. Pass

2013-01-01

411

Determination of protease subsite preference on SPOT peptide array by fluorescence quenching-based assay.  

PubMed

A peptide SPOT array was synthesized on a glass chip and used to determine protease subsite preference. To synthesize a peptide array for positional scanning, the ratio of the isokinetic concentration was determined for every Fmoc-amino acid except Cys. Based on this ratio, a peptide array consisting of Dabcyl-X-X-P(2)-Arg-X-X-X-Lys(FITC) (X: equimolar mixture of 19 amino acids, P(2): one of 19 amino acids) was synthesized on a chitosan-grafted glass chip. Subsequently, the peptide substrates on the array were hydrolyzed by thrombin to screen for subsite specificity using a fluorescence quenching-based assay. The P(2) subsite specificity of thrombin was screened by the fluorescence images obtained after hydrolysis. Pro at the P(2) subsite showed the highest specificity for thrombin based on both the fluorescence quenching-based assay and the solution phase assay. From these results, we confirmed that our mixture-based peptide SPOT array format on the chitosan-grafted glass chips could be used to determine protease subsite preference. PMID:22544649

Kim, Do-Hyun; Shin, Dong-Sik; Lee, Yoon-Sik

2012-06-01

412

Hydrogen sulfide deactivates common nitrobenzofurazan-based fluorescent thiol labeling reagents.  

PubMed

Sulfhydryl-containing compounds, including thiols and hydrogen sulfide (H2S), play important but differential roles in biological structure and function. One major challenge in separating the biological roles of thiols and H2S is developing tools to effectively separate the reactivity of these sulfhydryl-containing compounds. To address this challenge, we report the differential responses of common electrophilic fluorescent thiol labeling reagents, including nitrobenzofurazan-based scaffolds, maleimides, alkylating agents, and electrophilic aldehydes, toward cysteine and H2S. Although H2S reacted with all of the investigated scaffolds, the photophysical response to each scaffold was significantly different. Maleimide-based, alkylating, and aldehydic thiol labeling reagents provided a diminished fluorescence response when treated with H2S. By contrast, nitrobenzofurazan-based labeling reagents were deactivated by H2S addition. Furthermore, the addition of H2S to thiol-activated nitrobenzofurazan-based reagents reduced the fluorescence signal, thus establishing the incompatibility of nitrobenzofurazan-based thiol labeling reagents in the presence of H2S. Taken together, these studies highlight the differential reactivity of thiols and H2S toward common thiol-labeling reagents and suggest that sufficient care must be taken when labeling or measuring thiols in cellular environments that produce H2S due to the potential for both false-positive and eroded responses. PMID:24852143

Montoya, Leticia A; Pluth, Michael D

2014-06-17

413

Patterning pallet arrays for cell selection based on high-resolution measurements of fluorescent biosensors.  

PubMed

Pallet arrays enable cells to be separated while they remain adherent to a surface and provide a much greater range of cell selection criteria relative to that of current technologies. However there remains a need to further broaden cell selection criteria to include dynamic intracellular signaling events. To demonstrate the feasibility of measuring cellular protein behavior on the arrays using high resolution microscopy, the surfaces of individual pallets were modified to minimize the impact of scattered light at the pallet edges. The surfaces of the three-dimensional pallets on an array were patterned with a coating such as fibronectin using a customized stamping tool. Micropatterns of varying shape and size were printed in designated regions on the pallets in single or multiple steps to demonstrate the reliability and precision of patterning molecules on the pallet surface. Use of a fibronectin matrix stamped at the center of each pallet permitted the localization of H1299 and mouse embryonic fibroblast (MEF) cells to the pallet centers and away from the edges. Compared to pallet arrays with fibronectin coating the entire top surface, arrays with a central fibronectin pattern increased the percentage of cells localized to the pallet center by 3-4-fold. Localization of cells to the pallet center also enabled the physical separation of cells from optical artifacts created by the rough pallet side walls. To demonstrate the measurement of dynamic intracellular signaling on the arrays, fluorescence measurements of high spatial resolution were performed using a RhoA GTPase biosensor. This biosensor utilized fluorescence resonance energy transfer (FRET) between cyan fluorescent protein (CFP) and yellow fluorescent protein (YFP) to measure localized RhoA activity in cellular ruffles at the cell periphery. These results demonstrated the ability to perform spatially resolved measurements of fluorescence-based sensors on the pallet arrays. Thus, the patterned pallet arrays should enable novel cell separations in which cell selection is based on complex cellular signaling properties. PMID:21621038

