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1

Quantification of fluorophore concentration in vivo using two simple fluorescence-based measurement techniques.  

PubMed

The effect of photodynamic therapy treatments depends on the concentration of photosensitizer at the treatment site; thus a simple method to quantify concentration is desirable. This study compares the concentration of a fluorophore and sensitizer, aluminum phthalocyanine tetrasulfonate (AlPcS4), measured by two simple fluorescence-based techniques in vivo to post mortem chemical extraction and fluorometric assay of those tissues: skin, muscle, fascia, liver, and kidney (cortex and medulla). Fluorescence was excited and detected by a single optical fiber, or by an instrument that measured the ratio of the fluorescence and excitation reflectance. The in vivo measurements were compared to calibration measurements made in tissue-simulating phantoms to estimate the tissue concentrations. Reasonable agreement was observed between the concentration estimates of the two instruments in the lighter colored tissues (skin, muscle, and fascia). The in vivo measurements also agreed with the chemical extractions at low (< 0.6 microg/g) tissue concentrations, but underestimated higher tissue concentrations. Measurements of fluorescence lifetime in vivo demonstrated that AlPcS4 retains its mono-exponential decay in skin, muscle, and fascia tissues with a lifetime similar to that measured in aqueous tissue-simulating phantoms. In liver and kidney an additional short lifetime component was evident. PMID:15910081

Diamond, Kevin R; Malysz, Pawel P; Hayward, Joseph E; Patterson, Michael S

2005-01-01

2

A simple and sensitive label-free fluorescent approach for protein detection based on a Perylene probe and aptamer.  

PubMed

Highly sensitive detection of proteins is of great importance for effective clinical diagnosis and biomedical research. However, so far most detection methods rely on antibody-based immunoassays and are usually laborious and time-consuming with poor sensitivity. Here, we developed a simple and ultra-sensitive method to detect a biomarker protein-thrombin by taking advantage of the fluorescent probe Perylene tetracarboxylic acid diimide (PTCDI) derivatives and thrombin aptamer. The water-soluble dye PTCDI shows strong fluorescence in buffer solution for the existence of free dye monomer, but becomes weak after aggregation through self-assembly on nucleic acid aptamer. In the presence of thrombin, it specifically binds to thrombin aptamer which causes the conformational transition between aptamer and PTCDI and results in a significant fluorescence recovery. The results showed that as low as 40pM of thrombin could be detected by this method. The high sensitivity of the developed sensing system mainly attributes to the ultra-sensitivity of the fluorescence intensity changes of PTCDI. With the specificity of aptamer, the assay exhibited high selectivity for thrombin against three other proteins (bovine serum albumin, lysozyme, mouse IgG) and 1% diluted fetal bovine serum. The detection method might be extended to sensitive detection of a variety of proteins for its advantages of isothermal conditions required, simple and rapid without multiple separation and washing steps. PMID:25310484

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

2015-02-15

3

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

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

4

A pyrene-based simple but highly selective fluorescence sensor for Cu(2+) ions via a static excimer mechanism.  

PubMed

A pyrene-based simple fluorosensor has been synthesized by a one step process. It exhibited high selectivity towards Cu(2+) ions via fluorescence enhancement of monomer and excimer emission. The origin of excimer formation was examined and established to be of static in nature from the study of absorption and excitation spectra. The observed monomer and excimer emission in the presence and absence of Cu(2+) ion with varying pH was studied and provided probable justification. The effect of varying portions of water content in solvent on the sensor molecule was also examined. The sensor found its proper application in finding accurate and trace amount of Cu(2+) ions present in drinking water samples from various sources. The detection limit of the current sensor was found to be 4 × 10(-8) M. PMID:24133674

Sarkar, Soma; Roy, Swapnadip; Sikdar, Anindita; Saha, R N; Panja, Sujit S

2013-12-01

5

Simple method based on fluorescent detection for the determination of 4-hydroxycyclophosphamide in plasma.  

PubMed

Cyclophosphamide is a prodrug used both as a single drug and in combination chemotherapy. Cyclophosphamide is converted to its active metabolite (4-hydroxycyclophosphamide) by the cytochrome P450 enzymes. A liquid chromatography method including liquid-liquid extraction and protein precipitation in one step was developed to measure 4-hydroxycyclophosphamide in plasma. The 4-hydroxycyclophosphamide was stabilized and converted to a fluorescent dansylhydrazone derivative, which was chromatographed on a reverse-phase column and detected using a spectrofluorometric detector at excitation of 350 nm and emission of 550 nm. The limit of quantitation was 60 ng/mL and the between-day accuracy and precision were less than 9%. The method was applied to the analysis of plasma from patients who had received an intravenous infusion of 1 g/m(2) cyclophosphamide. PMID:12021633

Griskevicius, Laimonas; Meurling, Lennart; Hassan, Moustapha

2002-06-01

6

Simple and extremely efficient blue emitters based on mononuclear Cu(I)-halide complexes with delayed fluorescence.  

PubMed

Simple mononuclear Cu(I)-halide complexes, [CuX(PPh3)2(4-Mepy)] (X = Cl(-), Br(-), I(-); PPh3 = triphenylphosphine; 4-Mepy = 4-methylpyridine), were prepared. They exhibit blue light emission, with extremely high photoluminescence quantum yields approaching 100% in the crystals. Emission lifetime analyses and density functional theory calculations revealed that the bright blue light emission at room temperature is mainly delayed fluorescence originating from the singlet metal-to-ligand charge transfer (MLCT) state combined with the halide-to-ligand charge transfer (XLCT) state, ((1)(M + X)LCT), while that at 77 K is phosphorescence from the (3)(M + X)LCT transition state, due to the small singlet-triplet energy differences (?E = 940-1170 cm(-1)). The ternary ligand systems consisting of halide, bulky phosphine, and N-heteroaromatic ligands constitute inexpensive pure-blue-light-emitting materials, which can be fabricated by facile procedures such as simple manual grinding. PMID:25315634

Ohara, Hiroki; Kobayashi, Atsushi; Kato, Masako

2014-12-14

7

Simple Fluorescent Sensors Engineered with Catalytic DNA ‘MgZ’ Based on a Non-Classic Allosteric Design  

PubMed Central

Most NAE (nucleic acid enzyme) sensors are composed of an RNA-cleaving catalytic motif and an aptameric receptor. They operate by activating or repressing the catalytic activity of a relevant NAE through the conformational change in the aptamer upon target binding. To transduce a molecular recognition event to a fluorescence signal, a fluorophore-quencher pair is attached to opposite ends of the RNA substrate such that when the NAE cleaves the substrate, an increased level of fluorescence can be generated. However, almost all NAE sensors to date harbor either NAEs that cannot accommodate a fluorophore-quencher pair near the cleavage site or those that can accept such a modification but require divalent transition metal ions for catalysis. Therefore, the signaling magnitude and the versatility of current NAE sensors might not suffice for analytical and biological applications. Here we report an RNA-cleaving DNA enzyme, termed ‘MgZ’, which depends on Mg2+ for its activity and can accommodate bulky dye moieties next to the cleavage site. MgZ was created by in vitro selection. The selection scheme entailed acidic buffering and ethanol-based reaction stoppage to remove selfish DNAs. Characterization of MgZ revealed a three-way junction structure, a cleavage rate of 1 min?1, and 26-fold fluorescence enhancement. Two ligand-responsive NAE sensors were rationally designed by linking an aptamer sequence to the substrate of MgZ. In the absence of the target, the aptamer-linked substrate is locked into a conformation that prohibits MgZ from accessing the substrate. In the presence of the target, the aptamer releases the substrate, which induces MgZ-mediated RNA cleavage. The discovery of MgZ and the introduction of the above NAE sensor design strategy should facilitate future efforts in sensor engineering. PMID:18030352

Chiuman, William; Li, Yingfu

2007-01-01

8

Sensitive and simple detection of Escherichia coli strain based on time-resolved fluorescence DNA hybridization assay.  

PubMed

A two-probe tandem DNA hybridization assay based on time-resolved fluorescence was employed to detect Escherichia coli strain. The amino modified capture probe was covalently immobilized on the common glass slide surface. The Eu(TTA)(3)(5-NH(2)-phen) with the characteristics of long lifetime and intense luminescence was labeled with reporter probe. The original extracted DNA samples without the purification and amplification process were directly used in the hybridization assay. The concentration of capture probe, hybridization temperature, hybridization and washing time were optimized. The detection limit is about 1.49x10(3) CFU mL(-1) E. coli cells, which is comparable to the value of most microbiology methods. The proposed method has the advantages of easy operation, satisfactory sensitivity and specificity, which can provide a promising technique for monitoring the microorganisms. PMID:20226937

Ruan, Min; Niu, Cheng-Gang; Qin, Pin-Zhu; Zeng, Guang-Ming; Yang, Zhao-Hui; He, Hui; Huang, Jing

2010-04-01

9

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

PubMed

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

Suganya, Sivalingam; Velmathi, Sivan

2013-06-01

10

A highly selective and simple fluorescent sensor for mercury (II) ion detection based on cysteamine-capped CdTe quantum dots synthesized by the reflux method.  

PubMed

Cysteamine (CA)-capped CdTe quantum dots (QDs) (CA-CdTe QDs) were prepared by the reflux method and utilized as an efficient nano-sized fluorescent sensor to detect mercury (II) ions (Hg(2+) ). Under optimum conditions, the fluorescence quenching effect of CA-CdTe QDs was linear at Hg(2+) concentrations in the range of 6.0-450?nmol/L. The detection limit was calculated to be 4.0?nmol/L according to the 3? IUPAC criteria. The influence of 10-fold Pb(2+) , Cu(2+) and Ag(+) on the determination of Hg(2+) was?based on crude QDs). Furthermore, the detection sensitivity and selectivity were much improved relative to a sensor based on the CA-CdTe QDs probe, which was prepared using a one-pot synthetic method. This CA-CdTe QDs sensor system represents a new feasibility to improve the detection performance of a QDs sensor by changing the synthesis method. Copyright © 2014 John Wiley & Sons, Ltd. PMID:25263990

Ding, Xiaojie; Qu, Lingbo; Yang, Ran; Zhou, Yuchen; Li, Jianjun

2014-09-29

11

FLUORESCENCE-BASED SENSORS  

Microsoft Academic Search

The natural luminescent phenomena (from the Latin words “lumen” and “essentia”, i.e., “made of light”) such as northern lights (aurora borealis), marine brightness, glow-worms, shining putrid fish scales, “bluish”- appearing water when contained in certain wooden cups (quinine fluorescence), some stones heated at high temperatures with reducing agents (BaS phosphorescence), or light emitted while crushing sugar (triboluminescence) already fascinated our

Guillermo Orellana

12

Fluorescence-Based Sensors  

NASA Astrophysics Data System (ADS)

The natural luminescent phenomena (from the Latin words "lumen" and "essentia", i.e., "made of light") such as northern lights (aurora borealis), marine brightness, glow-worms, shining putrid fish scales, "bluish"- appearing water when contained in certain wooden cups (quinine fluorescence), some stones heated at high temperatures with reducing agents (BaS phosphorescence), or light emitted while crushing sugar (triboluminescence) already fascinated our ancestors. Nowadays we understand that ultraviolet and visible emission of light originates from a competitive deactivation pathway of the lowest electronic excited state of atoms and molecules that produces the so called luminescence (the sub-terms fluorescence and phosphorescence just designate whether the return of the excited to the ground state is an "allowed" or "forbidden" process, namely it is fast or slow, the loosely-defined border between them being a 1-?s-1 rate constant). Actually, luminescence is the only method to generate light in the known Universe regardless it is powered by the nuclear reactions in the stars, the ohmical heating in bulbs, an electric discharge, the absorption of light or a (bio)chemical reaction (chemiluminescence).

Orellana, Guillermo

13

Aptamer-Based Fluorescent Biosensors  

PubMed Central

Selected from random pools of DNA or RNA molecules through systematic evolution of ligands by exponential enrichment (SELEX), aptamers can bind to target molecules with high affinity and specificity, which makes them ideal recognition elements in the development of biosensors. To date, aptamer-based biosensors have used a wide variety of detection techniques, which are briefly summarized in this article. The focus of this review is on the development of aptamer-based fluorescent biosensors, with emphasis on their design as well as properties such as sensitivity and specificity. These biosensors can be broadly divided into two categories: those using fluorescently-labeled aptamers and others that employ label-free aptamers. Within each category, they can be further divided into “signal-on” and “signal-off” sensors. A number of these aptamer-based fluorescent biosensors have shown promising results in biological samples such as urine and serum, suggesting their potential applications in biomedical research and disease diagnostics. PMID:21838688

Wang, Rongsheng E.; Zhang, Yin; Cai, Jianfeng; Cai, Weibo; Gao, Ting

2011-01-01

14

Quasidistributed fluorescence-based optical fiber temperature sensor system  

Microsoft Academic Search

The use of multiple material fluorescence-based sensors, where each is optimized to a particular temperature range yet is pumped by the same light source, emitting over the same spectral region, makes for a very simple, convenient and promising optical arrangement which can be applied in real-time, quasidistributed temperature sensor systems. The fluorescence lifetime approach, which is an important technique to

T. Sun; Z. Y. Zhang; K. T. V. Grattan; A. W. Palmer

1998-01-01

15

A simple and sensitive fluorescence based biosensor for the determination of uric acid using H2O2-sensitive quantum dots/dual enzymes.  

PubMed

A novel optical detection system consisting of combination of uricase/HRP-CdS quantum dots (QDs) for the determination of uric acid in urine sample is described. The QDs was used as an indicator to reveal fluorescence property of the system resulting from enzymatic reaction of uricase and HRP (horseradish peroxidase), which is involved in oxidizing uric acid to allaintoin and hydrogen peroxide. The hydrogen peroxide produced was able to quench the QDs fluorescence, which was proportional to uric acid concentration. The system demonstrated sufficient activity of uricase and HRP at a ratio of 5U:5U and pH 7.0. The linearity of the system toward uric acid was in the concentration range of 125-1000µM with detection limit of 125µM. PMID:25113659

Azmi, Nur Ellina; Ramli, Noor Izaanin; Abdullah, Jaafar; Abdul Hamid, Mohammad Azmi; Sidek, Hamidah; Abd Rahman, Samsulida; Ariffin, Nurhayati; Yusof, Nor Azah

2015-05-15

16

Fluorescent sensors based on boronic acids  

NASA Astrophysics Data System (ADS)

Sensor systems have long been needed for detecting the presence in solution of certain chemically or biologically important species. Sensors are used in a wide range of applications from simple litmus paper that shows a single color change in acidic or basic environments to complex biological assays that use enzymes, antibodies and antigens to display binding events. With this work the use of boronic acids in the design and synthesis of sensors for saccharides (diols) will be presented. The fluorescent sensory systems rely on photoinduced electron transfer (PET) to modulate the observed fluorescence. When saccharides form cyclic boronate esters with boronic acids, the Lewis acidity of the boronic acid is enhanced and therefore the Lewis acid-base interaction between the boronic acid and a neighboring amine is strengthened. The strength of this acid-base interaction modulates the PET from the amine (acting as a quencher) to anthracene (acting as a fluorophore). These compounds show increased fluorescence at neutral pH through suppression of the PET from nitrogen to anthracene on saccharide binding. The general strategy for the development of saccharide selective systems will be discussed. The potential of the boronic acid based systems will be illustrated using the development of glucose and glucosamine selective fluorescent sensors as examples.

Cooper, Christopher R.; James, Tony D.

1999-05-01

17

A fluorescence-based rapid screening assay for cytotoxic compounds  

Microsoft Academic Search

A simple fluorescence-based assay was developed for the rapid screening of potential cytotoxic compounds generated by combinatorial chemistry. The assay is based on detection of nuclear green fluorescent protein (GFP) staining of a human cervical cancer cell line (HeLa) carrying an integrated histone H2B-GFP fusion gene. Addition of a cytotoxic compound to the HeLa-GFP cells results in the eventual degradation

Jessica Montoya; Armando Varela-Ramirez; Abril Estrada; Luis E. Martinez; Kristine Garza; Renato J. Aguilera

2004-01-01

18

Radiative Transport Based Frequency Domain Fluorescence Tomography  

PubMed Central

We report the development of radiative transport model based fluorescence optical tomography from frequency domain boundary measurements. The coupled radiative transport model for describing NIR fluorescence propagation in tissue is solved by a novel software based on the established Attila™ particle transport simulation platform. The proposed scheme enables the prediction of fluorescence measurements with non-contact sources and detectors at minimal computational cost. An adjoint transport solution based fluorescence tomography algorithm is implemented on dual grids to efficiently assemble the measurement sensitivity Jacobian matrix. Finally, we demonstrate fluorescence tomography on a realistic computational mouse model to locate nM to ?M fluorophore concentration distributions in simulated mouse organs. PMID:18364555

Joshi, Amit; Rasmussen, John C.; Sevick-Muraca, Eva M.; Wareing, Todd A.; McGhee, John

2011-01-01

19

Simple and robust image-based autofocusing for digital microscopy.  

PubMed

A simple image-based autofocusing scheme for digital microscopy is demonstrated that uses as few as two intermediate images to bring the sample into focus. The algorithm is adapted to a commercial inverted microscope and used to automate brightfield and fluorescence imaging of histopathology tissue sections. PMID:18545580

Yazdanfar, Siavash; Kenny, Kevin B; Tasimi, Krenar; Corwin, Alex D; Dixon, Elizabeth L; Filkins, Robert J

2008-06-01

20

Fluorescent sensors based on bacterial fusion proteins  

NASA Astrophysics Data System (ADS)

Fluorescence proteins are widely used as markers for biomedical and technological purposes. Therefore, the aim of this project was to create a fluorescent sensor, based in the green and cyan fluorescent protein, using bacterial S-layers proteins as scaffold for the fluorescent tag. We report the cloning, expression and purification of three S-layer fluorescent proteins: SgsE-EGFP, SgsE-ECFP and SgsE-13aa-ECFP, this last containing a 13-amino acid rigid linker. The pH dependence of the fluorescence intensity of the S-layer fusion proteins, monitored by fluorescence spectroscopy, showed that the ECFP tag was more stable than EGFP. Furthermore, the fluorescent fusion proteins were reassembled on silica particles modified with cationic and anionic polyelectrolytes. Zeta potential measurements confirmed the particle coatings and indicated their colloidal stability. Flow cytometry and fluorescence microscopy showed that the fluorescence of the fusion proteins was pH dependent and sensitive to the underlying polyelectrolyte coating. This might suggest that the fluorescent tag is not completely exposed to the bulk media as an independent moiety. Finally, it was found out that viscosity enhanced the fluorescence intensity of the three fluorescent S-layer proteins.

Prats Mateu, Batirtze; Kainz, Birgit; Pum, Dietmar; Sleytr, Uwe B.; Toca-Herrera, José L.

2014-06-01

21

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. PMID:23502324

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

2013-01-01

22

Sensitive detection of cysteine based on fluorescent silver clusters.  

PubMed

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 alpha-amino acids were present. By virtue of the specific response, a new, simple, and sensitive fluorescent method for detecting cysteine has been developed based on Ag clusters. The present assay allows for the selective determination of cysteine in the range of 2.5 x 10(-8) to 6.0 x 10(-6)M with a detection limit of 20 nM at a signal-to-noise ratio of 3. Based on the absorption and fluorescence studies, we suggested that cysteine quenched the emission by the thiol-adsorption-accelerated oxidation of the emissive Ag clusters. The present study shows a promising step toward the application of silver clusters, a new class of attractive fluorescence probes. PMID:18823770

Shang, Li; Dong, Shaojun

2009-02-15

23

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. PMID:24465818

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

2014-01-01

24

A simple method for fabrication of enhanced fluorescence substrate on TEM copper grid  

NASA Astrophysics Data System (ADS)

A simple method to fabricate enhanced fluorescence substrates was experimentally demonstrated. The fabricated substrate, consisting of silver dendrites, was manufactured by a modified galvanic displacement process between Ag ions and TEM grid at room temperature. Substrate enhancement efficiency, which was evaluated from fluorescence spectrum intensities of the adsorbed Rhodamine 6G (Rh6G) molecules, was found to increase rapidly with reaction time. The observation highlights the importance of strong coupling effects between silver nanobranches and the variation of SEF efficiency can be qualitatively explained with the local surface plasmon resonance model of coupled silver nanostructures. As a result, with a laser, a spectrometer, some second-hand TEM grids, and simple chemical agents, we can easily fabricate the enhanced substrate, which can be applied to study surface enhanced fluorescence, one of the research focuses currently.

Dong, Jun; Du, Yabing; Qi, Jianxia; Zhang, Wenwen; Li, Wenyang

2013-09-01

25

A SIMPLE EVENT-BASED PID CONTROLLER  

Microsoft Academic Search

A simple event-based PID controller is presented. It is shown that it is possible to obtain large reductions in CPU utilization with only minor control performance degradation. Simulations on a double-tank process are presented.

Karl-Erik Årzén

1999-01-01

26

A simple method to fluorescently label pericytes in the CNS and skeletal muscle.  

PubMed

Pericytes play important roles in vascular control and may form an important part of the blood brain barrier. Here we introduce a simple method for fluorescently labelling pericytes to enable further studies in live or fixed tissue of rats and mice. Following intraperitoneal injection, the fluorescent tracer Fluorogold was rapidly taken up into vascular endothelial cells, and within 3h in the central nervous system appeared within small perivascular cells with a morphology consistent with pericytes. These Fluorogold labelled cells were pericytes since they displayed immunoreactivity for platelet derived growth factor receptor ? and were closely associated with isolectin B4 binding to endothelial cells. Pericytes in skeletal muscle were also labelled with this method, but not those within the heart, lungs or kidney. This simple method could therefore be applied for labelling pericytes in a wide variety of studies, including live cell imaging or immunohistochemistry. PMID:23764127

Edwards, Ian J; Singh, Mukti; Morris, Sebastian; Osborne, Lydia; Le Ruez, Tom; Fuad, Mustapha; Deuchars, Susan A; Deuchars, Jim

2013-09-01

27

Portable optical oxygen sensor based on time-resolved fluorescence.  

PubMed

A new, simple signal processing, low-cost technique for the fabrication of a portable oxygen sensor based on time-resolved fluorescence is described. The sensing film uses the oxygen sensing dye platinum meso-tetra (pentfluorophenyl) porphyrin (PtTFPP) embedded in a polymer matrix. The ratio ?0/?100 measures sensitivity of the sensing film, where ?0 and ?100 represent the detected fluorescence lifetimes from the sensing film exposed to 100% nitrogen and 100% oxygen, respectively. The experimental results reveal that the PtTFPP-doped oxygen sensor has a sensitivity of 2.2 in the 0%-100% range. A preparation procedure for coating the photodiodes with the oxygen sensor film that produces repetitive and reliable sensing devices is proposed. The developed time-resolved optical oxygen sensor is portable, low-cost, has simple signal processing, and lacks optical filter elements. It is a cost-effective alternative to traditional electrochemical-based oxygen sensors and provides a platform for other optical based sensors. PMID:25402987

Chu, Cheng-Shane; Chu, Ssu-Wei

2014-11-10

28

A fluorescence-based rapid screening assay for cytotoxic compounds.  

PubMed

A simple fluorescence-based assay was developed for the rapid screening of potential cytotoxic compounds generated by combinatorial chemistry. The assay is based on detection of nuclear green fluorescent protein (GFP) staining of a human cervical cancer cell line (HeLa) carrying an integrated histone H2B-GFP fusion gene. Addition of a cytotoxic compound to the HeLa-GFP cells results in the eventual degradation of DNA and loss of the GFP nuclear fluorescence. Using this assay, we screened 11 distinct quinone derivatives and found that several of these compounds were cytotoxic. These compounds are structurally related to plumbagin an apoptosis-inducing naphthoquinone isolated from Black Walnut. In order to determine the mechanism by which cell death was induced, we performed additional experiments with the most cytotoxic quinones. These compounds were found to induce morphological changes (blebbing and nuclear condensation) consistent with induction of apoptosis. Additional tests revealed that the cytotoxic compounds induce both necrotic and apoptotic modes of death. PMID:15555600

Montoya, Jessica; Varela-Ramirez, Armando; Estrada, Abril; Martinez, Luis E; Garza, Kristine; Aguilera, Renato J

2004-12-24

29

Antigen detection based on background fluorescence quenching immunochromatographic assay.  

PubMed

Gold immunochromatographic assay (GICA) has been around for quite a while, but it is qualitative in the vast majority of applications. A fast, simple and quantitative GICA is in call for better medicine. In the current study, we have established a novel, quantitative GICA based on fluorescence quenching and nitrocellulose membrane background signals, called background fluorescence quenching immunochromatographic assay (bFQICA). Using model analyte alpha-fetoprotein (AFP), the present study assessed the performance of bFQICA in numerous assay aspects. With serial dilutions of the international AFP standard, standard curves for the calculation of AFP concentration were successfully established. At 10 and 100ngmL(-1) of the international AFP standard, the assay variability was defined with a coefficient of variance at 10.4% and 15.2%, respectively. For samples with extended range of AFP levels, bFQICA was able to detect AFP at as low as 1ngmL(-1). Fluorescence in bFQICA strips stayed constant over months. A good correlation between the results from bFQICA and from a well-established Roche electrochemiluminescence immunoassay was observed in 27 serum samples (r=0.98, p<0.001). In conclusion, our study has demonstrated distinctive features of bFQICA over conventional GICA, including utilization of a unique fluorescence ratio between nitrocellulose membrane background and specific signals (F1/F2) to ensure accurate measurements, combined qualitative and quantitative capabilities, and exceptionally high sensitivity for detection of very low levels of antigens. All of these features could make bFQICA attractive as a model for antigen-antibody complex based GICA, and could promote bFQICA to a broad range of applications for investigation of a variety of diseases. PMID:25109860

Chen, Xiangjun; Xu, Yangyang; Yu, Jinsheng; Li, Jiutong; Zhou, Xuelei; Wu, Chuanyong; Ji, Qiuliang; Ren, Yuan; Wang, Liqun; Huang, Zhengyi; Zhuang, Hanling; Piao, Long; Head, Richard; Wang, Yajie; Lou, Jiatao

2014-09-01

30

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

NASA Astrophysics Data System (ADS)

A quinoline-based simple receptor (bis(2-quinolinylmethyl)benzylamine = 1) as a Zn2+ selective fluorescent chemosensor showed a large fluorescent enhancement with a blue shift in the presence of Zn2+ 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 Zn2+ from Cd2+. The binding mode of 1 and Zn2+ was found to be a 1:1 and confirmed by Job plot, 1H NMR titration and ESI-mass spectrometry analysis.

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

2014-01-01

31

Quick and simple estimation of bacteria using a fluorescent paracetamol dimer-Au nanoparticle composite  

NASA Astrophysics Data System (ADS)

Rapid, simple and sensitive detection of bacterial contamination is critical for safeguarding public health and the environment. Herein, we report an easy method of detection as well as enumeration of the bacterial cell number on the basis of fluorescence quenching of a non-antibacterial fluorescent nanocomposite, consisting of paracetamol dimer (PD) and Au nanoparticles (NPs), in the presence of bacteria. The composite was synthesized by reaction of paracetamol (p-hydroxyacetanilide) with HAuCl4. The Au NPs of the composite were characterized using UV-Vis spectroscopy, transmission electron microscopy (TEM), X-ray diffraction and selected area electron diffraction analysis. The paracetamol dimer in the composite showed emission peak at 435 nm when excited at 320 nm. The method successfully detected six bacterial strains with a sensitivity of 100 CFU mL-1. The Gram-positive and Gram-negative bacteria quenched the fluorescence of the composite differently, making it possible to distinguish between the two. The TEM analysis showed interaction of the composite with bacteria without any apparent damage to the bacteria. The chi-square test established the accuracy of the method. Quick, non-specific and highly sensitive detection of bacteria over a broad range of logarithmic dilutions within a short span of time demonstrates the potential of this method as an alternative to conventional methods.Rapid, simple and sensitive detection of bacterial contamination is critical for safeguarding public health and the environment. Herein, we report an easy method of detection as well as enumeration of the bacterial cell number on the basis of fluorescence quenching of a non-antibacterial fluorescent nanocomposite, consisting of paracetamol dimer (PD) and Au nanoparticles (NPs), in the presence of bacteria. The composite was synthesized by reaction of paracetamol (p-hydroxyacetanilide) with HAuCl4. The Au NPs of the composite were characterized using UV-Vis spectroscopy, transmission electron microscopy (TEM), X-ray diffraction and selected area electron diffraction analysis. The paracetamol dimer in the composite showed emission peak at 435 nm when excited at 320 nm. The method successfully detected six bacterial strains with a sensitivity of 100 CFU mL-1. The Gram-positive and Gram-negative bacteria quenched the fluorescence of the composite differently, making it possible to distinguish between the two. The TEM analysis showed interaction of the composite with bacteria without any apparent damage to the bacteria. The chi-square test established the accuracy of the method. Quick, non-specific and highly sensitive detection of bacteria over a broad range of logarithmic dilutions within a short span of time demonstrates the potential of this method as an alternative to conventional methods. Electronic supplementary information (ESI) available. See DOI: 10.1039/c2nr11837h

Sahoo, Amaresh Kumar; Sharma, Shilpa; Chattopadhyay, Arun; Ghosh, Siddhartha Sankar

2012-02-01

32

Simple, Script-Based Science Processing Archive  

NASA Technical Reports Server (NTRS)

The Simple, Scalable, Script-based Science Processing (S4P) Archive (S4PA) is a disk-based archival system for remote sensing data. It is based on the data-driven framework of S4P and is used for data transfer, data preprocessing, metadata generation, data archive, and data distribution. New data are automatically detected by the system. S4P provides services such as data access control, data subscription, metadata publication, data replication, and data recovery. It comprises scripts that control the data flow. The system detects the availability of data on an FTP (file transfer protocol) server, initiates data transfer, preprocesses data if necessary, and archives it on readily available disk drives with FTP and HTTP (Hypertext Transfer Protocol) access, allowing instantaneous data access. There are options for plug-ins for data preprocessing before storage. Publication of metadata to external applications such as the Earth Observing System Clearinghouse (ECHO) is also supported. S4PA includes a graphical user interface for monitoring the system operation and a tool for deploying the system. To ensure reliability, S4P continuously checks stored data for integrity, Further reliability is provided by tape backups of disks made once a disk partition is full and closed. The system is designed for low maintenance, requiring minimal operator oversight.

Lynnes, Christopher; Hegde, Mahabaleshwara; Barth, C. Wrandle

2007-01-01

33

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

PubMed

ABSTRACT. In recent years, the use of light emitting diodes (LEDs) has become commonplace in fluorescence microscopy. LEDs are economical and easy to couple to commercial microscopes, and they provide powerful and stable light that can be triggered by transistor-transistor logic 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 localized illumination, typically achieved using lasers. Here we show that insertion of a long-pass (>411??nm) filter with an 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 to 20 ?m. We tested our system by performing calcium imaging experiments combined with L-glutamate or N-methyl-D-aspartic acid (NMDA) photorelease 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 budgets to run similar experiments in a variety of physiological applications. PMID:23764747

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

2013-06-01

34

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

35

Teaching about photosynthesis with simple equipment: analysis of light-induced changes in fluorescence and reflectance of plant leaves.  

PubMed

Solar energy absorbed by plants results in either reflection or absorption. The latter results in photosynthesis, fluorescence, or heat. Measurements of fluorescence changes have been used for monitoring processes associated with photosynthesis. A simple method to follow changes in leaf fluorescence and leaf reflectance associated with nonphotochemical quenching and light acclimation of leaves is described. The main equipment needed consists of a green-light emitting laser pointer, a digital camera, and a personal computer equipped with the camera acquisition software and the programs ImageJ and Excel. Otherwise, only commonly available cheap materials are required. PMID:23728512

Björn, Lars Olof; Li, Shaoshan

2013-10-01

36

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...

37

Fluorescence-based ion-sensing with colloidal particles.  

PubMed

Particle-based fluorescence sensors for the quantification of specific ions can be made by coupling ion-sensitive fluorophores to carrier particles, or by using intrinsically fluorescent particles whose fluorescence properties depend on the concentration of the ions. Despite the advantages of such particle-based sensors for the quantitative detection of ions, such as the possibility to tune the surface chemistry and thus entry portal of the sensor particles to cells, they have also some associated problems. Problems involve for example crosstalk of the ion-sensitive fluorescence read-out with pH, or spectral overlap of the emission spectra of different fluorescent particles in multiplexing formats. Here the benefits of using particle-based fluorescence sensors, their limitations and strategies to overcome these limitations will be described and exemplified with selected examples. PMID:25279439

Ashraf, Sumaira; Carrillo-Carrion, Carolina; Zhang, Qian; Soliman, Mahmoud G; Hartmann, Raimo; Pelaz, Beatriz; Del Pino, Pablo; Parak, Wolfgang J

2014-10-01

38

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

39

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. PMID:23620743

Stofanko, Martin; Gonçalves-Dornelas, Higgor; Cunha, Pricila Silva; Pena, Heloísa B.; Vianna-Morgante, Angela M.; Pena, Sérgio Danilo Junho

2013-01-01

40

Naphthoxazole-based singlet oxygen fluorescent probes.  

PubMed

In this study, we report the synthesis and photochemical behavior of a new family of photoactive compounds to assess its potential as singlet oxygen ((1)O2) probes. The candidate dyads are composed by a (1)O2 trap plus a naphthoxazole moiety linked directly or through an unsaturated bond to the oxazole ring. In the native state, the inherent great fluorescence of the naphthoxazole moiety is quenched; but in the presence of (1)O2, generated by the addition and appropriate irradiation of an external photosensitizer, a photooxidation reaction occurs leading to the formation of a new chemical entity whose fluorescence is two orders of magnitude higher than that of the initial compound, at the optimal selected wavelength. The presented dyads outperform the commonly used indirect fluorescent (1)O2 probes in terms of fluorescence enhancement maintaining the required specificity for (1)O2 detection in solution. PMID:23730728

Ruiz-González, Rubén; Zanocco, Renzo; Gidi, Yasser; Zanocco, Antonio L; Nonell, Santi; Lemp, Else

2013-01-01

41

Characterization of Flavin-Based Fluorescent Proteins: An Emerging Class of Fluorescent Reporters  

PubMed Central

Fluorescent reporter proteins based on flavin-binding photosensors were recently developed as a new class of genetically encoded probes characterized by small size and oxygen-independent maturation of fluorescence. Flavin-based fluorescent proteins (FbFPs) address two major limitations associated with existing fluorescent reporters derived from the green fluorescent protein (GFP)–namely, the overall large size and oxygen-dependent maturation of fluorescence of GFP. However, FbFPs are at a nascent stage of development and have been utilized in only a handful of biological studies. Importantly, a full understanding of the performance and properties of FbFPs as a practical set of biological probes is lacking. In this work, we extensively characterize three FbFPs isolated from Pseudomonas putida, Bacillus subtilis, and Arabidopsis thaliana, using in vitro studies to assess probe brightness, oligomeric state, maturation time, fraction of fluorescent holoprotein, pH tolerance, redox sensitivity, and thermal stability. Furthermore, we validate FbFPs as stable molecular tags using in vivo studies by constructing a series of FbFP-based transcriptional constructs to probe promoter activity in Escherichia coli. Overall, FbFPs show key advantages as broad-spectrum biological reporters including robust pH tolerance (4–11), thermal stability (up to 60°C), and rapid maturation of fluorescence (<3 min.). In addition, the FbFP derived from Arabidopsis thaliana (iLOV) emerged as a stable and nonperturbative reporter of promoter activity in Escherichia coli. Our results demonstrate that FbFP-based reporters have the potential to address key limitations associated with the use of GFP, such as pH-sensitive fluorescence and slow kinetics of fluorescence maturation (10–40 minutes for half maximal fluorescence recovery). From this view, FbFPs represent a useful new addition to the fluorescent reporter protein palette, and our results constitute an important framework to enable researchers to implement and further engineer improved FbFP-based reporters with enhanced brightness and tighter flavin binding, which will maximize their potential benefits. PMID:23741385

Mukherjee, Arnab; Schroeder, Charles M.

2013-01-01

42

Radiative transport-based frequency-domain fluorescence tomography  

NASA Astrophysics Data System (ADS)

We report the development of radiative transport model-based fluorescence optical tomography from frequency-domain boundary measurements. The coupled radiative transport model for describing NIR fluorescence propagation in tissue is solved by a novel software based on the established Attila™ particle transport simulation platform. The proposed scheme enables the prediction of fluorescence measurements with non-contact sources and detectors at a minimal computational cost. An adjoint transport solution-based fluorescence tomography algorithm is implemented on dual grids to efficiently assemble the measurement sensitivity Jacobian matrix. Finally, we demonstrate fluorescence tomography on a realistic computational mouse model to locate nM to µM fluorophore concentration distributions in simulated mouse organs.

Joshi, Amit; Rasmussen, John C.; Sevick-Muraca, Eva M.; Wareing, Todd A.; McGhee, John

2008-04-01

43

Radiative transport-based frequency-domain fluorescence tomography.  

PubMed

We report the development of radiative transport model-based fluorescence optical tomography from frequency-domain boundary measurements. The coupled radiative transport model for describing NIR fluorescence propagation in tissue is solved by a novel software based on the established Attila particle transport simulation platform. The proposed scheme enables the prediction of fluorescence measurements with non-contact sources and detectors at a minimal computational cost. An adjoint transport solution-based fluorescence tomography algorithm is implemented on dual grids to efficiently assemble the measurement sensitivity Jacobian matrix. Finally, we demonstrate fluorescence tomography on a realistic computational mouse model to locate nM to microM fluorophore concentration distributions in simulated mouse organs. PMID:18364555

Joshi, Amit; Rasmussen, John C; Sevick-Muraca, Eva M; Wareing, Todd A; McGhee, John

2008-04-21

44

A novel aptasensor based on silver nanoparticle enhanced fluorescence.  

PubMed

In the present study, we report a novel aptasensor based on silver nanoparticle enhanced fluorescence for the detection of adenosine. First, the distance dependence nature of silver nanoparticle enhanced fluorescence was investigated through fluorescent dyes modified oligonucleotides to control the spacing distance between dyes and AgNP. The results showed that the fluorescence intensity reached the maximum value with the spacing distance of dyes about 8 nm from AgNP surface. The fluorescence intensity decreases when the spacing distance is either above or below this value. Based on this result, a fluorescence switch is constructed. In the "OFF" state, without the target molecules, there is a greater spacing distance between the Cy3 dyes and the AgNP giving comparatively lower fluorescence intensity. While in the "ON" state, in the presence of target molecules, the fluorescence signals increased for the conformation structure change of the aptamer which shorten the spacing distance between the Cy3 dyes and the AgNP to 8 nm. Using adenosine as target, the aptasensor produced a linear range from 200 nM to 200 ?M with a correlation coefficient of 0.9949 and the detection limit was 48 nM estimated using 3?. The aptasensor was also found to be specific in targeting adenosine. The presented method shows a new strategy of combining aptamer recognition and silver nanoparticle for fluorescence signal enhancement and increasing sensitivity. PMID:22209330

Wang, Ying; Li, Zhonghui; Li, Hui; Vuki, Maika; Xu, Danke; Chen, Hong-Yuan

2012-02-15

45

Simple method for fluorescence DNA in situ hybridization to squashed chromosomes.  

PubMed

DNA in situ hybridization (DNA ISH) is a commonly used method for mapping sequences to specific chromosome regions. This approach is particularly effective at mapping highly repetitive sequences to heterochromatic regions, where computational approaches face prohibitive challenges. Here we describe a streamlined protocol for DNA ISH that circumvents formamide washes that are standard steps in other DNA ISH protocols. Our protocol is optimized for hybridization with short single strand DNA probes that carry fluorescent dyes, which effectively mark repetitive DNA sequences within heterochromatic chromosomal regions across a number of different insect tissue types. However, applications may be extended to use with larger probes and visualization of single copy (non-repetitive) DNA sequences. We demonstrate this method by mapping several different repetitive sequences to squashed chromosomes from Drosophila melanogaster neural cells and Nasonia vitripennis spermatocytes. We show hybridization patterns for both small, commercially synthesized probes and for a larger probe for comparison. This procedure uses simple laboratory supplies and reagents, and is ideal for investigators who have little experience with performing DNA ISH. PMID:25591075

Larracuente, Amanda M; Ferree, Patrick M

2015-01-01

46

A simple method for combined fluorescence in situ hybridization and immunocytochemistry.  

PubMed

By combining in situ hybridization (ISH) and immunocytochemistry (IC), microscopic topological localization of mRNAs and proteins can be determined. Although this technique can be applied to a variety of tissues, it is particularly important for use on neuronal cells which are morphologically complex and in which specific mRNAs and proteins are located in distinct subcellular domains such as dendrites and dendritic spines. One common technical problem for combined ISH and IC is that the signal for immunocytochemical localization of proteins often becomes much weaker after conducting ISH. In this manuscript, we report a simplified but robust protocol that allows immunocytochemical localization of proteins after ISH. In this protocol, we fix cultured cortical or hippocampal neurons with 4% paraformaldehyde (PFA), rinse briefly in PBS, and then further fix the cells with C methanol. Our method has several major advantages over previously described ones in that (1) it is simple, as it is just consecutive routine fixation procedures, (2) it does not require any special alteration to the fixation procedures such as changes in salt concentration, and (3) it can be used with antibodies that are compatible with either methanol (MeOH-) or PFA-fixed target proteins. To our best knowledge, we are the first to employ this fixation method for fluorescence ISH + IC. PMID:17846501

Moon, Il Soo; Cho, Sun-Jung; Jin, Ingnyol; Walikonis, Randall

2007-08-31

47

Boronate-Based Fluorescent Probes for Imaging Cellular Hydrogen Peroxide  

E-print Network

Boronate-Based Fluorescent Probes for Imaging Cellular Hydrogen Peroxide Evan W. Miller, Aaron E applications of the Peroxysensor family, a new class of fluorescent probes for hydrogen peroxide, are presented In particular, hydrogen peroxide is a major ROS byproduct in living organisms and a common marker for oxidative

Pralle, Arnd

48

Fluorescent Sensors for Zn2+ Based on a Fluorescein Platform  

E-print Network

Fluorescent Sensors for Zn2+ Based on a Fluorescein Platform: Synthesis, Properties fluorescent sensors for Zn2+ that utilize fluorescein as a reporting group, Zinpyr-1 and Zinpyr-2, have been. Both Zinpyr sensors have excitation and emission wavelengths in the visible range (500 nm

Tsien, Roger Y.

49

Disposable nitrate-selective optical sensor based on fluorescent dye  

Technology Transfer Automated Retrieval System (TEKTRAN)

A simple, disposable thin-film optical nitrate sensor was developed. The sensor was fabricated by applying a nitrate-selective polymer membrane on the surface of a thin polyester film. The membrane was composed of polyvinylchloride (PVC), plasticizer, fluorescent dye, and nitrate-selective ionophore...

50

Simple process of hybrid white quantum dot/organic light-emitting diodes by using quantum dot plate and fluorescence  

NASA Astrophysics Data System (ADS)

In this work, the simple process of hybrid quantum dot (QD)/organic light-emitting diode (OLED) was proposed to apply a white illumination light by using QD plate and organic fluorescence. Conventional blue fluorescent OLEDs were firstly fabricated and then QD plates of various concentrations, which can be controlled of UV–vis absorption and photoluminescence spectrum, were attached under glass substrate of completed blue devices. The suggested process indicates that we could fabricate the white device through very simple process without any deposition of orange or red organic emitters. Therefore, this work would be demonstrated that the potential simple process for white applications can be applied and also can be extended to additional research on light applications.

Lee, Ho Won; Lee, Ki-Heon; Lee, Jae Woo; Kim, Jong-Hoon; Yang, Heesun; Kim, Young Kwan

2015-02-01

51

Mosaic-Detector-Based Fluorescence Spectral Imager  

NASA Technical Reports Server (NTRS)

A battery-powered, pen-sized, portable instrument for measuring molecular fluorescence spectra of chemical and biological samples in the field has been proposed. Molecular fluorescence spectroscopy is among the techniques used most frequently in laboratories to analyze compositions of chemical and biological samples. Heretofore, it has been possible to measure fluorescence spectra of molecular species at relative concentrations as low as parts per billion (ppb), with a few nm spectral resolution. The proposed instrument would include a planar array (mosaic) of detectors, onto which a fluorescence spectrum would be spatially mapped. Unlike in the larger laboratory-type molecular fluorescence spectrometers, mapping of wavelengths to spatial positions would be accomplished without use of relatively bulky optical parts. The proposed instrument is expected to be sensitive enough to enable measurement of spectra of chemical species at relative concentrations <1 ppb, with spectral resolution that could be tailored by design to be comparable to a laboratory molecular fluorescence spectrometer. The proposed instrument (see figure) would include a button-cell battery and a laser diode, which would generate the monochromatic ultraviolet light needed to excite fluorescence in a sample. The sample would be held in a cell bounded by far-ultraviolet-transparent quartz or optical glass. The detector array would be, more specifically, a complementary metal oxide/ semiconductor or charge-coupled- device imaging photodetector array, the photodetectors of which would be tailored to respond to light in the wavelength range of the fluorescence spectrum to be measured. The light-input face of the photodetector array would be covered with a matching checkerboard array of multilayer thin film interference filters, such that each pixel in the array would be sensitive only to light in a spectral band narrow enough so as not to overlap significantly with the band of an adjacent pixel. The wavelength interval between adjacent pixels (and, thus, the spectral resolution) would typically be chosen by design to be approximately equal to the width of the total fluorescence wavelength range of interest divided by the number of pixels. The unitary structure comprising the photodetector array overlaid with the matching filter array would be denoted a hyperspectral mosaic detector (HMD) array.

Son, Kyung-Ah; Moon, Jeong

2007-01-01

52

Measurement of changes in cell volume based on fluorescence quenching.  

PubMed

The intracellular fluorescence of 6-methoxy-N-(3-sulfopropyl)-quinolinium (SPQ), a Cl(-) -sensitive fluorescent dye, is quenched by intracellular organic anions and proteins of unknown identity. The concentration of these intracellular quenchers (ICQs), however, is dependent on cell volume. In the absence of Cl-, changes in the observed SPQ fluorescence may therefore reflect changes in cell volume. This concept has been applied to determine relative changes in cell volume of cultured corneal endothelium in response to anisosmotic shocks, using NO3- as the Cl- substituent. SPQ fluorescence increased with decreasing osmolarity and vice versa. A 20 mosM hypertonic shock was needed to detect a change in SPQ fluorescence with a signal-to-noise ratio of >25. Assuming dynamic quenching by ICQs, we applied an extension of the Stern-Volmer equation to develop a simple relationship between the measured SPQ fluorescence and relative changes in cell volume. For large hyposmotic shocks, regulatory volume decrease (RVD) was observed. The rate of RVD could be enhanced by exposure to 0.5 microM gramicidin in low-Na+ Ringer solution (i.e., K+-NO3- efflux), indicating that K+ conductance is rate limiting for RVD. These results demonstrate the principle of using fluorescence quenching to measure changes in cell volume in real time. Because SPQ is sensitive to Cl-, its usefulness as a quenching probe is limited. However, a structure-activity study can be expected to yield useful Cl(-)-insensitive analogs. PMID:9142868

Srinivas, S P; Bonanno, J A

1997-04-01

53

A WS2 nanosheet-based platform for fluorescent DNA detection via PNA-DNA hybridization.  