Shadpour, Hamed; Zawistowski, Jon S; Herman, Annadele; Hahn, Klaus; Allbritton, Nancy L

2011-06-24

414

Molecularly imprinted polymers as biomimetic receptors for fluorescence-based optical sensors  

NASA Astrophysics Data System (ADS)

Molecularly imprinted polymers (MIPs), human-made polymers capable of recognizing a particular molecule in the presence of others due to the selective cavities of the material, have been successfully applied to the development of chromatographic and solid phase extraction methods. They have also been applied to the development of electrochemical, piezoelectrical and optical sensors. In parallel with the classification of biosensors, MIP-based devices can work according to two different detection schemes: (1) affinity sensors ("plastic-bodies") and, (2) catalytic sensors ("plastic-enzymes"). In the first case the change in a characteristic optical property, most frequently fluorescence, of the analyte or of the polymer is monitored, upon their mutual interaction. Alternatively, a fluorescent analogue of the target analyte can also be used to develop sensors based on competitive assays (MIAs). Optimization of the polymer composition and, in particular, a proper choice of the nature of the functional monomers involved in the polymerization process, is critical to prepare materials able to selectively interact with the analyte in aqueous media and with the fast kinetics required for analytical applications. Moreover, a rational design of fluorescent analogues of non-naturally fluorescent templates or of fluorescent monomers able to change its property upon interaction with the analyte, is also a bottle neck for wide application of this recognition elements in optical sensing. In this paper we present several approaches to address these issues namely the optimization of MIP composition and the design and synthesis of novel fluorophores for the analysis of antibiotics and mycotoxins in real samples.

Moreno-Bondi, María C.; Urraca, Javier L.; Benito-Peña, Elena; Navarro-Villoslada, Fernando; Martins, Sofía A.; Orellana, Guillermo; Sellergren, Börje

2007-07-01

415

Optimizing two radioluminescence based quality assurance devices for diagnostic radiology utilizing a simple model  

NASA Astrophysics Data System (ADS)

The extrinsic (absolute) efficiency of a phosphor is expressed as the ratio of light energy emitted per unit area at the phosphor surface to incident x-ray energy fluence. A model described in earlier work has shown that by knowing the intrinsic efficiency, the particle size, the thickness and the light extinction factor ?, it is possible to deduce the extrinsic efficiency for an extended range of particle sizes and layer thicknesses for a given design. The model has been tested on Gd2O2S:Tb and ZnS:Cu fluorescent layers utilized in two quality assurance devices, respectively, aimed for the assessment of light field and radiation field congruence in diagnostic radiology. The first unit is an established device based on both fluorescence and phosphorescence containing an x-ray sensitive phosphor (ZnS:Cu) screen comprising a long afterglow. Uncertainty in field edge position is estimated to 0.8 mm (k=2). The second unit is under development and based on a linear CCD sensor which is sensitized to x-rays by applying a Gd2O2S:Tb scintillator. The field profiles and the corresponding edge location are then obtained and compared. Uncertainty in field edge location is estimated to 0.1 mm (k=2). The properties of the radioluminescent layers are essential for the functionality of the devices and have been optimized utilizing the previously developed and verified model. A theoretical description of the maximization of phosphorescence is also briefly discussed as well as an interesting finding encountered during the development processes: focal spot wandering. The oversimplistic physical assumptions made in the radioluminescence model have not been found to lead the optimizing process astray. The obtained functionality is believed to be adequate within their respective limitations for both devices.