PubMed

The WS2 nanosheet, a two-dimensional layered nanomaterial, shows high fluorescence quenching ability for the dye-labeled ssDNA. Currently, most of the fluorescent DNA detection methods employ DNA as a probe for recognition of target DNA. Peptide nucleic acid (PNA) is a DNA mimic but a neutral molecule, showing superior hybridization properties to target DNA. Based on the unique properties of WS2 nanosheet and PNA-DNA hybridization, we have developed a rapid, simple, stable and sensitive approach for DNA detection based on good fluorescence quenching ability of the WS2 nanosheet as well as high binding affinity and specificity of PNA to DNA. This novel assay is capable of exhibiting high sensitivity and specificity with a detection limit of 500 pM, and discriminating between single bases. PMID:25426801

Wang, Shuting; Zhang, Yulin; Ning, Yong; Zhang, Guo-Jun

2014-12-15

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

Novel pyrazoline-based selective fluorescent probe for the detection of hydrazine.  

PubMed

A novel pyrazoline-based fluorescent probe, 2-[4-(3,5-diphenyl-4,5-dihydro-pyrazol-1-yl)-benzylidene]-malononitrile, with a simple structure and low detection limit (6.16×10(-6)M) for the detection of hydrazine is designed and synthesized. The probe responds selectively to hydrazine over other molecules with marked fluorescence enhancement. The probe can detect hydrazine effectively at pH 5.0-9.0 with a special emission wavelength at 520nm. Moreover, the probe can be used to detect hydrazine from variety of natural source water. PMID:25498821

Zheng, Xiao-Xin; Wang, Sheng-Qing; Wang, Hao-Yan; Zhang, Rong-Rong; Liu, Jin-Ting; Zhao, Bao-Xiang

2015-03-01

56

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

57

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

58

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

59

Fluorescent siderophore-based chemosensors: iron(III) quantitative determinations  

Microsoft Academic Search

A highly sensitive and selective method is described for a rapid and easy determination of iron(III). This procedure is based\\u000a on fluorimetric detection combined with the attractive properties of siderophores and biomimetic ligands, which are strong\\u000a and selective ferric chelators. Azotobactin ?, a bacterial fluorescent siderophore, three fluorescent derivatives of desferriferrioxamine\\u000a B with a linear structure (NBD-, MA-, NCP-desferriferrioxamine B)

Tania Palanché; Frank Marmolle; Mohamed A. Abdallah; Abraham Shanzer; Anne-Marie Albrecht-Gary

1999-01-01

60

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

61

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. PMID:23787643

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

2013-01-01

62

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

63

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

64

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. PMID:24988439

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

2014-01-01

65

A Simple DNA-Based Translation System  

PubMed Central

We have used DNA double crossover (DX) molecules to produce a translation system that generates unique molecular products. The particular species of DX molecule used contains an even number of half-turns between crossover points, so there is a continuous strand on both sides of the molecule. One of these strands acts as the input strand containing the message, and a second strand acts as the product of translation. The crossover strands carry the ‘code’ that connects the two sides of the molecule. This system is more robust, more extendable, and simpler than previous DNA-based translation systems that have been reported. It is designed to be useful in a variety of applications that utilize the concept of translating from one code to another. PMID:17243754

Garibotti, Alejandra V.; Liao, Shiping; Seeman, Nadrian C.

2008-01-01

66

A simple-structured acridine derivative as a fluorescent enhancement chemosensor for the detection of Pd2+ in aqueous media  

NASA Astrophysics Data System (ADS)

4,5-Bis(hydroxymethyl) acridine (sensor 1) has been discovered and synthesized as a simple-structured Pd2+ fluorescent probe. Sensor 1 showed highly selective recognition toward Pd2+ over other examined metal ions in aqueous solution. Under the optimized condition, fluorescence intensity was linearly proportional to the concentration of Pd2+ in the 0-1 ?M concentration range with detection limits of 0.021 ?M. The EDTA-adding and stoichiometry experiments indicated that sensor 1 was a reversible chemosensor for Pd2+ with a 2:1 ligand/metal complex at neutral pH. Moreover, the sensor 1 was also successfully applied to determination of Pd2+ in water samples and palladium-containing catalyst, which made it attractive for sensing applications.

Zhou, Yanmei; Huang, Qi; Zhang, Qingyou; Min, Yinghao; Wang, Enze

2015-02-01

67

EMCCD-based spectrally resolved fluorescence correlation spectroscopy.  

PubMed

We present an implementation of fluorescence correlation spectroscopy with spectrally resolved detection based on a combined commercial confocal laser scanning/fluorescence correlation spectroscopy microscope. We have replaced the conventional detection scheme by a prism-based spectrometer and an electron-multiplying charge-coupled device camera used to record the photons. This allows us to read out more than 80,000 full spectra per second with a signal-to-noise ratio and a quantum efficiency high enough to allow single photon counting. We can identify up to four spectrally different quantum dots in vitro and demonstrate that spectrally resolved detection can be used to characterize photophysical properties of fluorophores by measuring the spectral dependence of quantum dot fluorescence emission intermittence. Moreover, we can confirm intracellular cross-correlation results as acquired with a conventional setup and show that spectral flexibility can help to optimize the choice of the detection windows. PMID:21164726

Bestvater, Felix; Seghiri, Zahir; Kang, Moon Sik; Gröner, Nadine; Lee, Ji Young; Im, Kang-Bin; Wachsmuth, Malte

2010-11-01

68

Bis-benzimidazolyl diamide based fluorescent probe for copper(II): synthesis, structural and fluorescence studies.  

PubMed

A new fluorescent probe based on a bis-benzimidazole diamide N (2),N (2')-bis[(1-ethyl-benzimidazol-2-yl)methyl]biphenyl-2,2'-dicarboxamide ligand L 1 with a biphenyl spacer group and a Copper(II) trinuclear metallacycle has been synthesized and characterized by X-ray single crystallography, elemental and spectral (FT-IR, (1)H & (13)C NMR, UV-Visible) analysis. The fluorescence spectra of L 1 in MeOH show an emission band centered at 300 nm. This band arises due to benzimidazolyl moiety in the ligating system. The diamide L 1 in the presence of Cu(2+) show the simultaneous 'quenching' of (300 nm) and 'enhancement' of (375 nm) emission band. Similar fluorescence behavior was found in water-methanol mixture (9:1). The new emission band at 375 nm is attributed to intra ligand ?-?* transition of the biphenyl moiety. L 1 exhibited high selectivity and sensitivity towards Cu(2+) in both the medium over other common metal ions like Ni(2+), Co(2+), Mn(2+), Mg(2+), Zn(2+), Pb(2+) and Hg(2+). The binding constant with Cu(2+) was calculated by the Benesi-Hildebrand equation. Selective "off-on-off" behavior of L 1 in methanol has also been studied. The fluorescent intensity of 375 nm bands in L 1 enhances (turns-on) upon addition of Cu(2+) and quenches (turn-off) upon addition of Na2-EDTA. PMID:23494165

Mahiya, Kuldeep; Mathur, Pavan

2013-07-01

69

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

70

Quantification of DNA through a fluorescence biosensor based on click chemistry.  

PubMed

A simple, sensitive and selective fluorescence biosensor for determination of DNA using CuS particles based on click chemistry is reported. Biotin-modified capture DNA was modified on Streptavidin MagneSphere Paramagnetic Particles (PMPs) and hybridized with target DNA (hepatitis B virus DNA had been chosen as an example), then bound target DNA was hybridized with DNA-CuS particles and formed a sandwich like structure. CuS particles on the sandwich structures can be destroyed by acid to form Cu(II), and Cu(II) can be reduced to Cu(I) by sodium ascorbate, which in turn catalyzes the reaction between a weak-fluorescent 3-azido-7-hydroxycoumarin and propargyl alcohol to form a fluorescent 1,2,3-triazole compound. Using this method, target DNA concentration can be determined by a change in the fluorescence intensity of the system. It is found that the fluorescence increase factor has a direct linear relationship to the logarithm of target DNA concentrations in the range of 0.1 to 100 nM, and the detection limit is 0.04 nM (S/N = 3). The proposed sensor not only allows high sensitivity and good reproducibility, but also has a good selectivity to single-nucleotide mismatches. PMID:25259370

Yue, Guiyin; Ye, Huazhen; Huang, Xijing; Ye, Wenmei; Qiu, Suyan; Qiu, Bin; Lin, Zhenyu; Chen, Guonan

2014-11-21

71

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.

2012-03-01

72

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

73

Fluorescence-based Broad Dynamic Range Viscosity Probes.  

PubMed

We introduce two new fluorescent viscosity probes, SYBR Green (SG) and PicoGreen (PG), that we have studied over a broad range of viscosity and in collagen solutions. In water, both dyes have low quantum yields and excited state lifetimes, while in viscous solvents or in complex with DNA both parameters dramatically (300-1000-fold) increase. We show that in log-log scale the dependence of the dyes' quantum yield vs. viscosity is linear, the slope of which is sensitive to temperature. Application of SG and PG, as a fluorescence-based broad dynamic range viscosity probes, to the life sciences is discussed. PMID:24241893

Dragan, Anatoliy; Graham, August E; Geddes, Chris D

2013-11-16

74

Fluorescent blood glucose monitor by hemin-functionalized graphene quantum dots based sensing system.  

PubMed

In the present work, a highly sensitive and specific fluorescent biosensor for blood glucose monitoring is developed based on hemin-functionalized graphene quantum dots (GQDs) and glucose oxidase (GOx) system. The GQDs which are simply prepared by pyrolyzing citric acid exhibit strong fluorescence and good water-solubility. Due to the noncovalent assembly between hemin and GQDs, the addition of hemin can make hydrogen peroxide (H2O2) to destroy the passivated surface of GQDs, leading to significant fluorescence quenching of GQDs. Based on this effect, a novel fluorescent platform is proposed for the sensing of glucose. Under the optimized conditions, the linear range of glucose is from 9 to 300?M, and the limit of detection is 0.1?M. As unique properties of GQDs, the proposed biosensor is green, simple, cost-efficient, and it is successfully applied to the determination of glucose in human serum. In addition, the proposed method provides a new pathway to further design the biosensors based on the assembly of GQDs with hemin for detection of biomolecules. PMID:24439507

He, Yuezhen; Wang, Xiaoxun; Sun, Jian; Jiao, Shoufeng; Chen, Hongqi; Gao, Feng; Wang, Lun

2014-01-31

75

Simple white organic light emitting diodes with improved color stability and efficiency using phosphorescent and fluorescent emitters  

NASA Astrophysics Data System (ADS)

White organic light emitting diodes (WOLEDs) with both phosphorescent and fluorescent emitting layers (EML) usually adopt an interlayer between them to achieve high efficiency by preventing mutual quenching, but insertion of the interlayer causes a higher operating voltage as well as additional fabrication steps. Here, we demonstrate that simple-structure WOLEDs without an interlayer could be achieved using the combination of phosphor-sensitized-fluorescent red and phosphorescent blue EMLs. In addition, the main cause of the color shift with increasing current density was identified, and the color shift of the WOLED was successfully suppressed by properly balancing emission from the red and blue EMLs. Consequently, a maximum external quantum efficiency of 6.2% (a current efficiency of 14.3 cd/A) and very stable color coordinates of (0.32±0.01,0.42±0.002) were achieved. However, the elimination of an interlayer for the combination with a fluorescent blue EML causes about 50% decrease in the efficiency and a large change in the color coordinates with the driving current density.

Baek, Heume-Il; Lee, Changhee

2008-06-01

76

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

77

Fluorescent detection of ATP based on signaling DNA aptamer attached silica nanoparticles  

NASA Astrophysics Data System (ADS)

Novel methods for rapid, sensitive and low-cost biomolecule detection have attracted particular interest because of their wide use in medical diagnostics, food inspection and biomedical research applications. In this work, we report a simple and efficient silica nanoparticle (NP)-based fluorescent assay for ATP detection. It takes advantage of the washing and separation properties of NPs and the structure-switch property of DNA aptamers, resulting in fluorescence change of the supernatant in the presence of targets. A linear response for ATP detection was observed from 0 to 6 mM with a detection limit of ~34 µM. This detection strategy could be generalized to other aptamer-based detection systems.

Wang, Yanyan; Wang, Yusong; Liu, Bin

2008-10-01

78

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

79

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

80

Colorful Protein-Based Fluorescent Probes for Collagen Imaging  

PubMed Central

Real-time visualization of collagen is important in studies on tissue formation and remodeling in the research fields of developmental biology and tissue engineering. Our group has previously reported on a fluorescent probe for the specific imaging of collagen in live tissue in situ, consisting of the native collagen binding protein CNA35 labeled with fluorescent dye Oregon Green 488 (CNA35-OG488). The CNA35-OG488 probe has become widely used for collagen imaging. To allow for the use of CNA35-based probes in a broader range of applications, we here present a toolbox of six genetically-encoded collagen probes which are fusions of CNA35 to fluorescent proteins that span the visible spectrum: mTurquoise2, EGFP, mAmetrine, LSSmOrange, tdTomato and mCherry. While CNA35-OG488 requires a chemical conjugation step for labeling with the fluorescent dye, these protein-based probes can be easily produced in high yields by expression in E. coli and purified in one step using Ni2+-affinity chromatography. The probes all bind specifically to collagen, both in vitro and in porcine pericardial tissue. Some first applications of the probes are shown in multicolor imaging of engineered tissue and two-photon imaging of collagen in human skin. The fully-genetic encoding of the new probes makes them easily accessible to all scientists interested in collagen formation and remodeling. PMID:25490719

Aper, Stijn J. A.; van Spreeuwel, Ariane C. C.; van Turnhout, Mark C.; van der Linden, Ardjan J.; Pieters, Pascal A.; van der Zon, Nick L. L.; de la Rambelje, Sander L.; Bouten, Carlijn V. C.; Merkx, Maarten

2014-01-01

81

A Simple Visualization of Double Bond Properties: Chemical Reactivity and UV Fluorescence  

ERIC Educational Resources Information Center

A simple, easily visualized thin-layer chromatography (TLC) staining experiment is presented that highlights the difference in reactivity between aromatic double bonds and nonaromatic double bonds. Although the stability of aromatic systems is a major theme in organic chemistry, the concept is rarely reinforced "visually" in the undergraduate…

Grayson, Scott M.

2012-01-01

82

A chelation enhanced selective fluorescence sensing of Hg2+ by a simple quinoline substituted tripodal amide receptor.  

PubMed

Two tris(2-aminoethyl)amine (tren) based tripodal amide fluoroionophores, 1 and 2, functionalized with quinoline (chelating fluorophore) and naphthalene (non-chelating fluorophore) respectively, are synthesized in good yields. Fluoroionophore 1 shows a selective UV-Vis spectral shift in the case of Hg(2+) in acetonitrile among different metal ions like Li(+), Na(+), Ca(2+), Mg(2+), Cr(2+), Mn(2+), Fe(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), Hg(2+), Pb(2+), and Ag(+). On the other hand, fluoroionophore 2 shows no selectivity towards any of the above metal ions in the UV-Vis study. Furthermore, 1 shows a selective chelation induced fluorescence enhancement in the presence of Hg(2+) whereas 2 shows the enhancement of fluorescence with most of the metal ions via a photoinduced charge transfer mechanism. The naked eye detection of Hg(2+) in an acetonitrile solution of 1 shows a greenish fluorescence upon UV light irradiation. The isolated Hg(2+) complex of 1, 3, shows a similar UV-Vis and fluorescence spectral output as observed from in situ spectroscopic studies of 1 in the presence of Hg(2+). Infra-red (IR) and (1)H- NMR studies also reveal the interaction of Hg(2+) with the quinoline nitrogen atoms as well as with the amide functionality. PMID:21984526

Ahamed, B Nisar; Ghosh, Pradyut

2011-12-14

83

A Simple E-learning System based on Classroom Competition  

E-print Network

A Simple E-learning System based on Classroom Competition Iván Cantador, José M. Conde Departamento on online forms that allows teachers to easily organise competitions in a classroom. This system is used in a preliminary study to evaluate whether cooperative competition is positive or not in education, and to identify

Cantador, Iván

84

A Simple Inquiry-Based Lab for Teaching Osmosis  

ERIC Educational Resources Information Center

This simple inquiry-based lab was designed to teach the principle of osmosis while also providing an experience for students to use the skills and practices commonly found in science. Students first design their own experiment using very basic equipment and supplies, which generally results in mixed, but mostly poor, outcomes. Classroom "talk…

Taylor, John R.

2014-01-01

85

Contract-based discovery of Web services modulo simple orchestrators  

E-print Network

Contract-based discovery of Web services modulo simple orchestrators Luca Padovani Istituto di, or contract. The availability of repositories of Web service descriptions enables inter- esting forms of dynamic Web service discovery, such as searching for Web services exposing a specified contract

Torino, Università di

86

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

2011-03-01

87

A coumarin-indole based colorimetric and "turn on" fluorescent probe for cyanide.  

PubMed

A novel coumarin-indole based chemodosimeter with a simple structure was designed and prepared via a condensation reaction in high yield. The probe exhibited very high selectivity towards cyanide on both fluorescence and UV-vis spectra, which allowed it to quantitatively detect and imaging cyanide ions in organic-aqueous solution by either fluorescence enhancement or colorimetric changes. Confirmed by (1)H NMR and HRMS spectra, the detection mechanism was proved to be related with the Michael addition reaction induced by cyanide ions, which blocked the intramolecular charge transfer (ICT) of the probe. Moreover, the probe was able to be utilized efficiently in a wide pH range (7.5-10) with negligible interference from other anions and a low detection limit of 0.51?M. Application in 5 kinds of natural water source and accurate detection of cyanide in tap water solvent system also indicated the high practical significance of the probe. PMID:25490042

Xu, Yu; Dai, Xi; Zhao, Bao-Xiang

2015-03-01

88

A fluorescence enhancement-based sensor for hydrogen sulfate ion.  

PubMed

Sugar-aza-crown ether-based cavitand 1 can act as a selective turn-on fluorescence sensor for hydrogen sulfate ion in methanol among a series of tested anions. Spectroscopic studies, particularly NMR spectroscopy, revealed that the C-H hydrogen bonding between 1,2,3-triazole ring of cavitand 1 and hydrogen sulfate ion is crucial for the high selectivity of the receptor for hydrogen sulfate. PMID:22363932

Yang, Shih-Tse; Liao, De-Jhong; Chen, Shau-Jiun; Hu, Ching-Han; Wu, An-Tai

2012-04-01

89

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

90

Microfiberoptic Measurement of Extracellular Space Volume in Brain and Tumor Slices Based on Fluorescent Dye Partitioning  

PubMed Central

The fractional volume occupied by extracellular space in tissues, termed ?, is an important parameter of tissue architecture that affects cellular functions and drug delivery. We report a technically simple fluorescent dye partitioning method to measure ? in tissue slices based on microfiberoptic detection of dye fluorescence in tissue versus overlying solution. Microfiberoptic tip geometry and dyes were selected for ? determination from fluorescence intensity ratios, without the need to correct for illumination profile, light scattering/absorption, or dye binding. The method was validated experimentally using cell-embedded gels of specified ?-values and optical properties. In mouse brain slices, ? was strongly location-dependent, ranging from 0.16 in thalamus to 0.22 in brainstem, and was sensitive to cell volume changes. Aquaporin-4 water channel gene deletion caused significant extracellular space expansion, with ? = 0.181 ± 0.002 in cortex in wild-type mice and 0.211 ± 0.003 in Aquaporin-4 knockout mice. In slices of LLC1 cell tumors grown in mice to ?5 mm diameter, ? decreased remarkably from ?0.45 in superficial tumor to <0.25 in deeper (>100 ?m) tumor. Fluorescent dye partitioning with microfiberoptic detection permits rapid, accurate, and anisotropy-insensitive determination of ?-values in tissue slices. PMID:20713014

Zhang, Hua; Verkman, A.S.

2010-01-01

91

A simple, rapid and low-cost staining method for gel-electrophoresis separated phosphoproteins via the fluorescent purpurin dye.  

PubMed

A novel fluorescence detection method for phosphoproteins in 1-D and 2-D SDS-PAGE by using purpurin is developed in this study. Phosphoproteins as low as 4-8 ng could be specifically detected by purpurin within 60 min, and the detection limit is similar to or better than that of Pro-Q Diamond staining. Only 2 steps (staining and destaining) are needed for purpurin staining without requiring excessive fixing and washing steps, and for single use, $0.8 is enough for purpurin staining. By comprehensively comparing with Pro-Q Diamond staining, it is concluded that purpurin staining is a simple, rapid and low-cost staining method for a broad application to the research of phosphoproteins. PMID:25325196

Cong, Weitao; Shen, Jiayi; Xuan, Yuanhu; Zhu, Xinliang; Ni, Maowei; Zhu, Zhongxin; Hong, Guoying; Lu, Xianghong; Jin, Litai

2014-12-01

92

A simple and rapid fluorescence in situ hybridization microwave protocol for reliable dicentric chromosome analysis.  

PubMed

Fluorescence in situhybridization (FISH) is an extremely effective and sensitive approach to analyzing chromosome aberrations. Until recently, this procedure has taken multiple days to complete. The introduction of telomeric and centromeric peptide nucleic acid (PNA) probes has reduced the procedure's duration to several hours, but the protocols still call for a high temperature (80-90°C) step followed by 1-3 h of hybridization. The newest method to speed up the FISH protocol is the use of a microwave to shorten the heating element to less than a minute; however this protocol still calls for a 1-h hybridization period. We have utilized PNA centromere/telomere probes in conjunction with a microwave oven to show telomere and centromere staining in as little as 30 s. We have optimized the hybridization conditions to increase the sensitivity and effectiveness of the new protocol and can effectively stain chromosomes in 2 min and 30 s of incubation. We have found that our new approach to FISH produces extremely clear and distinct signals. Radiation-induced dicentric formation in mouse and human fibroblast cells was analyzed by two individual scorers and the observed dicentrics matched very well. PMID:23161278

Cartwright, Ian M; Genet, Matthew D; Kato, Takamitsu A

2013-03-01

93

A label-free, fluorescence based assay for microarray  

NASA Astrophysics Data System (ADS)

DNA chip technology has drawn tremendous attention since it emerged in the mid 90's as a method that expedites gene sequencing by over 100-fold. DNA chip, also called DNA microarray, is a combinatorial technology in which different single-stranded DNA (ssDNA) molecules of known sequences are immobilized at specific spots. The immobilized ssDNA strands are called probes. In application, the chip is exposed to a solution containing ssDNA of unknown sequence, called targets, which are labeled with fluorescent dyes. Due to specific molecular recognition among the base pairs in the DNA, the binding or hybridization occurs only when the probe and target sequences are complementary. The nucleotide sequence of the target is determined by imaging the fluorescence from the spots. The uncertainty of background in signal detection and statistical error in data analysis, primarily due to the error in the DNA amplification process and statistical distribution of the tags in the target DNA, have become the fundamental barriers in bringing the technology into application for clinical diagnostics. Furthermore, the dye and tagging process are expensive, making the cost of DNA chips inhibitive for clinical testing. These limitations and challenges make it difficult to implement DNA chip methods as a diagnostic tool in a pathology laboratory. The objective of this dissertation research is to provide an alternative approach that will address the above challenges. In this research, a label-free assay is designed and studied. Polystyrene (PS), a commonly used polymeric material, serves as the fluorescence agent. Probe ssDNA is covalently immobilized on polystyrene thin film that is supported by a reflecting substrate. When this chip is exposed to excitation light, fluorescence light intensity from PS is detected as the signal. Since the optical constants and conformations of ssDNA and dsDNA (double stranded DNA) are different, the measured fluorescence from PS changes for the same intensity of excitation light. The fluorescence contrast is used to quantify the amount of probe-target hybridization. A mathematical model that considers multiple reflections and scattering is developed to explain the mechanism of the fluorescence contrast which depends on the thickness of the PS film. Scattering is the dominant factor that contributes to the contrast. The potential of this assay to detect single nucleotide polymorphism is also tested.

Niu, Sanjun

94

Note: A portable, light-emitting diode-based ruby fluorescence spectrometer for high-pressure calibration  

NASA Astrophysics Data System (ADS)

Ruby (Al2O3, with ˜0.5 wt. % Cr doping) is one of the most widely used manometers at the giga-Pascal scale. Traditionally, its fluorescence is excited with intense laser sources. Here, I present a simple, robust, and portable design that employs light-emitting diodes (LEDs) instead. This LED-based system is safer in comparison with laser-based ones.

Feng, Yejun

2011-04-01

95

Note: A portable, light-emitting diode-based ruby fluorescence spectrometer for high-pressure calibration  

SciTech Connect

Ruby (Al{sub 2}O{sub 3}, with {approx}0.5 wt. % Cr doping) is one of the most widely used manometers at the giga-Pascal scale. Traditionally, its fluorescence is excited with intense laser sources. Here, I present a simple, robust, and portable design that employs light-emitting diodes (LEDs) instead. This LED-based system is safer in comparison with laser-based ones.

Feng Yejun [Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (United States)

2011-04-15

96

Smartphone-Based Fluorescence Detector for mHealth.  

PubMed

We describe here a compact smartphone-based fluorescence detector for mHealth. A key element to achieving high sensitivity using low sensitivity phone cameras is a capillary array, which increases sensitivity by 100×. The capillary array was combined with a white LED illumination system to enable wide spectra fluorescent excitation in the range of 450-740 nm. The detector utilizes an orthographic projection system to form parallel light projection images from the capillaries at a close distance via an object-space telecentric lens configuration that reduces the total lens-to-object distance while maintaining uniformity in measurement between capillaries. To further increase the limit of detection (LOD), a computational image processing approach was employed to decrease the level of noise. This enables an additional 5-10× decrease in LOD. This smartphone-based detector was used to measure serial dilutions of fluorescein with a LOD of 1 nM with image stacking and 10 nM without image stacking, similar to the LOD obtained with a commercial plate reader. Moreover, the capillary array required a sample volume of less than 10 ?l, which is an order of magnitude less than the 100 ?l required for the plate reader.As fluorescence detection is widely used in sensitive biomedical assays, the approach described here has the potential to increase mHealth clinical utility, especially for telemedicine and for resource-poor settings in global health applications. PMID:25626543

Balsam, Joshua; Bruck, Hugh Alan; Rasooly, Avraham

2015-01-01

97

Hybridization assay based on evanescent fluorescence excitation and collection  

NASA Astrophysics Data System (ADS)

There is a great need for high throughput and sensitive sensors for genetic analysis. These sensors can be used for varied purposes from monitoring gene expression in organims to speciation of possible pathogens. Consequently, an instrument capable of these tasks would be a great benefit for food and water safety, medical diagnostics and defense of military and civilian populations from biological threats. This work examines the development of a hybridization-based biosensor using a novel tapered fiber optic rpobe. The immobilization of single-stranded, synthetic ologinucleotides utilizing aminoproplytriethoxysilane and glutaraldehyde was implemented on the fiber optic sensor. Hybridization takes place with a complementary analyte sequence followed by a fluorescent, labeled signaling probe to form a sandwich assay. Following hybridization, the fiber is interrogated with a diode laser source and the resulting fluorescence signal is detected using a miniature spectrometer.

Sumner, James J.; Mmerole, Robert U.; Stratis-Cullum, Dimitra N.; Yi, Hyunmin; Bentley, William E.; Gillespie, James B.

2003-08-01

98

A colorimetric and fluorescent cyanide chemosensor based on dicyanovinyl derivatives: Utilization of the mechanism of intramolecular charge transfer blocking  

NASA Astrophysics Data System (ADS)

Chemosensor (CS1) was designed and synthesized by simple green chemistry procedure. CS1 exhibited both colorimetric and fluorescence turn-off responses for cyanide (CN-) ion in aqueous solution. The probe showed an immediate visible color changes from yellow to colorless and green fluorescence disappearance when CN- was added. The mechanism of chemosensor reaction with CN- was studied using 1HH NMR and 13C NMR spectroscopies and mass spectrometry. Moreover, test strips based on the sensor were fabricated, which served as convenient and efficient CN- test kits.

Li, Qiao; Cai, Yi; Yao, Hong; Lin, Qi; Zhu, Yuan-Rong; Li, Hui; Zhang, You-Ming; Wei, Tai-Bao

2015-02-01

99

A colorimetric and fluorescent cyanide chemosensor based on dicyanovinyl derivatives: utilization of the mechanism of intramolecular charge transfer blocking.  

PubMed

Chemosensor (CS1) was designed and synthesized by simple green chemistry procedure. CS1 exhibited both colorimetric and fluorescence turn-off responses for cyanide (CN(-)) ion in aqueous solution. The probe showed an immediate visible color changes from yellow to colorless and green fluorescence disappearance when CN(-) was added. The mechanism of chemosensor reaction with CN(-) was studied using (1)HH NMR and (13)C NMR spectroscopies and mass spectrometry. Moreover, test strips based on the sensor were fabricated, which served as convenient and efficient CN(-) test kits. PMID:25459631

Li, Qiao; Cai, Yi; Yao, Hong; Lin, Qi; Zhu, Yuan-Rong; Li, Hui; Zhang, You-Ming; Wei, Tai-Bao

2015-02-01

100

Seminaphthofluorescein-Based Fluorescent Probes for Imaging Nitric Oxide in Live Cells  

E-print Network

Fluorescent turn-on probes for nitric oxide based on seminaphthofluorescein scaffolds were prepared and spectroscopically characterized. The Cu(II) complexes of these fluorescent probes react with NO under anaerobic ...

Pluth, Michael D.

101

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

102

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

103

Simple and sensitive high-performance liquid chromatography-fluorescence method for the determination of citrinin application to the analysis of fungal cultures and cheese extracts  

Microsoft Academic Search

A new and highly sensitive method for the detection of the important mycotoxin, citrinin, has been developed. Spectroscopic studies demonstrate that the fluorescence of this metabolite is influenced by the pH of the environment. This fact was exploited in the chromatographic determination of citrinin with fluorescence detection. The proposed method, based on the addition of 1 M hydrochloric acid as

C. M. Franco; C. A. Fente; B. Vazquez; A. Cepeda; L. Lallaoui; P. Prognon; G. Mahuzier

1996-01-01

104

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

105

A simple, rapid, and high-throughput fluorescence polarization immunoassay for simultaneous detection of organophosphorus pesticides in vegetable and environmental water samples  

Technology Transfer Automated Retrieval System (TEKTRAN)

A simple, rapid, and high-throughput fluorescent polarization immunoassay (FPIA) for simultaneous determination of organophosphorus pesticides (OPs) was developed. Three haptens were labeled with a fluorescein probe and used as tracers to develop a homogenous FPIA using a broad-specificity monoclon...

106

The development of simple and sensitive small-molecule fluorescent probes for the detection of serum proteins after native polyacrylamide gel electrophoresis.  

PubMed

In this paper, a simple and sensitive small-molecule fluorescent probe, 2,5-dihydroxy-4'-dimethylaminochalcone (DHDMAC), was designed and synthesized for the detection of human serum proteins via hydrophobic interactions after polyacrylamide gel electrophoresis (PAGE). This probe produced lower fluorescence emission in the absence of proteins, and the emission intensity was significantly increased after the interaction with serum proteins. To demonstrate the imaging performance of this probe as a fluorescent dye, a series of experiments was conducted that included sensitivity comparison and 2D-PAGE. The results indicated that the sensitivity of DHDMAC staining is comparable to that of the most widely used fluorescent dye, SYPRO Ruby, and more protein spots (including thyroxine-binding globulin, angiotensinogen, afamin, zinc-?-2-glycoprotein and ?-1-antichymotrypsin) were detected after 2D-PAGE. Therefore, DHDMAC is a good protein reporter due to its fast staining procedure, low detection limits and high resolution. PMID:22475746

Wang, Fangfang; Huang, Lingyun; Na, Na; He, Dacheng; Sun, Dezhi; Ouyang, Jin

2012-05-21

107

Fluorescence sensors for Zn(2+) based on conjugated indole Schiff base.  

PubMed

Two novel fluorescence probes based on conjugated Schiff base for the detection of Zn(2+) were developed. Corresponding molecular geometries, orbital energies, electron contributions and absorption properties of the fluorescence probes were calculated at B3LYP/6-31G(?) by density functional theory. The fluorescence properties of the probes were investigated by UV-vis and fluorescence spectrometer. Results indicate that the probes exhibit excellent sensitivity and selectivity for Zn(2+) compared with metal ions examined. For example, the enhancement efficiency of the compound 2 for Zn(2+) is up to 846%. The detection limit of the sensor toward Zn(2+) could low to 1.0×10(-7)M. Moreover, mechanisms for the high selectivity and sensitivity of the probes to Zn(2+) were studied. PMID:25541397

Xu, Ting; Duan, Hongdong; Wang, Xingjian; Meng, Xia; Bu, Juan

2015-03-01

108

Base motif recognition and design of DNA templates for fluorescent silver clusters by machine learning.  

PubMed

Discriminative base motifs within DNA templates for fluorescent silver clusters are identified using methods that combine large experimental data sets with machine learning tools for pattern recognition. Combining the discovery of certain multibase motifs important for determining fluorescence brightness with a generative algorithm, the probability of selecting DNA templates that stabilize fluorescent silver clusters is increased by a factor of >3. PMID:25043854

Copp, Stacy M; Bogdanov, Petko; Debord, Mark; Singh, Ambuj; Gwinn, Elisabeth

2014-09-01

109

Comparison of fluorescence-based temperature sensor schemes: Theoretical analysis and experimental validation  

Microsoft Academic Search

The performance of the two most promising fluorescence-based temperature sensing techniques, namely the fluorescence intensity ratio (FIR) and fluorescence lifetime (FL) schemes, have been compared. Theoretical calibration graphs for the two methods illustrate the useful monotonic change of the response with temperature variation. Comparison of the responses and the sensitivities of the two schemes show that at very low temperatures

S. F. Collins; G. W. Baxter; S. A. Wade; T. Sun; K. T. V. Grattan; Z. Y. Zhang; A. W. Palmer

1998-01-01

110

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

111

A universal and label-free aptasensor for fluorescent detection of ATP and thrombin based on SYBR Green I dye.  

PubMed

A facile and universal aptamer-based label-free approach for selective and sensitive fluorescence detection of proteins and small biomolecules by using the SYBR Green I (SGI) dye is developed. This robust versatile biosensing strategy relies on fluorescence turn-off changes of SGI, resulting from target-induced structure switching of aptamers. Upon binding with the targets, the aptamers dissociate from the respective cDNA/aptamer duplexes, leading to the release of the dsDNA-intercalated SGI into solution and the quenching of the corresponding fluorescence intensities. Such target-induced conformational changes and release of aptamers from the DNA duplexes essentially lead to the change in the fluorescence signal of the SGI and thus constitute the mechanism of our aptamer-based label-free fluorescence biosensor for specific target analyses. Under optimized conditions, our method exhibits high sensitivity and selectivity for the quantification of ATP and thrombin with low detection limits (23.4 nM and 1.1 nM, respectively). Compared with previous reported methods for aptamer-based detection of ATP and thrombin, this label-free approach is selective, simple, convenient and cost-efficient without any chemical labeling of the probe or the target. Therefore, the present strategy could be easily applicable to biosensors that target a wide range of biomolecules. PMID:23202351

Kong, Ling; Xu, Jin; Xu, Yunying; Xiang, Yun; Yuan, Ruo; Chai, Yaqin

2013-04-15

112

Competitive Quenching Fluorescence Immunoassay for Chlorophenols Based on  

E-print Network

and Department of Entomology and UCD Cancer Center, University of California, Davis, California 95616 An improved. The detectability achieved is sufficient for occupational exposure risk assessment. Fluorescent detection methods the opportunity for miniaturization and high- throughput screening. Fluorescence immunoassays (fluoroimmu

Hammock, Bruce D.

113

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

114

Glycol Chitosan-Based Fluorescent Theranostic Nanoagents for Cancer Therapy  

PubMed Central

Theranostics is an integrated nanosystem that combines therapeutics with diagnostics in attempt to develop new personalized treatments with enhanced therapeutic efficacy and safety. As a promising therapeutic paradigm with cutting-edge technologies, theranostic agents are able to simultaneously deliver therapeutic drugs and diagnostic imaging agents and also monitor the response to therapy. Polymeric nanosystems have been intensively explored for biomedical applications to diagnose and treat various cancers. In recent years, glycol chitosan-based nanoagents have been developed as dual-purpose materials for simultaneous diagnosis and therapy. They have shown great potential in cancer therapies, such as chemotherapeutics and nucleic acid and photodynamic therapies. In this review, we summarize the recent progress and potential applications of glycol chitosan-based fluorescent theranostic nanoagents for cancer treatments and discuss their possible underlying mechanisms. PMID:25522316

Rhee, Jin-Kyu; Park, Ok Kyu; Lee, Aeju; Yang, Dae Hyeok; Park, Kyeongsoon

2014-01-01

115

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. PMID:22174395

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

2012-01-01

116

Pyrene-based fluorescent supramolecular hydrogel: scaffold for energy transfer.  

PubMed

The self-assembled gelation of an amino-acid-based low molecular weight gelator having a pyrene moiety at the N terminus and a bis-ethyleneoxy unit linked with succinic acid at the C terminus is reported. This amphiphile is capable of gelating binary mixtures (1/3 v/v) of CH3CN/water, DMSO/water, and DMF/water, and the minimum gelation concentration (MGC) varied from 0.2 to 0.3% w/v. The sodium salt of the amphiphile efficiently gelates water with an MGC of 1.5% w/v. The participation of different noncovalent interactions in supramolecular gelation by formation of fibrillar networks was investigated by spectroscopic and microscopic methods. High mechanical strength of the supramolecular gels is indicated by storage moduli on the order of 10(3) Pa. The hydrogel was utilized for energy transfer, whereby inclusion of only 0.00075% w/v of acridine orange resulted in about 50% quenching of the fluorescence intensity of the gel through fluorescence resonance energy transfer. PMID:25056417

Mukherjee, Subrata; Kar, Tanmoy; Das, Prasanta Kumar

2014-10-01

117

Fluorescence-based detection methodologies for nitric oxide using transition metal scaffolds  

E-print Network

Chapter 1. Fluorescence-Based Detection Methodologies for Nitric Oxide: A Review. Chapter 2. Cobalt Chemistry with Mixed Aminotroponimine Salicylaldimine Ligands: Synthesis, Characterization, and Nitric Oxide Reactivity. ...

Hilderbrand, Scott A. (Scott Alan), 1976-

2004-01-01

118

Polylysine crosslinked AIE dye based fluorescent organic nanoparticles for biological imaging applications.  

PubMed

Fluorescent organic nanoparticles based on aggregation induced emission dyes are fabricated through a ring-opening reaction using polylysine as the linker. The fluorescent organic nanoparticles obtained are characterized by a series of techniques including UV-vis absorption spectroscopy, fluorescence spectroscopy, Fourier Transform infrared spectroscopy, and transmission electron microscopy. A biocompatibility evaluation and the cell uptake behavior of the fluorescent organic nanoparticles are further investigated to evaluate their potential biomedical applications. It is demonstrated that these fluorescent organic nanoparticles can be obtained at room temperature in an air atmosphere without the need for catalyst or initiator. Furthermore, these crosslinked aggregation induced emission dye based fluorescent organic nanoparticles show uniform morphology, strong red fluorescence, high water dispersability, and excellent biocompatibility, making them promising candidates for various biomedical applications. PMID:24854875

Liu, Meiying; Zhang, Xiqi; Yang, Bin; Liu, Liangji; Deng, Fengjie; Zhang, Xiaoyong; Wei, Yen

2014-09-01

119

Gold Nanoparticle Based Surface Enhanced Fluorescence For Detection of Organophosphorus Agents  

PubMed Central

Organophosphorus agents (OPA) represent a serious concern to public safety as nerve agents and pesticides. Here we report the development of gold nanoparticle based surface enhanced fluorescence (NSEF) spectroscopy for rapid and sensitive screening of organophosphorus agents. Fluorescent from Eu3+ ions that are bound within the electromagnetic field of gold nanoparticles exhibit a strong enhancement. In the presence of OPA, Eu3+ ions are released from the gold nanoparticle surface and thus a very distinct fluorescence signal change was observed. We discussed the mechanism of fluorescence enhancement and the role of OPA for fluorescence intensity change in the presence of gold nanoparticles. PMID:24031096

Dasary, Samuel S. R.; Rai, Uma S.; Yu, Hongtao; Anjaneyulu, Yerramilli; Dubey, Madan

2013-01-01

120

Latest methods of fluorescence-based protein crystal identification.  

PubMed

Successful protein crystallization screening experiments are dependent upon the experimenter being able to identify positive outcomes. The introduction of fluorescence techniques has brought a powerful and versatile tool to the aid of the crystal grower. Trace fluorescent labeling, in which a fluorescent probe is covalently bound to a subpopulation (<0.5%) of the protein, enables the use of visible fluorescence. Alternatively, one can avoid covalent modification and use UV fluorescence, exploiting the intrinsic fluorescent amino acids present in most proteins. By the use of these techniques, crystals that had previously been obscured in the crystallization drop can readily be identified and distinguished from amorphous precipitate or salt crystals. Additionally, lead conditions that may not have been obvious as such under white-light illumination can be identified. In all cases review of the screening plate is considerably accelerated, as the eye can quickly note objects of increased intensity. PMID:25664782

Meyer, Arne; Betzel, Christian; Pusey, Marc

2015-02-01

121

Fluorescence-based visualization of autophagic activity predicts mouse embryo viability  

NASA Astrophysics Data System (ADS)

Embryo quality is a critical parameter in assisted reproductive technologies. Although embryo quality can be evaluated morphologically, embryo morphology does not correlate perfectly with embryo viability. To improve this, it is important to understand which molecular mechanisms are involved in embryo quality control. Autophagy is an evolutionarily conserved catabolic process in which cytoplasmic materials sequestered by autophagosomes are degraded in lysosomes. We previously demonstrated that autophagy is highly activated after fertilization and is essential for further embryonic development. Here, we developed a simple fluorescence-based method for visualizing autophagic activity in live mouse embryos. Our method is based on imaging of the fluorescence intensity of GFP-LC3, a versatile marker for autophagy, which is microinjected into the embryos. Using this method, we show that embryonic autophagic activity declines with advancing maternal age, probably due to a decline in the activity of lysosomal hydrolases. We also demonstrate that embryonic autophagic activity is associated with the developmental viability of the embryo. Our results suggest that embryonic autophagic activity can be utilized as a novel indicator of embryo quality.

Tsukamoto, Satoshi; Hara, Taichi; Yamamoto, Atsushi; Kito, Seiji; Minami, Naojiro; Kubota, Toshiro; Sato, Ken; Kokubo, Toshiaki

2014-03-01

122

Fluorescence-based visualization of autophagic activity predicts mouse embryo viability  

PubMed Central

Embryo quality is a critical parameter in assisted reproductive technologies. Although embryo quality can be evaluated morphologically, embryo morphology does not correlate perfectly with embryo viability. To improve this, it is important to understand which molecular mechanisms are involved in embryo quality control. Autophagy is an evolutionarily conserved catabolic process in which cytoplasmic materials sequestered by autophagosomes are degraded in lysosomes. We previously demonstrated that autophagy is highly activated after fertilization and is essential for further embryonic development. Here, we developed a simple fluorescence-based method for visualizing autophagic activity in live mouse embryos. Our method is based on imaging of the fluorescence intensity of GFP-LC3, a versatile marker for autophagy, which is microinjected into the embryos. Using this method, we show that embryonic autophagic activity declines with advancing maternal age, probably due to a decline in the activity of lysosomal hydrolases. We also demonstrate that embryonic autophagic activity is associated with the developmental viability of the embryo. Our results suggest that embryonic autophagic activity can be utilized as a novel indicator of embryo quality. PMID:24681842

Tsukamoto, Satoshi; Hara, Taichi; Yamamoto, Atsushi; Kito, Seiji; Minami, Naojiro; Kubota, Toshiro; Sato, Ken; Kokubo, Toshiaki

2014-01-01

123

Validation of a simple and fast method to quantify in vitro mineralization with fluorescent probes used in molecular imaging of bone  

SciTech Connect

Highlights: •We validate a simple and fast method of quantification of in vitro mineralization. •Fluorescently labeled agents can detect calcium deposits in the mineralized matrix of cell cultures. •Fluorescent signals of the probes correlated with Alizarin Red S staining. -- Abstract: Alizarin Red S staining is the standard method to indicate and quantify matrix mineralization during differentiation of osteoblast cultures. KS483 cells are multipotent mouse mesenchymal progenitor cells that can differentiate into chondrocytes, adipocytes and osteoblasts and are a well-characterized model for the study of bone formation. Matrix mineralization is the last step of differentiation of bone cells and is therefore a very important outcome measure in bone research. Fluorescently labelled calcium chelating agents, e.g. BoneTag and OsteoSense, are currently used for in vivo imaging of bone. The aim of the present study was to validate these probes for fast and simple detection and quantification of in vitro matrix mineralization by KS483 cells and thus enabling high-throughput screening experiments. KS483 cells were cultured under osteogenic conditions in the presence of compounds that either stimulate or inhibit osteoblast differentiation and thereby matrix mineralization. After 21 days of differentiation, fluorescence of stained cultures was quantified with a near-infrared imager and compared to Alizarin Red S quantification. Fluorescence of both probes closely correlated to Alizarin Red S staining in both inhibiting and stimulating conditions. In addition, both compounds displayed specificity for mineralized nodules. We therefore conclude that this method of quantification of bone mineralization using fluorescent compounds is a good alternative for the Alizarin Red S staining.

Moester, Martiene J.C. [Department of Radiology, Leiden University Medical Center (Netherlands)] [Department of Radiology, Leiden University Medical Center (Netherlands); Schoeman, Monique A.E. [Department of Orthopedic Surgery, Leiden University Medical Center (Netherlands)] [Department of Orthopedic Surgery, Leiden University Medical Center (Netherlands); Oudshoorn, Ineke B. [Department of Radiology, Leiden University Medical Center (Netherlands) [Department of Radiology, Leiden University Medical Center (Netherlands); Percuros BV, Leiden (Netherlands)] [Netherlands; Beusekom, Mara M. van [Department of Radiology, Leiden University Medical Center (Netherlands)] [Department of Radiology, Leiden University Medical Center (Netherlands); Mol, Isabel M. [Department of Radiology, Leiden University Medical Center (Netherlands) [Department of Radiology, Leiden University Medical Center (Netherlands); Percuros BV, Leiden (Netherlands)] [Netherlands; Kaijzel, Eric L.; Löwik, Clemens W.G.M. [Department of Radiology, Leiden University Medical Center (Netherlands); Rooij, Karien E. de, E-mail: k.e.de_rooij@lumc.nl [Department of Radiology, Leiden University Medical Center (Netherlands) [Department of Radiology, Leiden University Medical Center (Netherlands); Percuros BV, Leiden (Netherlands)] [Netherlands

2014-01-03

124

Quantum dot based turn-on fluorescent probes for anion sensing.  

PubMed

The design of fluorescent probes for turn-on sensing of anions has been especially significant because it can effectively enhance sensing sensitivity by decreasing the background interference. In the present work, we have systematically studied the potential applications of fluorescent quantum dots (QDs) in turn-on anion sensing. The fluorescence of QDs are firstly quenched by three different mechanisms, i.e. fluorescence resonance energy transfer, electron transfer and surface states modulated fluorescence. The fluorescence of the pre-quenched QDs can then be recovered by various anions due to the modulating effects of added anions on the interaction between QDs and QDs, the interaction between QDs and quenchers, and the surface chemistry of the quenched QDs, respectively. The results described here indicate that turn-on sensing of various anions by QDs-based systems can be achieved by rationally choosing fluorescence modulating strategies, demonstrating the versatility of QDs in the corresponding applications. PMID:22948544

Xia, Yunsheng; Wang, Jiajing; Zhang, Yuzhong; Song, Lei; Ye, Jingjing; Yang, Guang; Tan, Kanghui

2012-09-28

125

A sensitive fluorescent assay for thiamine based on metal-organic frameworks with intrinsic peroxidase-like activity.  

PubMed

Metal-organic frameworks (MOFs) with tunable structures and properties have recently been emerged as very interesting functional materials. However, the catalytic properties of MOFs as enzymatic mimics remain to be further investigated. In this work, we for the first time demonstrated the peroxidase-like activity of copper-based MOFs (HKUST-1) by employing thiamine (TH) as a peroxidase substrate. In the presence of H2O2, HKUST-1 can catalyze efficiently the conversion of non-fluorescent TH to strong fluorescent thiochrome. The catalytic activity of HKUST-1 is highly dependent on the temperature, pH and H2O2 concentrations. As a peroxidase mimic, HKUST-1 not only has the features of low cost, high stability and easy preparation, but also follows Michaelis-Menten behaviors and shows stronger affinity to TH than horseradish peroxidase (HRP). Based on the peroxidase-like activity of HKUST-1, a simple and sensitive fluorescent method for TH detection has been developed. As low as 1?M TH can be detected with a linear range from 4 to 700?M. The detection limit for TH is about 50 fold lower than that of HRP-based fluorescent assay. The proposed method was successfully applied to detect TH in tablets and urine samples and showed a satisfactory result. We believed that the present work could improve the understanding of catalytic behaviors of MOFs as enzymatic mimics and find out a wider application in bioanalysis. PMID:25542362

Tan, Hongliang; Li, Qian; Zhou, Zhengchen; Ma, Chanjiao; Song, Yonghai; Xu, Fugang; Wang, Li

2015-01-26

126

An efficient fluorescent sensing platform for biomolecules based on fenton reaction triggered molecular beacon cleavage strategy  

E-print Network

An efficient fluorescent sensing platform for biomolecules based on fenton reaction triggered: Molecular beacons Fenton reaction Glucose Choline Biosensor a b s t r a c t A universal sensing platform for fluorescence turn-on detection of biomolecules is developed based on Fenton reaction triggered molecular beacon

Tan, Weihong

127

Novel Ion Traps for Enhanced Fluorescence Collections and Single Photon Sources Based on Barium Ions  

E-print Network

Novel Ion Traps for Enhanced Fluorescence Collections and Single Photon Sources Based on Barium Ions Gang Shu A dissertation submitted in partial fulfillment of the requirements for the degree of Washington Abstract Novel Ion Traps for Enhanced Fluorescence Collections and Single Photon Sources Based

Blinov, Boris

128

Turn-on aptameric system for simple and selective detection of protein via base stacking-dependent DNA hybridization event.  

PubMed

Base stacking is employed in an entirely new type of sensing platform for the simple and robust detection of protein. Only in the presence of protein, the aptamer DNA can hybridize stably with the capture DNA to form a stem-loop structure due to the enhancement of base stacking. This leads to a strong chemiluminescence emission for simple protein detection. With the use of a platelet-derived growth factor as a model, a fM detection limit was obtained with a dynamic range that spanned 4 orders of magnitude. Upon modification, the approach presented herein was also extended to detect other types of targets including Hg(2+) ion and adenosine and also other types of labels such as fluorescence nanogold. We believe such advancements will represent a significant step toward improved diagnostics and more personalized medical treatment and environmental monitoring. PMID:21707048

Cai, Sheng; Lau, Choiwan; Lu, Jianzhong

2011-08-01

129

A fluorescence turn-on sensor for Hg2+ with a simple receptor available in sulphide-rich environments.  

PubMed

Detection of Hg(2+) in complex natural environmental conditions is extremely challenging, and no entirely successful methods currently exist. Here we report an easy-to-prepare fluorescent sensor B3 with 2-aminophenol as Hg(2+) receptor, which exhibits selective fluorescence enhancement toward Hg(2+) over other metal ions. Especially, the fluorescence enhancement was unaffected by anions and cations existing in environment and organism. Moreover, B3 can detect Hg(2+) in sulphide-rich environments without cysteine, S(2-) or EDTA altering the fluorescence intensity. Consequently, B3 is capable of distinguishing between safe and toxic levels of Hg(2+) in more complicated natural water systems with detection limit ?2 ppb. PMID:22227701

Fan, Jiangli; Peng, Xiaojun; Wang, Song; Liu, Xiaojian; Li, Honglin; Sun, Shiguo

2012-05-01

130

Enhanced fluorescence sensing of melamine based on thioglycolic acid-capped CdS quantum dots.  

PubMed

A sensitive and simple method for the determination of melamine (MA) was developed based on the fluorescence enhancement effect of MA for thioglycolic acid-capped (TGA-capped) CdS quantum dots (QDs). Under optimum conditions, a good linear relationship was obtained from 2.0 × 10(-9) to 5.0 × 10(-5)M. The detection limit was 1.0 × 10(-9)M, which was much lower than the safety limit (2.5 ppm in USA and the UK; 1 ppm for infant formula in China). The solution pH, the adding sequence of the buffer solution and MA and surface modifiers of CdS QDs greatly influenced the enhancement extent of MA for CdS QDs. The fluorescence enhancement was attributed to the surface passivation of the surface states of QDs by amine group of MA. The method was applied to detect MA in raw milk with satisfactory results. The proposed method manifested several advantages such as high sensitivity, short analysis time, low cost and ease of operation. PMID:22483928

Wang, Guang-Li; Jiao, Huan-Jun; Zhu, Xiao-Ying; Dong, Yu-Ming; Li, Zai-Jun

2012-05-15

131

Fluorescence resonance energy transfer-based near-infrared fluorescence sensor for glucose monitoring.  

PubMed

A novel near-infrared (NIR) fluorescence affinity sensor for continuous glucose monitoring was developed and characterized. The sensor operates by fluorescence resonance energy transfer between a NIR chromophore linked to concanavalin A (ConA) and an NIR fluorophore linked to free dextran. The binding of dextran with ConA in the absence of glucose results in low fluorescence due to quenching; however, the quenching is reversed by competitive displacement of dextran from ConA by glucose. In order to increase thermodynamic stability and the lifetime of the sensor, ConA was immobilized within a macroporous bead matrix. The sensor was contained within a sealed hollow dialysis fiber (o.d. 215 microm, wall thickness 20 microm), preventing the macromolecules from leaking out and enabling glucose to rapidly enter the fiber lumen. A glucose-insensitive reference fluorophore was also incorporated to allow for ratiometric measurements, resulting in a robust sensor output that is independent of positional and/or light intensity changes. The response of the fluorescence affinity sensor to glucose was tested continuously in an automated test chamber at 37 degrees C. The sensor showed good dynamic range within physiologically relevant glucose concentration range (15% change over 2.5-30 mM, no hysteresis), fast response time (2-4 min), and a remarkable long-term stability (6 months). We interpret the improved longevity of this sensor to be the result of an optimized photo exposure regime and immobilization of ConA to the matrix. Its small size, ratiometric output, and NIR fluorescence make this sensor well suited for dermal implantation and continuous transdermal monitoring. PMID:15117585

Ballerstadt, Ralph; Gowda, Ashok; McNichols, Roger

2004-04-01

132

Fluorescence-based assessment of plasma-induced hydrophilicity in microfluidic devices via Nile Red adsorption and depletion.  

PubMed

We present a simple method, called fluorescence-based assessment of plasma-induced hydrophilicity (FAPH), that enables spatial mapping of the local hydrophilicity of surfaces normally inaccessible by traditional contact angle measurement techniques. The method leverages the change in fluorescence of a dye, Nile Red, which is adsorbed on an oxygen plasma-treated surface, and its correlation with the contact angle of water. Using FAPH, we explored the effect of microchannel geometries on the penetration distance of oxygen plasma into a microchannel and found that entrance effects prevent uniform treatment. We showed that these variations have a significant impact on cell culture, and thus the design of cell-based microfluidic assays must consider this phenomenon to obtain repeatable and homogeneous results. PMID:25032783

Guckenberger, David J; Berthier, Erwin; Young, Edmond W K; Beebe, David J

2014-08-01

133

Highly sensitive detection of target molecules using a new fluorescence-based bead assay  

NASA Astrophysics Data System (ADS)

Development of immunoassays with improved sensitivity, specificity and reliability are of major interest in modern bioanalytical research. We describe the development of a new immunomagnetic fluorescence detection (IM-FD) assay based on specific antigen/antibody interactions and on accumulation of the fluorescence signal on superparamagnetic PE beads in combination with the use of extrinsic fluorescent labels. IM-FD can be easily modified by varying the order of coatings and assay conditions. Depending on the target molecule, antibodies (ABs), entire proteins, or small protein epitopes can be used as capture molecules. The presence of target molecules is detected by fluorescence microscopy using fluorescently labeled secondary or detection antibodies. Here, we demonstrate the potential of the new assay detecting the two tumor markers IGF-I and p53 antibodies in the clinically relevant concentration range. Our data show that the fluorescence-based bead assay exhibits a large dynamic range and a high sensitivity down to the subpicomolar level.

Scheffler, Silvia; Strauß, Denis; Sauer, Markus

2007-07-01

134

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

135

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

136

A Cell-Based Functional Assay Using a Green Fluorescent Protein-Based Calcium Indicator dCys-GCaMP  

PubMed Central

Abstract Measurement of the changes in intracellular Ca2+ levels is an important assay for drug discovery. In this report, we describe a novel Ca2+ indicator, dCys-GCaMP, based on the green fluorescent protein and the development of a rapid and simple cell-based functional assay using this new Ca2+ indicator. We demonstrated the sensitivity and reliability of the assay by measuring the cellular responses to the agonists, antagonists, channel blockers, and modulators of the ionotropic N-methyl-D-aspartate (NMDA) subtype of glutamate receptors. HEK293 cells coexpressing the NMDA receptor and dCys-GCaMP displayed a strong increase in fluorescence intensity when stimulated with the agonist glutamate. This increase in the fluorescence signal was agonist concentration dependent and could be blocked by NMDAR antagonists and channel blockers. The pharmacological parameters measured with the dCys-GCaMP assay are in close agreement with those derived from conventional assays with synthetic dye fluo-4 and literature values. In addition, we showed that this assay could be used on G protein-coupled receptors as well, as exemplified by studies on the ?1A adrenergic receptor. A limited scale evaluation of the assay performance in a 96-well compound screening format suggests that the dCys-GCaMP assay could be easily adapted to a high-throughput screening environment. The most important advantage of this new assay over the conventional fluo-4 and aequorin assays is the elimination of the dye-loading or substrate-loading process. PMID:25105973

Cai, Bin; Chen, Xia; Liu, Fang; Li, Jun; Gu, Lijuan; Liu, Jason R.

2014-01-01

137

Label-free fluorescent sensor for lead ion detection based on lead(II)-stabilized G-quadruplex formation.  

PubMed

A label-free fluorescent DNA sensor for the detection of lead ions (Pb(2+)) based on lead(II)-stabilized G-quadruplex formation is proposed in this article. A guanine (G)-rich oligonucleotide, T30695, was used as a recognition probe, and a DNA intercalator, SYBR Green I (SG), was used as a signal reporter. In the absence of Pb(2+), the SG intercalated with the single-stranded random-coil T30695 and emitted strong fluorescence. While in the presence of Pb(2+), the random-coil T30695 would fold into a G-quadruplex structure and the SG could barely show weak fluorescence, and the fluorescence intensity was inversely proportional to the involving amount of Pb(2+). Based on this, a selective lead ion sensor with a limit of detection of 3.79 ppb (parts per billion) and a detection range from 0 to 600 ppb was constructed. Because detection for real samples was also demonstrated to be reliable, this simple, low-cost, sensitive, and selective sensor holds good potential for Pb(2+) detection in real environmental samples. PMID:24486320

Zhan, Shenshan; Wu, Yuangen; Luo, Yanfang; Liu, Le; He, Lan; Xing, Haibo; Zhou, Pei

2014-10-01

138

Tuning a 96-well microtiter plate fluorescence-based assay to identify AGE inhibitors in crude plant extracts.  

PubMed

Advanced glycation end-products (AGEs) are involved in the pathogenesis of numerous diseases. Among them, cellular accumulation of AGEs contributes to vascular complications in diabetes. Besides using drugs to lower blood sugar, a balanced diet and the intake of herbal products potentially limiting AGE formation could be considered beneficial for patients' health. The current paper presents a simple and cheap high-throughput screening (HTS) assay based on AGE fluorescence and suitable for plant extract screening. We have already implemented an HTS assay based on vesperlysines-like fluorescing AGEs quickly (24 h) formed from BSA and ribose under physiological conditions. However, interference was noted when fluorescent compounds and/or complex mixtures were tested. To overcome these problems and apply this HTS assay to plant extracts, we developed a technique for systematic quantification of both vesperlysines (?(exc) 370 nm; ?(em) 440 nm) and pentosidine-like (?(exc) 335 nm; ?(em) 385 nm) AGEs. In a batch of medicinal and food plant extracts, hits were selected as soon as fluorescence decreased under a fixed threshold for at least one wavelength. Hits revealed during this study appeared to contain well-known and powerful anti-AGE substances, thus demonstrating the suitability of this assay for screening crude extracts (0.1 mg/mL). Finally, quercetin was found to be a more powerful reference compound than aminoguanidine in such assay. PMID:24256925

Séro, Luc; Sanguinet, Lionel; Blanchard, Patricia; Dang, Bach Tai; Morel, Sylvie; Richomme, Pascal; Séraphin, Denis; Derbré, Séverine

2013-01-01

139

A nanostructured aluminum oxide-based microfluidic device for enhancing immunoassay's fluorescence and detection sensitivity.  

PubMed

A nanostructured aluminum oxide (NAO)-based fluorescence biosensing platform with a programmable sample delivery microfluidic interface is reported. The NAO-based fluorescence sensor can tremendously enhance the fluorescence signals, typically up to 100?×?or more, over the glass substrate. The programmable sample delivery microfluidic interface, which is integrated with the NAO-based sensors, can automatically generate and deliver a series of different concentrations of the biological samples to each individual sensor. Hence it can facilitate the fluorescence-based biodetection and analysis for high throughput applications. Using Protein A and fluorophore-labeled Immunoglobulin G (IgG) as models, the binding between them on this platform have been demonstrated. It has been shown that the IgG of programmable concentrations can be delivered to individual sensor using the microfluidic interface and confirmed by the fluorescence images. Using current NAO-based fluorescence sensors without any optimization, the detectable concentration of IgG can be as low as 20 pg/mm(2) using a conventional fluorescence microscope. Due to its inexpensive fabrication process, this technology could provide a disposable technical platform for fluorescence-based sensing and analysis. PMID:24952737

Li, Xiang; Yin, Haocheng; Que, Long

2014-10-01

140

Recent progress in design of protein-based fluorescent biosensors and their cellular applications.  

PubMed

Protein-based fluorescent biosensors have emerged as key bioanalytical tools to visualize and quantify a wide range of biological substances and events in vitro, in cells, and even in vivo. On the basis of the construction method, the protein-based fluorescent biosensors can be principally classified into two classes: (1) genetically encoded fluorescent biosensors harnessing fluorescent proteins (FPs) and (2) semisynthetic biosensors comprised of protein scaffolds and synthetic fluorophores. Recent advances in protein engineering and chemical biology not only allowed the further optimization of conventional biosensors but also facilitated the creation of novel biosensors based on unique strategies. In this review, we survey the recent studies in the development and improvement of protein-based fluorescent biosensors and highlight the successful applications to live cell and in vivo imaging. Furthermore, we provide perspectives on possible future directions of the technique. PMID:25317665

Tamura, Tomonori; Hamachi, Itaru

2014-12-19

141

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

142

Enhancement of QDs' fluorescence based on porous silicon Bragg mirror  

NASA Astrophysics Data System (ADS)

We fabricated a new porous silicon photonic device which is a special multi-layer porous silicon including two different single layer porous silicon and a porous silicon Bragg mirror, and investigated the influence of porous silicon Bragg mirror's structure on the fluorescence intensity of quantum dots (QDs) which infiltrated into porous silicon device, and CdSe/ZnS QDs we used emit at 605 nm and 625 nm respectively. By immersing porous silicon samples in QDs solution, QDs were successfully infiltrated into porous silicon devices which have high reflection band at or beyond fluorescence peak. Experimental results show that the fluorescence intensity of QDs which infiltrated into the first layer of porous silicon device can be enhanced when fluorescence peak falls into the high reflection band of porous silicon device.

Liu, Chao; Jia, Zhenhong; Lv, Xiaoyi; Lv, Changwu; Shi, Fugui

2015-01-01

143

High-resolution fluorescence microscopy based on a cyclic sequential multiphoton process  

PubMed Central

We demonstrate high-resolution fluorescence microscopy based on a cyclic sequential multiphoton (CSM) process, which gives rise to fluorescence emission following a sequence of cyclic transitions between the bright and dark states of a fluorophore induced by pump and reverse light. By temporally modulating the reverse intensity, we can extract the fluorescence signal generated through the CSM process. We show that the demodulated fluorescence signal is nonlinearly proportional to the excitation intensities and it gives a higher spatial resolution than that of a confocal microscope. PMID:21258510

Isobe, Keisuke; Suda, Akira; Hashimoto, Hiroshi; Kannari, Fumihiko; Kawano, Hiroyuki; Mizuno, Hideaki; Miyawaki, Atsushi; Midorikawa, Katsumi

2010-01-01

144

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. PMID:23787669

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

2013-01-01

145

Long Fluorescence Lifetime Molecular Probes Based on Near Infrared Pyrrolopyrrole Cyanine Fluorophores for In Vivo Imaging  

E-print Network

Long Fluorescence Lifetime Molecular Probes Based on Near Infrared Pyrrolopyrrole Cyanine of organic molecules provide a new reporting strategy for molecular imaging in the near infrared (NIR of near-infrared (NIR) fluorescent molecular probes have been developed for in vivo imaging applications

Larson-Prior, Linda

146

Rubidium atomic beam clock based on lamp-pumping and fluorescence-detection scheme  

NASA Astrophysics Data System (ADS)

A compact, portable rubidium atomic beam clock based on lamp-pumping and fluorescence-detection scheme is proposed. The expected short-term frequency stability can be at least two orders of magnitude better than previous experimental results. The usages of lamp pumping, fluorescence detection and microwave slow-wave resonance structures make this design robust and compact.

Wang, Y. H.; Huang, J. Q.; Gu, Y.; Liu, S. Q.; Dong, T. Q.; Lu, Z. H.

2011-02-01

147

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

PubMed

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

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

2013-10-01

148

A new pyrazoline-based fluorescent sensor for Al3+ in aqueous solution  

NASA Astrophysics Data System (ADS)

A new pyrazoline-based fluorescent sensor was synthesized and the structure was confirmed by single crystal X-ray diffraction. The sensor responds to Al3+ with high selectivity among a series of cations in aqueous methanol. This sensor forms a 1:1 complex with Al3+ and displays fluorescent quenching.

Hu, Shengli; Song, Jingjing; Wu, Gongying; Cheng, Cuixia; Gao, Qing

2015-02-01

149

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

150

A new pyrazoline-based fluorescent sensor for Al3+ in aqueous solution.  

PubMed

A new pyrazoline-based fluorescent sensor was synthesized and the structure was confirmed by single crystal X-ray diffraction. The sensor responds to Al(3+) with high selectivity among a series of cations in aqueous methanol. This sensor forms a 1:1 complex with Al(3+) and displays fluorescent quenching. PMID:25456661

Hu, Shengli; Song, Jingjing; Wu, Gongying; Cheng, Cuixia; Gao, Qing

2015-02-01

151

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

152

A base-modified PNA-graphene oxide platform as a turn-on fluorescence sensor for the detection of human telomeric repeats.  

PubMed

Given the biological and therapeutic significance of telomeres and other G-quadruplex forming sequences in human genome, it is highly desirable to develop simple methods to study these structures, which can also be implemented in screening formats for the discovery of G-quadruplex binders. The majority of telomere detection methods developed so far are laborious and use elaborate assay and instrumental setups, and hence, are not amenable to discovery platforms. Here, we describe the development of a simple homogeneous fluorescence turn-on method, which uses a unique combination of an environment-sensitive fluorescent nucleobase analogue, the superior base pairing property of PNA, and DNA-binding and fluorescence quenching properties of graphene oxide, to detect human telomeric DNA repeats of varying lengths. Our results demonstrate that this method, which does not involve a rigorous assay setup, would provide new opportunities to study G-quadruplex structures. PMID:24981293

Sabale, Pramod M; George, Jerrin Thomas; Srivatsan, Seergazhi G

2014-09-21

153

A simple one-step method for preparation of fluorescent carbon nanospheres and the potential application in cell organelles imaging.  

PubMed

Highly fluorescent carbon nanospheres with a quantum yield of 17.6% have been prepared by a one-step method with hydrothermal treatment of spider silk. Due to the high photostability, low toxicity and well blood compatibility, these carbon nanospheres could be used as an excellent probes for cancer cell imaging. PMID:24655824

Ruan, Shaobo; Zhu, Biyue; Zhang, Huajin; Chen, Jiantao; Shen, Shun; Qian, Jun; He, Qin; Gao, Huile

2014-05-15

154

A base-modified PNA-graphene oxide platform as a turn-on fluorescence sensor for the detection of human telomeric repeats  

NASA Astrophysics Data System (ADS)

Given the biological and therapeutic significance of telomeres and other G-quadruplex forming sequences in human genome, it is highly desirable to develop simple methods to study these structures, which can also be implemented in screening formats for the discovery of G-quadruplex binders. The majority of telomere detection methods developed so far are laborious and use elaborate assay and instrumental setups, and hence, are not amenable to discovery platforms. Here, we describe the development of a simple homogeneous fluorescence turn-on method, which uses a unique combination of an environment-sensitive fluorescent nucleobase analogue, the superior base pairing property of PNA, and DNA-binding and fluorescence quenching properties of graphene oxide, to detect human telomeric DNA repeats of varying lengths. Our results demonstrate that this method, which does not involve a rigorous assay setup, would provide new opportunities to study G-quadruplex structures.Given the biological and therapeutic significance of telomeres and other G-quadruplex forming sequences in human genome, it is highly desirable to develop simple methods to study these structures, which can also be implemented in screening formats for the discovery of G-quadruplex binders. The majority of telomere detection methods developed so far are laborious and use elaborate assay and instrumental setups, and hence, are not amenable to discovery platforms. Here, we describe the development of a simple homogeneous fluorescence turn-on method, which uses a unique combination of an environment-sensitive fluorescent nucleobase analogue, the superior base pairing property of PNA, and DNA-binding and fluorescence quenching properties of graphene oxide, to detect human telomeric DNA repeats of varying lengths. Our results demonstrate that this method, which does not involve a rigorous assay setup, would provide new opportunities to study G-quadruplex structures. Electronic supplementary information (ESI) available. Figures, tables, experimental procedures and NMR spectra. See DOI: 10.1039/c4nr00878b

Sabale, Pramod M.; George, Jerrin Thomas; Srivatsan, Seergazhi G.

2014-08-01

155

A starting point for fluorescence-based single-molecule measurements in biomolecular research.  

PubMed

Single-molecule fluorescence techniques are ideally suited to provide information about the structure-function-dynamics relationship of a biomolecule as static and dynamic heterogeneity can be easily detected. However, what type of single-molecule fluorescence technique is suited for which kind of biological question and what are the obstacles on the way to a successful single-molecule microscopy experiment? In this review, we provide practical insights into fluorescence-based single-molecule experiments aiming for scientists who wish to take their experiments to the single-molecule level. We especially focus on fluorescence resonance energy transfer (FRET) experiments as these are a widely employed tool for the investigation of biomolecular mechanisms. We will guide the reader through the most critical steps that determine the success and quality of diffusion-based confocal and immobilization-based total internal reflection fluorescence microscopy. We discuss the specific chemical and photophysical requirements that make fluorescent dyes suitable for single-molecule fluorescence experiments. Most importantly, we review recently emerged photoprotection systems as well as passivation and immobilization strategies that enable the observation of fluorescently labeled molecules under biocompatible conditions. Moreover, we discuss how the optical single-molecule toolkit has been extended in recent years to capture the physiological complexity of a cell making it even more relevant for biological research. PMID:25271426

Gust, Alexander; Zander, Adrian; Gietl, Andreas; Holzmeister, Phil; Schulz, Sarah; Lalkens, Birka; Tinnefeld, Philip; Grohmann, Dina

2014-01-01

156

Evaluation of path-history-based fluorescence Monte Carlo method for photon migration in heterogeneous media.  

PubMed

The path-history-based fluorescence Monte Carlo method used for fluorescence tomography imaging reconstruction has attracted increasing attention. In this paper, we first validate the standard fluorescence Monte Carlo (sfMC) method by experimenting with a cylindrical phantom. Then, we describe a path-history-based decoupled fluorescence Monte Carlo (dfMC) method, analyze different perturbation fluorescence Monte Carlo (pfMC) methods, and compare the calculation accuracy and computational efficiency of the dfMC and pfMC methods using the sfMC method as a reference. The results show that the dfMC method is more accurate and efficient than the pfMC method in heterogeneous medium. PMID:25607163

Jiang, Xu; Deng, Yong; Luo, Zhaoyang; Wang, Kan; Lian, Lichao; Yang, Xiaoquan; Meglinski, Igor; Luo, Qingming

2014-12-29

157

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

158

A simple microcomputer-based optical theodolite for wind measurements  

Microsoft Academic Search

A simple pilot balloon theodolite was designed using an assembly of a camera mounted on a tripod and connected with a Apple II computer for fast and accurate data acquisition and analysis of wind velocities. An accuracy of 0.3 degrees for its two axes of rotation could be achieved and is comparable with that of a commercially available theodolite. This

S. L. Lau; K. K. Chow; C. H. Tan; K. S. Low

1987-01-01

159

Exciton energy transfer-based quantum dot fluorescence sensing array: "chemical noses" for discrimination of different nucleobases.  

PubMed

A novel exciton energy transfer-based fluorescence sensing array for the discrimination of different nucleobases was developed through target nucleobase-triggered self-assembly of quantum dots (QDs). Four QD nanoprobes with different ligand receptors, including mercaptoethylamine, N-acetyl-l-cysteine, 2-dimethyl-aminethanethiol, and thioglycolic acid, were created to detect and identify nucleobase targets. These QDs served as both selective recognition scaffolds and signal transduction elements for a biomolecule target. The extent of particle assembly, induced by the analyte-triggered self-assembly of QDs, led to an exciton energy transfer effect between interparticles that gave a readily detectable fluorescence quenching and distinct fluorescence response patterns. These patterns are characteristic for each nucleobase and can be quantitatively differentiated by linear discriminate analysis. Furthermore, a fingerprint-based barcode was established to conveniently discriminate the nucleobases. This pattern sensing was successfully used to identify nucleobase samples at unknown concentrations and five rare bases. In this "chemical noses" strategy, the robust characteristics of QD nanoprobes, coupled with the diversity of surface functionality that can be readily obtained using nanoparticles, provides a simple and label-free biosensing approach that shows great promise for biomedical applications. PMID:25495103

Liu, Jianbo; Li, Gui; Yang, Xiaohai; Wang, Kemin; Li, Li; Liu, Wei; Shi, Xing; Guo, Yali

2015-01-20

160

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

2012-03-01

161

Visualizing Graphene Based Sheets by Fluorescence Quenching Microscopy  

E-print Network

be made highly visible under a fluorescence microscope by quenching the emission from a dye coating, which in material discoveries at small length scales. For example, the discovery that graphene is visible under a normal optical microscope when deposited on dielectric-coated silicon wafers1,2 has enabled numerous

Huang, Jiaxing

162

Integrated microspectrometer for fluorescence based analysis in a microfluidic format.  

PubMed

We have demonstrated a monolithic integrated arrayed waveguide grating (AWG) microspectrometer microfluidic platform capable of fluorescence spectroscopic analysis. The microspectrometer in this proof of concept study has a small (1 cm × 1 cm) footprint and 8 output channels centred on different wavelengths. We show that the signals from the output channels detected on a camera chip can be used to recreate the complete fluorescence spectrum of an analyte. By making fluorescence measurements of (i) mixed quantum dot solutions, (ii) an organic fluorophore (Cy5) and (iii) the propidium iodide (PI)-DNA assay, we illustrate the unique advantages of the AWG platform for simultaneous, quantitative multiplex detection and its capability to detect small spectroscopic shifts. Although the current system is designed for fluorescence spectroscopic analysis, in principle, it can be implemented for other types of analysis, such as Raman spectroscopy. Fabricated using established semiconductor industry methods, this miniaturised platform holds great potential to create a handheld, low cost biosensor with versatile detection capability. PMID:22648688

Hu, Zhixiong; Glidle, Andrew; Ironside, Charles N; Sorel, Marc; Strain, Michael J; Cooper, Jon; Yin, Huabing

2012-08-21

163

Development of a Green Fluorescent Protein-Based Laboratory Curriculum  

ERIC Educational Resources Information Center

A laboratory curriculum has been designed for an undergraduate biochemistry course that focuses on the investigation of the green fluorescent protein (GFP). The sequence of procedures extends from analysis of the DNA sequence through PCR amplification, recombinant plasmid DNA synthesis, bacterial transformation, expression, isolation, and…

Larkin, Patrick D.; Hartberg, Yasha

2005-01-01

164

Fluorescence based spectral assessment of pork meat freshness  

Technology Transfer Automated Retrieval System (TEKTRAN)

Development of sensitive, nondestructive measurement methods for meat freshness is necessary to ensure safe distribution of meat products in the continually growing meat market. Fluorescence spectral technology has been shown to be a promising measurement method for quality and safety evaluation of ...

165

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. PMID:23537277

2013-01-01

166

c 2007 Anthony J. Halley A SIMPLE DISTRIBUTED BACKPRESSURE-BASED SCHEDULING AND  

E-print Network

c 2007 Anthony J. Halley #12;A SIMPLE DISTRIBUTED BACKPRESSURE-BASED SCHEDULING AND CONGESTION and Optimal Point . . . . . . . . . . . . . . . . . 13 3.3 Backpressure-Based Centralized Scheduling Algorithm . . . . . . . . . . . . . . . . . . . . . . . . . 20 4.3 Distributed Backpressure-Based Scheduler . . . . . . . . . . . . . . . 22 CHAPTER 5

Vaidya, Nitin

167

Metal-based turn-on fluorescent probes for nitric oxide sensing  

E-print Network

Chapter 1. Metal-Based Turn-On Fluorescent Probes for Sensing Nitric Oxide. Nitric oxide, a reactive free radical, regulates a variety of biological processes. The absence of tools to detect NO directly, rapidly, specifically ...

Lim, Mi Hee

2006-01-01

168

Mixed alkyl aryl phosphonate esters as quenched fluorescent activity-based probes for serine proteases.  

PubMed

Activity-based probes (ABPs) are powerful tools for the analysis of active enzyme species in whole proteomes, cells or animals. Quenched fluorescent ABPs (qABPs) can be applied for real time imaging, allowing the visualization of dynamic enzyme activation by fluorescent microscopy. Unfortunately, qABPs are only available for a few enzymes. We here describe the design and synthesis of qABPs for serine proteases based on a phosphonate ester scaffold. PMID:25553959

Serim, Sevnur; Baer, Philipp; Verhelst, Steven H L

2015-02-10

169

Selective recognition of Ni(2+) ion based on fluorescence enhancement chemosensor.  

PubMed

A new enhancing fluorescent chemosensor was introduced for selective and sensitive determination of nickel ions based on 2-(1-H-benzo[d]imidazol-2yl)-N-phenyl hydrazine carbothioamide (L). L has an intrinsic fluorescent emission which enhances in presence of nickel ions in CH3CN/H2O (70:30, v/v) solution. The fluorescence enhancement of L is attributed to a 1:1 complex formation between L and Ni(2+) ion which has been used for selective detection of Ni(2+) ion. At the optimum conditions, the fluorescence intensity of L at 352nm enhances linearly by the concentration of nickel ion from 1.6×10(-5) to 1.6×10(-7)M and detection limit of 7.9×10(-8)M. The new fluorescent probe exhibited high selectivity to Ni(2+) ion over the other common mono, di-and trivalent cations. PMID:25615675

Ganjali, M R; Hosseini, M; Motalebi, M; Sedaghat, M; Mizani, F; Faridbod, F; Norouzi, P

2015-04-01

170

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

NASA Astrophysics Data System (ADS)

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.

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

2012-10-01

171

A simple one-step method to prepare fluorescent carbon dots and their potential application in non-invasive glioma imaging  

NASA Astrophysics Data System (ADS)

Fluorescent carbon dots (CD) possess impressive potential in bioimaging because of their low photobleaching, absence of optical blinking and good biocompatibility. However, their relatively short excitation/emission wavelengths restrict their application in in vivo imaging. In the present study, a kind of CD was prepared by a simple heat treatment method using glycine as the only precursor. The diameter of CD was lower than 5 nm, and the highest emission wavelength was 500 nm. However, at 600 nm, there was still a relatively strong fluorescent emission, suggesting CD could be used for in vivo imaging. Additionally, several experiments demonstrated that CD possessed good serum stability and low cytotoxicity. In vitro, CD could be taken up into C6 glioma cells in a time- and concentration-dependent manner, with both endosomes and mitochondria involved. In vivo, CD could be used for non-invasive glioma imaging because of its high accumulation in the glioma site of the brain, which was demonstrated by both in vivo imaging and ex vivo tissue imaging. Furthermore, the fluorescent distribution in tissue slices also showed CD distributed in glioma with high intensity, while with a low intensity in normal brain tissue. In conclusion, CD were prepared using a simple method with relatively long excitation and emission wavelengths and could be used for non-invasive glioma imaging.Fluorescent carbon dots (CD) possess impressive potential in bioimaging because of their low photobleaching, absence of optical blinking and good biocompatibility. However, their relatively short excitation/emission wavelengths restrict their application in in vivo imaging. In the present study, a kind of CD was prepared by a simple heat treatment method using glycine as the only precursor. The diameter of CD was lower than 5 nm, and the highest emission wavelength was 500 nm. However, at 600 nm, there was still a relatively strong fluorescent emission, suggesting CD could be used for in vivo imaging. Additionally, several experiments demonstrated that CD possessed good serum stability and low cytotoxicity. In vitro, CD could be taken up into C6 glioma cells in a time- and concentration-dependent manner, with both endosomes and mitochondria involved. In vivo, CD could be used for non-invasive glioma imaging because of its high accumulation in the glioma site of the brain, which was demonstrated by both in vivo imaging and ex vivo tissue imaging. Furthermore, the fluorescent distribution in tissue slices also showed CD distributed in glioma with high intensity, while with a low intensity in normal brain tissue. In conclusion, CD were prepared using a simple method with relatively long excitation and emission wavelengths and could be used for non-invasive glioma imaging. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr02657h

Ruan, Shaobo; Qian, Jun; Shen, Shun; Zhu, Jianhua; Jiang, Xinguo; He, Qin; Gao, Huile

2014-08-01

172

An alternative fluorescence enhancement solution for use in lanthanide-based time-resolved fluoroimmunoassays.  

PubMed

Time-resolved fluoroimmunoassays that make use of lanthanide chelates as labels require the addition of an enhancement solution to elicit the formation of a fluorescent lanthanide complex. All solutions previously described are based on 2-naphthoyltrifluoroacetone (NTA), a beta-diketone. Currently, this compound is not commercially available. We report here the properties and performance of an enhancement solution prepared with a commercially available beta-diketone, thenoyltrifluoroacetone. Use of this solution in a commercial time-resolved fluoroimmunoassay gave results essentially identical to those obtained with the NTA-based solution, although fluorescence emission was approximately 27% lower. The lower fluorescence yield did not, however, significantly reduce assay sensitivity. We conclude that this solution represents a viable and highly economical alternative to the preparation currently in use, particularly for laboratories wishing to develop their own assays based on lanthanide fluorescence. PMID:3690848

Keelan, J A; France, J T; Barling, P M

1987-12-01

173

Colorimetric fluorescent cyanide chemodosimeter based on triphenylimidazole derivative.  

PubMed

In this paper, we demonstrated a highly selective colorimetric chemodosimeter for cyanide anion detection. This chemodosimeter having a triphenylimidazole group as a fluorescent signal unit and a dicyano-vinyl group as a reaction unit was synthesized by the Knoevenagel condensation of 4-(4,5-diphenyl-1H-imidazol-2-yl)benzaldehyde with malononitrile in a reasonable yield. The probe exhibited an intramolecular charge transfer (ICT) absorption band at 420 nm and emission band at 620 nm, respectively. Upon the addition of cyanide anion, the probe displayed a blue-shifted spectrum and loss in color due to the disruption of conjugation. With the aid of the fluorescence spectrometer, the chemodosimeter exhibited a detection limit of 0.11 ?M (S/N=3). Interferences from other common anions associated with cyanide anion analysis were effectively inhibited. PMID:24463246

Zheng, Wei; He, Xiangzhu; Chen, Hongbiao; Gao, Yong; Li, Huaming

2014-04-24

174

[Synthesis and theoretical study on fluorescence property of 4- (2-hydroxybenzylideneamino) phenyl ethanone schiff base].  

PubMed

Using salicylaldehyde and 4-aminophenyl ethanone as raw material, a Schiff base derivative 4-(2-hydroxybenzylidene-amino) phenyl ethanone was synthesized by the solid phase reaction method at room temperature. The structure of the product was characterized by elemental analysis and 1 HNMR The UV spectra, fluorescence emission spectra and fluorescence quantum yield of the title Schiff base derivative were investigated. The results showed that this Schiff base displayed superior fluorescence property. The ground state configuration of the title Schiff base was optimized by density functional theory (DFT) method at the B3LYP/6-311G level. After vibrational analysis, there is no imaginary frequency, which indicates that the structure is stable. Then the ground state configuration was optimized to the excited state configuration by the method of single excited interactions CIS. Based on the optimized structure for the ground state and excited state time-dependent density functional theory (TD-DFT) calculations were carried out at the B3LYP/6-31G level to predict the absorption spectra and the fluorescence spectra. The results show that the computed spectra were comparable with the spectra from the experiments. The relationship between the molecular structure and the fluorescence property of 4-(2-hydroxybenzylideneamino) phenyl ethanone was also discussed. The results obtained may provide some theoretical guidance for the design of new fluorescence compounds. PMID:24611382

Liang, Xiao-Rui; Wang, Gang; Jiang, Yan-Lan; Qu, Cheng-Li; Wang, Xiu-Juan; Zhao, Bo

2013-12-01

175

Fabrication, optimization and application of a dip-probe fluorescence spectrometer based on white-light excitation fluorescence  

NASA Astrophysics Data System (ADS)

A dip-probe adapter was designed for easy analysis of complex multifluorophoric systems. The newly fabricated fiber optic compatible spectrometer design with dip-probe adapter could reach and analyze fluorophores kept at a distance from the analyzer. The new design and its parameters were optimized using standard fluorophores to get an optimal spectral response. This white-light excitation fluorescence (WLEF) based spectrometer could analyze any fluorophoric system rapidly without changing the instrument configuration. Fuel-oil blends such as petrol-2T oil and petrol-4T oil were precisely quantified with high accuracy (0.3% error) using a WLEF-multivariate analysis combination.

Prakash, John; Mishra, A. K.

2013-10-01

176

Label free selective detection of estriol using graphene oxide-based fluorescence sensor  

NASA Astrophysics Data System (ADS)

Water-soluble and fluorescent Graphene oxide (GO) is biocompatible, easy, and economical to synthesize. Interestingly, GO is also capable of quenching fluorescence. On the basis of its fluorescence and quenching abilities, GO has been reported to serve as an energy acceptor in a fluorescence resonance energy transfer (FRET) sensor. GO-based FRET biosensors have been widely reported for sensing of proteins, nucleic acid, ATP (Adenosine triphosphate), etc. GO complexes with fluorescent dyes and enzymes have been used to sense metal ions. Graphene derivatives have been used for sensing endocrine-disrupting chemicals like bisphenols and chlorophenols with high sensitivity and good reproducibility. On this basis, a novel GO based fluorescent sensor has been successfully designed to detect estriol with remarkable selectivity and sensitivity. Estriol is one of the three estrogens in women and is considered to be medically important. Estriol content of maternal urine or plasma acts as an important screening marker for estimating foetal growth and development. In addition, estriol is also used as diagnostic marker for diseases like breast cancer, osteoporosis, neurodegenerative and cardiovascular diseases, insulin resistance, lupus erythematosus, endometriosis, etc. In this present study, we report for the first time a rapid, sensitive with detection limit of 1.3 nM, selective and highly biocompatible method for label free detection of estriol under physiological conditions using fluorescence assay.

Kushwaha, H. S.; Sao, Reshma; Vaish, Rahul

2014-07-01

177

Prospects for fluorescence based imaging/visualization of hydrodynamic systems on the National Ignition Facility  

SciTech Connect

The next generation of large, high power lasers, such as the National Ignition Facility (NIF) [1] in the United States, Laser Mega Joule [2] in France or Helen Successor [3] in the United Kingdom offer the prospect of x-ray fluorescence based diagnosis of hydrodynamic experiments The x-ray fluorescence could be pumped by at least two techniques One technique is to use a sizable fraction of these facilities` high power to efficiently make multi-kilovolt x-rays which, in turn, causes dopants placed in experimental packages to fluoresce We call this ``externally pumped x-ray fluorescence`` The second technique is to use the sizable multi-kilovolt photon background that we expect to be present in many hohlraum based experiments, while the driving laser is on, to pump x-ray fluorescence The fluorescing medium could be a dopant in an experimental package or, possibly, a relatively thick slab of material in the hohlraum wall which could serve as a backlighter We call this ``hohlraum hot-corona pumped fluorescence``.

Suter, L. J., LLNL

1998-06-04

178

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

2014-01-01

179

Selective detection of heavy metal ions by calixarene-based fluorescent molecular sensors  

NASA Astrophysics Data System (ADS)

The synthesis, spectroscopic characterization and complexing properties of calixarene-based fluorescent sensors are reported. The calixarene bearing four dansyl fluorophores (Calix-DANS4) exhibits a very high affinity for the detection of lead. A fluorimetric micro-device based on the use of a Y-shape microchannel was developed and allows lead detection with a 5 ppb detection limit. For mercury detection, a fluorescent molecular sensor containing a calixarene anchored with four 8-quinolinoloxy groups (Calix-Q) has been synthesized. The absorption and fluorescence spectra of this sensor are sensitive to the presence of metal cations. An efficient fluorescence quenching is observed upon mercury complexation because of a photoinduced electron transfer from the fluorophore to the bound mercury. Calix-Q shows a high selectivity towards Hg2+ over interfering cations (Na+, K+, Ca2+, Cu2+, Zn2+, Cd2+ and Pb2+) and a 70 ppb sensitivity.

Zhang, Haitao; Faye, Djibril; Zhang, Han; Lefevre, Jean-Pierre; Delaire, J. A.; Leray, Isabelle

2012-06-01

180

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

181

Live spheroid formation recorded with light sheet-based fluorescence microscopy.  

PubMed

We provide a detailed protocol for a three-dimensional long-term live imaging of cellular spheroids with light sheet-based fluorescence microscopy. The protocol allows the recording of all phases of spheroid formation in three dimensions, including cell proliferation, aggregation, and compaction. We employ the human hepatic cell line HepaRG transfected with the fusion protein H2B-GFP, i.e., a fluorescing histone. The protocol allows monitoring the effect of drugs or toxicants. PMID:25391793

Pampaloni, Francesco; Richa, Roli; Ansari, Nariman; Stelzer, Ernst H K

2015-01-01

182

An unnatural amino acid based fluorescent probe for phenylalanine ammonia lyase.  

PubMed

A fluorescent probe (2a-LP) based on an unnatural amino acid (UAA) is developed for the detection of phenylalanine ammonia lyase (PAL). In the presence of PAL, 2a-LP is catalytically deaminated to ortho-amino-transcinnamic acid (o-a-CA), which shows a remarkable “off–on” fluorescence signal. Thus, the probe 2a-LP enables direct visualization of the PAL activity in tomato under UV illumination and has potential in vitro assays. PMID:24971756

Tian, Zhenlin; Zhu, Weiping; Xu, Yufang; Qian, Xuhong

2014-08-21

183

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

184

Study of indicators for the development of fluorescence based optical fiber temperature sensors  

Microsoft Academic Search

An experimental study about fluorophores, which have never been used before in thermometric applications has been carried out for the development of fluorescence based temperature sensors. Fluorescent dyes like: 10-(3-sulfopropyl) acridinium betaine, quinacrine dihydrochloride, naphthofluorescein, fluorescein and 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt have been immobilized on sol–gel derived coatings deposited on optical fibers by dip coating. Comparison between the characteristics of

Francisco J. García Moreda; Francisco J. Arregui; Miguel Achaerandio; Ignacio R. Matias

2006-01-01

185

Fluorescence based cell counting in collagen monolayer cultures of primary hepatocytes.  

PubMed

Accurate determination of cell number is essential for the quantitative description of biological processes. The changes should be related to a measurable reference e.g. in the case of cell culture, the viable cell number is a very valuable reference parameter. Indirect methods of cell number/viability measurements may have up to 10 % standard deviation. This can lead to undesirable large deviations in the analysis of "-omics" data as well as time course studies. Such data should be preferably normalized to the exact viable cell number at a given time to allow meaningful interpretation and understanding of the biological processes. Manual counting of cell number is very laborious and not possible in certain experimental setups. We therefore, developed a simple and reliable fluorescence based method with an accuracy of 95-98 % for the determination of the viable cell number in situ. We optimized the seeding cell densities for primary rat hepatocytes for optimal cell adhesion. This will help in efficient use of primary cells which are usually limited in availability. The method will be very useful in the application of "-omics" techniques, especially metabolome analysis where the specific rates of uptake/production of metabolites can be reliably calculated. PMID:25424145

Priesnitz, C; Sperber, S; Garg, R; Orsini, M; Noor, F

2014-11-26

186

Sensitive detection of biothiols and histidine based on the recovered fluorescence of the carbon quantum dots-Hg(II) system.  

PubMed

In this paper, we presented a novel, rapid and highly sensitive sensor for glutathione (GSH), cysteine (Cys) and histidine (His) based on the recovered fluorescence of the carbon quantum dots (CQDs)-Hg(II) system. The CQDs were synthesized by microwave-assisted approach in one pot according to our previous report. The fluorescence of CQDs could be quenched in the presence of Hg(II) due to the coordination occurring between Hg(II) and functional groups on the surface of CQDs. Subsequently, the fluorescence of the CQDs-Hg(II) system was recovered gradually with the addition of GSH, Cys or His due to their stronger affinity with Hg(II). A good linear relationship was obtained from 0.10 to 20?molL(-1) for GSH, from 0.20 to 45?molL(-1) for Cys and from 0.50 to 60?molL(-1) for His, respectively. This method has been successfully applied to the trace detection of GSH, Cys or His in human serum samples with satisfactory results. The proposed method was simple in design and fast in operation, which demonstrated great potential in bio-sensing fields. PMID:25622608

Hou, Juan; Zhang, Fengshuang; Yan, Xu; Wang, Long; Yan, Jin; Ding, Hong; Ding, Lan

2015-02-15

187

Diketopyrrolopyrrole: brilliant red pigment dye-based fluorescent probes and their applications.  