Lindström, Jan; Hulthén, Markus; Alm Carlsson, Gudrun; Sandborg, Michael

2014-03-01

416

Silver nanoparticle-enhanced fluorescence in microtransponder-based immuno- and DNA hybridization assays  

PubMed Central

The aim of this study is to improve assay sensitivity in common solid-phase bioassay configurations as the result of using silver nanoparticles. The solid phase was provided by numerically indexed, silicon-based electronic chips, microtransponders (p-Chips) that have previously been used in multiplexed assays. Assay configurations investigated included an ELISA-type immunoassay and a DNA hybridization assay. The surface of p-Chips was derivatized with the silver island film (SIF) and a polymer, and then characterized with AFM and SEM. Silver nanoparticle sizes were in the range of 100 to 200 nm. Four fluorophores were tested for fluorescence enhancement; namely, green fluorescent protein, phycoerythrin, Cy3 and Alexa Fluor 555. We consistently observed significant fluorescence enhancement and sensitivity improvement in the p-Chip-based assays: the sensitivity in the cytokine IL-6 immunoassay was 4.3 pg/ml, which represented a 25-fold increase over the method not involving a SIF; and 50 pM in the hybridization assay, a 38-fold increase. The greatest enhancement was obtained for p-Chip surfaces derivatized first with the polymer and then coated with SIF. In conclusion, we show that the SIF-p-Chip-based platform is a highly sensitive method to quantify low-abundance biomolecules in nucleic acid-based assays and immunoassays.

Li, Ji; Wang, Zhuying; Gryczynski, Ignacy

2010-01-01

417

Dynamic range of fluorescence detection and base-calling accuracy in DNA sequencer based on single-photon counting.  

PubMed

Recently, we developed a family of high-performance automated capillary DNA sequencing instruments based on a single-photon detection of fluorescently labeled DNA fragments. Our machines employ digital and broadband techniques, essential for achieving superior instrument sensitivity and dynamic range. In the present paper, we discuss limitations of the instrument's performance caused by the nonlinearity of single-photon detectors as well as methods for nonlinearity compensation which increase the detection dynamic range and base-calling accuracy. PMID:12707910

Gavrilov, Dmitri N; Gorbovitski, Boris; Gouzman, Mikhail; Gudkov, Georgiy; Stepoukhovitch, Andrei; Ruskovoloshin, Victor; Tsuprik, Andrei; Tyshko, Georgiy; Bilenko, Olga; Kosobokova, Olga; Luryi, Serge; Gorfinkel, Vera

2003-04-01

418

Fluorescence-based temperature measurement in laser-induced vapor bubbles  

NASA Astrophysics Data System (ADS)

A fluorescence-based temperature probe (optrode) was designed to measure temperature within laser-induced vapor bubbles. The optrode consisted of a 400-micrometer optical fiber with a rhodamine B-doped polyurethane film attached to the fiber tip. The film exhibited a fluorescence decay time of 4 ns, and the measured fluorescence yield was temperature dependent in the range from 20 to 110 degrees Celsius. A Ho:YAG laser ((lambda) equals 2.12 micrometer, (tau) p equals 250 microseconds) with a pulse energy of 256 plus or minus 7 mJ delivered through a fiber was used to produce the vapor bubbles. The bubbles reached maximum expansion 200 microseconds after the onset of the laser pulse and had an average lifetime of 350 microseconds. The temperature was measured by positioning the optrode within the vapor bubble and exciting its fluorescent film-coated tip with a nitrogen dye laser ((lambda) equals 540 nm, (tau) p equals 500 ps). At maximum expansion, the temperatures in the vapor bubbles were approximately 61 degrees Celsius, indicating sub-atmospheric saturated vapor pressures. The vapor pressure at maximum expansion was confirmed by Rayleigh's equation.

Chan, Kin Foong; Pfefer, T. Joshua; Hammer, Daniel X.; Jansen, E. Duco; Frenz, Martin; Welch, Ashley J.

1998-05-01

419

Chemodosimeter-based fluorescent detection of L-cysteine after extracted by molecularly imprinted polymers.  