PubMed

The development of fluorescent probes for the detection of biologically relevant species is a burgeoning topic in the field of supramolecular chemistry. A number of available dyes such as rhodamine, coumarin, fluorescein, and cyanine have been employed in the design and synthesis of new fluorescent probes. However, diketopyrrolopyrrole (DPP) and its derivatives have a distinguished role in supramolecular chemistry for the design of fluorescent dyes. DPP dyes offer distinctive advantages relative to other organic dyes, including high fluorescence quantum yields and good light and thermal stability. Significant advancements have been made in the development of new fluorescent probes based on DPP in recent years as a result of tireless research efforts by the chemistry scientific community. In this tutorial review, we highlight the recent progress in the development of DPP-based fluorescent probes for the period spanning 2009 to the present time and the applications of these probes to recognition of biologically relevant species including anions, cations, reactive oxygen species, thiols, gases and other miscellaneous applications. This review is targeted toward providing the readers with deeper understanding for the future design of DPP-based fluorogenic probes for chemical and biological applications. PMID:25186723

Kaur, Matinder; Choi, Dong Hoon

2015-01-01

188

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

189

Comparison of fluorescence-based semi-automated genotyping of multiple microsatellite loci with autoradiographic techniques  

SciTech Connect

The practical application of highly efficient fluorescence-based methods for the semi-automated genotyping of polymerase chain reaction-based microsatellite markers will depend on the development of robust protocols that provide accurate and reproducible data. In the present report the authors compare the accuracy of a fluorescence-based protocol with a benchmark radiolabeling method that depends on a known sequence ladder or amplified DNA from reference individuals for sizing by autoradiography. Three microsatellite markers, IGF (mfd1), D4S174 (mfd 59), and D5S211 (mfd 154), with products overlapping in size were each labeled with a different fluorophore and run simultaneously with an internal size standard in a single electrophoretic lane. The size of each allele was compared for these markers by using both techniques for five larger CEPH families (884, 1331, 1333, and 1362). Of 462 possible alleles, four discrepancies (0.8%) were identified when the two approaches were compared. The authors conclude that the fluorescence-based protocol is at least as accurate as the standard radiolabeling technique since none of the sizing errors arose as a result of the fluorescence-based technique. They describe the adaptation of the fluorescence-based protocol to the simultaneous analysis of up to 24 microsatellite loci per electrophoretic lane. These highly accurate and efficient semi-automated techniques will be useful in high-resolution genomic analyses. 18 refs., 4 tabs., 3 figs.

Schwengel, D.A.; Jedlicka, A.E.; Levitt, R.C. [Johns Hopkins Medical Institutions, Baltimore, MD (United States)] [and others] [Johns Hopkins Medical Institutions, Baltimore, MD (United States); and others

1994-07-01

190

Quantum dots-based ratiometric fluorescence probe for mercuric ions in biological fluids.  

PubMed

Fluorescence analysis by means of a single fluorescence signal output usually leads to the signal fluctuation caused by various external factors. Ratiometric fluorescence probes that can significantly eliminate the external effects by self-calibration of two different emission bands are preferable for the detection of real samples. In this work, we designed a dual-emission quantum dots (QDs) nanocomposite as a ratiometric probe for the visual detection of Hg(2+). The dual-emission QDs nanocomposite consists of two differently sized CdTe/CdS QDs. The red-emitting larger sized CdTe/CdS QDs embeded in silica nanoparticles are insensitive to Hg(2+), while the green-emitting smaller sized ones are covalently conjugated onto the silica nanoparticles surface and sensitive to Hg(2+). The addition of Hg(2+) can only quench green fluorescence in the dual-emission QDs nanocomposites, which triggers the change of fluorescence intensity ratio of two different emission wavelengths and hence induces the evolution of fluorescence color of the probe solution with variation of Hg(2+) concentration. Based on this feature, the dual-emission QDs nanocomposites can be used to develop a ratiometric fluorescence probe for the visual detection of Hg(2+). Under the optimized conditions, the ratiometric fluorescence QDs probe shows a linear relationship between fluorescence intensity ratio and Hg(2+) concentration in the range of 5-300 nM. The detection limit of this probe was found to be 3.1 nM. This ratiometric assay also exhibits a high selectivity and it has been successfully used in the determination of Hg(2+) content in fetal bovine serum and human urine. PMID:24401456

Mu, Qin; Li, Yan; Xu, Hu; Ma, Yunfei; Zhu, Weihong; Zhong, Xinhua

2014-02-01

191

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

PubMed Central

This article presents the first evidence that the DNA base analogue 1,3-diaza-2-oxophenoxazine, tCO, is highly fluorescent, both as free nucleoside and incorporated in an arbitrary DNA structure. tCO 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 (? = 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, tCO shows only minor variations in fluorescence intensity and lifetime with neighbouring bases, and the average quantum yield is 0.22. These features make tCO, 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 tCO 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

192

Simple and sensitive multi-sugar-probe gut permeability test by high-performance liquid chromatography with fluorescence labelling.  

PubMed

Enteral intake of a mixture of inert, non-metabolic monosaccharide and disaccharide probes, followed by measurement of their urinary probe ratio, is a well known method to investigate gut permeability. However, most applications lack sensitivity, thus a large amount of especially the disaccharide lactulose has to be ingested. This may cause diarrhoea, which influences the outcome of the test. Recently, a new fluorescent label 9-fluorenylethyl chloroformate hydrazine (FMOC-hydrazine) was introduced, which reacts with reducing sugars to form stable and highly fluorescent single peak derivatives in organic medium. We applied this reagent to develop a sensitive measurement of reducing sugar probes in aqueous samples (e.g., urine). The presented method has a linear response for each sugar derivative between 1 and 1250 pmol with an R2 ranging from 0.9997 for lactulose to 0.9999 for rhamnose. The limit of detection, calculated as a signal-to-noise ratio of three, was 0.05 pmol for lactulose and 0.01 pmol for rhamnose, xylose and 3-O-methyl-D-glucose, corresponding to urine concentrations of 0.11 micromol/l for lactulose and 0.02 micromol/l for rhamnose, xylose and 3-O-methyl-D-glucose. Compared to other tests, the limit of detection is very low. This enabled a reduction in the enteral intake of the disaccharide lactulose from 6-10 g to 1.5 g, thereby minimizing the chance of introducing diarrhoea. The coefficient of variation was below 3% both in standards and urine samples. After spiking the urine with the saccharides a recovery of 102% for lactulose, 101% for rhamnose, xylose and 3-O-methyl-D-glucose was found. In order to evaluate the presented method we compared the lactulose rhamnose ratio measured in urine of healthy human volunteers and kept the ingested dose in agreement with literature values. Furthermore, the ratio was measured after 3, 6 and 9 h to establish the minimal response time required to measure correct ratios. We found that even after 3 h the ratio was stable at a value of 0.0133 which is comparable to literature values (0.008-0.052). PMID:8680601

Rooyakkers, D R; van Eijk, H M; Deutz, N E

1996-04-12

193

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

194

Bioimaging of nitric oxide with fluorescent indicators based on the rhodamine chromophore.  

PubMed

Diaminofluoresceins are widely used for detection and imaging of nitric oxide (NO), but for biological applications, they have the disadvantages that the fluorescence of the fluorescein chromophore is pH-sensitive and overlaps the autofluorescence of cells. We have developed a membrane-permeable fluorescent indicator for NO based on the rhodamine chromophore, DAR-4M AM, which can be excited with 550-nm light. The fluorescence quantum yield of the product after reaction with NO is 840 times higher than that of DAR-4M. The detection limit of NO was 7 nM, and the fluorescence showed no pH dependency above pH 4. DAR-4M AM was successfully applied to practical bioimaging of NO produced in bovine aortic endothelial cells. PMID:11354477

Kojima, H; Hirotani, M; Nakatsubo, N; Kikuchi, K; Urano, Y; Higuchi, T; Hirata, Y; Nagano, T

2001-05-01

195

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

PubMed

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. PMID:23380148

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

2013-04-01

196

Assessment of dental demineralization of yellow race based on fluorescence spectrum  

NASA Astrophysics Data System (ADS)

The goal of this study was to evaluate the demineralization status at different acid-etch time based on fluorescence spectrum. Human molars in vitro of yellow race were cut into tooth sections and then they were immersed in 0.3% citric acid to simulate the oral natural demineralization. According to the acid-etch time, samples were randomly divided into three groups: I:20 min, II:40 min, and III:60 min. The normal untreated specimen was set as control group. The fluorescence spectra before and after treatment were measured and analyzed. The result showed that fluorescence spectrum could be efficiently used to monitor the demineralization status of human dental tissue. The relative fluorescence intensities of dental tissue excited respectively with 260, 330 and 400 nm decreased with the increase of acid-etch time, though there was no new constituent formed after demineralization.

Zhan, Zhenlin; Chen, Chuanguo; Li, Xuwei; Zhang, Xianzeng; Xie, Shusen

2014-11-01

197

Static Hyperspectral Fluorescence Imaging of Viscous Materials Based on a Linear Variable Filter Spectrometer  

PubMed Central

This paper presents a low-cost hyperspectral measurement setup in a new application based on fluorescence detection in the visible (Vis) wavelength range. The aim of the setup is to take hyperspectral fluorescence images of viscous materials. Based on these images, fluorescent and non-fluorescent impurities in the viscous materials can be detected. For the illumination of the measurement object, a narrow-band high-power light-emitting diode (LED) with a center wavelength of 370 nm was used. The low-cost acquisition unit for the imaging consists of a linear variable filter (LVF) and a complementary metal oxide semiconductor (CMOS) 2D sensor array. The translucent wavelength range of the LVF is from 400 nm to 700 nm. For the confirmation of the concept, static measurements of fluorescent viscous materials with a non-fluorescent impurity have been performed and analyzed. With the presented setup, measurement surfaces in the micrometer range can be provided. The measureable minimum particle size of the impurities is in the nanometer range. The recording rate for the measurements depends on the exposure time of the used CMOS 2D sensor array and has been found to be in the microsecond range. PMID:24064604

Murr, Patrik J.; Schardt, Michael; Koch, Alexander W.

2013-01-01

198

Fluorescence detection in capillary arrays based on galvanometer step scanning.  

PubMed

A computer-controlled galvanometer scanner is adapted for scanning a focused laser beam across a 96-capillary array for laser-induced fluorescence detection. The signal at a single photomultiplier tube is temporally sorted to distinguish among the capillaries. The limit of detection for fluoresceins is 3 x 10(-11) M (S/N = 3) for 5 mW of total laser power scanned at 4 Hz. The observed cross-talk among capillaries is 0.2%. Advantages include the efficient utilization of light due to the high duty-cycle of step scan, good detection performance due to the reduction of stray light, ruggedness due to the small mass of the galvanometer mirror, low cost due to the simplicity of components, and flexibility due to the independent paths for excitation and emission. PMID:11669531

Xue, G; Yeung, E S

2001-10-01

199

Fluorescent-based chemical sensor for organophosphate detection  

NASA Astrophysics Data System (ADS)

We present a new optical sensor for the detection of organophosphates by incorporating fluorescent indicator dye into sol-gel material. We used different configurations of immobilization matrices such as thin film and spherical nanoparticles. The sensor thin films were prepared by using acid-catalyzed sol-gel process and the spherical nanoparticles by modified Stöber method. The effects of configuration matrices on the sensor's characteristic were studied. The use of dye-doped nanoparticles improved the detection limit from 0.69 ?M to 17 nM, response time from 600 s to 12 s, precision and sensitivity, but reduced the sensor's working rage from 6.9×10-7 M - 6.9×10-3 M to 1.75×10-8M - 2.3×10-7 M.

Urek, Špela Korent; Lobnik, Aleksandra

2011-05-01

200

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

201

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

202

A simple map-based localization strategy using range measurements  

NASA Astrophysics Data System (ADS)

In this paper we present a map-based approach to localization. We consider indoor navigation in known environments based on the idea of a "vector cloud" by observing that any point in a building has an associated vector defining its distance to the key structural components (e.g., walls, ceilings, etc.) of the building in any direction. Given a building blueprint we can derive the "ideal" vector cloud at any point in space. Then, given measurements from sensors on the robot we can compare the measured vector cloud to the possible vector clouds cataloged from the blueprint, thus determining location. We present algorithms for implementing this approach to localization, using the Hamming norm, the 1-norm, and the 2-norm. The effectiveness of the approach is verified by experiments on a 2-D testbed using a mobile robot with a 360° laser range-finder and through simulation analysis of robustness.

Moore, Kevin L.; Kutiyanawala, Aliasgar; Chandrasekharan, Madhumita

2005-05-01

203

Satin: Simple and Efficient Java-based Grid Programming  

Microsoft Academic Search

Grid programming environments need to be both portable and efficient to exploit the computational power of dynamically available resources. In previous work, we have presented the divide-and-conquer based Satin model for parallel computing on clustered wide-area systems. In this paper, we present the Satin implementation on top of our new Ibis platform which combines Java's write once, run everywhere with

Rob van Nieuwpoort; Jason Maassen; Thilo Kielmann; Henri E. Bal

2003-01-01

204

Understanding Wax Printing: A Simple Micropatterning Process for Paper-Based  

E-print Network

Understanding Wax Printing: A Simple Micropatterning Process for Paper-Based Microfluidics Emanuel a detailed study on wax printing, a simple and inexpensive method for fabricating microfluidic devices in paper using a commercially avail- able printer and hot plate. The printer prints patterns of solid wax

Prentiss, Mara

205

An automatic correction of Ma's thinning algorithm based on P-simple points  

E-print Network

An automatic correction of Ma's thinning algorithm based on P-simple points Christophe LOHOU-simple points has been introduced by Bertrand to conceive parallel thinning algorithms. In 'A 3D fully parallel thinning algorithm for generating medial faces', Ma has proposed an algorithm for which there exists

Paris-Sud XI, Université de

206

Cyanine-based probe\\tag-peptide pair for 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 (Richland, WA); Cao, Haishi (Richland, WA)

2010-08-17

207

High-throughput retrotransposon-based fluorescent markers: improved information content and allele discrimination  

PubMed Central

Background Dense genetic maps, together with the efficiency and accuracy of their construction, are integral to genetic studies and marker assisted selection for plant breeding. High-throughput multiplex markers that are robust and reproducible can contribute to both efficiency and accuracy. Multiplex markers are often dominant and so have low information content, this coupled with the pressure to find alternatives to radio-labelling, has led us to adapt the SSAP (sequence specific amplified polymorphism) marker method from a 33P labelling procedure to fluorescently tagged markers analysed from an automated ABI 3730 xl platform. This method is illustrated for multiplexed SSAP markers based on retrotransposon insertions of pea and is applicable for the rapid and efficient generation of markers from genomes where repetitive element sequence information is available for primer design. We cross-reference SSAP markers previously generated using the 33P manual PAGE system to fluorescent peaks, and use these high-throughput fluorescent SSAP markers for further genetic studies in Pisum. Results The optimal conditions for the fluorescent-labelling method used a triplex set of primers in the PCR. These included a fluorescently labelled specific primer together with its unlabelled counterpart, plus an adapter-based primer with two bases of selection on the 3' end. The introduction of the unlabelled specific primer helped to optimise the fluorescent signal across the range of fragment sizes expected, and eliminated the need for extensive dilutions of PCR amplicons. The software (GeneMarker Version 1.6) used for the high-throughput data analysis provided an assessment of amplicon size in nucleotides, peak areas and fluorescence intensity in a table format, so providing additional information content for each marker. The method has been tested in a small-scale study with 12 pea accessions resulting in 467 polymorphic fluorescent SSAP markers of which 260 were identified as having been mapped previously using the radio-labelling technique. Heterozygous individuals from pea cultivar crosses were identifiable after peak area data analysis using the fluorescent SSAP method. Conclusion As well as developing a rapid, and high-throughput marker method for genetic studies, the fluorescent SSAP system improved the accuracy of amplicon scoring, increased the available marker number, improved allele discrimination, and was sensitive enough to identify heterozygous loci in F1 and F2 progeny, indicating the potential to develop high-throughput codominant SSAPs. PMID:19638216

Knox, Maggie; Moreau, Carol; Lipscombe, James; Baker, David; Ellis, Noel

2009-01-01

208

Highly sensitive real-time assay of inorganic pyrophosphatase activity based on the fluorescent gold nanoclusters.  

PubMed

On the basis of the competition assay approach and fluorescent 11-mercaptoundecanoic acid-capped AuNCs (AuNCs@11-MUA) with unique optical properties, a convenient, reliable and highly sensitive real-time assay of pyrophosphatase (PPase) activity is established and developed for the first time. Pyrophosphate (PPi) could recover the Cu(2+)-quenched AuNCs@11-MUA fluorescence selectively owing to the higher binding affinity between PPi and Cu(2+) than that between 11-MUA and Cu(2+). Whereas PPase could catalyze the hydrolysis of PPi, thus released Cu(2+), leading to fluorescence requenching of the AuNCs@11-MUA. In the assay, a good linearity between the fluorescence response and PPase activity within a range from 1 to 20 mU is found, with a detection limit of less than 1 mU, which is better than other PPase assays using PPi as the substrate. Additionally, we demonstrate that our AuNCs@11-MUA-based fluorescent assay can be applied to assay the PPase activity in real biological samples such as the cell lysate. This strategy paves a new avenue for exploring the sensing applications of fluorescence AuNCs and improving the development of competition assay approach. PMID:25030322

Sun, Jian; Yang, Fan; Zhao, Dan; Yang, Xiurong

2014-08-01

209

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

210

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

211

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. PMID:24531300

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

2014-01-01

212

Fluorescence-based affinity labeling of nucleobase by hydrogen-bond forming metal complex.  

PubMed

A new class of nucleobase-binding fluorescent ligand, ND-DOTA in which 2-amino-5,7-dimethyl-1.8-naphthyridine (ND) is conjugated with 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid (DOTA) by an amide linker, was synthesized. On the basis of the experimental results obtained from the DNA melting analysis and fluorescent measurement, ND-DOTA-Tb (III) complex was found to strongly recognize cytosine (C) base opposite an abasic site in DNA duplexes. The binding of ND-DOTA-Tb (III) with C was accompanied by significant quenching of the fluorescence from the naphthyridine moiety (lambdamax, 435 nm), while the emission from the Tb based on lanthanoids energy-transfer luminescence (lambdamax, 550 nm) was relatively unaffected. Such a fluorescence response of ND-DOTA-Tb (III) is to be expected to develop the fluorescence-based affinity labelling of a nucleobase at the single-nucleotide segments in DNA duplexes. PMID:18029707

Yoshimoto, Keitaro; Atsumi, Hiroshi; Saito, Shingo; Okuma, Moriya; Maeda, Mizuo; Nagasaki, Yukio

2007-01-01

213

An ESIPT based fluorescent probe for highly selective and ratiometric detection of periodate.  

PubMed

Periodate is widely used in organic and bioorganic chemistry, and also related to food and environmental safety. To best of our knowledge, there is no efficient tools reported for simultaneously quantifying periodate with high accuracy and discriminating periodate from other forms of iodine. We have synthesized, characterized and applied a first ratiometric fluorescent probe (PDS-2) for simultaneous monitoring of changes of periodate based on the excited-state intramolecular proton transfer mechanism. This PDS-2 based fluorescent technique may enable for a better understanding of periodate related biological and chemical processes. Also, it is an efficient tool for public health, food safety and environmental protection. PMID:25145984

Huang, Chusen; Jia, Ti; Yu, Congjun; Zhang, Amin; Jia, Nengqin

2015-01-15

214

A Coumarin-Based Fluorescent Probe as a Central Nervous System Disease Biomarker  

PubMed Central

Homocysteine and methylmalonic acid are important biomarkers for diseases associated with an impaired central nervous system (CNS). A new chemoassay utilizing coumarin-based fluorescent probe 1 to detect the levels of homocysteine is successfully implemented using Parkinson's disease (PD) patients' blood serum. In addition, a rapid identification of homocysteine and methylmalonic acid levels in blood serum of PD patients was also performed using the liquid chromatography-mass spectrometry (LC-MS). The results obtained from both analyses were in agreement. The new chemoassay utilizing coumarin-based fluorescent probe 1 offers a cost- and time-effective method to identify the biomarkers in CNS patients. PMID:25390405

Yap, Ann-Chee; Mahamad, Ummi Affah; Lim, Shen-Yang; Kim, Hae-Jo; Choo, Yeun-Mun

2014-01-01

215

Simple plant-based design strategies for volatile organic pollutants  

SciTech Connect

Vegetation which enhances in-situ biodegradation of organic compounds can play a key role in the bioremediation of such contaminants in polluted soils and groundwater. Plants may act directly on some contaminants by degrading them, but their main effect is to enhance microbial populations in the thizosphere. Microbially mediated transformations are thus indirectly facilitated by root exudates which nourish the indigenous microorganisms. Plants may also be viewed as a solar driven pump-and-treat system which can contain a plume and reduce the spread of contaminated water. Laboratory investigations carried out in a growth chamber with alfalfa plants provide evidence for the (microbially mediated) biodegradation of organic compounds such as toluene, phenol and TCE. Alfalfa plants tolerate concentrations of these organics in contaminated water up to 100 mg/L. They facilitate transfer of the contaminants from the saturated to the vadose zone. For volatile organic compounds such as TCE, vegetation provides a controlled release of compounds and hence assures dilution of the TCE evapotranspired into the atmosphere from contaminated soils. Using a range of calculated plausible scenarios, it is shown that intermedia transfer caused by volatilization associated with plants is most unlikely to lead to exceedance of standards for gas phase contamination, for most volatile contaminants. Possible action level exceedances might occur with highly toxic substances including vinyl chloride and carbon tetrachloride, if they re present in ground water at levels above kilogram amounts in a single plume of a few hectares, and released by vigorously growing plants under hot dry conditions. Information needed for the calculation and design of plant-based bioremediation systems for typical sites is discussed in this paper.

Narayanan, M.; Erickson, L.E.; Davis, L.C.

1999-12-31

216

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 IC(50)s 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

217

Reductive fluorescence quenching of the photoexcited free base meso-tetrakis (pentafluorophenyl) porphyrin by amines.  

PubMed

Steady state and time resolved fluorescence quenching behaviors of meso-Tetrakis (pentafluorophenyl) porphyrin (H(2)F(20)TPP) in presence of different aliphatic and aromatic amines have been executed in homogeneous dichloromethane (DCM) solution. At room temperature in DCM, free base (H(2)F(20)TPP) shows fluorescence with two distinct peaks at 640 and 711 nm and natural lifetime tauf=9.8 ns which are very similar to that of meso-tetraphenyl porphyrin (TPP). Unlike TPP, addition of both aliphatic and aromatic amines to a solution containing H(2)F(20)TPP results in an efficient decrease in fluorescence intensity without altering the shape and peak position of fluorescence emission. Upon addition of amines there was no change in optical absorption spectra of H(2)F(20)TPP. The fluorescence quenching rate constants ranged from 1 x 10(9) to 4 x 10(9) s(-1), which are one order below to the diffusion control limit, and temperature dependent quenching rate constants yield the activation energies which are found to be order of 0.1 eV. Femto second transient absorption studies reveal the existence of amine cation radical and porphyrin anion radicals with very short decay time (15 ps). The fluorescence quenching reaction follows Stern-Volmer kinetics. Steady state and time-resolved data are interpreted within general kinetic scheme of Marcus semi-classical model which attributes bimolecular electron transfer process between amines and the lowest excited singlet state of H(2)F(20)TPP. Calculated internal reorganization energies are found to be in between 0.04 and 0.22 ev. Variation of electron transfer rate as function of free energy change (DeltaG(0)) points the ET reactions in the present systems are in Marcus normal region. This is the first example of reductive fluorescence quenching of free base neutral porphyrins in homogeneous organic solvent ever known. PMID:20063117

Prashanthi, Suthari; Kumar, P Hemant; Wang, Li; Perepogu, Arun Kumar; Bangal, Prakriti Ranjan

2010-03-01

218

A "turn-on" fluorescent sensor for ultrasensitive detection of melamine based on a new fluorescence probe and AuNPs.  

PubMed

In this study, we synthesized a new fluorescence probe which was used to detect melamine by coupling with gold nanoparticles (AuNPs). The new fluorescence probe has good optical stability and high fluorescence intensity, which can greatly improve the detection sensitivity. Compared to the traditional fluorophore, it is less dependent on the pH value. It has a very strong fluorescence emission peak at 550 nm, which has larger overlap with the absorption peak of AuNPs. When the probe incubates with the AuNPs, the fluorescence of the probe can be effectively quenched by AuNPs. Adding melamine into a probe-AuNPs mixture caused aggregation of AuNPs and released the adsorbed probe; the fluorescence intensity of the probe was recovered. By measuring the changes of the fluorescence intensity of the probe, the detection of melamine can be realized. Under optimized conditions, the linear response to melamine is in the range of 1.0 × 10(-8)-4.0 × 10(-6) mol L(-1) and lowers the detection limit down to 3.0 nmol L(-1) with the sensor. This method can detect melamine in milk and milk-based productions. PMID:25512948

Lu, Qiujun; Zhao, Jiangna; Xue, Shanyan; Yin, Peng; Zhang, Youyu; Yao, Shouzhuo

2015-02-01

219

Label-free detection of kanamycin based on a G-quadruplex DNA aptamer-based fluorescent intercalator displacement assay.  

PubMed

This work was the first to report that the kanamycin-binding DNA aptamer (5'-TGG GGG TTG AGG CTA AGC CGA-3') can form stable parallel G-quadruplex DNA (G4-DNA) structures by themselves and that this phenomenon can be verified by nondenaturing polyacrylamide gel electrophoresis and circular dichroism spectroscopy. Based on these findings, we developed a novel label-free strategy for kanamycin detection based on the G4-DNA aptamer-based fluorescent intercalator displacement assay with thiazole orange (TO) as the fluorescence probe. In the proposed strategy, TO became strongly fluorescent upon binding to kanamycin-binding G4-DNA. However, the addition of kanamycin caused the displacement of TO from the G4-DNA-TO conjugate, thereby resulting in decreased fluorescent signal, which was inversely related to the kanamycin concentration. The detection limit of the proposed assay decreased to 59?nM with a linear working range of 0.1??M to 20??M for kanamycin. The cross-reactivity against six other antibiotics was negligible compared with the response to kanamycin. A satisfactory recovery of kanamycin in milk samples ranged from 80.1% to 98.0%, confirming the potential of this bioassay in the measurement of kanamycin in various applications. Our results also served as a good reference for developing similar fluorescent G4-DNA-based bioassays in the future. PMID:25634469

Xing, Yun-Peng; Liu, Chun; Zhou, Xiao-Hong; Shi, Han-Chang

2015-01-01

220

Label-free detection of kanamycin based on a G-quadruplex DNA aptamer-based fluorescent intercalator displacement assay  

PubMed Central

This work was the first to report that the kanamycin-binding DNA aptamer (5?-TGG GGG TTG AGG CTA AGC CGA-3?) can form stable parallel G-quadruplex DNA (G4-DNA) structures by themselves and that this phenomenon can be verified by nondenaturing polyacrylamide gel electrophoresis and circular dichroism spectroscopy. Based on these findings, we developed a novel label-free strategy for kanamycin detection based on the G4-DNA aptamer-based fluorescent intercalator displacement assay with thiazole orange (TO) as the fluorescence probe. In the proposed strategy, TO became strongly fluorescent upon binding to kanamycin-binding G4-DNA. However, the addition of kanamycin caused the displacement of TO from the G4-DNA–TO conjugate, thereby resulting in decreased fluorescent signal, which was inversely related to the kanamycin concentration. The detection limit of the proposed assay decreased to 59?nM with a linear working range of 0.1??M to 20??M for kanamycin. The cross-reactivity against six other antibiotics was negligible compared with the response to kanamycin. A satisfactory recovery of kanamycin in milk samples ranged from 80.1% to 98.0%, confirming the potential of this bioassay in the measurement of kanamycin in various applications. Our results also served as a good reference for developing similar fluorescent G4-DNA-based bioassays in the future. PMID:25634469

Xing, Yun-Peng; Liu, Chun; Zhou, Xiao-Hong; Shi, Han-Chang

2015-01-01

221

On-chip integrated lensless fluorescence microscopy/spectroscopy module for cell-based sensors  

NASA Astrophysics Data System (ADS)

The integration of a fluorescence microscopy/spectroscopy module in cell-based lab-on-a-chip systems is of high interest for applications in cell-based diagnostics and substance evaluation in situ. We present an on-chip integrated lensless fluorescence imaging module applying the principle of contact/proximate optical lithography. The pixel resolution is comparable with a 4 x objective microscope. The module can be used for morphology and fluorescence imaging of mammalian cells (15 - 20 ?m) as well as for testing the concentration of a fluorescent substance. The biological samples or solutions are sustained in disposable sterilized microfluidic chips with 1 ?m thick silicon nitride (Si3N4) membranes. These chips are assembled on the surface of a 5 megapixel colored CMOS image sensor array with 1.75 ?m pixel size, which is coated with an additional interference filter. Each culturing chip consists of a MEMS cavity chip and a PDMS microfluidic interface. The surface of the CMOS image sensor is smoothened using SU-8 photoresist spin-coating for a commercial grade interference filter (optical density >= 5) coating by Plasma-Ion Assisted Deposition thereafter. The function is demonstrated by primary imaging results of the non-/fluorescent mammalian cells/microspheres as well as by differentiating different concentrations of FITC solutions.

Li, Wei; Knoll, Thorsten; Sossalla, Adam; Bueth, Heiko; Thielecke, Hagen

2011-03-01

222

Development of Fluorescence-Based Liposome Immunoassay for Detection of Cronobacter muytjensii in Pure Culture.  

PubMed

Cronobacter spp. are important foodborne pathogens that carry a very high risk of infection to neonates as well as immunocompromised individuals. In the present study, fluorescence-based liposome immunoassay was developed as a new sensitive and rapid diagnostic system for detection of Cronobacter muytjensii (C. muytjensii). Liposomes (size, 206 nm) used in this study were made from cholesterol, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine, 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine, 1,2-dipalmitoyl-sn-glycero-3-[phospho-rac-(1-glycerol)], and sulforhodamine B (SRB). The outer surface of liposome was conjugated with rabbit anti-C. muytjensii IgG in order to develop immunoliposome. The immunoliposome was incubated with C. muytjensii, which was coated on a 96-well plate. Immunoliposomes bound to C. muytjensii were lysed with 30 mM octyl ?-D-glucopyranoside, after which the SRB fluorescence signal was measured at an excitation wavelength of 550 nm and emission wavelength of 585 nm. The signal was directly proportional to the amount of bacterial cells in the test sample. The developed fluorescence-based liposome immunoassay was confirmed to be highly specific to C. muytjensii with a detection limit of 6.3 × 10(4) CFU ml(-1) in pure culture as well as sensitive, efficient, and rapid when compared to culture-based methods. Based on its rapid efficiency and low cost, this fluorescence-based liposome immunoassay may be used to develop diagnostic kits for C. muytjensii detection. PMID:25300633

Song, Xinjie; Shukla, Shruti; Oh, Sejong; Kim, Younghoan; Kim, Myunghee

2015-02-01

223

Label-Free and Sensitive Fluorescent Detection of Sequence-Specific Single-Strand DNA Based on S1 Nuclease Cleavage Effects  

PubMed Central

The ability to detect sequence-specific single-strand DNA (ssDNA) in complex, contaminant-ridden samples, using a fluorescent method directly without a DNA extraction and PCR step could simplify the detection of pathogens in the field and in the clinic. Here, we have demonstrated a simple label-free sensing strategy to detect ssDNA by employing its complementary ssDNA, S1 nuclease and nucleic acid fluorescent dyes. Upon clearing away redundant complementary ssDNA and possibly mismatched double strand DNA by using S1 nuclease, the fluorescent signal-to-noise ratio could be increased dramatically. It enabled the method to be adaptable to three different types of DNA fluorescent dyes and the ability to detect target ssDNA in complex, multicomponent samples, like tissue homogenate. The method can distinguish a two-base mismatch from avian influenza A (H1N1) virus. Also, it can detect the appearance of 50 pM target ssDNA in 0.5 µg·mL?1 Lambda DNA, and 50 nM target ssDNA in 5 µg·mL?1 Lambda DNA or in tissue homogenate. It is facile and cost-effective, and could be easily extended to detect other ssDNA with many common nucleic acid fluorescent dyes. PMID:25285445

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

2014-01-01

224

Fluorescence-based, high-throughput assays for ?-opioid receptor activation using a membrane potential-sensitive dye.  

PubMed

The development of new and improved opioid analgesics requires high-throughput screening (HTS) methods to identify potential therapeutics from large libraries of lead compounds. Here we describe two simple, real-time fluorescence-based assays of ?-opioid receptor activation that may be scaled up for HTS. In AtT-20 cells expressing the ?-opioid receptor (MOPr), opioids activate endogenous G protein gated inwardly rectifying K channels (GIRK channels), leading to membrane hyperpolarization. In Chinese hamster ovary cells expressing MOPr, adenylyl cyclase activation via forskolin results in membrane hyperpolarization, which is inhibited by opioids. Changes in membrane potential can be measured using a proprietary membrane potential-sensitive dye. In contrast to many HTS methods currently available, these assays reflect naturalistic coupling of the receptor to effector molecules. PMID:25293325

Knapman, Alisa; Connor, Mark

2015-01-01

225

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

226

Colorimetric and "turn-on" fluorescent determination of Cu2+ ions based on rhodamine-quinoline derivative.  

PubMed

A novel rhodamine-quinoline derivative-based indicator for Cu(2+) ion determination was designed and synthesized. It exhibited highly selective and sensitive colorimetric and "turn-on" fluorescent responses toward Cu(2+) ions based on the ring-opening mechanism of the rhodamine spirolactam in aqueous solution. The colorimetric and fluorescent responses were recorded using a domestic scanner and camera-based home-made fluorescent imaging unit, separately. The images were digitized, and the red (R), green (G), and blue (B) values were investigated. Both colorimetric and fluorescent methods showed good selectivity, and the color/fluorescence changes were remarkable for the Cu(2+) ion detection even in the presence of other metal ions. The good linear relationship was easily obtained between the color/fluorescence changes and the concentrations in the range of 20-120 ?M. PMID:23099824

Feng, Liang; Li, Hui; Lv, Yongjun; Guan, Yafeng

2012-12-21

227

Gaseous ammonia fluorescence probe based on cellulose acetate modified microstructured optical fiber  

Microsoft Academic Search

In this article, we report a novel fluorescent ammonia gas probe based on microstructured optical fiber (MOF) which is modified with eosin-doped cellulose acetate film. This probe was fabricated by liquid fluxion coating process. Polymer solution doped with eosin was directly inhaled into 18 array holes of MOF and then formed matrix film in them. The sensing properties of the

Lirong Peng; Xinghua Yang; Libo Yuan; Lili Wang; Enming Zhao; Fengjun Tian; Yanxin Liu

2011-01-01

228

Fluorescence from a gelatin-based film containing isolated and orientated single-walled carbon nanotubes  

E-print Network

Fluorescence from a gelatin-based film containing isolated and orientated single-walled carbon a technique to fabricate a gelatin thin film that contains orientated and individually dispersed single with gelatin, and the gelatin-SWNTs solution was spread over a SiO2 substrate by sliding a wire-bar uniformly

Maruyama, Shigeo

229

A biosensor for theophylline based on fluorescence detection of ligand-induced  

E-print Network

A biosensor for theophylline based on fluorescence detection of ligand-induced hammerhead ribozyme hammerhead ribozymes that rearrange from a catalytically inactive to an active conformation upon allosteric­acceptor fluorophore pair to the termini of the substrate RNA of such a hammerhead ribozyme, modified to cleave

Walter, Nils G.

230

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

231

Label-free fluorescent assays based on aptamer-target recognition.  

PubMed

Label-free fluorescent assays were developed based on the competition of intramolecular DNA hybridization and aptamer-target binding. Using small molecule adenosine triphosphate (ATP) and biomacro-molecule thrombin as model targets, our design was proved to be a general method with good sensitivity and high selectivity. PMID:22451893

Tan, Ying; Zhang, Xin; Xie, Yonghua; Zhao, Rui; Tan, Chunyan; Jiang, Yuyang

2012-05-21

232

Highly efficient non-doped fluorescent OLEDs based on aggregation-induced emission emitters  

E-print Network

26 Highly efficient non-doped fluorescent OLEDs based on aggregation-induced emission emitters into the host to alleviate the ACQ effect. However, the fabrication of OLEDs with doped layers is complex and thus it is desirable to develop non-doped OLEDs with high efficiency. In this talk, a series of highly

233

Turn-On Fluorescent Chemosensor for Hg2+ Based on Multivalent Rhodamine Ligands  

PubMed Central

Rhodamine-based fluorescent chemosensors 1 and 2 exhibit selective fluorescence enhancement to Fe3+ and Hg2+ over other metal ions at 580 nm in CH3CN/H2O (3/1, v/v) solution. Bis(rhodamine) chemosensor 1, under optimized conditions (CH3CN/HEPES buffer (0.02 M, pH = 7.0) (95/5, v/v)), shows a high selectivity and sensitivity to Hg2+, with a linear working range of 0–50 ?M, a wide pH span of 4–10, and a detection limit of 0.4 ?M Hg2+. PMID:23222686

Wang, Xuemei; Iqbal, Mudassir; Huskens, Jurriaan; Verboom, Willem

2012-01-01

234

Analysis of protein-based binding media found in paintings using laser induced fluorescence spectroscopy.  

PubMed

Laser induced fluorescence (LIF) spectroscopy of intrinsic fluorophores from organic media found in paintings (casein, animal glue and egg proteins) provides novel non-invasive means of characterisation of general classes of media on the basis of fluorescence emission arising from the presence of certain amino acids and their degradation byproducts. Proteins from traditionally employed binding media include collagen, casein, albumin and other egg proteins, of animal sources (skins, milk and egg respectively). Wavelength dependence of the spectra is presented for analyses of thin films of protein-based binding media. PMID:17723543

Nevin, Austin; Cather, Sharon; Anglos, Demetrios; Fotakis, Costas

2006-07-28

235

Light collection from fluorescence-based biochips by holographic diffractive optical elements  

NASA Astrophysics Data System (ADS)

A fluorescence-based biochip with an integrated holographic diffractive optical element on its underside is presented. The diffractive element is a thick volume hologram written into a layer of photopolymer recording material. The element acts as a collector of the spatially anisotropic fluorescence light emitted from surface-bound fluorophores and redirects the light to a CCD detector. The holographic lithography setup used to fabricate the diffractive elements is described. The performance of the diffractive elements to enhance the light collection is demonstrated.

Macko, Peter; Whelan, Maurice P.

2009-07-01

236

Fluorescence turn-on sensor for cyanide based on a cobalt(II)-coumarinylsalen complex.  

PubMed

A Co(II)-salen based fluorescent sensor (1.Co) that can selectively recognize cyanide anions in 1:2 binding stoichiometry over other anions has been developed. 1.Co displayed fluorescence enhancement upon the addition of cyanide owing to the interruption of photoinduced electron transfer from the coumarin fluorophore to the cobalt(II) ion. A general regression method was developed to calculate the binding constants in the 1:2 binding system, through which the 1:2 binding between 1.Co and cyanide anions was estimated to be in the range of micromolar dissociation constants. PMID:20092265

Lee, Jae Han; Jeong, A Reum; Shin, Ik-Soo; Kim, Hae-Jo; Hong, Jong-In

2010-02-19

237

A rhodamine-based fluorescent probe for detecting Hg(2+) in a fully aqueous environment.  

PubMed

A water-soluble fluorescent probe for Hg(2+) based on a rhodamine B derivative was designed and synthesized. The new probe showed reversible colorimetric and fluorescent response to Hg(2+) in a fully aqueous solution. The probe exhibited real-time detection of Hg(2+) with high selectivity in media containing less than 1% organic cosolvent. Furthermore, bioimaging studies indicated that the new probe was cell permeable and suitable for the real-time imaging of Hg(2+) in living cells by confocal microscopy. PMID:23986178

Chen, Xiaoli; Meng, Xiangming; Wang, Shuxing; Cai, Yulei; Wu, Yifan; Feng, Yan; Zhu, Manzhou; Guo, Qingxiang

2013-10-01

238

Fluorescent reversible regulation based on the interactions of topotecan hydrochloride, neutral red and quantum dots  

NASA Astrophysics Data System (ADS)

The interactions of topotecan hydrochloride (THC), neutral red (NR) and thioglycolic acid (TGA) capped CdTe/CdS quantum dots (QDs) built a solid base for the controlling of the fluorescent reversible regulation of the system. This study was developed by means of ultraviolet-visible (UV-vis) absorption, fluorescence (FL), resonance Rayleigh scattering (RRS) spectroscopy and transmission electron microscopy (TEM). Corresponding experimental results revealed that the fluorescence of TGA-CdTe/CdS QDs could be effectively quenched by NR, while the RRS of the QDs enhanced gradually with the each increment of NR concentration. After the addition of THC, the strong covalent conjugation between NR and THC which was in carboxylate state enabled NR to be dissociated from the surface of TGA-CdTe/CdS QDs to form more stable complex with THC, thereby enhancing the fluorescence of the TGA-CdTe/CdS QDs-NR system. What is more, through analyzing the optical properties and experimental data of the reaction between TGA-CdTe/CdS QDs and NR, the possible reaction mechanism of the whole system was discussed. This combination of multiple spectroscopic techniques could contribute to the investigation for the fluorescent reversible regulation of QDs and a method could also be established to research the interactions between camptothecin drugs and dyes.

Wang, Linlin; Shen, Yizhong; Liu, Shaopu; Yang, Jidong; Liang, Wanjun; Li, Dan; He, Youqiu

2015-02-01

239

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

240

Fluorescent reversible regulation based on the interactions of topotecan hydrochloride, neutral red and quantum dots.  

PubMed

The interactions of topotecan hydrochloride (THC), neutral red (NR) and thioglycolic acid (TGA) capped CdTe/CdS quantum dots (QDs) built a solid base for the controlling of the fluorescent reversible regulation of the system. This study was developed by means of ultraviolet-visible (UV-vis) absorption, fluorescence (FL), resonance Rayleigh scattering (RRS) spectroscopy and transmission electron microscopy (TEM). Corresponding experimental results revealed that the fluorescence of TGA-CdTe/CdS QDs could be effectively quenched by NR, while the RRS of the QDs enhanced gradually with the each increment of NR concentration. After the addition of THC, the strong covalent conjugation between NR and THC which was in carboxylate state enabled NR to be dissociated from the surface of TGA-CdTe/CdS QDs to form more stable complex with THC, thereby enhancing the fluorescence of the TGA-CdTe/CdS QDs-NR system. What is more, through analyzing the optical properties and experimental data of the reaction between TGA-CdTe/CdS QDs and NR, the possible reaction mechanism of the whole system was discussed. This combination of multiple spectroscopic techniques could contribute to the investigation for the fluorescent reversible regulation of QDs and a method could also be established to research the interactions between camptothecin drugs and dyes. PMID:25459722

Wang, Linlin; Shen, Yizhong; Liu, Shaopu; Yang, Jidong; Liang, Wanjun; Li, Dan; He, Youqiu

2014-10-24

241

Upconversion nanoparticle-based fluorescence resonance energy transfer assay for Cr(III) ions in urine.  

PubMed

A novel assay of chromium(III) ion based on upconversion fluorescence resonance energy transfer was designed and established. Lysine-capped NaYF(4):Yb/Er upconversion nanoparticles (UCNPs) and dimercaptosuccinic acid-capped gold nanoparticles (AuNPs) were used as the energy donor and acceptor, respectively. They were bound together via electrostatic interaction, resulting in the quenching of the fluorescence of UCNPs by AuNPs. Chromium(III) ions can specifically and strongly interact with dimercaptosuccinic acid that was modified on the surface of AuNPs, leading to the separation of AuNPs from UCNPs and the recovery of fluorescence of UCNPs. The fluorescence recovery of UCNPs showed a good linear response to Cr(3+) concentration in the range of 2-500 nM with a detection limit of 0.8 nM. This method was further applied to determine the levels of Cr(3+) in urine. Compared with other fluorescence methods, current method displayed very high sensitivity and signal-to-noise ratio because of the excitation of near-infrared that can eliminate autofluorescence, providing a promising examination of biological samples for the diagnostic purposes. PMID:23312329

Liu, Baoxia; Tan, Hongliang; Chen, Yang

2013-01-25

242

Enhanced chemical fluorescence-based sensing using metallic nano-composites  

NASA Astrophysics Data System (ADS)

It has been recently shown that the favorable effects of enhanced fluorescent intensities, reduced lifetimes (increased probe photostabilities), enhanced and localized rates of multiphoton excitation, and modified rates of energy transfer can occur for fluorophores or biological species of interest, in close proximity to noble metallic nano-structures and surfaces. Subsequently, nano-metal-enhanced fluorescence (NanoMEF) is yielding enormous opportunities for enhanced fluorescence sensing and imaging in microfluidics, lab-on-a-chip, clinical diagnostics, and cellular applications. NanoMEF is a through-space phenomenon relying on interaction of fluorophores with metallic nanoparticles in the presence of excitation light. MEF can be utilized to produce nanometer-size sensors, which display enhanced spectral properties, whie still potentially maintaining a probes free space-sensing functionalities. In this presentation we report our recent findings on the effects of silver nano-particles on the spectral properties of two representative fluorescent probes for pH and Ca2+ measurements. We demonstrate that quantum efficiencies of probes are greatly enhanced providing more reliable chemical sensing capabilities. Our findings promise a new class of potential sensors, which we believe could constitute a new breed of composite nanosensors based on metal-enhanced fluorescence and their applications in miniaturized systems.

Szmacinski, Henryk; Pugh, Vincent; Moore, Wayne E.; Geddes, Chris D.; Aslan, Kadir; Lakowicz, Joseph R.

2004-07-01

243

Extraction of lifetime distributions from fluorescence decays with application to DNA-base analogues.  

PubMed

Several important aspects of fluorescence decay analysis are addressed and tested against new experimental measurements. A simulated-annealing method is described for deconvoluting the instrument response function from a measured fluorescence decay to yield the true decay, which is more convenient for subsequent fitting. The method is shown to perform well against the conventional approach, which is to fit a convoluted fitting function to the experimentally measured decay. The simulated annealing approach is also successfully applied to the determination of an instrument response function using a known true fluorescence decay (for rhodamine 6G). The analysis of true fluorescence decays is considered critically, focusing specifically on how a distribution of decay constants can be incorporated in to a fit. Various fitting functions are applied to the true fluorescence decays of 2-aminopurine in water-dioxane mixtures, in a dinucleotide, and in DNA duplexes. It is shown how a suitable combination of exponential decays and non-exponential decays (based on a ? distribution of decay constants) can provide fits of equal quality to the conventional multi-exponential fits used in the majority of previous studies, but with fewer fitting parameters. Crucially, the new approach yields decay-constant distributions that are physically more meaningful than those corresponding to the conventional multi-exponential fit. The methods presented here should find wider application, for example to the analysis of transient-current or optical decays and in Förster resonance energy transfer (FRET). PMID:21212896

Fogarty, Aoife C; Jones, Anita C; Camp, Philip J

2011-03-01

244

A fluorescent chemosensor for Hg2+ based on a rhodamine derivative in an aqueous solution.  

PubMed

In this paper, we unveil a novel rhodamine compound-based fluorescent chemosensor (compound 1) for fluorescent detection of Hg(2+) in an aqueous solution. The fluorescence enhancement of compound 1 was attributed to the formation of a complex between compound 1 and Hg(2+) by 1:1 complex ration (K = 8.0 × 10(4)), which has been utilized as the basis of fabrication of the Hg(2+)-sensitive chemosensor. A comparison of this method with some other fluorescence methods for the determination of Hg(2+) indicated that this method has high selectivity and good water solubility. The analytical performance characteristics of the proposed Hg(2+)-sensitive chemosensor were investigated. The chemosensor can be applied to the quantification of Hg(2+) with a linear range from 6.6 × 10(-7) to 2.4 × 10(-4) M and a detection limit of 1.3 × 10(-7) M. The experiment results show that the response behavior of compound 1 towards Hg(2+) is pH independent in neutral conditions (pH 5.0-9.0). Most importantly, the fluorescence changes of the chemosensor are remarkably specific for Hg(2+) in the presence of other metal ions, which meet the selective requirements for practical application. Moreover, the response of the chemosensor toward Hg(2+) is fast (response time less than 1 min). In addition, the chemosensor has been used for the determination of Hg(2+) in river water samples with satisfactory results. PMID:24025574

Li, Chun-Yan; Zhou, Yu; Li, Yong-Fei; Zou, Chun-Xiang; Kong, Xue-Fei

2013-01-01

245

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. PMID:22163636

Pietsch, Christian; Vollrath, Antje; Hoogenboom, Richard; Schubert, Ulrich S.

2010-01-01

246

Crystal structure and fluorescence sensing properties of tetramethoxyresorcinarene functionalized Schiff bases  

NASA Astrophysics Data System (ADS)

A series of tertamethoxyresorcinarene functionalized Schiff bases were conveniently prepared by the reaction of resorcinarene ester derivatives with excess of ethylenediamine and then condensation with salicylaldehyde. The single crystal analysis of five products shows that tetramethoxyresorcinarenes existed in chair conformation. The complexing properties of these polydentated ligands to transition metal ions were studied by UV-Vis and fluorescence spectroscopy. The results demonstrate that these polydentated ligands are more efficient for recognition of Zn2+ in preference to other metal ions, accompanying a remarkable fluorescence intensity enhancement. Taking 4a as an example, it exhibits a 13-fold fluorescence enhancement upon the addition of 3 equiv. of Zn2+ in CH3OH/CH3CN (1:9 v/v) solution.

Li, Liang; Sun, Jing; Zhang, Li-Li; Yao, Rong; Yan, Chao-Guo

2015-02-01

247

[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

248

A sensitive biosensor for the fluorescence detection of the acetylcholinesterase reaction system based on carbon dots.  

PubMed

The carbon dots (C-dots) with high fluorescence quantum yield were prepared using hydrothermal method. C-dots have been adopted as probes for the fluorescence turn-off detection of H2O2 based on the special sensibility for the hydroxyl radical. And then the biosensors for the detection of substrate and enzymes activities were established in the acetylcholinesterase reaction system, which were related to the production of H2O2. Specifically, the proposed fluorescent biosensor was successfully applied to detect the concentration of choline (in the range from 0.025 to 50?M) and acetylcholine (in the range from 0.050 to 50?M), and the activity of choline oxidase (in the range from 1 to 75U/L) and acetylcholinesterase (1 to 80U/L). These results showed a sensitive, universal, nontoxic and eco-friendly detecting technique has been developed. PMID:25500325

Ren, Xiangling; Wei, Jianfei; Ren, Jun; Qiang, Li; Tang, Fangqiong; Meng, Xianwei

2015-01-01

249

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.

2006-04-01

250

Atom localization via resonance fluorescence  

Microsoft Academic Search

We propose a simple scheme of atom localization based on resonance fluorescence from a standing-wave field. The Rabi frequency is position dependent and therefore the spontaneously emitted photon carries the information of the atomic center-of-mass motion. This leads to atom localization even during the flight through the standing-wave field.

Sajid Qamar; Shi-Yao Zhu; M. Suhail Zubairy

2000-01-01

251

Vision-Based Navigation of Mobile Robot using Fluorescent Tubes  

E-print Network

which are located above it's desired path thanks to a camera pointing to the ceiling. After explaining, it uses sensors to know its relative localization by summing elementary displacements provided by incremen them. Therefore navigation based on ceiling landmark recognition can be thought as an alterna- tive

Ohya, Akihisa

252

Nucleic acid based fluorescent sensor for mercury detection  

DOEpatents

A nucleic acid enzyme comprises an oligonucleotide containing thymine bases. The nucleic acid enzyme is dependent on both Hg.sup.2+and a second ion as cofactors, to produce a product from a substrate. The substrate comprises a ribonucleotide, a deoxyribonucleotide, or both.

Lu, Yi; Liu, Juewen

2013-02-05

253

Fluorescence-based Total Protein Determination using the Compound CBQCA  

E-print Network

techniques are available that eliminate many of the problems associated with the traditional colorimetric, many different absorbance-based colorimetric methods to quantify protein have been developed, the most contamination. Dye- binding protein assays such as that described by Bradford (3) have also been developed

Raizada, Manish N.

254

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

255

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

256

Polarized - and Two-Photon Fluorescence Excitation Spectroscopy on Selected Nucleic Acid Bases  

NASA Astrophysics Data System (ADS)

The first two-photon fluorescence excitation spectra of thymine, cytosine and the four nucleotides of deoxyribonucleic acid (DNA) are reported. These were obtained using neutral aqueous solutions at room temperature in the spectral range 400-600nm delivered by a pulsed (8nsec) ND-YAG pumped dye laser. The low fluorescence quantum yields (10 ^{-4}) established a new detection domain for the two-photon fluorescence excitation technique, for molecules in solution, made possible by strong two -photon absorptions and short lifetimes. The two-photon polarization ratio (delta_{rm cir}/delta_{rm lin}) was low and constant for the 260nm region of thymine and TMP, but exhibited a maximum at 220nm, therefore, confirming the singular nature of the lowest pipi ^* band and the composite nature of the 205nm band. The data for CMP is consistent with either three or four pipi^* transitions in the 192-300nm region. In no case did the two-photon peaks exactly coincide with their one-photon counterparts. This result was puzzling for the thymine and TMP 260nm band which is strongly allowed under both one- and two-photon absorption. Extensive testing procedures are reported to confirm the intrinsic origin of the data obtained. The experimental two-photon data for the nucleotides and bases are compared to the predicted values calculated using the current semiempirical molecular orbital (INDO/S) methods. Polarized one-photon fluorescence excitation and emission spectra of thymine in room temperature aqueous solution as a function of pH are reported. In contrast to the high and constant fluorescence anisotropy across the first absorption envelope found for thymine dissolved in a pH 5.0 aqueous buffer, a loss in fluorescence anisotropy (DeltaR cong 0.2) is observed for thymine at neutral pH when excited at wavelengths greater than 280nm. This loss in fluorescence anisotropy for thymine at neutral pH is explained by the presence of a small equilibrium concentration of the highly fluorescent thymine anion (pKa = 9.9). No evidence for the presence of a weakly absorbing low-lying state under the first absorption band is found for thymine in room temperature aqueous solution. The fluorescence anisotropies of uracil and UMP are also reported for the first time.

Williams, Scott Allan

257

A fluorescence detection of D-penicillamine based on Cu2+-induced fluorescence quenching system of protein-stabilized gold nanoclusters  

NASA Astrophysics Data System (ADS)

In this contribution, a luminescent gold nanoclusters which were synthesized by bovine serum albumin as novel fluorescent probes were successfully utilized for the determination of D-penicillamine for the first time. Cupric ion was employed to quench the strong fluorescence of the gold nanoclusters, whereas the addition of D-penicillamine caused obvious restoration of fluorescence intensity of the Cu2+-gold nanoclusters system. Under optimum conditions, the increment in fluorescence intensity of Cu2+-gold nanoclusters system caused by D-penicillamine was linearly proportional to the concentration of D-penicillamine in the range of 2.0 × 10-5-2.39 × 10-4 M. The detection limit for D-penicillamine was 5.4 × 10-6 M. With the off-on fluorescence signal at 650 nm approaching the near-infrared region, the present sensor for D-penicillamine detection had high sensitivity and low spectral interference. Furthermore, the novel gold nanoclusters-based fluorescent sensor has been applied to the determination of D-penicillamine in real biological samples with satisfactory results.

Wang, Peng; Li, Bang Lin; Li, Nian Bing; Luo, Hong Qun

2015-01-01

258

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

259

Highly sensitive fluorescent immunosensor for detection of influenza virus based on Ag autocatalysis.  

PubMed

A versatile, ultrasensitive immunosensor for detection of influenza virus was designed by combining silver nanoparticles (Ag NPs) labeled antibodies with indirect fluorescence. A new technology using Ag-S covalent binding was applied for antibody labeling. Influenza A (H1N1) virus, as a subtype of influenza A virus that was the most common cause of human influenza (flu), was acted as the target antigen using sandwich type-immunoreactions on the high binding ELISA plates. The antibody-labeled Ag NPs were then released by acid solution to produce Ag(+) which can catalyze o-phenylenediamine (OPDA) oxidation to produce fluorescence for highly sensitive detection. Under the optimal conditions, it shows good linear relationship between fluorescence intensity and the logarithm of the concentration of H1N1 over the range of 1.0×10(-12)-1.0×10(-8) g mL(-1) with a detection limit (LOD, 3?) of 1.0×10(-13) g mL(-1). Results indicated that the proposed method give a good sensitivity and simple operation for detecting the influenza virus. This work also provided a promising potential for antigen detection by Ag NPs labeled, and the steps were easy to handle. PMID:24292140

Li, Yanxia; Hong, Mei; Qiu, Bin; Lin, Zhenyu; Chen, Yiting; Cai, Zongwei; Chen, Guonan

2014-04-15

260

Aptamer-based folding fluorescent sensor for cocaine.  

PubMed

We adapted in two steps a deoxyribonucleotide-based aptamer to signal the recognition of cocaine: an instability was engineered in one stem of a three-way junction that forms the cocaine-binding pocket and the resulting short stem was end labeled with a fluorophore and a quencher. In the absence of cocaine, two stems are open, but in its presence they close and the three-way junction forms. This major structural change brings fluorophore and quencher together thereby signaling the presence and concentration of ligand. The sensor is selective for cocaine over its metabolites, can operate in serum, and is useful for the screening of cocaine hydrolases. PMID:11457319

Stojanovic, M N; de Prada, P; Landry, D W

2001-05-30

261

Simple and sensitive high-performance liquid chromatography--fluorescence method for the determination of citrinin application to the analysis of fungal cultures and cheese extracts.  

PubMed

A new and highly sensitive method for the detection of the important mycotoxin, citrinin, has been developed. Spectroscopic studies demonstrate that the fluorescence of this metabolite is influenced by the pH of the environment. This fact was exploited in the chromatographic determination of citrinin with fluorescence detection. The proposed method, based on the addition of 1 M hydrochloric acid as an acidic post-column reagent, has a limit of detection of 0.9 center dot 10(-7) M. Analytical validation shows that linearity can be assumed from 2 center dot 10(-7) to 10(-4) M citrinin. The repeatability and reproducibility are satisfactory, with R.S.D. = 5.1% (n = 9, c = 10(-5) M) and R.S.D. = 7.2% (n = 9, c = 10(-5) M). The method was also applied to the determination of this mycotoxin produced by mould cultures isolated from soft cheese and also from soft cheese and also from cheese extracts spiked with citrinin. The specificity of the method is demonstrated and the necessity for post-column acidification is illustrated on real samples. PMID:8819823

Franco, C M; Fente, C A; Vazquez, B; Cepeda, A; Lallaoui, L; Prognon, P; Mahuzier, G

1996-02-01

262

Determination of trace terbium(III) with N, N', N"-tri(3-indolemethanal)triaminotriethylamine based on a new fluorescence enhancement system.  

PubMed

A new Schiff-base ligand with a tripodal structure, N,N',N"-tri(3-indolemethanal)triaminotriethylamine (TTAIM), was synthesized. Its fluorescence intensity with terbium(III) was increased by about two orders of magnitude in the present of sodium acetate (NaAc). After the adding of the organic solvent dimethyl sulfoxide (DMSO) to the above system, leading to Tb3+ the fluorescence was further enhanced by about 16 fold. The spectrofluorimetric determination of a trace amount of Tb3+ based on this phenomenon was carried out. The excitation and emission wavelengths were 330 nm and 545 nm, respectively. Under the optimal conditions, the fluorescence intensities varied linearly with the concentration of Tb3+ in the range of 5.7 x 10(-11) - 6.3 x 10(-6) mol L(-1) with a detection limit of 5.0 x 10(-11) mol L(-1). The interferences of some rare earth metals and other inorganic ions were described. The method is a selective, sensitive, rapid and simple analytical procedure for the determination of terbium(III) in a high-purity yttrium oxide and synthetic sample. The mechanism for the fluorescence enhancement was also studied. PMID:15055966

Yang, Tianlin; Tai, Xishi; Qin, Wenwu; Liu, Weisheng; Tan, Minyu

2004-02-01

263

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

264

Nicking enzyme-assisted biosensor for Salmonella enteritidis detection based on fluorescence resonance energy transfer.  

PubMed

Salmonella enteritidis (S. enteritidis) outbreaks continue to occur, and have increased public awareness of this pathogen. Nicking endonuclease Nb.BbvC I is widely used for the detection of biomolecules and displays activity for specific double-stranded DNA (dsDNA). In this study, we developed a biosensor to detect S. enteritidis based on fluorescence resonance energy transfer (FRET) using nicking enzyme and carbon nanoparticles (CNPs). Because of the quenching effect of black hole quencher 1 (BHQ 1), the CNPs do not fluoresce in the reaction system. When the target bacteria are added, the nicking enzyme recognizes and cleaves the dsDNA fabricated by the interaction between probe and target. As a result, the CNPs dissociate from BHQ 1 and emit strong fluorescence. Using the nicking enzyme, the fluorescence signals of the biosensor are greatly amplified. The biosensor exhibited a linear relationship with the concentration of S. enteritidis ranging from 10(2) to 3 × 10(3)CFU/mL in water and from 1.5 × 10(2) to 3 × 10(3)CFU/mL in milk. The present results indicate that our FRET-based detection system can be widely employed for the effective detection of pathogens. PMID:24434495

Song, Yang; Li, Wenkai; Duan, Yingfen; Li, Zhongjie; Deng, Le

2014-05-15

265

A Patch-Based Method for Repetitive and Transient Event Detection in Fluorescence Imaging  

PubMed Central

Automatic detection and characterization of molecular behavior in large data sets obtained by fast imaging in advanced light microscopy become key issues to decipher the dynamic architectures and their coordination in the living cell. Automatic quantification of the number of sudden and transient events observed in fluorescence microscopy is discussed in this paper. We propose a calibrated method based on the comparison of image patches expected to distinguish sudden appearing/vanishing fluorescent spots from other motion behaviors such as lateral movements. We analyze the performances of two statistical control procedures and compare the proposed approach to a frame difference approach using the same controls on a benchmark of synthetic image sequences. We have then selected a molecular model related to membrane trafficking and considered real image sequences obtained in cells stably expressing an endocytic-recycling trans-membrane protein, the Langerin-YFP, for validation. With this model, we targeted the efficient detection of fast and transient local fluorescence concentration arising in image sequences from a data base provided by two different microscopy modalities, wide field (WF) video microscopy using maximum intensity projection along the axial direction and total internal reflection fluorescence microscopy. Finally, the proposed detection method is briefly used to statistically explore the effect of several perturbations on the rate of transient events detected on the pilot biological model. PMID:20976222

Boulanger, Jérôme; Gidon, Alexandre; Kervran, Charles; Salamero, Jean

2010-01-01

266

Nonlinear Emission of Quinolizinium-Based Dyes with Application in Fluorescence Lifetime Imaging.  

PubMed

Charged molecules based on the quinolizinum cation have potential applications as labels in fluorescence imaging in biological media under nonlinear excitation. A systematic study of the linear and nonlinear photophysics of derivatives of the quinolizinum cation substituted by either dimethylaniline or methoxyphenyl electron donors is performed. The effects of donor strength, conjugation length, and symmetry in the two-photon emission efficiency are analyzed in detail. The best performing nonlinear fluorophore, with two-photon absorption cross sections of 1140 GM and an emission quantum yield of 0.22, is characterized by a symmetric D-?-A(+)-?-D architecture based on the methoxyphenyl substituent. Application of this molecule as a fluorescent marker in optical microscopy of living cells revealed that, under favorable conditions, the fluorophore can be localized in the cytoplasmatic compartment of the cell, staining vesicular shape organelles. At higher dye concentrations and longer staining times, the fluorophore can also penetrate into the nucleus. The nonlinearly excited fluorescence lifetime imaging shows that the fluorophore lifetime is sensitive to its location in the different cell compartments. Using fluorescence lifetime microscopy, a multicolor map of the cell is drafted with a single dye. PMID:25135761

Marcelo, Gema; Pinto, Sandra; Cañeque, Tatiana; Mariz, Inês F A; Cuadro, Ana M; Vaquero, Juan J; Martinho, José M G; Maçôas, Ermelinda M S

2014-09-01

267

Sensitive detection of acetylcholine based on a novel boronate intramolecular charge transfer fluorescence probe.  

PubMed

A highly sensitive and selective fluorescence method for the detection of acetylcholine (ACh) based on enzyme-generated hydrogen peroxide (H2O2) and a new boronate intramolecular charge transfer (ICT) fluorescence probe, 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-N-butyl-1,8-naphthalimide (BN), was developed. This strategy involves the reaction of ACh with acetylcholinesterase (AChE) to produce choline, which is further oxidized by choline oxidase (ChOx) to obtain betaine and H2O2. The enzyme-generated H2O2 reacts with BN and results in hydrolytic deprotection of BN to generate fluorescent product (4-hydroxyl-N-butyl-1,8-naphthalimide, ON). Two consecutive linear response ranges allow determining ACh in a wide concentration range with a low detection limit of 2.7nM (signal/noise=3). Compared with other fluorescent probes based on the mechanism of nonspecific oxidation, this reported boronate probe has the advantage of no interference from other biologically relevant reactive oxygen species (ROS) on the detection of ACh. This study provides a new method for the detection of ACh with high selectivity and sensitivity. PMID:25132563

Liu, Chang; Shen, Youming; Yin, Peng; Li, Lidong; Liu, Meiling; Zhang, Youyu; Li, Haitao; Yao, Shouzhuo

2014-08-14

268

Streptavidin sensor and its sensing mechanism based on water-soluble fluorescence conjugated polymer  

NASA Astrophysics Data System (ADS)

Fluorescence quenching effect of water-soluble anionic conjugated polymer (CP) (poly[5-methoxy-2-(3-sulfopoxy)-1,4-phenylenevinylene] (MPS-PPV)) by [Re(N-N)(CO)3(py-CH2-NH-biotin)](PF6) [N-N=2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline; py-CH2-NH-biotin=N-[(4-pyridyl) methyl] biotinamide] (Re-Biotin) and fluorescence recovery in the presence of streptavidin (or avidin) were investigated using Re-Biotin as quencher tether ligand (QTL) probe. Meanwhile, the mechanisms of fluorescence quenching and recovery were discussed to provide new thoughts to design biosensor based on water-soluble CPs. The results indicate that the sensing mechanisms of streptavidin sensor or avidin sensor, using Re-Biotin as QTL probe, are the same and stable, whether in non-buffer system (aqueous solution) or different buffer systems [0.01 mol·L-1 phosphate buffered solution (pH = 7.4), 0.1 mol·L-1 ammonium carbonate buffered solution (pH = 8.9)]. There exists specific interactions between streptavidin (or avidin) and biotin of Re-Biotin. Fluorescence quenching and recovery processes of MPS-PPV are reversible. Mechanisms of Re-Biotin quenching MPS-PPV fluorescence can be interpreted as strong electrostatic interactions and charge transferences between Re-Biotin and MPS-PPV. Fluorescence recovery mechanisms of Re-Biotin-MPS-PPV system can be interpreted as specific interactions between streptavidin (or avidin) and biotin of Re-Biotin making Re-Biotin far away from MPS-PPV. Avidin or strptavidin as re-Biotin probe can not only be quantitatively determinated, but also be identified.

Chen, Yanguo; Hong, Peng; Xu, Baoming; He, Zhike; Zhou, Baohan

2014-03-01

269

A ratiometric fluorescent probe for gasotransmitter hydrogen sulfide based on a coumarin-benzopyrylium platform.  

PubMed

A ratiometric fluorescent probe for H2S was developed based on a coumarin- benzopyrylium platform. The ratiometric sensing is realized by a selective conversion of acyl azide to the corresponding amide, which subsequently undergoes an intramolecular spirocyclization to alter the large ?-conjugated system of CB fluorophore. Compared with the traditional azide-based H2S probes, the proposed probe utilizes the acyl azide as the recognition moiety and exhibits a rapid response (?1min) towards H2S, which is superior to most of the azide-based H2S probes. Preliminary fluorescence imaging experiments show that probe 1 has potential to track H2S in living cells. PMID:25622606

Duan, Yu-Wei; Yang, Xiao-Feng; Zhong, Yaogang; Guo, Yuan; Li, Zheng; Li, Hua

2015-02-15

270

A fast reconstruction algorithm for fluorescence optical diffusion tomography based on preiteration.  

PubMed

Fluorescence optical diffusion tomography in the near-infrared (NIR) bandwidth is considered to be one of the most promising ways for noninvasive molecular-based imaging. Many reconstructive approaches to it utilize iterative methods for data inversion. However, they are time-consuming and they are far from meeting the real-time imaging demands. In this work, a fast preiteration algorithm based on the generalized inverse matrix is proposed. This method needs only one step of matrix-vector multiplication online, by pushing the iteration process to be executed offline. In the preiteration process, the second-order iterative format is employed to exponentially accelerate the convergence. Simulations based on an analytical diffusion model show that the distribution of fluorescent yield can be well estimated by this algorithm and the reconstructed speed is remarkably increased. PMID:18253470

Song, Xiaolei; Xiong, Xiaoyun; Bai, Jing

2007-01-01

271

Experimental determination of photostability and fluorescence-based detection of PAHs on the Martian surface  

NASA Astrophysics Data System (ADS)

Even in the absence of any biosphere on Mars, organic molecules, including polycyclic aromatic hydrocarbons (PAHs), are expected on its surface due to delivery by comets and meteorites of extraterrestrial organics synthesized by astrochemistry, or perhaps in situ synthesis in ancient prebiotic chemistry. Any organic compounds exposed to the unfiltered solar ultraviolet spectrum or oxidizing surface conditions would have been readily destroyed, but discoverable caches of Martian organics may remain shielded in the subsurface or within surface rocks. We have studied the stability of three representative polycyclic aromatic hydrocarbons (PAHs) in a Mars chamber, emulating the ultraviolet spectrum of unfiltered sunlight under temperature and pressure conditions of the Martian surface. Fluorescence spectroscopy is used as a sensitive indicator of remaining PAH concentration for laboratory quantification of molecular degradation rates once exposed on the Martian surface. Fluorescence-based instrumentation has also been proposed as an effective surveying method for prebiotic organics on the Martian surface. We find the representative PAHs, anthracene, pyrene, and perylene, to have persistence half-lives once exposed on the Martian surface of between 25 and 60 h of noontime summer UV irradiation, as measured by fluorescence at their peak excitation wavelength. This equates to between 4 and 9.6 sols when the diurnal cycle of UV light intensity on the Martian surface is taken into account, giving a substantial window of opportunity for detection of organic fluorescence before photodegradation. This study thus supports the use of fluorescence-based instrumentation for surveying recently exposed material (such as from cores or drill tailings) for native Martian organic molecules in rover missions.

Dartnell, Lewis R.; Patel, Manish R.; Storrie-Lombardi, Michael C.; Ward, John M.; Muller, Jan-Peter

2012-05-01

272

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. PMID:20798932

Li, Ji; Wang, Zhuying; Gryczynski, Ignacy

2010-01-01

273

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

274

Fluorescence-lifetime-based determination of anions using a site-directed mutant enzyme transducer  

NASA Astrophysics Data System (ADS)

In comparison to metal ions in aqueous solutions, there are few methods for analysis of small anions such as cyanide, cyanate, carbonate, sulfide, and nitrate. Yet such analytes are important as environmental pollutants and as reagents and byproducts of industrial processes, paper manufacture, and mining. For some time we have been developing fluorescence-based fiber optic biosensors for metal ions such as zinc, cobalt, copper, mercury, nickel and cadmium, using the unparalleled selectivity and avidity of a metalloenzyme, human carbonic anhydrase. In the cases of Cu2+, CO2+, and Ni2+, we made use of the characteristic weak d-d absorbance bands of these metals when bound in the active site of the enzyme to serve as a fluorescence energy transfer acceptor for a suitably positioned fluorescent label attached to the enzyme. For this approach the intensity and lifetime of the fluorophore reflect the degree of energy transfer, and therefore the concentration of the metal. To measure certain anions such as cyanide and cyanate, we made use of the well-known perturbation of the d-d absorbance of Co2+ when an anion inhibitor becomes bound and inhibits the enzyme. These changes in absorbance modify the overlap integral with a suitable fluorescent label, and thereby the degree of energy transfer, resulting in a perturbation of the intensity and lifetime.

Thompson, Richard B.; Lin, Hai-Jui; Ge, Zhengfang; Johnson, Kelly; Fierke, Carol A.

1997-05-01

275

[Study of screening nephroprotective bioactive substances based on triple-color fluorescence probes in Carthami flos].  

PubMed

In this study, an approach based on triple-color fluorescence probes was developed for screening potential nephro-protective bioactive substances. Three fluorescent probes (i. e. FDA, MTR and Hoechst 33342) were used to label HK-2 cells injured by doxorubicin hydrochloride, and cellular fluorescence images were subsequently acquired and analyzed by a cellular-fluorescence image microscopy platform. The established method was applied to screening 53 components of Carthami Flos, and three components C17, C18 and C19 were found to exhibit nephroprotective effects against doxorubicin hydrochloride induced injury on HK-2 cells. Eight compounds (i. e. hydroxysafflor yellow A, 6-hydroxykaempferol-3-O-rutinoside-6-O-glucoside, 6-hydroxykaempferol-3,6-di-O-gluco-side or 6-hydroxykaempferol-6, 7-di-O-glucoside, 6-hydroxykaempferol-3-O-rutinoside, 6-hydroxykaempferol-3-O-glucoside or 6-hydroxykaempferol-7-O-glucoside, rutin, isoquercetin, and kaempferol-3-O-rutinoside) in components C17, C18 and C19 were preliminarily identified by liquid chromatography-mass spectrometry (LC-MS). Isoquercetin, rutin, kaempferol-3-O-rutinoside, and hydroxysafflor yellow A were confirmed by comparing with reference substances, Further study indicated that these four compounds had moderate nephroprotective effects, while isoquercetin showed a significant nephroprotective effect in a dose-dependent manner. These results suggest that isoquercetin, rutin, kaempferol-3-O-rutinoside and hydroxysafflor yellow A might be the nephroprotective bioactive substances in Carthami Flos. PMID:25282899

Lan, Xiao-Hong; Xiao, Shun; Gong, Wan; Wang, Yi; Zhao, Xiao-Ping

2014-05-01

276

A novel label-free fluorescent sensor for the detection of potassium ion based on DNAzyme.  

PubMed

A novel label-free and sensitive fluorescent aptasensor for the detection of potassium ion (K(+)) was developed based on the horseradish peroxidase-mimicking DNAzyme (HRP-DNAzyme). In this work, we selected a K(+)-stabilized single stranded DNA (ssDNA) with G-rich sequence as the recognition element. In the presence of K(+), the G-rich DNA folded into the G-quadruplex structure, and then hemin can bind to the G-quadruplex structure as a co-factor and form HRP-DNAzyme. 3-(p-Hydroxyphenyl)-propanoic acid (HPPA) can be oxidized by H(2)O(2) into a fluorescent product in the presence of DNAzyme. The fluorescence intensity of the HPPA oxidative product increased with the K(+) concentration. Under the optimal conditions, the fluorescence intensity was linearly related to the logarithm of K(+) concentration in the range of 2.5 ?M to 5mM. Other metal ions, such as Na(+), Li(+), NH(4)(+), Mg(2+) and Ca(2+) caused no notable interference on the detection of K(+). PMID:22284459

Fan, Xiaoyu; Li, Haitao; Zhao, Jie; Lin, Fanbo; Zhang, Lingli; Zhang, Youyu; Yao, Shouzhuo

2012-01-30

277

Molecular imaging based on x-ray fluorescent high-Z tracers  

NASA Astrophysics Data System (ADS)

We propose a novel x-ray fluorescence imaging setup for the in vivo detection of high-Z tracer distributions. The main novel aspect is the use of an analyzer-based, energy-resolved detection method together with a radial, scatter reducing collimator. The aim of this work is to show the feasibility of this method by measuring the Bragg reflected K-fluorescence signal of an iodine solution sample in a proof of principle experiment and to estimate the potential of the complete imaging setup using a Monte Carlo simulation, including a quantification of the minimal detectable tracer concentration for in vivo imaging. The proof of principle experiment shows that even for a small detector area of approximately 7 mm2, the collimated and Bragg reflected K-fluorescence signal of a sample containing an iodine solution with a concentration of 50 µg?ml-1 can be detected. The Monte Carlo simulation also shows that the proposed x-ray fluorescence imaging setup has the potential to image distributions of high-Z tracers in vivo at a radiation dose of a few mGy and at tracer concentrations down to 1 µg?ml-1 for iodine in small animals.

Müller, Bernhard H.; Hoeschen, Christoph; Grüner, Florian; Arkadiev, Vladimir A.; Johnson, Thorsten R. C.

2013-11-01

278

Intrinsic Fluorescence-Based Optical Fiber Sensor for Cocaine Using a Molecularly Imprinted Polymer as the Recognition Element  

Microsoft Academic Search

A fiber-optic chemical sensor for the detection of cocaine has been developed, based on a molecularly imprinted polymer (MIP) containing a fluorescein moiety as the signalling group. The fluorescent MIP was formed and covalently attached to the distal end of an optical fiber. The sensor exhibited an increase in fluorescence intensity in response to cocaine in the concentra- tion range

T. Hien Nguyen; Sheila A. Hardwick; Tong Sun; Kenneth T. V. Grattan

2012-01-01

279

Sensitive fluorescence-based method for the rapid determination of polysorbate-80 content in therapeutic monoclonal antibody products.  

PubMed

Abstract A sensitive and effective method has been developed for the rapid determination of polysorbate-80 content in therapeutic monoclonal antibody (mAb) products. The method is based on the detection of the fluorescence emission of 4,4'-dianilino-1,1'-binaphthyl-5,5'-disulfonic acid dipotassium salt (bis-ANS) enhanced by the presence of polysorbate-80. The developed method includes two approaches. One requires removal of the mAb from solution prior to analysis, while the other requires only simple sample dilution. The limits of detection and quantitation, calculated from the calibration curve generated in the absence of mAb-A, were 1.5 and 4.7 parts per million, respectively. Given the comparable linear range and linearity of the linear line between the solutions, with or without mAb, the limit of detection and quantitation is assumed to be similar. The dilution method is not only fast and simple in terms of sample preparation, but it is also particularly useful for analyzing the level of polysorbate-80 contained in highly concentrated mAb products. However, given that this method does require availability of polysorbate-80-free materials of mAb for preparation of calibration standards, the protein removal method may be useful for the cases where appropriate protein materials for standard preparation are limited or unavailable. PMID:24946793

Zheng, Songyan; Smith, Pedro; Burton, Lori; Adams, Monica L

2014-06-20

280

A Study of WebBased SNMP Network Management with a Simple Java Applet Network Monitoring Tool  

E-print Network

A Study of Web­Based SNMP Network Management with a Simple Java Applet Network Monitoring Tool . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2. Simple Network Management Protocol (SNMP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2.1 SNMP Model

281

A novel Schiff-base as a Cu(II) ion fluorescent sensor in aqueous solution  

NASA Astrophysics Data System (ADS)

A new fluorescent Cu(II) sensor (L) obtained from the Schiff base of 5,5?-methylene-bis-salicylaldehyde with amidol (2,4-diaminophenol) was synthesized and characterized by FT-IR, MS, 1H NMR, 13C NMR techniques. In the presence of pH 6.5 (KHPO4-Na2HPO4) buffer solutions, copper reacted with L to form a stable 2:1 complex. Fluorescence spectroscopic study showed that Schiff base is highly sensitive towards Cu(II) over other metal ions (K+, Na+, Al3+, Ni2+, Co2+, Fe3+, Zn2+, Pb2+) in DMSO/H2O (30%, v/v). The sensor L was successfully applied to the determination of copper in standard reference material. The structural properties and molecular orbitals of the complex formed between L and Cu2+ ions were also investigated using quantum chemical computations.

Gündüz, Z. Yurtman; Gündüz, C.; Özp?nar, C.; Urucu, O. Ayd?n

2015-02-01

282

A dinuclear cadmium(II) Schiff base thiocyanato complex: crystal structure and fluorescence.  

PubMed

A new dinuclear cadmium(II) complex, [Cd(L)(NCS)]2 (1) has been synthesized using a potentially tetradentate Schiff base ligand HL, 2-((E)-(2-(diethylamino)ethylimino)methyl)-6-methoxyphenol, obtained by the condensation of 2-diethylaminoethylamine and o-vanillin, and characterized by different physicochemical techniques. Crystal structure of the title complex was unambiguously established by single crystal X-ray diffraction which reveals that metal centers are connected by bridging phenolato and chelating methoxy oxygen atoms of the coordinating Schiff bases and embedded in severely distorted octahedral geometries. Fluorescence properties of the ligand and its complex, studied at room temperature indicate that later may serve as strong fluorescent emitter. PMID:24664327

Shit, Shyamapada; Sankolli, Ravish; Guru Row, Tayur N

2014-01-01

283

Photocured thiol-ene based optical fluorescence sensor for determination of gold(III).  

PubMed

This study describes the preparation and the characterization of a new thiol-ene based polymeric fluorescence sensor by photo initiated polymerization of trimethylolpropane tris(3-mercaptopropionate), 2-hydroxyethylacrylate, and 2,4,6-triallyloxy-1,3,5-triazine which are used as monomers and also a photo initiator (2,2-dimethoxy-2-phenylacetophenone) for its usage as optical sensor for gold ions. The thiol-ene based polymeric membrane sensor was characterized by using attenuated total reflectance-fourier transform infrared spectroscopy (ATR-FTIR) and scanning electron microscopy (SEM). The response characteristics of the sensors including dynamic range, pH effect, response time, and the effect of foreign ions were investigated. Fluorescence spectra showed that the excitation/emission maxima of the membrane were at 379/425 nm, respectively. PMID:24491784

Cubuk, Soner; Kahraman, Memet Vezir; Yetimo?lu, Ece Kök; Kenan, Sibel

2014-02-17

284

Triazole-based Zn²?-specific molecular marker for fluorescence bioimaging.  

PubMed

Fluorescence bioimaging potential, both in vitro and in vivo, of a yellow emissive triazole-based molecular marker has been investigated and demonstrated. Three different kinds of cells, viz Bacillus thuringiensis, Candida albicans, and Techoma stans pollen grains were used to investigate the intracellular zinc imaging potential of 1 (in vitro studies). Fluorescence imaging of translocation of zinc through the stem of small herb, Peperomia pellucida, having transparent stem proved in vivo bioimaging capability of 1. This approach will enable in screening cell permeability and biostability of a newly developed probe. Similarly, the current method for detection and localization of zinc in Gram seed sprouts could be an easy and potential alternative of the existing analytical methods to investigate the efficiency of various strategies applied for increasing zinc-content in cereal crops. The probe-zinc ensemble has efficiently been applied for detecting phosphate-based biomolecules. PMID:24725748

Sinha, Sougata; Mukherjee, Trinetra; Mathew, Jomon; Mukhopadhyay, Subhra K; Ghosh, Subrata

2014-04-25

285

A highly selective turn on fluorescence sensor for Hg2+ based on rhodamine derivative.  

PubMed

A novel fluorescent rhodamine based chemosensor (E)-3',6'-bis(diethylamino)-2-((2-(pyridin-2-ylmethoxy)benzylidene)amino)spiro[isoindoline-1,9'-xanthen]-3-one, RSP, had been successfully developed and well characterized by NMR, FT-IR and Mass spectroscopy. The chemosensor exhibits high selectivity for Hg(2+) over other ions (Ag(+), Pb(2+), Cu(2+), Ni(2+), Fe(3+), Co(2+), Zn(2+) and Cd(2+)) with fluorescence enhancement in ethanol solution. More over the detection limit of the sensor is in the 10(-6) M level. The binding ratio of RSP-Hg(2+) complex was determined to be 1:1 according to the Job plot. Test strips based on RSP were fabricated, which showed the application of the sensor for detection of mercuric ions in water by naked eyes. PMID:25082208

Li, LianQing; Yuan, Li; Liu, ZhiHong

2014-09-01

286

Aerial Imaging of Fluorescent Dye in the Near Shore DAVID B. CLARK  

E-print Network

measurements are costly and complex, and few fluorescent dye studies have been conducted in turbid nearshore waters. Passive aerial imaging of solar stimulated fluorescence offers a relatively simple, low) in the nearshore zone have not been described. Here we develop simple airborne-based optical methods for measuring

Boss, Emmanuel S.

287

Phase-sensitive flow cytometry: fluorescence lifetime-based sensing technology for analyzing free fluorophore and cells/particles labeled with fluorescent probes  

NASA Astrophysics Data System (ADS)

A phase-sensitive cytometer has been developed that combines flow cytometry and fluorescence lifetime spectroscopy measurement principles to provide unique features for making frequency-domain lifetime measurements on free fluorophore (solution) and on fluorophore-labeled cells/particles in real time. No other instrument can quantify lifetimes directly and resolve heterogeneous fluorescence based on differences in lifetimes (expressed as phase shifts), while maintaining the capability to make conventional flow cytometric measurements. The technology has been characterized with respect to measurement precision, linearity, sensitivity, and dynamic range. Fluorescence lifetime distributions have been measured on autofluorescence lung cells, thymocytes labeled with antibody conjugated to fluorophores for studying fluorescence quenching as a function of antibody dilution and F/P ratio, cells stained with DNA-binding fluorochromes, and on particles labeled with fluorophores and free fluorophore (solution). Phase-resolved, fluorescence signal- intensity histograms have been recorded on thymocytes labeled with a phycoerythrin/Texas Red tandem conjugate and propidium iodide to demonstrate the resolution of signals from highly overlapping emission spectra. This technology adds a new dimension to flow analyses of free and cell/particle-bound fluorophore. 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.

1999-12-01

288

A highly sensitive and selective fluorescent chemosensor for detection of Zn(2+) based on a Schiff base.  

PubMed

A Schiff-base fluorescent probe - 2-((E)-(quinolin-8-ylimino)methyl)quinolin-8-ol (H7L) was synthesized and evaluated as a chemoselective Zn(2+) sensor. Upon treatment with Zn(2+), the complexation of H7L with Zn(2+) resulted in a red shift with a pronounced enhancement in the fluorescence emission intensity in ethanol solution. Moreover, other common alkali, alkaline earth and transition metal ions failed to induce response or minimal spectral changes. Notably, this chemosensor could distinguish clearly Zn(2+) from Cd(2+). Fluorescence studies on H7L and H7L-Zn(2+) complex reveal that the quantum yield strongly increases upon coordination. The stoichiometric ratio and association constant were evaluated using Benesi-Hildebrand relation giving 1:1 stoichiometry. This further corroborated 1:1 complex formation based on Job's plot analyses. This chemosensor exhibits a very good fluorescence sensing ability to Zn(2+) over a wide range of pH. PMID:25590829

Roy, Nayan; Pramanik, Harun A R; Paul, Pradip C; Singh, T Sanjoy

2015-04-01

289

Shape assisted fabrication of fluorescent cages of squarate based metal-organic coordination frameworks.  

PubMed

Micronic cage structures of squarate based metal-organic coordination frameworks (MOCFs) have been fabricated for the first time by specific anion selective etching of metal squarate cubes. Time and stoichiometry dependent synthesis and the corresponding microscopic studies have provided mechanistic insight into the cage formation. Furthermore, a non-covalent post-synthetic strategy has been adopted to functionalize the micronic cubes or cages with chromophores rendering the resulting hybrids green fluorescent. PMID:23435584

Jayaramulu, Kolleboyina; Krishna, Katla Sai; George, Subi J; Eswaramoorthy, Muthuswamy; Maji, Tapas Kumar

2013-05-11

290

AlGaN-based deep-UV LEDs for fluorescence sensing  

Microsoft Academic Search

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

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

2004-01-01

291

Fluorescence determination of metoprolol in human plasma by trilinear decomposition-based calibration techniques  

Microsoft Academic Search

In this study a new spectrofluorimetric method for the direct determination of metoprolol in human plasma is presented and\\u000a discussed. It is based on the use of fluorescence excitation–emission matrices (EEMs) and second-order calibration performed\\u000a with parallel factor analysis (PARAFAC) or alternating trilinear decomposition (ATLD). This methodology enables accurate and\\u000a reliable discrimination of the analyte signal, even in the presence

Yan Zhang; Hai-Long Wu; A-Lin Xia; Shao-Hua Zhu; Qing-Juan Han; Ru-Qin Yu

2006-01-01

292

Bay functionalized perylenediimide as a deaggregation based intracellular fluorescent probe for perchlorate.  

PubMed

The aggregates of perylenediimide based chemosensor (PDI 1) undergo de-aggregation induced fluorescence quenching selectively with ClO4(-) ions both in the solution and in the solid phase and can detect ClO4(-) ions in drinking water and fireworks. PDI 1 is permeable to C6 glioma cells, and ClO4(-) can be detected using confocal microscopy. PMID:25266857

Singh, Prabhpreet; Mittal, Lalit Singh; Vanita, Vanita; Kumar, Rahul; Bhargava, Gaurav; Walia, Amandeep; Kumar, Subodh

2014-11-21

293

Simple Identity-Based Cryptography with Mediated Xuhua Ding and Gene Tsudik  

E-print Network

with identity-based cryptography. Mediated RSA (mRSA) [9] is a simple and practical method of splitting a RSA another since each cryptographic operation (signature or decryption) involves both parties. mRSA allows fast and fine-grained control of users' security privileges. However, mRSA still relies on conventional

Ding, Xuhua

294

Two Simple Classroom Demonstrations for Scanning Probe Microscopy Based on a Macroscopic Analogy  

ERIC Educational Resources Information Center

This article describes two simple classroom demonstrations that illustrate the principles of scanning probe microscopy (SPM) based on a macroscopic analogy. The analogy features the bumps in an egg carton to represent the atoms on a chemical surface and a probe that can be represented by a dwarf statue (illustrating an origin of the prefix…

Hajkova, Zdenka; Fejfar, Antonin; Smejkal, Petr

2013-01-01

295

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

296

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

297

A Cognitively Based Simulation of Simple Organizations Ron Sun (rsun@rpi.edu)  

E-print Network

that better mod- els of individual cognition can lead us to a better un- derstanding of aggregate processes, conceptual processes). Therefore, the mecha- nisms underlying individual cognition cannot be ignoredA Cognitively Based Simulation of Simple Organizations Ron Sun (rsun@rpi.edu) Isaac Naveh

Varela, Carlos

298

Wordnet creation and extension made simple: A multilingual lexicon-based approach using wiki resources  

E-print Network

Wordnet creation and extension made simple: A multilingual lexicon-based approach using wiki be a way to mitigate the lack of wide coverage bilingual lexicon for wordnet creation or extension. We wordnet creation and extension has become a field of interest. Many methods have been developed

Paris-Sud XI, Université de

299

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

2014-08-25

300

Density functional calculations on simple carbonyl bases: protonation and hydrogen bond formation with water  

E-print Network

Density functional calculations on simple carbonyl bases: protonation and hydrogen bond formation than for hydrogen bond formation. The hydrogen bond energies are linearly correlated to the proton Hydrogen bonding is one of the most important intermolecular interaction, and its strength has been

Nguyen, Minh Tho

301

Simple mathematical mapping based meshing technique with application to antenna simulations  

Microsoft Academic Search

A simple meshing technique, based on mathematical mapping, is introduced. In this technique, a basic unit, such as a rectangular plate or a circular plate, is generated using triangular patches; then it is mapped into a specified surface using a mathematical formula. In this way, any closed or open cylinder can easily be generated by the rectangular plate and any

Yunhua Zhang

2004-01-01

302

A Simple Stand Growth Model Based on Canopy Dynamics and Biomechanics  

E-print Network

A Simple Stand Growth Model Based on Canopy Dynamics and Biomechanics Thomas J. Dean, Mauricio be expressed in terms of wind drag. From this point of view, biomechanical principles determine the stem cross in a developing stand, biomechanics create a conceptual framework for predicting aboveground stem production

Cao, Quang V.

303

A simple birth-death-migration individual-based model for biofilm development  

E-print Network

A simple birth-death-migration individual-based model for biofilm development Nabil Mabrouk only three main processes: birth (binary fission), death (or detachment) and surface migration in time due to three stochastic events acting on the individuals: · birth of a new bacterium · detachment

Paris-Sud XI, Université de

304

NOISE PROCESSING FOR SIMPLE LAPLACIAN PYRAMID SYNTHESIS BASED ON DUAL FRAME RECONSTRUCTION  

E-print Network

NOISE PROCESSING FOR SIMPLE LAPLACIAN PYRAMID SYNTHESIS BASED ON DUAL FRAME RECONSTRUCTION Aditya, zakhary, mflierl, bgirod}@stanford.edu ABSTRACT The Laplacian pyramid (LP) provides a frame expansion processing at the encoder. Index Terms-- Laplacian pyramid, dual frame, framed pyra- mid. 1. INTRODUCTION

Girod, Bernd

305

Pancreatic tumor detection using hypericin-based fluorescence spectroscopy and cytology  

NASA Astrophysics Data System (ADS)

Hypericin is a novel, highly fluorescent photosensitizer that exhibits selective tumor cell uptake properties and is particularly resistant to photobleaching. In this study, we have characterized hypericin uptake in human pancreatic tumor cells with relation to incubation time, cell number, and drug concentration. Ex vivo hypericin based fluorescence spectroscopy was performed to detect the presence of MIA PaCa-2 pancreatic tumor cells in the peritoneal cavity of BALB/c nude mice, as well as to quantify gross tumor burden. Hypericin based cytology of peritoneal lavage samples, using both one and two photon laser confocal microscopy, demonstrated more than a two-fold increase in fluorescence emission of pancreatic tumor cells as compared to control samples. In vitro treatment of pancreatic cancer cells with hypericin based photodynamic therapy showed tumor cell cytotoxicity in a drug dose, incident laser power, and time dependent manner. For these experiments, a continuous wavelength solid-state laser source (532 nm) was operated at power levels in the range of 100-400 mW. Potential applications of hypericin in tumor diagnosis, staging, and therapy will be presented.