PubMed

A chemodosimeter-based fluorescent detection method coupled with molecularly imprinted polymers (MIPs) extraction was developed for determination of L-cysteine (L-Cys) by combining molecular imprinting technique with fluorescent chemodosimeter. The MIPs prepared by precipitation polymerization with L-Cys as template, possessed high specific surface area of 145 m(2)/g and good thermal stability without decomposition lower than 300 °C, and were successfully applied as an adsorbent with excellent selectivity for L-Cys over other amino acids, and enantioselectivity was also demonstrated. A novel chemodosimeter, rhodamine B1, was synthesized for discriminating L-Cys from its structurally similar homocysteine and glutathione as well as various possibly co-existing biospecies in aqueous solutions with notable fluorescence enhancement when adding L-Cys. As L-Cys was added with increasing concentrations, an emission band peaked at 580 nm occurred and significantly increased in fluorescence intensity, by which the L-Cys could be sensed optically. High detectability up to 12.5 nM was obtained. An excellent linearity was found within the wide range of 0.05-50 ?M (r=0.9996), and reasonable relative standard deviations ranging from 0.3% to 3.5% were attained. Such typical features as high selectivity, high sensitivity, easy operation and low cost enabled this MIPs-fluorometry to be potentially applicable for routine detection of trace L-Cys. PMID:24468373

Cai, Xiaoqiang; Li, Jinhua; Zhang, Zhong; Wang, Gang; Song, Xingliang; You, Jinmao; Chen, Lingxin

2014-03-01

420

Highly sensitive detection of proteins based on metal-enhanced fluorescence with novel silver nanostructures.  

PubMed

We present a highly sensitive metal enhanced fluorescence (MEF) method based on a novel silver nanostructure fabricated with Cy5-functionalized silver nanoparticles (AgNPs) and AgNO(3). The analytical performance has been demonstrated by microarray detection of streptavidin (SA) and human IgE. The fluorescence intensity can be enhanced substantially with the combined use of AgNPs and fluorescence enhanced solution (FES). Aptamers have been used for the preparation of Tag-C, which demonstrate IgE detection from 0.5 ng/mL to 16 ng/mL, and the limit of detection is determined to be 0.25 ng/mL. SEM images show nanogaps exist in the aggregated silver nanoparticles and the nanogaps allow for the trap of fluorophores in the nanostructures that emit brighter light upon excitation. The silver nanostructures formed by Tags and FES proved to be an excellent platform for MEF of fluorophores whose excitation and emission occurred between 436 nm and 1000 nm. Finite-difference time-domain (FDTD) simulation has been carried out to confirm the enhanced electromagnetic field inside silver nanostructures, leading to strong overlap/resonance coupling and eventual fluorescence enhancement. PMID:22992196

Li, Hui; Chen, Chih-Yuan; Wei, Xia; Qiang, Weibing; Li, Zhonghui; Cheng, Quan; Xu, Danke

2012-10-16

421

Matrix Effects on the Microcystin-LR Fluorescent Immunoassay Based on Optical Biosensor  

PubMed Central

Matrix effects on the microcystin-LR fluorescent immunoassay based on the evanescent wave all-fiber immunosensor (EWAI) and their elimination methods were studied. The results indicated that PBS and humic acid did not affect the monitoring of samples under the investigated conditions. When the pH was less than 6 or higher than 8, the fluorescence signals detected by immunosensor systems were obviously reduced with the decrease or increase of pH. When the pH ranged from 6 to 8, IC50 and the linear working range of MC-LR calculated from the detection curves were 1.01?1.04 ?g/L and 0.12?10.5 ?g/L, respectively, which was favourable for an MC-LR immunoassay. Low concentrations of Cu2+ rarely affected the detection performance of MC-LR. When the concentration of CuSO4 was higher than 5 mg/L, the fluorescence signal detected by EWAI clearly decreased, and when the concentration of CuSO4 was 10 mg/L, the fluorescence signal detected was reduced by 70%. The influence of Cu2+ on the immunoassay could effectively be compromised when chelating reagent EDTA was added to the pre-reaction mixture.

Long, Feng; Zhu, An-na; Sheng, Jian-Wu; He, Miao; Shi, Han-Chang

2009-01-01

422

A ratiometric fluorescent sensor for zinc ions based on covalently immobilized derivative of benzoxazole  

NASA Astrophysics Data System (ADS)

In the present paper, we describe the fabrication and analytical characteristics of fluorescence-based zinc ion-sensing glass slides. To construct the sensor, a benzoxazole derivative 4-benzoxazol-2'-yl-3-hydroxyphenyl allyl ether (1) with a terminal double bond was synthesized and copolymerized with 2-hydroxyethyl methacrylate (HEMA) on the activated surface of glass slides by UV irradiation. In the absence of Zn 2+ at pH 7.24, the resulting optical sensor emitted fluorescence at 450 nm via excited-state intramolecular proton transfer (ESIPT). Upon binding with Zn 2+, the ESIPT process was inhibited resulting in a 46 nm blue-shift of fluorescence emission. Thus, the proposed sensor can behave as a ratiometric fluorescent sensor for the selective detection of Zn 2+. In addition, the sensor shows nice selectivity, good reproducibility and fast response time. Cd 2+ did not interfere with Zn 2+ sensing. The sensing membrane demonstrates a good stability with a lifetime of at least 3 months. The linear response range covers a concentration range of Zn 2+ from 8.0 × 10 -5 to 4.0 × 10 -3 mol/L and the detection limit is 4.0 × 10 -5 mol/L. The determination of Zn 2+ in both tap and river water samples shows satisfactory results.

Ma, Qiu-Juan; Zhang, Xiao-Bing; Zhao, Xu-Hua; Gong, Yi-Jun; Tang, Jian; Shen, Guo-Li; Yu, Ru-Qin

2009-08-01

423

Light-sheet-based fluorescence microscopy for three-dimensional imaging of biological samples.  

PubMed

In modern biology, most optical imaging technologies are applied to two-dimensional cell culture systems; that is, they are used in a cellular context that is defined by hard and flat surfaces. However, a physiological context is not found in single cells cultivated on coverslips. It requires the complex three-dimensional (3D) relationship of cells cultivated in extracellular matrix (ECM) gels, tissue sections, or in naturally developing organisms. In fact, the number of applications of 3D cell cultures in basic research as well as in drug discovery and toxicity testing has been increasing over the past few years. Unfortunately, the imaging of highly scattering multicellular specimens is still challenging. The main issues are the limited optical penetration depth, the phototoxicity, and the fluorophore bleaching. Light-sheet-based fluorescence microscopy (LSFM) overcomes many drawbacks of conventional fluorescence microscopy by using an orthogonal/azimuthal fluorescence arrangement with independent sets of lenses for illumination and detection. The basic idea is to illuminate the specimen from the side with a thin light sheet that overlaps with the focal plane of a wide-field fluorescence microscope. Optical sectioning and minimal phototoxic damage or photobleaching outside a small volume close to the focal plane are intrinsic properties of LSFM. We discuss the basic principles of LSFM and methods for the preparation, embedding, and imaging of 3D specimens used in the life sciences in an implementation of LSFM known as the single (or selective) plane illumination microscope (SPIM). PMID:24371323

Swoger, Jim; Pampaloni, Francesco; Stelzer, Ernst H K

2014-01-01

424

Ultrasound-modulated fluorescence based on a fluorophore-quencher-labeled microbubble system.  

PubMed

Ultrasound-modulated fluorescence from a fluorophore-quencher-labeled microbubble system driven by a single ultrasound pulse was theoretically quantified by solving a modified Herring equation (for bubble oscillation), a two-energy-level rate equation (for fluorophore excitation), and a diffusion equation (for light propagation in tissue). The efficiency of quenching caused by fluorescence resonance energy transfer (FRET) between the fluorophore and the quencher was modulated when the microbubble oscillates in size driven by the ultrasound pulse. Both intensity- and lifetime-based imaging methods are discussed in three different illumination modes of the excitation light: continuous wave (DC), frequency domain (FD), and time domain (TD). Results show that microbubble expansion opens a time period during which the quenching efficiency is dramatically reduced so that the emitted fluorescence strength and fluorophore lifetime are significantly increased. The modulation efficiency may even reach 100%. In addition, an important finding in this study is that in TD illumination mode, the modulated fluorescence photons may be temporally separated from the unmodulated photons, which makes the modulation efficiency limited only by thermal noise of the measurement system. PMID:19405771

Yuan, Baohong

2009-01-01

425