Lavu, Harish; Geary, Kevin; Fetterman, Harold R.; Saxton, Romaine E.

2005-04-01

306

Modelling of diffraction grating based optical filters for fluorescence detection of biomolecules.  

PubMed

The detection of biomolecules based on fluorescence measurements is a powerful diagnostic tool for the acquisition of genetic, proteomic and cellular information. One key performance limiting factor remains the integrated optical filter, which is designed to reject strong excitation light while transmitting weak emission (fluorescent) light to the photodetector. Conventional filters have several disadvantages. For instance absorbing filters, like those made from amorphous silicon carbide, exhibit low rejection ratios, especially in the case of small Stokes' shift fluorophores (e.g. green fluorescent protein GFP with ? exc = 480 nm and ? em = 510 nm), whereas interference filters comprising many layers require complex fabrication. This paper describes an alternative solution based on dielectric diffraction gratings. These filters are not only highly efficient but require a smaller number of manufacturing steps. Using FEM-based optical modelling as a design optimization tool, three filtering concepts are explored: (i) a diffraction grating fabricated on the surface of an absorbing filter, (ii) a diffraction grating embedded in a host material with a low refractive index, and (iii) a combination of an embedded grating and an absorbing filter. Both concepts involving an embedded grating show high rejection ratios (over 100,000) for the case of GFP, but also high sensitivity to manufacturing errors and variations in the incident angle of the excitation light. Despite this, simulations show that a 60 times improvement in the rejection ratio relative to a conventional flat absorbing filter can be obtained using an optimized embedded diffraction grating fabricated on top of an absorbing filter. PMID:25071964

Kova?i?, M; Kr?, J; Lipovšek, B; Topi?, M

2014-07-01

307

When Simple Harmonic Motion Is Not that Simple: Managing Epistemological Complexity by Using Computer-Based Representations  

ERIC Educational Resources Information Center

Many real-world phenomena, even "simple" physical phenomena such as natural harmonic motion, are complex in the sense that they require coordinating multiple subtle foci of attention to get the required information when experiencing them. Moreover, for students to develop sound understanding of a concept or a phenomenon, they need to learn to get…

Parnafes, Orit

2010-01-01

308

[Remote sensing of chlorophyll fluorescence at airborne level based on unmanned airship platform and hyperspectral sensor].  

PubMed

The solar-induced chlorophyll fluorescence (ChlF) has a close relationship with photosynthetic and is considered as a probe of plant photosynthetic activity. In this study, an airborne fluorescence detecting system was constructed by using a hyperspectral imager on board an unmanned airship. Both Fraunhofer Line Discriminator (FLD) and 3FLD used to extract ChlF require the incident solar irradiance, which is always difficult to receive at airborne level. Alternative FLD (aFLD) can overcome the problem by selecting non-fluorescent emitter in the image. However, aFLD is based on the assumption that reflectance is identical around the Fraunhofer line, which is not realistic. A new method, a3FLD, is proposed, which assumes that reflectance varies linearly with the wavelength around Fraunhofer line. The result of simulated data shows that ChlF retrieval error of a3FLD is significantly lower than that of aFLD when vegetation reflectance varies near the Fraunhofer line. The results of hyperspectral remote sensing data with the airborne fluorescence detecting system show that the relative values of retrieved ChlF of 5 kinds of plants extracted by both aFLD and a3FLD are consistent with vegetation growth stage and the ground-level ChlF. The ChlF values of aFLD are about 15% greater than a3FLD. In addition, using aFLD, some non-fluorescent objects have considerable ChlF value, while a3FLD can effectively overcome the problem. PMID:24555390

Yang, Pei-Qi; Liu, Zhi-Gang; Ni, Zhuo-Ya; Wang, Ran; Wang, Qing-Shan

2013-11-01

309

Free-space fluorescence tomography with adaptive sampling based on anatomical information from microCT  

NASA Astrophysics Data System (ADS)

Image reconstruction is one of the main challenges for fluorescence tomography. For in vivo experiments on small animals, in particular, the inhomogeneous optical properties and irregular surface of the animal make free-space image reconstruction challenging because of the difficulties in accurately modeling the forward problem and the finite dynamic range of the photodetector. These two factors are fundamentally limited by the currently available forward models and photonic technologies. Nonetheless, both limitations can be significantly eased using a signal processing approach. We have recently constructed a free-space panoramic fluorescence diffuse optical tomography system to take advantage of co-registered microCT data acquired from the same animal. In this article, we present a data processing strategy that adaptively selects the optical sampling points in the raw 2-D fluorescent CCD images. Specifically, the general sampling area and sampling density are initially specified to create a set of potential sampling points sufficient to cover the region of interest. Based on 3-D anatomical information from the microCT and the fluorescent CCD images, data points are excluded from the set when they are located in an area where either the forward model is known to be problematic (e.g., large wrinkles on the skin) or where the signal is unreliable (e.g., saturated or low signal-to-noise ratio). Parallel Monte Carlo software was implemented to compute the sensitivity function for image reconstruction. Animal experiments were conducted on a mouse cadaver with an artificial fluorescent inclusion. Compared to our previous results using a finite element method, the newly developed parallel Monte Carlo software and the adaptive sampling strategy produced favorable reconstruction results.

Zhang, Xiaofeng; Badea, Cristian T.; Hood, Greg; Wetzel, Arthur W.; Stiles, Joel R.; Johnson, G. Allan

2010-02-01

310

Free-space fluorescence tomography with adaptive sampling based on anatomical information from microCT  

PubMed Central

Image reconstruction is one of the main challenges for fluorescence tomography. For in vivo experiments on small animals, in particular, the inhomogeneous optical properties and irregular surface of the animal make free-space image reconstruction challenging because of the difficulties in accurately modeling the forward problem and the finite dynamic range of the photodetector. These two factors are fundamentally limited by the currently available forward models and photonic technologies. Nonetheless, both limitations can be significantly eased using a signal processing approach. We have recently constructed a free-space panoramic fluorescence diffuse optical tomography system to take advantage of co-registered microCT data acquired from the same animal. In this article, we present a data processing strategy that adaptively selects the optical sampling points in the raw 2-D fluorescent CCD images. Specifically, the general sampling area and sampling density are initially specified to create a set of potential sampling points sufficient to cover the region of interest. Based on 3-D anatomical information from the microCT and the fluorescent CCD images, data points are excluded from the set when they are located in an area where either the forward model is known to be problematic (e.g., large wrinkles on the skin) or where the signal is unreliable (e.g., saturated or low signal-to-noise ratio). Parallel Monte Carlo software was implemented to compute the sensitivity function for image reconstruction. Animal experiments were conducted on a mouse cadaver with an artificial fluorescent inclusion. Compared to our previous results using a finite element method, the newly developed parallel Monte Carlo software and the adaptive sampling strategy produced favorable reconstruction results. PMID:21743784

Badea, Cristian T.; Hood, Greg; Wetzel, Arthur W.; Stiles, Joel R.; Johnson, G. Allan

2011-01-01

311

Free-space fluorescence tomography with adaptive sampling based on anatomical information from microCT.  

PubMed

Image reconstruction is one of the main challenges for fluorescence tomography. For in vivo experiments on small animals, in particular, the inhomogeneous optical properties and irregular surface of the animal make free-space image reconstruction challenging because of the difficulties in accurately modeling the forward problem and the finite dynamic range of the photodetector. These two factors are fundamentally limited by the currently available forward models and photonic technologies. Nonetheless, both limitations can be significantly eased using a signal processing approach. We have recently constructed a free-space panoramic fluorescence diffuse optical tomography system to take advantage of co-registered microCT data acquired from the same animal. In this article, we present a data processing strategy that adaptively selects the optical sampling points in the raw 2-D fluorescent CCD images. Specifically, the general sampling area and sampling density are initially specified to create a set of potential sampling points sufficient to cover the region of interest. Based on 3-D anatomical information from the microCT and the fluorescent CCD images, data points are excluded from the set when they are located in an area where either the forward model is known to be problematic (e.g., large wrinkles on the skin) or where the signal is unreliable (e.g., saturated or low signal-to-noise ratio). Parallel Monte Carlo software was implemented to compute the sensitivity function for image reconstruction. Animal experiments were conducted on a mouse cadaver with an artificial fluorescent inclusion. Compared to our previous results using a finite element method, the newly developed parallel Monte Carlo software and the adaptive sampling strategy produced favorable reconstruction results. PMID:21743784

Zhang, Xiaofeng; Badea, Cristian T; Hood, Greg; Wetzel, Arthur W; Stiles, Joel R; Johnson, G Allan

2010-01-01

312

A sensitive and selective chemosensor for ascorbic acid based on a fluorescent nitroxide switch.  

PubMed

Ascorbic acid (AsA), also known as vitamin C, is a vital small-molecule antioxidant with multiple functions in vivo. It's the major natural antioxidant found in plants and is also an essential component of human nutrition. AsA plays a key role in many diseases-related biological metabolism. Therefore, sensitive and selective detection of AsA is greatly important in pharmaceutical, clinical and food industry. Here a sensitive and selective sensor for ascorbic acid detection based on the recovered fluorescence of NAPS-NO (N-propyl-triethoxysilane-4-(4-ylamino-1-oxy-2,2,6,6-tetramethylpiperdine)- naphthalimide) probe is described. The fluorescence of the naphthalimide moiety of NAPS-NO is inhibited by the nitroxide group, which is covalently linked to the fluorophore. Then, ascorbic acid reacts rapidly with the nitroxide moiety of NAPS-NO to form hydroxylamine, and the fluorescence properties of the naphthalimide moiety are recovered and the ESR signal decayed. Over a wide range from 80nM to 50?M, a good linear relationship between the fluorescence intensity and the concentration of ascorbic acid was found and the detection limit was estimated to be as low as 20nM. To confirm the practical usefulness of the fluorophore-nitroxide probe, we demonstrated the use of NAPS-NO for the measurement of AsA in human blood serum and also successfully determined the concentration of AsA in HEK 293 cell lysate. Results from confocal laser scanning microscopy experiments demonstrated that this chemosensor is cell permeable and can be used as a fluorescent probe for monitoring ascorbic acid in living cells. PMID:25476297

Yang, Tian; Zheng, Baozhan; Liang, Hengxing; Wan, Yuping; Du, Juan; Xiao, Dan

2015-01-15

313

A new fluorescent chemosensor for Al(3+) ion based on schiff base naphthalene derivatives.  

PubMed

A new naphthalene derivative receptor (H2L) was synthesized. The chemosensor (H2L) exhibited a strong fluorescence enhancement in the presence of trace amounts of Al(3+), attributable to chelation-enhanced fluorescence (CHEF) effect, which also displayed high selectivity over a series of other metal cations (Na(+), K(+), Cs(+), Mg(2+), Ba(2+), Pb(2+), Cr(3+), Mn(2+), Fe(3+), Fe(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), Hg(2+) and Ag(+)) in ethanol. PMID:24650877

Azadbakht, Reza; Rashidi, Somaye

2014-06-01

314

Fluorescence Intensity- and Lifetime-Based Glucose Sensing Using Glucose/Galactose-Binding Protein  

PubMed Central

We review progress in our laboratories toward developing in vivo glucose sensors for diabetes that are based on fluorescence labeling of glucose/galactose-binding protein. Measurement strategies have included both monitoring glucose-induced changes in fluorescence resonance energy transfer and labeling with the environmentally sensitive fluorophore, badan. Measuring fluorescence lifetime rather than intensity has particular potential advantages for in vivo sensing. A prototype fiber-optic-based glucose sensor using this technology is being tested.Fluorescence technique is one of the major solutions for achieving the continuous and noninvasive glucose sensor for diabetes. In this article, a highly sensitive nanostructured sensor is developed to detect extremely small amounts of aqueous glucose by applying fluorescence energy transfer (FRET). A one-pot method is applied to produce the dextran-fluorescein isothiocyanate (FITC)-conjugating mesoporous silica nanoparticles (MSNs), which afterward interact with the tetramethylrhodamine isothiocyanate (TRITC)-labeled concanavalin A (Con A) to form the FRET nanoparticles (FITC-dextran-Con A-TRITC@MSNs). The nanostructured glucose sensor is then formed via the self-assembly of the FRET nanoparticles on a transparent, flexible, and biocompatible substrate, e.g., poly(dimethylsiloxane). Our results indicate the diameter of the MSNs is 60 ± 5 nm. The difference in the images before and after adding 20 ?l of glucose (0.10 mmol/liter) on the FRET sensor can be detected in less than 2 min by the laser confocal laser scanning microscope. The correlation between the ratio of fluorescence intensity, I(donor)/I(acceptor), of the FRET sensor and the concentration of aqueous glucose in the range of 0.04–4 mmol/liter has been investigated; a linear relationship is found. Furthermore, the durability of the nanostructured FRET sensor is evaluated for 5 days. In addition, the recorded images can be converted to digital images by obtaining the pixels from the resulting matrix using Matlab image processing functions. We have also studied the in vitro cytotoxicity of the device. The nanostructured FRET sensor may provide an alternative method to help patients manage the disease continuously. PMID:23439161

Pickup, John C.; Khan, Faaizah; Zhi, Zheng-Liang; Coulter, Jonathan; Birch, David J. S.

2013-01-01

315

A recombinant estrogen receptor fragment-based homogeneous fluorescent assay for rapid detection of estrogens.  

PubMed

In this work, we demonstrate a novel estrogenic receptor fragment-based homogeneous fluorescent assay which enables rapid and sensitive detection of 17?-estradiol (E2) and other highly potent estrogens. A modified human estrogenic receptor fragment (N-His × 6-hER270-595-C-Strep tag II) has been constructed that contains amino acids 270-595 of wild-type human estrogenic receptor ? (hER270-595) and two specific tags (6 × His and Strep tag II) fused to the N and C terminus, respectively. The designed receptor protein fragment could be easily produced by prokaryotic expression with high yield and high purity. The obtained protein exhibits high binding affinity to E2 and the two tags greatly facilitate the application of the recombinant protein. Taking advantage of the unique spectroscopic properties of coumestrol (CS), a fluorescent phytoestrogen, a CS/hER270-595-based fluorescent assay has been developed which can sensitively respond to E2 within 1.0 min with a linear working range from 0.1 to 20 ng/mL and a limit of detection of 0.1 ng/mL. The assay was successfully applied for rapid detection of E2 in the culture medium of rat hippocampal neurons. The method also holds great potential for high-throughput monitoring the variation of estrogen levels in complex biological fluids, which is crucial for investigation of the molecular basis of various estrogen-involved processes. PMID:24434499

Wang, Dan; Xie, Jiangbi; Zhu, Xiaocui; Li, Jinqiu; Zhao, Dongqin; Zhao, Meiping

2014-05-15

316

A small azide-modified thiazole-based reporter molecule for fluorescence and mass spectrometric detection  

PubMed Central

Summary Molecular probes are widely used tools in chemical biology that allow tracing of bioactive metabolites and selective labeling of proteins and other biomacromolecules. A common structural motif for such probes consists of a reporter that can be attached by copper(I)-catalyzed 1,2,3-triazole formation between terminal alkynes and azides to a reactive headgroup. Here we introduce the synthesis and application of the new thiazole-based, azide-tagged reporter 4-(3-azidopropoxy)-5-(4-bromophenyl)-2-(pyridin-2-yl)thiazole for fluorescence, UV and mass spectrometry (MS) detection. This small fluorescent reporter bears a bromine functionalization facilitating the automated data mining of electrospray ionization MS runs by monitoring for its characteristic isotope signature. We demonstrate the universal utility of the reporter for the detection of an alkyne-modified small molecule by LC–MS and for the visualization of a model protein by in-gel fluorescence. The novel probe advantageously compares with commercially available azide-modified fluorophores and a brominated one. The ease of synthesis, small size, stability, and the universal detection possibilities make it an ideal reporter for activity-based protein profiling and functional metabolic profiling. PMID:25383118

Wolfram, Stefanie; Würfel, Hendryk; Habenicht, Stefanie H; Lembke, Christine; Richter, Phillipp; Birckner, Eckhard; Beckert, Rainer

2014-01-01

317

Development of a QDots 800 based fluorescent solid phantom for validation of NIRF imaging platforms  

NASA Astrophysics Data System (ADS)

Over the past decade, we developed near-infrared fluorescence (NIRF) devices for non-invasive lymphatic imaging using microdosages of ICG in humans and for detection of lymph node metastasis in animal models mimicking metastatic human prostate cancer. To validate imaging, a NIST traceable phantom is needed so that developed "first-inhumans" drugs may be used with different luorescent imaging platforms. In this work, we developed a QDots 800 based fluorescent solid phantom for installation and operational qualification of clinical and preclinical, NIRF imaging devices. Due to its optical clearance, polyurethane was chosen as the base material. Titanium dioxide was used as the scattering agent because of its miscibility in polyurethane. QDots 800 was chosen owing to its stability and NIR emission spectra. A first phantom was constructed for evaluation of the noise floor arising from excitation light leakage, a phenomenon that can be minimized during engineering and design of fluorescent imaging systems. A second set of phantoms were constructed to enable quantification of device sensitivity associated with our preclinical and clinical devices. The phantoms have been successfully applied for installation and operational qualification of our preclinical and clinical devices. Assessment of excitation light leakage provides a figure of merit for "noise floor" and imaging sensitivity can be used to benchmark devices for specific imaging agents.

Zhu, Banghe; Sevick-Muraca, Eva M.

2013-02-01

318

A novel pyrene-based fluorescing amphiphile with unusual bulk and interfacial properties.  

PubMed

We have synthesised a new, pyrene-based, low-molecular-mass, amphiphilic molecule that displays a wealth of properties of potential interest for aggregation and interfacial applications. In order to elucidate some of the key properties of this molecule, which consists of a pyrene-containing hydrophobic head and a short PEG-based hydrophilic tail, we investigate herein some aspects of its concentration-dependent behaviour in aqueous solutions. We show that the inclusion of the hydrophobic pyrene group not only provides the molecule with intriguing bulk and interfacial properties down to low concentrations, but also with various means of assessing its aggregation behaviour by means of its well-characterised fluorescence properties. Combining a range of fluorescence techniques with microscopic imaging (optical and Cryo-TEM), interfacial tension measurements and foaming studies, we have been able to identify and characterise three concentration-dependant regimes. At low concentrations, the molecule is dissolved in monomeric form. At intermediate concentrations, labile aggregates are formed, which, at higher concentrations, give way to aggregates containing pre-associated pyrenes. Our measurements strongly imply that the latter aggregates are hexagonally close-packed tubular micelles. In this latter regime we also find a range of micron-sized precipitates. Additionally, the molecule displays strong interfacial activity, yet a surprisingly slow dynamics of interfacial adsorption. Finally, we demonstrate the possibility of using it to visualize interfaces and also create reasonably stable (1 hour) and fluorescing foams. PMID:21226196

Salonen, Anniina; Knyazev, Anton; von Bandel, Nicolas; Degrouard, Jéril; Langevin, Dominique; Drenckhan, Wiebke

2011-01-17

319

A fluorescent hydrogel-based flow cytometry high-throughput screening platform for hydrolytic enzymes.  

PubMed

Screening throughput is a key in directed evolution experiments and enzyme discovery. Here, we describe a high-throughput screening platform based on a coupled reaction of glucose oxidase and a hydrolase (Yersinia mollaretii phytase [YmPh]). The coupled reaction produces hydroxyl radicals through Fenton's reaction, acting as initiator of poly(ethyleneglycol)-acrylate-based polymerization incorporating a fluorescent monomer. As a consequence, a fluorescent hydrogel is formed around Escherichia coli cells expressing active YmPh. We achieve five times enrichment of active cell population through flow cytometry analysis and sorting of mixed populations. Finally, we validate the performance of the fluorescent polymer shell (fur-shell) technology by directed phytase evolution that yielded improved variants starting from a library containing 10(7) phytase variants. Thus, fur-shell technology represents a rapid and nonlaborious way of identifying the most active variants from vast populations, as well as a platform for generation of polymer-hybrid cells for biobased interactive materials. PMID:25525992

Pitzler, Christian; Wirtz, Georgette; Vojcic, Ljubica; Hiltl, Stephanie; Böker, Alexander; Martinez, Ronny; Schwaneberg, Ulrich

2014-12-18

320

A small azide-modified thiazole-based reporter molecule for fluorescence and mass spectrometric detection.  

PubMed

Molecular probes are widely used tools in chemical biology that allow tracing of bioactive metabolites and selective labeling of proteins and other biomacromolecules. A common structural motif for such probes consists of a reporter that can be attached by copper(I)-catalyzed 1,2,3-triazole formation between terminal alkynes and azides to a reactive headgroup. Here we introduce the synthesis and application of the new thiazole-based, azide-tagged reporter 4-(3-azidopropoxy)-5-(4-bromophenyl)-2-(pyridin-2-yl)thiazole for fluorescence, UV and mass spectrometry (MS) detection. This small fluorescent reporter bears a bromine functionalization facilitating the automated data mining of electrospray ionization MS runs by monitoring for its characteristic isotope signature. We demonstrate the universal utility of the reporter for the detection of an alkyne-modified small molecule by LC-MS and for the visualization of a model protein by in-gel fluorescence. The novel probe advantageously compares with commercially available azide-modified fluorophores and a brominated one. The ease of synthesis, small size, stability, and the universal detection possibilities make it an ideal reporter for activity-based protein profiling and functional metabolic profiling. PMID:25383118

Wolfram, Stefanie; Würfel, Hendryk; Habenicht, Stefanie H; Lembke, Christine; Richter, Phillipp; Birckner, Eckhard; Beckert, Rainer; Pohnert, Georg

2014-01-01

321

Local SIMPLE multi-atlas-based segmentation applied to lung lobe detection on chest CT  

NASA Astrophysics Data System (ADS)

For multi atlas-based segmentation approaches, a segmentation fusion scheme which considers local performance measures may be more accurate than a method which uses a global performance measure. We improve upon an existing segmentation fusion method called SIMPLE and extend it to be localized and suitable for multi-labeled segmentations. We demonstrate the algorithm performance on 23 CT scans of COPD patients using a leave-one- out experiment. Our algorithm performs significantly better (p < 0.01) than majority voting, STAPLE, and SIMPLE, with a median overlap of the fissure of 0.45, 0.48, 0.55 and 0.6 for majority voting, STAPLE, SIMPLE, and the proposed algorithm, respectively.

Agarwal, M.; Hendriks, E. A.; Stoel, B. C.; Bakker, M. E.; Reiber, J. H. C.; Staring, M.

2012-02-01

322

A LabVIEW-Based Virtual Instrument System for Laser-Induced Fluorescence Spectroscopy.  

PubMed

We report the design and operation of a Virtual Instrument (VI) system based on LabVIEW 2009 for laser-induced fluorescence experiments. This system achieves synchronous control of equipment and acquisition of real-time fluorescence data communicating with a single computer via GPIB, USB, RS232, and parallel ports. The reported VI system can also accomplish data display, saving, and analysis, and printing the results. The VI system performs sequences of operations automatically, and this system has been successfully applied to obtain the excitation and dispersion spectra of ?-methylnaphthalene. The reported VI system opens up new possibilities for researchers and increases the efficiency and precision of experiments. The design and operation of the VI system are described in detail in this paper, and the advantages that this system can provide are highlighted. PMID:22013388

Wu, Qijun; Wang, Lufei; Zu, Lily

2011-01-01

323

Protein A Detection Based on Quantum Dots-Antibody Bioprobe Using Fluorescence Coupled Capillary Electrophoresis  

PubMed Central

In this report, fluorescence detection coupled capillary electrophoresis (CE-FL) was used to detect Protein A. Antibody was first labeled with Cy5 and then mixed with quantum dots (QDs) to form QDs-antibody bioprobe. Further, we observed fluorescence resonance energy transfer (FRET) from QDs donor to Cy5 acceptor. The bioprobe was formed and brought QDs and Cy5 close enough to allow FRET to occur. After adding protein A, the FRET system was broken and caused the FRET signal to decrease. Thus, a new method for the determination of protein A was proposed based on the FRET signal changes. This study provides a new trail of thought for the detection of protein. PMID:24469315

Qiu, Lin; Bi, Yanhua; Wang, Cheli; Li, Jingyan; Guo, Peilin; Li, Jinchen; He, Weijiang; Wang, Jianhao; Jiang, Pengju

2014-01-01

324

Novel Highly Selective and Reversible Chemosensors Based on Dual-Ratiometric Fluorescent Electrospun Nanofibers with pH- and Fe(3+)-Modulated Multicolor Fluorescence Emission.  

PubMed

Novel dual-ratiometric fluorescent electrospun (ES) nanofibers featuring high sensitivity for pH and ferric ion (Fe(3+)) were prepared using binary blends of poly(2-hydroxyethyl methacrylate-co-N-methylolacrylamide-co-nitrobenzoxadiazolyl derivative) (poly(HEMA-co-NMA-co-NBD)) and a spirolactam rhodamine derivative (SRhBOH) by employing a single-capillary spinneret. The HEMA, NMA, and NBD moieties were designed to exhibit hydrophilic properties, chemical cross-linking, and fluorescence (fluorescence resonance energy transfer (FRET) donor), respectively. The fluorescence emission of SRhBOH was highly selective for pH and Fe(3+); when SRhBOH detected acidic media and Fe(3+), the spirocyclic form of SRhBOH, which is nonfluorescent, was transformed into the opened cyclic form and exhibited strong fluorescence emission. The emission colors of ES nanofibers in acidic or Fe(3+) aqueous solutions changed from green to red because of FRET from NBD (donor) to SRhBOH (acceptor). The off/on switching of the FRET process was modulated by adjusting the SRhBOH blending ratio, pH, and Fe(3+) concentration. Poly(HEMA-co-NMA-co-NBD) ES fibers blended with 20% SRhBOH showed high sensitivity in sensing Fe(3+) and pH because of the substantial 57 nm red shift in emission as well as substantial reversible dual photoluminescence. The prepared FRET-based dual-ratiometric fluorescent ES nanofibrous membranes can be used as "naked eye" sensors and have potential for application in multifunctional environment sensing devices. PMID:25585636

Chen, Bo-Yu; Kuo, Chi-Ching; Huang, Yun-Shao; Lu, Shih-Tung; Liang, Fang-Cheng; Jiang, Dai-Hua

2015-02-01

325

A universal fluorescent aptasensor based on AccuBlue dye for the detection of pathogenic bacteria.  

PubMed

We report a universal fluorescent aptasensor based on the AccuBlue dye, which is impermeant to cell membranes, for the detection of pathogenic bacteria. The sensor consists of AccuBlue, an aptamer strand, and its complementary strand (cDNA) that partially hybridizes to the aptamer strand. We have fabricated two models by changing the sequence of the reaction between the elements in the system. One is the "signal on" model in which the aptamer is first bound to the target, followed by the addition of cDNA and AccuBlue, at which time the cDNA hybridizes with the free unreacted aptamer and forms a double-stranded DNA (dsDNA) duplex. Such hybridization causes AccuBlue to insert into the dsDNA and exhibit significantly increased fluorescence intensity because of the specific intercalation of the AccuBlue into dsDNA rather than single-stranded DNA (ssDNA). The other model, "signal off," involves hybridization of the aptamer with cDNA first, resulting in high fluorescence intensity on the addition of AccuBlue. When the target is added, the aptamer binds the target, causing the cDNA to detach from the dsDNA duplex and resulting in low fluorescence as a result of the liberation of AccuBlue. Because this design is based purely on DNA hybridization, and AccuBlue is impermeant to cell membranes, it could potentially be adapted to a wide variety of analytes. PMID:24650583

Duan, Nuo; Wu, Shijia; Ma, Xiaoyuan; Xia, Yu; Wang, Zhouping

2014-06-01

326

Optimization of a Concanavalin A-based glucose sensor using fluorescence anisotropy  

PubMed Central

To date, the dependent nature of the recognition and transduction mechanisms in optical glucose sensors based upon Concanavalin A (ConA) has tended to prevent the sensors’ full potential from being realized. In this paper, these mechanisms are independently optimized for a given assay configuration in order to decrease the predictive error of a ConA-based glucose sensor and to give a more accurate demonstration of its potential. To this end, we used fluorescence anisotropy as the transduction mechanism to determine the binding of ConA to 4 kDa FITC-dextran by measuring the change in the rotational correlation lifetime between the bound and unbound populations. By tracking the fluorescence anisotropy of this ligand, the ranges of ConA and 4 kDa FITC-dextran concentrations capable of being explored were not limited by the transduction mechanism. Using predetermined association constants, the binding responses to physiological glucose concentrations were predicted for different assay configurations, and experimentally collected fluorescence anisotropy data displayed the predicted trends for these assay configurations. From the experimental results, a calibration fit was generated for the optimized assay configuration to predict the glucose concentrations using the fluorescence anisotropy. This optimized assay displayed a mean standard error of prediction of 7.5 mg/dL (0–300 mg/dL), and 100% of the data points fell within clinically acceptable zones (A and B) upon the Clarke Error Grid Analysis. This indicates that, by independently optimizing the recognition and transduction mechanisms for the final assay configuration, the sensitivity of a competitive binding chemistry using ConA can be appropriately configured for continuous glucose monitoring applications. PMID:23627407

Garza, Javier T.; Coté, Gerard L.

2013-01-01

327

Characterization of the chemical composition of polyisobutylene-based oil-soluble dispersants by fluorescence.  

PubMed

A novel methodology based on fluorescence quenching measurements is introduced to determine quantitatively the amine content of polyisobutylene succinimide (PIBSI) dispersants used as engine oil-additives. To this end, a series of five PIBSI dispersants were prepared by reacting 2 mol equiv of polyisobutylene succinic anhydride (PIBSA) with 1 mol equiv of hexamethylenediamine (HMDA), diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and pentaethylenehexamine to yield the corresponding b-PIBSI dispersants. After having demonstrated that the presence of hydrogen bonds between the polyamine linker and the succinimide carbonyls of the dispersants prevents the quantitative analysis of the (1)H NMR and FTIR spectra of the dispersants to determine their chemical composition, alternative procedures based on gel permeation chromatography (GPC) and fluorescence quenching were implemented to estimate the amine content of the b-PIBSI dispersants. Taking advantage of the doubling in size that occurs when 2 mol of PIBSA are reacted with 1 mol of HMDA, a combination of GPC and FTIR was employed to follow how the chemical composition and molecular weight distribution of the polymers produced evolved with the reaction of PIBSA and HMDA mixed at different molar ratios. These experiments provided the PIBSA-to-HMDA molar ratio yielding the largest b-PIBSI dispersants and this molar ratio was then selected to prepare the four other dispersants. Having prepared five b-PIBSI dispersants with well-defined secondary amine content, the fluorescence of the succinimide groups was found to decrease with increasing number of secondary amines present in the polyamine linker. This result suggests that fluorescence quenching provides a valid method to determine the chemical composition of b-PIBSI dispersants which is otherwise difficult to characterize by standard (1)H NMR and FTIR spectroscopies. PMID:24628080

Pirouz, Solmaz; Wang, Yulin; Chong, J Michael; Duhamel, Jean

2014-04-10

328

Fluorescence-based sensing of p-nitrophenol and p-nitrophenyl substituent organophosphates.  

PubMed

A novel detection method for organophosphate neurotoxins has been described, based on the fluorescence quenching of a Coumarin derivative. These dyes are similar in structure to some organophosphates (OPs), and they fluoresce in the blue-green region of the spectra. This methodology has been utilized for the detection of organophosphates whose hydrolysis product is p-nitrophenol by using an enzyme, organophosphorus hydrolase (OPH). Coumarin1 in the presence of p-nitrophenol results in a quenching of fluorescence, providing a direct measure of the concentration of p-nitrophenol present in the sample. The decrease in fluorescence intensity is proportional to the paraoxon concentration in the range of 7.0x10(-7)-1.7x10(-4) M. The specificity of this sensing application for p-nitrophenyl substituent OPs has also been demonstrated. OPs are a class of synthetic organic pesticides which generally have a short residual life and can cause numerous acute and chronic health effects. They have been an integral part of the agricultural industry for the past several decades due to their target specificities and selectable toxicities. The toxic nature of these compounds can be attributed to the species-specific inhibition of acetylcholinesterase (AChE), an important enzyme responsible for the regeneration of neural synaptic function. In addition to their wide agricultural and urban usage, they have also been exploited for the development of neurological chemical warfare agents. Currently available technologies for OP detection include sol-gel thin films, screen printed electrodes, acoustic patterning, gas chromatography-mass spectrometry, and various other intricate techniques that have limited field applicabilities. This optically-based approach promises much simpler and more direct detection capabilities. PMID:17616234

Paliwal, Sheetal; Wales, Melinda; Good, Theresa; Grimsley, Janet; Wild, James; Simonian, Aleksandr

2007-07-16

329

Ultra-portable explosives sensor based on a CMOS fluorescence lifetime analysis micro-system  

NASA Astrophysics Data System (ADS)

This work explores the use of a green-light-emitting copolymer as a chemosensor to detect nitroaromatic-based explosive vapors by recording photoluminescence (PL) and time-resolved PL decay. We show successful detection of 10 ppb 1,4-dinitrobenzene (DNB) vapor. Both a conventional time-correlated single photon counting (TCSPC) device and CMOS time-resolved fluorescence lifetime micro-system are used in the DNB detection. An ultra-portable on-site explosive sensor based on the micro-system has also been demonstrated. This gives rise to the potential for real-time, reliable, inexpensive organic/inorganic hybrid explosives detection.

Wang, Yue; Rae, Bruce R.; Henderson, Robert K.; Gong, Zheng; Mckendry, Jonathan; Gu, Erdan; Dawson, Martin D.; Turnbull, Graham A.; Samuel, Ifor D. W.

2011-09-01

330

A protease assay for two-photon crosscorrelation and FRET analysis based solely on fluorescent proteins  

PubMed Central

GFP and the red fluorescent protein, DsRed, have been combined to design a protease assay that allows not only for fluorescence resonance energy transfer (FRET) studies but also for dual-color crosscorrelation analysis, a single-molecule-based method that selectively probes the concomitant movement of two distinct tags. The measurement principle is based on a spectrally resolved detection of single molecules diffusing in and out of a diffraction-limited laser focus. Double-labeled substrate molecules are separated into two single-labeled products by specific cleavage at a protease cleavage site between the two flanking tags, DsRed and GFP, thus disrupting joint fluctuations in the two detection channels and terminating FRET between the two labels. In contrast to enzyme assays based solely on FRET, this method of dual-color crosscorrelation is not limited to a certain range of distances between the fluorophores and is much more versatile with respect to possible substrate design. To simplify the measurement setup, two-photon excitation was used, allowing for simultaneous excitation of both tags with a single infrared laser wavelength. The general concept was experimentally verified with a GFP–peptide–DsRed construct containing the cleavage site for tobacco etch virus protease. Two-photon excitation in the infrared and the use of cloneable tags make this assay easily adaptable to intracellular applications. Moreover, the combination of FRET and crosscorrelation analysis in a single-molecule-based approach promises exciting perspectives for miniaturized high-throughput screening based on fluorescence spectroscopy. PMID:12209012

Kohl, Tobias; Heinze, Katrin G.; Kuhlemann, Rene; Koltermann, Andre; Schwille, Petra

2002-01-01

331

Multipoint parallel excitation and CCD-based imaging system for high-throughput fluorescence detection of biochip micro-arrays  

Microsoft Academic Search

We report the development and the characterization of a multipoint parallel excitation and CCD-based imaging system for high-throughput fluorescence detection of biochip micro-arrays. A two-dimensional array of (19×19) points with uniform intensity distribution, generated by a holographic array generator, was used for parallel excitation of two-dimensional micro-arrays of fluorescence samples. A CCD-based imaging system was used for high-throughput parallel detection

D. S. Mehta; C. Y. Lee; A. Chiou

2001-01-01

332

Sensitivity of Ag:DNA fluorescence to single base mutations of hairpin strands  

NASA Astrophysics Data System (ADS)

DNA strands can stabilize fluorescent silver clusters composed of just a few atoms [1]. The small size of these photon emitters and their formation in single-stranded DNA [2] give Ag:DNA emitters promise for use in optically-active, self-assembled DNA nanostructures. Exploiting this promise requires an understanding of how fluorophore color relates to the sequence and conformation of the host DNA strand. Here we examine the optical properties of Ag:DNA solutions for a family of DNA hairpins that differ by single base mutations in the hairpin loop. Specific mutations result in spectral redistribution of the fluorescence and large changes in brightness, pointing to geometric control as a means to select specific emitter species.[4pt] [1] J.T. Petty, J. Zheng, N.V. Hud and R.M. Dickson, ``DNA-templated Ag nanocluster formation,'' J. Am. Chem. Soc, 126, 5207 (2004).[0pt] [2] E.G. Gwinn, P. O'Neill, A. Guerrero, D. Bouwmeester and D.K. Fygenson, ``Sequence-dependent fluorescence from DNA-hosted silver nanoclusters,'' Advanced Materials 20, 279 (2008).

Gwinn, Elisabeth; Hassanzadeh, Rameen; O'Neill, Patrick; Fygenson, Deborah

2010-03-01

333

Fluorescent film sensors based on SAMs of pyrene derivatives for detecting nitroaromatics in aqueous solutions  

NASA Astrophysics Data System (ADS)

The detection of nitroaromatics in aqueous solutions by a novel pyrene-functionalized film has been investigated in the present study. The pyrene moieties were attached on the glass surface via a long flexible spacer based on self-assembled monolayer technique. Steady-state fluorescence measurements revealed that these surface-attached pyrene moieties exhibited both monomer and excimer emission. Nitroaromatics such as 2,4,6-trinitrotoluene, 2,4-dinitrotoluene, and 2,4,6-trinitrophenol (picric acid) were found to efficiently quench the fluorescence emission of this film. The quenching results demonstrated that the excimer emission of these surface-confined pyrene moieties is more sensitive to the presence of nitroaromatics than the monomer emission. The quenching mechanism was examined through fluorescence lifetime measurement and it revealed that the quenching is static in nature and may be caused by electron transfer from the polycyclic aromatics to the nitroaromatics. Furthermore, the response of the film to nitroaromatics is fast and reversible, and the obtained film shows promising potentials in detecting explosives in aqueous environment.

Zhang, Shujuan; Ding, Liping; Lü, Fengting; Liu, Taihong; Fang, Yu

2012-11-01

334

Developing a Fluorescence-based Approach to Screening for Macromolecule Crystallization Conditions  

PubMed Central

Current macromolecule crystallization screening methods rely on the random testing of crystallization conditions, in the hope that one or more will yield positive results, crystals. Most plate outcomes are either clear or precipitated solutions, which results are routinely discarded by the experimenter. However, many of these may in fact be close to crystallization conditions, which fact is obscured by the nature of the apparent outcome. We are developing a fluorescence-based approach to the determination of crystallization conditions, which approach can also be used to assess conditions that may be close to those that would give crystals. The method uses measurements of fluorescence anisotropy and intensity. The method was first tested using model proteins, with likely outcomes as determined by fluorescence measurements where the plate data showed either clear or precipitated solutions being subjected to optimization screening. The results showed a ~83% increase in the number of crystallization conditions. The method was then tried as the sole screening method with a number of test proteins. In every case at least one or more crystallization conditions were found, and it is estimated that ~53% of these would not have been found using a plate screen. PMID:21792347

Pusey, Marc L.

2011-01-01

335

Rationally designed aptamer-based fluorescence polarization sensor dedicated to the small target analysis.  

PubMed

A direct fluorescence polarization (FP) assay strategy, dedicated to the small molecule sensing and based on the unique induced-fit binding mechanism of end-labelled nucleic acid aptamers, has been recently developed by our group. Small target binding has been successfully converted into a significant increase of the fluorescence anisotropy signal presumably produced by the reduction of the local motional freedom of the dye. In order to generalize the approach, a rational FP sensor methodology was established herein, by engineering instability in the secondary structure of an aptameric recognition element. The anti-adenosine DNA aptamer, labelled by a single fluorescein dye at its 3' extremity, was employed as a model functional nucleic acid probe. The terminal stem of the stem-loop structure was shortened to induce a destabilized/denatured conformation which promoted the local segmental mobility of the dye and then a significant depolarization process. Upon target binding, the structural change of the aptamer induced the formation of a stable stem-loop structure, leading to the reduction of the dye mobility and the increase in the fluorescence anisotropy signal. This reasoned approach was applied to the sensing of adenosine and adenosine monophosphate and their chiral analysis. PMID:20034782

Perrier, Sandrine; Ravelet, Corinne; Guieu, Valérie; Fize, Jennifer; Roy, Béatrice; Perigaud, Christian; Peyrin, Eric

2010-03-15

336

Fluorescence-based fast diagnostics platform for the direct and indirect immunodiagnostic analysis methods  

NASA Astrophysics Data System (ADS)

VTT Technical Research Centre of Finland has developed two reader prototypes for immunodiagnostic tests. VTT has also developed a one-step, homogeneous noncompetitive immunoassay for small analytes using recombinant antibodies and morphine as the model analyte. VTT developed reader for lateral flow test. Lateral flow test is a strip, which has a sample area and a detection area. In the sample area there are antibodies attached to gold or fluorescence particles, which are captured into the detection area, if a sample has a desired analyte. The concentration of the measured sample is then calculated from the fluorescence detection or color change. The second developed prototype reader is based on Time Resolved Fluorescence Resonance Energy Transfer (TR-FRET). In this reader samples are put on microwell array. There are two fluorophores in each of the wells and emission of both fluorophores is measured. The sample concentration is calculated from these emission signals. The optimization of homogenous FRET assays for morphine was included to this project. The first results obtained with the TR-FRET reader prototype show that the sensitivity of the current morphine test is clearly adequate.

Mannila, Rami; Pulli, Timo; Saari, Heikki; Tappura, Kirsi; Tuppurainen, Jussi; Välimäki, Hannu; Niskanen, Aimo

2007-07-01

337

An iminocoumarin benzothiazole-based fluorescent probe for imaging hydrogen sulfide in living cells.  

PubMed

Hydrogen sulfide (H2S) has recently been identified as the third gaseous signaling molecule that is involved in regulating many important cellular processes. We report herein a novel fluorescent probe for detecting H2S based on iminocoumarin benzothiazole scaffold. The probe displayed high sensitivity and around 80-fold increment in fluorescence signal after reacting with H2S under physiological condition. The fluorescent intensity of the probe was linearly related to H2S concentration in the range of 0-100?M with a detection limit of 0.15?M (3?/slope). The probe also showed excellent selectivity towards H2S over other biologically relevant species, including ROS, RSS and RNS. Its selectivity for H2S is 32 folds higher than other reactive sulfur species. Furthermore, the probe has been applied for imaging H2S in living cells. Cell imaging experiments demonstrated that the probe is cell-permeable and can be used to monitor the alteration of H2S concentrations in living cells. We envisage that this probe can provide useful tools to further elucidate the biological roles of H2S. PMID:25640139

Zhang, Huatang; Xie, Yusheng; Wang, Ping; Chen, Ganchao; Liu, Ruochuan; Lam, Yun-Wah; Hu, Yi; Zhu, Qing; Sun, Hongyan

2015-04-01

338

Development of fluorescence imaging-based assay for screening cardioprotective compounds from medicinal plants.  

PubMed

Medicinal plants have been widely recognized as a renewable resource for the discovery of novel leads and drug. In this study, an approach for screening and identification compounds with cardioprotective activity from medicinal plant extracts by cellular-fluorescence imaging technique was developed. It is a cell-based assay for measuring mitochondrial membrane potential changes in H9c2 cardiac muscle cells exposed to H(2)O(2) by using a fluorescence automatic microscopy screening platform. Rhodamine 123 was used as the fluorescent dye to indicate the change of mitochondrial membrane potential. The sensitivity and linear range of the proposed approach were evaluated and validated using vitamin C, an antioxidative compound. The method was applied to screen active components with potent cardioprotective effects from a traditional Chinese formula. The potential cardioprotective components were identified by liquid chromatography coupled with mass spectrometry (LC/MS). Moreover, the utility of the proposed approach was further validated by three compounds (salvianolic acid B, protocatechuic aldehyde, and tanshinone II A) identified from the formula which showed cardioprotective effects in a dose-dependent manner. These applications suggested that the proposed rapid and sensitive screening approach offers an efficient way to discover active components or compounds from medicinal plants. PMID:21819864

Wang, Yi; Zhao, Xiaoping; Gao, Xiumei; Nie, Xiaojing; Yang, Yingxin; Fan, Xiaohui

2011-09-19

339

Energy transfer in PPV-based conjugated polymers: a defocused widefield fluorescence microscopy study.  

PubMed

Both pendant and main chain conjugated MEH-PPV based polymers have been studied at the level of single chains using confocal and widefield fluorescence microscopy techniques. In particular, defocused widefield fluorescence is applied to reveal the extent of energy transfer in these polymers by identifying whether they act as single emitters. For main chain conjugated MEH-PPV, molecular weight and the surrounding matrix play a primary role in determining energy transport processes and whether single emitter behaviour is observed. Surprisingly in polymers with a saturated backbone but containing the same pendant MEH-PPV oligomer on each repeating unit, intra-chain energy transfer to a single emitter is also apparent. The results imply there is chromophore heterogeneity that can facilitate energy funneling to the emitting site. Both main chain conjugated and pendant MEH-PPV polymers exhibit changes in orientation of the emission dipole during a fluorescence trajectory of many seconds, whereas a model MEH-PPV oligomer does not. The results suggest that, in the polymers, the nature of the emitting chromophores can change during the time trajectory. PMID:24618928

Hooley, E N; Tilley, A J; White, J M; Ghiggino, K P; Bell, T D M

2014-04-21

340

Fluorescence-based proxies for lignin in freshwater dissolved organic matter  

USGS Publications Warehouse

Lignin phenols have proven to be powerful biomarkers in environmental studies; however, the complexity of lignin analysis limits the number of samples and thus spatial and temporal resolution in any given study. In contrast, spectrophotometric characterization of dissolved organic matter (DOM) is rapid, noninvasive, relatively inexpensive, requires small sample volumes, and can even be measured in situ to capture fine-scale temporal and spatial detail of DOM cycling. Here we present a series of cross-validated Partial Least Squares models that use fluorescence properties of DOM to explain up to 91% of lignin compositional and concentration variability in samples collected seasonally over 2 years in the Sacramento River/San Joaquin River Delta in California, United States. These models were subsequently used to predict lignin composition and concentration from fluorescence measurements collected during a diurnal study in the San Joaquin River. While modeled lignin composition remained largely unchanged over the diurnal cycle, changes in modeled lignin concentrations were much greater than expected and indicate that the sensitivity of fluorescence-based proxies for lignin may prove invaluable as a tool for selecting the most informative samples for detailed lignin characterization. With adequate calibration, similar models could be used to significantly expand our ability to study sources and processing of DOM in complex surface water systems.

Hernes, Peter J.; Bergamaschi, Brian A.; Eckard, Robert S.; Spencer, Robert G.M.

2009-01-01

341

Ion track reconstruction in 3D using alumina-based fluorescent nuclear track detectors  

E-print Network

Fluorescent nuclear track detectors (FNTDs) based on Al2O3:C,Mg single crystal combined with confocal microscopy provide 3D information on ion tracks with a resolution only limited by light diffraction. FNTDs are also ideal substrates to be coated with cells to engineer cell-fluorescent ion track hybrid detectors. This radiobiological tool enables a novel platform linking cell responses to physical dose deposition on a sub-cellular level in proton and heavy ion therapies. To achieve spatial correlation between single ion hits in the cell coating and its biological response the ion traversals have to be reconstructed in 3D using the depth information gained by the FNTD read-out. FNTDs were coated with a confluent human lung adenocarcinoma epithelial cell layer. Carbon ion irradiation of the hybrid detector was performed perpendicular and angular to the detector surface. In-situ imaging of the fluorescently labeled cell layer and the FNTD was performed in a sequential read-out. Making use of the trajectory info...

Niklas, Martin; Akselrod, Mark S; Abollahi, Amir; Jäkel, Oliver; Greilich, Steffen

2013-01-01

342

Development of a Fluorescence Resonance Energy Transfer (FRET)-Based DNA Biosensor for Detection of Synthetic Oligonucleotide of Ganoderma boninense  

PubMed Central

An optical DNA biosensor based on fluorescence resonance energy transfer (FRET) utilizing synthesized quantum dot (QD) has been developed for the detection of specific-sequence of DNA for Ganoderma boninense, an oil palm pathogen. Modified QD that contained carboxylic groups was conjugated with a single-stranded DNA probe (ssDNA) via amide-linkage. Hybridization of the target DNA with conjugated QD-ssDNA and reporter probe labeled with Cy5 allows for the detection of related synthetic DNA sequence of Ganoderma boninense gene based on FRET signals. Detection of FRET emission before and after hybridization was confirmed through the capability of the system to produce FRET at 680 nm for hybridized sandwich with complementary target DNA. No FRET emission was observed for non-complementary system. Hybridization time, temperature and effect of different concentration of target DNA were studied in order to optimize the developed system. The developed biosensor has shown high sensitivity with detection limit of 3.55 × 10?9 M. TEM results show that the particle size of QD varies in the range between 5 to 8 nm after ligand modification and conjugation with ssDNA. This approach is capable of providing a simple, rapid and sensitive method for detection of related synthetic DNA sequence of Ganoderma boninense.

Mohd Bakhori, Noremylia; Yusof, Nor Azah; Abdullah, Abdul Halim; Hussein, Mohd Zobir

2013-01-01

343

Fluorescence Imaging-Based High-Throughput Screening of Fast- and Slow-Cycling LOV Proteins  

PubMed Central

Light-oxygen-voltage (LOV) domains function as blue light-inducible molecular switches. The photosensory LOV domains derived from plants and fungi have provided an indispensable tool for optogenetics. Here we develop a high-throughput screening system to efficiently improve switch-off kinetics of LOV domains. The present system is based on fluorescence imaging of thermal reversion of a flavin cofactor bound to LOV domains. We conducted multi site-directed random mutagenesis of seven amino acid residues surrounding the flavin cofactor of the second LOV domain derived from Avena sativa phototropin 1 (AsLOV2). The gene library was introduced into Escherichia coli cells. Then thermal reversion of AsLOV2 variants, respectively expressed in different bacterial colonies on agar plate, was imaged with a stereoscopic fluorescence microscope. Based on the mutagenesis and imaging-based screening, we isolated 12 different variants showing substantially faster thermal reversion kinetics than wild-type AsLOV2. Among them, AsLOV2-V416T exhibited thermal reversion with a time constant of 2.6 s, 21-fold faster than wild-type AsLOV2. With a slight modification of the present approach, we also have efficiently isolated 8 different decelerated variants, represented by AsLOV2-V416L that exhibited thermal reversion with a time constant of 4.3×103 s (78-fold slower than wild-type AsLOV2). The present approach based on fluorescence imaging of the thermal reversion of the flavin cofactor is generally applicable to a variety of blue light-inducible molecular switches and may provide a new opportunity for the development of molecular tools for emerging optogenetics. PMID:24367542

Kawano, Fuun; Aono, Yuki; Suzuki, Hideyuki; Sato, Moritoshi

2013-01-01

344

Compact and cost effective instrument for detecting drug precursors in different environments based on fluorescence polarization  

NASA Astrophysics Data System (ADS)

Several techniques for detecting chemical drug precursors have been developed in the last decade. Most of them are able to identify molecules at very low concentration under lab conditions. Other commercial devices are able to detect a fixed number and type of target substances based on a single detection technique providing an absence of flexibility with respect to target compounds. The construction of compact and easy to use detection systems providing screening for a large number of compounds being able to discriminate them with low false alarm rate and high probability of detection is still an open concern. Under CUSTOM project, funded by the European Commission within the FP7, a stand-alone portable sensing device based on multiple techniques is being developed. One of these techniques is based on the LED induced fluorescence polarization to detect Ephedrine and Benzyl Methyl Keton (BMK) as a first approach. This technique is highly selective with respect to the target compounds due to the generation of properly engineered fluorescent proteins which are able to bind the target analytes, as it happens in an "immune-type reaction". This paper deals with the advances in the design, construction and validation of the LED induced fluorescence sensor to detect BMK analytes. This sensor includes an analysis module based on high performance LED and PMT detector, a fluidic system to dose suitable quantities of reagents and some printed circuit boards, all of them fixed in a small structure (167mm × 193mm × 228mm) with the capability of working as a stand-alone application.

Antolín-Urbaneja, J. C.; Eguizabal, I.; Briz, N.; Dominguez, A.; Estensoro, P.; Secchi, A.; Varriale, A.; Di Giovanni, S.; D'Auria, S.

2013-05-01

345

Label-free fluorescence assay for thrombin based on unmodified quantum dots.  

PubMed

Rapid and sensitive assay of thrombin and its inhibition in a high-throughput manner is of great significance in the diagnostic and pharmaceutical fields. In this article, we developed a novel biosensor for the detection of thrombin and its inhibition based on the aggregation behavior of the unmodified CdTe QDs. A cationic substrate peptide of thrombin (GGLVPRGSCC-NH2, S-peptide) can attach to the surface of CdTe QDs, partly balance their surface negative charge, and induce the aggregation of QDs, which results in the fluorescence quenching of QDs. After hydrolysis of S-peptide by thrombin, two kinds of shorter peptides (P1-peptide, GGLVPR, and P2-peptide, GSCC) are produced. The uncharged P2-peptide rather than the cationic P1-peptide would bind to QDs. Hence, the CdTe QDs were kept stable in the solution with the fluorescence being maintained. The change of fluorescence intensity would sensitively respond to thrombin activity and its inhibition. Fluorescence spectroscopy, transmission electron microscopy and dynamic light scattering were performed to discuss the quenching mechanism. Under optimized conditions, this method enables measurement of thrombin in the range of 10-100 ?U/mL with the detection limit of 1.5 ?U/mL. Not only in buffer, but also in blood serum, such sensor exhibited extraordinarily high sensitivity and excellent specificity. In addition, the typical inhibitor of thrombin, hirudin, was also successfully assayed by this method (from 2 ?U/mL to 30 ?U/mL with the LOD of 0.21 ?U/mL). Furthermore, the present approach could also be potentially extended to other proteases and their inhibitors detection with unmodified CdTe QDs. PMID:24240167

Li, Lijun; Lin, Hui; Lei, Chunyang; Nie, Zhou; Huang, Yan; Yao, Shouzhuo

2014-04-15

346

Gramicidin-based Fluorescence Assay; for Determining Small Molecules Potential for Modifying Lipid Bilayer Properties  

PubMed Central

Many drugs and other small molecules used to modulate biological function are amphiphiles that adsorb at the bilayer/solution interface and thereby alter lipid bilayer properties. This is important because membrane proteins are energetically coupled to their host bilayer by hydrophobic interactions. Changes in bilayer properties thus alter membrane protein function, which provides an indirect way for amphiphiles to modulate protein function and a possible mechanism for "off-target" drug effects. We have previously developed an electrophysiological assay for detecting changes in lipid bilayer properties using linear gramicidin channels as probes 3,12. Gramicidin channels are mini-proteins formed by the transbilayer dimerization of two non-conducting subunits. They are sensitive to changes in their membrane environment, which makes them powerful probes for monitoring changes in lipid bilayer properties as sensed by bilayer spanning proteins. We now demonstrate a fluorescence assay for detecting changes in bilayer properties using the same channels as probes. The assay is based on measuring the time-course of fluorescence quenching from fluorophore-loaded large unilamellar vesicles due to the entry of a quencher through the gramicidin channels. We use the fluorescence indicator/quencher pair 8-aminonaphthalene-1,3,6-trisulfonate (ANTS)/Tl+ that has been successfully used in other fluorescence quenching assays 5,13. Tl+ permeates the lipid bilayer slowly 8 but passes readily through conducting gramicidin channels 1,14. The method is scalable and suitable for both mechanistic studies and high-throughput screening of small molecules for bilayer-perturbing, and potential "off-target", effects. We find that results using this method are in good agreement with previous electrophysiological results 12. PMID:20972414

Ingólfsson, Helgi I.; Sanford, R. Lea; Kapoor, Ruchi; Andersen, Olaf S.

2010-01-01

347

Structural diversity of new solid-state luminophores based on quinoxaline-?-ketoiminate boron difluoride complexes with remarkable fluorescence switching properties.  

PubMed

A series of structurally simple yet highly tunable organoboron luminophores was designed and synthesized. The solid-state fluorescence quantum yields exhibit nearly exponential growth by decorating the luminophore with additional sterically demanding substituents. Uniquely, the luminescence of these organoboron dyes can be easily switched on/off by acidic/basic vapors, yielding a solid-state fluorescence switching function. PMID:25572298

Liao, Chia-Wei; Rao M, Rajeswara; Sun, Shih-Sheng

2015-01-29

348

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. PMID:23785056

Ealba, Erin L.; Schneider, Richard A.

2013-01-01

349

Simple spectrophotometric method for determination of zirconium or hafnium in selected molybdenum-base alloys.  

PubMed

A simple analytical procedure is described for determining zirconium or hafnium in molybdenum-base alloys by formation of the Arsenazo III complex of zirconium or hafnium in 9 M hydrochloric acid medium. The absorbance is measured at 670 nm. Molybdenum (10 mg), titanium (1 mg), and rhenium (10 mg) have no adverse effect. No prior separation is needed. The relative standard deviation is 1.3-2.7%. PMID:18961121

Dupraw, W A

1972-06-01

350

A Simple PIFA-Based Tunable Internal Antenna for Personal Communication Handsets  

Microsoft Academic Search

A simple planar inverted F antenna (PIFA)-based tunable internal antenna is proposed for personal communication handset applications. The antenna can covers following frequency bands: DCS (1710-1880 MHz), PCS (1880-1990 MHz), UMTS (1900-2170 MHz), WiBro (2300-2390 MHz), WLAN (5.2 and 5.8 GHz), Bluetooth (2400-2480 MHz), and ISM band (2500-2700 MHz). Varactor diode is used to get tuning over the wide frequency

Viet-Anh Nguyen; Rashid-Ahmad Bhatti; Seong-Ook Park

2008-01-01

351

Simple Fibroblast-Based Assay To Test the Pyrazinamide Susceptibility of Mycobacterium tuberculosis  

Microsoft Academic Search

Received 4 May 2004\\/Returned for modification 5 August 2004\\/Accepted 11 October 2004 A simple fibroblast-based assay (SFA) was found to be efficient in evaluating the susceptibilities of clinical isolates of Mycobacterium tuberculosis to pyrazinamide (PZA). Forty-five clinical isolates were examined. The MICs of PZA for susceptible strains in an SFA were between 3.13 and 12.5 g\\/ml, and the MICs of

Takemasa Takii; Sonomi Hamasaki; Kazue Hirano; Chiyoji Abe; Kikuo Onozaki

2005-01-01

352

A new selective colorimetric and fluorescent chemodosimeter for HSO4- based on hydrolysis of Schiff base  

NASA Astrophysics Data System (ADS)

Two new receptors 1 and 2 were prepared, and their chromogenic and fluorogenic behaviors toward various anions were investigated. Receptors 1 and 2 show exclusive response toward HSO4- ion and also distinguish HSO4- from other anions by different color changes in aqueous solution (CH3CN/H2O = 4/1, v/v). Between them receptor 1 selectively exhibits a pronounced HSO4--induced fluorescence enhancement. The detection limit for the HSO4- ion was determined as (0.24 ± 0.03 ?M). Thus, the receptor 1 can be used as a colorimetric and fluorescent sensor for the determination of HSO4- ion. The sensing mechanism has been suggested to proceed via a hydrolysis process. The hydrolysis product has been isolated and further identified by 1H NMR spectroscopy, ESI-MS analysis and X-ray diffraction.

Lin, Chi-Yung; Huang, Keh-Feng; Yen, Yao-Pin

2013-11-01

353

Spectral filtering modulation method for estimation of hemoglobin concentration and oxygenation based on a single fluorescence emission spectrum in tissue phantoms  

PubMed Central

Purpose: Hemoglobin concentration and oxygenation in tissue are important biomarkers that are useful in both research and clinical diagnostics of a wide variety of diseases such as cancer. The authors aim to develop simple ratiometric method based on the spectral filtering modulation (SFM) of fluorescence spectra to estimate the total hemoglobin concentration and oxygenation in tissue using only a single fluorescence emission spectrum, which will eliminate the need of diffuse reflectance measurements and prolonged data processing as required by most current methods, thus enabling rapid clinical measurements. Methods: The proposed method consists of two steps. In the first step, the total hemoglobin concentration is determined by comparing a ratio of fluorescence intensities at two emission wavelengths to a calibration curve. The second step is to estimate oxygen saturation by comparing a double ratio that involves three emission wavelengths to another calibration curve that is a function of oxygen saturation for known total hemoglobin concentration. Theoretical derivation shows that the ratio in the first step is linearly proportional to the total hemoglobin concentrations and the double ratio in the second step is related to both total hemoglobin concentration and hemoglobin oxygenation for the chosen fiber-optic probe geometry. Experiments on synthetic fluorescent tissue phantoms, which included hemoglobin with both constant and varying oxygenation as the absorber, polystyrene spheres as scatterers, and flavin adenine dinucleotide as the fluorophore, were carried out to validate the theoretical prediction. Results: Tissue phantom experiments confirm that the ratio in the first step is linearly proportional to the total hemoglobin concentration and the double ratio in the second step is related to both total hemoglobin concentrations and hemoglobin oxygenation. Furthermore, the relations between the two ratios and the total hemoglobin concentration and hemoglobin oxygenation are insensitive to the scattering property of the tissue model for the chosen probe geometry. Conclusions: A simple two-step ratiometric method based on the SFM of fluorescence spectra is proposed to estimate the total hemoglobin concentration and oxygenation in a tissue model using only a single fluorescence emission spectrum. This method is immune to the variation in system throughput caused by inconsistent optical coupling because of its ratiometric nature. Calibration curves are insensitive to the scattering coefficient for the chosen probe geometry. Moreover, since only fluorescence intensities at a few wavelengths in a single fluorescence emission spectrum are needed in this method, the SFM method minimizes the amount of required data and reduces the data acquisition time. Finally, since this method does not use nonlinear regression, it can dramatically save computation time in data processing. The high sensitivity of the proposed method to superficial tissue volumes makes it ideal for fluorescence based oximetry and medical diagnostics in applications such as early epithelial cancer diagnosis or wherever the measured tissue volume is exposed to the outside such as in open surgery. PMID:19928112

Liu, Quan; Vo-Dinh, Tuan

2009-01-01

354

Pixel-based criteria-oriented analysis of time-lapse Ca2+-fluorescence images.  

PubMed

Since its inception, the analysis of time-lapse video-images acquired during Ca2+ imaging experiments using fluorescence microscopy has been progressively optimized for achieving a high temporal resolution. In contrast, the spatial resolution of the acquired images is often compromised during analysis to varying degrees by the need to draw regions of interest (ROI). We developed a strategy to analyze images at the acquired spatial resolution-pixel-by-pixel, grouping all pixels based on criteria of interest (COI) in regard to their associated fluorescence values over time and visualizing the distributions of the pixel-groups detected in a pseudo-colored map. We applied this pixel-based COI-strategy to the analysis of relative intracellular free calcium levels (Ca(i)(2+)) in attached cultured embryonic hippocampal cells under baseline and experimental conditions designed to evaluate the contribution of extracellular Ca2+ (Ca(e)(2+)) to baseline Ca(i)(2+) levels. We discovered distinct groups of Ca(e)(2+)-dependent Ca(i)(2+) regulation patterns emergent during the earliest phases of hippocampal cell differentiation, which were not limited to inter-cell differences. Thus, pixel-based COI-analysis of time-lapse images can be used to disclose distinct patterns of Ca(e)(2+)-dependent Ca(i)(2+) levels and their corresponding subcellular distributions in developing hippocampal cells. Such a strategy should be useful in studying the emergence and distribution of Ca(i)(2+) signaling at subcellular levels of resolution using fluorescence microscopy. PMID:12906945

Lorenz, Jürgen J; Lorenz, Matthias G O; Barker, Jeffery L

2003-08-15

355

Ratiometric fluorescent chemosensor for fluoride ion based on inhibition of excited state intramolecular proton transfer.  

PubMed

ESIPT based benzimidazole derivative has been synthesized and investigated their photophysical behavior towards various anions. The probe 2 has been used for selective estimation of F(-) ions as compared to other anions and signaled the binding event through formation of new absorption band at 360nm and emission band at 420nm. The probe 2 showed fluorescence behavior towards fluoride ions through hydrogen bonding interactions and restricted the ESIPT emission at 540nm from OH to nitrogen of benzimidazole moiety to release its enol emission at 420nm. PMID:25463052

Gupta, Akul Sen; Paul, Kamaldeep; Luxami, Vijay

2015-03-01

356

The Pocketscope: a spatial light modulator based epi-fluorescence microscope for optogenetics  

NASA Astrophysics Data System (ADS)

Microscopy incorporating spatial light modulators (SLMs) enables three dimensional (3D) excitation and monitoring of the activity of neuronal ensembles, enabling studies of neuronal circuit activity both in vitro and in vivo. In this paper we present a portable (22 cm x 42.5 cm x 30 cm), SLM-based epi-fluorescence upright microscope ("Pocketscope") that enables 3D calcium imaging and photoactivation of neurons in brain slices. Here we describe the implementation of the instrument; quantify the volume over which neural activity can be excited; and demonstrate the use of the system for mapping neural circuits in brain slices.

Linnenberger, Anna; Peterka, Darcy S.; Quirin, Sean; Yuste, Rafael

2014-09-01

357

Electron Transfer-Based Single Molecule Fluorescence as a Probe for Nano-Environment Dynamics  

PubMed Central

Electron transfer (ET) is one of the most important elementary processes that takes place in fundamental aspects of biology, chemistry, and physics. In this review, we discuss recent research on single molecule probes based on ET. We review some applications, including the dynamics of glass-forming systems, surface binding events, interfacial ET on semiconductors, and the external field-induced dynamics of polymers. All these examples show that the ET-induced changes of fluorescence trajectory and lifetime of single molecules can be used to sensitively probe the surrounding nano-environments. PMID:24496314

Chen, Ruiyun; Wu, Ruixiang; Zhang, Guofeng; Gao, Yan; Xiao, Liantuan; Jia, Suotang

2014-01-01

358

Biomolecular imaging based on far-red fluorescent protein with a high two-photon excitation action cross section  

NASA Astrophysics Data System (ADS)

The two-photon excitation action cross section of Hc-Red fluorescent proteins (Hc-RFPs) is measured and found to be of the same order as that of enhanced green fluorescent proteins. With a 618 nm emission wavelength in the far-red region and with an excitation wavelength around 1200 nm, Hc-RPF-based two-photon fluorescence microscopy (2PFM) can offer deep penetration capability inside live samples and is ideal for in vivo gene expression study and biomolecular imaging in live objects. In vivo 2PFM of the developing heart deep inside a transgenic zebrafish embryo tagged by Hc-RFP is also successfully demonstrated.

Tsai, Tsung-Han; Lin, Cheng-Yung; Tsai, Huai-Jen; Chen, Szu-Yu; Tai, Shih-Peng; Lin, Kung-Hsuan; Sun, Chi-Kuang

2006-04-01

359

The performance of 2D array detectors for light sheet based fluorescence correlation spectroscopy.  

PubMed

Single plane illumination microscopy based fluorescence correlation spectroscopy (SPIM-FCS) is a new method for imaging FCS in 3D samples, providing diffusion coefficients, transport, flow velocities and concentrations in an imaging mode. SPIM-FCS records correlation functions over a whole plane in a sample, which requires array detectors for recording the fluorescence signal. Several types of image sensors are suitable for FCS. They differ in properties such as effective area per pixel, quantum efficiency, noise level and read-out speed. Here we compare the performance of several low light array detectors based on three different technologies: (1) Single-photon avalanche diode (SPAD) arrays, (2) passive-pixel electron multiplying charge coupled device (EMCCD) and (3) active-pixel scientific-grade complementary metal oxide semiconductor cameras (sCMOS). We discuss the influence of the detector characteristics on the effective FCS observation volume, and demonstrate that light sheet based SPIM-FCS provides absolute diffusion coefficients. This is verified by parallel measurements with confocal FCS, single particle tracking (SPT), and the determination of concentration gradients in space and time. While EMCCD cameras have a temporal resolution in the millisecond range, sCMOS cameras and SPAD arrays can extend the time resolution of SPIM-FCS down to 10 ?s or lower. PMID:23571955

Singh, Anand Pratap; Krieger, Jan Wolfgang; Buchholz, Jan; Charbon, Edoardo; Langowski, Jörg; Wohland, Thorsten

2013-04-01

360

Fluorescent gold nanoclusters based photoelectrochemical sensors for detection of H2O2 and glucose.  

PubMed

In this work, low-toxicity fluorescent gold nanoclusters (AuNCs) based photoelectrochemical sensors were developed for H2O2 and glucose detection. Herein, the processes used to fabricate the sensors and the photoelectrochemical performances of the sensors under different conditions were presented. Based on the energy band levels of the AuNCs and electron tunneling processes, a detailed photoelectrochemical sensing model was given. The designed sensors were then used for H2O2 and glucose detection without any extra modification of the AuNCs or complex enzyme immobilization. The results demonstrate that the AuNCs allow for H2O2 sensing based on their capacity for both fluorescence and catalysis. Indeed, it was observed that H2O2 was catalyzed by the AuNCs and reduced by photoinduced electrons derived from excited AuNCs. Furthermore, an enhancement in photocurrent amplitude followed the increase in the concentrations of H2O2 and glucose. The effects of the types of ligands surrounding the AuNCs and the applied potential on the output photocurrent were well studied to optimize the measurement conditions. The sensitivity and LOD of MUA-AuNCs at -500mV were 4.33nA/mM and 35?M, respectively. All experimental results indicated that AuNCs could not only serve as a promising photoelectrical material for building the photoelectrochemical biosensors but as catalysts for H2O2 sensing. PMID:25190086

Zhang, Jianxiu; Tu, Liping; Zhao, Shuang; Liu, Guohua; Wang, Yangyun; Wang, Yong; Yue, Zhao

2015-05-15

361

5-(Pyren-1-yl)uracil as a base-discriminating fluorescent nucleobase in pyrrolidinyl peptide nucleic acids.  

PubMed

A pyrene-labeled uridine (U(Py)) monomer for a pyrrolidinyl peptide nucleic acid with an alternating proline/2-aminocyclopentanecarboxylic acid backbone (acpcPNA) was synthesized and incorporated into the PNA. The U(Py) base in acpcPNA could specifically recognize the base A in its complementary DNA strand as determined by thermal denaturation (T(m)) experiments. The fluorescence of the U(Py)-containing single-stranded acpcPNA was very weak in aqueous buffer. In the presence of a complementary DNA target, the fluorescence was enhanced significantly (2.7-41.9 folds, depending on sequences). The fluorescence enhancement was specific to the pairing between U(Py) and dA, making the U(Py)-modified acpcPNA useful as a hybridization-responsive fluorescence probe for DNA-sequence determination. PMID:21976408

Boonlua, Chalothorn; Vilaivan, Chotima; Wagenknecht, Hans-Achim; Vilaivan, Tirayut

2011-12-01

362

Establishment of a New Cell-Based Assay To Measure the Activity of Sweeteners in Fluorescent Food Extracts  

PubMed Central

Taste receptors have been defined at the molecular level in the past decade, and cell-based assays have been developed using cultured cells heterologously expressing these receptors. The most popular approach to detecting the cellular response to a tastant is to measure changes in intracellular Ca2+ concentration using Ca2+-sensitive fluorescent dyes. However, this method cannot be applied to food-derived samples that contain fluorescent substances. To establish an assay system that would be applicable to fluorescent samples, we tested the use of Ca2+-sensitive photoproteins, such as aequorin and mitochondrial clytin-II, as Ca2+ indicators in a human sweet taste receptor assay. Using these systems, we successfully detected receptor activation in response to sweetener, even when fluorescent compounds coexisted. This luminescence-based assay will be a powerful tool to objectively evaluate the sweetness of food-derived samples even at an industry level. PMID:21981007

2011-01-01

363

Multiplex competitive microbead-based flow cytometric immunoassay using quantum dot fluorescent labels.  

PubMed

In answer to the ever-increasing need to perform the simultaneous analysis of environmental hazards, microcarrier-based multiplex technologies show great promise. Further integration with biofunctionalized quantum dots (QDs) creates new opportunities to extend the capabilities of multicolor flow cytometry with their unique fluorescence properties. Here, we have developed a competitive microbead-based flow cytometric immunoassay using QDs fluorescent labels for simultaneous detection of two analytes, bringing the benefits of sensitive, rapid and easy-of-manipulation analytical tool for environmental contaminants. As model target compounds, the cyanobacterial toxin microcystin-LR and the polycyclic aromatic hydrocarbon compound benzo[a]pyrene were selected. The assay was carried out in two steps: the competitive immunological reaction of multiple targets using their exclusive sensing elements of QD/antibody detection probes and antigen-coated microsphere, and the subsequent flow cytometric analysis. The fluorescence of the QD-encoded microsphere was thus found to be inversely proportional to target analyte concentration. Under optimized conditions, the proposed assay performed well within 30 min for the identification and quantitative analysis of the two environmental contaminants. For microcystin-LR and benzo[a]pyrene, dose-response curves with IC(50) values of 5 ?g L(-1) and 1.1 ?g L(-1) and dynamic ranges of 0.52-30 ?g L(-1) and 0.13-10 ?g L(-1) were obtained, respectively. Recovery was 92.6-106.5% for 5 types of water samples like bottled water, tap water, surface water and seawater using only filtration as sample pretreatment. PMID:23062440

Yu, Hye-Weon; Kim, In S; Niessner, Reinhard; Knopp, Dietmar

2012-10-31

364

Stand-off tissue-based biosensors for the detection of chemical warfare agents using photosynthetic fluorescence induction  

Microsoft Academic Search

Tissue biosensors made from immobilized whole-cell photosynthetic microorganisms have been developed for the detection of airborne chemical warfare agents and simulants. The sensor read-out is based on well-known principles of fluorescence induction by living photosynthetic tissue. Like the cyanobacteria and algae from which they were constructed, the sensors are robust and mobile. The fluorescence signal from the sensors was stable

Charlene A. Sanders; Miguel Rodriguez; Elias Greenbaum

2001-01-01

365

Novel BODIPY-based fluorescence turn-on sensor for Fe3+ and its bioimaging application in living cells.  

PubMed

A novel boron-dipyrromethene (BODIPY) based fluorescence turn-on sensor for detecting Fe(3+) in aqueous media is reported with 23-fold fluorescence enhancement. The sensor is comprised of a combination of BODIPY fluorophore and a new Fe(3+)-recognizing cryptand that exhibits high selectivity, sensitivity, and reversibility toward Fe(3+) detection. Cell imaging studies demonstrate that this sensor is capable of sensing Fe(3+) in living cells. PMID:25337695

Sui, Binglin; Tang, Simon; Liu, Taihong; Kim, Bosung; Belfield, Kevin D

2014-11-12

366

Dynamics of a Cortical Neural Network Based on a Simple Model  

NASA Astrophysics Data System (ADS)

The collective dynamics of a randomly connected neuronal network motivated by the anatomy of a mammalian cortex based on a simple model are studied. This simple model can not only reproduce the rich behaviors of biological neurons but also has only two equations and one nonlinear term. By varying some key parameters, such as the connection weights of neurons, the external current injection and the noise of intensity, this neuronal network will exhibit various collective behaviors. It is demonstrated that the synchronization status of the neuronal network has a strong relationship with the key parameters and the external current has more influence on the spiking of inhibitory neurons than that of excitatory neurons. These results may be instructive in understanding the collective dynamics of a mammalian cortex.

Qu, Jing-Yi; Wang, Ru-Bin

2012-08-01

367

Magnetic bead-based fluorescence immunoassay for aflatoxin B1 in food using biofunctionalized rhodamine B-doped silica nanoparticles.  

PubMed

A simple and sensitive fluorescence immunoassay for the detection of aflatoxin B(1) (AFB(1), as a model compound) in food was developed using AFB(1)-bovine serum albumin conjugate (AFB(1)-BSA)-functionalized magnetic beads as immunosensing probes. The recognition elements were prepared by doping of rhodamine B (RB) fluorophore into silica nanoparticles followed by immobilization of monoclonal anti-AFB(1) antibodies on the silica shell. Based on a competitive-type immunoassay format, the assay was performed both in low-binding polypropylene 96-well microtiter plates (MTPs) and in an automated sequential injection (SI) format. Similar detection limit (LOD) of 0.2 ng mL(-1)vs. 0.1 ng mL(-1) but narrower dynamic working linear range of 0.5-7 ng mL(-1)vs. 0.5-30 ng mL(-1) was obtained toward AFB(1) standards with the flow setup compared to the MTP format. Intra-batch assay precision was substantially improved (?5.3% vs.?8.7%) by resorting to the SI manifold. The proposed method features unbiased identification of negative (blank) and positive samples. No significant differences at the 95% confidence level were encountered in the analysis of naturally contaminated peanut samples between the proposed immunoassay and liquid chromatography for determination of AFB(1). PMID:20820489

Tang, Dianping; Yu, Yongliang; Niessner, Reinhard; Miró, Manuel; Knopp, Dietmar

2010-10-01

368

Detection of acrylamide in potato chips using a fluorescent sensing method based on acrylamide polymerization-induced distance increase between quantum dots.  

PubMed

Acrylamide is a neurotoxin and potential carcinogen, but is found in various thermally processed foods such as potato chips, biscuits, and coffee. Simple and sensitive methods for on-line detection of acrylamide are needed to ensure food safety. In this paper, a novel fluorescent sensing method based on acrylamide polymerization-induced distance increase between quantum dots (QDs) was proposed for detecting acrylamide in potato chips. The functional QDs were prepared by their binding with N-acryloxysuccinimide (NAS), which was characterized by Fourier transform infrared (FR-IR) spectra. The carbon-carbon double bonds of NAS modified QDs polymerized with assistance of photo initiator under UV irradiation, leading to QDs getting closer along with fluorescence intensity decreasing. Acrylamide in the sample participated in the polymerization and induced an increase of fluorescence intensity. This method possessed a linear range from 3.5×10(-5) to 3.5 g L(-1) (r(2)=0.94) and a limit of detection of 3.5×10(-5) g L(-1). Although the sensitivity and specificity cannot be compared with standard LC-MS/MS analysis, this new method requires much less time and cost, which is promising for on-line rapid detection of acrylamide in food processing. PMID:24252761

Hu, Qinqin; Xu, Xiahong; Li, Zhanming; Zhang, Ying; Wang, Jianping; Fu, Yingchun; Li, Yanbin

2014-04-15

369

Generation of transducers for fluorescence-based microarrays with enhanced sensitivity and their application for gene expression profiling.  

PubMed

The present paper describes a novel generation of microchips suitable for fluorescence-based assays, such as cDNA, oligonucleotide, or protein microarrays. The new transducers consist of a fully corrugated surface coated with a thin layer of Ta2O5 as a high refractive index material. Tuning of the incident excitation light beam to abnormal reflection geometry results in a confinement of the energy within the thin metal oxide layer. Consequently, strong evanescent fields are generated at the surface of these microchips and fluorophores located within the fields showed up to a 2 order of magnitude increase in fluorescence intensities relative to the epifluorescence signals. We have attributed this phenomenon as evanescent resonance (ER). Due to the surface architecture, propagation distances of the incident energy and fluorescence photons are in the micrometer range, thus preventing cross talk between adjacent regions. ER microchips offer a significant increase in fluorescence intensities in both "snapshot" fluorescence setups and commercial fluorescence scanners. The underlying principle of the novel chips is explained, and quantitative data on the fluorescence enhancement are provided. To demonstrate their potential, the novel chips are used to investigate the dependence of expression levels from metabolic genes in rat liver on drug treatment. In contrast to competitive hybridization, labeled samples were hybridized to individual ER microchips, and changes were observed by comparing with normalized data from different chips. Results obtained in gene expression profiling experiments with phenobarbital-treated rats are shown. PMID:12948122

Budach, Wolfgang; Neuschäfer, Dieter; Wanke, Christoph; Chibout, Salah-Dine

2003-06-01

370

Chromenoquinoline-based thiol probes: a study on the quencher position for controlling fluorescent Off-On characteristics.  

PubMed

The design, synthesis and thiol sensing ability of chromenoquinoline-based fluorescent probes 4, 5 and 6 and are reported here. The relative position of the maleimide moiety was varied along the chromenoquinoline fluorophore to decrease the background fluorescence. Lower background fluorescence in probes 4 and 6 was rationalized by the smaller k(r)/k(nr) values compared to that of probe 5. An intramolecular charge transfer (ICT) mechanism was proposed for quenching and the extent was dependent on the position of the maleimide quencher. Fluorescent Off-On characteristics were evaluated by theoretical calculations. All probes were selective only towards thiol containing amino acids. Thiol sensing by probes 4 and 6 were much better compared to 5. Probe 4 displayed a better fluorescence response for less hindered thiol (185-, 223- and 156-fold for Hcy, Cys and GSH, respectively), while for probe 6, a higher enhancement in fluorescence was observed with more hindered thiols (180-, 205- and 245-fold for Hcy, Cys and GSH, respectively). The better response to bulkier thiol, GSH by probe 6 was attributed to the steric crowding at the C-4 position and bulkiness of the GSH group which force the succinimide unit to be in a nearly orthogonal conformation. This spatial arrangement was important in reducing the fluorescence quenching ability of the succinimide moiety. The application of probes 4, 5 and 6 was demonstrated by naked eye detection thiols using a 96-well plate system as well as by live-cell imaging. PMID:23364761

Kand, Dnyaneshwar; Kalle, Arunasree Marasanapalli; Talukdar, Pinaki

2013-02-13

371

Selective visual detection of trace trinitrotoluene residues based on dual-color fluorescence of graphene oxide-nanocrystals hybrid probe.  

PubMed

Herein, for the detection of highly explosive 2,4,6-trinitrotoluene (TNT) instantly and on-site, a fluorescence ratiometric probe using a dual-emission nanohybrid has been developed. The nanohybrid comprises blue-colored fluorescent graphene oxide (FGO) being conjugated with red-emitting manganese-doped ZnS nanocrystals (ZnS:Mn NCs), the latter being functionalized with hexamethylenediamine. The blue fluorescence of FGO is insensitive to TNT and is used as an internal reference, whereas the red fluorescence of ZnS:Mn NCs can be selectively quenched by TNT through electron transfer, resulting in a unique red-purple-blue color response as the amount of TNT is increased. Thus, the probe could be used for the quantitative measurement of TNT based on the fluorescence ratiometric method. We demonstrated that the nanohybrid probe exhibited high visual detection sensitivity and reliability in comparison with single-color fluorescence quenching probes. A fluorescence test paper was prepared using the nanohybrid probe and was demonstrated to detect TNT residues directly on various surfaces including rubber, a person's fingers and manila envelopes with a visual detection limit as low as 5.68 ng mm(-2), showing its promising application for security screening. PMID:24667778

Zhang, Kui; Yang, Lei; Zhu, Houjuan; Ma, Fang; Zhang, Zhongping; Wang, Suhua

2014-05-21

372

A new fundamental parameter based calibration procedure for micro X-ray fluorescence spectrometers  

NASA Astrophysics Data System (ADS)

Fundamental parameter based quantification of X-ray fluorescence (XRF) measurement data requires an accurate knowledge of the spectrometer parameters, including the spectral distribution of the excitation radiation. In case of micro-XRF where a polycapillary optic is utilized in the excitation channel this distribution is changed due to the transmission properties of the lens. A new calibration procedure, based on fluorescence data of thin standard samples, was developed to determine the excitation spectrum, i.e., the product of the X-ray tube spectrum and the transmission of the used X-ray optic of a micro-XRF setup. The calibration result was validated by the quantitative analyses of certified multi-element reference standards and shows uncertainties in the order of 2% for main components, 10% for minor elements and 25% for trace elements. The influence of secondary order effects like Coster-Kronig transitions and cascade effects is analyzed and the accuracy of fundamental parameters in common databases is discussed.

Wolff, Timo; Malzer, Wolfgang; Mantouvalou, Ioanna; Hahn, Oliver; Kanngießer, Birgit

2011-02-01

373

Squaraine-based polymer dots with narrow, bright near-infrared fluorescence for biological applications.  

PubMed

This article describes the design and development of squaraine-based semiconducting polymer dots (Pdots) that show large Stokes shifts and narrow-band emissions in the near-infrared (NIR) region. Fluorescent copolymers containing fluorene and squaraine units were synthesized and used as precursors for preparing the Pdots, where exciton diffusion and likely through-bond energy transfer led to highly bright and narrow-band NIR emissions. The resulting Pdots exhibit the emission full width at half-maximum of ?36 nm, which is ?2 times narrower than those of inorganic quantum dots in the same wavelength region (?66 nm for Qdot705). The squaraine-based Pdots show a high fluorescence quantum yield (QY) of 0.30 and a large Stokes shift of ?340 nm. Single-particle analysis indicates that the average per-particle brightness of the Pdots is ?6 times higher than that of Qdot705. We demonstrate bioconjugation of the squaraine Pdots and employ the Pdot bioconjugates in flow cytometry and cellular imaging applications. Our results suggest that the narrow bandwidth, high QY, and large Stokes shift are promising for multiplexed biological detections. PMID:25494172

Wu, I-Che; Yu, Jiangbo; Ye, Fangmao; Rong, Yu; Gallina, Maria Elena; Fujimoto, Bryant S; Zhang, Yong; Chan, Yang-Hsiang; Sun, Wei; Zhou, Xing-Hua; Wu, Changfeng; Chiu, Daniel T

2015-01-14

374

Light-emitting diode and laser fluorescence-based devices in detecting occlusal caries  

NASA Astrophysics Data System (ADS)

The aim of this study was to assess the performance of two light-emitting diode (LED)- and two laser fluorescence-based devices in detecting occlusal caries in vitro. Ninety-seven permanent molars were assessed twice by two examiners using two LED- (Midwest Caries - MID and VistaProof - VP) and two laser fluorescence-based (DIAGNOdent 2095 - LF and DIAGNOdent pen 2190 - LFpen) devices. After measuring, the teeth were histologically prepared and classified according to lesion extension. At D1 the specificities were 0.76 (LF and LFpen), 0.94 (MID), and 0.70 (VP); the sensitivities were 0.70 (LF), 0.62 (LFpen), 0.31 (MID), and 0.75 (VP). At D3 threshold the specificities were 0.88 (LF), 0.87 (LFpen), 0.90 (MID), and 0.70 (VP); the sensitivities were 0.63 (LF and LFpen), 0.70 (MID), and 0.96 (VP). Spearman's rank correlations with histology were 0.56 (LF), 0.51 (LFpen), 0.55 (MID), and 0.58 (VP). Inter- and intraexaminer ICC values were high and varied from 0.83 to 0.90. Both LF devices seemed to be useful auxiliary tools to the conventional methods, presenting good reproducibility and better accuracy at D3 threshold. MID was not able to differentiate sound surfaces from enamel caries and VP still needs improvement on the cut-off limits for its use.

Rodrigues, Jonas A.; Hug, Isabel; Neuhaus, Klaus W.; Lussi, Adrian

2011-10-01

375

Visualizing and Manipulating Temporal Signaling Dynamics with Fluorescence-Based Tools  

PubMed Central

The use of genome-wide proteomic and RNA interference approaches has moved our understanding of signal transduction from linear pathways to highly integrated networks centered on core nodes. However, probing the dynamics of flow of information through such networks remains technically challenging. In particular, how the temporal dynamics of an individual pathway can elicit distinct outcomes in a single cell type and how multiple pathways may interact sequentially or synchronously to influence cell fate remain open questions in many contexts. The development of fluorescence-based reporters and optogenetic regulators of pathway activity enables the analysis of signaling in living cells and organisms with unprecedented spatiotemporal resolution and holds the promise of addressing these key questions. We present a brief overview of the evidence for the importance of temporal dynamics in cellular regulation, introduce these fluorescence-based tools, and highlight specific studies that leveraged these tools to probe the dynamics of information flow through signaling networks. In particular, we highlight two studies in Caenorhabditis elegans sensory neurons and cultured mammalian cells that demonstrate the importance of signal dynamics in determining cellular responses. PMID:24692594

Doupé, David P.; Perrimon, Norbert

2015-01-01

376

An Affinity-Based Fluorescence Polarization Assay for Protein Tyrosine Phosphatases  

PubMed Central

Protein tyrosine phosphatases (PTPs) are important signaling enzymes that control such fundamental processes as proliferation, differentiation, survival/apoptosis, as well as adhesion and motility. Potent and selective PTP inhibitors serve not only as powerful research tools, but also as potential therapeutics against a variety illness including cancer and diabetes. PTP activity-based assays are widely used in high throughput screening (HTS) campaigns for PTP inhibitor discovery. These assays suffer from a major weakness, in that the reactivity of the active site Cys can cause serious problems as highly reactive oxidizing and alkylating agents may surface as hits. We describe the development of a fluorescence polarization (FP)-based displacement assay that makes the use of an active site Cys to Ser mutant PTP (e.g., PTP1B/C215S) that retains the wild type binding affinity. The potency of library compounds is assessed by their ability to compete with the fluorescently labeled active site ligand for binding to the Cys to Ser PTP mutant. Finally, the substitution of the active site Cys by a Ser renders the mutant PTP insensitive to oxidation and alkylation and thus will likely eliminate “false” positives due to modification of the active site Cys that destroy the phosphatase activity. PMID:17532513

Zhang, Sheng; Chen, Lan; Kumar, Sanjai; Wu, Li; Lawrence, David S.; Zhang, Zhong-Yin

2007-01-01

377

Screening for Small Molecules' Bilayer-Modifying Potential Using a Gramicidin-Based Fluorescence Assay  

PubMed Central

Abstract Many drugs and other small molecules used to modulate biological function are amphiphiles that adsorb at the bilayer/solution interface and thereby alter lipid bilayer properties. This is important because membrane proteins are energetically coupled to their host bilayer by hydrophobic interactions. Changes in bilayer properties thus alter membrane protein function, which provides a possible mechanism for “off-target” drug effects. We have previously shown that channels formed by the linear gramicidins are suitable probes for changes in lipid bilayer properties, as experienced by bilayer-spanning proteins. We now report a gramicidin-based fluorescence assay for changes in bilayer properties. The assay is based on measuring the time course of fluorescence quenching in fluorophore-loaded large unilamellar vesicles, due to entry of a gramicidin channel-permeable quencher. The method is scalable and suitable for both mechanistic studies and high-throughput screening for bilayer-perturbing, potential off-target effects, which we illustrate using capsaicin (Cap) and other compounds. PMID:20233091

Ingólfsson, Helgi I.

2010-01-01

378

Fluorescence-based resource for semiautomated genomic analyses using microsatellite markers  

SciTech Connect

To facilitate the practical application of highly-efficient semiautomated methods for general application in genomic analyses, the authors have developed a fluorescence-based microsatellite marker resource. Ninety highly polymorphic microsatellite markers were combined to provide a rapid, accurate, and highly efficient initial genome-wide screening system. These markers are spaced on average every 33 cM, with a mean heterozygosity of 81% (range 65-94%), covering 22 autosomes and the X and Y chromosomes. Less than 10% of the genome lies beyond 20 cM of the nearest marker. Since this genomic analysis system is fully compatible with automated fragment analyzers using simultaneous four-color fluorescence-based detection systems, the 5 groups of 18 markers can be detected concurrently. This multiplex detection provides a throughput of 1944 genotypes daily per instrument. This system will be highly beneficial in a number of clinical and research applications including linkage, cancer genetics, forensics, and cytogenetics. 16 refs., 1 fig., 2 tabs.

Levitt, R.C.; Kiser, M.B.; Dragwa, C. [Johns Hopkins Medical Institutions, Baltimore, MD (United States)] [and others] [Johns Hopkins Medical Institutions, Baltimore, MD (United States); and others

1994-11-15

379

Diagnosis of breast cancer using fluorescence and diffuse reflectance spectroscopy: a Monte-Carlo-model-based approach  

PubMed Central

We explore the use of Monte-Carlo-model-based approaches for the analysis of fluorescence and diffuse reflectance spectra measured ex vivo from breast tissues. These models are used to extract the absorption, scattering, and fluorescence properties of malignant and nonmalignant tissues and to diagnose breast cancer based on these intrinsic tissue properties. Absorption and scattering properties, including ?-carotene concentration, total hemoglobin concentration, hemoglobin saturation, and the mean reduced scattering coefficient are derived from diffuse reflectance spectra using a previously developed Monte Carlo model of diffuse reflectance. A Monte Carlo model of fluorescence described in an earlier manuscript was employed to retrieve the intrinsic fluorescence spectra. The intrinsic fluorescence spectra were decomposed into several contributing components, which we attribute to endogenous fluorophores that may present in breast tissues including collagen, NADH, and retinol/vitamin A. The model-based approaches removes any dependency on the instrument and probe geometry. The relative fluorescence contributions of individual fluorescing components, as well as ?-carotene concentration, hemoglobin saturation, and the mean reduced scattering coefficient display statistically significant differences between malignant and adipose breast tissues. The hemoglobin saturation and the reduced scattering coefficient display statistically significant differences between malignant and fibrous/benign breast tissues. A linear support vector machine classification using (1) fluorescence properties alone, (2) absorption and scattering properties alone, and (3) the combination of all tissue properties achieves comparable classification accuracies of 81 to 84% in sensitivity and 75 to 89% in specificity for discriminating malignant from nonmalignant breast tissues, suggesting each set of tissue properties are diagnostically useful for the discrimination of breast malignancy. PMID:18601560

Zhu, Changfang; Palmer, Gregory M.; Breslin, Tara M.; Harter, Josephine; Ramanujam, Nirmala

2009-01-01

380

Diarylethene based fluorescent switchable probes for the detection of amyloid-? pathology in Alzheimer's disease.  

PubMed

Two fluorescent switchable diarylethene derivatives which exhibit high affinity for amyloid-? aggregates with the increase of fluorescence intensity were reported. Moreover, the probes show excellent photochromic and anti-photobleaching properties both in vitro and in vivo. PMID:25384304

Lv, Guanglei; Cui, Baiping; Lan, Haichuang; Wen, Ying; Sun, Anyang; Yi, Tao

2015-01-01

381

Substituent effects on the turn-on kinetics of rhodamine-based fluorescent pH probes.  

PubMed

Fluorescent turn-on probes based on a rhodamine spirolactam (RSL) structure have recently become a popular means of detecting pH, metal ions, and other analytes of interest. RSLs are colorless and non-fluorescent until the target analyte induces opening of the spirocyclic ring system, revealing the fully conjugated and highly fluorescent rhodamine dye. Among RSLs opened by acid, we have observed wide variation in the kinetics of the fluorescence turn-on process such that some probes would not be usable in situations where a rapid reading is desired or the pH fluctuates temporally. Herein we present a systematic investigation of the fluorescence turn-on kinetics of RSLs to probe the hypothesis that the reaction rates are influenced by the electronic properties of the spirolactam ring system. A series of 8 aniline-derived RSLs with para substituents ranging from electron-donating to electron-withdrawing was prepared from rhodamine B. The fluorescence turn-on rates are observed to increase by a factor of four as the substituent is tuned from methoxy to nitro. This effect is explained in terms of the destabilization of the reaction intermediate by the substituent. As the reaction rates increase across the series, a concomitant increase in fluorescence intensity is also observed. This result is attributed to an increase in the concentration of the fluorescent form of the dye and is consistent with the expected equilibrium properties of this system. These findings are applied to the design of a faster-reacting and more intensely fluorescent RSL pH probe. PMID:24287714

Czaplyski, William L; Purnell, Grace E; Roberts, Courtney A; Allred, Rebecca M; Harbron, Elizabeth J

2014-01-21

382

A Red Cy3-Based Biarsenical Fluorescent Probe Targeted to a Complementary Binding Peptide  

SciTech Connect

Small-molecule biarsenical multiuse affinity probes (MAPs) FlAsH and ReAsH,1,2 in conjunction with complementary protein tags, are important new tools for analyzing cellular function through live-cell imaging,3,4 targeted protein inactivation,5 and the measurement of protein dynamics and binding.6 In addition, MAPs serve as affinity reagents for isolating intact protein complexes for complementary structural measurements.7 These first-generation MAPs bind to a tetracoordinate arsenic group (TAG) binding motif (i.e., CCXXCC or FlAsHTAG) genetically engineered onto a protein of interest. They are superior to other targeted labeling strategies (such as the Halo-tag, the SNAP tag, and fluorescent proteins) in that the small peptide tag does not disrupt protein protein interactions nor perturb the correct trafficking of tagged proteins.8,9 The conserved interatomic distance (*6 Å) between the two arsenic moieties in FlAsH and ReAsH complicates the selective labeling of multiple proteins with different reporters. To overcome these limitations, we have synthesized a new biarsenical MAP (i.e., AsCy3) based on Cy3, a member of the cyanine dye family, whose well-recognized brightness and photostability facilitate their utility in single-molecule measurements. The large interatomic distance between the two arsenics in AsCy3 (*14.5 Å) coupled with the identification of a complementary high-affinity binding sequence CCKAEAACC (Cy3TAG) permits the simultaneous application of both AsCy3 and FlAsH to selectively label their respective binding TAGs in different proteins. In addition, the fluorescence of FlAsH overlaps with the absorption of AsCy3, which can act as an acceptor of fluorescence resonance energy transfer (FRET) to allow ratiometric measurements of protein association.

Cao, Haishi; Xiong, Yijia; Wang, Ting; Chen, Baowei; Squier, Thomas C.; Mayer, M. Uljana

2007-06-22

383

Ion track reconstruction in 3D using alumina-based fluorescent nuclear track detectors  

NASA Astrophysics Data System (ADS)

Fluorescent nuclear track detectors (FNTDs) based on Al2O3: C, Mg single crystal combined with confocal microscopy provide 3D information on ion tracks with a resolution only limited by light diffraction. FNTDs are also ideal substrates to be coated with cells to engineer cell-fluorescent ion track hybrid detectors (Cell-Fit-HD). This radiobiological tool enables a novel platform linking cell responses to physical dose deposition on a sub-cellular level in proton and heavy ion therapies. To achieve spatial correlation between single ion hits in the cell coating and its biological response the ion traversals have to be reconstructed in 3D using the depth information gained by the FNTD read-out. FNTDs were coated with a confluent human lung adenocarcinoma epithelial (A549) cell layer. Carbon ion irradiation of the hybrid detector was performed perpendicular and angular to the detector surface. In situ imaging of the fluorescently labeled cell layer and the FNTD was performed in a sequential read-out. Making use of the trajectory information provided by the FNTD the accuracy of 3D track reconstruction of single particles traversing the hybrid detector was studied. The accuracy is strongly influenced by the irradiation angle and therefore by complexity of the FNTD signal. Perpendicular irradiation results in highest accuracy with error of smaller than 0.10°. The ability of FNTD technology to provide accurate 3D ion track reconstruction makes it a powerful tool for radiobiological investigations in clinical ion beams, either being used as a substrate to be coated with living tissue or being implanted in vivo.

Niklas, M.; Bartz, J. A.; Akselrod, M. S.; Abollahi, A.; Jäkel, O.; Greilich, S.

2013-09-01

384

A ratiometric fluorescent probe for zinc ions based on the quinoline fluorophore  

Microsoft Academic Search

A ratiometric fluorescent zinc probe 1 of carboxamidoquinoline with a carboxylic acid group was designed and synthesised. Probe 1 exhibits high selectivity for sensing Zn; about a 13-fold increase in fluorescence emission intensity and an 82?nm red-shift of fluorescence emission are observed upon binding Zn in EtOH\\/H2O (1?:?1, V\\/V) solution. The ratiometric fluorescence response is attributed to the 1?:?1 complex

Qiu-Juan Ma; Xiao-Bing Zhang; Zhi-Xiang Han; Bo Huang; Qin Jiang; Guo-Li Shen; Ru-Qin Yu

2011-01-01

385

[2] Fluorescence-sensing methods  

Microsoft Academic Search

Novel approaches to sensor design, based on the use of an internal standard with appropriate spectral properties, provide new possibilities for designing simple devices for fluorescence sensing. Detection of combined emission from the reference and an analyte-sensitive fluorophore has been achieved in numerous measurements in cuvettes,7–10,42,43 tissues,46,47 and high-throughput formats.48 These methods have been used with a long-lifetime reference to

Zygmunt Gryczynski; Ignacy Gryczynski; Joseph R. Lakowicz

2003-01-01

386

Determination of trace aluminum by fluorescence quenching method based on catalysis of potassium chlorate oxidizing alizarin red  

NASA Astrophysics Data System (ADS)

A new method for the determination of trace aluminum has been proposed. It is based on the fact that alizarin red can emit strong and stable fluorescence at 80 °C for 30 min and Al 3+ can effectively catalyze potassium chlorate oxidizing alizarin red to form non-fluorescence complex which cause the fluorescence quenching. The linear dynamic range of this method is 0.040-4.00 ng l -1 with a detection limit of 5.3 pg l -1. The regression equation can be expressed as ? If = 8.731 + 21.73 c (ng l -1), with the correlation coefficient r = 0.9992 ( n = 6). This sensitive, rapid and accurate method has been applied to the determination of trace aluminum(III) in human hair and tea samples successfully. What is more, the mechanism of catalyzing potassium chlorate oxidizing alizarin red by the fluorescence quenching method is also discussed.

Shao-Qin, Lin; Xuan, Lin; Shi-Rong, Hu; Li-Qing, Zeng; Yan, Wang; Li, Chen; Jia-Ming, Liu; Long-Di, Li

2005-11-01

387

Review of Fluorescence-Based Velocimetry Techniques to Study High-Speed Compressible Flows  

NASA Technical Reports Server (NTRS)

This paper reviews five laser-induced fluorescence-based velocimetry techniques that have been used to study high-speed compressible flows at NASA Langley Research Center. The techniques discussed in this paper include nitric oxide (NO) molecular tagging velocimetry (MTV), nitrogen dioxide photodissociation (NO2-to-NO) MTV, and NO and atomic oxygen (O-atom) Doppler-shift-based velocimetry. Measurements of both single-component and two-component velocity have been performed using these techniques. This paper details the specific application and experiment for which each technique has been used, the facility in which the experiment was performed, the experimental setup, sample results, and a discussion of the lessons learned from each experiment.

Bathel, Brett F.; Johansen, Criag; Inman, Jennifer A.; Jones, Stephen B.; Danehy, Paul M.

2013-01-01

388

High Repetition Rate, LINAC-Based Nuclear Resonance Fluorescence FY 2008 Final Report  

SciTech Connect

This summarizes the first year of a multi-laboratory/university, multi-year effort focusing on high repetition rate, pulsed LINAC-based nuclear resonance fluorescence (NRF) measurements. Specifically, this FY2008 effort centered on experimentally assessing NRF measurements using pulsed linear electron accelerators, operated at various repetition rates, and identifying specific detection requirements to optimize such measurements. Traditionally, interest in NRF as a detection technology, which continues to receive funding from DHS and DOE/NA-22, has been driven by continuous-wave (CW), Van de Graff-based bremsstrahlung sources. However, in addition to the relatively sparse present-day use of Van de Graff sources, only limited NRF data from special nuclear materials has been presented; there is even less data available regarding shielding effects and photon source optimization for NRF measurements on selected nuclear materials.

Scott M Watson; Mathew T Kinlaw; James L Jones; Alan W. Hunt; Glen A. Warren

2008-12-01

389

Mesh-based Monte Carlo method in time-domain widefield fluorescence molecular tomography  

PubMed Central

Abstract. We evaluated the potential of mesh-based Monte Carlo (MC) method for widefield time-gated fluorescence molecular tomography, aiming to improve accuracy in both shape discretization and photon transport modeling in preclinical settings. An optimized software platform was developed utilizing multithreading and distributed parallel computing to achieve efficient calculation. We validated the proposed algorithm and software by both simulations and in vivo studies. The results establish that the optimized mesh-based Monte Carlo (mMC) method is a computationally efficient solution for optical tomography studies in terms of both calculation time and memory utilization. The open source code, as part of a new release of mMC, is publicly available at http://mcx.sourceforge.net/mmc/. PMID:23224008

Chen, Jin; Fang, Qianqian; Intes, Xavier

2012-01-01

390

Total internal reflection-based module for fluorescence and absorbance detection  

NASA Astrophysics Data System (ADS)

We present a miniaturized polymer-based micro-optical detection unit for ultraviolet and visible laser-induced fluorescence (LIF) and absorbance (ABS) analysis with an interaction length of 3 mm. We use nonsequential optical ray tracing simulations to model the system and to optimize its performance with respect to optical efficiency and system complexity. The design features a compact optical system combining total internal reflection (TIR) mirrors and refractive optics. The detection module is prototyped with deep proton writing in 2-mm-thick polymethylmethacrylate and quantitatively characterized using a three-dimensional coordinate measurement machine. We demonstrate the proof-of-concept of this TIR mirror-based module for coumarin 480 obtaining limits of detection of 50 pM and 500 nM for LIF and ABS, respectively.

Verschooten, Tom; Ottevaere, Heidi; Vervaeke, Michael; Van Erps, Jürgen; Thienpont, Hugo

2014-07-01

391

Enhanced fluorescence of chitosan based on size change of micelles and application to directly selective detecting Fe³? in human serum.  

PubMed

In this paper, we have developed an approach to significantly enhance fluorescence of chitosan by simply heated the inherently low fluorescent chitosan aqueous solution. Enhanced blue fluorescence of chitosan solution was observed as originated from the formation of small size of chitosan micelle after long time heated. The fluorescence of chitosan micelles was quenched and recovered when Fe³? ions were combined and released from chitosan micelles. Therefore, chitosan without modification of functional groups can recognize Fe³? with very high selectivity. As a result, a new fluorescence sensor for sensitively detecting Fe³? ion based on the change of chitosan micelles sizes was subsequently fabricated. This enhanced fluorescence enables the chitosan sensor to be sensitive to low concentrations of Fe³?, and it is linear responsive in the range of 1.96×10?? to 2.00×10?? M. Importantly, this novel sensor may be applied in human serum for direct detection of Fe³? ion without sample pretreatment. Analysis of 5 samples of human serum shows that the average concentration of Fe³? is 26.95 ?M, which is consistent with the results determined by other methods. Moreover, the advantage of chitosan-based assay is that Fe³? rather than Fe²? in human serum can be directly measured, avoiding costly, time-consuming and complex process. PMID:23261686

Huang, Haowen; Liu, Fang; Chen, Shenna; Zhao, Qian; Liao, Bo; Long, Yunfei; Zeng, Yunlong; Xia, Xiaodong

2013-04-15

392

Design and synthesis of a novel fluorescent protein probe for easy and rapid electrophoretic gel staining by using a commonly available UV-based fluorescent imaging system.  

PubMed

A new fluorescent molecular probe, methyl 3-(3,5-bis((bis(pyridin-2-ylmethyl)amino)-methyl)-4-hydroxyphenyl)-2-(5-(dimethylamino)naphthalene-1-sulfonamido) propanoate, dizinc(II) chloride salt (Dansyl-1-Zn(II)), which possesses Zn(II) complexes and a dansyl group, was designed and synthesized to enable the detection of proteins in solution and in high-throughput electrophoresis by using a UV-based detection system. Dansyl-1-Zn(II) exhibited weak fluorescence in the absence of proteins and strong green fluorescence at approximately 510 nm in the presence of BSA upon irradiation with light at a wavelength of 345 nm. Compared with conventional protocols for in-gel SDS-PAGE protein staining (e.g. silver staining, SYPRO Ruby, and Oriole), the operating times of which range from 90 min to overnight, Dansyl-1-Zn(II) allowed 1-step protein staining (SDS-PAGE ?Staining ?Detection) and shortened the operating time (35 min) with high sensitivity (LOD: 1 ng or less) under 312-nm or 365-nm light excitation with orange or red emission filters, respectively. Moreover, Dansyl-1-Zn(II) was successfully applied to protein identification by MS via in-gel tryptic digestion, Western blotting, and Native-PAGE. Accordingly, Dansyl-1-Zn(II) may facilitate highly sensitive and high-throughput protein detection, and it may be widely applicable as a convenient tool in various scientific and medical fields. PMID:23801451

Suzuki, Yoshio; Takagi, Nobuyuki; Sano, Takuma; Chimuro, Tomoyuki

2013-09-01

393

Simple far-field radiative thermal rectifier using Fabry-Perot cavities based infrared selective emitters.  

PubMed

We present a thermal rectification device concept based on far-field radiative exchange between two selective emitters. Rectification is achieved due to a large contrast between the two selective emitters' thermo-optical properties. A simple device constituted by two multilayer samples made of metallic (Au) and semiconductor (Si and HDSi) thin films is proposed. This device shows a rectification ratio increasing with temperature up to 19% for a temperature difference of ?T=370??K. Further optimization would allow larger rectification values. The presented results might be useful for energy conversion devices, engineering of smart radiative coolers/insulators, and development of thermal logical circuits. PMID:24922424

Nefzaoui, E; Drevillon, J; Ezzahri, Y; Joulain, K

2014-06-01

394

Analysis of the THz response of a simple periodic graphite-based structure.  

PubMed

We report the observation of the dichroism effect in simple wire grid structures made of graphite on a paper substrate, i.e. we investigate the feasibility of drawing polarizers for the THz band using conventional graphite-based lead pencils. The displacement of the maximum frequency of the selective absorption phenomenon by varying the wire pitch hints at a polarizing behavior. Measurements of the maximum and minimum of transmission efficiency, extinction ratio and degree of polarization are carried out with a transmission fiber THz-TDS setup. Experimental results show a 9 dB extinction ratio for an inexpensive (<1$) home-made component. PMID:25606945

Colleoni, M P M; Vidal, B

2014-12-01

395

A Simple Quality Assessment Index for Stereoscopic Images Based on 3D Gradient Magnitude  

PubMed Central

We present a simple quality assessment index for stereoscopic images based on 3D gradient magnitude. To be more specific, we construct 3D volume from the stereoscopic images across different disparity spaces and calculate pointwise 3D gradient magnitude similarity (3D-GMS) along three horizontal, vertical, and viewpoint directions. Then, the quality score is obtained by averaging the 3D-GMS scores of all points in the 3D volume. Experimental results on four publicly available 3D image quality assessment databases demonstrate that, in comparison with the most related existing methods, the devised algorithm achieves high consistency alignment with subjective assessment. PMID:25133265

Wang, Shanshan; Shao, Feng; Li, Fucui; Yu, Mei; Jiang, Gangyi

2014-01-01

396

Fluorescence enhancement in a polymer-based photonic-crystal biosensor  

NASA Astrophysics Data System (ADS)

Detecting labeled or naturally-fluorescent biomolecules at very low concentrations is of a significant importance for health sciences, agricultural sciences, and security-related applications. Photonic crystals (PhC) are microfabricated nano-structures of periodic dielectric permittivity in one, two, or three dimensions that possess unique light manipulation properties. These include the ability to localize electromagnetic waves at particular PhC lattice locations. Ultra-sensitive detection using thin-film PhC structures fabricated in semiconductor materials has been demonstrated in both "active" and "passive" modalities. In the active modality, the adsorption of target molecules to the PhC surface causes a refractive index change that is translated into reflectance or transmission peak shifts. The passive modality demonstrated by our group utilizes the PhC structure to observe enhanced fluorescent emission within resonant defect cavities in a 2D PhC lattice. Integrating these semiconductor-based PhC structures with biocompatible microfluidic channels is a challenging task that can significantly increase the final cost of the sensor system. We demonstrate here soft lithographic nanomolding techniques for polymer-based PhC structures that are easily integrated with microfluidic channels to provide a portable means of biosensing. A TE bandgap of 2.857% for a 2D PhC fabricated in poly(dimethylsiloxane) (PDMS) will allow these lattices to become core structures in PhC-based biosensors incorporating both active and passive modalities. Modeling and initial optical characterization results of the Si- and PDMS-based PhC biosensor will also be presented.

Hamza, Bashar; Kadiyala, Anand; Kilemi, Caroline; Liu, Yuxin; Dawson, Jeremy

2011-03-01

397

Enhanced Fluorescence by Controlled Surface Roughness of Plastic Biochip  

NASA Astrophysics Data System (ADS)

Fluoroimmunoassay is one of the protein detection methods in which the most critical parameter is fluorescence intensity as it determines the sensitivity of the analysis. In this study, cyclic olefin copolymer (COC) based plastic biochips of various thicknesses were fabricated from 304 SS (Stainless Steel) molds using imprinting technique. The effect of surface roughness of COC biochip on the enhancement of fluorescence intensity was investigated. The fluorescence intensity reached the maximum value at optimum value of surface roughness without significantly affecting the auto-fluorescence value. The process proposed in this technique is simple, low cost yet highly sensitive for protein detection.

Kim, Dong-Jin; Lee, Jung-Hwan; Cho, Si-Hyeong; Rizwan, Muhammad; Prasanna Venkatesh, R.; Guen Chung, Bong; Park, Jin-Goo

2011-06-01

398

A Simple and Fast Hypervolume Indicator-Based Multiobjective Evolutionary Algorithm.  

PubMed

To find diversified solutions converging to true Pareto fronts (PFs), hypervolume (HV) indicator-based algorithms have been established as effective approaches in multiobjective evolutionary algorithms (MOEAs). However, the bottleneck of HV indicator-based MOEAs is the high time complexity for measuring the exact HV contributions of different solutions. To cope with this problem, in this paper, a simple and fast hypervolume indicator-based MOEA (FV-MOEA) is proposed to quickly update the exact HV contributions of different solutions. The core idea of FV-MOEA is that the HV contribution of a solution is only associated with partial solutions rather than the whole solution set. Thus, the time cost of FV-MOEA can be greatly reduced by deleting irrelevant solutions. Experimental studies on 44 benchmark multiobjective optimization problems with 2-5 objectives in platform jMetal demonstrate that FV-MOEA not only reports higher hypervolumes than the five classical MOEAs (nondominated sorting genetic algorithm II (NSGAII), strength Pareto evolutionary algorithm 2 (SPEA2), multiobjective evolutionary algorithm based on decomposition (MOEA/D), indicator-based evolutionary algorithm, and S-metric selection based evolutionary multiobjective optimization algorithm (SMS-EMOA)), but also obtains significant speedup compared to other HV indicator-based MOEAs. PMID:25474815

Jiang, Siwei; Zhang, Jie; Ong, Yew-Soon; Zhang, Allan N; Tan, Puay Siew

2014-12-01

399

Mesh-based Monte Carlo code for fluorescence modeling in complex tissues with irregular boundaries  

NASA Astrophysics Data System (ADS)

There is a growing need for the development of computational models that can account for complex tissue morphology in simulations of photon propagation. We describe the development and validation of a user-friendly, MATLAB-based Monte Carlo code that uses analytically-defined surface meshes to model heterogeneous tissue geometry. The code can use information from non-linear optical microscopy images to discriminate the fluorescence photons (from endogenous or exogenous fluorophores) detected from different layers of complex turbid media. We present a specific application of modeling a layered human tissue-engineered construct (Ex Vivo Produced Oral Mucosa Equivalent, EVPOME) designed for use in repair of oral tissue following surgery. Second-harmonic generation microscopic imaging of an EVPOME construct (oral keratinocytes atop a scaffold coated with human type IV collagen) was employed to determine an approximate analytical expression for the complex shape of the interface between the two layers. This expression can then be inserted into the code to correct the simulated fluorescence for the effect of the irregular tissue geometry.

Wilson, Robert H.; Chen, Leng-Chun; Lloyd, William; Kuo, Shiuhyang; Marcelo, Cynthia; Feinberg, Stephen E.; Mycek, Mary-Ann

2011-07-01

400

High Repetition Rate, LINAC-based Nuclear Resonance Fluorescence FY 2009 Final Report  

SciTech Connect

Nuclear Resonance Fluorescence (NRF), which is possible for nuclei with atomic numbers greater than helium (Z=2), occurs when a nuclear level is excited by resonant absorption of a photon and subsequently decays by reemission of a photon. The excited nuclear states can become readily populated, provided the incident photon’s energy is within the Doppler-broadened width of the energy level being excited. Utilizing continuous energy photon spectra, as is characteristic of a bremsstrahlung photon beam, as the inspection source, ensures that at least some fraction of the impinging beam will contribute to the population of the excited energy levels in the material of interest. Upon de-excitation, either to the ground state or to a lower-energy excited state, the emitted fluorescence photon’s energy will correspond to the energy difference between the excited state and the state to which it decays. As each isotope inherently contains unique nuclear energy levels, the NRF states for each isotope are also unique. By exploiting this phenomenon, NRF photon detection provides a well-defined signature for identifying the presence of individual nuclear species. This report summarizes the second year (Fiscal Year [FY] 2009) of a collaborative research effort between Idaho National Laboratory, Idaho State University’s Idaho Accelerator Center, and Pacific Northwest National Laboratory. This effort focused on continuing to assess and optimize NRF-based detection techniques utilizing a slightly modified, commercially available, pulsed medical electron accelerator.

Mathew Kinlaw; Scott Watson; James Johnson; Alan Hunt; Heather Seipel; Edward Reedy

2009-10-01

401

Isotopic imaging via nuclear resonance fluorescence with laser-based Thomson radiation  

DOEpatents

The present invention utilizes novel laser-based, high-brightness, high-spatial-resolution, pencil-beam sources of spectrally pure hard x-ray and gamma-ray radiation to induce resonant scattering in specific nuclei, i.e., nuclear resonance fluorescence. By monitoring such fluorescence as a function of beam position, it is possible to image in either two dimensions or three dimensions, the position and concentration of individual isotopes in a specific material configuration. Such methods of the present invention material identification, spatial resolution of material location and ability to locate and identify materials shielded by other materials, such as, for example, behind a lead wall. The foundation of the present invention is the generation of quasimonochromatic high-energy x-ray (100's of keV) and gamma-ray (greater than about 1 MeV) radiation via the collision of intense laser pulses from relativistic electrons. Such a process as utilized herein, i.e., Thomson scattering or inverse-Compton scattering, produces beams having diameters from about 1 micron to about 100 microns of high-energy photons with a bandwidth of .DELTA.E/E of approximately 10E.sup.-3.

Barty, Christopher P. J. (Hayward, CA); Hartemann, Frederic V. (San Ramon, CA); McNabb, Dennis P. (Alameda, CA); Pruet, Jason A. (Brentwood, CA)

2009-07-21

402

Self-assembled DNA hydrogel as switchable material for aptamer-based fluorescent detection of protein.  

PubMed

The methodology based on target-responsive structural switching is powerful in bioanalysis with the controllability and sensitivity. In this paper, an aptamer-functionalized DNA hydrogel was designed as a specifically target-responsive switchable material for protein detection. This pure DNA hydrogel was constructed by using a Y-shaped DNA and an aptamer linker through a DNA self-assembly without synthetic polymer backbone. With use of thrombin as the model analyte, the DNA hydrogel was first applied to visual detection with the entrapped Au nanoparticles (AuNPs) as indicating agent. Furthermore, the positively charged quantum dots (QDs) as the fluorophore were synthesized by using polyethyleneimine (PEI) as wrapper and characterized with spectroscopy, transmission electron micrograph, ? potential, and dynamic laser scattering techniques. Along with a gel-to-sol transition in the presence of the target, the released negatively charged AuNPs from the hydrogel could approach the positively charged QDs. Due to the electrostatic interaction, fluorescence resonance energy transfer between PEI-QDs and AuNPs therefore occurred and quenched the fluorescence signal for the sensitive detection of thrombin. This assay for the detection of thrombin showed a good linear relationship in a range of 0.075 to 12.5 ?M with a detection limit of 67 nM at 3?, and demonstrated excellent feasibility in complex serum matrixes. The biocompatible DNA hydrogel provides a universal switchable material for signal transduction and significantly demonstrates proof-of-concept for the detection of proteins. PMID:24138007

Zhang, Lei; Lei, Jianping; Liu, Lin; Li, Changfeng; Ju, Huangxian

2013-11-19

403

Hyperbranched polyester-based fluorescent probe for histone deacetylase via aggregation-induced emission.  

PubMed

Aberrant expression of histone deacetylases (HDACs) is related to various types of cancer and is associated with increased proliferation of tumor cells. Hence, the detection of HDAC activities is of great significance for medical sciences as well as biological diagnostics. Herein, we report a hyperbranched polyester-based one-step fluorescent assay for HDAC. This assay system consists of two water-soluble components: the hyperbranched polyester coupled with the acetylated lysine groups (H40-Lys(Ac)) and the negatively charged TPE derivative bearing two sulfonic acid groups (TPE-2SO3(-)). HDAC triggers the deacetylation of H40-Lys(Ac), thereby turning the electroneutral polymer into the positively charged one. Consequently, complexation occurs between the positively charged polymer and the negatively charged TPE-2SO3(-), thereby leading to the formation of nanoaggregates due to electrostatic interaction. Eventually, the fluorescence enhancement as a result of AIE effect is achieved. This assay system is operable in aqueous media with very low detection limit of 25 ng/mL. The system is capable of detecting HDAC in such biological fluid as serum, and this strategy may provide a new and effective approach for enzyme assay. PMID:24251690

Yu, Changmin; Wu, Yinglong; Zeng, Fang; Li, Xizhen; Shi, Jianbin; Wu, Shuizhu

2013-12-01

404

A highly selective fluorescent probe for Cu2+ based on rhodamine B derivative.  

PubMed

A new fluorescent probe 1 for Cu(2+) based on a rhodamine B derivative was designed and synthesized. Probe 1 displays high sensitivity toward Cu(2+) and about a 37-fold increase in fluorescence emission intensity is observed upon the addition of 10 equiv. Cu(2+) in 50% water/ethanol buffered at pH 7.10. Besides, upon binding Cu(2+) a remarkable color change from colorless to pink was easily observed by the naked eyes. The reversible dual chromo- and fluorogenic response toward Cu(2+) is likely due to the chelation-induced ring-opening of rhodamine spirolactam. The linear response range covers a concentration range of Cu(2+) from 8.0×10(-7) to 1.0×10(-4) mol/L and the detection limit is 3.0×10(-7) mol/L. Except Co(2+), the probe exhibits high selectivity for Cu(2+) over a large number of cations such as alkaline, alkaline earth and transitional metal ions. The accuracy and precision of the method were evaluated by the analysis of the standard reference material, copper in water (1.0 mol/L HNO3). The proposed probe has been used for direct measurement of Cu(2+) content in river water samples and imaging of Cu(2+) in living cells with satisfying results, which further demonstrates its value of practical applications in environmental and biological systems. PMID:24508880

Xu, Junhong; Hou, Yimin; Ma, Qiujuan; Wu, Xuefen; Feng, Suxiang; Zhang, Juan; Shen, Youming

2014-04-24

405

Identification of Adiponectin Receptor Agonist Utilizing a Fluorescence Polarization Based High Throughput Assay  

PubMed Central

Adiponectin, the adipose-derived hormone, plays an important role in the suppression of metabolic disorders that can result in type 2 diabetes, obesity, and atherosclerosis. It has been shown that up-regulation of adiponectin or adiponectin receptor has a number of therapeutic benefits. Given that it is hard to convert the full size adiponectin protein into a viable drug, adiponectin receptor agonists could be designed or identified using high-throughput screening. Here, we report on the development of a two-step screening process to identify adiponectin agonists. First step, we developed a high throughput screening assay based on fluorescence polarization to identify adiponectin ligands. The fluorescence polarization assay reported here could be adapted to screening against larger small molecular compound libraries. A natural product library containing 10,000 compounds was screened and 9 hits were selected for validation. These compounds have been taken for the second-step in vitro tests to confirm their agonistic activity. The most active adiponectin receptor 1 agonists are matairesinol, arctiin, (-)-arctigenin and gramine. The most active adiponectin receptor 2 agonists are parthenolide, taxifoliol, deoxyschizandrin, and syringin. These compounds may be useful drug candidates for hypoadiponectin related diseases. PMID:23691032

Sun, Yiyi; Zang, Zhihe; Zhong, Ling; Wu, Min; Su, Qing; Gao, Xiurong; Zan, Wang; Lin, Dong; Zhao, Yan; Zhang, Zhonglin

2013-01-01

406

Rapid and quantitative detection of zoonotic influenza A virus infection utilizing coumarin-derived dendrimer-based fluorescent immunochromatographic strip test (FICT).  

PubMed

Great efforts have been made to develop robust signal-generating fluorescence materials which will help in improving the rapid diagnostic test (RDT) in terms of sensitivity and quantification. In this study, we developed coumarin-derived dendrimer-based fluorescent immunochromatographic strip test (FICT) assay with enhanced sensitivity as a quantitative diagnostic tool in typical RDT environments. The accuracy of the proposed FICT was compared with that of dot blot immunoassay techniques and conventional RDTs. Through conjugation of coumarin-derived dendrimers with latex beads, fluorescent emission covering broad output spectral ranges was obtained which provided a distinct advantage of easy discrimination of the fluorescent emission of the latex beads with a simple insertion of a long-pass optical filter away from the excitation wavelength. The newly developed FICT assay was able to detect 100 ng/10 ?L of influenza A nucleoprotein (NP) antigen within 5 minutes, which corresponded to 2.5-fold higher sensitivity than that of the dot blot immunoassay or conventional RDTs. Moreover, the FICT assay was confirmed to detect at least four avian influenza A subtypes (H5N3, H7N1, H7N7, and H9N2). On applying the FICT to the clinical swab samples infected with respiratory viruses, our FICT assay was confirmed to differentiate influenza H1N1 infection from other respiratory viral diseases. These data demonstrate that the proposed FICT assay is able to detect zoonotic influenza A viruses with a high sensitivity, and it enables the quantitation of the infection intensity by providing the numerical diagnostic values; thus demonstrating enhanced detectability of influenza A viruses. PMID:25285172

Yeo, Seon-Ju; Huong, Dinh Thi; Hong, Nguyen Ngoc; Li, Chun-Ying; Choi, Kyunghan; Yu, Kyoungsik; Choi, Du-Young; Chong, Chom-Kyu; Choi, Hak Soo; Mallik, Shyam Kumar; Kim, Hak Sung; Sung, Haan Woo; Park, Hyun

2014-01-01

407

Chip-scale fluorescence microscope based on a silo-filter complementary metal-oxide semiconductor image sensor  

E-print Network

Chip-scale fluorescence microscope based on a silo-filter complementary metal-oxide semiconductor microscope. The extruded pixel design with metal walls between neighboring pixels guides fluores- cence-based epifluorescence microscopes have long been standard equipment in biological imaging de- spite their inherent

Yang, Changhuei

408

Community-Based Prevention Using Simple, Low-Cost, Evidence-Based Kernels and Behavior Vaccines  

ERIC Educational Resources Information Center

A paradox exists in community prevention of violence and drugs. Good research now exists on evidence-based programs, yet extensive expenditures on prevention have not produced community-level results. Various multiproblems are quite prevalent in the United States, such as violence, Attention Deficit Hyperactivity Disorder (ADHD), conduct problems,…

Embry, Dennis D.

2004-01-01

409

Compression-based distance (CBD): a simple, rapid, and accurate method for microbiota composition comparison  

PubMed Central

Background Perturbations in intestinal microbiota composition have been associated with a variety of gastrointestinal tract-related diseases. The alleviation of symptoms has been achieved using treatments that alter the gastrointestinal tract microbiota toward that of healthy individuals. Identifying differences in microbiota composition through the use of 16S rRNA gene hypervariable tag sequencing has profound health implications. Current computational methods for comparing microbial communities are usually based on multiple alignments and phylogenetic inference, making them time consuming and requiring exceptional expertise and computational resources. As sequencing data rapidly grows in size, simpler analysis methods are needed to meet the growing computational burdens of microbiota comparisons. Thus, we have developed a simple, rapid, and accurate method, independent of multiple alignments and phylogenetic inference, to support microbiota comparisons. Results We create a metric, called compression-based distance (CBD) for quantifying the degree of similarity between microbial communities. CBD uses the repetitive nature of hypervariable tag datasets and well-established compression algorithms to approximate the total information shared between two datasets. Three published microbiota datasets were used as test cases for CBD as an applicable tool. Our study revealed that CBD recaptured 100% of the statistically significant conclusions reported in the previous studies, while achieving a decrease in computational time required when compared to similar tools without expert user intervention. Conclusion CBD provides a simple, rapid, and accurate method for assessing distances between gastrointestinal tract microbiota 16S hypervariable tag datasets. PMID:23617892

2013-01-01

410

An aptamer-based dipstick assay for the rapid and simple detection of aflatoxin B1.  

PubMed

A rapid and simple dipstick assay based on an aptamer has been developed for the determination of aflatoxin B1 (AFB1). The dipstick assay format was based on a competitive reaction of the biotin-modified aptamer specific to AFB1 between target and cy5-modified DNA probes. Streptavidin and anti-cy5 antibody as capture reagents were immobilized at test and control lines on a membrane of the dipstick assay. After optimization, the limit of detection for the dipstick assay was 0.1?ng/ml AFB1 in buffer. The method was confirmed to be specific to AFB1, and the entire process of the assay can be completed within 30?min. Aqueous methanol (20%) provided a good extraction efficiency, and the matrix influence from corn extracts was successfully reduced through 2-fold dilution. The results of AFB1 analysis for corn samples spiked with known concentration of AFB1 by the dipstick assay and ELISA showed good agreement. The cut-off value of the dipstick assay for corn samples was 0.3?ng/g AFB1. Therefore, the dipstick assay is first reported and considered as a rapid, simple, on-site and inexpensive screening tool for AFB1 determination in grains as well as a corn. PMID:25032679

Shim, Won-Bo; Kim, Min Jin; Mun, Hyoyoung; Kim, Min-Gon

2014-12-15

411

Far-red fluorescence gene reporter tomography for determination of placement and viability of cell-based gene therapies  

PubMed Central

Non-invasive injectable cellular therapeutic strategies based on sustained delivery of physiological levels of BMP-2 for spinal fusion are emerging as promising alternatives, which could provide sufficient fusion without the associated surgical risks. However, these injectable therapies are dependent on bone formation occurring only at the specific target region. In this study, we developed and deployed fluorescence gene reporter tomography (FGRT) to provide information on in vivo cell localization and viability. This information is sought to confirm the ideal placement of the materials with respect to the area where early bone reaction is required, ultimately providing three dimensional data about the future fusion. However, because almost all conventional fluorescence gene reporters require visible excitation wavelengths, current in vivo imaging of fluorescent proteins is limited by high tissue absorption and confounding autofluorescence. We previously administered fibroblasts engineered to produce BMP-2, but is difficult to determine 3-D information of placement prior to bone formation. Herein we used the far-red fluorescence gene reporter, IFP1.4 to report the position and viability of fibroblasts and developed 3-D tomography to provide placement information. A custom small animal, far-red fluorescence tomography system integrated into a commercial CT scanner was used to assess IFP1.4 fluorescence and to demark 3-D placement of encapsulated fibroblasts with respect to the vertebrae and early bone formation as assessed from CT. The results from three experiments showed that the placement of the materials within the spine could be detected. This work shows that in vivo fluorescence gene reporter tomography of cell-based gene therapy is feasible and could help guide cell-based therapies in preclinical models. PMID:24104323

Lu, Yujie; Darne, Chinmay D.; Tan, I-Chih; Zhu, Banghe; Hall, Mary A.; Lazard, ZaWaunyka W.; Davis, Alan R.; Simpson, LaShan; Sevick-Muraca, Eva M.; Olmsted-Davis, Elizabeth A.

2013-01-01

412

Pencil-drawn paper supported electrodes as simple electrochemical detectors for paper-based fluidic devices.  

PubMed

A simple procedure for preparing inexpensive paper-based three-electrode electrochemical cells is described here. They consist of small circular pads of hydrophilic paper defined by hydrophobic barriers printed on paper with wax-based ink. The back face of these pads is insulated by thermally laminating a polyethylene layer and working, reference and counter electrodes are drawn on paper by using commercial pencil leads. At last, a controlled volume of sample containing a supporting electrolyte was laid to soak in paper channels. Their performance was evaluated by assaying these devices as both simple cells suitable for recording voltammograms on static samples and low-cost detectors for flowing systems. Voltammetric tests, conducted by using potassium hexacyanoferrate(II) as model prototype, were also exploited for identifying the brand and softness of graphite sticks enabling paper to be marked with lines displaying the best conductivity. By taking advantage of the satisfactory information thus gained, pencil drawn electrodes were tested as amperometric detectors for the separation of ascorbic acid and sunset yellow, which were chosen as prototype electroactive analytes because they are frequently present concomitantly in several food matrices, such as soft drinks and fruit juices. This separation was performed by planar thin layer chromatography conducted on microfluidic paper-based devices prepared by patterning on filter paper two longitudinal hydrophobic barriers, once again printed with wax-based ink. Factors affecting both separation and electrochemical detection were examined and optimised, with best performance achieved by using a 20 mM acetate running buffer (pH 4.5) and by applying a detection potential of 0.9 V. Under these optimum conditions, the target analytes could be separated and detected within 6 min. The recorded peaks were well separated and characterized by good repeatability and fairly good sensitivity, thus proving that this approach is indeed suitable for rapidly assembling inexpensive and reliable electrochemical detectors for flow analysis systems. PMID:23161669

Dossi, Nicolò; Toniolo, Rosanna; Pizzariello, Andrea; Impellizzieri, Flavia; Piccin, Evandro; Bontempelli, Gino

2013-07-01

413

A signal-on fluorescent assay for DNA methyltransferase activity using a methylation-resistant endonuclease.  

PubMed

A simple, rapid, and signal-on fluorescent assay was developed for activity analysis of DNA methyltransferase and for screening of its inhibitors based on a methylation-resistant endonuclease and SYBR Green I. PMID:24714961

Quach, Quang Huy; Chung, Bong Hyun

2014-06-01

414

A gold nanorods-based fluorescent biosensor for the detection of hepatitis B virus DNA based on fluorescence resonance energy transfer.  

PubMed

In this study, we designed a fluorescence resonance energy transfer system containing gold nanorods (AuNRs) and fluorescein (FAM) for the detection of hepatitis B virus DNA sequences. AuNRs were synthesized according to the seed-mediated surfactant-directed approach, and the surface of the AuNRs was wrapped with a thin layer of cetyltrimethylammonium bromide (CTAB), resulting in the AuNRs being positively charged. When FAM-tagged single-stranded DNA (FAM-ssDNA) was added into the AuNRs suspension, it was adsorbed onto the surface of the positively charged AuNRs and formed a FAM-ssDNA-CTAB-AuNRs ternary complex, the resulting structure led to a fluorescence resonance energy transfer (FRET) process from FAM to AuNRs and the fluorescence intensity of FAM was consequently quenched. When complementary target DNA was added to the FAM-ssDNA-CTAB-AuNRs complex solution, a further decrease in fluorescence intensity was observed because of an increased FRET efficiency. Under optimal conditions, the decline of the fluorescence intensity of FAM (?F) was linear with the concentration of the complementary DNA from 0.045 to 6.0 nmol L(-1) and the detection limit was as low as 15 pmol L(-1) (signal/noise ratio of 3). When this fluorescent DNA sensor was used to detect the polymerase chain reaction product of hepatitis B virus gene extracted from a positive real sample, a positive response was obtained. Impressively, the biosensor exhibits good selectivity, even for single-mismatched DNA detection. PMID:23172079

Lu, Xiaocui; Dong, Xiao; Zhang, Keying; Han, Xiaowei; Fang, Xian; Zhang, Yuzhong

2013-01-21

415

Relay recognition of Cu2+ and S2- in water by a simple 2-(2'-aminophenyl)benzimidazole derivatized fluorescent sensor through modulating ESIPT.  

PubMed

A new 2-(2'-aminophenyl)benzimidazole (2-APBI) derivatized fluorescent sensor (L) that behaves relay recognition of Cu(2+) and S(2-) in water solution (pH 7.4) has been developed. Sensor L displays excited-state intramolecular proton transfer (ESIPT) featured two emission bands and performs highly selective and sensitive recognition to Cu(2+) through two emissions simultaneous quenching. The on-site formed L-Cu(2+) complex exhibits excellent selectivity to S(2-) with fluorescence "off-on" response via Cu(2+) displacement approach, which exerts ESIPT recovery. Thus, through modulation the ESIPT state of sensor L, relay recognition of Cu(2+) and S(2-) in water has been achieved. PMID:24334067

Tang, Lijun; Dai, Xin; Cai, Mingjun; Zhao, Jia; Zhou, Pei; Huang, Zhenlong

2014-03-25

416

Development of a monolithic total internal reflection-based biochip utilizing a microprism array for fluorescence sensing  

Microsoft Academic Search

This paper proposes a monolithic integration method to fabricate a total-internal-reflection (TIR) based biosensor for fluorescence sensing. The monolithic TIR-based biosensor integrates a microfluidic chamber, polymer-based optics and planar waveguides into a high-throughput platform. The polymer-based optics, fabricated by SU-8 resist, include cylindrical microlenses and a microprism array for effectively conducting the excitation light into the planar waveguide. Two kinds

Shih-Hao Huang; Fan-Gang Tseng

2005-01-01

417

A sugar-aza-crown ether-based fluorescent sensor for Hg(2+) and Cu(2+).  

PubMed

A fluorescent sensor, 5, based upon the sugar-aza-crown ether structure with two anthracenetriazolymethyl groups was prepared and its fluoroionophoric properties toward transition metal ions were investigated. In methanol, the sensor exhibits highly selective recognition of Cu(2+) and Hg(2+) ions among a series of tested metal ions. The association constant for 5.Cu(2+) and 5.Hg(2+) in methanol was calculated to be 4.0 x 10(5)M(-1) and 1.1 x 10(5)M(-1), respectively. The detection limits for the sensing of Cu(2+) and Hg(2+) ions were 1.39 x 10(-6)M and 1.39 x 10(-5) M, respectively. PMID:19765693

Hsieh, Yu-Chi; Chir, Jiun-Ly; Wu, Hsiu-Han; Chang, Po-Sheng; Wu, An-Tai

2009-11-01

418

A triple helical calcium-based coordination polymer with strong blue fluorescent emission  

NASA Astrophysics Data System (ADS)

A hydrothermal reaction of 1,3-dicyanobenzene and Ca(OH) 2 yielded a triple helical calcium-based coordination polymer of the formula, C 20H 25Ca 2.50O 18.50 ( 1). The 1,3-benzenecarboxylate anion, found in the final product was generated in situ during the synthesis by the hydrolysis of 1,3-dicyanobenzene. X-ray diffraction study shows that the complex 1 crystallizes in the monoclinic system, C2/c space group, a=15.5701(5), b=21.4445(7), c=17.1601(6) Å, ?=111.7400(7)°, V=5322.1(3) Å 3, Z=8, Dc=1.651 Mg/m 3. The calcium atoms show differences in the coordination environments. Complex 1 emits strong blue fluorescent light ( ?em(max)=419 nm) when it is excited by UV light ( ?ex(max)=316 nm) in the solid state at room temperature.

Yu, Liang-Cai; Chen, Zhen-Feng; Liang, Hong; Zhou, Chun-Shan; Li, Yan

2005-08-01

419

A fluorescent aptasensor for potassium ion detection-based triple-helix molecular switch.  

PubMed

Here, a biosensor based on a quadruplex-forming aptamer for the determination of potassium ion (K(+)) is presented. The aptamer was used as a molecular recognition element; it was adjacent to two arm fragments and a dual-labeled oligonucleotide serving as a signal transduction probe (STP) that is complementary of the arm fragment sequence. In the presence of K(+), the aptamer was displaced from the STP, which was accompanied by decreased signal. The quenching percentage of fluorescence intensity was proportional to the concentration of K(+) in the range of 0.05 to 1.4mM. A detection limit of 0.014 mM was achieved. Furthermore, other metal ions, such as Na(+), Li(+), NH4(+), Mg(2+), and Ca(2+), caused no notable interference on the detection of K(+). PMID:25173515

Verdian-Doghaei, A; Housaindokht, M R; Abnous, Kh

2014-12-01

420

High-resolution mesoscopic fluorescence molecular tomography based on compressive sensing.  

PubMed

Mesoscopic fluorescence molecular tomography (MFMT) is new imaging modality aiming at 3-D imaging of molecular probes in a few millimeter thick biological samples with high-spatial resolution. In this paper, we develop a compressive sensing-based reconstruction method with l1 -norm regularization for MFMT with the goal of improving spatial resolution and stability of the optical inverse problem. Three-dimensional numerical simulations of anatomically accurate microvasculature and real data obtained from phantom experiments are employed to evaluate the merits of the proposed method. Experimental results show that the proposed method can achieve 80 ?m spatial resolution for a biological sample of 3 mm thickness and more accurate quantifications of concentrations and locations for the fluorophore distribution than those of the conventional methods. PMID:25137718

Yang, Fugang; Zhao, Lingling; Cong, Wenxiang; Wang, Ge; Intes, Xavier

2015-01-01

421

[Development of fluorescence imaging based assay for screening compounds with anti-migration activity].  

PubMed

In the present study, A fluorescent imaging-based high-throughput screening method was developed for identifying anti-migratory compounds with 96-well Transwell plates. The correlation, precision and stability of this method were examined and the incubation time of dye Hoechst 33342 in addition to migration time was optimized. In addition, The inhibitory activity of anti-cancer drug paclitaxel on tumor cell migration was assayed and an IC50 value of 0.717 micromol x L(-1) was obtained. Using this method, 24 components from Rhizoma Alismatis were screened and one component with anti-migration activity was found. These results show that the new proposed method with good precision, stability and linear range has the potential to assay the inhibitory activity of anticancer compounds. PMID:22010348

Nie, Xiao-Jing; Zhao, Xiao-Ping; Wang, Yi

2011-07-01